There was a leak in the Solid Attenuator that increased on Saturday morning when SPB moved the arm number 4 (see last entry ID 236).

We were lucky that a balance developed between the leak and the pumping of the ion pumps, so by setting the setpoints of the three most affected ionpumps to 5x10-5 mbar we could survive the weekend and save the beamtime. 

On Monday Maik and I then entered the tunnel to fix the leak. The need of breaking the interlock to bring a dewar and a pumpcart was already discussed on Saturday/Sunday with the PRC (Jan Grünert) and BKR. So Maik and I could enter on Monday afternoon at around 13:20. We found out that the bellow of the arm number 4 is the leaky one which we removed then and put a blind flange. So the XTD 2 solid attenuator has two removed arms now (see photo).

After about half an hour of pumping both ion pumps on the Solid Attenuator were already in the good 10-6 mbar range. We also set back the setpoint of the three pumps P10160I, P10170I and P10180I to the default value 5x10-6 mbar and put the bridge for the end switch on the connector (see picture). The whole work including cleanup in the tunnel could be finished around 19:15 and the tunnel search crew could then set the interlock back.

So the acute problem with the leak could be solved for first now, but there was no time for the activation of the NEC pump. This should be kept in mind for the next shutdown, when we hopefully have spare parts and can anyway replace the arms number 4 and 5. 

We packed the removed actuator and diamond plate in foil and they are next to the radiation protection release box now and waiting for release (see photo). Email was sent to radiation protection officer.

Thanks to Maik for help and a nice working time yesterday and to Michaela for helping us to bring all the things to the XHE3 shaft building! Thanks also to Raul for talking to BKR as PRC and arranging the final tunnel access appointment!