Minutes from the ISOLDE Physics Group meeting on October 8, 2014

No comments on the minutes for the meetings of October 1^st .

Technical news

GPS

• Ta target for ¹¹Li production at LA1. A few issues with protons during the run, watchdog, LINAC 2 and magnets in the BTY line. All problems fixed by Saturday night.
• The separator magnet “hysteresis” problem (i.e. the beam was a few mm off when coming from low or high mass) was not observed by the technical or RILIS teams with this target.
  
  • The engineer in charge reports that large steering was required to center the beam and obtain good transmission after the separator. Tim Giles will follow up the problem.
  • Transmission problems have been observed in many GPS targets so far. This point to a possible alignment problem. Users are reminded to keep it in mind when tuning GPS beams.
• There were 2 HV trips at the beginning of the IS525 run. It’s been running stably at 50 kV since.
  
  • Technical team noticed that sometimes after rebooting the HV pulsing mode does not start at first try and HV goes to static mode – this worsens the HV recovery and can break the HV installation.
  •  It is recommended to make sure pulsing mode is engaged to protect the HV platform.
• Scanner SC482 does not work. If all needed parts become available; it will be replaced next Monday.
• RILIS laser position had shifted on Wednesday morning, causing beam 11Li intensity fluctuations. Beam intensity recovered  previous values after RILIS team corrected the shift (50% higher with laser on than off).
• Target change postponed to Monday after the HRS intervention planned for Friday. GLM/GHM collections on Thursday; IS525 extended to run through the weekend.

HRS

• After uncoupling the problematic piston from the target table/platform both the table and the piston moved freely again. This suggests that the rigid coupling of the piston was indeed the problem.
• A new commercial piston has been received. It contains plastic parts, which are not radiation resistant.
  
  • The all-metallic design will not be used again. The coating degraded due to friction in regular operations.
  • As in previous years the commercial pistons will now be removed at the end of the year, every year.
  • The piston will be fitted with a spherical tip to ensure it can be realigned.
  • The intervention to install all parts mentioned is planned for this Friday (update after PG meeting: intervention now planned for Monday 13^th of October).
• CRIS experiment, requiring HRS, will be hopefully scheduled once HRS is fixed.

RILIS                                                  

• The parts required to repair the pumps of the two TiSa lasers will be delivered in 1 month.
• The spare pump laser is currently in use for IS525.

REX-ISOLDE

• Twin-EBIS current increased to 500 mA compared to previous 200 mA at REX-EBIS. This will allow for faster and higher charge breeding at REX, but at the expense of a reduced cathode life.

Miscellanea

• The HRS schedule for the remainder of the year will be released after the status of the piston repair is evaluated post intervention.
• A new pair of cryogenics safety gloves were purchased and are now at the ISOLDE toolbox.

IS525 at LA1

• The IS525 experiment will measure the energy of neutrons emitted in the beta decay of ¹¹Li, both single and double neutron emission.
• As of Wednesday, 10 shifts of ¹¹Li at 1000 cps or higher beta-rate; 3 hours of ⁹Li with 8 ms beam gate (20 000 cps beta-rate) to measure the beta-decay half-life.
• Collected 10 times more statistics than the previous experiment by Hirayama and collaborators.
• 500 two-neutron coincidences observed in the 3 shifts analyzed, after cross-talk filter applied. This corresponds to 50% of the experiment goal in 1/5 of the allotted time.

• COLLAPS laser was mounted in the CRIS laser table in the hall and it is working stable.

IDS

• IDS electrical and LN2 safety checks have been approved and signed by safety department
• The setup is being prepared for ³¹Ar run; Clover frame was turned around; IEM-CSIC chamber and silicon detectors installed;

The next meeting will take place at the same time Thursday next week (2pm, 16^th October 2014) and it will be followed by the seminar of Claes Fahlander on Superheavy research.

Minutes taken by MMF