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I. Syratchev, structure team meeting, 19.09.2007 Re-circulation Re-visited I. Syratchev
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I. Syratchev, structure team meeting, 19.09.2007 I. Syratchev April 1999 beam Load Ohmic Losses PETS Load Ohmic Losses Power divider beam From PETS, A1 Structure Output, A2 Structure Input, A3 To RF Load, A4 Variable polarized power divider basics Traveling wave with re-circulation Circular waveguide with H11 mode beam RF
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I. Syratchev, structure team meeting, 19.09.2007 Traveling wave (constant impedance) Q-factor 5000 at 12 GHz Traveling wave with re-circulation beam loading PETS (Structure input) PETS Structure input Structure output (Load) Structure output beam loading No beam Tf=31 ns α = 32.92 Loss=0.627 BL=0.234 Pg = 1.35 η norm =1.29 Tf=62 ns α = 28.25 Loss=0.393 BL=0.141 Pg = 1.224 η norm =0.955 # Example 1. Fixed input parameters: - Input power - Input cell - Beam pulse length - Back loop RF power losses – 0.95 We do change: -Structure length (losses and filling time) We do adjust for the max. efficiency for the case with recirculation: - Optimal divider angle - beam current Benchmarked with the similar TW case.
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I. Syratchev, structure team meeting, 19.09.2007 Power gain = 1.35 Power gain = 1.76 # Example 2. T beam injection = 2x T filling T beam injection = 3x T filling # Example 3. Q= 2Q 0 Power gain = 1.43 # Example 4. The beam loading is not optimal. Divider angle is kept constant Power gain = 1.42 BL=BL OPT 0.85 To provide beam loading compensation, the ramp duration and beam injection time were adjusted: T ramp = 1.14 x T filling T injection = 2xT filling + 0.24xTfilling Power into the load 0 BL=BL OPT 1.15 Power gain = 1.265 T ramp = 0.87 x T filling T injection = 2xT filling - 0.22xTfilling Fixed PETS power TW TW + rec. To maintain the same gradient for the 15% reduced current, the PETS power should be reduced: TW: -3.6% TW + rec.: - 8.3%
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I. Syratchev, structure team meeting, 19.09.2007 How to integrate into Alexej’s optimization: # 1. For any given structure the RF transmitting efficiency and filling time are calculated. #2. For the given current, the beam induced RF power at the structure output is defined. #3. The input RF power is then taken from Fig.1 : # 4. Calculate loaded gradient. If result < Target value, STOP! # 5. The RF pulse shape (amplitude) is constructed following: -Linear ramp = 2x Filling time (pp #1) -Flat top # 6. Flat top is adjusted then to the P/C or temperature, or… # 7. For the efficiency calculation: Efficiency = (Beam power/Input power/PR) x (Tflat/(Tflat+2xTfill)) where PR (PETS power reduction) is taken from Fig 2. following calculated losses in a structure (pp.#1) #8. Enjoy! Fig.1 Fig.2 TW versus TW + rec. for the fixed gradient and current. Data for the old 30 GHz CLIC structure called TDS TW TW + rec. TDS
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