Optimization of waveguide geometry in the CLICG structures

Optimization of waveguide geometry in the CLIC-G structures Hao Zha 13/08/2014

Geometry of CLIC-G cell Optimized for Independed parameters: -- c magnetic field -- eow=ac/bc -- iw: waveguide opening Optimized for wakefield damping -- w: wavegude width When eow increase: bc iw w ld w /2 /2 45 o Note : In all the next slides, if you see “maximum magnetic field”, the eow should have been optimized! rdw ac=eow*bc b Beam axis c

Compact waveguides • There is safety distance between cells and loads. • Smaller waveguide has shorter safety distance

RF test model for dipole modes • Like wakefield monitor, measure the S-matrix for 4 waveguide port. • Reflection of each port may refer a dipole modes. Port 2 Frequency of first dipole mode Port 1 Port 3 Port 4

Circuit model • Cavity : Transmission line with higher Z 0 • Waveguide: Transmission line with lower Z 0 • Junction: Impedance converter Waveguide N: 1 Cavity Waveguide 1: N’

Compared with Gdfidl Cells with different aperture Cells with different waveguide width

Annoying frequency shift • Test cube resonator + 2 waveguide • Dimension: 20 mm*12 mm Q is almost exactly same But the frequency has a shift Analytical frequency of TE 101 Mode

Study on waveguide geometry Width Opening • Sweep on waveguide width and opening. • Width↓, Q↓, H-field↓, • Opening↓, Q↑, H-field↓,

Optimum waveguide width • Why smaller width have better damping effect: • Impedance match Different waveguide width for middle cell Optimum waveguide width for cells Here is CLIC-G

Sweep on First cell Optimum width = 10. 3 mm

Optimum on width & opening • • Width↓, Q↓, H-field↓, Opening↓, Q↑, H-field↓, Width ↓ and Opening ↓, Q==, H-field↓↓ Contour line of width and opening : Optimum width = 9. 9 mm

Original cell/Optimized width & opening Max-E field (MV/m) Max-H field (KA/m) Max-Sc (MW/mm 2) Vg (%c) R/Q (Mohm/m) Q Original cell Optimized width & opening 202. 4 4. 020 4. 112 1. 661 14615 5559 202. 3 3. 983↓ 4. 105↓ 202. 2 3. 940↓↓ 4. 102↓↓ 1. 684↑ 14822↑ 5618↑ 1. 696↑↑ 14929↑↑ 5655↑↑

Mid cell Optimum width = 9. 7 mm Optimum width = 10 mm

Last cell Optimum width = 9. 5 mm Optimum width = 9. 7 mm

New design for CLIC-G Cells Optimized width & opening width Opening Width opening First 10. 3 mm 8 mm 9. 9 mm 7. 98 mm Middle 10. 0 mm 8 mm 9. 8 mm 7. 94 mm Last 9. 7 mm 8 mm 9. 7 mm 7. 90 mm Original cell Optimized width & opening

Tapered cells (26 regular cell+2 matching cell) Original cell Input power = 63. 1 MW Optimized width Input power = 62. 4 MW ↓ 1. 3 Optimized width & opening Input power = 62. 1 MW ↓ 2. 6

Wakefield results • • Original cell W(s=0. 15 m) [V/p. C/m/mm] Original: 5~6 Optimized width: 1~3 Optimized width & opening: 1~3 Optimized width & opening

Thank you