Minutes of the 54th Machine-Time Committee Meeting
Date and time: April 20, 2012; 13:30–15:10
Place: RIBF Bldg., Room 203Attendees: Sakaiaaa, †(Chair), Abe , En’yo

Motobayashia, †, Nishimuraaa, †, OkunobWakasugi , Yamaguchi , YonedaaAbsent: Sakurai , Yoshidaa, Fukunishi , Habaa, †a, †baaa

a, Kamigaito , Kase , Kubo , Morita ,, Shimoura , Sudac, †, ‡aaa‡

TV Attendee, Ueno , Uesaka , Uwamino ,a, †a, †a

RNC /bCNS /cRIBF-UEC /†Observer /(in random order)
Reports
1.

Status of beam-time operation (Ueno)
The beam times (BTs) were conducted as scheduled last month.

2.

RIBF operation (Fukunishi)
The accelerator status of the delivery of 18O beams from March to April was reported. In the firstseries, where 18O beams were delivered at the energy of E/A = 294 MeV, 95.6 % of the requested BT
was delivered (183.6 hours / 192 hours). In the next series, E/A = 230 MeV, the accelerators wereagain operated very reliably with 95.6 % of the requested BT being delivered (514.5 hours / 536hours).

RRC trouble
It was reported that a vacuum trouble occurred in the RRC cavity at the beginning of the 238U BT in
the Machine-Study (MS) category scheduled immediately following the 18O series. Details of thetrouble are being investigated.

3.

BigRIPS operation (Kubo)

It was reported that the following secondary beams were delivered in the 18O beam series fromMarch to April:–Facility Inspection (Mar.16): 16O–SAMURAI commissioning (Mar.16–23): A/Z=2 cocktails, p, 10-12,14Be, 15B, 10-12, 14-17C–EURICA commissioning#1 (Mar.28–31): 12B, 16N–SHARAQ (Mar.31–Apr.15): CNO cocktails, 8He–EURICA commissioning#2 (Apr.15–18): 14Be+15B, 17B–BigRIPS MS-Exp-12: 14O

During this series, the cryogenic refrigerators equipped with Superconducting Triplet Quadrupolemagnets (STQ) 6, 8 broke down while the one with 13 malfunctioned. The refrigerator of STQ13 isstill working, although its condition is unstable. After replacing two of them with the spares, theBigRIPS team requested the manufacturer to find out the cause of the trouble.

4.

R&D study of the first-stage charge stripper for Kr beam deliveries (Okuno)
The following subjects were investigated in the BT of MS11-1:

Carbon-foil charge stripper
The charge of Kr ion beams should be increased from q = 18+ to 26+ at the first stage (E/A = 2.7MeV) and q = 26+ to 34+ at the second stage (E/A = 46 MeV). In the R&D study, a significant
enhancement of the endurance time of a carbon foil up to as long as 18 hours, was observed byintroducing new beam slits made of tantalum instead of graphite. With this however, a change in thebeam phase was observed at the exit of RILAC. The same problem is expected with a Zn beam. The
stability of the beam transportation should be investigated for the entire cyclotron cascadeacceleration mode.

H2-gas charge stripper
A high charge state, q = 25+, was obtained for Kr utilizing a H2-gas charge stripper. The difference
between the high charge state obtained with a carbon foil is only Δq = 1+. As expected, thesuppression effect of the electron capture process with a low-Z gas was observed, suggesting thefeasibility of the H2-gas charge stripper.

5.

SAMURAI commissioning (Yoneda)
The following subjects were studied in the MS11-10 BT (Mar.16-23):
Secondary-beam transportation: The best transportation mode was determined through themeasurement of effective acceptance and resolutions of the proposed three modes.

Neutron detector array NEBURA: A performance evaluation of NEBURA was carried out throughthe measurement of  rays and neutrons utilizing the 15C+Cu and p+Li reactions. Sufficiently highperformance was confirmed in the measurement.

SAMURAI magnet: Properties of the magnet was studied by measuring eight different particle
trajectories under the three settings of the magnetic field B = 2.0, 2.5, and 3.0 T. A position
resolution of 3 cm and an angular resolution of 14 mrad were obtained.

Entire performance test: The test was performed utilizing the 17C+C and 15C+Pb reactions based on
the invariant mass spectroscopy.

6.

EURICA commissioning (Nishimura)
The performance of the EURICA system was tested twice with 18O beams at E/A = 230 MeV. In the BTof MS11-16 (Mar.28–31), the isomeric state in 16N was immediately identified, where its half-life t1/2 =5.25 μs was accurately measured. An obtained energy resolution of the EURICA Ge detector array was
2–3 keV. Also, the time-stamping data acquisition systems which differed depending on theEURICA/BigRIPS detectors were successfully combined. In the next BT of MS11-17 (Apr.15–18),
further performance test was carried out through the β- measurement with 17B, whose β decay is known
to be followed by the β-delayed neutron emission with up to four neutron multiplicity. The system
performance will be evaluated in detail through the off-line analysis. Preparations for the first EURICA
BT scheduled for June will be completed after i) the check of the efficiency and the fast timing and ii) theinstallation of the Munich’s Si detectors. For the BTs of the 238U beam series scheduled for this autumn
and winter, the readout electronics for the Si detectors will be prepared.

7.

Construction of Rare RI Ring and its influence on the FY2012 BT schedule (Wakasugi)
The relevant infrastructure constructions will be scheduled in the first half of FY2012 which will notaffect the BT operation. The bending magnets of Rare RI Ring will be tentatively placed at theSHARAQ site in August.

The main construction of Rare RI Ring will start from September, where a stage of concrete will befirst constructed from September to November. This work will not affect SHARAQ BTs. SAMURAIBTs, however, cannot be conducted during this period since the north carry-in entrance will beoccupied by this work. The construction of Rare RI Ring on stage will be continued until the end ofFY2012. Since the north carry-in entrance will be used for this work as well from time to time, boththe BT and the construction schedules in the second half of FY2012 should be well arranged andadjusted for their smooth operations.

8.

Dealing with the EURICA-related four proposals, RIBF10, RIBF49R1, RIBF80, and RIBF90(Ueno)The representatives of the aforementioned proposals requested that i) the four experiments should beseparated into two BT slots, RIBF90+RIBF10 (7.5 days + 11 days → 16 days by sharing a part of thedata) and RIBF80+RIBF49R1 (total of 7 days in parallel), although it has been recommended in the PAC
report to incorporate the four programs in one BT slot for an efficient BT use, and that ii) the grade of thecombined BTs should be the same as the grade given at the time of approval even when the four
programs are divided into two. Understanding the difficulty incorporating the four programs due to thedifferences in the BigRIPS setting and in the trigger rate acceptable for each detector configuration, theRNC and CNS directors accepted the requests.

9.

Strategic plan of SHE researches (Sakai)
It was reported that a meeting to discuss a future plan of the SHE researches was held on April 10.

10. Status of PAC meetings (Ueno)

11th NP-PAC (June 18–19): The call-for-proposals has been opened (submission deadline is May 2).



9th ML-PAC: The PAC meeting schedule is being deliberated to be held sometime in June or July. It
would be desirable to set the schedule so as to make it in time for the call for BT scheduling requests
for the second half of FY2012.



3rd In-PAC: The PAC meeting schedule is being considered to be held at the end of June.

Topics discussed
1. Approval of the minutes of the previous meeting (Sakai)
2. Outline of the BT schedule for the second half-year of FY2012 (Sakai)A plan for the beam delivery in the SRC-based experiments in the second half of FY2012 wasdiscussed in which the beams of 238U, 124Xe, and light charged particles are being considered.
Discussions were also made about the some constraints in the BT scheduling such as the constructionof Rare RI Ring, and BTs in the MS category for accelerator developments. The discussions willcontinue.
Nishimura, the EURICA Project Manager, has been assigned as the coordinator of the EURICA BT
series. Based on the above consideration, the total BT of the EURICA series was tentatively set forthe second half of FY2012.

3. Next meetings
The next meeting will be held on Friday, May 18, 2012, at 13:30

The meeting after the next will be held on Friday, June 15, 2012, at 13:30