T18 VG2.4 Disk #2 processing summary · MV/m Total# BD RF-ON integrated (hr) 090610 090709 SLAC...

T18_VG2.4_Disk_#2 processingsummary

SLAC Workshop

090708-10

T. Higo and Nextef group

Whole history of T18_#2 processing

• Installation in Oct. 2008• Steady-state run at 80MV/m in Dec. 2008• Higher field in Jan-Feb 2009• Breakdown rate meas. in Mar.-Apr. 2009• Longer pulse in latter half of Apr. 2009• Breakdown rate meas. May 2009• Various measurement in June 2009• Finish with 4000 hrs operation

090709 2SLAC Workshop

Processing history for 9 monthsNextef startup and careful processing

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9/7

T18_VG2.4_Disk #2 Processing whole RF-ON historyRF-ON

vs date (h

r)


Recovery pass in (T,P) space

CERN

T

P

50%P, -20%T

SLAC

T

P

20%P, 20nsT

KEK

T

P

P, -1stepT

In case of number of BD’s even atlower power level than defined

090709 SLAC Workshop 4

Whole BD history of T18_VG2.4_Disk #2

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MasterTable_Eacc_Trend till_090610

<Eacc> 51nsec Ushi<Eacc> 113ns Ushi<Eacc> 173n ushi<Eacc> 213n Ushi<Eacc> 253ns UshimotoEacc keep 253ns UshiEacc 51ns UshiEacc 113ns UshiEacc 173ns UshiEacc 213ns UshiEacc 253ns UshiEacc Usahimoto 2/21-3/23Eacc 252ns Usahi 4/1-4/7Eacc 252ns 4/7-14Eacc 312ns 4/14-16Eacc 412ns 4/23-27Eacc 331ns 4/28-5/1Eacc 252ns 5/1-11Eacc 412ns 5/11-6/10

Total BD<Eacc> MV/m

Total# B

D

RF-ON integrated (hr)

090610


Nextef: RF monitors along waveguide

SLAC Workshop 6

Two klystronsACC Structure

Low loss waveguide

2-klystrons 120MW, 300nsklystron—3dB 2.3m3dB— LLWG 1.5mLLWG 5mLLWG—ACC Str 5.0mWR90 flanges ~36sets*7mm SUS

Loss Kly. Str. ~23%Delay ~ 50ns

090709

Nextef: Monitors along beam axis

090709 SLAC Workshop

GVGVPM PMAM

Sl i t

FC

E

E

I P

Louni nel oad

Ot sukal oad

DC

I PH

VAC

I nsulVAC

I PDC H

H

Var i an I P

187

KX03 425

FC

I P

Load

Var i anI P

Q- mass

WC WCFC

FC

VAC DC

230

FC-MidFC-UPFC-DN

Qmass

PM PMAM

GVGVACC str

7

Now T18_VG2.4_Disk #2 has beenprocessed since late October

T18_VG2.4_Disk

GV SLAC3dB hybrid

Acousticsensors

Plastic scintilator& PMT

FC

090709 SLAC Workshop

(These are not used effecively.)8

Big breakdown followed by a breakdownfrom the very first pulse

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file number= 3 20081124_210211_1 Red=final, black=previous pulse and blue=-2nd pulse

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file number= 4 20081124_210301_1 Red=final, black=previous pulse and blue=-2nd pulse 1st pulse BD,following big BD

Nominal BD

FsRs Ra

Tr

FC-UP FC-Mid

Fs

DPO

1D

PO2


Current burst toward upstream

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Rare event but need to understand the mechanismOne out of 100 breakdownsAbrupt big burst in current only to upstreamno change in RF pulse shape

FsRs Ra

Tr

FC-UP FC-Mid

Fs


Power at BD’s and BDR during 27 days at 80MV/m (35MW)during RF-ON from 700 ~ 1200 hours since startup

BDR

~17 str. BD / 566 hr

~0.030 BD/hr/str

~0.75 x10-6 BD/Pulse/m0

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20

30

40

50

0 100 200 300 400 500 600

BD power vs RF-ON period from Nov. 28-Dec. 25

Power MW

Excessive power related

Power FC-UP

Pow

er

MW

(ca

lib. n

eede

d)

RF ON Period (hours)

Total 20 BD's/585hrs (3 BD's are over pulse driven)

Power is calculated from DPO with a background subtraction

Finished at9:00 onDec. 25

Started at10:00 onNov. 28

566 hrs run / 643 hrs= 88% ON


252ns, 65MW

Total operation hours >5MW = 140.6 hours

Period ACC-IN > 64 MW = 91.7 hours090709 12SLAC Workshop

Appearance of breakdowns at 65MW run

2010

2020

2030

2040

2050

2060

2070

2200 2250 2300 2350

Breakdowns and other INTLK's during 65MW runRun#29 09027-090305

Total BDACC-BDFollowing BDFC-UPWG-BD

Total BD

RF-ON (hrs)


252ns, 70MW



2140

2145

2150

2155

2160

2720 2730 2740 2750 2760 2770 2780 2790 2800

Breakdowns and other INTLK's during 70MW runRun#32-2 090403-090407

Total BDACC-BDFollowing BDFC-UPWG-BD

Tota

l BD

RF-ON (hrs)


252ns, 75MW



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Breakdowns and other INTLK's during 75MW run (Run#32-3)

Total BDACC-BDFollowing BDFC-UPWG

Total BD

RF-ON (hrs)090709 17SLAC Workshop

Typical processing / steady-state run

• Breakdowns are– mostly followed by a few to several successive

breakdowns

– typically from the very first pulse at even lowerpower.

• Spurious events exist– with flush of current towards upstream occur

from time to time


Breakdown rate evaluation

10-7

10-6

10-5

10-4

80 85 90 95 100 105 110 115 120

T18_VG2.4_Disk #2Breakdown rate for 252ns and 412ns

BDR(ACC) 412ns

BDR(ACC) 252ns

BDR(ACC) 252ns

BDR(ACC) [1/pulse/m]

Eacc [MV/m]

0530-0610(3700hr)

0525-0530(3500hr)

0520-0525(3500hr)

0515-0518(3400hr)

0511-0515(3300hr)

0501-0507(3100hr)

0423-0427(2900hr)

0411-0414(2800hr)

0403-0407 (2700hr)

0402-0403 (2700hr)

0401-0402 (2700hr)

0313-0323 (2500hr)

0227-0305(2300hr)

1128-1225(700-1200hr)

It is not so clear from this experiment that the breakdown ratedecreases as function of “processing.”090709 19SLAC Workshop

Breakdown rate versus Eacc

10-7

10-6

10-5

10-4

80 85 90 95 100 105 110 115 120

Breakdown rate for 252ns and 412ns

BDR(ACC) 412nsBDR(ACC) 252nsBDR(ACC) 252ns

y = 2.3888e-18 * e^(0.28603x) R= 0.97016

y = 1.815e-17 * e^(0.24289x) R= 0.94792

BDR

(ACC

)

[1/

puls

e/m]

Eacc [MV/m]

Exponential fit.090709 20SLAC Workshop

10-7

10-6

10-5

10-4

80 85 90 95 100 105 110 115 120

Breakdown rate for 252ns and 412ns

BDR(ACC) 412nsBDR(ACC) 252nsBDR(ACC) 252ns

y = 5.2958e-61 * x^(27.542) R= 0.96504

y = 2.1053e-60 * x^(26.721) R= 0.94346

BDR

(ACC

) [1/pulse/m]

Eacc [MV/m]

Power fit.Cannot discuss functional form due to large scatter.


7/10/2009 X-Band 2008

100 150 20010

-7

10-6

10-5

10-4

RF Flat Top Pulse Width: ns

BKD

Rat

e: 1

/pul

se/m

95 100 105 110 11510

-7

10-6

10-5

10-4

Unloaded Gradient: MV/m

BK

D R

ate:

1/p

ulse

/m

RF BKD Rate Gradient Dependence for 230ns Pulse at DifferentConditioning Time

After 250hrs RFCondition



RF BKD Rate Pulse Width Dependence at Different ConditioningTime

G=108MV/m

G=108MV/m

G=110MV/m

RF Processing of the T18 Structure


This performance maybe good enough for 100MV/m structure for a warm collider, however, it does not yetcontain all necessary features such as wake field damping. Future traveling wave structure designs will alsohave better efficiencies

R. Ruth at X-band workshop at CI, UK, Dec. 2009

Breakdown rate versus width

10-7

10-6

10-5

10-4

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BDR_vs_Width

BDR [1/pulse/m]

Width [nsec]

BDR = 3e-18 * Tp^5

BDR = 9e-25 * Tp^7.45

Not enough to discuss functional form.But it is evident that the longer pulse makes breakdown ratelarge with much more than linear dependence.


Summary of breakdown rate

• Exponential slope as Eacc– Data scattering band around a slope is by an order

of magnitude

– Slope = an order of magnitude by 10 MeV/m

– Not enough to discuss about the functional form

• Breakdown rate evolution– Reduction of BDR was not seen in last 2000 hours


Breakdown position and timing

• Still trying to analyze in detail.

• At present, mainly refer to Steffen’s previousanalysis– More frequent at downstream


Analysis still on the way137 examples of run24: 60MW, 400ns


-150

-100

-50

0

50

100

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run34_60MW_400nstiming delay from Rs to Tr

Rs-Tr

Rs-Tr

BD*#1

-100

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DPO run34 60MW, 400nsRs_timing

Tr_timing

Rs_rise

Tr_rise

Rs, Tr Timing and Rise/Fall time

Rs_rise, Tr_fall

BD*#

Timing of Rs rise and Tr fall show correlation.Two cases: those at the same time and those at 50ns later.Position and time of the breakdown should be deduced from Rs and Tr.FC current burst timing and amount should be integrated in the analysis.Breakdowns from the very first pulse are missing; should be included in the analysis.

Red real cell timing, blue linear cell timing, 205 ns data

5 10 150

2

4

6

8

10

12

14

16

Breakdown position

No.

of s

hots

Breakdown position for 205 ns dataSteffen 090227

Dark current measurement

• Setup

• Amount and beta value of dark current versusprocessing time

• Spectrum at RF-ON 2000hrs and 4000hrs

75cm 75cm 195cm

FC-DNFC-UP FC-Mid AM


Amount of dark current


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Dark Current 090414 Tp=252ns

FC-UP microA (253ns, 090225)FC-Mid microA (253ns, 090225)FC-DN microA (253ns, 090225)

FC-UP micro

A

Eacc [MV/m]

FC-Mid = 30 A@100MV/m

FC-UP ~ FC-Mid/3

FC-DN ~ FC-Mid/4

Dark current evolution 252nsec

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T18_#2 Dark Current evolution081128-081224-090224-090414-090515

FC-UP [microA] (081128)

FC-UP [microA] (081224)

FC-UP microA (253ns, 090225)

FC-UP microA (253ns, 090414)

FC-UP microA 090515

FC-UP mi

croA

Eacc [MV/m]

0.01

0.1

1

10

100

50 60 70 80 90 100 200


FC-Mid [microA] (081128)

FC-Mid [microA] (081224)

FC-Mid microA (253ns, 090225)

FC-Mid microA (253ns, 090414)

FC-Mid microA 090515FC-Mid micr

oA

Eacc [MV/m]

Measured at RF ON 700 – 1200 – 2100 – 3000 – 3400 hoursDecreased by a factor 2 between processing with max Eacc 80 110MV/m,

but no more suppression in the following steady-state run for more than 1000 hours090709 30SLAC Workshop

Dark current evolution 252nsec

10-6

10-5

10-4

10-3

0.008 0.01 0.012 0.014 0.016 0.018


I_UP/Eacc^2.5 (081128)

I_UP/Eacc^2.5 (081224)

FN FC-UP (253ns, 090225)

FN FC-UP (253ns, 090414)

I_UP/E^2.5 253ns 090515

y = 0.14557 * e^(-653.42x) R= 0.99838

y = 0.074674 * e^(-672.19x) R= 0.99772

FC-UP microA/(MV/m)^2.5

Eacc [MV/m]

beta=37

beta=36

10-6

10-5

10-4

10-3

0.008 0.01 0.012 0.014 0.016 0.018


I_Mid/Eacc^2.5 (081128)

I_Mid/Eacc^2.5 (081224)

FN FC-Mid (253ns, 090225)

FN FC-Mid (253ns, 090414)

I_Mid/E^2.5 253ns 090515

y = 0.22345 * e^(-596.01x) R= 0.99982

y = 0.1351 * e^(-607.18x) R= 0.99854

FC-Mid micro

A/(MV/m)

^2.5

Eacc [MV/m]

beta=40

beta=39

Measured at RF ON 700 – 1200 – 2100 – 3000 – 3400 hoursNo big change in shape nor slope (beta).


Deduction of the field enhancement factor

)/()/(1053.6

5.2

5.19

mMVEmVE accs eeE

I

23951)/(

6530 5.1

accs EE

(Cu)=4.52eV

Assuming Es/Eacc=2actually T18_VG2.4_Disk

Es/<Eacc>~2.62 max

Fitting of modified F-N curve


Width dependence

Upstream currentbehaves as linear onwidth

Downstream current hastwo components.

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1000

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Darck current at 103MV/mdependence on pulse width

FC-UP [pA]

FC-Mid [pA]

FC [p

A] at 50Hz

Width 090515


Dark current spectra in June

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T18_VG2.4_Disk #2Spectrum_vs_Width at 64MW

I_slit_peak [microA] 64MW, 252ns

I_slit_peak [microA] 113ns, 64MW


I_s

lit peak [microA]

pc (MeV/c)

090618

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T18_VG2.4_Disk #2Spectrum_vs_power at 252ns




I_s

lit peak [micr

oA]

pc (MeV/c)

090618Dependence on power Dependence on width

Actual field of analyzer magnet was checked.The formula used up to now pc[MeV/m] = 1.646 x I [A] = 8.23xRef. Volt. [V] was confirmed.

Two peaks appear and higher for higher momentum one.Less than ½ of full acceleration.Little exists below 2.5MeV/m.


Dark current versus operation frequency

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350

11422.5 11423 11423.5 11424 11424.5 11425 11425.5 11426

T18_VG2.4_Disk #2Downstrean dark current vs frequency

FC-UP [pA]

FC-DN [pA]

FC-UP, FC-DN [pA]

Freq [MHz]

090618

Increase as operation frequency increases.Easy to be captured for both!?


Dark current behaviour• Amount

– to upstream << to downstream– Divergent: 1/4 from Mid to DN– Linear vs pulse width

• Reduction of dark current– By a factor 2~3 during first 2000 hrs– No reduction after 2000 hrs

• Beta value– Stayed almost constant from 700hrs to 3300 hrs– Not processed?

• Spectrum– Two peaks below half of full acceleration


Conclusion• Established a basic procedure of processing and evaluation

– Can proceed a series of structure tests

– Better to further develop a system in such as• Phase measurement, missing energy evaluation, etc.

• Breakdown rate was evaluated.– Gross comparison with that of SLAC is consistent with each other.

– In order to precisely compare, power estimation and identification ofbreakdowns should be better.

• Dark current– Decreased during initial processing but stayed constant during a long-

term run without higher field nor longer pulse processing.

– Energy is at most a half of full acceleration and little exists below a fewMeV/c.

• Breakdown pulse analysis– Breakdown pulses are still to be analyzed carefully.


T18 VG2.4 Disk #2 processing summary · MV/m Total# BD RF-ON integrated (hr) 090610 090709 SLAC...

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Transcript of T18 VG2.4 Disk #2 processing summary · MV/m Total# BD RF-ON integrated (hr) 090610 090709 SLAC...