Showing papers by "Japan Atomic Energy Research Institute published in 2013"

A multi-reflection time-of-flight mass spectrograph for short-lived and super-heavy nuclei

Abstract: A multi-reflection time-of-flight (MRTOF) mass spectrograph has been implemented at RIKEN to provide high-precision mass measurements of very short-lived nuclei. Of particular interest are mass measurements of r-process nuclei and trans-uranium nuclei. In such nuclei, the MRTOF can perform on par with or better than traditional Penning trap systems. We demonstrate that the MRTOF-MS is capable of accurately attaining relative mass precision of δ m / m 10 - 7 and describe it’s utility with heavy, short-lived nuclei.

Evolution of the ITER program and prospect for the next-step fusion DEMO reactors: status of the fusion energy R&D as ultimate source of energy

Abstract: An international joint project of fusion experimental reactor, the ITER (International Thermonuclear Experimental Reactor), is reviewed in view of long-range fusion energy research and development (R&D). Its purpose, goal, evolution, and the present construction status are briefly reviewed. While the ITER is a core machine in the present stage, generation of electricity is a role of the next-step fusion demonstration power plant “DEMO.” The status of designs and technology R&D for DEMO are also reviewed.

GAMMA 10/PDX Project Status and Future

Abstract: GAMMA 10/PDX project is the development of the mirror devices to aim the fusion-reactor relevant research using the potential control and the end loss as the particle and heat fluxes for transport,...

X Ray Diffraction Measurements in a Double-Stage Multianvil Apparatus Using ADC Anvils

Abstract: Anvils made of ADC (Advanced Diamond Composite) have been introduced for a double-stage multianvil system. Using a hybrid system for the second stage anvils, composed of four ADC and four WC cubes, we were able to produce pressures to 28 GPa and temperatures exceeding 1500°C. In situ X ray diffraction measurements on some minerals have been successfully performed with a combination of the present high pressure system and synchrotron radiation. Only in two runs some failures of ADC anvils have been observed out of more than 10 runs so far conducted using the MAX80 and MAX90 apparatus at the Photon Factory, National Laboratory for High Energy Physics (KEK). The present system may be used on a routine basis for experiments under pressures to 30 GPa, and at temperatures approaching 2000°C within the force capacity of these apparatus.

Development of high intensity linear accelerator for heavy ion inertial fusion driver

Abstract: In order to verify the direct plasma injection scheme (DPIS), an acceleration test was carried out in 2001 using a radio frequency quadrupole (RFQ) heavy ion linear accelerator (linac) and a CO2-laser ion source (LIS) (Okamura et al., 2002) [1] . The accelerated carbon beam was observed successfully and the obtained current was 9.22 mA for C4+. To confirm the capability of the DPIS, we succeeded in accelerating 60 mA carbon ions with the DPIS in 2004 (Okamura et al., 2004; Kashiwagi and Hattori, 2004) [2] , [3] . We have studied a multi-beam type RFQ with an interdigital-H (IH) cavity that has a power-efficient structure in the low energy region. We designed and manufactured a two-beam type RFQ linac as a prototype for the multi-beam type linac; the beam acceleration test of carbon beams showed that it successfully accelerated from 5 keV/u up to 60 keV/u with an output current of 108 mA (2×54 mA/channel) (Ishibashi et al., 2011) [4] . We believe that the acceleration techniques of DPIS and the multi-beam type IH-RFQ linac are technical breakthroughs for heavy-ion inertial confinement fusion (HIF). The conceptual design of the RF linac with these techniques for HIF is studied. New accelerator-systems using these techniques for the HIF basic experiment are being designed to accelerate 400 mA carbon ions using four-beam type IH-RFQ linacs with DPIS. A model with a four-beam acceleration cavity was designed and manufactured to establish the proof of principle (PoP) of the accelerator.

Competition between magnetic ordering and random spin freezing in Dy2PtS3

Abstract: We report the results for ac and dc susceptibility, magnetization, magnetic relaxation, specific heat and electrical resistivity measurements on a well annealed ternary intermetallic compound Dy2PtSi3. An unusual magnetic phase transition with an apparent ferromagnetic nature was observed at T C = 5.6 K. At temperatures below T C , however, Dy2PtSi3 showed a metastable magnetic behavior characteristic of a typical cluster glass. The classification of Dy2PtSi3 as a large magnetic cluster (extended short-range ferromagnetic ordered) system with competition between magnetic ordering and random spin freezing seems appropriate.

Diamagnetic Screening of Transverse Current Correlations and Neutron Scattering in Metals

Abstract: A general expression for the differential scattering cross section of neutrons by an electron system is considered in terms of the transverse current-current response function. Effect of the transverse fluctuating field on the transverse current-current response function· is found to be important. Such a calculation is made by using the transverse effective field approach formulated by Pines and Nozieres. The effect of the fluctuating transverse field appears in the final expression in the form of dynamic screening. This suppresses the other­ wise divergent differential cross section appreciably at smallest q of order hundredth of inverse Angstrom or less. orbital magnetism. Nevertheless, we are still left with several important pro­ blems to be settled, especially on the dynamic orbital magnetism. We have among them the problem of neutron scattering by orbital current carried by electrons in a metal. Neutron with nuclear spin 1/2 probes the magnetic field in a solid, which is fluctuating, generally, in space and time. This fluctuating field induces fluctuating current, and vice versa: the fluctuating magnetic field arises from the spontaneous motion of charged particles. As is well known, the total orbital current consists of two parts, paramagnetic and diamagnetic, and the latter depends linearly on the vector potential acting on the electrons that carry it. This dualism of orbital current should be considered carefully: the gauge invariance has to be maintained in any theoretical calculations. In this paper we try to construct the theory of neutron scattering by current fluctuation, taking account of the above point. We do it by follow­ ing the steps outlined below. In § 2 we represent the neutron scattering cross section in terms of the magnetic field-magnetic field correlation function, then express it in terms of the transverse current-current correlation function by making use of the exact microscopic Maxwell equation incorporating the electromagnetic fluctuations. The transverse current-current correlation function is related to the corres-

Cold test results of a side-coupled standing-wave electron-accelerating structure

Abstract: The radio-frequency (RF) cavity for the dual-energy S-band electron linear accelerator (LINAC) is designed for a cargo inspection system (CIS) at the Korea Atomic Energy Research Institute (KAERI). The cold test results of the electron accelerator structure, which has a side-coupled standing-wave interlaced-pulse dual-energy mode, are described. The design concept, basic structure, microwave-tuning method, and cold-test procedure are described as well. The measured dispersion curve, spectrum characteristics, ρ-f relation of the power coupler, and axial field distribution of the accelerating gradient are provided.

X ray diffraction analysis of molten KCl and KBr under pressure: Pressure-induced structural transition in melt

Abstract: The structures of molten KCl and KBr were studied by energy dispersive X ray diffraction experiments under high temperature and high pressure using synchrotron radiation. The radial distribution function g(r) for molten KCl and KBr was obtained at several points just above the melting temperatures up to 4 GPa. The second neighbor ionic distance decreases with pressure, although the nearest neighbor distance is almost constant. The coordination number of the nearest neighbor ions increases with pressure. Both melts transform from an open, simple-cubic-like structure into a more highly coordinated structure, probably a body-center-cubic-like structure. The structure of molten KCI changes before the crystalline phase but the molten KBr transforms into a dense phase about the same time as the solid. In both KCl and KBr melts the structural transition occurs over a narrow pressure range.

Charge-Transfer Cross Sections of Slow Doubly and Triply Charged Carbon Ions from CO and CO2 Molecules

Abstract: collisions with CO and CO2 molecules in the energy range of 035 to 30 keV per initial charge number based on the initial growth rate method Most of the present single- and multiple-charge-transfer cross sections show weak energy dependence over the observed collision energy range For CO2 molecules, the present data smoothly join with the previously measured data in the energy range greater than 10 keV The cross sections for total charge transfer, which are summations of single- and multiple-charge-transfer cross sections, are compared with a simple over-barrier model and available scaling laws

Effect of Neutron Attenuation on Strain Measurement with Large Gauge Volume

Abstract: When measuring residual strain distributions of thick structural components such as thick butt-welds using neutron diffraction, it is required to make a gauge volume larger as well as to shorten neutron path length in a material to obtain sufficient diffraction intensity. In this study, neutron attenuation effect on the strain measurement with a large gauge volume was discussed on the normal strain measurement of a thick butt-weld. Influences of neutron attenuation like an apparent strain change were observed, and it was more noticeable when the gauge volume becomes larger. Therefore, the neutron attenuation effect should be considered in the strain measurement with a large gauge volume, and the neutron absorption corrections certainly play an important role for improvement of reliabilities of strain measurement using neutron diffraction with a large gauge volume.

Three-Body ΛNN → nNN Nonmesonic Weak Decay Process of Λ Hypernuclei

Abstract: The fundamental motivation to study the non-mesonic weak decay (NMWD) of Λ hypernuclei is that it provides the unique channel for the information of the baryon–baryon weak interaction in SU3f group. The relative strength of the two main channels of NMWD whose decay processes are the Λp → np and Λn → nn has been the long standing puzzle during last several decades. The puzzling status has been settled down recently with the Γn / Γp value converging to \({\sim 0.5}\) . The large experimental values of Γn / Γp of the previous measurements turned out to be due to the surprisingly large contribution of the competing three-body NMWD, ΛNN → nNN process. This paper discusses about the first measurement of the branching ratio of the three-body NMWD process and the renormalized intra-nuclear cascade method adopted to disentangle the contribution of the three-body process out of those due to final state interaction. And the prospects of the more accurate measurement of the three-body process also are presented.