during HV-tests on the installed XGMs, our DESY colleagues from Kai Tiedtkes team have found an issue with one of the electrodes / resistors inside one XGM vacuum chamber at XTD2.

 

Roughly, we know the following:

1)      If not repaired, we would lose at least the capability of monitoring shot-to-shot horizontal beam position at this XGM location. This is a lower-priority info.

2)      However, it’s not yet fully tested if other functionalities could be affected. In case the absolute calibrated intensity info is affected, then clearly we would have to repair.

3)      Since the cause of the resistor-irregularity is not understood, there is a risk to damage the other (operational) remaining resistors in the other chambers of the same XGM.

 

It is not yet fully clear 

a)      what is the cause for the irregular behavior (it concerns a resistor inside vacuum which dramatically changed its resistance, which apparently possibly might happen even during a correct dry-nitrogen venting),

b)      the entire consequences for operation with this XGM

c)       the effort/details of a potential repair (could include up to removing one of the four chambers off the girder out of the tunnel into a lab, certainly needs re-survey)

d)      if another XGM chamber is affected (so far tested 2 of 6).

 

The DESY colleagues are running various tests with us on the XGMs, also extending to all the other XGMs, to get answers to the above questions in order to allow a decision on “repair/not repair”. 

 

Since this concerns the internals of the high-prio XGM in XTD2, we could ask Kai Tiedtke to give us his brief 10min report and recommendation in the tomorrow SASE1Readiness Meeting. Should we request his presence / will you add him to the agenda ?

 

Best regards,

Jan

________________________________________

Dr. Jan Grünert

Group Leader X-ray Photon Diagnostics (WP74)

European XFEL GmbH

Holzkoppel