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

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

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

4. 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 1 Port 2 Port 4 Port 3 Frequency of first dipole mode

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

6. Compared with Gdfidl Cells with different apertureCells with different waveguide width

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

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

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

10. Sweep on First cell Optimum width = 10.3mm

11. 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 = 9.9mm

12. Original cell/Optimized width/Optimized width & opening Original cellOptimized widthOptimized width & opening Max-E field (MV/m) 202.4 202.3202.2 Max-H field (KA/m) 4.020 3.983↓3.940↓↓ Max-Sc (MW/mm2) 4.112 4.105↓4.102↓↓ Vg (%c) 1.6611.684↑1.696↑↑ R/Q (Mohm/m) 1461514822↑14929↑↑ Q 55595618↑5655↑↑

13. Mid cell Optimum width = 10mm Optimum width = 9.7mm

14. Last cell Optimum width = 9.7mm Optimum width = 9.5mm

15. New design for CLIC-G CellsOptimized widthOptimized width & opening widthOpeningWidthopening First10.3mm8mm9.9mm7.98mm Middle10.0mm8mm9.8mm7.94mm Last9.7mm8mm9.7mm7.90mm Original cellOptimized widthOptimized width & opening

16. Tapered cells (26 regular cell+2matching cell) Original cell Input power = 63.1 MW Optimized width Input power = 62.4 MW Optimized width & opening Input power = 62.1 MW ↓1.3↓2.6

17. Wakefield results W(s=0.15m) [V/pC/m/mm] Original: 5~6 Optimized width: 1~3 Optimized width & opening: 1~3 Original cell Optimized width Optimized width & opening

18. Thank you