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JAERI-KEK Joint Project Newsletter No. 1 July, 2000
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High Intensity Proton Accelerator Project proposed jointly
by the Japan Atomic Energy Research Institute (JAERI)
and the High Energy Accelerator Research Organization (KEK)
http://jkj.tokai.jaeri.go.jp/
Editorial Board:
Masatoshi ARAI (chair): masatoshi.arai@kek.jp
Tomokazu FUKUDA: tomokazu.fukuda@kek.jp
Yujiro IKEDA: ikeda@fnshp.tokai.jaeri.go.jp
Ganjiro MIZUMOTO: mizumoto@linac.tokai.jaeri.go.jp
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Contents
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0. Editorial Note (Masatoshi ARAI)
1. Status of the Joint Project between JAERI and KEK on High-Intensity
Proton Accelerators (Shoji NAGAMIYA)
2. Activities of the Accelerator Development Group (Yoshishige YAMAZAKI)
3. Report from the Nuclear and Particle Physics Group (Tomokazu FUKUDA)
4. Report from the Neutron Science Group (Susumu IKEDA)
5. Report from the Muon Science Group (Yasuhiro MIYAKE)
6. Report from the Accelerator Driven Transmutation Group (Yujiro IKEDA)
7. Activity of the Facilities Construction Group (Youichi AKUTSU)
8. Activity of the Radiaton Safety Group (Norio SASAMOTO)
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0. Editorial Note
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by Masatoshi ARAI
This is the 1st volume of the Joint Project Newsletter. We plan to
publish the Newsletter every 3 months. In order to inform everyone
of the current status of the project, we will send the Newsletter to
those who are listed in our data file of e-mail addresses. In case
you do not wish to receive this Newsletter in the future, please
send an email to majordomo@jkj.tokai.jaeri.go.jp and simply write
one sentence in the body of the message as "unsubscribe news-l".
In order to subscribe your email address, the sentence of the body
should be "subscribe news-l". You can get a help with a sentence of
"help" in the body.
Information on the project can be obtained also at the Web site:
http://jkj.tokai.jaeri.go.jp/
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1. Status of the Joint Project between JAERI and KEK on High-Intensity
Proton Accelerators
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by Shoji NAGAMIYA
Since this is the first volume of the Newsletter for the Joint Project
between JAERI and KEK on high-intensity proton accelerators, I will
describe the Joint Project itself, the past progress, and the present
status.
Originally, KEK (= High Energy Accelerator Research Organization) had a
hadron accelerator project called the Japan Hadron Facility (JHF), which
consisted of a 50-GeV proton synchrotron and a 3-GeV booster ring where
the projected power of the latter was 0.6 MW. On the other hand, JAERI
(= Japan Atomic Energy Research Institute) had a high-power spallation
neutron source project with a proton linac, in which 3-MW pulsed beams
were planned for neutron scattering and 5-MW continuous beams were
planned for nuclear transmutation. Since both projects have a common goal
to attain "high-power proton beams," in the summer of 1998 the Government
suggested a joint effort between KEK and JAERI for one proton facility
in Japan. As you might know, Monbu-sho (which supports KEK) and STA (=
Science and Technology Agency which supports JAERI) will merge together
to form one agency in January of 2001. Therefore, the suggestion made
in the summer of 1998 also had an implication that the Government wanted
to make a trial to promote one project supported by these two governmental
agencies.
Since then, a long discussion ensued between KEK and JAERI, and both
institutions finally agreed in March 1999 to make a cooperate effort to
create one high-intensity proton accelerator proposal. On March 18, 1999,
a formal MoU between KEK and JAERI was signed by the directors of these
two institutions. Subsequently, a Joint Proposal document was published,
and the project was reviewed in April 1999 by an International Committee,
which was chaired by Yanglai Cho (ANL). This Committee strongly endorsed
the Joint Proposal.
The project will be constructed at the JAERI/Tokai site and has the
following accelerator components:
1) A 400-MeV proton linac (normal conducting) to inject beams to the
3-GeV PS.
2) A superconducting linac to accelerate protons from 400 MeV to 600 MeV.
This machine will be used primarily for experiments toward nuclear
transmutation.
3) A 25-MHz 3-GeV proton synchrotron with 1 MW power. This will be used
primarily for life and material sciences with neutrons and muons.
4) A 50-GeV proton synchrotron with 15 microA. It has two extraction
modes:
a) slow extraction for kaon beams, pion beams and for primary beams,
and
b) fast extraction for neutrino beams to Super Kamiokande.
The total budget of the project is about 1,890 Oku Yen, where Oku is 100
millions (and, thus, approximately $1.89B when $1 = 100 Yen).
According to a new law in Japan, which was established very recently, any
big scientific project must pass a third-party review committee organized
by the Government. Here, the third-party committee must include a broad
body of people; professional scientists (physicists, chemists, biologists,
etc.), institutional administrators, journalists, economists, company
presidents, etc. Clearly, the Joint Project is a big project, so that this
project was assigned as a first example for the third-party review. The
committee members were assigned in the late fall of 1999. In so far, six
meetings have been held, and a draft of the final report was created
recently. According to the draft, the project is very strongly supported
by the committee, even though the project is expensive. This report will
strongly influence the policy decision of the project.
We thus hope that our project be approved officially for construction to
start in JFY2001 which starts in April 2001. Of course, both STA and
Monbu-sho (and both JAERI and KEK) are enthusiastic about this new Joint
Project. Also, scientific communities in Japan are supporting this Joint
Project strongly.
In the next issue of the Newsletter, I hope that I can report more details
on the advanced progress of this project. Note again that the project team
is presently working very hard everyday towards the official approval of
the Joint Project for JFY2001, as we believe that the chance of approval
is very high at this time.
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2. Activities of the Accelerator Development Group
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by Yoshishige YAMAZAKI
Here we summarize the accelerator scheme in more detail.
Phase I of the project comprises a 600-MeV linac, a 3-GeV, 1-MW
rapid-cycling synchrotron (RCS) and a 50-GeV main synchrotron. The Phase I
facility can be upgraded to a 5-MW neutron source, which will be Phase II
of the project.
One half of the 400-MeV beam from the linac is injected to the RCS, while
another half is further accelerated up to 600 MeV by a superconducting (SC)
linac. The 3-GeV beam from the RCS is injected to the 50-GeV synchrotron.
The 600-MeV beam accelerated by the SC linac is transported to the
experimental area for the accelerator-driven nuclear waste transmutation
system (ADS). The 3-GeV beam from the RCS is mainly used to produce pulsed
spallation neutrons and muons. The muon-production target and the
neutron-production target are respectively located in series in the Life
and Materials Science Experimental Area. Ten percent of the beam is used for
muon production. The 50-GeV beam is slow extracted to the Particle and
Nuclear Physics Experimental Area. It is also fast extracted for the
neutrino experiment, which is conducted at the Super Kamiokande detector
located 300 km distance from the Tokai site.
A volume-production type of negative hydrogen source is designed to produce
a peak current of 53 mA with a pulse length of 500 micro sec and a
repetition rate of 50 Hz. About 53 percent of the beam will be accelerated
after the beam is chopped at both the 50-keV low-energy beam transport
(LEBT) and the 3-MeV medium-energy beam transport (MEBT). The radio-
frequency quadrupole (RFQ) linac accelerates the beam up to 3 MeV, the
conventional drift-tube linac (DTL) up to 50 MeV, and the separated DTL
(SDTL) up to 200 MeV. An acceleration frequency of 324 MHz was chosen for
these. The frequency is increased by a factor of three at the energy of
200 MeV. Among the possible candidates for the coupled-cavity linac (CCL)
to be used from 200 MeV to 400 MeV, the annular-ring-coupled structure
(ACS) is most preferable for its axial symmetry. Several prototypes of
the L-band ACS have been developed and powered up to higher than the
designed value for the Japanese Hadron Facility (JHF).
The 400-MeV H- beam from the linac is injected to the RCS during the time
of 500 micro sec, which is limited by the flat bottom of the sinusoidally
varying magnetic field of the 25-Hz RCS. The beam is chopped at twice
the ring RF frequency of 1.36 MHz (thus, two bunches per ring) in order to
avoid beam loss during the injection process.
The RCS thus accelerates two bunches (4 x 10**13 protons per bunch) every
40 ms. Eight buckets among the ten buckets of the 50-GeV ring are filled
out by four cycles of the RCS (it takes 40 ms x 3). Then the 50-GeV
synchrotron is ramped up for 1.9 s. The beam is slowly extracted during the
time of 0.7 s. Afterwards, it takes 0.7 s for the synchrotron to be ready
for the next injection. In total, the period of one beam cycle is 3.42 s,
which corresponds to an average current of 15.4 micro A.
The linac is operated with a repetition rate of 50 Hz. The other half of the
beam is further accelerated up to 600 MeV by a superconducting linac for the
ADS experiment. The purpose of the SC linac is to develop the CW accelerator
technology necessary for the ADS. If the present scheme is successful, one
of the most important key technologies will be completed. If the future
development of the SC linac realizes the beam with delta-p/p 0.2 %, which is
required for the injection to the RCS, the 600-MeV beam will be injected to
the RCS in order to upgrade the beam power.
The construction of the 60-MeV proton linac has been already started for the
JHF in KEK site in 1998. The beam commissioning of the ion source and the
RFQ linac will be started by this fall. Since these two components were
designed for a peak current of 30 mA, they will be replaced in future for
the present project. However, the beam from these can be used for the beam
test of the DTL and SDTL by that time. After the construction and the beam
commissioning of the 60-MeV linac have been completed in collaboration
between JAERI and KEK, the linac will be shipped to Tokai site and used for
the Joint Project.
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3. Report from the Nuclear and Particle Physics Group
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by Tomokazu FUKUDA
The 50-GeV PS will provide high intensity secondary beams such as kaons,
pions, muons, and neutrinos and will present exciting opportunities in
nuclear and particle physics for the world scientific community. The
physics includes hypernuclear physics, rare decays, and neutrino physics
programs where Japanese physicists are world experts. In addition, various
kinds of physics with primary beams can be pursued.
High-resolution spectroscopy of hypernuclei with a large solid-angle
gamma detector will give us detailed information on the hyperon-nucleon
interaction as well as baryon properties inside nuclear matter. Studies
of strangeness -2 systems such as double-lambda hypernuclei and the
H-dibaryon will give the first steps for multi-strange systems, i.e.
"strange matter". Kaon rare decays, in particular K+ -> pi+ nu nubar and
K0L -> pi0 nu nubar, will provide good opportunities to study the Cabibbo-
Kobayashi-Maskawa (CKM) quark-mixing matrix. Together with studies using
the B-meson, clues to "new physics beyond the Standard Model" may be
found. The violation of the fundamental symmetries, such as CP and/or
T violation, and the lepton flavor violation, in particular rare muon
processes, are also important subjects. In neutrino physics, Japan has
recently provided the most credible evidence of possible neutrino oscillations
in the Super Kamiokande detector. A new experiment has started at KEK to
further confirm this hypothesis by sending a muon neutrino beam from KEK
to Super Kamiokande. Higher neutrino intensity at 50-GeV PS will enable us
to obtain more detailed information on the neutrino mass as well as lepton
flavour mixing. Concerning the physics with primary beams, one example of
the research is to study the interior of the nucleus by implanting vector
mesons like the omega, phi, and J/psi and observing the change of the mass
etc.
An experimental area for slow extraction and a neutrino beam line for
fast extraction will be constructed so as to accommodate such a broad
range of physics. The slow extraction area will be equipped with three
primary beam lines (A,B and C). The line A will produce high-intensity
secondary charged particle beams from two target stations and the line B
is considered for a neutral kaon beam at the moment. The line C will be
for primary beam physics. The details of the beam lines will be determined
according to experimental programs and the layout allows an extension
in the future.
Nuclear physics with radioactive nuclear beams, which is based on an ISOL
and a post-accelerator, has been considered but the facility will be
constructed in a later stage of the project.
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4. Report from the Neutron Science Group
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by Susumu IKEDA
We plan to construct a 1-MW pulsed spallation neutron source utilizing the
high intensity proton beam from the 3-GeV proton synchrotron (3 GeV, 333
microA, 25 Hz), which can provide considerably higher peak and higher
time-averaged neutron flux than existing facilities.
We are on the way to design a neutron generation target system including
the neutron generation target itself, the neutron moderator, and the
reflector. For the target, two types of mercury target and a heavy-water-
cooled solid target are now under conceptual design. The solid one is
considered as a backup option. The main technical issues for the target
are (1) structural integrity against the thermal shock, the pressure wave,
and the high heat density caused by the proton beam, (2) safety
performance to prevent an off-normal occurrence, and (3) remote handling
devices. In order to solve these issues, further R&D work as well as
design work is being pursued vigorously.
In addition, several useful experiments on the target design are
progressing under international collaborations with Brookhaven National
Laboratory and the Paul Scherrer Institute. Examples are a mercury target
mockup test and the proton beam irradiation test. With these activities,
the present concept for the mercury and the solid targets are expected to
be validated for 1-MW operation, and hopefully up to 2 MW.
For neutron moderators, we will install one coupled super critical
hydrogen moderator with a newly proposed fully extended pre-moderator and
two decoupled hydrogen moderators. All moderators are located around the
highest luminosity region above or below the target. The coupled one can
provide the high-intensity cold neutron beam. This is very useful for
small-angle experiments and reflectometers, etc. The decoupled ones can
realize high-energy-resolution neutron experiments in the cold and thermal,
as well as the epi-thermal energy regions.
The neutron beams of cold, thermal, and epi-thermal regions are taken out
through approximately 20-30 neutron beam lines, and are utilized by
eventually more than 30 spectrometers which will be installed in the
neutron experimental hall. However, several diffractometers or
spectrometers with extremely high resolution will be constructed outside
of the hall (at 100-150 m positions from the neutron source). The design
of these spectrometers and R&D experiments on novel devices, such as the
focus device, detectors, and polarizers, etc. are in progress.
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5. Report from the Muon Science Group
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by Yasuhiro MIYAKE
Muons can be used in various fields of scientific research including (1)
fundamental muon physics, such as precise measurements of particle
properties of muons, hunting for rare decays, etc., (2) muon catalyzed
fusion and its application to energy resource problems, (3) use of the
muon as a spin probe sensitive to the microscopic magnetic properties of
various new materials, and (4) non-destructive element analysis to be
applied to bio-medical studies, etc. All of these research subjects
will be strongly promoted by obtaining the world's most powerful muon
beam at the Joint Project in the 21st century.
Facility Proposal
The facilities for Muon Science are mainly aimed at the production of
pulsed muons, which will be generated by 3-GeV protons. Design work on
the advanced muon channel is in progress with the aim of producing beams,
which are not only the most intense so far, but also the highest in
quality. The proposed layout of the facility of Muon Science to be placed
in the upstream of the Neutron Science facility with two thin carbon
targets (10 mm and 20 mm) includes:
i) keV ultra-slow mu+ beam
The generation of ultra-slow mu+ as a result of (pulsed) laser resonant
ionization of thermal muonium (designated Mu) produced in vacuum from a hot
tungsten surface leads to an intense mu+ beam source of keV or lower energy
with an intensity of 10**4 mu+/s.
ii) 4 MeV surface mu+ beam
The conventional surface mu+ beam for muSR studies on condensed matter is
generated by the pi+ -> mu+ decay at the surface layer of the production
target in the primary proton beam line. An electrostatic kicker system with
an exact form depending upon the pulse structure, will be installed to feed
single pulses to specific experimental areas with a rate of 10**7 mu+/s;
iii) 10-100 MeV decay mu+/mu- beam
A superconducting decay muon channel with a modest-acceptance pion injector
will be constructed to produce intense (10**7 mu+- /s) high quality
backward decay muons. A magnetic kicker system at the extraction part of the
channel will allow single-pulse experiments.
iv) ultra-high intensity mu+/ mu- channel
Due to the requirement for a muon beam with a high intensity at the 10**10
mu+-/s level for some fundamental and applied physics experiments, design
work is in progress on a superconducting muon channel with ultra-large
spatial and momentum acceptance. A high field focusing superconducting
solenoid will be placed adjacent to the pion production target, although it
is intended to be installed in the second phase. Such a large-scale
installation of a superconducting magnet system will open new fields of
Muon Science.
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6. Report from the Accelerator Driven Transmutation Group
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by Yujiro IKEDA
To realize the accelerator-driven nuclear waste transmutation system (ADS),
various areas of fundamental research and technical development are
required. The issues involve spallation target technology, sub-critical
reactor physics, hybrid system operation and controls, the nuclear
transmutation process, thermal-hydraulics, and material developments, etc.
Among them, the development of the material for a proton beam window of the
spallation target and the sub-critical reactor physics driven by the high
energy proton beam are most important to evaluate the technical
feasibility for ADS. Under the JAERI-KEK joint project for the high
intensity proton accelerator, two experimental facilities for the ADS
nuclear transmutation experiment are proposed to be built for testing and
developing the technologies as a real step of the ADS development: (1)
Accelerator Material Irradiation Facility, and (2) ADS Physics Experimental
Facility. The accelerator of the Joint Project provides proton beams of
600 MeV with 0.33 mA (200 kW at maximum) to these facilities through the
superconducting Linac. This arrangement meets the basic requirements for
the primary missions of the experimental facilities. The Accelerator
Material Irradiation Facility is to be constructed to develop the material
of the beam window and the spallation target system. Identifying a
lead-bismuth (Pb-Bi) as the first candidate target/coolant material system,
irradiation tests of materials with the 600 MeV and 0.33 mA (200 kW) proton
beam and high intensity spallation neutrons will be performed. On a
preliminary evaluation, dose rates of more than 10 dpa (Displacement per
Atom) per year could be achieved in this facility by adjusting the proton
beam current density. By simulating the Pb-Bi flow condition in terms of
temperature and flow rate, important data of material compatibility, i.e.,
corrosion, erosion, etc., will be produced. The ADS Physics Experimental
Facility uses low power proton beam up to 10 W, which is picked up from
the 200 kW main beam by a laser charge exchanger. Basic sub-critical
reactor physics, e.g., sub-criticality, reactivity, power profile, etc.
and reactor power control with the beam power are to be studied. For this
purpose, a critical assembly with maximum reactor power of 500 W,
consisting of mainly 20%-enriched uranium fuels is to be constructed. It
will be the first demonstration anywhere in the world of the sustained
stable integral operation of a spallation target and a fast neutron sub-
critical core driven by a proton beam.
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7. Activity of the Facilities Construction Group
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by Youichi AKUTSU
Facilities construction group constituted by the JAERI Construction
Department (Construction Division and Installation Division) and the KEK
Facility Department (Architecture Section and Facility Section) was founded
in 1998 in order to make a rational construction plan of the Joint Project
Facility.
The activity of the group during the period of the last two years is as
follows:
1. In the forming of the group, various problems for promoting the
cooperative project were discussed and reviewed.
2. As the activity in 1998, design studies related to the site selection
and facility layout were carried out to merge two existing facility
plans, the JAERI Neutron Science Project planned in Tokai and the KEK
Japan Hadron Facilities planned in Tsukuba into a single rational
integrated facility layout.
3. In 1999, the master plan (building facilities, layout planning, tunnel
plan, utility plan, etc.) of the Joint Project was constructed.
The work on the cost estimation of the construction and cost reduction
of the whole facilities was simultaneously performed.
There is further work remaining to prepare for actual commencement of
construction, such as obtaining the understanding of local people who
live near the site, effective usage of the existing facilities, various
formal processes for application and permission to the authorities, and
planning for management of construction.
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8. Activity of the Radiaton Safety Group
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by Norio SASAMOTO
The radiation safety group of the project consists of the facility
safety group of JAERI and the radiation science center of KEK, partially
supported by the department of health physics of JAERI. The group is
responsible for the design of shielding for the facility, evaluation of its
radiation safety and construction of the safety control equipment. Getting
a license by the government through radiation safety evaluation is the major
job of the group.
In 1999 FY, a preliminary shielding design was carried out. The required
shield thickness was determined mainly using the Moyer model with KEK
parameters and the Stapleton's equation to meet the shielding design
criteria of 0.2 microSv/h outside the controlled area and 30 microSv/y at
the site boundary, together with the soil activation criterion around the
underground shielding walls. Also the amount of activation of air in the
proton accelerator tunnels and cooling water was obtained to predict the
amount of gaseous and liquid radioactive wastes.
Development and improvement of more sophisticated shielding design codes
for the coming detailed shielding designs have been made. Both a streaming
calculation code DUCT-III and a skyshine calculation code SHINE-III have
been improved to take account of energy components up to 3 GeV.
A conceptual study is in progress for the safety control equipment,
consisting of a radiation monitoring system and an access control system.
Improvement of a neutron monitor is also in progress to increase its
sensitivity in the higher energy region by adding a lead layer as a
moderator to existing monitors.
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