1 jector Accelerator Readiness Review, 10/31/06 nrik Loos Beam Losses During LCLS Injector Phase-1 Operation Scope of phase 1 operation Operating modes Operating plan for phase 1 Beam power and losses during nominal operation Maximum credible beam Summary of maximum credible beam in injector and linac
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Injector Accelerator Readiness Review, 10/31/06 Henrik Loos 1 Beam Losses During LCLS Injector Phase-1 Operation Scope of phase 1 operation Operating modes.
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Scope of phase 1 operationOperating modesOperating plan for phase 1Beam power and losses during nominal operationMaximum credible beam Summary of maximum credible beam in injector and linac
1. Beam operation from the LCLS injector gun to dump SDMP during LINAC operation, which is located in Sector 21-1. Magnets BX01/BX02 will be locked off.
2. Beam operation from the LCLS injector gun to dump TD11, which is located in sector 21-3. Dump TD11 will be disabled “in”.
The following modes of operation for phase-1 of LCLS injector commissioning have been approved:
Estimated average beam power loss and location along the LCLS in nominal and special tune-up conditions. Power levels set in bold type occur in normal operating conditions. Non-bold entries are special configurations as described in the “note” column.
Table Notes:aa. This loss occurs only when this Faraday cup is inserted (6 MeV, 120 Hz).a. This loss occurs only with beam on the gun spectrometer (6 MeV, 120 Hz).b. This loss occurs only with beam on the injector spectrometer (135 MeV, 120 Hz).c. This is a normal loss due primarily to dark current from gun and injector.d. This loss occurs only with beam on this tune-up dump (120 Hz).
Component Description Area Linac z [m]
LCLS z [m]†
Energy [GeV]
Power [W]
note
FC01 Gun Faraday cup gun 2018.42 - 0.006 3 aa FCG1 Spec. Faraday cup gun 2018.47 - 0.006 1.15 aa GSDMP gun-spec. dump gun 2018.44 - 0.006 1.15 a SDMP inj.-spec. dump SAB 2036.08 - 0.135 16 b BX01 DL1 bend chamber DL1 2032.07 - 0.135 2 c L1X X-band struc. iris BC1 2044.76 - 0.260 0.5 c CE11 energy collimator BC1 2049.34 - 0.250 < 0.1 c TD11 tune-up dump BC1 2058.57 - 0.250 30 d
Nominal and Tune-up Beam Losses from Gun through BC1 ending at TD11
Explosive electron emission occurs from the photocathode if the drive laser intensity exceeds the threshold for plasma production. This emission persists until it has depleted the gun of all its stored energy.
Source in a RF Photocathode Gun is Explosive Electron Emission
The quads between L0-a and L0-b transport 64 MeV electrons so will over-focus MCB electrons causing lost in the L0-b structure. Max power deposited in L0-b is assumed to be the full beam power of 2.2 kW.
The macro pulse 1.2 A is accelerated by L0-a, with beam loading it will have energies between 21 to 76 MeV, with 48 MeV average energy. Average beam power at L0-a exit: (48 MeV)(0.38 C)(120 Hz) 2.2 kW.
The maximum stored energy in the gun is 10 J at 140 MV/m. Beam loading gives 4 MeV energy, therefore the max charge/pulse is (10 J)/(4 MeV) = 2.5microC, at 120 Hz, current is 0.30mA. Studies show 85% lost in GTL, average loss is (4 MeV)(0.30mA) (85%) 1.0 kW.
Quads OFF: this beam could be accelerated by L0-b, with range of 56 to 160 MeV, for the max 62 MW RF power and beam loading. The average energy is (160 MeV+56 MeV)/2 110 MeV, average power is (110 MeV)(0.38 C)(120 Hz) 5.0 kW after L0-b.
DL1 bend off: 5.0 kW lost in and after the spectrometer dipole.
Max energy is 160 MeV and DL1 energy acceptance is 5%, the highest energy with max transmission is (1 - 5%)(160 MeV) 150 MeV. Worst case MCB to main linac is 150 MeV with average power of (13%)(0.38 C)(150 MeV)(120 Hz) 0.9 kW.
Acceleration to 250MeV, MCB ~ 6A*250MeV=1.5kW after L1