Minutes of the 93rd Machine-Time Committee Meeting
Date and time: November 17, 2015; 15:00–16:35
Place: RIBF Bldg., Room 203
Attendees: Sakai a (Chair), En’yo a, †, Abe a, Fukunishi a, Kamigaito a, Kase a, Kubo a, Morimoto a, Okuno a,Sakurai a, Shimoura b, Ueno a, Uesaka a, Uwamino a, Wakasugi a, Yamaguchi b, Imai d, †, Haba a, †,Motobayashi a, †, K. Yoshida a, † , Otsu a, †, Tanaka a, †, A. Yoshida a, †,Hirayama c (in lieu of Miyatake), Imao a, †, Satou a, †, Isobe a, †, Sonoda a, †, Yokkaichi a, †, Yonedaa
Absent: Miyatake c, Morita a, †, Motobayashi a, †, Kishimoto a, †a

RNC / b CNS / c KEK / d RIBF-UEC / † Observer(in random order)

Reports
1.

Current Status of the Machine Time Operation (Yoneda)
The current status of the machine time operation was reported. After the last MT committee meeting, anImPACT experiment and two PAC-approved experiments were conducted using the 238U beam. Due toRF troubles etc., the MT schedule has been changed as follows. The 238U MT was terminated due to theion source trouble on November 14.
(before change)

2.

(after change)

ImPACT15-01(SAKURAI)

9am, 21Oct – 9pm, 31Oct

9am, 21Oct – 9am, 3Nov

NP1412-RIBF124R1-01(Ichikawa)

9pm, 3Nov – 9pm, 9Nov

9am, 4Nov – 9am, 10Nov

NP1306-RIBF99-01(Daugas)

9pm, 9Nov – 9am, 13Nov

9am, 10Nov – 5:40am, 14Nov

Report on the RIBF Accelerator Operation（Fukunishi）
A status report was made concerning the beam provided to the SRC-BigRIPS experiments. The 238U
beam was provided to the SRC-BigRIPS experiments from October 19 to November 14. The beam
intensity reached 48.8pnA, thanks to the big gain achieved by the improvement of the RRC vacuum. Thebeam availability was 88.3%, and the troubles related to RF occurred frequently. At the end, there was avacuum leak on the ion source which took a long time to recover, thus the beam delivery had to bediscontinued. Now the beam tuning is ongoing to provide the 48Ca beam to SRC-BigRIPS fromNovember 18 as scheduled, while the RILAC RFQ vacuum tube was exchanged to deal with thebreakdown.

3.

Report on Accelerator Machine Study (Imao)
A report was made concerning the accelerator machine study. While the machine study was aimed atinvestigating causal relationship between the light emission of the helium gas stripper and suppression oftemperature increase during the beam irradiation, the correlation of light signal in with the beam cycle
was not observed this time. In the next trial, the detector will be placed closer. After the next
measurement, this machine study can be performed in a parasite mode.

4.

Report on BigRIPS Machine Study (Satou)
A report was made concerning the BigRIPS machine study performed on November 4. This machine
study was aimed at checking the tolerability of PPACs against high count rates. Since there was noproblem with a short-time irradiation, the tolerance for a long-time irradiation was checked this time. The
high voltage was tuned carefully not to be too high, as was done in the last test, and the PPACs wereirradiated with a secondary beam with isotopes around 132Sn. There was no trip observed after 70-minutes
irradiation with 600kcps, and 60-minutes irradiation with 1Mcps. The detection efficiency changed
depending on the rate, but recovered when the rate became low. This suggests that the detector was notdamaged with the discharge. The electric circuit which lowers the voltage when there is discharge
worked as expected. After this circuit is triggered, the detector does not work for approximately 16
minutes.

5.

Report on SAMURAI-TPC machine study (Isobe)
A report was made concerning the SAMURAI-TPC machine study. The basic performance ofSAMURAI-TPC was checked by placing the detector downstream of SAMURAI. The gating grid which
is triggered by a heavy ion injection worked as expected. The data was taken by using the GET circuits
and the 1200ch flash ADC with the noise level suppressed to about 80% of the MIP signal level, andsome reaction events with multiple particles generated in the collision on an aluminum plate wereobserved. The trigger test with detectors out of SAMURAI-TPC was also completed without anyproblem. The next test will be made with the detector in the magnetic field.

6.

Report on PALIS machine study (Sonoda)
A report was made concerning the PALIS machine study. PALIS is an experimental device which
captures gas cell particles abandoned on the F2 slits, and measures their physics quantities without
disturbing the main beam in the BigRIPS. This was the first performance test with a beam. Theinterference with the main beam was checked by moving the gas cell, and it was confirmed that there wasalmost no beam loss with ±5cm away from the central trajectory. Although there was a concern that thelaser used at PALIS might cause significant noise signal in the detectors downstream, it was found that
there was no such problem. The ion extraction with the RF ion guide did not succeed, but an effect wasseen with the extraction with an electrode, and the decay curves with the unstable Cu isotopes wereobserved. In the next test, the ion extraction with the ion guide which broke down during the test will betested and particle bunching will also be tested.

7.

Report on Radiation Measurement during 238U Beam Time (Tanaka)
A report was made concerning the radiation measurement during the 238U beam time. The radiation level
was measured when a 50µA 238U beam was stopped in a Faraday cup at the exit of SRC (G01). It wasconfirmed that the radiation level was still lower than the dose limitation set for the boundary of theradiation-controlled area, but a request has been made that the beam with intensity larger than 50µA notbe allowed to be stopped in the Faraday cup until the radiation shield is fortified.
8.

Status of PAC Meetings （Yoneda）
・ 16th NP-PAC:（12/3 – 5）
34 proposals have been submitted. The total requested beam time is 382 days. The breakdown is asfollows:
low-energy branch: 12 proposals 174days：GARIS 4proposals 89.5 days,
CRIB 5 proposals 55.5 days, KISS 3 proposal 29 days
high-energy branch: 22 proposals 208days：BigRIPS/ZDS 11proposals 101days,SHARAQ 1 proposal 15days, SAMURAI 9 proposals 81days,
PSP（report & next plan）1 proposal 11days
・ 12th ML-PAC：
The schedule is under consideration based on the backlog of experiments using the low-energy
facility and status of RAL experiments.
・ 4th In-PAC：to be held until the end of this year.

Topics discussed
1. Approval of Minutes of Previous Meeting (Sakai)
2. Request of Parasite Experiment (Yokkaichi)
A parasite experiment at AVF was requested. A GEM detector with CsI vapor-deposited photocathode will
be placed in an AVF room during an RI-production experiment, and its performance under high-dose
neutron radiation will be checked. During the RI-production experiment, the radiation level is about 40
mSv/h, and is suitable for the test.
After deliberation, the request was approved as proposed.
3. FY2015 First Half SRC-BigRIPS Official Beam Time (Yoneda)
Details of the lengths of the SRC-BigRIPS experiments performed from March to June in 2015 werepresented. After discussions, the official BTs provided from the facility to each experimental program
were set as follows:
NP1406-RIBF126(E.Sahin) 5 days
NP1306-RIBF98R1(A.Jungclaus) 3 days
NP1312-RIBF118R1(P.Doornenbal&A.Obertelli) 9 days
NP1106-RIBF65(K.Sekiguchi) 4 days
NP1112-RIBF94(W.Korten&P.Doornenbal) 6 days
NP0702-RIBF4R1(B.Blank) 5 days
NP1112-RIBF82(B.Rubio and others) 5 days
NP1112-RIBF93(A.Algora and others) 5 days

4. Next Meetings
・The next meeting will be held on Tuesday, December 15, 2015, at 3pm.

・The meeting after the next will be held on Tuesday, January 19, 2016, at 3pm.