[Neutron] J-PARC Newsletter No. 61

shibata.kaoru shibata.kaoru at jaea.go.jp
Fri Feb 26 03:03:06 CET 2016


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     J-PARC Project Newsletter
                                                     No.61, January 2016
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]

 J-PARC AIMS FOR HIGHER STABILITY AND EFFICIENCY FOR MORE SCIENCE.

2. [Accelerator Division]
 
 OPERATION STATUS OF THE ACCELERATORS.

3. [Particle and Nuclear Physics Division]

 OBSERVATION OF SPIN-DEPENDENT CHARGE SYMMETRY BREAKING IN LAMBDA-N 
INTERACTION.
 PROFESSOR EMERITUS K. NISHIKAWA AND K2K/T2K HAS BEEN AWARDED THE 
BREAKTHROUGH PRIZE.
 PROGRESS IN MUON PARTICLE PHYSICS PROGRAMS. 
 HINT2015.

4. [Materials and Life Science Division]

 UNSCHEDULED SHUTDOWN DUE TO THE PROBLEM OF TARGET VESSEL.
 NEUTRON USER PROGRAM WAS SUSPENDED FROM NOVEMBER 20. 
 THE 7TH AONSA NEUTRON SCHOOL AND THE 3RD MLF SCHOOL WAS JOINTLY HELD.
 S-LINE IS FINALY UP AND RUNNING.

5. [Nuclear Transmutation Division]

 GROUND SURVEY FOR THE HEART OF TRANSMUTATION PHYSICS EXPERIMENTAL 
FACILITY (TEF-P).

6. [Safety Division]

 THE PERIODICAL INSPECTION WAS SUCCESSFULLY CONDUCTED BY THE NUCLEAR 
SAFETY TECHNOLOGY CENTER (NUSTEC).
 AN EMERGENCY DRILL WAS HELD ASSUMING RADIATION EXPOSURE ACCIDENT.
 FISCAL 2015 J-PARC SAFETY AUDIT.

7. [Editorial Note]


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1. [Overview] by Naohito SAITO
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 J-PARC AIMS FOR HIGHER STABILITY AND EFFICIENCY FOR MORE SCIENCE 

     This is the first message from J-PARC for this year. I would like 
to wish for all of you a very successful and fruitful year. 
     Last year was a year of struggle for J-PARC. It started with a 
small fire incident in the Materials and Life Science Experimental 
Facility (MLF), which resulted in a delay in the program execution 
at all facilities. At the end of April, we were able to restart 
operation of the Hadron Experimental Facility after nearly two years 
of renovation and improvements in safety measures. However, we were 
not able to keep all facilities in an operational state for more than 
four days. We had a water leak in the protection vessel of the Mercury 
target for neutron production at MLF. The beam was back to MLF in late 
October, but we could not keep the beam for more than a month due to 
a water leak from another location in the target vessel. Now we are 
trying to restart the MLF beam operation with lower beam power, i.e. 
200 kW, because the mechanically robust target system we have is not 
equipped with the helium bubbling system that is considered necessary 
to go beyond 300 kW. As a user facility, it is obviously the first 
priority to provide beam stably.  We, J-PARC as a whole, are working 
hard to increase the availability of all facilities. By the way, the 
Hadron Facility enjoyed continuous beam in November and December at 
an average availability of 85%. Now the Neutrino Facility has started 
to receive the beam after eight months of maintenance. 
   
     The budget for the next fiscal year is yet to be fixed especially 
for the KEK side, but it is getting clear now that we are going to 
receive funding for a new power supply for the main ring, which would 
provide highly stable currents to the magnets with high repetition 
rate. Both the neutrino program and the hadron program will benefit 
from this new power supply and we will work hard to construct the 
power supply in a timely manner. On the other hand, we need to expect 
fewer months of operation in both MLF and for the MR program. We will 
try to maximize the actual beam time for users by improving the 
availability of all facilities.  
    
     Having written all the above, it is definitely true that we are 
encouraged by various stakeholders and the local community to produce 
excellent scientific results. We will make every effort towards the 
creation of science by bringing all J-PARC facilities to the next 
stage of the high intensity frontier with stable and safe operations. 
To achieve that goal, we appreciate even closer cooperation with all 
users. 


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2. [Accelerator Division] by Kazuo HASEGAWA
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 OPERATION STATUS OF THE ACCELERATORS

     A new operation run, RUN#64, was started at the end of September 
after the summer shutdown. An accelerator study work at higher linac 
beam current of 50 mA was carried out as well as confirmation of
reproducibility.
     In the slow extraction (SX) mode of the main ring (MR), we have 
taken a shorter acceleration time of 1.4 seconds, which is the same 
as that in the fast extraction mode, rather than 1.9 seconds. The MR 
SX cycle time was shortened from 6.0 to 5.52 seconds. On October 15, 
beam delivery to the Hadron Experimental Facility (HD) users was 
started with the beam power of 32 kW. The shorter cycle time and the 
machine study have increased the beam power to 42 kW. The user 
operation for the HD ended on the morning of December 18 as scheduled.
     On October 24, the beam delivery to the Materials and Life 
Science Experimental Facility (MLF) was resumed at the beam power of 
500 kW as before the summer shutdown. However, the operation to the 
MLF was suspended again on November 20 due to a defect in the neutron 
production target.
     The availability of the operation runs evaluated in the HD user 
runs from September to December was roughly 83%. The main factors for 
down time were many defects at the Linac; the 3-GeV Rapid Cycling 
Synchrotron and the MR were relatively stable. Several defects related 
to high voltage, such as an insulation breakdown in a high voltage 
cable and a klystron discharge, suspended the operation for 11 to 21 
hours, respectively. One of the Linac ventilation systems stopped due 
to the current leakage. This event occurred three times and each 
event stopped the operation for several hours. Some other Linac 
defects, such as lack of a timing pulse and cooling water flow 
decrease, also caused unscheduled suspensions. We have patched up or 
fixed most of defects but some need mid- or long-term treatment.


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3. [Particle and Nuclear Physics Division] by T.O. YAMAMOTO, 
T. TAKAHASHI, T. TSUKAMOTO, S. MIHARA AND T. KOBAYASHI
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 OBSERVATION OF SPIN-DEPENDENT CHARGE SYMMETRY BREAKING IN LAMBDA-N 
INTERACTION (by T.O. YAMAMOTO and T. TAKAHASHI)

     The symmetry of the nuclear force under the exchange of protons 
and neutrons is a basic concept in nuclear physics and it is called 
charge symmetry. To study charge symmetry in strangeness nuclei, the 
binding energy of a He-4-Lambda hypernucleus was precisely measured 
at the Hadron Experimental Facility of J-PARC. As a result, an 
unexpectedly large charge-symmetry breaking was observed.
     The J-PARC E13 group measured gamma-rays from He-4-Lambda 
hypernuclei produced by (K-, pi-) reactions on a helium target at the 
K1.8 beamline. Gamma-rays emitted by transition from the exited 1+ 
state to the ground 0+ state were clearly observed and the excitation 
energy of 1.406+-0.002(stat.)+-0.002(syst.) MeV was obtained. On the 
other hand, the Hydrogen-4-Lambda nucleus, which is the charge-
conjugate of Helium-4-Lambda nucleus, is known to have the excitation 
energy of 1.09+-0.02MeV. The difference of excitation energies is 
quite large and, by combining with data taken by nuclear emulsion 
experiments,depends on their spin states.
     The result is considered to be the first evidence of a spin-
dependent charge-symmetry breaking in the nuclear force with a Lambda 
hyperon. The result was published in PRL115, 222501 and selected as 
an Editor's Suggestion.

 PROFESSOR EMERITUS K. NISHIKAWA AND K2K/T2K HAS BEEN AWARDED THE 
BREAKTHROUGH PRIZE (by T. TSUKAMOTO)

     Professor Emeritus K. Nishikawa (the 1st spokesperson of T2K 
and also the former Deputy Director of J-PARC Center) and K2K/T2K 
were jointly awarded the 2016 Breakthrough Prize in Fundamental 
Physics with Kamland, Daya-Bay, Super-Kamiokande, and the Sudbury 
Neutrino Observatory (SNO) experiments. The Breakthrough Prizes honor 
important achievements in Fundamental Physics, Life Science and 
Mathematics (https://breakthroughprize.org).

     At the end of the last beam operation, a slight pressure decrease 
was observed in the helium cooling line of the target. Investigation 
of the cause was done during the maintenance period and a leak was 
found at the connection between a ceramic part and a metal part. The 
leaking part was successfully replaced by using the manipulator in the 
hot cell with an international collaboration among High Energy 
Accelerator Research Organization (KEK), Rutherford Appleton 
Laboratory (RAL), and TRIUMF in December. The neutrino beam facility 
will be ready for the beam from January 31.

 PROGRESS IN MUON PARTICLE PHYSICS PROGRAMS (by S. MIHARA)

     The construction of detectors for the E21 COMET experiment 
searching for mu-e conversion in muonic aluminum has proceeded; wire 
stringing of the cylindrical drift chamber (CDC), the main detector of 
COMET Phase-I, was successfully completed in December 2015. It took 
more than 120 days to string about 20000 wires with proper tensions 
and stereo angles. The team will continue further checks of the wires.
The physics program and facility construction towards the second stage 
of the experiment were thoroughly discussed in December 2015.

     The E34 collaboration for precision measurements of muon 
anomalous magnetic moment and electric dipole moment obtained a grant 
for construction of a part of the positron-tracking detector. A 
technology for shimming the magnetic field to achieve local uniformity 
better than 1 ppm was proven with a 1.6 T MRI magnet at J-PARC.

 HINT2015 (by T. KOBAYASHI)

     The international workshop on future potential of a high 
intensity proton accelerator for particle and nuclear physics, 
HINT2015, was held from October 13 to 15, 2015 at the Ibaraki Quantum 
Beam Research Center (IQBRC) in Tokai adjacent to J-PARC.
     The new workshop focused on future prospects for high-intensity 
proton accelerators and beams toward multi Mega-Watt (MW) power and 
the new frontier in particle and nuclear physics that is explored by 
high intensity beams. Lively discussions were held among 129 
scientists from 12 countries who participated in the workshop. 
For more information, see http://j-parc.jp/pn/HINT2015/


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4. [Materials and Life Science Division] by Toshiji KANAYA
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 UNSCHEDULED SHUTDOWN DUE TO THE PROBLEM OF TARGET VESSEL
 
     1) Neutron Source
     On October 27, neutron production for the Materials and Life 
Science Experimental Facility (MLF) user program resumed with 500-kW 
proton beam. However, the MLF user operation has been stopped due to 
an unexpected trouble of the target vessel since November 20. The 
problem occurred inside the target shroud and was different from what 
happened last April. There was no leakage of radioactive materials by 
this problem. We have been working to diagnose the cause of the 
problem. To assure more reliable operation, we decided to replace the 
target vessel and have begun preparations for the replacement. 
     At the same time, the performance of the helium refrigerator of 
the cryogenic hydrogen circulation system for the moderators degraded. 
We found that water accumulated in the heat exchanger of the helium 
refrigerator. We started to regenerate the charcoal which might be 
the source of the water contamination and also conducted related 
purification during the shut-down period for the target replacement.    
     We sincerely apologize about the inconvenience that the MLF user 
program is stopped for a long period and would deeply appreciate your 
understanding. 

 NEUTRON USER PROGRAM WAS SUSPENDED FROM NOVEMBER 20
 THE 7TH AONSA NEUTRON SCHOOL AND THE 3RD MLF SCHOOL WAS JOINTLY HELD

     2) Neutron Instruments and Science
     From October 27, we resumed the user program with 18 neutron 
instruments and commissioning activities for 2 beam lines, but they 
were interrupted on November 20 due to the problem at the neutron 
target. Staff members of all beam lines are now tightly communicating 
with users whose experiments have been suspended by the trouble for 
resumption of their experiments in the future. 
     From December 1 to 5, the joint school of the 7th AONSA Neutron 
School and the 3rd MLF School was held. The school was sponsored and 
supported by Asia-Oceania Neutron Scattering Association (AONSA), The 
Japanese Society for Neutron Science (JSNS), International Atomic 
Energy Agency (IAEA), Society of Muon and Meson Science of Japan, 
Comprehensive Research Organization for Science and Society, The 
Institute for Solid State Physics in The University of Tokyo, 
Institute of Materials Structure Science in High Energy Accelerator 
Research Organization, Ibaraki Prefecture, and Australian Institute 
of Nuclear Science and Engineering. Forty one young researchers and 
graduate students participated in the school from Japan, Korea, 
Australia, Indonesia, India, China, Taiwan, Malaysia, the United 
States, and Iran. Although J-PARC had no beam operation of neutrons 
or muons during the school unfortunately, the participants enjoyed 
cold-experiments on 11 neutron beam lines and one muon instrument 
followed by comprehensive lectures on neutron and muon sciences. In 
2016, we will organize an international neutron and muon school again.

 S-LINE IS FINALY UP AND RUNNING

     3) Muon Science Facility (MUSE)
    In the Experimental Hall No.1, the first surface muon beam was 
successfully delivered to the S1 area at the end of new S-line in 
November 2015. The beam line had been completed a year ago; however, 
the original plan of commission had to be postponed due to a series 
of incidents at the MLF, the fire incident in MUSE and the trouble of 
the neutron target vessel which led to the unscheduled shutdown of 
MUSE until the resumption of the MLF operation in late October 2015. 
The first beam at the S1 area still brings great excitement to the 
muon community. Even though the S-line has been delayed and there are 
"ever-increasing demands", the supply of beam time will catch up.


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5. [Nuclear Transmutation Division] by Toshinobu SASA
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 GROUND SURVEY FOR THE HEART OF TRANSMUTATION PHYSICS EXPERIMENTAL 
FACILITY (TEF-P)

     To establish the Accelerator-driven System (ADS), a subcritical 
core is one of the key issues. Therefore, we proposed to construct a
subcritical assembly for understanding nuclear physical properties of 
ADS. The specific characteristic of TEF-P is capability to drive the 
subcritical core by volumetric spallation neutron source that is 
formed with 400 MeV or more injection proton energy delivered from 
J-PARC.
     After the Fukushima accident, the regulations of nuclear 
facilities including research reactors have been drastically 
strengthened. According to the latest regulations specified by the 
Nuclear Regulation Authority of Japan, a detailed ground survey to 
construct a critical assembly is required. The ADS Target Test 
Facility (TEF-T), which will be located beside the TEF-P, is not 
categorized as a nuclear facility but radiation application facility. 
It is also required to examine the safety impacts to TEF-P.
     In the national review working party held in 2014, the members of 
the working party accepted a prior ground survey for the entire TEF 
location. The ground survey was planned to be performed in two years. 
The exact location of the reactor is being excavated to judge 
stability for a nuclear reactor. The hole will be down to 300 meters. 
Three surrounding positions are also specified and examined down to 
40 meters. During excavation, several tests will be conducted to 
specify the quality of the soil layers. The measured characteristics 
of the soil layers will be used to analyze the earthquake-resistance 
of the TEF-P building and specific components related to safety. 
Further ground survey covering the TEF-T location will be planned in 
fiscal year 2016.


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6. [Safety Division] by Yukihiro MIYAMOTO and Kotaro BESSHO
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 THE PERIODICAL INSPECTION WAS SUCCESSFULLY CONDUCTED BY THE NUCLEAR 
SAFETY TECHNOLOGY CENTER (NUSTEC)

     The periodical inspection was successfully conducted and the 
certificate was issued on Dec. 8 by NUSTEC. The periodic inspection 
is taken once every five years to make sure that radiation 
installations are maintained in compliance with technical standards 
by the Radiation Hazards Prevention Law.

 AN EMERGENCY DRILL WAS HELD ASSUMING RADIATION EXPOSURE ACCIDENT

     An emergency drill was held on Nov. 13, in cooperation with the 
Nuclear Science Research Institute of Japan Atomic Energy Agency.
It was assumed that the beam operation was started without evacuating 
a worker in the accelerator tunnel of Main Ring and he suffered 
a neutron exposure of approximately 1 Gy. The drill included initial 
measures of the staff in responding to a variety of situations at the 
accident such as an estimation of exposure dose, transport to a 
medical facility by ambulance (simulated), and press releases.

 FISCAL 2015 J-PARC SAFETY AUDIT

     The fiscal 2015 J-PARC safety audit was conducted by outside 
auditors (Prof. Takano of Keio Univ. and Prof. Ishibashi of Kyushu 
Univ.) on Nov. 6. They heard the current status of safety management 
in J-PARC Center and various efforts by the facilities, and 
interviewed the director, the deputy directors, the managers of 
facilities and other staff members. They gave us valuable suggestions 
for the future safety efforts such as effective information exchange 
for the safety activities among the divisions. The safety management 
system will be improved in response to their suggestions. 


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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 
Junko BEANBLOSSOM (Secretary): beanblossom.junko at jaea.go.jp
++++++++++++++++End of Letter++++++++++++++++++++++++++++++++++++++++





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