Post on 16-Jan-2016
Christoph Gabor, ASTeC HIPPI—Meeting (WP 5) 26 th – 28th September 2007
Non—destructive transverseemittance measurement device
The Front End Test Stand Collaboration
C. Gabor, J. Pozimski, A. Letchford
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Outline
Introduction FETS, Photo detachment & basic principle of beam diagnostic
Theoretical investigations
Proof of principle experiment Demonstration experiment at a small H- beam line in Frankfurt
Further Hardware
Summary & Outlook
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Layout of the Front End Test Stand FETS
(PD) Diagnostic & Support
Beamstop
IonSource
(PD) Emittance Measurement
3 Solenoids90
sect
or
ma
gne
t LEBT RFQ324 MHz3 MeV
MEBTDiagnosticQuads,
Buncher,Chopper
3MeV beam energy, ~ 60mA H-
50Hz, <2ms (10% duty cycle)
at David Lee andJuergen Pozimski,Imperial College
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Photo Detachment H— beam diagnostic
• non destructive (i.e. no mechanical parts inside the ion beam) => minimizing the influence on the H- beam (on line) highly suitable for high power applications like FETS
• different applications possible: profile(s), emittance ~ electrons, neutrals, laser power attentuation ~ more information about beam are possible, also with good resolution ~ separating neutrals and H- can cause less flexibility because of dipole ~ higher costs compared with a traditional emittance scanner
T hresho ld :=1644nm (0 ,754eV )
M A X : =840nm (1 ,476eV )
Photon energy /a.u. (atomic unit)
0
0,1
0,2
0,3
0,4
0,5
0 0,1 0,2 0,3 0,4
Cro
ss s
ecti
on
/a
.u.
Ine
last
ic r
eg
ion
:>
0,4
a.u
. (1
0,8
...1
4,4
eV
)
- -
-
-
--
-
LASER
Photodetachm ent
Chargeseparation
Magneticdipole
I(t)1dim profile,
long. emi
I(x,y,t)2dim profile,
trans. em i
Detection ofdistribution
y
z
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Non-destructive, transverse H- emittance measurement
H -beam,Neutral atoms produced in the transport section
-
Laser, 1060 nm
H-b
eam
-
Neutra l a tom s produced in the transport section
M agnet poletips
B X
xy
z
Region of interactionand separation of thebeam s
scan
Scintillator
Comparission with a slit—slit emittance instrument:1st slit is replaced by a laser2nd slit is replaced by a scintillator with CCD camera more information (than 2dim) about phase space
Only a small portion of H- will be neutralized,
i.e. max. portion oflaser interaction
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Different emittance measurement principles
Envellope ofthe ion beam
Cross section of the ion beam
sligh tly convergent ion beam envelope
A ngle m easurem ent p laneP osition m easurem ent p lane
"slit--s lit"p rincip le
"po in t--point"princip le
F irst step S econd step
R
R
z
x x
y y
drift length L
P (x ,y )0 0
L(y )0
(y ,y ')0
r= ( x, y)
y
( ,x ',y ')0x ,y0
Slit—slit Principle : only 2dim phase space = 2dim (y,y')Point—point Principle : full 4dim information about phase space
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Photo detachment simulations aboutits transfer function
100
50
-50
-100-20 10-10 20
<PDsimK.dat>
y/mm
y'/m
rad
=0,138 mmmrad100%,rms,n
255075100
-60-40
-2020
040
60Angl
e [mrad]
y= -10mmy= +10mm
Intensity [a.u.]
-15-10-5051015
-10 0 10
x-axis /mm
y-axis
/mm
x
y-20
Left, beam profile I(y') integrated of the emittance pattern and integration of drifted, (100mm) neutralized particles (dots). Right, the "neutralized particles" at +/-10mm and the drifted particles, enclosed by the neutralized patterns, are shown.
beam profile phase space neutralized particles,drifted particles
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Comparision of simulation & measurement
y/m m 10-10
100
50
-50
-100
y'/m
rad
-15 0 15
-20
500m m
20
500m m
50
-50
prf101.spe
prf139.spe
X
Y’
y=-3
,8m
my=
+8,
4mm
2dim yy‘ emittance simulation close to
the experiment
expe
rimen
tal r
esul
ts a
t di
ffer
ent
lase
r po
sitio
ns
simulation of photo neutralized ions of the xy distribution
(drift length 500mm
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Further, current development work
Photodetachment Diagnostic Dipole (FETS)
D:\FETS\MAGNET\POISSON-SIMULATIONEN\H-MAGNET\UEBUNG@UNI\VERS-E_YOKE+COIL VARIATION\DIPOLE016.AM 2-12-2007 18:55:56
-10
0
10
20
30
40
50
60
-10
0
10
20
30
40
50
60
-20 -10 0 10 20 30 40 50 60 70 80 90
good field region20cm
4cm15cm
vacu
umve
sse
l
space for piezo driven stages
arc lenght: 500 mmdeflection angle: 60 degB—field: 0.522 T
I(y)
y
yx
1/e 2H beam-
m in angle
m ax angle
scanningregion
laser beam (reference) path
• homogeneity (waist) along the H- ion beam (collimation/ focusing)• different angles within scanning region
Limiting spatial resolution
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Summary
-- Introduction about Photo detachment ion beam diagnostics Motivation; different principles of diagnostic using photo detachment; Comparison with other emittance measurement methods
-- Theoretical aspects investigations about transfer function of "slit—point" emittance
-- Proof of principle experiment in Frankfurt, Germany
Outlook and recent workFurther hardware:
diagnostic dipole & laser equipmenttesting laser beam line/ movable mirrorsparticle detector (beam test of scintillators like P43, 45improving theoretical understanding
Longitudinal emittance measurement
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Spare slides
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Piezoelectric motors: status
Motion controller
Rotary stage
Amplifiers and
power supplies
Linear stage
Encoders
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Motivation for non-destructive diagnostics
665keV H-
1...3% dc30....40mA500 W/cm2
(by Alan Letchford)
Water cooled end plate of a Fast Faraday Cup
(unfocused ion beam)
Measurements at the current ISIS RFQ
Scintillator image of H- ion beamafter the ion source
=> beam not cylindrically symmetric mainly caused the slit extraction of the ion source
xy intensity distribution of H-,35keV 45mA,
(Ion source test stand)
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Some data about Front End Test Stand FETS
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Integration of a photo neutralized& drifted H- distribution
01
00
20
03
00
400
50
0
Pix
el
<=
> y
' /m
rad
In te nsity I(y ') /a .u . prf129.spe
y=+4,7mm
CCD image (raw data) + P43 with Alu
y
xRelationship between y, y and y'
y
Christoph Gabor, UKNF—Meeting, 3rd October 2007
Laser characterisation, beam guiding
Laser lab at Imperial college
Power meter
Attenuation
CCD camera
Switching mirror