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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@kek.jp
Kaoru SHIBATA: shibata.kaoru@ jaea.go.jp
Takashi ITO: itou.takashi@jaea.go.jp
Dick MISCHKE (English Editor): mischke@triumf.ca
Junko BEANBLOSSOM (Secretary): beanblossom.junko@jaea.go.jp
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