1、Design of a superconducting third harmonic cavity for SSRFHongtao HOU On behalf of RF group2018-06-28Hongtao Hou,TTC workshop,RIKEN,Japan,June 2018Contents1.Background2.Design Specification3.Harmonic Cryomodule Design4.SummaryHongtao Hou,TTC workshop,RIKEN,Japan,June 20181.Background:MotivationFSSRF
2、 beamline phase-II project Installation of more insertion devices will decrease the beam lifetimeFFunction Lifetime increase Beam performance improvement Instabilities suppressionFAdvantages Provide Landau damping of synchrotron oscillations:suppress coupled-bunch and microwave instabilities Increas
3、e threshold of single bunch instabilitiesFHarmonic cavities for bunch lengthening Resonant at fharm=n fRF (often n=3)Passive/active:no external power source required for passive system NC/SC:SC has sufficient impedance even at low currentHongtao Hou,TTC workshop,RIKEN,Japan,June 2018SSRF operation s
4、tatus(2017)Scheduled/hrsAccomplished/hrsAvailabilityMTBFMDT20092215209494.6%28.31.65201040033829.195.3%40.441.8420114477437097.6%55.31.57201246104535.498.469.81.19201347274638.798.1%70.31.36201446924624.598.6%81.11.220154634455698.3%79.91.5420164606453097%45.761.4520174246415297.8%54.61.25Hongtao Ho
5、u,TTC workshop,RIKEN,Japan,June 2018Hongtao Hou,TTC workshop,RIKEN,Japan,June 2018SLS:passiveFEmax=2.4 GeV Ibeam=400 mA 1 Nb/Cu HCs fharm=3 fRF 3 times length 2.2 times lifetime Elettra:passiveFEmax=2.0 GeV Ibeam=320 mA 1 Nb/Cu HCs fharm=3 fRF 3 times length 3.5 times lifetime APS-U:passive+FPCFEmax
6、=6.0 GeV Ibeam=200 mA 1 Nb cavity fharm=4 fRF 3 times length 3.5 times lifetime NSLS-II:passive,FEmax=3.0 GeV Ibeam=500 mA F2-cell Nb cavity fharm=3 fRF 2 times lifetime Worldwide SC harmonic cavitiesIn operationUnder developmentHongtao Hou,TTC workshop,RIKEN,Japan,June 2018Contents1.Background2.Des
7、ign Specification3.Harmonic Cryomodule Design4.Control and interlock5.SummaryHongtao Hou,TTC workshop,RIKEN,Japan,June 20182.Design SpecificationFGoal:Lifetime increase factor2，bunch lengthening factor2 Low transient beam loading:R/Q 90 Ohm；Passive cavity,1.5 GHz Q0 1.0 E10 Eacc=10 MV/m(VT)FHigh sta
8、ble and reliable SRF module:high performance niobium cavity,reliable tuner,HOM heavily damped;PLC-based control for cryomodule;FHarmonic cavity voltage control:constant voltage operation mode,digital LLRF,mechanic+pizeo tuner;FInterlock and machine protection system:PLC based,cryomodule monitoring,i
9、nterlock with main rf systemFLimited by installation space available(2 m)and higher harmonic voltage required(1.8 MV),resulting in one module with a double-cell cavity operation at 2.0 K.(low gradient,easier to reach and 2K operation stable)Hongtao Hou,TTC workshop,RIKEN,Japan,June 2018Specification
10、Harmonic systemFBunch lengthening factor:2FBeam lifetime increase factor:2ParameterDescriptionValueEBeam energy3.5 GeVCCircumference432 mIdcDC beam current0.2 0.3 AfrfRF frequency499.654 MHzhHarmonic number720Momentum compaction4.2e-4Energy spread0.001U0Radiation loss per turn1.4 MeVVrfMain rf volta
11、ge4.5 5.4 MVQsNominal synchrotron tune0.0075lNominal rms bunch length3.8 mmVhHarmonic rf voltage1.4 1.8 MVSchematic Diagram of Third Harmonic ModuleTable-1:Parameters of SSRF Storage Ring00.511.526420246Phase(rad)Voltage(MV)66V.tz()V.mz()V.hz()V.xz()20 z()Hongtao Hou,TTC workshop,RIKEN,Japan,June 20
12、18Physics calculation0.20.100.10.2010020030004080120Longitudinal position/mPotential(a.u.)Normalized bunch densitymo_nz()h_nz()z()hz()z 1)、Double rf system：optimal lengthening factor 4Bunch shape lengthenedMomentum acceptanceBunch shape with harmonic voltage01002003004005006007001.822.22.42.62.8Buck
13、et numberLengthening factor01002003004005006007003.844.24.44.64.85Bucket numberlengthening factor010020030040050060070012345Bucket numberLengthenling factor2)、Lengthening effect with different filling pattern：factor 2Long bunch train：500 filling+220 gapShort bunch train：100 filling+44 gaps,5 trains5
14、00 bunches+1 high current bunch(9mA)Hongtao Hou,TTC workshop,RIKEN,Japan,June 2018Contents1.Background2.Design Specification3.Harmonic Cryomodule Design4.SummaryHongtao Hou,TTC workshop,RIKEN,Japan,June 20183.1 Choice of cavity shapeSimilar to 3HC at SLS and ElettraRequired HOM couplers on the pipes
15、 between cellsThe HOM couplers will need cryogenic cooling2-cell wo coupling2-cell wo coupling2-cell wi coupling enlarged pipe2-cell wi coupling fluted pipe2-cell structure with cell couplingHOM propagation by the beam pipe；Fluted beam pipe resulted in a shorter niobium cavityBeam line HOM damper,ou
16、tside the cryomodule,water cooling is possible2-cell with FPCI=300 mA2-cell structure with fundamental couplers,Qext adjustable,can reach optimal lengtheningRequired 47 kW beam power,adding main rf load;L band CW coupler is a challengeCavity shape:2-cell structure,fluted beam pipe for HOM propagatio
17、nHongtao Hou,TTC workshop,RIKEN,Japan,June 20183.2 Cavity simulationRi=40 mm,r_blend=10.0mmCST E-mode simulation)(1.1183.01049.3102.4105.31042.72)/(23493kffIfeERrrbsrsmkIfeERbrv/5.5547.83.0106941097.6105.32)/(2339Instability threshold value of SSRF storage ringEigen mode simulation results show both
18、 monopole modes and dipoles impedance meet SSRF requirementHongtao Hou,TTC workshop,RIKEN,Japan,June 2018Multiphysics-Mechanical simulationNb Properties300 K4 KYoungs modulus1.05e111.26e11Poissons ratio0.380.38density85708570Yield strength(MPa)65.5577.1Tensile strength(MPa)181.3819.1Allowable stress
19、(MPa)43.7234df/dl1.48MHz/mmdf/dp(wo stiffness ring)5.2Hz/mbarCool down2.2MHzTuning 1 MHz0.7mmResults3.2 Niobium cavity simulationHongtao Hou,TTC workshop,RIKEN,Japan,June 20183.3 Cavity simulation with HOM dampers SiC material:=45,tan =0.45 2.0 GHzHongtao Hou,TTC workshop,RIKEN,Japan,June 20183.3 Ca
20、vity simulation with HOM dampersD=80mmD=110mmLoss factor of different thermal transition:fluted type has a lower loss factorDifferent HOM dampers location:small influence on impedanceHongtao Hou,TTC workshop,RIKEN,Japan,June 20183.4 Operation mode considerationOperationFNormal operation：SSRF top-up(
21、250 mA)，3HC constant voltage operation；F3HC trip mode Cryomodule breakdown：warm-up,influence SSRF operation.If keeping 300mA operation,3HC cavity needs to be cooled by cold helium gas or pure N2 cooling；RT parts breakdown：keeps 2.0 K，3HC cavity parked with detuning df=347 kHz，no influence on SSRF op
22、eration；l example:cooling water；l Tuner is important，even located outside cryomodule，tuner problem will influence SSRF operation；2.0K system breakdownl 3HC keeps 4.2K,and parked with df=347 kHz；4.2K cryogenic breakdown：switch to the spare cryogenic systemACB&2K cold box2K Multi-transfer lineCryoplan
23、tHarmonic cryomoduleMain SRF modules&ValveBoxesTest CaveRF HallLocation in tunnelHongtao Hou,TTC workshop,RIKEN,Japan,June 2018Superconducting Cryomodule requirementHOM power:300mA,500 bunches filling pattern,4 mm Hongtao Hou,TTC workshop,RIKEN,Japan,June 2018Taper with ion pump(downstream)Gate-valv
24、eHOMDamperMulti-transfer linesTunerAssemblyHOMDamperGate-valveTaper with ion pump(upstream)Adjustable Module baseNb CavitySlidingJointsCryostatHongtao Hou,TTC workshop,RIKEN,Japan,June 2018FHigh pure fine grain niobium material:RRR300FSurface treatment:mechanical polishing+BCP+HPR+650 annealing+ligh
25、t BCP+120 baking(48 hours)3.5 Niobium cavity fabricationBCP:HF(49%):HNO3(69.5%):H3PO4(85%)=1:1:2Hongtao Hou,TTC workshop,RIKEN,Japan,June 2018FPre-tuning：bead-pullFVertical testing：test dewar,low magnetic filed,2.0 K system，specification:Q0 1E10 10 MV/m 2.0 K Phase lock,data acquisition,Q0Eacc Verti
26、cal test insert:l adjustable input coupler,pumping VT Cryostat:l 2 magnetic shielding(Perm-alloy)l low magnetic field,10 mGauss(h +/-347 kHz(revolution frequency 694 kHz)，decision:+/-500 kHz；ncomponent：tuner arm(1:2)，stepper motor，gear box，piezo and power supply，control unit；FSpecificationn Tuning r
27、ange：+/-500kHzn Resolution：10 HzdffQRIVhcb/*)/(*sin*3.9 State monitor and ready-chain interlockFFunction：temperature,pressure,vacuum,level,and heater controlF PLC-based techniqueFSignal to cryogenic for control：cavity temperature,helium level,pressure in helium vessel,LN2 cooling outlet temperatureB
28、CL01/02BDT03/04BDT01/02BDT05/06BDT07/08BDT09/10BDT11/12BDT13/14BCL03/04BCL05BCL06BCL07BCL08BPT01BPT02BPT03BPT04BPT05BPT06CLTSLake shorePT100Pirani GaugeIon PumpCold Cathode GaugeBCC01BPI01AIP01BCC02BPI01AIP01Hongtao Hou,TTC workshop,RIKEN,Japan,June 2018Interlock:FCavity and cryostat safetyFGate val
29、ve controlFCommunicate with main rf systemFOperation mode switchFCommunicate with EPICSFast interlock signals：kick the beamFQuench;FCavity vacuum;FHelium vessel pressure;Hongtao Hou,TTC workshop,RIKEN,Japan,June 20183.10 LLRF controller:block diagramSSRF third generation LLRFSSRF third generation LL
30、RFHarmonic RF LLRF LO signal boardDown conversion boardTuner control boardTuner control boardHongtao Hou,TTC workshop,RIKEN,Japan,June 20184、summaryRequirement of 3HC for SSRF：Increase beam life time 2；Superconducting 3HC cryomodule：constant voltage2-cell cavity,fluted beam pipe for HOM propagation2K，static loss10 W，dynamic loss 600 W；Interlock and LLRF：LLRF controller：digital IQ,cavity voltage stability+/-1%Interlock:PLC-based，state monitor and interlockThank you for your attention
