[Neutron] J-PARC Newsletter No. 73

Fri Apr 19 03:25:09 CEST 2019

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     J-PARC Project Newsletter
                                                   No.73, January 2019 Japan Proton Accelerator Research Complex under operation jointly by the High Energy Accelerator Research Organization (KEK) and the Japan Atomic Energy Agency (JAEA) http://j-parc.jp/index-e.html

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HEADLINES AND CONTENTS

1. [Overview]

 NEW YEAR STARTS WITH MORE STABILITY AND POWER FOR MORE RESULTS

2. [Accelerator Division]

 STABLE OPERATION OF THE ACCELERATORS FROM OCTOBER TO DECEMBER.

3. [Particle and Nuclear Physics Division]

 KOTO ANNOUNCED AN IMPROVED UPPER LIMIT ON THE KAON RARE DECAY.
 T2K HAS RELEASED NEW ANALYSIS RESULTS INCLUDING FULL 2018 DATASET.
 STATUS OF THE MUON G-2/ ELECTRIC DIPOLE MOMENT (EDM) (E34).
 STATUS OF THE COHERENT MUON TO ELECTRON TRANSITION (COMET).

4. [Materials and Life Science Division]

 STABLE USER PROGRAM OPERATION WAS CONTINUED AT 500 KW.
 THE 3RD NEUTRON AND MUON SCHOOL WAS HELD. 
 265 NEUTRON GENERAL PROPOSALS HAVE BEEN RECEIVED FOR THE 2019A PERIOD.
 SMALL GLITCH OVERSHADOWS MUON ROTATION TARGET.

5. [Nuclear Transmutation Division]

 SCOOPING UP THE 10 W BEAM FROM 250 kW PROTON STREAM (4).

6. [Safety Division]

 THE EMERGENCY DRILL ASSUMING A FIRE IN THE LINAC TUNNEL.
 FISCAL 2018 J-PARC SAFETY AUDIT.

7. [Editorial Note]

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1. [Overview] by Naohito SAITO
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NEW YEAR STARTS WITH MORE STABILITY AND POWER FOR MORE RESULTS

    This is the first newsletter issued in 2019, which was delayed for a few months due to many events in the new year. We are to restart the run after the maintenance end of the year/beginning of the new year. 
Until the end of the year, we have successfully operated the Material and Life science experimental Facility (MLF) at 500 kW or more with the high availability of more than 94%. The user operation of the Main Ring (MR) will restart in February after long maintenance of Hadron Experimental Facility (HEF).
    Meantime, we have been preparing for the J-PARC annual reviews; The International Advisory Committee (IAC) will meet on March 3 and 4, following meetings of Neutron Advisory Committee (NAC), ADS Technical Advisory Committee (T-TAC), Muon Advisory Committee (MAC), and Accelerator Technical Advisory Committee (A-TAC), and Physics Advisory Committee (PAC) for particle and nuclear physics. Since the last IAC meeting, we have produced many scientific results with users from academia and industry. We also made some progress in developing more uniform operation of MLF. In addition, we now have more concrete future plans of J-PARC upgrades to keep the facility attractive to users from domestic and overseas. We hope to present the current status and future perspectives of J-PARC as a coherent roadmap of the facility at IAC.
     As for the future of J-PARC, we are discussing near future upgrade projects in the context of Master Plan 2020 of Japan Science Council, which is to be called in February.  We held J-PARC-wide meeting in the beginning of January. The agenda and the materials presented can be found at the link below:
https://kds.kek.jp/indico/event/29990/
We have discussed an upgrade of MR along with neutrino facility upgrades, upgrades of experimental facilities, an extension of HEF, and COMET phase II, as well as muon g-2/EDM measurements at MLF. As a major upgrade of MLF, the second target station was discussed with more details of a concrete design, which was to be summarized in the form of Conceptual Design Report. 
The ADS project is now slightly modified to reflect the JAEA’s policy which enhances computational aspects, and to enhance Post-Irradiation-Examination (PIE) facility required for high-intensity frontier facility like J-PARC. In addition, heavy ion acceleration project, “J-PARC HI” was discussed from both scientific and technological aspects.
     With the stable and safe operation of J-PARC with highest possible beam power at all facilities, we hope to provide more opportunities for users to work together for outcomes, which we believe to contribute to all human beings!

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2. [Accelerator Division] by Kazuo HASEGAWA
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 STABLE OPERATION OF THE ACCELERATORS FROM OCTOBER TO DECEMBER

     A new operation run was started at the beginning of October after the summer shutdown. Accelerator study work at the beam currents of 5 mA and 50 mA was carried out at the linac. The study work followed at the 3 GeV Rapid Cycling Synchrotron (RCS) at the linac beam current of 50 mA for user operation. The main purposes of the study were to startup the machine, reproduce the accelerator parameters, confirm performance of some new components installed during the summer shutdown, new parameter survey for lower beam loss, etc.
     The neutron production target of the Materials and Life Science Experimental Facility (MLF) was replaced during the summer shutdown. 
On October 22, the user operation of MLF resumed at 300 kW and we increased the power to 500 kW on November 6. The operation was rather smooth until the morning of December 15, as scheduled. The availability of the MLF was sufficiently high about 94 percent from October to December, since we had no serious troubles at the linac, the RCS, and the MLF.
     During the period of October to December, operation of the Main Ring Synchrotron (MR) was suspended due to the improvement of the experimental facilities: refurbishment of Super-Kamiokande detector for the Neutrino experiment, and maintenance and upgrade work for the Hadron experimental facility.
We had a slightly longer shutdown period than normal from the end of December to the middle of January. We had a power outage at the end of December for the refurbishment of an old power station of Nuclear Science Research Institute of Japan Atomic Energy Agency, where our power line is connected. At the middle of January, MLF did not accept the beam because of the transportation of a used neutron production target to the storage building. This should be done as carefully as possible and was scheduled at that period. We started linac tuning on January 18 followed by the RCS and MR tuning. The user program of the MLF started on January 23, and that of the Hadron facility will start in February.

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3. [Particle and Nuclear Physics Division] by T. NOMURA, T. ISHIDA, T. MIBE, AND S. MIHARA
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KOTO ANNOUNCED AN IMPROVED UPPER LIMIT ON THE KAON RARE DECAY (by T. NOMURA)

     The neutral kaon experiment at the hadron facility now reaches the world-leading sensitivity in the search for a CP-violating rare decay. The KOTO experiment announced new upper limit on the branching ratio of KL->pi0 nu nubar decay, based on the data taken in 2015. 
After the first physics run in 2013, data were collected for 100 hours and the results were published in 2016, KOTO improved several detectors in order to reduce background and develop their sensitivity. 
The year two thousand and fifteen was a year that the hadron facility restarted its operation after renovation and KOTO conducted the first mass production of data taking from April to December. Intensive data analysis continued in particular to understand and suppress background for two and a half years, and KOTO finally set a new upper bound for the decay to be 3.0e-9 at 90% confidence level, which improved the world record by an order of magnitude. KOTO presented the result first at the high energy conference in July 2018
(ICHEP2018 at Seoul) and submitted the paper in October (http://arxiv.org/abs/1810.09655). The paper was accepted for publication in the middle of December and will appear in Physical Review Letters soon.
     KOTO collected about 1.4 times more data in 2016-2018 runs after a major upgrade in 2016 when a new photon detector surrounding the KL decay region was installed. The data analysis is ongoing which means that further development of methods to reduce background is an important key.
     In summer-autumn of 2018, KOTO was doing a second upgrade for a major detector: implementation of the both-end readout scheme for the electromagnetic calorimeter and new in-vacuo charged particle detector. KOTO will be ready for accepting the beam by the middle of February in 2019.

 T2K HAS RELEASED NEW ANALYSIS RESULTS INCLUDING FULL 2018 DATASET (by T. ISHIDA)

     In NuPhys2018 held in London in December 2018, T2K collaboration released new results based on the full dataset until 2018 summer corresponding to 3.2x10^21 protons on target (pot), 1.5x10^21 pot for neutrino mode and 1.65x10^21 pot for anti-neutrino mode. The latter was increased by 46% from previous release at Neutrino 2018 conference in June.
     With the dataset T2K has observed 75/15 events of single ring e-like event at the far Super-Kamiokande detector in neutrino/anti- neutrino mode operation, respectively. They can be compared to
74.4/17.1 events for prediction with maximum CP phase violation, dCP=
-pi/2 (in case no CP phase, the prediction is 62.2/19.4). The CP conservation lies outside of the 2-sigma interval, but not 3-sigma. 
The data prefers Normal mass ordering with probability of ~0.9.

Link: 
https://indico.ph.qmul.ac.uk/indico/contributionDisplay.py?contribId=
22&confId=289

     In summer of 2018, Super-Kamiokande was in big refurbishment for Gd loading which is almost in completion as scheduled. The beam-line upgrade towards 1.3 MW beam power and near neutrino detector upgrade are both in good progress, under review of Technical Design Reports.

 STATUS OF THE MUON G-2/ ELECTRIC DIPOLE MOMENT (EDM) (E34) (by T. MIBE)

     The E34 collaboration prepares for precision measurements of the muon anomalous magnetic moment and electric dipole moment. The Program Advisory Committee (PAC) recommended the stage-2 status. A letter for the stage-2 approval from the Institute of Particle and Nuclear Studies is given to the collaboration. Construction of the surface muon beamline (H-line) is in progress. A test experiment at the MLF D2 area was completed for the measurement of longitudinal distribution of RF accelerated muon beam. The collaboration is carrying out development of an IH-DTL test cavity, spin rotator, demonstration of spiral beam injection to the storage ring, and construction of the positron-tracking detector. An international workshop on physics of muonium and related topics [1] was co- organized at Osaka University in December 10-11, where possible applications of the thermal muonium production were actively discussed.

[1] http://www-kuno.phys.sci.osaka-u.ac.jp/muonium2018/

 STATUS OF THE COHERENT MUON TO ELECTRON TRANSITION (COMET) (by S. MIHARA)

     The COMET experiment aims to search for the lepton-flavor violating muon reaction, mu-e conversion, with sensitivity better than 10^{-14} in Phase I.
     Construction of the COMET facility is in progress: installation of proton beamline elements in the switch yard is almost completed and coil winding for the pion capture solenoid is in progress.
     Fabrication of the solenoid magnet connecting the muon transport curved solenoid and the detector solenoid has finally started. It makes the magnetic field distribution in the detector region unaffected by the beamline solenoid. It also contains a beam collimator inside. The collaboration has completed summarizing experiment details in the Technical Design Report (TDR). Concise version of the report can be found at [2].

[2] http://arxiv.org/abs/1812.09018

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4. [Materials and Life Science Division] by Toshiji KANAYA
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 STABLE USER PROGRAM OPERATION WAS CONTINUED AT 500 KW

     1) Neutron Source
     On October 22, the neutron production with a new mercury target vessel began for the MLF user programs. Though the beam operation started at 300 kW due to the functional problem of the helium gas supply system, which is used for gas bubbling in the mercury target, the beam power was raised to 500 kW on November 6. Current mercury target vessel has the same structure as the former one that had a monolithic structure for the inner mercury vessel and outer water shroud jointed with ribs between them. In order to secure the robustness and reliability, the weld lines of the target vessel where the initial defects tend to be generated were carefully inspected in the course of fabrication. Before the user program started, the target beam study was carried out. The temperature and vibration of the mercury target were compared with the former ones to check the structural soundness of the target vessel. The user program ended on December 16 with a good availability of 94% during the scheduled beam time of 50 days. Because the transportation of the used target vessel to the storage facility from MLF is planned in early January, next neutron production operation will begin on January 23, 2019. 

 THE 3RD NEUTRON AND MUON SCHOOL WAS HELD 

 265 NEUTRON GENERAL PROPOSALS HAVE BEEN RECEIVED FOR THE 2019A PERIOD

     2) Neutron Instruments and Science
     After the summer shutdown, user program of 2018A period was resumed from October 22. From November 8, 2018B period was started.
     The 3rd Neutron and Muon School was held in November 20-24. 35 young researchers and graduate students from China, India, Korea, Thailand, Russia, and United Kingdom, as well as Japan participated in the school. From the neutron groups, nine instruments contributed to hands-on experiments.
     The 3rd ESS-J-PARC Workshop was held in November 13-15. 24 participants from ESS visited J-PARC. On the first day of the workshop, the greetings of H.E. Mr. Magnus Robach, Ambassador of Sweden were given. At the meetings, experts exchanged information on a wide range of items such as accelerator fields, safety relations, radiation monitoring, neutron targets, handling of radioactive substances, deuteration of experimental samples, and discussions on clarification of concrete cooperation matters.
     Call for General use proposals and New User Promotion proposals for the 2019A period was closed on November 7 and we received 265 neutron proposals. Those proposals will be sent to the Neutron Science Proposal Review Committee / the Proposal Evaluation Committee for reviewing process. The final results will be sent to users in February 2019. From 2019A period, POLANO (polarized neutron chopper spectrometer at BL23) will be open to general users.

 SMALL GLITCH OVERSHADOWS MUON ROTATION TARGET

     3) Muon Science Facility (MUSE)
     Since its installation to the primary proton beamline of MLF in 2014, the muon rotating target system served for stable muon beam delivery to users without trouble. However, a recent report on the potential damage of a flexible joint for transferring motor rotation to the graphite disk target raised concern about the possibility for unexpected suspension of target rotation due to the breakdown of the joint. The option of replacing the whole target system with a brand-new spare was deferred to avoid the risk associated with limited available time. Based on the numerical simulations on the temperature and stress of a stopped graphite disk exposed to a 500 kW proton beam, some measures were taken to minimize potential hazards expected in case of suspended target rotation. In particular, a buffer tank for exhaust gas was installed behind the vacuum pump system connected to the proton beamline to accumulate tritium gas emitted from the target. By ensuring that those measures were effective, the muon user program was resumed in the beginning of November after two weeks delay from the original schedule.

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5. [Nuclear Transmutation Division] by Hayanori TAKEI
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 SCOOPING UP THE    10 W BEAM FROM 250 KW PROTON STREAM (4)

     In the previous issue of the J-PARC Newsletter #68, we described a laser charge exchange method (LCE) for the Transmutation Physics Experimental Facility, TEF-P. This LCE method is a meticulous low power beam extraction method from high power proton beam stream of the J-PARC linac. The LCE device consists of a bright laser with the wavelength of 1064 nm and laser transport system with beam position controllers. The negative proton (H-) beam from the J-PARC linac is exposed to the laser beam, which can strip one of the two electrons, so as to change H- to neutral ones (H0). The other electron of the H0 is finally stripped by a carbon foil so that the positive protons
(H+) are introduced into TEF-P.
     We installed the LCE device at the end of the 3-MeV linac in cooperation with the J-PARC accelerator division. To measure the power of the charge-exchanged H+ beam, an LCE experiment was conducted using the bright pulse laser beam. The results of this LCE experiment were summarized in ref. [DOI: 10.1585 / pfr.13.2406012]. Next, we conducted the LCE experiment using the bright continuous laser beam to extract the continuous H+ beam.
     As a result of the experiment, a charge-exchanged H+ beam with a power of 0.59 mW was obtained. If the laser light from this LCE device collided with the H- beam (400 MeV, 250 kW) delivered from the J-PARC linac, the stripped H+ beam with a power of 0.73 W equivalent was obtained, and this value agrees well with the theoretical result. 
Thus, we established an elemental technology required for the TEF, i.e., the foundations of control technology for the extraction of the low-power H+ beam from the high-power H− beam at J-PARC.

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6. [Safety Division] by Yukihiro MIYAMOTO and Kotaro BESSHO
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 THE EMERGENCY DRILL ASSUMING A FIRE IN THE LINAC TUNNEL

     The emergency drill was held on Sep. 6. In the training, it was assumed that a fire occurred in the linac tunnel, and workers could not extinguish the fire by initial fire-fighting actions. The workers should evacuate safely from the tunnel area, thus certain evacuee- confirmation was an important subject of the drill. Further the procedures to extinguish a fire by sealing the tunnel were confirmed.
These experiences must be valuable for improving safety measures in emergency.

 FISCAL 2018 J-PARC SAFETY AUDIT

     The fiscal 2018 J-PARC safety audit was conducted by two auditors on Nov. 20-21. They reviewed the points: 1) Management of work safety, 2) Introduction of “Improvement of the operational procedures for radiation protection”, 3) Effectiveness and improvements of radiation safety education, 4) Communication in emergency, 5) Promotion of the safety culture. Review on a toolbox meeting held before the work was also carried out. The auditors gave us valuable suggestions for future safety efforts in J-PARC.

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7. [Editorial Note]
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Editorial Board:
Toshifumi TSUKAMOTO (Chair): toshifumi.tsukamoto at kek.jp Kaoru SHIBATA: shibata.kaoru@ jaea.go.jp Takashi ITO: itou.takashi at jaea.go.jp Dick MISCHKE (English Editor): mischke at triumf.ca Tomoko KAWAMURA (Secretary): kawamura.tomoko at jaea.go.jp
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