T18_VG2.4_Disk_#2 processing summary SLAC Workshop 090708-10 T. Higo and Nextef group Whole history of T18_#2 processing • • • • • • • • 090709 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 SLAC Workshop 2 Processing history for 9 months Nextef startup and careful processing T18_VG2.4_Disk #2 Processing whole RF-ON history 4000 3500 RF-ON vs date (hr) 3000 2500 2000 1500 1000 090709 SLAC Workshop 2009/7 2009/6 2009/5 2009/4 2009/3 2009/2 2009/1 2008/12 2008/11 0 2008/10 500 3 Recovery pass in (T,P) space P SLAC P CERN P KEK 50%P, -20%T 20%P, 20nsT T T aP, -1stepT T In case of number of BD’s even at lower power level than defined 090709 SLAC Workshop 4 Whole BD history of T18_VG2.4_Disk #2 090610 MasterTable_Eacc_Trend till_090610 120 3000 100 2500 80 2000 1500 60 <Eacc> 51nsec Ushi <Eacc> 113ns Ushi <Eacc> 173n ushi <Eacc> 213n Ushi <Eacc> 253ns Ushimoto Eacc keep 253ns Ushi Eacc 51ns Ushi Eacc 113ns Ushi Eacc 173ns Ushi Eacc 213ns Ushi Eacc 253ns Ushi Eacc Usahimoto 2/21-3/23 Eacc 252ns Usahi 4/1-4/7 Eacc 252ns 4/7-14 Eacc 312ns 4/14-16 Eacc 412ns 4/23-27 Eacc 331ns 4/28-5/1 Eacc 252ns 5/1-11 Eacc 412ns 5/11-6/10 40 20 0 0 090709 Total# BD <Eacc> MV/m Total BD 500 1000 1500 2000 2500 3000 RF-ON SLAC Workshop integrated (hr) 3500 1000 500 0 4000 5 Nextef: RF monitors along waveguide Low loss waveguide 2-klystrons 120MW, 300ns klystron—3dB 2.3m 3dB— LLWG 1.5m LLWG 5m LLWG—ACC Str 5.0m WR90 flanges ~36sets*7mm SUS ACC Structure 090709 Loss Kly.Str. ~23% Delay ~ 50ns SLAC Workshop Two klystrons 6 Nextef: Monitors along beam axis PM GV ACC str GV GV FC GV KX03 VAC Q-mass VAC DC FC-UP Qmass 090709 Slit AM 1 87 PM Varian IP VAC 230 WC Insul 425 PM FC DC E FC Lounine IP H load IP Varian IP H IP PM AM E DC WC FC IP H Otsuka load Load FC-Mid SLAC Workshop FC-DN 7 Now T18_VG2.4_Disk #2 has been processed since late October GV FC 090709 SLAC 3dB hybrid Acoustic Plastic scintilator sensors & PMT T18_VG2.4_Disk SLAC Workshop (These are not used effecively.) 8 Big breakdown followed by a breakdown from the very first pulse file number= 3 20081124_210211_1 Red=final, black=previous pulse and blue=-2nd pulse 30 000 30 000 24 000 DPO1 25 000 Fs 15 000 10 000 Ra 20 000 20 000 10 000 5000 10 000 200 18 000 200 200 400 600 800 200 1000 30 000 30 000 20 000 20 000 10 000 10 000 400 600 400 600 800 1000 400 600 800 1000 10 000 800 1000 Tr 5000 5000 0 DPO2 Rs 22 000 20 000 Nominal BD 10 000 30 000 30 000 20 000 Fs 20 000 10 000 10 000 200 400 600 10 000 800 1000 FC-UP 20 000 30 000 200 400 600 10 000 800 1000 200 FC-Mid 20 000 30 000 200 400 600 800 1000 10 000 800 1000 20 000 1st pulse BD, following big BD 30 000 10 000 20 000 5000 24 000 25 000 20 000 22 000 15 000 20 000 10 000 200 10 000 18 000 200 200 400 600 800 200 1000 400 600 800 1000 30 000 20 000 20 000 10 000 10 000 400 600 800 1000 5000 5000 0 30 000 600 30 000 file number= 4 20081124_210301_1 Red=final, black=previous pulse and blue=-2nd pulse 30 000 400 10 000 400 600 800 1000 10 000 10 000 30 000 30 000 20 000 20 000 10 000 10 000 200 400 600 800 1000 200 10 000 10 000 20 000 20 000 30 000 30 000 090709 400 600 800 1000 200 400 600 800 1000 10 000 200 10 000 SLAC Workshop 400 600 800 1000 20 000 30 000 9 Current burst toward upstream 30 000 20 000 10 000 20 000 22 000 Fs 15 000 Ra 30 000 Rs 24 000 25 000 20 000 5000 10 000 200 10 000 18 000 5000 200 0 200 400 600 800 200 1000 30 000 30 000 20 000 20 000 10 000 10 000 400 400 600 800 1000 400 600 800 1000 10 000 600 800 1000 Tr 5000 10 000 30 000 30 000 Fs 20 000 20 000 10 000 10 000 200 10 000 20 000 30 000 400 600 800 1000 FC-UP 200 10 000 20 000 30 000 400 600 800 1000 200 400 600 800 1000 10 000 FC-Mid 200 10 000 400 600 800 1000 20 000 30 000 Rare event but need to understand the mechanism One out of 100 breakdowns Abrupt big burst in current only to upstream no change in RF pulse shape 090709 SLAC Workshop 10 Power at BD’s and BDR during 27 days at 80MV/m (35MW) during RF-ON from 700 ~ 1200 hours since startup Started at 10:00 on BD power vs RF-ON period Nov. 28 Finished at 9:00 on Dec. 25 from Nov. 28-Dec. 25 Total 20 BD's/585hrs (3 BD's are over pulse driven) Power MW (calib. needed) 50 566 hrs run / 643 hrs = 88% ON 40 30 BDR 20 ~17 str. BD / 566 hr 10 ~0.030 BD/hr/str Power MW Excessive power related Power FC-UP Power is calculated from DPO with a background subtraction 0 0 090709 100 200 300 400 RF ON Period (hours) SLAC Workshop 500 ~0.75 x10-6 BD/Pulse/m 600 11 252ns, 65MW Total operation hours >5MW = 140.6 hours Period ACC-IN > 64 MW = 91.7 hours 090709 SLAC Workshop 12 Appearance of breakdowns at 65MW run Breakdowns and other INTLK's during 65MW run Run#29 09027-090305 2070 2060 Total BD 2050 Total BD ACC-BD Following BD FC-UP WG-BD 2040 2030 2020 2010 2200 2250 2300 2350 RF-ON (hrs) 090709 SLAC Workshop 13 252ns, 70MW 090709 SLAC Workshop 14 Appearance of breakdowns at 70MW run Breakdowns and other INTLK's during 70MW run Run#32-2 090403-090407 2160 Total BD 2155 Total BD ACC-BD Following BD FC-UP WG-BD 2150 2145 2140 2720 2730 2740 2750 2760 2770 2780 2790 2800 RF-ON (hrs) 090709 SLAC Workshop 15 252ns, 75MW 090709 SLAC Workshop 16 Appearance of breakdowns at 75MW run Breakdowns and other INTLK's during 75MW run (Run#32-3) 2300 2280 Total BD 2260 Total BD ACC-BD Following BD FC-UP WG 2240 2220 2200 2180 2850 090709 2860 2870 2880 2890 RF-ON (hrs) SLAC Workshop 2900 2910 2920 17 Typical processing / steady-state run • Breakdowns are – mostly followed by a few to several successive breakdowns – typically from the very first pulse at even lower power. • Spurious events exist – with flush of current towards upstream occur from time to time 090709 SLAC Workshop 18 Breakdown rate evaluation T18_VG2.4_Disk #2 Breakdown rate for 252ns and 412ns BDR(ACC) [1/pulse/m] 10-4 0423-0427 (2900hr) BDR(ACC) 412ns BDR(ACC) 252ns BDR(ACC) 252ns 0411-0414 (2800hr) 0227-0305 (2300hr) 0402-0403 (2700hr) 10-5 0520-0525 (3500hr) 0525-0530 (3500hr) 0403-0407 (2700hr) 0401-0402 (2700hr) 0313-0323 (2500hr) -6 10 0530-0610 (3700hr) 1128-1225 (700-1200hr) 0511-0515 (3300hr) 0515-0518 (3400hr) 0501-0507 (3100hr) 10-7 80 85 90 95 100 105 110 115 120 Eacc [MV/m] 090709 It is not so clear from this experiment that the breakdown rate decreases as function of “processing.” SLAC Workshop 19 Breakdown rate versus Eacc Breakdown rate for 252ns and 412ns BDR(ACC) [1/pulse/m] 10-4 BDR(ACC) 412ns BDR(ACC) 252ns BDR(ACC) 252ns 10-5 10-6 y = 2.3888e-18 * e^(0.28603x) R= 0.97016 y = 1.815e-17 * e^(0.24289x) R= 0.94792 10-7 80 85 90 95 100 105 110 115 120 Eacc [MV/m] Exponential fit. 090709 SLAC Workshop 20 Breakdown rate for 252ns and 412ns BDR(ACC) [1/pulse/m] 10-4 BDR(ACC) 412ns BDR(ACC) 252ns BDR(ACC) 252ns 10-5 10-6 y = 5.2958e-61 * x^(27.542) R= 0.96504 y = 2.1053e-60 * x^(26.721) R= 0.94346 10-7 80 85 90 95 100 105 110 115 120 Eacc [MV/m] Cannot discuss functional form due to large scatter. 090709 SLAC Workshop Power fit. 21 R. Ruth at X-band workshop at CI, UK, Dec. 2009 RF Processing of the T18 Structure RF BKD Rate Gradient Dependence for 230ns Pulse at Different Conditioning Time RF BKD Rate Pulse Width Dependence at Different Conditioning Time -4 10 -4 10 After 500hrs RF Condition -5 10 After 900hrs RF Condition -6 10 After 1200hrs RF Condition -7 10 95 100 105 110 Unloaded Gradient: MV/m G=108MV/m BKD Rate: 1/pulse/m BKD Rate: 1/pulse/m After 250hrs RF Condition 10 10 G=108MV/m -6 G=110MV/m 10 115 -5 -7 100 150 200 RF Flat Top Pulse Width: ns This performance maybe good enough for 100MV/m structure for a warm collider, however, it does not yet contain all necessary features such as wake field damping. Future traveling wave structure designs will also have better efficiencies 7/2/2016 X-Band 2008 Page 22 Breakdown rate versus width BDR_vs_Width BDR [1/pulse/m] 10-4 10-5 10-6 BDR = 3e-18 * Tp^5 BDR = 9e-25 * Tp^7.45 -7 10 0 100 200 300 400 500 Width [nsec] Not enough to discuss functional form. But it is evident that the longer pulse makes breakdown rate large with much more than linear dependence. 090709 SLAC Workshop 23 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 090709 SLAC Workshop 24 Breakdown position and timing • Still trying to analyze in detail. • At present, mainly refer to Steffen’s previous analysis – More frequent at downstream 090709 SLAC Workshop 25 Analysis still on the way 137 examples of run24: 60MW, 400ns Rs_timing DPO run34 Rs-Tr Rs_rise 60MW, 400ns Tr_rise 350 500 300 400 250 300 200 200 150 100 100 run34_60MW_400ns timing delay from Rs to Tr 100 50 Rs-Tr 600 Rs_rise, Tr_fall Rs, Tr Timing and Rise/Fall time Tr_timing 0 -50 -100 50 0 -100 0 20 40 60 80 100 120 0 140 -150 0 20 40 60 80 100 120 140 BD*#1 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. 090709 SLAC Workshop 26 Steffen 090227 Breakdown position for 205 ns data 16 14 No. of shots 12 10 8 6 4 2 0 5 10 Breakdown position 15 Red real cell timing, blue linear cell timing, 205 ns data Dark current measurement • Setup FC-UP FC-Mid 75cm 75cm AM FC-DN 195cm • Amount and beta value of dark current versus processing time • Spectrum at RF-ON 2000hrs and 4000hrs 090709 SLAC Workshop 28 Amount of dark current Dark Current 090414 Tp=252ns 100 FC-Mid = 30mA @100MV/m 1 FC-UP ~ FC-Mid/3 FC-UP microA 10 0.1 FC-DN ~ FC-Mid/4 FC-UP microA (253ns, 090225) FC-Mid microA (253ns, 090225) FC-DN microA (253ns, 090225) 0.01 60 70 80 90 100 110 120 Eacc [MV/m] 090709 SLAC Workshop 29 T18_#2 Dark Current evolution 081128-081224-090224-090414-090515 100 100 10 10 microA T18_#2 Dark Current evolution 081128-081224-090224-090414-090515 1 FC-UP [microA] (081128) FC-UP [microA] (081224) 0.1 1 FC-Mid FC-UP microA Dark current evolution 252nsec FC-UP microA (253ns, 090225) FC-UP microA (253ns, 090414) FC-Mid [microA] (081128) FC-Mid [microA] (081224) 0.1 FC-Mid microA (253ns, 090225) FC-Mid microA (253ns, 090414) FC-Mid microA 090515 FC-UP microA 090515 0.01 50 60 70 80 90 100 Eacc [MV/m] 200 0.01 50 60 70 80 90 100 200 Eacc [MV/m] Measured at RF ON 700 – 1200 – 2100 – 3000 – 3400 hours Decreased 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 hours 090709 SLAC Workshop 30 Dark current evolution 252nsec T18_#2 Dark Current evolution 081128-081224-090224-090414-090515 T18_#2 Dark Current evolution 081128-081224-090224-090414-090515 10-3 10-3 I_UP/Eacc^2.5 (081128) FN FC-UP (253ns, 090414) 10-4 I_UP/E^2.5 253ns 090515 beta=36 beta=37 10-5 10-6 0.008 microA/(MV/m)^2.5 FN FC-UP (253ns, 090225) y = 0.14557 * e^(-653.42x) R= 0.99838 y = 0.074674 * e^(-672.19x) R= 0.99772 0.01 0.012 0.014 0.016 (081128) I_Mid/Eacc^2.5 (081224) FN FC-Mid (253ns, 090225) FC-Mid FC-UP microA/(MV/m)^2.5 I_UP/Eacc^2.5 (081224) I_Mid/Eacc^2.5 FN FC-Mid (253ns, 090414) 10-4 I_Mid/E^2.5 253ns 090515 beta=40 10-5 beta=39 y = 0.22345 * e^(-596.01x) R= 0.99982 y = 0.1351 * e^(-607.18x) R= 0.99854 -6 0.018 10 0.008 0.01 0.012 0.014 0.016 0.018 Eacc [MV/m] Eacc [MV/m] Measured at RF ON 700 – 1200 – 2100 – 3000 – 3400 hours No big change in shape nor slope (beta). 090709 SLAC Workshop 31 Deduction of the field enhancement factor Fitting of modified F-N curve I e 2.5 E 6.53109 1.5 E s (V / m ) e a Eacc ( MV / m ) Assuming Es/Eacc=2 actually T18_VG2.4_Disk Es/<Eacc>~2.62 max (Cu)=4.52eV 6530 1.5 23951 a ( Es / Eacc ) a 090709 SLAC Workshop 32 Width dependence Darck current at 103MV/m dependence on pulse width 1000 FC-UP [pA] FC [pA] at 50Hz 800 Upstream current behaves as linear on width FC-Mid [pA] 600 Downstream current has two components. 400 200 0 0 100 200 300 400 090515 Width 090709 500 SLAC Workshop 33 Dark current spectra in June Dependence on power T18_VG2.4_Disk #2 Spectrum_vs_Width at 64MW 090618 T18_VG2.4_Disk #2 Spectrum_vs_power at 252ns 1.2 I_slit_peak [microA] 1.4 1 I_slit_peak [microA] 64MW, 331ns I_slit peak [microA] I_slit_peak [microA] 55MW, 252ns I_slit_peak [microA] 70MW, 252ns I_slit peak [microA] 64MW, 252ns I_slit_peak [microA] 113ns, 64MW I_slit_peak [microA] 64MW, 252ns 1.2 09 Dependence on width 1 0.8 0.6 0.4 0.8 0.6 0.4 0.2 0.2 0 0 0 0 5 10 15 5 10 15 pc (MeV/c) pc (MeV/c) 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. 090709 SLAC Workshop 34 Dark current versus operation frequency 090618 T18_VG2.4_Disk #2 Downstrean dark current vs frequency 350 FC-UP [pA] FC-DN [pA] FC-UP, FC-DN [pA] 300 250 200 150 100 11422.5 11423 11423.5 11424 11424.5 11425 11425.5 11426 Freq [MHz] Increase as operation frequency increases. Easy to be captured for both!? 090709 SLAC Workshop 35 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 090709 SLAC Workshop 36 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 of breakdowns should be better. • Dark current – Decreased during initial processing but stayed constant during a longterm run without higher field nor longer pulse processing. – Energy is at most a half of full acceleration and little exists below a few MeV/c. • Breakdown pulse analysis – Breakdown pulses are still to be analyzed carefully. 090709 SLAC Workshop 37