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40mm STF2 Coupler Design

Content1. Motivation2. 40mm Design3. “Preliminary” Result by

HFSS4. “Tentative” Conclusion5. Future Plan

This report is made by help from Kako-san and Sakai-san. Kirk

superconducting rf test facilityMotivation

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40mm 60mm

DESY/FNAL Cavity Package KEK Cavity Package

TTF3 Coupler STF2 Coupler

In view of “Plug compatibility”, the use of STF2 coupler should be evaluated for 40mm diameter.

What is the most simple way for this change?

superconducting rf test facilityDesign of 40mm STF2 Coupler

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Only this part should be modified for minimum change!

I used HFSS for this calculation.

superconducting rf test facilityHFSS modeling for each step

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Step 1: only cold partStep 2: full model Step 3: bellows

Bellows are Not included!

superconducting rf test facility

Step 1: Only cold part without bellows

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60 mm 40 mm

1.3 GHz 1.3 GHzS11 S11

The both types has S11 with <-25 dB!

Same structure

superconducting rf test facility

Step 2: Full model without bellows

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60 mm 40 mm

1.3 GHz 1.3 GHzS11 S11

Same structure

The both types has S11 with <-20 dB!

superconducting rf test facility

Step 2: Full model without bellows

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60 mm 40 mm

superconducting rf test facilityStep 3: Evaluation of bellows

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60 mm 40 mm

1.3 GHz (-22 dB) 1.3 GHz (-18 dB)S11 S11

We have to develop the smaller bellows.

Same structure

superconducting rf test facility

It’s no problem in RF performance for 40mm

STF2 coupler!

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“Tentative” Conclusionat least

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Future Plan Mechanical Design for 40mm STF2 Coupler

More important than RF calculation Especially, inner conductor in cold part

Tuning range (1-10 x 106) to be estimated

Lower cost If the cost is higher, it’s no meaning!

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To Do List (Simulation) Cavity-to-Coupler coupling should be

fixed Simulated by HFSS or CST Studio

Full model simulation with Doorknob Simulated by HFSS or CST Studio

Test bench simulation with Waveguide Simulated by HFSS or CST Studio

Multipactoring Simulated by CST Studio or TRACK-3P or OMEGA-3P

Others (?)

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To Do List (Mechanical Design)

Inner Conductor Inner Conductor Bellows in cold

part Doorknob

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Thank you for your attention!

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