Choose timezone
Your profile timezone:
4th meeting: Status of Copper testing and irradiation plans
→
Europe/Zurich
Present: Ruth, Walter, Giulia, Sergio, Suitbert, Alexej
Ruth: Pair of copper electrodes is installed into the pulsed DC test as soon as they came out the oven. the surface state is better now. The testing will start in a few days. The initial conditioning parameters will be as close to the L4-RFQ conditioning (35 MV/m, 250us) as possible. the the pulse length will be increased to the one used in operation ~900us.
Sergio reported that fabrication of the electrode holder is under way to be finished by the end of July.
Giulia reported the feedback from the WP11 on the design of electrode holder for the H- source test stand. Main comments is that any manipulation/installation of the electrodes would require breaking the vacuum. It was proposed to look into integrating a valve between the solenoid and the holder. This valve would then stay on the solenoid flange and keep source under vacuum when exchanging/manipulating irradiation setup or putting back RFQ-box.
Giulia will confirm the available length and aperture for the valve integration.
Giulia reported on the H- source test stand schedule. According to the present schedule, there is no available time slot for electrode irradiation this year. The schedule for the next year is not fixed yet and we can probably get an irradiation slot at the beginning of 2021. It has been clarified that for the first irradiation of one copper electode the time slot could be rather short, the same as for the 'collimator test', few days.
Giulia will double check if this short slot of few days could be still possible this year.
Alexej reported that he had a initial discussion with Richard S. about potential use of Linac2 proton source for the irradiation of electrodes. Richard was rather positive and he will look into what is necessary to put it back into operation. This will need further discussion with Richard and with WP11 on the organization of the activity.
Sergio presented a study on the hydrogen diffusion in Nb, modelling a 1-mm thick Nb sample irradiated over 1 cm2 with the full dose rate available from the source (collimator-like experiment). Hydrogen quickly diffuses (within 1000 s at room temperature) from the surface into the bulk, so no local blistering is expected, contrary to copper. Above a certain concentration, corresponding to about one month of full rate irradiation, formation of hydrides can be expected.
Note added after the meeting: when H concentration in Nb reaches 1% (below the hydrides formation threshold), the equilibrium pressure will be such that a typical turbopump (100 l/s) will be able to remove the outgassed H with the same rate than the implantation rate from the source, thus setting an equilibrium.
There are minutes attached to this event.
Show them.