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Wakefield suppression in the CLIC main accelerating structures. Vasim Khan & Roger Jones. Wakefield suppression in CLIC main linacs. We are looking into alternative scheme in order to suppress the wakefield in the main accelerating structures:
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Wakefield suppression in the CLIC main accelerating structures Vasim Khan & Roger Jones
Wakefield suppression in CLIC main linacs • We are looking into alternative scheme in order to suppress the wakefield in the main accelerating structures: • 1) Detuning the first dipole band by forcing the cell parameters to have Gaussian spread in the frequencies • 2) Considering the moderate damping Q~500
CLIC_G structure Cell parameters of a modified CLIC_G structure: Gaussian distribution Uncoupled values: <a>/λ=0.11 ∆f = 0.82 GHz ∆f = 3σ i.e.(σ=0.27 GHz) ∆f/favg= 4.5 % Then we calculate the coupled mode frequencies and kicks using double band circuit model
Modified CLIC_G structure Coupled Uncoupled Coupled Uncoupled Undamped Undamped Q = 500 Q = 500 Envelope Wake-field Amplitude Wake-field
Zero crossing of wake-field The oscillations in the wake-field amplitude are due to a corresponding sin term. We adjust the mode frequencies to force the bunches to be located at the zero crossing in the wake-field. We adjust the zero crossing by systematically shifting the cell parameters (aperture and cavity radius). Cell parameters of seven cells of CLIC_ZC structure having Gaussian distribution Uncoupled values: <a>/λ=0.102 ∆f = 0.83 GHz ∆f = 3σ i.e.(σ=0.27 GHz) ∆f/favg= 4.56% ∆a1=160µm and ∆a24= 220µm. The first trailing bunch is at 73% of the peak value (Wmax=180 V/pC/mm/m). ∆f=110 MHz. There is a considerable difference in the actual wake-field experienced by the bunch, which is 1.7 % of peak value which was otherwise 27%.
CLIC_ZC structure Coupled Uncoupled Coupled Uncoupled Undamped Undamped Q = 500 Q = 500 Envelope Wake-field Amplitude Wake-field
Interleaved cells & SRMS Q = 500 Q = 500 192 cells 24 cells