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

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!

safety distance 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 1 Port 2 Port 4 Port 3 Frequency of first dipole mode

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

Compared with Gdfidl Cells with different apertureCells with different waveguide width

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

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

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

Sweep on First cell Optimum width = 10.3mm

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

Original cell/Optimized width/Optimized width & opening Original cellOptimized widthOptimized width & opening Max-E field (MV/m) Max-H field (KA/m) ↓3.940↓↓ Max-Sc (MW/mm2) ↓4.102↓↓ Vg (%c) ↑1.696↑↑ R/Q (Mohm/m) ↑14929↑↑ Q ↑5655↑↑

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

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

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

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

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

Thank you