Makoto Asai (SLAC) Geant4 Users Workshop @ SLAC Feb. 18 th, 2002 Getting Started.
1961 - SLAC
57
M-280 LINEAR ELECTRON ACCEL;ERATOR STUDIES A.E. C. Contract AT(C4-3)-21 (Project Agreement No. 1) and PROPOSED TWO-MILE ACCELERATOR PROJECT A.E.C. Contract AT(C4-3)-363 Combined Status Report 1 July t o 30 September 1961 M.L. Report No. 859 M Report No. 28c October 1961 Project M and Stanford University Stanford, California W. W. Hansen Laboratories of Physics
Transcript of 1961 - SLAC
M-280
LINEAR ELECTRON ACCEL;ERATOR STUDIES
A.E. C. Contract AT(C4-3)-21 (Project Agreement No. 1)
and
PROPOSED TWO-MILE ACCELERATOR PROJECT
A.E.C. Contract AT(C4-3)-363
Combined Status Report 1 July t o 30 September 1961
M.L. Report No. 859 M Report No. 28c
October 1961
Project M and
Stanford University Stanford, California
W. W . Hansen Laboratories of Physics
Proprietory data of Stanford University and/or U. S. Atomic Energy
Recipient hereby agrees not t o publish the within informa- Commission.
t i on without specif ic permission of Stanford University,.
Nothing i n t h i s permission sha l l be construed as a warranty o r
representation by o r on behalf of Stanford University and/or the United
States Government t h a t exercise of the permission or r igh ts herein
granted w i l l not infringe patent, copyright, trademark or other r igh ts
of t h i r d par t ies nor shal l Stanford University and/or the Government
bear any l i a b i l i t y o r responsibi l i ty fo r any such infringement,
No l icenses o r other r igh t s under patents or w i t h respect t o
trademarks or trade names are herein granted by implication, estoppel
o r otherwise and no l icenses or other r igh ts respecting trade secrets ,
unpatented processes, ideas o r devices or t o use any copyrighted material are herein gmnted by implieation, estoppel o r otherwise
except t o the ext,ent revealed by the technical data and information,
the subject of the permission herein granted.
I . I1 . I11 .
N . V .
VI .
VI1 a
VI11 .
I X .
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . Mark I V program . . . . . . . . . . . . . . . . . . . . . . . Accelerator structure and high-power waveguide component
studies . . . . . . . . . . . . . . . . . . . . . . . . . . . A . Radiofrequency studies of the accelerator structure . . . B . Electroforming . . . . . . . . . . . . . . . . . . . . . . C . Brazing . . . . . . . . . . . . . . . . . . . . . . . . . D . Parts fabrication . . . . . . . . . . . . . . . . . . . . E. Water jacket . . . . . . . . . . . . . . . . . . . . . . . F . High-power waveguide components . . . . . . . . . . . . . Beamdynamics . . . . . . . . . . . . . . . . . . . . . . . . Injection system . . . . . . . . . . . . . . . . . . . . . . A . Mark IV conversion program . . . . . . . . . . . . . . . . Bo Bunch monitoring . . . . . . . . . . . . . . . . . . . . . C . Inf lect ion system . . . . . . . . . . . . . . . . . . . . D . Accelerator energy spectrum . . . . . . . . . . . . . . . Microwave c i r cu i t s . . . . . . . . . . . . . . . . . . . . . . A . General rf studies . . . . . . . . . . . . . . . . . . . . B . Drive system . . . . . . . . . . . . . . . . . . . . . . . C . Phase studies . . . . . . . . . . . . . . . . . . . . . . Klystron studies . . . . . . . . . . . . . . . . . . . . . . . A . Tube complement and performance . ., e . e . . . . B . Subcontracts . . . . . . . . . . . . . . . . . . . . . . . C . New f a c i l i t i e s . . . . . . . . . . . . . . . . . . . . . . Do L i f e t e s t s . . . . . . . . . . . . . . . . . . . . . . . . E . Experimental tubes . . . . . . . . . . . . . . . . . . . . F . Program for next quarter . . . . . . . . . . . . . . . . . High-power klystron windows . . . . . . . . . . . . . . . . . A . Window-life t e s t stand . . . . . . . . . . . . . . . . . . B . Recirculator window t e s t s . . . . . . . . . . . . . . . . C . Other window work . . . . . . . . . . . . . . . . . . . . Modulator studies . . . . . . . . . . . . . . . . . . . . . . A . Subcontract system development program . . . . . . . . . . B . Project development a c t i v i t i e s . . . . . . . . . . . . . .
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1
2
3 3 4 4 4 4 5 8
9 9 9
10
10
13 13 19 22
24 24 24 25 23 25 26 27 27 27 33 35 35 35
* ' I
X . Vacuum system . . . . . . . . . . . . . . . . . . . . . . . . . . . A . Mark IV conversion . . . . . . . . . . . . . . . . . . . . . . B . Feas ib i l i ty studies . . . . . . . . . . . . . . . . . . . . . . C . Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . D . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . .
X I . Support and alignment . . . . . . . . . . . . . . . . . . . . . . . A . Si t e ear th movement studies . . . . . . . . . . . . . . . . . . Bo Support . . . . . . . . . . . . . . . . . . . . . . . . . . . .
XI1 . Control system studies . . . . . . . . . . . . . . . . . . . . . . . A . General studies during the quarter . . . . . . . . . . . . . . . B . Magnetic systems for inject ion . . . . . . . . . . . . . . . . C . Reports published during the quarter . . . . . . . . . . . . .
XI11 . Research area design . . . . . . . . . . . . . . . . . . . . . . . A . Radiation shielding . . . . . . . . . . . . . . . . . . . . . . B . Accelerator heating . . . . . . . . . . . . . . . . . . . . . . C . Magnet calculations . . . . . . . . . . . . . . . . . . . . . . D . Photoproduction experiments . . . . . . . . . . . . . . . . . .
XIV . Site , buildings and u t i l i t i e s . . . . . . . . . . . . . . . . . . . XV . AC power system . . . . . . . . . . . . . . . . . . . . . . . . . .
A . Preliminary proposal f o r the s i te u t i l i t i e s . . . . . . . . . . B . Project power service connection . . . . . . . . . . . . . . . C . T e s t laboratory def in i t ive design . . . . . . . . . . . . . . .
XVI . Cooling-water system . . . . . . . . . . . . . . . . . . . . . . . A . Two-mile accelerator . . . . . . . . . . . . . . . . . . . . . B . M a r k N . . . . . . . . . . . . . . . . . . . . . . . . . . . . C . Research and development . . . . . . . . . . . . . . . . . . .
XVII . Heating and vent i la t ing . . . . . . . . . . . . . . . . . . . . . .
C . Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . .
E . Kinematics . . . . . . . . . . . . . . . . . . . . . . . . . .
37 37 37 37 37 38 38 38 38 39 39 40 48 51 51 51 52
52
52
53 54 54 54 55 56 56 56 56 57
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LIST OF FIGUriES
1.
2 .
3.
4.
5.
7.
8.
9. 10.
11.
12.
13. 14.
M a x i m u m def lect ion of each broad side of a waveguide vs inside pre s sure. ( A l l copper waveguides annealed i n
hydrogen a t gOO°C fo r 1 hour) . . . . . . . . . . . . . . . . . . 7 Qual i ty factor Q as a function of distance z along
constant-gradient section . . . . . . . . . . . . . . . . . . . . 14 Field strength squared (r/Q) observed along l a s t four
f ee t of constant-gradient section . . . . . . . . . . . . . . . . Comparison of rs/2 and 211/3 conical disk cavi t ies :
( a ) Bri l louin diagrams, (b) r/Q . . . . . . . . . . . . . . . . . w-p diagrams f o r the f’undamental m1 mode a t the 6$-ft point of a ten-foot accelerator section, and for the
TMll mode a t the input, the 6*-ft point, and output.
Note tha t the l i n e of v /c = 1 intersec ts a t three
different frequencies . . . . . . . . . . . . . . . . . . . . . . 20
Window-test assemblies . . . . . . . . . . . . . . . . . . . . . 29
Punctures on three half-wave windows a f t e r t e s t s
on resonant r ing . . . . . . . . . . . . . . . . . . . . . . . . 30
Breakdown i n half -wave window No. 111, magnification
approximately three times . . . . . . . . . . . . . . . . . . . . 32
Three ident ica l uniform-field magnets . . . . . . . . . . . . . . 41 Three nonidentical uniform-field magnets (isochronous system) . 43 Two bending and one quadrupole magnets . . . . . . . . . . . . . 44 Four bending and one quadrupole magnets (isochronous system) . 47 Three bending and two quadrupole magnets . . . . . . . . . . . . 49 Two bending and one off-center quadrupole magnets . . . . . . . . 50
15
18
P
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11.
11. ElARK IV PROGRAM
The Mark IV conversion program w a s continued during the past quarter
and i s now approximately 90% complete.
Essent ia l ly a l l the major components are i n place and have been
t e s t ed individually.
f o r a preliminary beam t e s t have been in s t a l l ed and f i n a l connections a re
being made.
generator source i n the console.
A l l of the control room console instruments necessary
Modulator-ignitron pulse t e s t s are under ww using the t r igger -
The vacuum system and cooling-water system are operational, subject t o
As pre- adjustments as other portions of the accelerator are activated.
viously reported, fur ther t e s t s and modifications of the rf driver were
found necessary and are s t i l l being carr ied out. A considerable amount
of system-interlock wiring remains t o be done and t h i s i s i n progress.
The next major s tep toward get t ing a beam i n the machine w i l l be t o
put rf in to the accelerator sections.
conduct t h i s t e s t i n October. Following th i s , the gun w i l l be in s t a l l ed
and the beam w i l l be turned on.
Preparations are being made t o
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111.
111. ACCELERATOR S T B U C W AND HIGIi-lQWR WAVEGUTIE L'OMFONENZ' STeTDIES
A. RADIOFBBQZTENCY STLTDIS OF TTE ACmBMNR STRUCTURE
During t h i s period we have continJed preparing f a c i l i t i e s and have
conducted the i n i t i a l tests needed for unciet%ak.lng the rf ppogrm of the
group.
t ion, requfred ear ly i n the program, t h a t underlies the l a t e r work, Areas
af current ac t iv i ty are the determinatlsr of" fabricatton, processing, and
handling procedures iasoyar a3 they affect rf performance; and the design
of matching, tuning, and inspection techniques requfred in zhe How-level
t e s t i n g of L O - f t sections, The fo-riuer ab jectives require htgh-pswer test- ing, whereas the 'Lattel- do riot.
A t present we are concern?d p r h a r i l y w i t h ga the~fng the Informa-
A s e r i e s of tes5s us ing short resor~anr lengths sf accelerator s t ructure
These tests and the equip- i s OUT i n i t l a l , e f for t i n the high-power program,
ment required were described i n an ea r i i e r S%a-Sus Fepsr5,L
equipment has been gahhered, modified and tes2eci under operating conditions
Briefly, the t e s t se5-up was as fsl Lokis A matched cavity consisting
The necessary
of 3 perfods of the uniform s f , m e i j u a w3,c dririeo with a VA-87 klystron at
a peak output power of l o 8 inegsi.watt,>a ='LIS resulted i n a s5andfng-field
s t rength within the cavlty correspondiug t~ a peak powe- -Eo excess of 20
megawatts f o r a t ravel ing wawe %rr si. marched s t ructxre , The pulse l-engt,h
of 2 psec p e d t t e d the peak C a V i t y fleaas Lo reach very near l r a steady-
s t a t e condition with a dwatloru 03 sotnevlzdt l e s s t n a n I usec. A se l f -
excited ~~3-60 ampLifier tsf7.h a TS-270 echo aux L n th? fezc-back Poop,
as used ear1ie-p i n the Nark -Fd d ~ i v r ~ , was f"c~u.rd :Q be auff iefent ly s tab le
for t h i s use,
An 2-3460 cw magnetron also w&s lwea ta ff?.?d the cavitg with 500 w a t t s .
This tu3e i s expected to cl?;Av?.r '(73 WdL"f,3 wkilc-t~ w i l l correspond t o an
average power d%ssfpa+fon of fhree-fourths of +,re m' ix -nm diss ipat ion ex-
pected i n a 10-f t section operating a t f u l l power. .[he tuning control
and s t a b i l i t y of the magnetron were suff ic ient ly good t o alLow the cavity
t o be eas i ly excited and traeked.
Tne enclosure f o r low-level. measliremente has been completed, and
suf f ic ien t equipment i s on hand to begln t h i s portion of the program.
room temperature control of 7'3 f 3/"-lF has 'been obtalned,
A
The r e l a t ive 0
'Status Report,, M Report No. 260, Project %I, Stanfor& University, Stanford, California, April 1 - 9 6 ~
Y 3 r>
humidity has varied about ? 3% and thus becomes the major contribution t o
changes i n the propagation constant of the accelerator s t ructure .
B. ELECTROFORMING
The small f a c i l i t y f o r electroforming 10-f t lengths has been completed
except f o r the f ix ture for holding the 10- f t length horizontally, as de-
scribed i n previous Status Reports.
i s now under construction.
This f ix tu re has been designed and
C. BRAZING
The furnace previously described, for brazing 10-f t lengths of accel-
The f irst t e s t s w i t h the furnace e ra to r section, i s v i r tua l ly completed.
a re expected t o be carr ied out i n l a t e October.
D. PARTS FABRICATION
The boring machine and associated equipment have now been ins ta l led ,
and the machine is about t o undergo acceptance t e s t s . A constant-temper-
a ture system f o r control l ing the cu t t ing o i l used on the machine has been
completed and holds the temperature within
i s controlled t o about ? l0C.
k 1/4OC. The room temperature
E. WATER JACKET
A study i s being made t o determine the optimum method of maintaining
the desired accelerator-tube temperature.
w i l l meet the temperature-control requirements for e i the r the constant-
gradient machine or the uniform-structure machine w i t h the same basic
cooling-jacket design.
date are reduced pressure boiling, cross flow,and p a r a l l e l flow with
variable flow ra t e .
A method i s being sought t h a t
Some of the more promising methods considered t o
A small-scale t e s t system f o r the reduced-pressure boi l ing method
of cooling has been designed and i s currently being assembled.
is expected t o begin i n October.
data t o determine the f e a s i b i l i t y of t h i s method of cooling the disk-
loaded waveguide.
Testing
The t e s t s w i l l provide the necessary
A small-scale t e s t has been planned t o determine the required number
of water j e t s for the cross-flow water-jacket design for the constant-
gradient section.
model of the accelerator section. The model is being made by put t ing
The t e s t w i l l be carr ied out w i t h a simplified copper
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111.
copper r ibs , simulating the copper disks, on one side of the plate . On the other side, the water chamber is formed by a second p la te t h a t has an exper-
imentally variable spacing.
ulated by s t r i p heaters attached t o the r i b side of the plate .
of t h i s experiment i s t o provide a uniform-heat input t o the under side of
a copper p la te and t o measure the temperature d is t r ibu t ion on the other
side of the copper when water i s flowing across the surface under varying
conditions.
possible t o make a t e s t set-up w i t h an actual short section of accelerator
t o check the r e su l t s of the data from the sample experiment.
The heat input t o the accelerator w i l l be sim- The objective
With the data from t h i s preliminary experiment it w i l l be
F. HIGH-POWER WAVEGUIDE COMPONENTS
1. Wavemide
A study i s being carr ied out t o es tab l i sh the specif icat ions fo r the
waveguide t o be used between the klystrons and the accelerator sections.
The two most l i k e l y cross sections are the standard S-band waveguide
(13 in . x 3 i n . ) and a waveguide having a cross section of 3.900 in.
X 1.950 in . Radiofrequency performance of the two waveguides may be
compared as follows
S-Band 3.900 in . x 1.950 i n .
Phase s h i f t i n degrees/OC change i n
Attenuation 6.24 X loe3 db/ft 3 X loB3 db/f't
temperature per 50 f t of length 1.25 1
Heat input per cm2 of waveguide-wall surface w i t h 20 kw i n the waveguides ,01 c a l .OO3 c a l
2. Waveguide-Wall Thickness
PreliminaSy calculations and a check t e s t have been carr ied out t o determine the deflection of a waveguide w a l l of OFHC copper, under vacuum,
as a function of thickness.
The calculations of the deflections were simplified t o elementary beam
theory by taking advantage of the double symmetry of the cross section. The
calculated deflections f o r an S-band waveguide w i t h 1/8-in. w a l l , which were
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I
car r ied out assuming the Copper t o be
as curve A i n Fig. 1.
within t h i s range, are plot ted
m e values used i n the p lo t a re
p = inches of mrcuw vacuum
A = maximum deflection o f each side of the waveguide i n . O O l in .
check the calculated Vafues, d@f'lOCtiOnS were measured as a fmc-
t i o n of pressure on a 2-ft long piece of annealed oopper S-band waveguide
with an 1/8-in. wall thickness.
measured deflection6 a t diff'erent pmssures fo r t h i s waveguide.
from curves A and B, there was good agreement bgtween the computed and the
experimental deflections i n the range where Hooke'e Law applies.
2 in . x 4 in. (nominal dimensiew) waveguide with, reagectively, 3/16 i n , ,
l /4 in . , 5/16 in . , and 3/8 In, W k l ekichesses, were a l l obtained from
curve B by the use of relationships established through the theory of
s t ruc tu ra l s i m l l i f u & *
B i n Fig. 1 was obtained by p lo t t i ng
A s seen
The curves C, I), and F, which represent the defIections of a
A s l igh t var ia t ion o f the pragsr%ienal X h i t from one fully-annealed
waveguide t o the other w i l l give great variations i n deflections i n the
nonelastic region, while more uniformity can be eQeeBed i f the s t resses
s tay w e l l below the e l a s t i c limf'b.
The 2 in. x 4 in . waveguide w i l l be tes ted for deflection as soon as it i s available, and creep t e s t s will be made when the f i n a l croBs section
i s established.
Deflections i n the rraveguide w a l l are of bportance because the phase
sh i f t per un i t length i s determined by the waveguide cross-sectional
dimensions.
guide feed t o the next has been se t at 2'. Hence, the waveguide w a l l must be mechanically s table and temperakure controlled t o insure tha t
any change tha t may occur w i l l f a l l within allowable l i m i t s .
cation f o r these l i m i t s i s now being formulated.
The t o t a l allowable var ia t ion i n phase s h i f t from one wave-
The specif i -
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111.
4D
t I
o\ - 0
0
-3 0
r- - 0
0
n \ D [ o 0 0
-0 ,-c - 0 c
rl W
8
* %
In -d -0 v: 0
cd e, %i
4 - 0
o c * o .d 4 0 e, r-l k
ma, -0 a
0
-- 0
-nJ 0 0
rl -0
0 .
a, r l k
2 2 8 W
N.
IV. BEAM DYNAMICS
A section on beam dynamics of the Project M accelerator was wri t ten
f o r a paper given at the Brookhaven Conference on High-Energy Accelerators.
The question of beam-steering by a strong-focusing quadrupole system
has been re-examined.
focusing system could guide the beam through somewhat la rger misalignment
than was thought previously. For example, i n the case of systematic m i s -
alignment (constant curvature of the accelerator axis) it appears t h a t
misalignments of the order of 10-15 cm could be handled.
2-3 cm was quoted previously.)
The present ten ta t ive conclusion i s t h a t the strong-
( A f igure of
The quadrupoles i n the above example would have t o have a strength
of
length) . The l imi ta t ion on maximum quadrupole s t rength (and maximum t o l -
erable misalignment) still appears t o be imposed by chromatic aberration.
- 5000 gauss (e.g. , a gradient of 500 gauss/inch and a 10-inch
2K.L. Brown, A.L. Eldredge, R.H. H e l m , J . H . Jasberg, J . V . Lebacqz, G.A. Loew, R.F. Mozley, R.B. Neal, WOK. H. PanofsQ, T.F. Turner, "Linear Electron Accelerator Progress a t Stanford University," M Report No. 275, Project M, Stanford University, Stanford, California, September 1961.
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v.
V. I N J E C T I O N SYSTEM
A. MARK IV CONVERSION PROGRAM
The Mark IV gun modulator has been tes ted w i t h a r e s i s t i ve load.
The pulse-forming networks have been adjusted, Some s l igh t readjustment
of the pulse l i n e s w i l l be required a f t e r the gun i s ins ta l led . The modulator was t e s t ed at repe t i t ion r a t e s f r o m 60 pps t o 360 pps
i n multiples of 60 pps.
essary t o reduce the grid-pulse voltage below the nominal operating
voltage t o avoid exceeding the ra t ing of the grid-modulator power t rans-
former.
been ordered.
A t repe t i t ion r a t e s above 120 pps it was nec-
A replacement transformer adequate fo r 360 pps operation has
B. BUNCH MONITORING During the past quarter the problem of providing a d i r ec t monitor
of the in jec tor bunching was studied. Although the electron-energy
spectrum can provide a measure of the bunch size, the spectrum width
measured depends a l so on the phase of the bunch, on the var ia t ion of any of the primary machine parameters i n the in te rva l during which the spec-
t rum i s measured, and on the veloci ty modulation introduced by the buncher.
For turning on and tuning the In jec tor it would be desirable t o have a
monitor t h a t i s sensi t ive t o the bunch s ize , but re la t ive ly insensi t ive
t o phase and beam energy. Any device t h a t is sensi t ive t o the harmonic
current i n the accelerator might f i l l this need, The most obvious ap-
proach i s t o l e t the beam pass through the rf s t ructure so t h a t a par t ic -
u l a r harmonic of the accelerator rf w i l l be generated. I f we consider
the accelerator bunch t o be rectangular with a phase in t e rva l of
the rf current at the n ' t h harmonic i s
8 ,
where Io i s the dc current. Squaring and d i f fe ren t ia t ing with respect
t o the bunch s ize 8 , we obtain
e 2 2
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'n
For good sens i t i v i ty we would l i k e t o have the f rac t iona l change of the
harmonic power be of the same order as the f rac t iona l change i n bunch s ize .
Thus
which i s s a t i s f i e d f o r
If the in jec tor produces a 5' bunch, we should monitor about the 30th
harmonic whose wavelength i s 3.5 mm. be used t o ex t rac t power i n t h i s wavelength range from a r e l a t i v i s t i c
beam.
The magnetic undulator3 can readi ly
With an undulator 1 meter long, an aperture of 1 cm, magnetic f i e l d s
of about 500 gauss, and 50 milliamperes beam current, it should be possible
t o generate 100 m i l l i w a t t s of the 30th harmonic. The magnetic f i e l d s can
be turned off when the in jec tor i s not being tuned t o avoid deter iorat ion
of the beam opt ics ,
C. INFJXCTION SYSTEM
The f e a s i b i l i t y study of inject ing in to the accelerator at an angle
i s being continued,
f o r which the path length through the system i s independent of momentum
t o first order i n Ap/p. With such isochronous systems it appears fea-
s ib l e t o in j ec t a t 90' from the accelerator axis .
possible t o locate the electron guns i n o r adjacent t o the klystron
housing f o r ease i n maintenance.
It i s possible t o design an achromatic def lect ion
This w i l l make it
Do ACCELEFWPOR ENERGY SPECTRUM
The electrons that enter the first section of accelerator may be
divided in to four groups:
and hence w i l l be within the desired energy spectrum;
t h a t may be expected t o t r a v e l a considerable distance along the accel-
e r a to r with an asymptotic phase outside but near the 5' bunch; (3 ) elec-
t rons with an asymptotic phase so f a r from the bunch (and the wave c r e s t )
(1) electrons t h a t w i l l form the 5' bunch
(2) electrons
'He Motz, "Applications of the Radiation from Fast Electron Beams," J- A P P ~ ~ ptu.~. 22, 527-535 (1951).
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tha t they may be expected t o get lost before a t ta in ing high energy;
(4) e lectrons tha t are not bound t o the wave at al l .
desirable t o maximize the number of electrons i n group (1).
important t o minimize the number i n group ( 2 ) , since these electrons
contribute t o the radiat ion along the accelerator and at the end s ta t ion .
The number of e lectrons i n groups (3) and (4) is probably of l e s s impor-
tance, but it is cer ta in ly desirable t o keep t h e i r number s m a l l s ince they
contribute t o beam loading and probably t o gassing i n the first sect ion
of the accelerator .
the populations of these groups for the following two buncher configurations:
(1) a single-cavity buncher followed by a uniform accelerator sect ion w i t h
B, = 1, a = 3.63; (2) a uniform waveguide buncher with by an accelerator section w i t h Dw = 1, CY = 3.63. The parameters of the
bunchers were chosen t o maximize the current within a 5' bunch, assuming
a 14 gun-voltage r ipple .
Table I.
i n t r i n s i c spectrum (5' bunch), 10% spectrum, and 100% spectrum ( a l l bound
electrons whose ve loc i t ies are never negative) are l i s t e d f o r the two types
of bunchers.
be expected t o travel a considerable distance along the accelerator.
minimum veloci ty a t ta ined by any electrons i n the 104 spectrum is two- th i rds the in jec t ion velocity, so t h e i r probabi l i ty of a t t a in ing high
energy before ge t t ing l o s t is considered excel lent .
It is, of course,
It i s a l so
A preliminary calculat ion w a s performed t o estimate
pW = 0.5 followed
The r e s u l t s of the calculat ion a re given i n The f rac t ion of injected electrons contained within a 0.14
It i s assumed t h a t the electrons within a lo$ spectrum m u s t The
v.
H
Y
O C O C O O d c u 1
r i r i r i
2 -
V I . MICROWAE3 CIRCUITS
Because of a recent reorganization, the work separately reported on rf studies, drive systems and phasing s tudies w i l l now be consolidated under
t h i s section.
A. GENERALRFSTUDIES
1. Measurement of Qual i ty Factor Q as a Function of z i n the
Constant-Gradient Acceleratqr StmctLire
Figure 2 shows a graph of Q as a function of z, where z i s taken
i n the longitudinal d i rec t ion of the present constant-gradient s t ruc ture
design. It i s seen t h a t Q var ies by about 7% over the t o t a l length of
a section.
careful ly electropolishing the t e s t cav i t ies and by taking in to account the
coupling coeff ic ients of the pick-up loops, The decrease i n Q w i l l some-
what compensate f o r the increase of r/Q vs z reported e a r l i e r , thereby
tending t o reduce the increase of the e l e c t r i c a l f i e l d over the section t o
about 5$,, a t zero beam loading,
A considerable improvement, was obtained fn the measurements by
2. Constant-Gradient Coupler Design
An output coupler f o r the constant-gradient s t ructure w a s t e s t ed w i t h an
electroformed two-foot sec t ion corresponding t o the l a s t nine cav i t i e s
of the constant-gradient section,
following parameters :
.The match appears sa t i s fac tory f o r the
2a = 0.7640 inches
2b = 3.1790 inches
iris aperture = 0.870 inches
The input coupler i s ready and will be t e s t ed as soon as the two-foot
input sample is available .,
3- Constant-Gradient F ie ld Skudies
In order t o attempt a d i r ec t measurement of the f i e l d var ia t ion i n a
constant-gradient section, a four-foot constant-gradient sample w a s assembled
out of available t e s t cav i t ies .
ing the phase-shift var ia t ion created by a d i e l ec t r i c bead introduced in to
the section and displaced longitudinally along i ts axis. A graph of these
r e s u l t s i s shown i n Fig. 3. It i s in te res t ing t o notice that, although the
The f i e l d var ia t ion w a s obtained by measur-
- 13 -
1
VI.
Q
14200
14000
13800
13600
13400
13200
13000
Q vs z
FIG. 2--Quality fac tor Q as a f’unction of distance z along
constant - gradient sect ion.
- 14 -
VI "
0
- 15 -
T
VI.
phase s h i f t (and, therefore,
every time the d i e l ec t r i c bead passes by a disk, the average increase i n
f i e l d can be measured qui te accurately.
an average increase of 7$ per meter i n
This v e r i f i e s quite accurately r e su l t s reported e a r l i e r on experiments done
on individual cav i t ies .
E2) undergoes osc i l la t ions as a function of z
Preliminary r e su l t s indicate t h a t
r/Q occurs i n t h i s four-foot sample.
4. Conical-Disk Structure
Figure 4 shows a comparison of group velocity v and r / Q measure- g
ments done on rr/2 and 25r/3 conical-disk t e s t cav i t ies . The cavi t ies used
for the 5[/2 case were the same as reported i n M.L. Report No. 416,4 where
a Is$ improvement w a s reported over the standard Stanford rr/2 f la t -d isk
case. It appears now tha t t h i s ear ly r e s u l t was i n e r ro r and t h a t the
conical-disk s t ructure actual ly gives a lower r/Q than the f la t -d isk
structure, fo r both the rr/2 and the 2rr/3 cases. Although physical reason-
ing had previously indicated t h a t tapering the disk surface would increase
the
group velocity, one i s forced t o increase both 2a and 2b, thereby actual ly
decreasing r/Q.
r/Q, it now i s seen tha t i n order t o maintain the same frequency and
The next s tep i s obviously t o perform an experiment where the disk
is tapered i n the opposite direct ion (thinner a t the wall, th icker at the
hole) t o check whether an improvement i n can thereby be obtained or whether the f la t disk i s actual ly the opthum case.
r/Q
5 . Measurements of Space-Harmonic Amplitude
A new se r i e s of measurements has been performed t o obtain the var ia-
t ions of the space-harmonic amplitude a as a function of disk thickness
and group velocity. In some cases the disk edge was square, i n others it
was beveled. Results obtained so far are shown i n the tab le below.
0
4Status Report (PA-1 and -2), M.L. Report No. 416, W. W. Hansen Laboratories of Physics, Stanford University, Stanford, California, April 1957.
- 16 -
VI.
THREE DISKS PER WAVELLFNGTH (d = 1.378 i n . , 2n/3 mode)
Disk Thickness vg/c a2/Xa2 o n Disk Edge
,060 i n .
120 in .
,230 i n . ,230 i n .
,230 i n .
-230 in .
.23O i n .
,230 i n . ,230 in .
so153 .o i l5 a0057 .0068
,0115 9 0139 .or78 .0200
.0215
,850 837
-757 .816 .829
.839
.a53
.860
.862
square
square
square
beveled
beveled
beveled
beveled
beveled
beveled
FOUR DISKS PER WAVELZNGTH (d = 1.034 in . , n/2 mode, 2b = 3.214 i n . )
a2/Ca2 Disk Edge vg/c o n Disk Thickness
.23O i n . .0072 .920 square
A few addi t ional cases a re now being measured, and a complete graph
w i l l be published i n the next Status Report.
measurements made a t Stanford did not take in to account more than three
terms i n the Fourier expansion of the f i e l d and, therefore, gave r e s u l t s
somewhat higher than warranteda5 It can now be sa id t h a t from the shunt
impedance point of view, khere w i l l be a de f in i t e advantage i n going
t o a disk thinner than 0.230 i n . Mehanical and thermal properties may,
however, outweigh the r e l a t ive advantage of thinner disks.
It appears t h a t previous
6. Prebuncher Studies
A prebuncher design for the Mark rV accelerator has been completed,
By using s t a in l e s s s t e e l and shaping the and a model has been tes ted .
coupling loop f o r c r i t i c a l coupling, a
2836 Mc have been obtained.
i s hoped t h a t with t h i s new 1ow-Q design, no tuning w i l l be required during
accelerator operation.
of 530 and a QL of 265 a t
The f i n a l unit is now being welded, and it QO
5Renke Hirel, "Space Harmonics Content of the 2n/3 Accelerator Struc- ture," M Report No. 270, Project M, Stanford University, Stanford, California, June 1961. - 17 -
I
2880 ,- VI 0
f (Mc/sec )
2860
2840
2820
r /Q (ohms/cm)
60
40 f l a t disk
group velocity as
------I I I I I I
20 2s/3 J[
(b 1 ~113 fl/2 2 d 3
t i n . .120 .120
d in . 1.0335 1.378 2b i n . 3.825 3.750
a degrees 11.16 15-72 h i n . .148 .250
vg/c .0103 .0180
f Mc /set 2857.3 2855.8
2a i n . .920 1.060 d
r/Q ohms/cm 37.0 35.0
bandwidth Mc /sec 39.1 56.9
FIG. 4--Comparison of s/2 and 2s/3 conical disk cavi t ies : ( a ) Br i l lou in diagrams,
- 18 -
V I .
7. Group-Velocity Measurements
Report No. 5103, P . N . Robson, Metrcpolitan-Vickers Elec t r ica l Co., L t d . ,
indicates tha t it i s possible t o Fourier analyze a Brillouin diagram and t o get a more accurate measurement of group velocity than i s generally ob-
tained from the graphical d i f fe ren t ia t ion method ( i .e . , taking the slope
of the curve at the used frequency).
s i x cavities, the graphical r e su l t approaches the Fourier Series r e su l t by
about 5$*
The table below shows that by using
Cavi t i e s Fourier Series Graphic a1 Met hod
3 Vg/ c 0170
6 0119 . o n 3
8 , TMll Mode Studies
Continuing the studies carr ied out at Stanford t o examine the higher
passbands present i n the accelerator s t ructure and t h e i r possible connec-
t i on w i t h the beam-breakup phenomenon observed a t high currents, Bri l louin
diagrams were obtained f o r various cavi t ies of the constant-gradient struc-
tu re , Figure 5 shows the results fo r three d i f fe ren t cavi t ies . It is seen
tha t the values of
intercept wi th the
foot constant-gradient length,
f o r beam breakup, where the beam induces energy t o flow i n the TMll mode
and i s then deflected by it, varying the cross-sectional dimensions of
the accelerator s t ructure w i l l prevent the osc i l la t ion from get t ing
s ta r ted a t t h e currents usually quoted (about 300 milliamperes f o r a
2-microsecond pulse). The Q a t the lc mode i s of the order of 13,000.
which are approximately the frequencies at the f l c p
v = e l ine , vary by more than 200 Mc over a ten- P
With the mechanism presently suggested
B. DRIVE SYSTEM 1. Design Studies
The whole drive system i s presently undergoing re-examination and
it i s possible t h a t considerable departures from the or ig ina l design
w i l l be made i n the next few months.
boosters altogether and replacing the coaxial drive l i n e by a large
The idea of eliminating the main
- 19 -
T
VI. 4600
4400
4200
4000
3 800
3600
3400
320C
300C
280C
z = IO FT.
z = 6i FT. I I I I /I I w IL Q 27r 5 F w 6 3 2 - 6 3 0
FIG. 5--cu-B diagrams for the fundamental TM mode at the 6$--ft point of a ten-foot
accelerator section, and f o r the TM mode at the input, the 62-ft point,
and output. Note tha t the l i n e of v /c = 1 intersec ts a t three different P
frequencies.
01
11
- 20 -
I
VI.
cross-section rectangular waveguide i s being examined.
2 Radiofrequency Driver
Tests on the rf dr iver f o r the Mark IV accelerator have continued
throughout t h i s quarter.
f icat ions under a subcontract,
the uni t s t i l l suffers from several weaknesses.
being made t o remedy the following problems:
i n the first three microseconds of the pulse;
over the 4 Me tuning range; (3) elimination, or at l e a s t reduction, of rf
power appearing i n sidebands and spurious frequencies.
This uni t has been developed t o Stanford speci-
Several improvements have been made, but
An attempt is presently
(1) osc i l la t ions and droop
(2 ) output power in s t ab i l i t y
3. Specifications are being draf ted for a t o t a l of 16 rf dr ivers t o pro-
Radiofrequency Drivers f o r Test-Staqd Ins ta l la t ions
vide rf energy t o a t o t a l of 16 test stands.
used t o perform feas ib i l i t y , performance and l i f e - t e s t studies of components
for Project M.
These t e s t stands are t o be
4. With the exception of the rf driver, the rf drive and phase system
Drive-System Contributions t o the Mark I V Conversion Program
for the Mark IV has been substantially completed,
components--ovens, power supplies, switching c i rcu i t , etc.--have been in-
s t a l l ed together w i t h the necessary control wiring.
console has been completed, with the exception of the rf-driver control.
Preliminary t e s t ing of the rf system, however, can be conducted with a
temporary control uni t presently available.
components have been instal led, and only a l imited number of rf cables
remain t o be Laid, A complete subsystem tes t i s contemplated immediately
following acceptance of the rf driver.
The associated electronic
Equipment f o r the
A l l the required microwave
3 . Sub-Boosters
The TH-2101 klystrons on loan from the CFTH Company of France have
been tes ted using available modulators. Their performance shows a s m a l l
modulation on the beam, caused by the magnetic f i e l d of the filament.
When the filaments are ac supplied, t h i s modulation appears i n the output
causing the rf output power and phase t o vary.
360 pps, several output Levels are observed. of t h i s d i f f i cu l ty and w i l l try t o remedy it.
A t a repe t i t ion r a t e of
The manufacturer i s conscious
- 21 -
I
VI.
T e s t s on these tubes w i l l continue throughout the next quarter.
6. Coaxial Couplers
Two coaxial couplers have been received from Narda (Model 2413, 10 and 6 db, respectively). These d i rec t iona l couplers are t o be used with
an Andrew-type r i g i d coaxial l i n e , Their performance has been checked,
and it appears t h a t the respective coupling fac tors a re 10.6 and 5.7 db, w i t h d i r e c t i v i t i e s of 33 and 25 db, respectively.
t e r i s t i c s of these couplers were measured across the main arms, a s well as
across the input coupling arms, and turned out t o be negligibly small over
the 2856 f .1 Mc range (less than 0.02' i n a l l cases).
The dispersion charac-
C. PHASE STUDIES
1. Mark I11 Phasing Experiments
A preliminary phasing experiment using the beam-induction technique6
w a s carr ied out on the Mark 111 accelerator.
enable the phasing of four sections t o be undertaken. It is d i f f i c u l t t o
d r a w f i n a l quant i ta t ive conclusions from t h i s experiment, since the ex- pected increase i n beam energy and improvement i n spectrum width resu l t ing
from one correctly-phased section was l e s s than the accuracy with which
these two parameters could be measured w i t h equipment available on Mark 111.
It can be stated, however, t h a t using the beam-induction technique it was
possible t o phase the four sections t o about the same degree of accuracy
as with the present technique based on beam-energy maximization.
Equipment was in s t a l l ed t o
A detector uni t , previously described, w a s used f o r comparing the
r e l a t ive phases of the two given signals. Preliminary d i f f i c u l t i e s en-
countered i n using t h i s phase detector were overcome, but completely sa t -
i s fac tory operation w a s not obtained.
the detector so as t o use it f o r pulsed, cw, or a combination of these
inputs. More detai led experiments are t o be scheduled when the improved
phase-detector un i t is available
Attempts are being made t o adapt
2. Beam-Energy Maximization Technique
In view of the large equipment costs involved i n any method using the
electron-beam phase as a reference (react ive beam loading as well as beam-
induction methods), the beam-energy maximization technique i s presently
%scribed i n Status Report, M Report No. 260, Project M, Stanford University, Stanford, California, April 1961.
VI.
being re-examined. accelerator i n such a way as t o simulate the influence of one klystron on the beam-output energy of an accelerator that uses 240 klystrons.
We are examining the problem of how t o use the Mark I V
3. Phasing of a Nonsynchronous Section by the Beam-Induction Technique
A study of the beam-induction method applied t o a nonsynchronous
section, i . e . , a section not operating exactly at the velocity of l igh t ,
has been completed and shows that under these conditions the beam-induction
method produces a phase ident ica l t o the reactive beam-loading technique.
It can thus be concluded tha t the beam-induction method i s equally satis-
factory from t h i s point of view.
short ly . A separate report w i l l be published
- 23 -
I
V I I .
V I I . KLYSTRON STUDIES
During the last quarter the Klystron Group completed the move in to
Because of t h i s move the i t s new f a c i l i t i e s i n the Project M building.
construction of new klystrons has been slowed down.
oxide ceramic windows were constructed and are ready f o r use on the next
tubes.
Several beryllium
We a lso have begun l i f e t e s t ing of exis t ing Stanford klystrons.
A. TUBE COMPLEMENT AND PERFORMANCE
The stockpile of tubes on hand has been decreased by two tubes t h a t
a re now ins t a l l ed i n Mark I V accelerator sockets and by two tubes that
f a i l e d a f t e r approximately 100 and 50 hours, respectively, of l i f e tes t ing .
During the quarter the first "short" tube w a s b u i l t and tes ted .
was t o be operated on a permanent magnet t h a t was received i n June.
i n i t i a l tube t e s t s were performed on an electromagnet and the tube per-
formance was adequate, although the eff ic iency was somewhat lower than
expected. Unfortunately, during the removal of the tube from the electro-
magnet, a mishap i n the handling equipment ruined the cathode sea l and l e t
the tube down t o a i r .
t e s t ing .
This tube
The
The tube has now been repaired and i s ready f o r
B. SUBCONTRACTS
A t the present time both subcontractors (Sperry Gyroscope Company,
Great Neck, Long Island, N. Y., and RCA, Lancaster, Pa.) a re somewhat
behind schedule, but the expected delivery date of s i x sample tubes has
not been materially affected.
Sperry is t e s t i n g i t s second klystron, which was b u i l t t o accommodate
reversal f i e l d focusing.
tubes, which should be delivered t o Stanford between now and January.
The permanent magnets f o r these tubes are manufactured by G.E. and were
l a t e i n delivery.
They also have subassemblies f o r three short
RCA has resolved the low perveance problem experienced on their first
tube.
average beam power, f o r several weeks. Their beam t e s t e r should be under-
going t e s t s by October 1st and they expect t o have t h e i r f i rs t deliverable
tube b u i l t by October 15th.
They have had a diode running a t approximately 50 Mw peak, 50 kw
- 24 -
VII.
C. NEW FACILITIES
The move t o the new Project M building on campus has been completed.
1. Shop
Except f o r the lack of gasses and chemical cleaning f a c i l i t i e s , the
tube shop i s now i n operation.
2. Test Area
We now have two modulators i n operation, the Ling 100 Mw uni t t h a t has
been used pr incipal ly fo r l i f e t e s t ing and the spark gap modulator t h a t
i s being used f o r t e s t s of special tubes (such as the short tubes). We
are a lso adding bakeout f a c i l i t i e s t h a t should be completed by the end
of next quarter.
3. Test Equipment
I n i t i a l t e s t s on all-metal high-power loads have not been completely
sa t i s fac tory as yet , and we are s t i l l using glass, water-fi l led loads i n
sp i t e of the inherent dangers of loss of vacuum through glass f a i lu re .
4
D. LIFE TESTS
We are presently undertaking a one-socket l i f e - t e s t program t o deter-
mine what problems besides the windows might determine end of l i f e of our tubes.
vacuum loads, even though the windows had been punctured much e a r l i e r .
The end of l i f e came from fa i lu re of the loads t h a t resul ted i n the l o s s
of vacuum i n the tube through the punctured window.
through a cathode-bushing puncture tha t was induced by gassing i n the tube
resu l t ing from the loss of vacuum i n the load through a punctured window.
From our experience t o date it appears t h a t the windows can be blamed fo r
the end of l i f e of these tubes.
The f i rs t tube tes ted operated f o r approximately 100 hours on
The second tube f a i l e d
E. EXPERIMENTAL TUBES
A s mentioned e a r l i e r , the first short tube has been t e s t ed on an
electromagnet w i t h adequate but not outstanding r e su l t s . The gain was as
high a s the gain of a long tube, but the eff ic iency w a s somewhat lower.
Another short tube w i l l be ready f o r addi t ional t e s t s within the next month.
A complete redesign of the output system i s being undertaken t o accom-
modate the out l ine drawing of the production Project M klystrons.
- 25 -
V I 1 .
F. PROGRAM FOR NEXT QUARTER During the next quarter we expect t o have a t h i r d high-power modulator
available t h a t w i l l permit us t o continue l i f e t e s t ing a t high-average power,
t o repair standard tubes, and t o investigate fur ther the short tubes and
t h e i r modifications.
- 26 -
V I I I .
VIII. HIGH-POWER KLYSTRON W I N D O W S
A. WINDOW-LIFE TEST STAND During the l a s t quarter the window-life t e s t stand was moved t o the
new building where it i s being used w i t h the new Ling modulator. A Litton
type-L 3302 klystron tha t operates up t o 10 Mw i s on th i s equipment.
though the high-power section of the modulator has operated very sa t i s fac-
t o r i l y , considerable d i f f i cu l ty has been encountered w i t h the low-level
t r i gge r generators. We are temporarily using a jury-rigged, Locally b u i l t
un i t t o overcome t h i s d i f f i cu l ty .
un i t t h a t should be available shortly. In sp i t e of delays caused by t h i s
and by a shorted tube socket, we have operated about 160 hours on a one-
sh i f t bas i s , During t h i s time one section became very gassy. The suspected
window was removed and found t o be peppered w i t h punctures, none of which
went through the disk tha t was s t i l l vacuum t i g h t .
w i t h a t o t a l of s i x windows.
Al-
The Ling Company is building a new trigger
Operation has continued
The success of the present vacuum system, which has a separate power
supply f o r each Vacion pump, encouraged us t o order supplies f o r the next
s i x windows.
We w i l l add addi t ional s h i f t s as soon as we can obtain the necessary per-
sonnel.
These w i l l be added as soon a s the supplies are available.
B. RECJRCULATOR WINDOW TESTS
Shorting plungers of a new design have been in s t a l l ed i n the phase
s h i f t e r on the recirculator .
t ha t occasionally occurred on the old pair .
have occurred a t full power.
It is hoped tha t t h i s w i l l avoid the arcing
In a few weeks use, no troubles
A se r ies of t e s t s has been run on 1/16-inch disks of Wesgo MI 995 and
Coors AD 96 i n the s t ructure described i n the last Status Report.7
these disks were run t o powers i n excess of 30 Mw, no damage has occurred.
A t o t a l of seven disks were tes ted, some of them several times.
made a t a reduced vacuum t h a t caused some arcing but did no damage.
application of power was t r i e d t o simulate the former Mark I11 operation
(see below) without any ef fec t . Although these r e su l t s are disappointing,
we w i l l continue these tests as time permits.
Although
Tests were
Sudden
7Status Report, M Report No. 272, Project M, Stanford University, Stanford, California, July 1961, p. 17.
- 27 - t ' 1
V I I I .
A new RCA window with a vacuum seal made by shrinking was tes ted at the highest available power.
The window w a s rotated t o place the chip at a voltage minimum.
power on t h i s window w a s 28 Mw at 60 pps.
which accounts f o r the s l i gh t ly lower than usual power. Tests were run t o leve ls as high as 21 kw average power.
During i t s first run it was s l igh t ly chipped.
The peak
The window ran s l igh t ly warm,
A window structure, similar t o the J-type but having the l e s s abrupt
t rans i t ions from circular-to-rectangular guide used on the Project M klys-
trons, was t e s t ed t o 20 Mw. the tests, operation was normal. Mark I11 accelerator.
Except fo r an e r r a t i c br ight glow ear ly i n
This window i s now i n operation on the
Two windows with a conductive coating applied by Eimac were tes ted
Operation was normal except fo r a glow tha t was br ight green t o 20 Mw.
instead of the usual blue. These windows were intended fo r fur ther tes t -
ing on the Mark I11 accelerator, but both were found t o leak a t the metal-
to-ceramic sea l after the tests on the recirculator .
The low-gradient window described i n the last Status Report' was
tes ted twice t h i s quarter using d i f fe ren t disks.
assemblies ran very warm although they successfully passed more than
20 Mw.
[See Fig. 6 ( a ) ] Both
The cause of t h i s abnormal heating has not been determined.
A half-wave slab window, shown, i n Fig. 6(b), has been designed and
three models have been tes ted i n the recirculator . The s l igh t taper
between the section holding the disk and the rectangular-to-circular taper
enabled us t o use available 3-inch tapers. The nearest measured ghost
mode was approximately 30 Mc from the match frequency.
Mc lower than our calculated value and i s probably due t o the e f fec t of
the taper.
surface as shown i n Fig. 7. The windows shown i n Fig. 7, Nos. I and 111,
punctured on the load side. Figure 7, No. 11, punctured on the tube side,
but w a s reversed so t h a t w e could observe the puncturing. Arcing occurred
between the pa i r s of puncture marks, similar t o t h a t observed on a J win-
d ~ w . ~
This i s about 17
Three successive models of t h i s window were punctured on one
There w a s no arcing t o the metal w a l l s at any time. In each case
'Status Report, op. c i t . , p. 16.
- 28 -
VI11 *
/ /
/
/
/
/
/
/
/
/
/
/
(a) low-gradient window assembly
taper 3" circular- to -rectangular waveguide
.707" x 2.875" dim disk
(b) half-wave window assembly
FIG. 6--Window-test assemblies.
- 29 -
T
V I I I .
H H H
- 30 -
V I I I .
f a i lu re s ta r ted within a f e w hours operation as soon as the power had reached about 20 Mw. It w a s possible t o observe the window through a t e l e -
scope and, apparently, t o see the formation of holes.
Figure 8 shows photographs taken through a telescope, of three events
on the Fig.7( 111) disk a f t e r considerable damage had occurred. The area covered i s about an inch i n diameter i n the damaged region shown i n Fig. 7, No. 111. A continuous se r i e s of short, thin, blue streaks move between the
two patches of "stars" i n Fig. 8(a). In Fig. 8(b) a diffuse white discharge
i s taking place t o the l e f t of the stars along a subsidiary crack discovered
when the window was removed. This discharge's motion w a s similar t o a worm. A similar "worm" occurs i n Fig. 8 ( c ) along a crack passing through some of
the larger holes. The worms were quite e r r a t i c i n occurrence; the stars
were a f a i r l y s table phenomena, although varying somewhat i n extent and
brightness.
but were not successfully photographed.
Violent l ightning-like arcs a lso occurred across t h i s region
These windows are the f irst type on which w e seem t o be able t o obtain
fa i lure on every t e s t .
f a i lu re s occurring on the Stanford accelerators.
similar, i n t h a t there are two regions of maximum destruction. In these
X/2 windows the punctured region covers a smaller area and the spacing of
the two regions i s closer and somewhat of fse t from the center of the disk.
The smaller amount of damage may be due t o the re la t ive ly short t i m e of
operation of each disk.
The holes formed are ident ica l t o those found on
The pat tern of holes i s
These are the first extensive observations tha t we have been able t o
make of breakdown on a disk window. While the formation of holes i s s t i l l
obscure, some interest ing phenomena have been seen. It i s apparent, as i n
the J-type t e s t noted above, t h a t a l l v i s ib le ac t iv i ty i s confined t o the
region between and including the damage areas. Holes appear t o form near
or s l igh t ly below the surface, and a t l e a s t one case of "eruption" has
been seen. This would agree well w i t h the r ing of glass-l ike material
surrounding some of the holes. We believe tha t we have seen some ac t iv i ty
occurring at the bottom of the holes after their formation.
W e intend t o continue studies of hole formation on these and similar
types of windows. In addition, an increased e f fo r t w i l l be made t o explain
w h y t h i s par t icu lar geometry i s so susceptible t o t h i s type of damage.
- 31 -
T 1
VIII.
n cd U
.- 32 -
V I I I .
C. OTHER WINDOW WORK
1. Resonant-Cavity Tests
The f i r s t model of a resonant cavity has been constructed using a
shrunk-in 1/8- in . alumina disk. The cavity operates i n the TEl12 mode
w i t h the disk i n the region of maximum f i e ld .
w i l l allow us t o move the window t o other regions.
provided i n one end of the cavity. The cavity has a cold Q of 6000.
A t present the uni t i s being powered by a type-5586 magnetron.
i s pumped by two Vacion ? - l i t e r pumps. The uni t has been operated f o r
only a few days and no experimental r e su l t s have been obtained t o date.
The shrinking technique
A viewing port i s
The cavity
2. Recirculator Power Increase
We are ordering the necessary equipment t o i n s t a l l a la rger klystron
With the present modulator we should be able t o ob- on the recirculator .
t a i n 2 t o 3 times the peak power i n the r ing w i t h a sui table klystron.
Ei ther a Litton type-L 3302 o r one of the M klystrons w i l l be used, oper-
a t ing a t much below t h e i r maximum rat ings. The present tubes, Varian
v~-87's, are now being used a t t h e i r maximum peak-power output. This
change i s being made because it i s apparent that the present 30 Mw i s
insuff ic ient t o cause breakdown i n most types of windows.
3. All-Metal Recirculator
We have s t a r t ed plans f o r the construction of an all-metal very high-
vacuum, resonant ring.
t h i s system, which w i l l be bakeable.
design i s expected t o be the phase shifter, and several d i f fe ren t types
are being studied.
i n in s t a l l i ng t e s t pieces. A t present, s m a l l inaccuracies are compensated
fo r by a s l igh t misalignment of the flanges.
flanges now available w i l l require exceedingly careful alignment and highly
accurate construction.
of vacuum conditions on the operation of windows.
allow the introduction of known contaminators in to a very clean system,
which i s not possible on the present r ing due t o the inherent contamination
caused by poor trapping, organic O-rings, and by not being able t o bake
the ring.
We hope t o obtain a vacuum be t t e r than 10" on
The most d i f f i c u l t par t of the
The re-entrant nature of the r ing may also give trouble
The types of metal-to-metal
This r ing should be useful i n studying the e f f ec t s
In par t icular , it w i l l
- 33 -
T 1
VIII.
4. Mark 111 Window Failure Since July, the f a i lu re ra te of windows on the Mark I11 accelerator
While has dropped from an average of 6.6 per month t o essent ia l ly none,
it i s d i f f i c u l t t o evaluate a l l changes on such a complex system, it now seems that t h i s improvement w a s caused by one change i n operating
procedure.
machine was turned on a f t e r a vacuum shut of f .
sure i n any vacuum system on the machine shuts off the rf power.)
power i s now reduced approximately 50% before turn on and i n 5 sec i s
raised t o full power.
i s involved, time constants tha t are long compared t o a pulse in te rva l
are needed i f the above change i n procedure i s t o be effective.
t o duplicate t h i s effect on the r ing have been unsuccessful t o date.
Before July, the rf power was applied a t f u l l l eve l when the
(Excessive r i s e of pres-
The
It i s obvious tha t whatever process of destruction
Attempts
- 34 -
IX .
I X . MODULATOR STLTDIES
A. SUBCONTRACT SYSTEM DEVELOPMENT FROGRAM
During t h i s past quarter the major subcontract with RCA a t Moorestown,
New Jersey, has continued sa t i s fac tor i ly . A f i e l d t r i p during the week of
18 September t o the RCA f a c i l i t y confirmed tha t delivery of the three pro-
totype modulators,and the 200 kw power supply f o r i n s t a l l a t ion i n Mark IV w i l l be approximately on time,
An examination of t h e work i n process showed tha t RCA has been re-
sponsive i n every major respect t o the statement of work cal led fo r under
Subcontract S-l25. In par t icular , we are pleased w i t h the mechanical de-
sign of the equipment i n tha t it re f l ec t s t h e amount of care they have
taken t o ensure tha t component ava i l ab i l i t y is maximized f o r ease of main-
tenance and minimum down time.
During t h i s period lowPpower breadboard studies a t RCA and full-power
studies at Stanford have confirmed that the pulse-to-pulse amplitude j i t t e r
control c i r cu i t ry w i l l perform as expected.lo Similar breadboard and full- power studies have shown that the pulse-shape requirements of s-125 w i l l
be met by RCA's design.
B. PROJECT DEXELOlXENT ACTIVITIES
1, Ignitron Studies During the Past Quarter
One sample of an ignitron constructed i n accordance with our Drawing
504-g l l l l has been tes ted i n t h i s laboratory with the following resu l t s :
a.
b.
The tube w a s capable of withstanding a 75 kv, rms high-potential t e s t .
The tube was sa t i s f ac to r i ly operated i n a modulator c i r c u i t t o a
hold-off voltage of 29 kv and a pulse-current of 2000 amperes.
taken during these t e s t s confirm t h a t the tube deionizes i n the control-
g r id region i n the time anticipated,
Measurements
c , These t e s t s showed, however, that the i n i t i a l water-jacket design
w a s inadequate. Accordingly, the water jacket w a s improved i n o w labora-
tory by the expedient of so f t soldering the cooling pipes t o the tube body
'OK. L. Brown, e t a l e , "Linear Electron Accelerator Progress at Stanford University," M Report No. 275, Project M, Stanford University, Stanford, California, September 1961.
Stanford, California, July 1961, po 20. IISee Status Report, M Report No. 272, Project M, Stanford University,
- 35 -
I
IX.
along the en t i r e length of the tube.
proved water-cooling scheme appeared Satisfactory.
confirmat ion could be obtained the control-grid sea l ruptured.
After t e s t s were resumed t h i s im-
However, before complete
d. Examination of t h i s s ea l and conferences w i t h the manufacturer
indicate t h a t improper care had been taken i n the fabricat ion of a l l seals.
The General Elec t r ic Company i s now manufacturing new tubes w i t h graded
sea ls t o accommodate the d i f f e r e n t i a l expansion between the al loy 304 s ta in-
l e s s body and the kovar sea l cup.
r ica ted a t General Electr ic , Schenectady, N. Ye, and should be available
fo r t e s t i n g i n about four weeks.
These improved tubes are now being fab-
2. Application of Solid-state Diodes
During t h i s period sil icon-junction diodes have been t e s t ed f o r service
a s end-of-line clippers, hold-off diodes and transformer-backswing clippers,
and fo r service i n the pulse-to-pulse amplitude j i t t e r c i r c u i t .
has been generally sa t i s fac tory i n a l l these applications.
recently have had an unexplainable f a i l u r e i n the transformer-clipper diode
even though it had been operated s a t i s f a c t o r i l y a t full power fo r the order
of 40 hours. The cause of t h i s f a i lu re i s not known a t present. We expect
t h a t the diode assembly may have deter iorated due t o the high-ambient X-ray
f lux i n the region of the assembly.
w i t h s ingle c e l l s of t h i s type t o determine whether or not such X-ray damage
occurs.
Operation
However, we
W e are presently undertaking t e s t s
3. Investigation of Solid-state Switches
We have received a developmental 5000-ampere, 2-kv switch as a conse-
quence of our subcontract with the Shockley Transistor Corporation.
we have been unable fo r various p rac t i ca l reasons t o accomplish i t s t e s t
and evaluation during t h i s period.
w i l l be obtained by 1 November.
However,
We ant ic ipate t h a t complete t e s t data
- 36 -
X.
Xo VACUUM SYSz%M
A. MARK IV CONVEESION The Mark IV vacuum system w a s completed during t h i s quarter. The
en t i r e system consisting of two accelerator tubes, the transmission wave-
guide,and two klystrons and waveguides has been held under a vacuum of
3 x t o r r fo r over a month. The accelerator tubes are a source of
outgassing, so tha t no fur ther improvement i n the vacuum leve l i s expected
u n t i l the tubes can be outgassed by rf power o r by dfrect heating.
B. FEASIBILITY STUDlES
A manufacturers' field-inspection t r i p w a s made for the purpose of
seeing what vacuum equipment manufacturers are doing.
successful from the standpoint, of observing t h e i r e f f o r t s and in t e re s t s
and thus establishing the areas where Project M vacuum research should
be continued.
i n cer ta in areas and count on established manufacturers t o take care of
other system requirements,
The t r i p w a s very
Project personnel w i l l concentrate t he i r research e f f o r t s
C. PROBLEMS
1, The automatic bakeable ultra-high vacuum valve calculations and
study has been s ta r ted ,
2.
3. A new flange and metall ic gasket, system i s under investigation.
Equipment f o r determining the pumping character is t ics of s ix ty
f ee t of waveguide i s being fabricated,
4. Equipment for studying various material outgassing charac te r i s t ics
i s being fabricated,
D. CONCLUSIONS The project research and development effort , has been established by
consulting the l a t e s t research being done by vacuum equipment manufacturers.
The research and development studies needed f o r the two-mile acceler-
a to r are i n various stages of investigation, engineering and fabrication.
Results have been evaluated and w i l l soon be forthcoming.
The Mark IV vacuum system has been operating successfully fo r over a
Further processing i s needed but must be held up u n t i l the rf month.
power or externally applied heating can be used on the system.
- 37 -
XI.
X I . SUPPORT AND ALIGNMENT
A. SITE EARTH MOVEMENT STUDIES
The f i e l d work of t he t h i r d precise elevation survey has been completed.
The f i n a l r e s u l t s have not been presented as ye t ,
a l l observations of t h i s survey be made at night and t h a t t he length of
sightings be l imited t o 50 f t has appreciably improved the closures.
i t i o n a l surveys over the same system of hubs w i l l be repeated periodically.
Verti-
The requirements t h a t
Add-
Hydraulic tilt meters are being experimented with at t he si te.
c a l differential-movement s e n s i t i v i t i e s t o one par t i n t en m i l l i o n are
expected.
upon the results of these experiments.
Extensive use of t h i s method over the e n t i r e s i t e w i l l depend
The survey plan f o r the precise horizontal t r iangulat ion and t r i l a t e r -
Monuments are being placed and precision
It i s hoped t h a t the first survey w i l l
a t ion surveys has been established.
op t ica l equipment i s being purchased.
be completed before the middle of November.
B. SUPPORT
In addition t o the previously discussed support methods, the possi-
b i l i t y of using a forty-foot substructure t o carry four accelerator sections
i s being considered. Adjustable supports i n t h i s design would be placed a t
an appropriate distance i n from each end of t h e substructure so t h a t the
e l a s t i c def lect ion a t the ends and mid-point would be equal.
the adjustment mechanism would be manual but could be extended t o the
klystron housing i f desired.
Operation of
C. ALIGNMENT
An addi t ional optical-alignment proposal has recently been submitted
by Keuffel and Esser Co., Optics and Metrology Division, Hoboken, N. J.
It w i l l be considered along with the numerous other proposals previously
submitted.
- 3 8 -
XII.
X I I . CONTROL SYSTEM STUDIES
A. GENERAL STUDIES DURING THE QUARTER During the past quarter the Instrumentation and Control Group has
continued t o pursue the following objectives.
1. General studies of the operation and maintenance pol ic ies and
of the data communication costs, and technical considerations t h a t w i l l influence the control system design.
studies have been issued during the quarter.
Several reports based on these
2. Technical f e a s i b i l i t y studfes of ideas tha t show promise of sim- Preliminary r e su l t s from a study of magnetic plif 'yingthe control system.
beam-inflection systems are presented below.
One of the staff menibers attended the design study f o r the 300-lOOO
Bev accelerator a t Brookhaven National Laboratory during the month of August and, subsequently, attended the International Accelerator Conference
i n September. A contribution was made t o a chapter on instrumentation of
the report published by the Brookhaven Conference (as a consequence of the
design study), en t i t l ed "A Design Study fo r a 3 0 0 - l O O O Bev Accelerator,"
dated August 28, 1961. Another member of our staff made a t r i p t o Europe as a result of an
inv i ta t ion t o present a paper at the Microwave Measurements Conference i n
London, England. T h i s t r i p also included v i s i t s t o Harwell and Orsay.
Three members of the group v is i ted Brookhaven and Argonne National
Laboratories t o exchange instrumentation ideas Par t icular ly in te res t ing
was the proposed application of d i g i t a l data techniques t o the ZGS machine
a t Argonne.
formation f o r cost estimates i n t h i s f i e l d .
The opportunity t o compare notes a lso provided valuable in-
Considerable time has been spent by the group i n analyzing the equip-
ment requirements f o r the instrumentation of the Project M accelerator,
t e s t accelerator and t e s t stands. Budgetary estimates and scheduling,
which w i l l represent our schedule of work f o r the coming year, resul ted
from t h i s analysis. A s a consequence of project approval the staff has
been increased, and the group now w i l l proceed t o analyzing and itemizing
i n greater d e t a i l the manpower and equipment requirements.
- 39 -
T I
B. MAGNETIC SYSTEMS FOR I N J E C T I O N
During the las t quarter extensive calculations have been made on
several achromatic isochronous beam-transport systems tha t a re applicable
f o r in jec t ing in to and extract ing from electron l i nea r accelerators.
reported at the 1961 Internat ional High Energy Accelerator Conference, we
have been able t o devise systems which sa t i s fy both of these requirements
and have an almost a rb i t ra ry def lect ion angle. A summary of these calcu-
l a t ions i s given below.
A s
A more detai led report i s i n preparation.
The main l imi ta t ion of a def lect ing system used fo r inject ion i s the
debunching.
For a zero-dispersion system that t ransfers a pa ra l l e l beam in to a pa ra l l e l
beam, the path length depends only on the energy of the par t ic le .
The path length of the electrons depends on t h e i r energy.
Among the zero-dispersion systems it i s possible t o have (1) a non-
isochronous system w i t h small debunching; the angle of deviation w i l l be
l imited by t h i s debunching; and (2 ) isochronous systems; for these systems
the path lengths of a l l the pa r t i c l e s of the bunch are the same t o the
f irst order a
The following systems are under study.
1.
The maximum angle of deviation i s 60' and
Three Ident ical Uniform-Field Magnets (Fig. 9)
2 cos a - 1 & = ' 0 s i n a
The debunching i s
Po AP
l o Po
AT = -360°(r s i n a - 3) - -
For p
magnetic f i e l d of 5000 gauss), the debunching fo r each percent of energy
spread i s
= 26.6 cm ( the radius of curvature f o r 40 Mev electrons i n a 0
30° - 3 . 9 O 40' - 4 - 3 0
0 50° -4,1 - 40 -
- 41 -
T
XII.
X I 1 .
This system i s not acceptable fo r an in jec t ion device.
2.
If the deviation is specified, the system is completely determined.
Three Nonidentical Uniform-Field Magnets (Isochronous System) (Fig. 10)
The maximum deviation angle for isochronism i s lo?', and fo r 90' the
results are
and, f o r 105'
a = 87.5' 2a' = 3 5 O
P I P ' 2
3. The conditions are
Two Bending and One Quadrupole Magnets (Fig. 11)
tan a
t an a t an ,5 = -
2
f 2 cos a - =
s i n a (1 + cos a)
The debunching is given by
2 ( a - s i n a)po a & = 360'
xO P
The deviation angle i s 2a.
- 42 -
- 43 -
XII.
d rl
T
XII.
7-’-
/ -7-
a c Ld
- 44 -
X I I .
For p = 26.6 0
4 Deviation Degrees/Percent (Degrees) of AP/P
0.06
0.13 0.23
0.43 0.68 1.00
1.43
If w e assume an energy spread of
of the first section, 60' looks l i k e the maximum possible deviation and
45O, a reasonable value.
5 5$, which is reasonable at the output
a. Geometrical Tolerances
W e have calculated the possible displacement of each of the three
components i n respect t o i t s theore t ica l posit ion.
DH I$
+ %
p d
6 b.
The center of the beam, i f the foca l length i s not properly adjusted,
i s the horizontal displacement of the out.put beam,
is the v e r t i c a l displacement of the output beam.
is the horizontal ro ta t ion of the output beam.
i s the v e r t i c a l ro ta t ion of the output beam.
is the tolerance i n posit ioning the ''centers'12 of each element.
i s the angular tolerance i n posit ioning the ax i s of the elements.
Adjustment of the Focal Length of Quadrupole
0
?Chis center i s the in te rsec t ion of the input axis, t he output axis f o r a bending magnet, and the geometric center fo r a quadrupole.
- 45 -
T
XII.
is displaced by an amount x, where
ap 1 + cos a Af p 2 cos a f x = Po -
For a 45' inflection system, the following tolerance is c mP' ted.
If we replace the rotated-face magnets by n-type magnets (n = 3) the results remain about the same with
4. This system depends on five parameters (a, a ' , -el, & and f) bound by
four conditions. If one free parameter remains, the best compromise seems to be
Four Bending and One Quadrupole Magnets (Isochronous System) (Fig. 12)
a' = 1 0 O 2 0 '
In this case, the compromise requires both not too s m a l l and a' not
too s m a l l , which are two contradictory conditions.
- 46 -
XII.
m
c: 2 R 0 m .d W
I (u r-i
- 47 -
e 50 -
XI1
X I I I .
XIII. RBSEARCH AREA DESIGN
A. M I A T I O N SHIELDING
1. An attenuation measurement has been made using nuclear emulsions
exposed at various depths i n a large stack of concrete (baryte) shielding
t o the 20-Bev scattered external proton beam at the CERN accelerator.
exposure w a s made by Ballam, Lock, Hoffman and others a t CERN. The exposure
w a s done w i t h three s e t s of emulsions, and these have been given t o Stanford,
Harwell, and a DESY-CERN group.
by the emulsion group under Gilbert and Oliver at the Livermore Laboratory,
and it i s hoped tha t a measurement t o an attenuation factor of about lo5 w i l l be possible.
This
The Stanford emulsions are being scanned
2. Clayton Zerby of the Oak Ridge National Laboratory has finished
a Monte Carlo calculation of the longitudinal development of the electro-
magnetic cascade. The r e su l t s agreed within 5% w i t h the d i f f e ren t i a l
photon t rack length of Approximation A of shower theory f o r secondary
energies greater than the c r i t i c a l energy and l e s s than half the primary
energy. These data are being combined with the photoneutron y ie lds pre-
dicted by Dedrick using a photodeuteron model t o give a source strength,
and an analytic calculation of shielding attenuation i s being made. The
coding f o r t h i s calculation i s almost complete.
Zerby w i l l a lso make a calculation of the l a t e r a l shower development.
This w i l l be done a l so i n special configurations such as collimators.
3. We are continuing our calculations of the residual radioact ivi ty
inside the accelerator tunnel and, also, our estimates of the e f fec ts of
ducts through the main shield.
B. AC-TOR HEATING
A calculation has been made by J. Muray of the heating of the accel-
e ra tor s t ructure i f it intercepts the electron beam. An M report on t h i s
w i l l be issued shortly.13
In addition, Muray and J. Cobb have equipped a two-foot length of
accelerator w i t h thermistors t o allow a measurement of the heating of
the accelerator disks when exposed t o the 1 Bev beam of the Mark 111 accelerator. T h i s measurement can be used t o check the calculations.
13J. Muray, "Shower Development and Heating i n the Structure of a 5O-Bev Linear Electron Accelerator," M Report No. 276, Project M, Stanford University, Stanford, California, September 1961.
- 51 -
XV. AC POWER SYSTEM
During the l a s t quarter studies were completed of s i t e - u t i l i t i e s
preliminary-design features, of project-power service, and of the Test
Laboratory definitive-design factors .
A. PRELIMINARY PROPOSAL FOR THF, SITE UTILITIES
Elec t r ica l features of the i n i t i a l u t i l i t y i n s t a l l a t ion were deter-
mined and included i n the Preliminary Proposal f o r the S i t e Utilities.
Prior t o the in s t a l l a t ion of the e l e c t r i c a l service t o the project, needs
w i l l be met by engine-driven generators furnished by ABA.
service connection w i l l be v ia a 60 kv, overhead-transmission l ine . l i n e w i l l t a p the ex is t ing Pacific Gas and Elec t r ic Company's 60-kv system
near the intersect ion of Alpine Road, Santa Cruz Avenue and Serra Road.
It w i l l terminate a t a temporary 60-kv substation located adjacent t o and
south of the proposed beam switchyard.
w i l l feed a temporary 12-kv overhead pole-line d is t r ibu t ion system t o
serve project needs.
ground cables, and the 60-kv substation w i l l be incorporated i n t o the
project master substation complex.
The first power
This
The temporary 60-kv substation
The temporary system w i l l be replaced by 12-kv under-
B. PROJECT POWER SERVICE CONNECTION
Reviews made during t h i s quarter of the envisioned load growth are
summarized i n the following table .
ELECTRICAL POWER LOAD REQUIREN3NTS (Estimate of Septeniber 14, 1961)
Connected Load Mvamps
SulY Januam DescriDtion
Pro j e c t support
Project general u t i l i t i e s
Auxiliary t e s t and research
Accelerator aux i l i a r i e s
Accelerator operation
TOTAL
1.87 1.87 1.00 1.20
11.60 11.60
17 80 21.00
54.24 - 86.51
106.60
142 27
196& 1969
- 54 -
xv.
C. "EST LABORATORY IEFINITIVE DESIGN
Continuing efforts i n connection with the Test Laboratory requirements
and load locations yielded the def in i t ive infomation necessary t o expand
the preliminary data previously reported. l5
i n the def in i t ive design, such as the reduction i n the high-bay illumination
in tens i ty t o 50 foot candles. The special usage areas i n the Test Labora-
tory wing w i l l be at 100 foot candles. changed t o include an 8 Mvamps substation appended t o the building.
Revisions were incorporated
Also, the preliminary design w a s
~~ - -~~
'%tatus Report, M Report No. 272, Project M, Stanford University, Stanford, California, July 1961, pp. 36-37.
T 1
XVI .
XVI. COOLING WATER SYSTEM
A. T W O - M I U ACCEXXRATOR
The master plan fo r the plant water system has been completed except
f o r the location of the water-storage tank. The select ion of a location
f o r the storage tank i s awaiting completion of development o f a possible
water-supply system t o be operated by the City of Menlo Park t o serve
Project M, the Sharon Estate development and Stanford University lands
adjacent t o Project M.
There w i l l be three cooling-tower s ta t ions serving the plant: one large one located about half'way along the two-mile accelerator t o serve
the Klystron Gallery and Accelerator Housing; a second large one located
near the end s ta t ions t o serve them and the beam switchyard; and a t h i r d
and smaller s t a t ion t o serve the buildings i n the laboratory area. The
laboratory area s t a t ion w i l l be the f irst one constructed, t o coincide
w i t h the construction of the Test Laboratory Building.
In the case of the two-mile accelerator, cooling-tower water w i l l be
d is t r ibu ted t o f i f t e e n ident ica l heat-exchanger in s t a l l a t ions spaced about
640-feet apart along the length of the accelerator.
low conductivity, closed-circuit cooling-water systems, serving klystrons, modulators, e t c . , w i l l give up heat t o the cooling-tower water and be
pumped back t o the electronic equipment. This arrangement w a s decided
upon on the bas i s of ABA Report, "Heat Transfer System Study" (ABA-3).
I n the case of the beam switchyard and end-station area, cooling-
A t these points the
tower water w i l l be d is t r ibu ted t o heat-exchanger in s t a l l a t ions located
adjacent t o the major cooling-load centers, where the exchangers w i l l pick
up the heat load from the closed-circuit , low-conductivity, cooling-water
systems e
The laboratory area cooling-water system i s i n the de ta i led design
stage.
B. MARK N The cooling-water system fo r the revised Mark I V machine has been
t e s t ed and f i n a l cal ibrat ions are being made.
c. RESEARCH AND rnvEL0pMENT
See Section III., Accelerator Structure Studies, f o r research and
development work on cooling the accelerator s t ructure .
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XVII.
D I T . HEATING AND VENTILATING
Detailed design of the heating and vent i la t ing system fo r the Tes t
Laboratory Building i s v i r tua l ly complete.
Detailed design of U t i l i t y Building A has been s tar ted. This build- ing w i l l house a central-heating plant, compressed-air equipment, and
air-conditioning refr igerat ion equipment f o r a l l of the buildings i n the
laboratory area.
various buildings. Included i n the design are d is t r ibu t ion l i n e s t o the
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I
