- Email: [email protected]
J-PARC and new era of science
ARTICLE IN PRESS
Nuclear Instruments and Methods in Physics Research A 562 (2006) 548–552 www.elsevier.com/locate/nima
J-PARC and new era of science Yukio Oyama Japan Atomic Energy Research Institute, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195, Japan Available online 9 March 2006
Abstract High Intensity Proton Accelerator Project promoted jointly by Japan Atomic Energy research Institute (JAERI) and High Energy Accelerator Research Organization (KEK), named as Japan Proton Accelerator Research Complex (J-PARC) was started on 1 April, 2001. The accelerator complex of J-PARC consists of three accelerators: 400 MeV Linac, 3 GeV rapid cycle synchrotron and 50 GeV synchrotron, and three major experimental facilities: Material & Life Science Facility, Nuclear & Particle Physics Facilities (Hadron and Neutrino Facilities) and Nuclear Transmutation Experiment Facility. r 2006 Elsevier B.V. All rights reserved. PACS: 29.17.tw; 29.20.c; 29.25.t Keywords: Proton accelerator facility; Linac; Synchrotron; Spallation source; Neutron; Muon; Meson; Neutrino; Accelerator driven system
1. Introduction High Intensity Proton Accelerator Project promoted jointly by Japan Atomic Energy research Institute (JAERI) and High Energy Accelerator Research Organization (KEK), named Japan Proton Accelerator Research Complex (J-PARC) was started on 1 April, 2001. The project was merged from the projects promoted so far by the both institutes, called Neutron Science Project (NSP) and Japan Hadron Facility (JHF) Project, respectively. The both projects were based on proton accelerators, and aimed at utilizing secondary particles produced from high-energy proton reactions. The NSP aimed at promoting researches to be developed by utilizing neutrons produced 1.5 GeV maximum and 8 MW protons, such as nuclear transmutation technology, material irradiation study, isotope production and so on. On the other hand, the JHF was focusing on fundamental researches mainly for nuclear physics relevant to hadron beam produced by 50 GeV maximum and 0.6 MW protons, combined with parasitic
Tel.: +81 29 282 6809; fax: +81 29 282 5996.
E-mail address: [email protected]. 0168-9002/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2006.02.139
use of neutron, muon, unstable nuclei produced by lowerenergy protons. The J-PARC project were planned to satisfy the purpose of two projects by optimizing the both facility concepts as 50 GeV and 1 MW with upgradeable to 5 MW. The accelerator complex of J-PARC consists of three accelerators: 400 MeV Linac, 3 GeV rapid cycle synchrotron and 50 GeV synchrotron, and four major experimental facilities: Material & Life Science Facility (MLF), Nuclear & Particle Physics (NP) Facility (Hadron facility and Neutrino facility), and Nuclear Transmutation Experiment Facility (TEF) [1]. At the current construction phase, Phase-I, those facilities except for Nuclear Transmutation Experiment Facility are being progressed. The accelerators will be completed in JFY2007 with 200 MeV Linac, and an operation for users will start at the time. The Neutrino facility will be completed one year later. The 200–400 MeV part of linac will be constructed in JFY2008-10 to increase proton beam power toward 1 MW goal. The second phase facilities including a 400–600 MeV superconducting linac, Nuclear Transmutation Experimental Facility, and some upgrades of Phase-I facilities will start soon after Phase-I completion, according to the review by the government.
ARTICLE IN PRESS Y. Oyama / Nuclear Instruments and Methods in Physics Research A 562 (2006) 548–552
2. J-PARC: Multi-purpose particle beam facility as a platform of science 2.1. J-PARC facility concept Figs. 1 and 2 show the J-PARC facility concept. The merit by combining the different projects is to be able to use common proton accelerators for high-energy acceleration, but twice of the accelerator power is necessary. For the J-PARC accelerators, the acceleration energies were divided into three regions and the type of accelerator was chosen according to the user requirements for operation mode. A linac was adopted for the first-stage accelerator and its energy was selected to 400 MeV and the repetition rate is 50 Hz. A half of repetition beam is used for a nuclear transmutation study and another is used for injection to a 3 GeV synchrotron. The energy of 400 MeV is also selected to be suitable for 1MW injection. On the other hand, the nuclear transmutation study requires longer pulse because a future commercial system will be operated in continuous beam mode to avoid a heat stress cycle. The second stage accelerator is a 3 GeV synchrotron used for muon and neutron researches and for injection to 50 GeV synchrotron. This energy was chosen because the neutron generation efficiency becomes maximized at
Fig. 1. J-PARC facility concept.
1–3 GeV and also one tenth of the 50 GeV is a suitable energy for injection to the 50 GeV synchrotron. In addition, the muon and neutron researches requires short pulses less than a micro-second, so synchrotron works as a device for beam storage and compression. The last stage is a 50 GeV synchrotron and the energy more than 30 GeV is required from the users. Because the yields of secondary particles from proton reactions are proportional to the beam power, the energy and power were set at 50 GeV and 0.75 MW as a goal. As mentioned above, a proton beam can be used for different ways at different acceleration stages. Therefore, this type of multi-purpose accelerator facility is very effective and cost conscious. In particular, high-power accelerators and experimental facilities for different energy regions allow us to make the accelerator complex a platform of various kinds of scientific researches with a world’s highest performance. For example, material researchers for nuclear transmutation study could use neutron scattering or muon techniques at J-APRC. Various scientists will cross over various research fields at this platform facility, and then new science will be born as a result. 2.2. Accelerator design Several kinds of linac accelerators to 400 MeV of proton energy are lined up [2]. The negative ions with more than 50 mA are accelerated by Radio-Frequency Quadrupole (RFQ) linac, Drift Tube Linac (DTL), Separated Drift Tube Linac (SDTL) and Annular-ring Coupled Structure (ACS) linac. A Super-Conducting Cavity (SCC) linac of 400–600 MeV range can be followed toward the nuclear transmutation facility as one of key technology development for accelerator driven system (ADS). A basic operation mode will be done by 50 Hz with the pulse width of 500 ms, and by dividing into two beams with 25 Hz each, i.e., toward the 3 GeV synchrotron and the SCC. Proton beams at 3 GeV Rapid Cycle Synchrotron (RCS) are accelerated along the 350 m circumference of the ring with the pulse width of 784 ns of two bunches and the
Phase 1 3 GeVSynchrotron (25Hz)
Phase 2
549
HadronExperimental Facility
Material andLife Experimental Facility
Nuclear Transmutation Linac (SuperConducting) Linac (Normal Conducting)
50GeV Synchrotron Neutrinos to SpuerKamiokande
Fig. 2. Schematic drawing of the J-PARC facility arrangement.
ARTICLE IN PRESS 550
Y. Oyama / Nuclear Instruments and Methods in Physics Research A 562 (2006) 548–552
average current of 333 mA. The RCS consists of 24 bending magnets and 60 quadrupole magnets. Negative hydrogen ions are converted to positive ions by carbon charge stripping foils at the injection point. The accelerated proton beam is extracted to MLF and the 50 GeV synchrotron (MR: Main Ring) with the extraction ratio of 80 vs. 4. Thus the injection rate to MR is 0.3 Hz. The average proton beam current of MR is 15 mA. There are 98 bending magnets and 216 quadrupole magnets along 1600 m circumference of the ring. The proton beam is extracted by two ways, i.e., slow and fast extractions. The slow one is for the Hadron facility and the fast one by fast switching magnet for the Neutrino facility.
2.3. Target stations The J-PARC experimental facilities are based on various kinds of secondary particle sources, such as neutron, muon, pion, K-meson, neutrino, anti-proton, and so on. These particles are generated by different target materials and station designs, according to particles. The MLF consists of muon and neutron target stations [3]. A 5% of proton beam is used at the muon target and the rest of beam is introduced to the neutron target. Neutron target station consists of a fluid mercury target with 1 m/s mercury flow which could be persistent to 3 GeV–1 MW beam power. However, pressure wave caused by spontaneous heat release by proton beam in the mercury is one of most significant limit for the life of the container materials. The pressure wave will generate bubble cavitations just at inner surface of the container wall and the pitting erosion will take place. This phenomenon has been intensively studied and clarified [4]. For use of neutron scattering research, it is necessary to decelerate neutron energy less than eV range. For this purpose, a liquid hydrogen moderator is used at 20 K. The obtained thermal neutron flux is expected to be 5 108 n/s/cm2 at 10 m distance from the moderator. Muon target uses a rotating target system. The muon station is placed just in front of neutron mercury target and use a graphite wheel with 20 mm in thickness and 250 mm of the inner diameter. The produced muons are collected to muon channels by solenoid magnets with the intensity of 3 107/s. In the hadron facility, the target is also a rotating type and made by a nickel disk with 54 mm in thickness and 500 mm in diameter to produce K-meson beam. The K-meson intensity is expected to be 1.3 107 ppp. In the neutrino facility, neutrino beam is obtained from decay of pion produced by proton–carbon reaction. The graphite rod with 30 mm in diameter and 900 mm in length is used for the target. The emitted pions are focused to forward direction by a horn magnet to make strong pulsed ring magnetic field. The neutrino beam intensity by 0.75 MW proton beam is about 2 1012/s within 41 corn, which corresponds to 3 107/s neutrinos passing through the
KAMIOKNDE detector at the distance of 295 km from J-PARC. 3. Science opened at J-PARC 3.1. Science opened by an intense secondary beam source Secondary particles produced by high-energetic proton reactions are usually unstable and thus do not exist in nature except for cosmic rays. These particles are neutron, muon, pion, K-meson, neutrino, anti-proton, and so on. The quantum properties of those particles give us unique tools especially for materials research as probes to investigate inside the matter. For examples, low-energy neutrons behave as a wave and make interference pattern like X-rays, and the anisotropic electron emission against a spin orientation in b-decay of muon can give us information of magnetic field inside materials. K-meson is also rare particles and brings the strangeness into nucleus. However, the intensity of the secondary particles, i.e., the intensity of proton beam is essential to make those researches effective, in the sense that the signal strength is proportional to the number of the probe. The intensity of secondary particles is generally proportional to beam power, i.e., beam energy multiplied by beam current. The power of J-PARC is 1 MW and more than one order higher than the existing facilities in the world. 3.2. Materials and life science by neutron and muon Muon is used to investigate magnetic interaction inside the materials by muon spin resonance or rotation (mSR) techniques, which is especially sensitive in the time range of 109–105 s between neutron scattering and NMR techniques. Another area is basic physics. Muon is similar particle to electron but the weight is 200 times larger. This causes muon orbit closer to nucleus, then it shows relativistic effect to directly demonstrate the theory. Neutrons behave like a wave at low energy less than eV as well known de-Broglie wave, and makes diffraction pattern through the interaction with condensed matter in similar way of X-ray diffraction. Neutron diffraction has some features superior to X-ray diffraction: (1) neutron has spin and magnetic moment, i.e., sensitive to magnetic structure, (2) cross section does not depend on atomic number, i.e., relatively sensitive to light elements compare to X-rays, and (3) penetrate more deeply in a sample. First one gives us information on magnetic property, second one on positions of hydrogen or light elements which cannot easily seen by X-ray diffraction and third one on residual stress distribution inside the bulk materials. For example, the hydrogen positions of Lysozyme protein were clearly determined by neutron diffraction as the first result in the world. In addition, a specific feature of neutron is that it allows us to observe dynamics and structural change of compounds and liquids by inelastic scattering due to the energy sensitivity higher than the X-ray or synchrotron
ARTICLE IN PRESS Y. Oyama / Nuclear Instruments and Methods in Physics Research A 562 (2006) 548–552
radiation. Using high intense neutrons, it is expected that new materials will be developed for industrial products such as superconducting materials, high dense magnetic memories, long-life batteries, medicines and so on. 3.3. Nuclear and particle physics by meson and neutrino In nuclear physics, the present questions about how mass of matter is created will be researched using meson implanting to nuclei. In the case of nucleons total mass of free nucleons is heavier than nuclei with the same number of nucleons. This is well known by mass defect. On the other hand, in the case of quarks a relationship is completely reverse, i.e., free quarks are 100 times lighter than the bounded quarks. Another question is why quarks can be contained in such a small volume of 1013 cm3. These questions are studied by implanting mesons into nuclei. Also implanting K-meson the strangeness is brought into nucleus called hypernucleus. These studies are called ‘‘nuclear matter physics’’ symbolically. Another urgent question is neutrino oscillation. There are three kinds of neutrinos and those can be mixed if they have mass. This means if they have mass, they changed into each other during flight. For observing this phenomenon clearly, J-PARC will emit m-neutrino beam to SuperKamiokande detector that is a huge pure water tank detector at a distance from 295 km from the J-PARC site (T2 K experiment). The m–t neutrino change was almost confirmed by KEK to Kamioka (K2 K) experiment, but J-PARC will precisely determine the parameters. Then the next interest by the T2 K experiment will be the probability of the m–e neutrino change. 3.4. Nuclear transmutation technology by fast neutron From reprocessing of 1 kg of nuclear fuel for nuclear power plants, liquid waste containing 50 kg of high-level radioactive waste (HLW) are produced. This liquid HLW can be separated (partitioning) to long-lived nuclei and the others. The long-lived waste nuclei consists of 2 kg longlived fission products, such as Tc-99 (T 1=2 ¼ 2:1 105 y) and I-129 (T 1=2 ¼ 1:6 107 y), and 1 kg minor actinides
551
such as Np-237 (T 1=2 ¼ 2:14 y) and Am-241 (T 1=2 ¼ 432:7 y). When HLW goes to deep geological disposal, those nuclides remain and become essential after long storage period, e.g., a few hundred thousand years later. If these long-lived nuclei can be changed to short-lived nuclei or stable nuclei, the severe requirement for geological storage technology can be reduced. For that purpose, a nuclear transmutation technology is proposed with an accelerator neutron source driven sub-critical system, so called ADS. By a simple calculation for 800 MWt sub-critical system, a 250 kg of MA, corresponding to MA produced from 10 nuclear power plants with 1 Gwe, can be converted to short-lived or stable nuclei, of which the effective half-life is about 500 yr. This sub-critical system will be assembled by MA fuels, and a high-energy and high-power accelerator will be used as the external neutron source. In this case, the accelerator is required for more than 1 GeV energy and a 10 mA of beam current. The first step of research and development for physics and engineering of a demonstration ADS system will be carried out at the J-PARC facility. These researches are reactor physics of sub-critical core, controllability of nuclear power and distribution, effectiveness of transmutation, materials technology, and so on.
4. Progress of J-PARC construction A photo of the construction site at the beginning of 2005 from an airplane is shown in Fig. 3 [5]. The conventional facilities up to the 3 GeV synchrotron have already been completed, except for the 50 GeV synchrotron tunnels. An accelerator installation started at July 2005. The construction of the Neutrino facility has just started in JFY2004 and a part of the pion decay tube (called as decay volume) under a proton beam transport to MLF was completed. A beam commissioning is planned to start at the mid of 2006 from the linac and in the spring of 2007 for the RCS. The MLF buildings will be completed in 2007 and the commissioning of neutron source too. In the meanwhile, the fabrication for neutron experimental devices will start according to the budget request,
Fig. 3. A photo of the J-PARC construction site at Tokai on January 2005.
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Y. Oyama / Nuclear Instruments and Methods in Physics Research A 562 (2006) 548–552
especially for two by the local government. The facility management will be done jointly by the both JAERI and KEK, so that a basic agreement of organization is under discussion. 5. Concluding remarks The power of J-PARC is more than one order higher than the existing facilities in the world, and also secondary beams will be well controlled, so that we should call this technology frontier of an accelerator facility ‘‘quantum beam technology’’. In a few years, J-PARC will start the user operation. Because the science to be performed at MLF is strongly connected to the development of various device materials and medicines, we should pay much attention for industrial application. At the same time, J-PARC is expected to be a platform facility serving to a wide range of users, from academic and industrial users, and a base of quantum beam technology development.
Acknowledgments The author would like to thank the JAERI-KEK joint project team of J-PARC for their cooperation. References [1] The Joint Project Team, High intensity proton accelerator project, JAERI-Tech 2000-003/KEK Report 99-5, 2000 (in Japanese); See also The Joint Project for High-intensity proton accelerators, JAERI-Tech 056/KEK Report 99-4 1999. [2] High-Intensity Proton Accelerator Project Team, Accelerator technical design report for high-intensity proton accelerator facility project, J-PARC, JAERI-Tech 2003-044/KEK Report 2002-13, 2003. [3] High-Intensity Proton Accelerator Project Team, Technical design report of material & life science facility for high-intensity proton accelerator facility project, J-PARC, JAERI-Tech 2004-001, 2003 (in Japanese). [4] M. Futakawa, T. Naoe, H. Kogawa, C. Tsai, Y. Ikeda, J. Nucl. Sci. Technol. 40 (11) (2004) 895. [5] JAERI and KEK joint project team, Web site of J-PARC project, http://j-parc.jp.
Nuclear Instruments and Methods in Physics Research A 562 (2006) 548–552 www.elsevier.com/locate/nima
J-PARC and new era of science Yukio Oyama Japan Atomic Energy Research Institute, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195, Japan Available online 9 March 2006
Abstract High Intensity Proton Accelerator Project promoted jointly by Japan Atomic Energy research Institute (JAERI) and High Energy Accelerator Research Organization (KEK), named as Japan Proton Accelerator Research Complex (J-PARC) was started on 1 April, 2001. The accelerator complex of J-PARC consists of three accelerators: 400 MeV Linac, 3 GeV rapid cycle synchrotron and 50 GeV synchrotron, and three major experimental facilities: Material & Life Science Facility, Nuclear & Particle Physics Facilities (Hadron and Neutrino Facilities) and Nuclear Transmutation Experiment Facility. r 2006 Elsevier B.V. All rights reserved. PACS: 29.17.tw; 29.20.c; 29.25.t Keywords: Proton accelerator facility; Linac; Synchrotron; Spallation source; Neutron; Muon; Meson; Neutrino; Accelerator driven system
1. Introduction High Intensity Proton Accelerator Project promoted jointly by Japan Atomic Energy research Institute (JAERI) and High Energy Accelerator Research Organization (KEK), named Japan Proton Accelerator Research Complex (J-PARC) was started on 1 April, 2001. The project was merged from the projects promoted so far by the both institutes, called Neutron Science Project (NSP) and Japan Hadron Facility (JHF) Project, respectively. The both projects were based on proton accelerators, and aimed at utilizing secondary particles produced from high-energy proton reactions. The NSP aimed at promoting researches to be developed by utilizing neutrons produced 1.5 GeV maximum and 8 MW protons, such as nuclear transmutation technology, material irradiation study, isotope production and so on. On the other hand, the JHF was focusing on fundamental researches mainly for nuclear physics relevant to hadron beam produced by 50 GeV maximum and 0.6 MW protons, combined with parasitic
Tel.: +81 29 282 6809; fax: +81 29 282 5996.
E-mail address: [email protected]. 0168-9002/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2006.02.139
use of neutron, muon, unstable nuclei produced by lowerenergy protons. The J-PARC project were planned to satisfy the purpose of two projects by optimizing the both facility concepts as 50 GeV and 1 MW with upgradeable to 5 MW. The accelerator complex of J-PARC consists of three accelerators: 400 MeV Linac, 3 GeV rapid cycle synchrotron and 50 GeV synchrotron, and four major experimental facilities: Material & Life Science Facility (MLF), Nuclear & Particle Physics (NP) Facility (Hadron facility and Neutrino facility), and Nuclear Transmutation Experiment Facility (TEF) [1]. At the current construction phase, Phase-I, those facilities except for Nuclear Transmutation Experiment Facility are being progressed. The accelerators will be completed in JFY2007 with 200 MeV Linac, and an operation for users will start at the time. The Neutrino facility will be completed one year later. The 200–400 MeV part of linac will be constructed in JFY2008-10 to increase proton beam power toward 1 MW goal. The second phase facilities including a 400–600 MeV superconducting linac, Nuclear Transmutation Experimental Facility, and some upgrades of Phase-I facilities will start soon after Phase-I completion, according to the review by the government.
ARTICLE IN PRESS Y. Oyama / Nuclear Instruments and Methods in Physics Research A 562 (2006) 548–552
2. J-PARC: Multi-purpose particle beam facility as a platform of science 2.1. J-PARC facility concept Figs. 1 and 2 show the J-PARC facility concept. The merit by combining the different projects is to be able to use common proton accelerators for high-energy acceleration, but twice of the accelerator power is necessary. For the J-PARC accelerators, the acceleration energies were divided into three regions and the type of accelerator was chosen according to the user requirements for operation mode. A linac was adopted for the first-stage accelerator and its energy was selected to 400 MeV and the repetition rate is 50 Hz. A half of repetition beam is used for a nuclear transmutation study and another is used for injection to a 3 GeV synchrotron. The energy of 400 MeV is also selected to be suitable for 1MW injection. On the other hand, the nuclear transmutation study requires longer pulse because a future commercial system will be operated in continuous beam mode to avoid a heat stress cycle. The second stage accelerator is a 3 GeV synchrotron used for muon and neutron researches and for injection to 50 GeV synchrotron. This energy was chosen because the neutron generation efficiency becomes maximized at
Fig. 1. J-PARC facility concept.
1–3 GeV and also one tenth of the 50 GeV is a suitable energy for injection to the 50 GeV synchrotron. In addition, the muon and neutron researches requires short pulses less than a micro-second, so synchrotron works as a device for beam storage and compression. The last stage is a 50 GeV synchrotron and the energy more than 30 GeV is required from the users. Because the yields of secondary particles from proton reactions are proportional to the beam power, the energy and power were set at 50 GeV and 0.75 MW as a goal. As mentioned above, a proton beam can be used for different ways at different acceleration stages. Therefore, this type of multi-purpose accelerator facility is very effective and cost conscious. In particular, high-power accelerators and experimental facilities for different energy regions allow us to make the accelerator complex a platform of various kinds of scientific researches with a world’s highest performance. For example, material researchers for nuclear transmutation study could use neutron scattering or muon techniques at J-APRC. Various scientists will cross over various research fields at this platform facility, and then new science will be born as a result. 2.2. Accelerator design Several kinds of linac accelerators to 400 MeV of proton energy are lined up [2]. The negative ions with more than 50 mA are accelerated by Radio-Frequency Quadrupole (RFQ) linac, Drift Tube Linac (DTL), Separated Drift Tube Linac (SDTL) and Annular-ring Coupled Structure (ACS) linac. A Super-Conducting Cavity (SCC) linac of 400–600 MeV range can be followed toward the nuclear transmutation facility as one of key technology development for accelerator driven system (ADS). A basic operation mode will be done by 50 Hz with the pulse width of 500 ms, and by dividing into two beams with 25 Hz each, i.e., toward the 3 GeV synchrotron and the SCC. Proton beams at 3 GeV Rapid Cycle Synchrotron (RCS) are accelerated along the 350 m circumference of the ring with the pulse width of 784 ns of two bunches and the
Phase 1 3 GeVSynchrotron (25Hz)
Phase 2
549
HadronExperimental Facility
Material andLife Experimental Facility
Nuclear Transmutation Linac (SuperConducting) Linac (Normal Conducting)
50GeV Synchrotron Neutrinos to SpuerKamiokande
Fig. 2. Schematic drawing of the J-PARC facility arrangement.
ARTICLE IN PRESS 550
Y. Oyama / Nuclear Instruments and Methods in Physics Research A 562 (2006) 548–552
average current of 333 mA. The RCS consists of 24 bending magnets and 60 quadrupole magnets. Negative hydrogen ions are converted to positive ions by carbon charge stripping foils at the injection point. The accelerated proton beam is extracted to MLF and the 50 GeV synchrotron (MR: Main Ring) with the extraction ratio of 80 vs. 4. Thus the injection rate to MR is 0.3 Hz. The average proton beam current of MR is 15 mA. There are 98 bending magnets and 216 quadrupole magnets along 1600 m circumference of the ring. The proton beam is extracted by two ways, i.e., slow and fast extractions. The slow one is for the Hadron facility and the fast one by fast switching magnet for the Neutrino facility.
2.3. Target stations The J-PARC experimental facilities are based on various kinds of secondary particle sources, such as neutron, muon, pion, K-meson, neutrino, anti-proton, and so on. These particles are generated by different target materials and station designs, according to particles. The MLF consists of muon and neutron target stations [3]. A 5% of proton beam is used at the muon target and the rest of beam is introduced to the neutron target. Neutron target station consists of a fluid mercury target with 1 m/s mercury flow which could be persistent to 3 GeV–1 MW beam power. However, pressure wave caused by spontaneous heat release by proton beam in the mercury is one of most significant limit for the life of the container materials. The pressure wave will generate bubble cavitations just at inner surface of the container wall and the pitting erosion will take place. This phenomenon has been intensively studied and clarified [4]. For use of neutron scattering research, it is necessary to decelerate neutron energy less than eV range. For this purpose, a liquid hydrogen moderator is used at 20 K. The obtained thermal neutron flux is expected to be 5 108 n/s/cm2 at 10 m distance from the moderator. Muon target uses a rotating target system. The muon station is placed just in front of neutron mercury target and use a graphite wheel with 20 mm in thickness and 250 mm of the inner diameter. The produced muons are collected to muon channels by solenoid magnets with the intensity of 3 107/s. In the hadron facility, the target is also a rotating type and made by a nickel disk with 54 mm in thickness and 500 mm in diameter to produce K-meson beam. The K-meson intensity is expected to be 1.3 107 ppp. In the neutrino facility, neutrino beam is obtained from decay of pion produced by proton–carbon reaction. The graphite rod with 30 mm in diameter and 900 mm in length is used for the target. The emitted pions are focused to forward direction by a horn magnet to make strong pulsed ring magnetic field. The neutrino beam intensity by 0.75 MW proton beam is about 2 1012/s within 41 corn, which corresponds to 3 107/s neutrinos passing through the
KAMIOKNDE detector at the distance of 295 km from J-PARC. 3. Science opened at J-PARC 3.1. Science opened by an intense secondary beam source Secondary particles produced by high-energetic proton reactions are usually unstable and thus do not exist in nature except for cosmic rays. These particles are neutron, muon, pion, K-meson, neutrino, anti-proton, and so on. The quantum properties of those particles give us unique tools especially for materials research as probes to investigate inside the matter. For examples, low-energy neutrons behave as a wave and make interference pattern like X-rays, and the anisotropic electron emission against a spin orientation in b-decay of muon can give us information of magnetic field inside materials. K-meson is also rare particles and brings the strangeness into nucleus. However, the intensity of the secondary particles, i.e., the intensity of proton beam is essential to make those researches effective, in the sense that the signal strength is proportional to the number of the probe. The intensity of secondary particles is generally proportional to beam power, i.e., beam energy multiplied by beam current. The power of J-PARC is 1 MW and more than one order higher than the existing facilities in the world. 3.2. Materials and life science by neutron and muon Muon is used to investigate magnetic interaction inside the materials by muon spin resonance or rotation (mSR) techniques, which is especially sensitive in the time range of 109–105 s between neutron scattering and NMR techniques. Another area is basic physics. Muon is similar particle to electron but the weight is 200 times larger. This causes muon orbit closer to nucleus, then it shows relativistic effect to directly demonstrate the theory. Neutrons behave like a wave at low energy less than eV as well known de-Broglie wave, and makes diffraction pattern through the interaction with condensed matter in similar way of X-ray diffraction. Neutron diffraction has some features superior to X-ray diffraction: (1) neutron has spin and magnetic moment, i.e., sensitive to magnetic structure, (2) cross section does not depend on atomic number, i.e., relatively sensitive to light elements compare to X-rays, and (3) penetrate more deeply in a sample. First one gives us information on magnetic property, second one on positions of hydrogen or light elements which cannot easily seen by X-ray diffraction and third one on residual stress distribution inside the bulk materials. For example, the hydrogen positions of Lysozyme protein were clearly determined by neutron diffraction as the first result in the world. In addition, a specific feature of neutron is that it allows us to observe dynamics and structural change of compounds and liquids by inelastic scattering due to the energy sensitivity higher than the X-ray or synchrotron
ARTICLE IN PRESS Y. Oyama / Nuclear Instruments and Methods in Physics Research A 562 (2006) 548–552
radiation. Using high intense neutrons, it is expected that new materials will be developed for industrial products such as superconducting materials, high dense magnetic memories, long-life batteries, medicines and so on. 3.3. Nuclear and particle physics by meson and neutrino In nuclear physics, the present questions about how mass of matter is created will be researched using meson implanting to nuclei. In the case of nucleons total mass of free nucleons is heavier than nuclei with the same number of nucleons. This is well known by mass defect. On the other hand, in the case of quarks a relationship is completely reverse, i.e., free quarks are 100 times lighter than the bounded quarks. Another question is why quarks can be contained in such a small volume of 1013 cm3. These questions are studied by implanting mesons into nuclei. Also implanting K-meson the strangeness is brought into nucleus called hypernucleus. These studies are called ‘‘nuclear matter physics’’ symbolically. Another urgent question is neutrino oscillation. There are three kinds of neutrinos and those can be mixed if they have mass. This means if they have mass, they changed into each other during flight. For observing this phenomenon clearly, J-PARC will emit m-neutrino beam to SuperKamiokande detector that is a huge pure water tank detector at a distance from 295 km from the J-PARC site (T2 K experiment). The m–t neutrino change was almost confirmed by KEK to Kamioka (K2 K) experiment, but J-PARC will precisely determine the parameters. Then the next interest by the T2 K experiment will be the probability of the m–e neutrino change. 3.4. Nuclear transmutation technology by fast neutron From reprocessing of 1 kg of nuclear fuel for nuclear power plants, liquid waste containing 50 kg of high-level radioactive waste (HLW) are produced. This liquid HLW can be separated (partitioning) to long-lived nuclei and the others. The long-lived waste nuclei consists of 2 kg longlived fission products, such as Tc-99 (T 1=2 ¼ 2:1 105 y) and I-129 (T 1=2 ¼ 1:6 107 y), and 1 kg minor actinides
551
such as Np-237 (T 1=2 ¼ 2:14 y) and Am-241 (T 1=2 ¼ 432:7 y). When HLW goes to deep geological disposal, those nuclides remain and become essential after long storage period, e.g., a few hundred thousand years later. If these long-lived nuclei can be changed to short-lived nuclei or stable nuclei, the severe requirement for geological storage technology can be reduced. For that purpose, a nuclear transmutation technology is proposed with an accelerator neutron source driven sub-critical system, so called ADS. By a simple calculation for 800 MWt sub-critical system, a 250 kg of MA, corresponding to MA produced from 10 nuclear power plants with 1 Gwe, can be converted to short-lived or stable nuclei, of which the effective half-life is about 500 yr. This sub-critical system will be assembled by MA fuels, and a high-energy and high-power accelerator will be used as the external neutron source. In this case, the accelerator is required for more than 1 GeV energy and a 10 mA of beam current. The first step of research and development for physics and engineering of a demonstration ADS system will be carried out at the J-PARC facility. These researches are reactor physics of sub-critical core, controllability of nuclear power and distribution, effectiveness of transmutation, materials technology, and so on.
4. Progress of J-PARC construction A photo of the construction site at the beginning of 2005 from an airplane is shown in Fig. 3 [5]. The conventional facilities up to the 3 GeV synchrotron have already been completed, except for the 50 GeV synchrotron tunnels. An accelerator installation started at July 2005. The construction of the Neutrino facility has just started in JFY2004 and a part of the pion decay tube (called as decay volume) under a proton beam transport to MLF was completed. A beam commissioning is planned to start at the mid of 2006 from the linac and in the spring of 2007 for the RCS. The MLF buildings will be completed in 2007 and the commissioning of neutron source too. In the meanwhile, the fabrication for neutron experimental devices will start according to the budget request,
Fig. 3. A photo of the J-PARC construction site at Tokai on January 2005.
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especially for two by the local government. The facility management will be done jointly by the both JAERI and KEK, so that a basic agreement of organization is under discussion. 5. Concluding remarks The power of J-PARC is more than one order higher than the existing facilities in the world, and also secondary beams will be well controlled, so that we should call this technology frontier of an accelerator facility ‘‘quantum beam technology’’. In a few years, J-PARC will start the user operation. Because the science to be performed at MLF is strongly connected to the development of various device materials and medicines, we should pay much attention for industrial application. At the same time, J-PARC is expected to be a platform facility serving to a wide range of users, from academic and industrial users, and a base of quantum beam technology development.
Acknowledgments The author would like to thank the JAERI-KEK joint project team of J-PARC for their cooperation. References [1] The Joint Project Team, High intensity proton accelerator project, JAERI-Tech 2000-003/KEK Report 99-5, 2000 (in Japanese); See also The Joint Project for High-intensity proton accelerators, JAERI-Tech 056/KEK Report 99-4 1999. [2] High-Intensity Proton Accelerator Project Team, Accelerator technical design report for high-intensity proton accelerator facility project, J-PARC, JAERI-Tech 2003-044/KEK Report 2002-13, 2003. [3] High-Intensity Proton Accelerator Project Team, Technical design report of material & life science facility for high-intensity proton accelerator facility project, J-PARC, JAERI-Tech 2004-001, 2003 (in Japanese). [4] M. Futakawa, T. Naoe, H. Kogawa, C. Tsai, Y. Ikeda, J. Nucl. Sci. Technol. 40 (11) (2004) 895. [5] JAERI and KEK joint project team, Web site of J-PARC project, http://j-parc.jp.