[Neutron] J-PARC Newsletter No. 79

Wed Jul 29 07:52:48 CEST 2020

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     J-PARC Project Newsletter
                                                   No.79, July 2020 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 RESEARCH LIFE WITH COVID-19 AT J-PARC.

2. [Accelerator Division]

   OPERATION STATUS OF THE ACCELERATORS.

3. [Particle and Nuclear Physics Division]

   FIRST BEAM AT THE NEW BEAMLINE IN HADRON EXPERIMENTAL FACILITY.
   NEW RESULTS ON THE NEUTRINO CP PHASE AND THE SARUHASHI PRIZE TO A. K. ICHIKAWA.
   STATUS OF THE COHERENT MUON TO ELECTRON TRANSITION (COMET).
   STATUS OF THE MUON G-2/ ELECTRIC DIPOLE MOMENT. (EDM) (E34).

4. [Materials and Life Science Division]

  GREETING FROM THE NEW LEADER OF THE MATERIALS AND LIFE SCIENCE EXPERIMENTAL FACILITY (MLF) DIVISION.
  BEAM POWER WAS RAISED TO 600 kW.
  MLF IS CALLING GENERAL USE PROPOSALS FOR THE ROUND 2020B+2021A.
  CONSTRUCTION OF ELECTRIC POWER SUBSTATION FOR H-LINE COMPLETED.

5. [Nuclear Transmutation Division]

   MEASUREMENT OF DISPLACEMENT CROSS-SECTION FOR PROTON BEAM INTERCEPTING MATERIAL.

6. [Safety Division]

   THE APPLICATION FOR A LICENSE OF THE OPERATION WAS GRANTED.
   THE SAFETY INSPECTION WAS SUCCESSFULLY CONDUCTED.

7. [Editorial Note]

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1. [Overview] by Naohito SAITO
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 NEW RESEARCH LIFE WITH COVID-19 AT J-PARC

     We hope you all are doing well and healthy under still expanding gloom. As reported in the previous issue, we have managed to restart the operation of J-PARC in mid-May. Since then, we have fully opened the facility for users, while some domestic users still had travel restrictions from their own institutions.  
     The operation ended as of June 27, and we have now entered into summer maintenance. Even during a short period of operation, we were able to make progress of the facilities entering into a new phase of J-PARC: a new beamline in the Hadron Experimental Facility (HEF) started its operation to accommodate immediately user experiments, and high power operation of Material and Life experimental Facility (MLF) was successfully performed with most of the beamline operated at “1 MW (1)” for 36.5 hours. These accomplishments are described by those facilities later in this issue.
     While we are editing this issue, a confirmed number of positive cases started to increase in Japan. We have been updating our measures to prevent us from infections through the discussions at the Special Measures Taskforce, co-headed by Dr. Ishii, the deputy director of J-PARC for safety and myself. The latest message can be found at https://j-parc.jp/c/en/j-parc-covid/index.html (Japanese) and http://j-parc.jp/c/en/j-parc-covid/index.html (English).  
     The message is not only for staff and users, but also for the contractors who are increasingly important during the maintenance. We are asking for physical distancing, wearing facial masks properly in talking, cleaning and washing hands thoroughly, and getting fresh air regularly. Now we have added the counter measures for heatstroke, since wearing mask tends to increase body temperature.
     With all these possible measures to protect users, ourselves, and anyone working at J-PARC, which might be overdoing, we will make our best efforts to keep our facility open for research and education as much as possible even with upcoming next waves. We will proactively update our measures reflecting the up-to-date knowledge on COVID-19 and relevant information and share with users and contractors through our homepage.
     Stay healthy and we are looking forward to seeing you at upcoming beam time after summer shutdown at J-PARC!

(1) The operation power of 1 MW means the power of beam accelerated at Rapid Cycle Synchrotron (RSC), and typical power received at MLF was 0.92 MW due to bunches extracted for further acceleration at the Main Ring (MR).

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2. [Accelerator Division] by Michikazu KINSHO
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 OPERATION STATUS OF THE ACCELERATORS

     The beam operation as an operation run of Run#84, which started in January, continued until April 20th, when it was stopped for COVID-19. The scheduled outage was May 1st. The user program was executed in only the Materials and Life Science experimental facility (MLF), at a beam power of 500 kW, because licensing for a new target and a new beam line in the HD was delayed from the Authority and beam operation was postponed. A new operation run was started on May 11th, we started the user program for the MLF at a beam power 500 kW which was the same as the previous Run#84 on May 15th, and the beam power was increased to 600 kW from May 18th. The user program was carried out as scheduled until June 27th, and it was successfully executed with a beam power of 1 MW from June 25th to 27th. The user operation for the MLF ended on June 27th followed by the six days of accelerator study before the summer shutdown.
     After the shutdown, we will start linac tuning on October 25th followed by the RCS tuning. The user program of the MLF will start on November 9th.
     For the Main Ring synchrotron (MR), the beam delivery to the Hadron experimental facility (HD) was started at small beam power on May 28th. After the fine tuning of the MR, we delivered beam at around 51 kW, which was the similar level as the previous operation. The HD user program was executed on June 25th and 26th at a beam power of around 51 kW, and one day beam study was carried out after HD user program. The MR operation was completed on June 27th until after the summer shutdown.

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3. [Particle and Nuclear Physics Division] by T. TAKAHASHI and K. OZAWA
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 First beam at the new beamline in Hadron Experimental Facility (by H. Takahashi, Y. Komatsu, K. Ozawa)

     We had beam time from May 23 to June 25 for the Hadron Experimental Facility. During the beam time, we succeeded in having the first beam to a new beamline. The new beamline was constructed to deliver primary protons to experimental areas and experiments can use primary protons directly. This is the first case to use primary protons directly for experiments at J-PARC.
     The beamline was implemented as a branch of the existing beamline. A very tiny fraction (0.05%) of the primary beam is separated and transported into the south part of the Hadron experimental hall. The intensity of the new beamline is 10^10 protons per spill and it is high enough for direct uses by experiments. Beam tunings were carefully performed at the beginning of the beam time. We adjusted beam positions and profiles and increased the beam intensity gradually. Finally, we succeeded in having the designed beam intensity and a minimum loss of the beam. An official inspection for radiation safety issues was done on June 22 and the new beamline started its operation. A new experiment to study modifications of mass spectra of vector mesons in a nucleus was started at the new beamline.
     In parallel, we performed a Sigma-Nucleon scattering experiment at the K1.8 beamline and measurements of K_L to pi0 nu nu-bar experiment at the KL beamline. 

 NEW RESULTS ON THE NEUTRINO CP PHASE AND THE SARUHASHI PRIZE TO A. K. ICHIKAWA (by T. Matsubara) 

     In April, the T2K collaboration published new results in the scientific journal Nature placing the strongest constraint on the leptonic CP violating phase in neutrino oscillation. CP violation in the neutrino sector provides a hint to explain the matter-antimatter imbalance of the universe.
     Theoretically, the phase can take any value from  -180 deg to 180 deg and the actual value is not yet known. T2K evaluated the confidence intervals for the phase, by analyzing data with 1.49x10^21 (neutrino beam mode) and 1.64x10^21 (antineutrino beam mode) protons on target from the accelerator.
     The data is most compatible with a value close to -90 deg and the disfavored region at the 99.7% (3 sigma) confidence level is almost half of the possible region: -2 deg to 165 deg. The CP symmetry (0 deg and 180 deg) is disfavored at the 95% confidence level, which is consistent with previous results in 2018. This result is a major step forward to know whether neutrinos and antineutrinos behave differently.

     A. K. Ichikawa (Kyoto Univ.), a current spokesperson of the T2K collaboration, was awarded the Saruhashi prize 2020 that is an annual prize to a woman researcher in the field of natural science (http://www.saruhashi.net/index.html, only in Japanese). The research theme for the award is "unraveling the nature of neutrino by accelerator-based long baseline neutrino experiment".

Recent Publications

o Constraint on the matter–antimatter symmetry-violating phase in neutrino oscillations, K. Abe et al.
   https://www.nature.com/articles/s41586-020-2177-0

o First combined measurement of the muon neutrino and antineutrino charged-current cross section without pions in the final state at T2K, K. Abe et al.
   https://doi.org/10.1103/PhysRevD.101.112001

o Simultaneous measurement of the muon neutrino charged-current cross section on oxygen and carbon without pions in the final state at T2K, K. Abe et al.
   https://doi.org/10.1103/PhysRevD.101.112004 

 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.
     After completing winding of all coils for the capture solenoid in JFY2019, we started assembling them to two larger coils by connecting them mechanically, electrically, and thermally. Once this assembly work finishes, the cold mass will be installed into a large cryostat for cooling down to the liquid helium temperature. Close communication with the manufacturing factory continues until we complete the production.

     A new proposal to measure the 8 GeV proton beam extinction factor in advance of the COMET phase-I has been submitted. We plan to conduct this measurement with a new accelerator configuration established after long discussion with the J-PARC accelerator team based on the result obtained in the previous test. The expected sensitivity of the extinction factor measurement is 4x10^{-12}.

     The collaboration had a collaboration meeting fully by videoconference in June 29 - July 3 as we still suffer from the COVID-19 effect.  Duration of the meeting of each day was shortened to cope with the time differences of collaboration members from different countries. Nevertheless, active discussion was made to maintain the experiment group activity, and the schedule toward the start of phase-I was updated.

 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 muon g-2 theory initiative released a white paper in arXiv where a single value for muon g-2 in the standard model is given. It appears the discrepancy from the BNL experiment is at a level of 3.7 standard deviations. The collaboration held a collaboration meeting to discuss global plan of the experiment by using a video conference system in June 17-18.
     Demonstration of laser ionization of muonium for the thermal energy positive muon source is in preparation. A test experiment to ionize hydrogen atoms was successful in KEK Tsukuba campus. The experimental setup is being upgraded for the upcoming experiment at J-PARC. A paper on muonium production was submitted.
     Preparations for 1 MeV acceleration of muon with RFQ and IH-DTL are in progress at J-PARC linac bldg. Testing of DAW (Disk And Washer) cold model for middle range velocity is in progress.
     The three-dimensional beam injection has been studied with low energy electron beam by KEK and Ibaraki University. A kicker system for beam storage was developed.
     The silicon tracking detector is being assembled at KEK mechanical engineering center in collaboration with Kyushu University. A paper on front-end electronics was submitted. Software framework with simulation package was released. Tutorial lectures on the software framework were given to the collaboration. A high statistics production of end-to-end simulation data is being prepared. 

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4. [Materials and Life Science Division] by Toshiya OTOMO
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 GREETING FROM THE NEW LEADER OF THE MATERIALS AND LIFE SCIENCE EXPERIMENTAL FACILITY (MLF) DIVISION

     I assumed leadership of the MLF division in J-PARC on April 1, 2020 as a replacement for the former division head, Prof. Toshiji Kanaya. It has been more than 10 years since the first beam in 2008 and I think that it is now the time to clarify a 10 years vision of MLF for producing the world’s top outcomes in science and industrial applications with neutron and muon. I am more than happy to have an occasion to work with MLF staff and users in the world to produce excellent outcomes.

Toshiya Otomo
Head of the Materials and Life Science Experimental Facility Division

 BEAM POWER WAS RAISED TO 600 kW

1) Neutron Source
     The beam operation of MLF is going on with the daily availability of 93.7% on average since April 1, as of June 27 in 2020. The beam operation was forced to be stopped from April 20 to May 15 due to the coronavirus pandemic. After the beam operation was resumed, the beam power was raised from 500 kW to 600 kW on May 18.
     At the end of this run time, 1 MW beam operation with the duration of 36.5 hours was held from June 25 to 27 which is much longer than the 1 MW operation of 10.5 hours last year. Much facility data of high-power operation were obtained.

 MLF IS CALLING GENERAL USE PROPOSALS FOR THE ROUND 2020B+2021A

2) Neutron Instruments and Science
     MLF beam operation has been paused on April 20 taking into consideration the request of the Japanese government for controlling spreading infection of COVID-19 (declaration of a state of emergency). The declaration was lifted on May 14, and MLF decided to resume the beam operation on the next day 15. We started from the in-house staff work, then opened for the users step by step. Until the end of May, MLF activities are almost fully opened for domestic users.
     All the MLF user experiments scheduled on the round 2019A, 2019B and 2020A which are yet to be carried out partly due to the delay of beam delivery after the long shut down in November 2019 and partly due to the COVID-19 pandemic can be postponed (carried over) but will expire in the end of fiscal 2020 (March 31, 2021) without further extension.
     The upcoming MLF proposal round 2020B combined with 2021A is called during June 17 to July 15, which is two months behind the usual schedule (URL: https://mlfinfo.jp/en/user/proposals/2020B2021A/).
     Many symposia, conferences and workshops have been cancelled in this period all over the world. MLF plans to organize two major international workshops, DENIM (The 9th annual Design and Engineering of Neutron Instruments Meeting) and ISSE Workshop (11th International Workshop on Sample Environment at Scattering Facilities), they both are strongly important and related to neutron instrumentation and techniques. These two series of workshops were postponed to September in 2021.

CONSTRUCTION OF ELECTRIC POWER SUBSTATION FOR H-LINE COMPLETED

3) Muon Science Facility (MUSE)
     The H-line is one of the four branches of muon beamlines envisaged in the original plan of MLF, located next to the S-line in experimental hall No. 1. While it has been in a status of limbo for years, the J-PARC headquarters provided partial support every year since 2016 for putting the plan forward. The support was used for building the new electric power substation needed to meet the huge demand of electricity expected for the H-line operation. The construction work underwent steady progress for the past three years, and all the civil engineering works and cabling through the MLF building were finally completed towards the end of FY2019.  This marks a major milestone in realizing the H-line, and now it is planned in the coming summer shutdown period to complete the minimal equipment required for muon beam delivery to the H1 experimental area.

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5. [Nuclear Transmutation Division] by Shin-ichiro MEIGO
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 MEASUREMENT OF DISPLACEMENT CROSS-SECTION FOR PROTON BEAM INTERCEPTING MATERIAL

     For the accelerator-driven system (ADS), beam intercepting material such as a beam window plays an important role. To evaluate the displacement damage of materials irradiated with the proton beam, displacement per atom (dpa) is widely utilized as a damage index, which is estimated by displacement cross-section and particle flux. Although the dpa is widely employed as a damage index, the displacement cross-sections for the proton energy employed in the ADS, especially for a beam window made of iron, is unknown. Therefore, we carried out the experiment of measurement of the displacement cross-section at J-PARC using 3 GeV proton synchrotron (RCS).
     Since the electrical resistance increases by the displacement in the metal, the displacement cross-section can obtain from the resistivity change of the sample owing to the proton irradiation. To sustain the defect created by the irradiation, the sample was kept under the cryo-temperature (4 K). After a series of measurements, displacement cross-sections of iron were obtained, which are the first experimental data in the world in the energy range applied to the ADS.
     With the experimental data, the calculation model for displacement was validated. The Norgett−Robinson−Torrens displacements per atom (NRT-dpa) model widely utilized for the estimation displacement was found to give about 2 times larger than the experiment. On the other hand, the cutting edge model, athermal recombination correction (arc) based on the molecular dynamics simulation, showed good agreement with the experiment.

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6. [Safety Division] by Kotaro BESSHO and Yoshihiro NAKANE
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 THE APPLICATION FOR A LICENSE OF THE OPERATION WAS GRANTED

     The application for changes of the radiological license was granted by the Nuclear Regulation Authority (NRA) on April 28. The approved changes in the application were the power-up and a new primary beam line in the Hadron Experimental Facility and the minor change of the radiation controlled area of the Neutrino Experimental Facility.

 THE SAFETY INSPECTION WAS SUCCESSFULLY CONDUCTED

     The safety inspection of the Hadron Experimental Facility (HD) was successfully conducted, and the certificate was issued on June 24 by Radiation Management Institute, Inc. The inspection items were the shielding construction prepared for a new primary beam line, the measurement of radiation dose rates around the shielding construction, and the operation tests on the safety interlocks in HD.

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7. [Editorial Note]
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Past issues are available from the below link.
http://j-parc.jp/c/en/topics/project-newsletter/index.html

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Editorial Board:
Toshifumi TSUKAMOTO (Chair): toshifumi.tsukamoto at kek.jp 
Kaoru SHIBATA: shibata.kaoru at jaea.go.jp 
Taketoshi MORISHITA: morishita.takatoshi at jaea.go.jp
Dick MISCHKE (English Editor): mischke at triumf.ca 
Keiko NEMOTO (Secretary): nemoto.keiko at jaea.go.jp
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