1. Phase reference RF work
Anders Sunesson RF group leader
September 18, 2017

2. An artists impression of ESS

3. Site August 11

4. Overview RF group had a visit by Fritz Caspers from CERN
He met and discussed with members of the RF group
He visited the site and our labs
We did some measurements and analysed a failed high power load (multiple design and material choice errors)
He offered some ideas on actions

5. ESS Linac Layout Low Energy Front end DTL RF Spoke RF Medium beta RF
High beta RF
Spoke cryo-modules
Medium beta cryomodules
High beta cryomodules
DTL tanks

6. Timing and Phase Reference
Phase reference line in tunnel.

7. Phase ref line First design prepared
Prototyping , scaled down version to test
Phase reference signal delivery system
Air pressure system
Temperature control system
Data acquisition, drift calibration, EPICS interface
Several design alternatives MO
20dBm, MHz
20dBm,352.21MHz
~50dBm, MHz
~40dBm, MHz
Temperature controlled within ±0.1°C …
704.42MHz, 1 5/8’’ rigid line
352.21MHz, 1 5/8’’ rigid line

8. Points to consider reference line
Measure the whole reference line with a VNA in time domain to find out reflections, imperfections etc.
Also to find out standing waves
Simulate this?
How much power is really needed? Difficult to calculate a number all can agree on

9. Couplers
Perform measurements on some (2-4) couplers from the delivery to assess variation of parameters like matching, directivity, and coupling
Can the couplers be optimized for both frequencies?
Our answer has been “no”, a compromise is needed
Needs VNA, rigid lines, couplers, good cables
Perform full 4-port to get the full S-matrix
Criticality of alignment
Is it even so that this is needed? Maybe not.

10. Filters
An alternative solution would be to use diplexers, that offer good isolation and low loss. Check out if a customed type could be used
Maybe ask for a quote

11. Other
Dismounting – how to do this if needed

12. Thank you