Minutes from the ISOLDE Physics Group meeting on October 1, 2014
No comments on the minutes for the meetings of September 18th and 24th.
Technical news
GPS
- The prototype target to develop Boron beams was installed on Friday (investigated with ISOLDE tape station and ISOLTRAP).
- Extraction method is based on volatile molecules, by injecting SF6.
- Activity consistent with Boron in atomic form was observed, but not as molecules. Improving extraction in its molecular forms is being investigated.
- When changing the GPS magnet to another mass, the beam moves up to +/- 3mm in SC483 depending if the previous set mass was higher or lower.
- The effect was observed in mass range between 8 and 50.
- Temporary solution is to always approach the mass of interest from the same direction.
- FC490 readout has no more 10-s spikes. The fluctuations were caused by an overflow of the middleware software.
- The Ta target for 11Li was changed Wednesday afternoon after the HRS intervention. Stable beam tuning on Thursday; proton scan, yield tests and RILIS setup on Friday.
- Information about the T1/2 gates was asked by users
- There is not jitter in the T1 signal anymore. This was fixed during the 2012 redesign.
- The master beamgate window that controls the voltage ramp up presently opens 4 ms after the proton impact. Nominal time is 6 ms, in order to make sure the ramp up of voltage is finished, relevant heavy masses. For 11Li it’ll be shortened to 1-2 ms. Because of 11Li short half-life of 8 ms opening the gate early helps increasing the yield. Previous measurements show that by using this short gate the observed yield is limited only by the target release time.
HRS
- HRS target unclamping problem: during the intervention on Monday the old target was found unclamped. The reason is most probably that on Monday the piston pressure was set to 10 bar, while it was 8.5 bar before the weekend.
- The problem is now thought to come from grind in the in-house-designed piston that drives the target platform and finishes the clamping. As it seems to be a design error the pistons for both HRS and GPS will be exchanged.
- During Wednesday’s intervention the piston will be used with 6 bar, the nominal pressure, before being removed for closer inspection in class A laboratory.
- The substitute pistons are commercially available. They come with rubber O-rings, which do not perform well in high radiation areas. Four such pistons are expected to be delivered next week.
- The new piston on HRS will be installed asap and on GPS - after the 11Li run.
- The HRS magnet cycling reliability (which seems to be high at the moment) is going to be studied further by the person that designed the new software.
RILIS: Two pump lasers for Ti:Sa lasers are presently broken. The replacement parts will be delivered in 4 weeks. A spare laser is operational, although it shows lower performance.
Miscellanea
- Discussions with PH and space managers are ongoing concerning the user of B275, once B508 is finished. Maria and Magda have collected the ISOLDE-users requirements for space.
IS525 at LA1
- The IS525 experiment will measure the energy of neutrons emitted in the beta decay of 11Li
- Main aim is to measure the energy of the two neutrons in the 9Be+2n channel in coincidence, in order to elucidate the decay mechanism.
- In addition, it aims to improve the level scheme of single neutron emission populating 10Be thanks to the increased beam intensity, efficiency and resolution, compared to previous measurement by Hirayama and collaborators at TRIUMF.
- The plastic/Cadmium wall (3x3 m2) that used to be placed next to the GLM/GHM is missing. It was used to shield prompt neutrons coming from the proton impact on target. Please contact Miguel if you know its location.
- The valves at LA1 and LA2 for venting user chambers with gaseous N2 are currently not connected to the control system. Magda is following it with the vacuum team.
The next meeting will take place at the same time Wednesday next week (2pm, 8th October 2014)
Minutes taken by MMF