High power CW tests of cERL main-linac cryomodule Hiroshi Sakai, Kazuhiro Enami, Takaaki Furuya, Masato Sato, Kenji Shinoe, Kensei Umemori (KEK) Masaru Sawamura(JAEA), Enrico Cenni (Soken-dai) Contents • Introduction for Cryomodule for cERL main linac • cool down to 2K and performence test at 2K • Results of High power test • cryomodule displacement & microphonics • Summary 1 SRF2013 @Paris. (2013.Sep.23-Sep.28)
Compact ERL(cERL) at KEK Current : 10-100mA 2 V Emittance : 0.1-1 mm mrad Apparatus of cERL loss Ploss = 25W/m (15MV/m) c P R / Q Q Bunch length :0.1-3ps 0 cERL parameters Red: initial case Requirements of cERL main linac Frequency : 1.3 GHz Gradient: 15MV/m Q0: >1*10^10 Beam current : max 100mA (100mA (in)+ 100mA(out)) HOM-BBU calculation ERL-model-2 cavity ： 600mA can be circulated in design (w/o HOM randamization) H.Sakai et al., Proc. of ERL07 (2007). All HOMs damped to both end F 100 (SBP) Iris : f 80 F 120 (LBP) 0.7 0.6 KEK-ERL Model-2 (HOM: 6x2) threshold current (A) 0.5 simulation by BI 0.4 HOM absorber HOM absorber 0.3 Calc by R. Hajima, Parameters of cERL main linac ():TESLA cavity R.Nagai, KEK-ERL Model-1 (HOM: 6x2) 0.2 Frequency 1300 MHz Eacc 15-20MV/m 0.1 TESLA (HOM: 5x2) Q0 1e+10 Coupling 3.8 % (1.9%) (TESLA 20mA) 0 R sh /Q 897 Ω (1007Ω) Q o × R s 289 Ω 0 50 100 150 200 250 300 350 400 E p /E acc 3.0 (2.0) H p /E acc 42.5 Oe/(MV/m) phase advance in the ERL loop (deg.)
Compact ERL main linac cryomodule configuration HOM absorber 9cell superconducting ・ HIP ferrite on Copper beampipe cavity ・ Operation at 80K. (expected 150W HOM power) Q0 > 1*10^10 @15MV/m ・ Check enough absorption ability of ferrite at 80K 5K frame e- ERL model-2 9cell Nb cavities 80K (Compact) ERL target 2K Frequency : 1.3 GHz 80K 80K Input power : 20kW CW (SW) Gradient: 15MV/m 80K 2K Q0: >1*10^10 Beam current : max 100mA e- (against HOM-BBU instability) 80K 2-cavity cryomodule was developed for compact ERL main linac to demonstrate the Input coupler high current ERL operation at ・ 20kW CW (standing wave) cERL. We have done the high ・ Cold and warm window Frequency Tuner power test by using this ・ HA997 ceramic is used Slide jack tuner (mechanical) 3 cryomodule. ・ QL=(1-4)*10^7(variable) piezo tuner(fine tuning)
Results of vertical test of cERL Main linac two cavities K.Umemori et al., Proc. of IPAC12, p2227 Carried out V.T of 2 ERL-model-2 cavities for cERL in 2011. For module assembly Achieve 25MV/m (administrative limit) : Satisfy cERL requirement : Q0>1*10^10@15MV/m ERL 9-cell #4 cavity ERL 9-cell #3 cavity • X-ray onset : 22 MV/m • X-ray onset : 14 MV/m : Requirement of cERL Field emission profile by rotating X-ray mapping Simulation (with Fowler Nordheim eq.) Candidate of source (#3 cav., 2nd VT, Eacc=22MV/m) PIN diode Field emission Profile on Nb surface See detail simulated with including EGS5 Enrico Cenni (radiation with materical interaction) Broad signals IPAC12, p295, and Doctor thesis Source on iris Sharp traces on cell Measured profile were clearly explained by simulation . 4 H.Sakai et al., Proc. of IPAC 2010 ,p2950 We can know the localized source of field emission in V.T
Cavities, HOM absorbers and cold window of input Module Assembly after V.T couplers were assembled in class 4 clean room supported by backbone through 5K frame support 2012/Mar 2012/Aug 5K frame 5K frame support After Ar gas purging into cavities,He jacket, were welded on cavities. Diameter of jacket is 300 Backbone set at 300K mm to make He level inside the jacket to fulfill CW operation , 2012/Sep 2012/Oct Keep alignment within 0.2mm After fixing alignment, warm window were set and vacuum Assemble He line, magnetic shield, thermal 5 vessel were mounted. Gate valves were set on both sides Insulator, sensor and so on
Setup of high power test at cERL beam line 30kWIOT Setup of high power test #4 cavity （ upper ） #3 cavity （ lower ） Radiation monitor shield shield Installed in cERL beam line PIN radiation profile monitor set around beam axis Si PIN diode set around beam axis 16 Si PIN diodes at each position #3 cavity （ lower ） #4 cavity （ upper ） SBP side LBP3 LBP4 SBP3 SBP4 6 LBP side
Crack of damper ferrite at Green ： 80K line Cryomodule Cooling to 2K thermal cycle test Blue ： 2K line Light bule ： 5K line Strategy of cooling Gas He out for Gas He outline precooling ・ HOM damper should be cooled down slowly, to avoid cracking of ferrite.3K/h #3 cavity #4 cavity was required for 80K line, which cool the HOM dampers. ・ Relatively large temperature difference was avoided within each 2K, 5K(He) and 80K(N 2 ) lines. He inlet History of 2k cooling Lower LBP absorber Upper LBP absorber SBP absorber Keep 3K/h Lig N2 supply For 24 h Lig He supply Only daytime 7
Performance test of cERL cryomodule Performance of frequency tuner HOM properties under 2K condition shaft Mechanical tuner PU 10 7 10 7 HOM1 HOM2 HOM3 calc (Dipole) 2 Piezo tuner 10 6 10 6 calc (Monopole) 10 5 10 5 Loaded Q Cancel pressure variation Loaded Q Coarse mechanical tuner stroke @ 2K 10 4 Piezo performance @ 2K 10 4 10 3 10 3 D f >1kHz@2K at 0-500V 10 2 10 2 2 turn around 10 1 10 1 1000 1500 2000 2500 3000 1000 1500 2000 2500 3000 1.3GHz Frequency (MHz) Frequency (MHz) D f =600kHz #4 cavity • Using fundamental pickup port (PU) 3 turn around) with 2mm and HOM ports (HOM1, 2, 3), stroke HOM characteristics were measured. • Their behavior, frequency and Course and fine piezo tuners also worked smoothly and loaded Q-values, were generally agreed with calculation results. had enough stroke under 2K cooling. 8
Results of high power test (Vc vs Q0) Max input power Upper QL : 1.54*10^7 (Pin) is 5kW during Lower QL : 1.15*10^7 • High power test was done one by one cavity. high power test • Input coupler was processed up to 25kW before #4 high power test. (upper ) • Both cavities reached to Vc = 16MV. • Q 0 of #4 cavity decreased during processing. • Field emission on-set was 8-9 MV for both burst cavities. • Low field (<10MV/m) reached Q0>1*10^10. (no (before burst) effect of HOM damper and magnetic shield works well. ( Mika Masuzawa , WEIOD02 ) (after burst) Measured radiation of each cavities at final state #3 (lower) Ref ： # ４ (upper) blue ： # ３ (lower) Max field 16MV appplied. ~ Eacc (MV/m) 9 : Requirement of cERL
Detail radiation profile measurement Sudden burst event was observed under keeping field of 14.5MV Before burst After burst #3 #4 cav (lower) #4 (upper ) Field decreased ・ Radiation pattern was changed from V.T ・ Another new radiation sources were produced ・ Radiation pattern also changed after X-ray burst during assembly work and high power test.
Enrico Cenni et al., TUP091 in SRF2013 Survey location of field emission source by NaI Measured spectrum (at 8.5MV) NaI detector set on beam axis Gate valve cryomodule Cavity #3 (up) 2min Cavity #4 (dowm) 0.7m Different energy spectrum were observed with same gradient 2x2mm collimator by Pb shield Reachable energy at gate valve (eV) Comparison between Estimated source position 2,0E+07 measured data and simulation Iris 1-2 1,8E+07 with different Eacc Cav4 1,6E+07 Cav3 Iris 2-3 1,4E+07 MAX 1,2E+07 Iris 3-4 1,0E+07 8,0E+06 6,0E+06 4,0E+06 Position near SBP and input port is estimated as a 2,0E+06 radiation source. String assembly work was poor 0,0E+00 near SBP side ?? Coupler also caused the burst ?? 0 5 10 15 20 Accelerating field (MV/m) 11 Measured error is assumed end point of bremsstrulung effect
Vc keep test Accelerating Voltage 13.5MV 14.2MV #3 (Lower) #4 (Upper) 1hour 1hour ・ We can keep the following voltages of Accelerating voltage was kept stably Upper cavity ： 14.2MV Lower cavity : 13.5MV He pressure Return He gas for more than 1 hour. (40-45W heat @2K) ・ We cannot keep more than 14.5MV field because of the lack of the cryogenic power (>50m^3/h ～ 50W) He level We note that He gas return, He level and He pressure were also stable. Especially He pressure was kept stable within 10Pa (measured) 12
H.Sakai et al., MOP069 in SRF2013 Measurement of displace ment unde 2K cooling WLI monitor ( 10um reslution) (1-4) target Alignment telescope Temperature of 5K frame (5-8) Alignment target Measured displacements of targets Move same way with targets at same transverse position Summary of displacements Horizon Vertic of targets and cavities tal al between RT to 2K (mm) (mm) Target 1-4 (Average) -0.11 -1.06 Target 5-8 (Average) 0.87 -0.37 • About 0.4mm of cavity center movement was evaluated horizontally and Average movement of cavity 0.39 -0.37 vertically , which agreed with expected values of thermal shrink of 5K supports. • These vales were within alignment error from beam requirement of 1mm. center (from target 5-8)
2K microphonics measurements • Example of#3 cavity, QL = 1.15*10^7 oscilloscope Pk-pk =7Hz • measure Df (Pin and Pt) • LLRF Feedback loop off • Field set to 2.5MV/m ・ Pk-pk = 7Hz by oscilloscope. It allow us to increase the QL higher than several *10^7 lower power ・ Main peak was observed at 49.5Hz (not 50Hz of electrical noise) by FFT analyzer ,which was not come from cavity resonance frequency. We need to continue measuring michrophinics on next cERL operation
Recommend
More recommend
