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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=3D22&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@kek.jp
Kaoru SHIBATA: shibata.kaoru@ jaea.go.jp
Takashi ITO: itou.takashi@jaea.go.jp
Dick MISCHKE (English Editor): mischke@triumf.ca
Tomoko KAWAMURA (Secretary): kawamura.tomoko@jaea.go.jp
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