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LCLSII Physics Meeting 11/06/2013 Lanfa Wang. 300pC configuration study Reduce emittance growth due to CSR at 100pC. Configuration Example for 300pC. Beam at Gun exit 30A, The solutions of Fernando and Feng are very similar
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LCLSII Physics Meeting 11/06/2013 Lanfa Wang • 300pC configuration study • Reduce emittance growth due to CSR at 100pC LCLSII Physics meeting, 11/06/2013, L. Wang
Configuration Example for 300pC • Beam at Gun exit 30A, The solutions of Fernando and Feng are very similar • There is a strong de-chirp effect at 300pC due to the wake field at long bypass line. • Tried to keep flat current profile and high peak current >2KA, However the beam has negative energy chirp; Charge =300pC R56@BC1: -35mm R56@BC2: -51mm Phase L1: -27.8 Phase L2: -25.0 Phase L3: 0 Phase of Linearizer: -165 Voltage of Linearizer: 68MV LCLSII Physics meeting, 11/06/2013, L. Wang
300pC with BC3 • To overcome the strong de-chirper effect of the wake field along the long by pass line, we may add 3rd BCs after Linac 3. • Need find solution which has small R56@BC3 to reduce the CSR effect. LCLSII Physics meeting, 11/06/2013, L. Wang
Example of 100pC 100pC 12A peak current Slice emittance 0.25 mm-mrad Charge =100pC R56@BC1=-55mm R56@BC2=-60mm L1 phase =-21 degree L2 phase =-21 degree L3 phase =-0 degree 3rd HC phase =-165 degree L1voltage =219.6 MV L2 voltage =1.447GV 3rdHC Voltage=55MV LCLSII Physics meeting, 11/06/2013, L. Wang
emittance growth due to CSR, 100pC, Nominal The major contribution of the emittance growth is from the tail part of beam LCLSII Physics meeting, 11/06/2013, L. Wang
Minimization of projected emittance growth due to CSR(by increasing L2 Phase and reducing R56@BC2) • Significantly reduce the emittance growth (comparing nominal configuration, 1um at the end) • Assume that the positive energy chirp can be removed using de-chirper Charge =100pC R56@BC1=-55mm R56@BC2=-58.8mm L1 phase =-21 degree L2 phase =-30 degree L3 phase =-0 degree 3rd HC phase =-165 degree L1voltage =219.6 MV L2 voltage =1.56GV 3rdHC Voltage=55MV LCLSII Physics meeting, 11/06/2013, L. Wang