Possible improvement of the CLIC accelerating structure. From CLIC_G to CLIC_K.

Transcription

1 Possible improvement of the CLIC accelerating structure. From CLIC_G to CLIC_K Alexej Grudiev CERN

2 Outline Current CLIC accelerating structure: CLIC_G Compact coupler design with damping Comparison of rounded and not rounded cell geometry New type of waveguide damping for lower pulsed surface heating a ridged waveguide damping Constant Sc structure as an optimally tapered accelerating structure

3 Structure C L I C CLIC_G Parameters of CLIC_G Frequency: f [GHz] 12 Average iris radius/wavelength: <a>/ 0.11 Input/Output iris radii: a 1,2 [mm] 3.15, 2.35 Input/Output iris thickness: d 1,2 [mm] 1.67, 1.00 Group velocity: v (1,2) g /c [%] 1.66, 0.83 N. of reg. cells, str. length: N c, l [mm] 24, 229 Bunch separation: N s [rf cycles] 6 Luminosity per bunch X-ing: L b [m -2 ] Bunch population: N Number of bunches in a train: N b 312 Filling time, rise time: f, r [ns] 62.9, 22.4 Pulse length: p [ns] Input power: P in [MW] 63.8 P in /Ct P p 1/3 [MW/mm ns 1/3 ] 18 Max. surface field: E max surf [MV/m] 245 Max. temperature rise: T max [K] 53 Efficiency: [%] 27.7 Figure of merit: L b /N [a.u.] 9.1

4 WDS cell geometry Waveguide Damped Structure (WDS) 2 cells Minimize E-field Minimize H-field Provide good HOM damping Provide good vacuum pumping

5 TD24_vg1.8_disk

6 TD24_vg1.8_disk transverse wake 10 3 CLIC-G TD24-vg1.8-disk 10 2 W x [V/pC/mm/m] s [m]

7 Structure CLIC_G TD24 Frequency: f [GHz] Av. iris radius/wavelength: <a>/ In/Output iris radii: a 1,2 [mm] 3.15, , 2.35 In/Output iris thickness: d 1,2 [mm] 1.67, , 1.00 Group velocity: v g (1,2) /c [%] 1.66, , 0.81 N. of reg. cells, str. length: N c, l [mm] 24, , 229 Bunch separation: N s [rf cycles] 6 6 Lumi. per bunch X-ing: L b [m -2 ] Bunch population: N Number of bunches in a train: N b Filling time, rise time: f, r [ns] 62.9, , 23.1 Pulse length: p [ns] Input power: P in [MW] P in /Ct P p 1/3 [MW/mm ns 1/3 ] S c max [MW/mm 2 ] Max. surface field: E surf max [MV/m] Max. temperature rise: T max [K] Efficiency: [%] Figure of merit: L b /N [a.u.] Parameters of TD24_vg1.8_disk Parameters assuming coupler overhead P [MW] (black), E s (green), E a (red) [MV/m], T [K] (blue), S c *50 [MW/mm 2 ] (magenta Parameters of unloaded (deshed) and loaded (solid) structure load P in = 66.0 MW, load Pout = 11.4 MW Eff = 26.5 % t r = 23.1 ns, t f = 64.2 ns, t p = ns iris number

8 Electric field coupler

9 Magnetic field coupler with damping compact coupler (CC) Courtesy of R. Zennaro

10 P [MW] (black), E s (green), E a (red) [MV/m], T [K] (blue), S c *50 [MW/mm 2 ] (magenta C L I C Parameters of unloaded (deshed) and loaded (solid) structure CLIC_G load P in = 63.8 MW, load Pout = 11.9 MW Eff = 27.7 % t r = 22.4 ns, t f = 62.9 ns, t p = ns iris number CLIC_G + compact coupler P [MW] (black), E s (green), E a (red) [MV/m], T [K] (blue), S c *50 [MW/mm 2 ] (magenta Parameters of unloaded (deshed) and loaded (solid) structure CLIC_GCC load P in = 59.8 MW, load Pout = 10.0 MW Eff = 28.8 % t r = 22.4 ns, t f = 64.7 ns, t p = ns iris number Prototype is under design

11 CLIC_G rounded idw = 8.75 mm adw = mm Rounded and non-rounded damped cells TD18 cell CLIC_G non-rounded idw = 8.2 mm adw = 10.1 mm

12 Rectangular waveguide Ridged waveguide for HOM damping CLIC_GLDT (low T) idw = 7.5 mm adw = 9.25 mm Double-ridged waveguide Ridged waveguide

13 EM field configuration in RWDS C L I C Electromagnetic field configuration on the surface of a Ridged waveguide damped structure (RWDS) cell Electric field Magnetic field Sc

14 Structures with ridged waveguide damping P [MW] (black), E s (green), E a (red) [MV/m], T [K] (blue), S c *50 [MW/mm 2 ] (magenta CLIC_GLDT : a = mm Parameters of unloaded (deshed) and loaded (solid) structure load P in = 61.3 MW, load Pout = 9.9 MW Eff = 28.5 % t r = 21.6 ns, t f = 63.0 ns, t p = ns iris number P [MW] (black), E s (green), E a (red) [MV/m], T [K] (blue), S c *50 [MW/mm 2 ] (magenta CLIC_K : a = mm Parameters of unloaded (deshed) and loaded (solid) structure load P in = 64.6 MW, load Pout = 11.5 MW Eff = 29.5 % t r = 21.6 ns, t f = 58.4 ns, t p = ns iris number

15 10 3 Wake field of proposed structures CLIC-G CLIC-G non-rounded CLIC-GLDT CLIC-K 10 2 W x [V/pC/mm/m] s [m]

16 Transverse impedance CLIC-G CLIC-G non-rounded CLIC-GLDT CLIC-K 10 Z x [kohm/m/mm] f [GHz]

17 Structure CLIC_G CLIC_GCC Parameters of the structures CLIC_GCC non-rounded CLIC_GLDT Frequency: f [GHz] Average iris radius/wavelength: <a>/ CLIC_K Input/Output iris radii: a 1,2 [mm] 3.15, , , , , 2.35 Input/Output iris thickness: d 1,2 [mm] 1.67, , , , , 1.00 Group velocity: v g (1,2) /c [%] 1.66, , , , , 0.86 N. of reg. cells, str. length: N c, l [mm] 24, , , , , 225 Bunch separation: N s [rf cycles] Luminosity per bunch X-ing: L b [m -2 ] Bunch population: N Number of bunches in a train: N b Filling time, rise time: f, r [ns] 62.9, , , , , 21.6 Pulse length: p [ns] Input power: P in [MW] (65.2) P in /Ct P p 1/3 [MW/mm ns 1/3 ] S max c [MW/mm 2 ] Max. surface field: E max surf [MV/m] Max. temperature rise: T max [K] Efficiency: [%] (29.2) Figure of merit: L b /N [a.u.] (95% of Cu conductivity)

18 Proposal for new test structures 1. CLIC_GCC non-rounded: TD25_vg1.7_disk - an optimized version of TD24-type made in standard disk technology the same as TD18-type. 2. CLIC_GLDT: TD25_vg1.7_dLDT structure with ridged waveguide damping 3. CLIC_K: T25_vg2_disk non-damped structure with higher input group velocity and stronger tapering than CLIC_G TD25_vg2_disk damped version

19 RF breakdown constraints (S c ) 1/2 [a.u.] (f P/C) 1/2 [a.u.] Surface Electric Field [MV/m] Structure Number Structure Number Structure Number {200ns, BDR=10-6 bpp/m} ~ {180ns, BDR=3x10-7 bpp/m}