0. Comments to the minutes of the ISOLDE Physics Group Meeting of the 26.09.2012:
a. ”Ta:Sa” should read “Ti:Sa” (TEC).
b. Céline Van Beveren came to work with RILIS and windmill setup, not MINIBALL (TEC).
c. Marek is not included in the isolde-house mailing list (MP).
1. Technical news - GPS
a. Small delay of the schedule due to the intervention on the HRS. On Tuesday afternoon the p-scan was done.
b. Beam instabilities and problems with focusing observed on Wednesday. The drifts in the range of 1 mm (on the edge of the measurement precision) reported. The abovementioned effect was neither observed in front of GLM nor in the focal plane of the magnet.
c. Continuation of the collections. Problems with alignment and beam focusing observed, partially due to unusually small samples. Beam lost on Friday for several hours due to a problem with the PS booster.
d. Over the weekend the heating of the target went off, switched to the local operation mode. On Monday the heating PLC was replaced and heating could be put back to remote.
e. On Monday target changed to UC-Ta #482, p-scan and yield check planned for Wednesday.
f. The magnet was found to be misaligned by 4 cm, probably due to not obvious identification of the strong beams (no space for mass marker in this mass range).
2. Technical news – HRS
a. No stable beam still on Tuesday night, available on Wednesday morning.
b. ‘Phantom’ leak on Thursday, pressure at 1e-5 mbar, leak check done, nothing found, but vacuum went down afterwards to 1e-6 mbar.
c. The scanner 482 box got damaged when inspecting the Faraday cup. It was not possible to repair the box, left like that. No deterioration of the vacuum observed.
d. Mass problems with stable-beam tuning to ISOLTRAP on Wednesday and Thursday nights. Wednesday: RILIS did the scan of mass 205, at the end of the scan the beam partially lost before the takeover by ISOLTRAP. The ISOLTRAP team, after spending the whole night tuning the stable beam, found it 1 cm below the centre of the beam-line where it leaves the first separator.
f. The transmission through the cooler was 10% for U, in spite of correct values for K. The usual procedure relaying on scaling the ISCOOL radiofrequency between masses did not work. This was probably due to problems with the gas as an ISCOOL turbopump had problems (see point g. below).
g. The turbo pump located close to the cooler broke down. Not sure when it happen (probably Wednesday evening during the RILIS scan). This affected the pressure in the cooler explaining also the problem of the beam positioning observed by ISOLTRAP.
h. Friday onwards the beam taken to LA1 and ISOLTRAP. The transmission through the cooler after adjusting it to U was 75%.
i. Target heating lost on Wednesday morning, switched to local control. An open question remains if the ramping cards not only solve, but also trigger the problem.
3. Technical news - REX and RILIS
a. RILIS is switching to Ag, spectroscopic studies of At took place until now.
4. Other technical news
a. A water leak was found in the REX RF room and old ISOLDE entrance. The leak from the roof will be patched as soon as possible. A thorough repair preventing REX operation will take place in LS1.
b. A migration to INCA control software is scheduled for Monday the 8th.
5. Physics and schedule
a. Due to several interventions both the LA1 experiment using the windmill and ISOLTRAP lost part of their beam-time. The experiments were studying the hyperfine structure of At isotopes. The obtained results suggest a presence of shape coexistence in 217At and 218At.
b. The rate of At isotopes was smaller by a factor of 3-20 than observed in the past. In the last hours of measurement the rate of 217At increased by factor of 100, which brought it closer to previous yields. The cause of the sudden change is under investigation.
c. ISOLTRAP made an attempt to measure the n-rich 220At isotope (2 shifts). Due to a high Fr contamination observed, the team decided to focus on p-rich 197,198At measuring the mass of the ground and isomeric states for those isotopes.
d. On GLM and GHM six groups (3 from biophysics and 3 from solid state physics) were making collections. The planned experimental programme was found to be very demanding due to the need of going through a long pumping cycle (2-3h) while exchanging samples. First time a Cd beam was used for biophysics at ISOLDE, the observed yields were higher by factor 20 than expected. For future measurements it is planned to decouple both experimental programmes, using GLM for biophysics and GHM for solid state.
e. proton-sharing worked very well, however, because – as expected – only 0.2uA p current was used with the molten target.
f. Not sure if the tape station works correctly. Sudden changes of the observed activity even by three orders of magnitude could suggest that the positioning of the collected source in the detection setup is not well reproducible.
g. CRIS is taking the stable beam on Wednesday and will continue whenever the central beamline is available.
6. AOB
a. The “Karlsruher Nuklidkarte (8. Auflage, 2012)” just arrived. Various versions are available.
b. Reminder: the crane will not be available in week 42.
c. The second circular for EMIS conference in Japan (02.12-07.12.2012) was announced.
d. The ISOLDE workshop and User meeting will take place on 17.12-19.12.2012.
e. The defense of Monika’s PhD is scheduled on 14.12.2012 in Copenhagen. An earlier talk will be given at ISOLDE on 07.12.2012.
f. Please be reasonable when calling people at unusual time – in particular when they cannot really help. Not urgent information about the present status of the experiment can be send by e-mail.
g. The documentary photographer Andy Paul is preparing a photo book about people working at CERN. In the next weeks he is willing to spend one day in the ISOLDE hall, please do not feel disturbed by his presence. As he mentioned “the best for me is just when you ignore me”.
Minutes by jk