Status of work on the HOM coupler. 2 nd Harmonic cavity Meeting 11/II-2016 Thermal analyses with shims (Y.Terechkine). Gennady Romanov On behalf of Y.Terechkine

The CST model based on SuperFish geometry from Tan 11/II-2015Gennady Romanov | Status of work on the HOM coupler 2 CST model without planes of symmetry No HOM couplerWith HOM coupler F, MHz Dipole modes π/ Dipole modes Dipole modes

Comparison CST FD with SF + Transmition model 11/II-2015Gennady Romanov | Status of work on the HOM coupler3 50 Ω

Further comparison CST FD with SF + Transmition model 11/II-2015Gennady Romanov | Status of work on the HOM coupler4 50 Ω Model from SuperFish Operating mode, μ = 3.5 Drop of impedance -27% SF: –11% (from 49.4 kΩ to 44 kΩ) HOM1 Drop of impedance -93% SF: –99.3% (from 228 kΩ to 1.6 kΩ) Calculation of R equiv =50∙(V g /V d ) 2 Ω ModeCST EMSF Operating4.22e5≈4e5 HOM1378≈180 No HOM cavity With HOM cavity

Toward reality 11/II-2015Gennady Romanov | Status of work on the HOM coupler5 Load gap increased from 0.25 cm to 1 cm. All diameters are made equal. Wall thickness of the drift tube is 1 cm instead of 0.2 cm HOM1: Z11= Ω without HOM cavity, Z11= Ω with HOM cavity Drop = -96% R equiv. = 868 Ω with HOM cavity Operating: Z11= Ω without HOM cavity, Z11= Ω with HOM cavity Drop = - 29% R equiv. = 7.96e5 Ω with HOM cavity

Magnetic shims 11/II-2015Gennady Romanov | Status of work on the HOM coupler6 Material of shim – Al800 Thickness – 3.5 mm Inner radius – 115 mm Outer radius – 148 mm Fillet radii – 2.5 mm H min has increased from ~33 Oe to ~50 Oe Ferrite disks: Upper 16 mm Others 21 mm Total length 100 mm

Calculations of thermal losses 11/II-2015Gennady Romanov | Status of work on the HOM coupler7 RF losses distribution, W/cm 3, 76 MHzThermal losses distribution, W/cm 3, averaged over block volumes and over time, i.e. this is an input for the thermal model. Total thermal losses = ?

Thermal analyses 11/II-2015Gennady Romanov | Status of work on the HOM coupler8 No shims, no contact between garnet and walls, Max. temp. 56°C With shims, no contact between garnet and walls, max. temp. 49°C With shims, all contacts are there, Max. temp. 44°C

Electric field enhancement 11/II-2015Gennady Romanov | Status of work on the HOM coupler9 40 kV/cm The minimum internal bias magnetic field has increased from 50 to 70.4 Oe. Power losses. Not a problem though Electric field New shape of shim Electric field, Maximum 25 kV/cm Magnetic field Permeability, max is 11.6