TD18 High Power Test ResultsFaya Wang

Chris AdolphsenMay 3, 2010

In NLCTA Beamline Structure Note Performance

4/08 – 7/08T18vg2.6-Disk

SLAC_1Cells by KEK,

Assembled at SLAC

Good: 105 MV/m, 230 ns at LC BDR spec of 8e-7/pulse/m but hot cell

developed

7/08 – 10/08T18vg2.6-Disk

SLAC_1Powered from

Downstream EndGood: 163 MV/m, 80 ns, 2e-5 BDR in last cell, consistent with fwd operation

12/08 – 2/09T18vg2.6-Disk

CERN_1CERN Built, Operate

in Vac CanVery Poor: very gassy with soft breakdowns at 60 MV/m, 70 ns

Test at KEK10/08 – 06/09

T18vg2.6-DiskKEK_1

Cells by KEK, Assembled at SLAC

Good: 102 MV/m, 240 ns at LC BDR spec – no bkd location info

7/09 – 8/09T24vg1.8Disk

CERN_1CERN Built, Cells

Pre-FiredPoor: achieve < 60 MV/m after 100 hours with pulse lengths < 100 ns

5/09 - presentT18vg2.6-Disk

SLAC_2Cells by KEK,

Assembled at SLACGood: after 280 hours, 97 MV/m, 230 ns

at LC DBR spec – one hot cell

12/09 -4/10TD18vg2.3-Disk

SLAC_1Cells by KEK,

Assembled at SLACFair: after 1000 hours, 81 MV/m, 230 ns

at LC DBR spec – no hot cells

CLIC Disk Structure Tests

a [mm] 4.06 3.36 2.66a/l (%) 15.4 12.8 10.1d [mm] 2.794 2.054 1.314e 1.21 1.18 1.15 f [GHz] 11.424 11.423 11.424Q(Cu) 5098 5364 5458vg/c [%] 2.25 1.47 0.87r’/Q [LinacΩ/m] 10195 12560 15034Es/Ea 1.97 1.88 1.88Hs/Ea [mA/V] 5.85 5.2 4.85Sc/Ea2 [mA/V] 0.52 0.39 0.3

0 100 200 300 400 500 600 700 800 900 10000

5

10

15

20

25

n

|Ez|

[kV

/m]

For regular cellsP = 59.8 MW for <G> = 100 MV/m

Active Length = 15.8 cm

First Middle Last Cell

TD18 Parameters

A. Grudiev

TD18 Parameter Plots for an Unloaded Gradient of 100 MV/m

0 2 4 6 8 10 12 14 16 180

50

100

150

200

250

iris number

P [M

W] (

blac

k), E

s (gre

en),

Ea (r

ed) [

MV/

m],

T

[K] (

blue

), S

c*50

[MW

/mm

2 ] (m

agen

ta)

29.1

47.0

155

226

3.2

4.4

79

120

57.5

34.3

Pinload = 57.5 MW, Pout

load = 34.3 MW Eff = 0.0 % tr = 0.0 ns, tf = 0.0 ns, tp = 100.0 ns

High T : 47 degCfor 100 ns Pulsewhereas T18 is only 12.5 degC

0 5 10 15 200

50

100

150

200

250

iris number

T18 vg2p6 disk

8.1 12.5

148

232

2.7

4.4

76

126

53.037.4

T18

Last Cell Surface Magnetic Field

High Power Operation History

Final Run at 230 ns: 94 hrs at 100 MV/m w BDR = 7.6e-5 60 hrs at 85 MV/m w BDR = 2.4e-6

0 200 400 600 800 1000 12000

20

40

60

80

100

120

140

Accumulated rf process time (hr)

BDR (1/hr)<G> for regular cell (MV/m)Pulse width (divided by 10) (ns)

BDR Evolution with RF Processing

0 500 1000 150010

-6

10-5

10-4

10-3

RF Process Time (hr)

BD

R (1

/pul

se/m

)

100MV/m@100ns100MV/m@150ns100MV/m@200ns100MV/m@230ns

0 1000 2000 3000 400010

-6

10-5

10-4

10-3

Accumulated Breakdown Events

BD

R (1

/pul

se/m

)

100MV/m@100ns100MV/m@150ns100MV/m@200ns100MV/m@230ns

TD18 Breakdown Location Profile at Different Stages of Processing

0 5 10 15 200

50

100

150

200

250

Regular Cell No.

BD

R E

vent

s

0 ~ 200 hrs200 ~ 400 hrs400 ~ 600 hrs600 ~ 700 hrs700 ~ 960 hrs 0 ~960 hrs

0 5 10 15 200

10

20

30

40

50

Cell No.

Per

cent

of B

KD

Eve

nts

394 BKDs within 0~250hrs193 BKDs within 250~500hrs298 BKDs within 500~750hrs57 BKDs within 750~900hrs74 BKDs within 900~1000hrs34 BKDs within 1000~1200hrs24 BKDs within 1200~1400hrs

Did not find visual evidence related to the hot cell in a post-run boroscope exam – typical of NLC/GLC structures, many of which had hot cells

T18 Breakdown Location Profile at Different Stages of Processing

98 100 102 104 106 108 110 11210

-7

10-6

10-5

10-4

10-3

Gradient (MV/m)

BD

R (1

/pul

se/m

)

500 hr

250 hr

1400 hr

900 hr

1200 hr

TD18 700 hr

Comparison with T18_SLAC1

Pulse width 230ns: Green line for TD18, Others for T18

LC Breakdown Limits• For NLC, the breakdown rate limit was chosen so that the 2% pool of spare rf units

would rarely (once a year) be depleted assuming a 10 second recovery period after each breakdown. Operation with a 10 second recovery period has been demonstrated but longer times (30-100 sec) are typically used since the structure monitoring system has a 30 second sampling period. For 60 Hz operation at NLCTA, the breakdown rate limit translates to 0.1 per hour with the nominal 60 cm long structure design. This choice is somewhat soft in that a four-times higher rate would still provide 99% full-energy availability assuming a 5 second recovery time, which has also been demonstrated.

• For reference, at the 0.1 per hour limit, a breakdown would occur in one of the ~ 20,000 NLC X-Band structures once every 120 pulses. Such breakdowns will degrade the luminosity from that pulse, but the beam kicks from the breakdown fields should not inhibit beam operation.

• To 'translate' this limit, for one bkd in 10 hours in a 0.6 m structure at 60 Hz, the rate is 4.6e-7/pulse/structure or 7.7e-7/pulse/m. For CLIC 3-TeV, this same limit gives 1 bkd per 40 pulses, but because of the smaller beam emittance (and hence a smaller collimator aperture), the kicks are more likely to hit the collimators. The bkd kick distribution measured at NLCTA has values as large as 30 keV/c - this level is < 1/10 of the amount needed to hit the collimators at NLC.

Can TD18 Run with no Recovery Period ?

1 2 3 4 5 6 70

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Frac

tion

of b

reak

dow

n ev

ents

Cascaded events

All eventsMulti-event taken as one event

Type 1 2 3 4 5 6 7

Events 77 23 5 5 1 2 1

33 Hour Test Period

180 185 190 195 200 205 210 215

2468

pulses

Inpu

t ref

(arb

.u.)

24 26 28 30 32 34 362468

1012

pulses

Inpu

t ref

(arb

.u.)

150 160 170 180 190 200 2100

5

10

15

pulses

Inpu

t ref

(arb

.u.)

155 160 165 170 1752468

1012

pulses

Inpu

t ref

(arb

.u.)

Cascaded BDR Test at 100 MV/m @ 200ns

BDR Pulse Width Dependence

50 100 150 200 25010

-6

10-5

10-4

10-3

Pulse Width (ns)

BD

R (1

/pul

se/m

)

@80~140 hr@280~360 hr@700~960 hr

100 150 200 25010

-6

10-5

10-4

Pulse Width (ns)

BD

R (1

/pul

se/m

)

T18, 108 MV/m @ 250 hrsT18, 108 MV/m @ 500 hrsT18, 110 MV/m @900 hrsTD18, 100 MV/m @ 80~140 hrsTD18, 100 MV/m @ 230~360 hrsTD18, 100 MV/m @700~960 hrs

100 MV/m

BDR Pulse Heating Dependence

20 30 40 50 60 70 80 90 10010

-7

10-6

10-5

10-4

10-3

Peak Pulse Heating at Last Cell (K)

BD

R (1

/pul

se/m

)

T18, 900 hrsTD18, 100 MV/m @ 100ns,870hrsTD18, 100MV/m@ 150ns, 960hrs TD18, 100MV/m@200ns, 750hrsTD18, 115MV/m@150ns, 550hrsTD18, 120MV/m@150ns, 570hrsTD18, 100MV/m@230ns, 700hrsTD18, 105MV/m@230ns, 680hrsTD18, 100MV/m@50ns

110 MV/m

1st cell 62% of last cell at pulse heating

Pulse Heating under Different Conditions

0 500 1000 1500 20000

10

20

30

40

50

60

70

80

90

Time (ns)

Pea

k P

ulse

Hea

ting

in L

ast C

ell (

K)

100 MV/m, 100 ns - square pulse

120 MV/m, 100 ns

100 MV/m, 200 ns

115 MV/m,150 ns

100 MV/m, 150 ns

0 500 1000 1500 20000

10

20

30

40

50

60

Pulse Width (ns)

Pow

er to

Strc

utur

e (M

W)

200 ns @ 100 MV/m150 ns @ 100 MV/m

Pulse Heating BDR Test

0 500 1000 1500 2000-10

0

10

20

30

40

50

60

70

Time (ns)

Pow

er to

Stru

ctur

e (M

W)

150ns - normal150ns - pre heating

0 500 1000 1500 20000

20

40

60

80

Time (ns)

Pea

k P

ulse

Hea

ting

in L

ast C

ell (

K)

100 MV/m, 200 ns100 MV/m, 150 ns100 MV/m, 150 ns pre-heating

60 65 70 750.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

Peak Pulse Heating in Last Cell (K)

BD

R (1

/hou

r)

100MV/m@150ns100MV/m@150ns + pre-heating100MV/m@200ns

TD18 Summary• Structure performed worse than T18 even though it did not have

any hot cells. TD18 bead pull data also shows a large phase advance change unlike that for T18 where no change is observed (see Juwen’s talk).

• BDR pulse heating dependence suggests that operation above 50 degC may be a factor (as it appears to be in single SW cell data)

• Pre-heating test at constant gradient confirms the pulse heating sensitivity (although the statistics are low) – Factor of ~ 3 BDR increase similar to that seen with no pre-

heating for the same temperature range. • Perhaps should not draw too strong of conclusion given that this is

just one structure, and the KEK TD18 results are even more puzzling.