Phase reference RF work Anders Sunesson RF group leader www.europeanspallationsource.se September 18, 2017

An artists impression of ESS

Site August 11

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

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

Timing and Phase Reference Phase reference line in tunnel.

Phase ref line First design prepared Prototyping 2015-2016, 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, 704.42MHz 20dBm,352.21MHz ~50dBm, 704.42MHz ~40dBm, 352.21MHz Temperature controlled within ±0.1°C … 704.42MHz, 1 5/8’’ rigid line 352.21MHz, 1 5/8’’ rigid line

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

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.

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

Other Dismounting – how to do this if needed

Thank you