Beam Commissioning & Operation of SRF Modules for PLS-II Younguk. Sohn, Y-D. Joo, I.S. Park, I.H. Yu, M.H. Chun, J.D. Park, J-Y. Haung Pohang Accelerator Laboratory, POSTECH 17 th International Conference on Accelerators and Beam Utilizations November 11-13, 2013, Daejon, Korea

Topics Design for SRF System Operation with NC Cavities Preparation, SRF Module Beam Commissioning with 1 SRF Cavity Beam Commissioning with 2 SRF Cavities Operation for User Runs Home Works Conclusion

Design for SRF System

Design of PLS-II RF System ParametersCommissioningPLS-II Energy [GeV]33 Current [mA] Emittance [nm-rad]-5.9 Harmonic number470 No. of Insertion Devices1420 Electron energy loss / turn - Dipoles [KeV] - Insertion devices [KeV] Beam loss power by synchrotron radiation [kW] RF frequency [MHz] Cavity typeNCSC No. of RF cavities43 Accelerating Voltage [MV] RF Voltage per cavity [MV] Klystron amplifier kW amps kW amp kW amps Cryogenic Cooling K [w]-700

Configuration of SRF System Components Characteristics / Spec. # RF station 3 RF cavity superconducting, CESR-B type RF Control (LLRF) Digital type Amplifier Klystron, 300 kW Waveguide WR1800 Circulator ~350kW

CESR-B SRF Module, Developed in Cornell Uni.

Specifications of SRF Module ParametersValues Resonant frequency [MHz] R/Q [Ω]89 Q0Q0 > 5  MV, Vacc QeQe 1.37 (±0.2)  10 5 Frequency tuning range (step-motor)  150 kHz with resolution of 10 Hz Operating Temperature [K]4.4 Accelerating Voltage / Cavity [MV] Max. RF Power / Cavity [kW]300 HOM RemovalFerrite Absorber Input power couplerWaveguide Window 500 kW in traveling wave cw 150 kW standing wave cw at full reflection

Two SRF cryomodules at #12 Long straight section One SRF straight section 300 kW High voltage supply & Klystron amplifier Cryomodules test facility & He refrigerator Layout & Status, SRF System SRF Phase 1-2 Jan. –Feb CM 3 SRF Phase 2 Jan.-Feb., 2014 CM 1 MCTL (Multi Channel Transfer Line) Microwave transmission line SRF Phase 1-1 Aug.-Sep CM 2 HPRF on Standby

Operation with NC Cavities

Operation, 4 NC  1 st Beam Commissioning : August, 2011 – March, 2012  1 st User Service: March – July, 2012  Easy beam commissioning with less sensitive RF systems  To clean vacuum components before SRF cavities  Long preparation time of SRF modules for fabrication, conditionings and tests Why;

Amplitude & Phase Beam, decay mode Current 50 to 100mA Amplitude Variation (ΔV/V): <0.2%, p-p Phase Variation (ΔΦ) : <0.1 deg. p- p

Preparation, SRF Module and Other Components

Accelerating Bare Cavity Courtesy of Research Instruments, RI

RF Windows Conditioning & Tests, TW ※ Pulse: 1, 2, 5, 10, 20, 50 msec and CW

RF Windows Conditioning & Tests, SW

Characteristics, 300 kW Klystrons Manufacture: THALES Model: TH2161B, power 300kW Site Acceptance Test with KSU-301, input power vs output power For constant anode voltage For constant perveance 200kW 100kW 200kW 100kW

Performance He Refrigerator

Installation, SR Tunnel SRF module 2 SRF module 3

Summary, Commissioning Cryomodule Window & Cavity conditioning  On-resonance and off-resonance  Pulse conditioning: 1, 2, 5, 10, 20, 50 msec and CW mode  Repetition rate: primarily 10 Hz with 1, 2, 5 Hz RF Voltage (Vacc) Measurement  Long term operation: 2.03 MV, Q0=6.8e8 (Spec: >5.0e8), 8 hours  Maximum Vacc: 2.13 MV, Q0=6.4e8 Window Test with CW Standing Wave Power  100 kW for 60 minute (equivalent to 400 kW travelling wave) (Without electron beams)

Leak Check: Cavity from Atmosphere and He vessel  Warm temperature < 2e-10 mbar l/s  Superconducting temperature < 2e-10 mbar l/s  Double check with mass-spectrometer Q external: tunnel Summary, Commissioning Cryomodule – CM2

Window Baking Window vacuum pressure Window temperatures (72 hours)

Pre-cooling Cryomodule with LN FBT far (~10 hour) Cavity top & bottom LN2 GN2

Cooling & Filling with Liquid He (~25 hours) 17.5K/hr cavity bottom ~8 hour ~6 hour~7 hour Required temperature gradient: <30 K/hr, <60 K/(bot-top) Stop cooling

(Frequency) Tuner Characteristics +50 kHz-50 kHz Gradient: 14.8 kHz/mm

Conditioning Window & Cavity 1 msec 2 msec 5 msec 10 msec 20 msec 50 msec CW mode Window Vacuum Cavity Vacuum 2.03 MV !! (~30 hours pulse conditioning before this measurement) Window Vacuum

Q0 Measurement, Vacc vs Q0 Specification ≥ 5.0 x 10 MV

Beam Commissioning with 1 srf Cavities, Sep.-Oct., 2012

Amplitude & Phase Stability Beam Current = mA Detune Phase = 5.4 deg. p-p Amplitude Variation (ΔV/V): 0.2%, p-p Phase Variation (Φ) : 0.41 deg. (p-p) With 1 srf cavity, Decay Mode during 9 hours

Amplitude & Phase Beam Current = mA Detune Phase = 4.9 deg. p-p Phase = 0.58 deg. p-p With 1 srf cavity, Top up Mode during 9 hours Amplitude = 0.5% p-p

Sidebands in mA Sidebands : <-65dBm Harmonics With 1 srf cavity, Top up

Troubles with 1 st Module Operation  He refrigerator trips from voltage sagging of commercial electricity (4 times) and poor operation skill: 8-24 hours per each event beam interruption  Leakage of LHe transfer line between module and valve box, resulted to 7 days’ interruption of user service  Frequent vacuum and downstream of cavity (RBT)  Power dissipations on cavity surface at moment of RF power shut-off by interlok, resulted to cryogenic instabilities (LHe level and return gas flow) Then, the operation statistics of srf system was very poor during 1 st 2 months’ user beam operation ! -MTBF: ~40 hours -Beam availability: 10 days loss with planed 44 days user beam

Beam Commissioning with 2 srf Cavities, Feb.-Mar., 2013

Beam Commissioning Maximum Beam Current with 2 SRF Cavities (2/16) 250 mA Max

Beam Commissioning RF power (2/16) Vrf_CM21.79 Vrf_CM32.04 mA

Beam Commissioning Long Term Operation (13 hours) Beam current: mA, decay / 13h30m

Beam Commissioning Long Term Operation – RF Amplitude (2/17-18) Beam current: mA, decay / 13h30m Vrf_CM2 Stability P-P: 2.18 kV  V/V: Vrf_CM3 Stability P2P: 1.38 kV  V/V: RF Voltage for CM2 RF Voltage for CM3

Beam Commissioning Long Term Operation – Phase Phase_CM2 P-P: deg. Phase_CM3 P-P: deg. Beam current: mA, decay / 13h30m RF cavity phase for CM2 RF cavity phase for CM3

Beam Commissioning with one module only Beam current: 80 mA Life time: 9 hours RF power: Pf=108 kW, Pr=29 kW Vrf: 1.81 MV With in-vacuum undulators Detune idle cavity (CM2) (T.P = 7.35→9.66 mm,  f ~ 34 kHz) M.S: top mode 150 mA

Operation for User Runs

1 st User Beam with 2 Cavities, 125 mA Topup during 8 to May

User Beam, Topup mA during 4 weeks in July

Maximum Stored Beam, 400mA

Maximum User Beam, 250mA Topup from Oct. 29, 2013

RF mA,Topup Amplitude (  V/V <0.2% RMS) DateDuration SRF2SRF3 Peak to peak RMS (0.2% Req.) Peak to peak RMS (0.2% Req.) Long- 24hrs0.23%0.08%0.11%0.04% Short- 1min0.19%0.07%0.08%0.03% Phase (ΔΦ<0.2 deg. RMS) DateDuration SRF2SRF3 RMS Long- 24hrs0.16 deg.0.06 deg. Short- 1min0.04 deg.0.06 deg.

Statistics for Beam Operation 19 March – 24 October, 2013 Provided beam time / planned beam time Mean Time Between Failures

Statistics for Beam Dump 19 March – 24 October, 2013

Statistics for 14 RF Trips Mean Time Between Failure of RF system only: 194 hours 19 March – 24 October, 2013

Target for SRF System, Year 2013  Max. beam current with SRF system: 3 GeV, done  Stable beam operation for user service: GeV, done  Mean Time Between Failures with SRF modules >50 hr, done (194)  Stability for RF amplitude </= 0.2%, done  Stability for RF phase </= 0.2 degree, done

Management, Cavity & Window Vacuums Partial warmup & cooldown, and then conditioning with pulse power

Partial Warmup & Cooldown, Mass-Spectrometer (RGA) 4 days before partial warmup, and 3 days after re-cooldown Before partial warmup After re-cooldown Partial warmup Partial Pressure of Hydrogen (Black)

Home Works, Road to 400 mA Beam One more SRF cavity in coming winter To improve and fine tuning LLRF parameters for higher currents To separate LN2 supply system from He refrigerator (for more accurate frequency stability) More conditioning SRF module itself and vacuum components in PLS-II for high beam current

Conclusion A lot of beam trips during first 2 months operation with one SRF cavity. Cleared nearly all troubles during last winter Now, performance with 2 cavities shows good enough RF design performance is achieved with two cavities 270mA topup beam will be provided in 2 nd half of 2013 One more SRF cavity will be installed in coming winter

Thank you very much for your attention 감사합니다.