The thermal conductivity of a hydrogen deuteride (HD) single crystal is measured at 3–7K for two mutually perpendicular directions of heat flow in the crystal. The HD sample is prepared by direct ...crystallization from ultra high-purity HD gas. A typical anisotropy with a ratio of nearly tenfold is obtained for the thermal conductivity in the measured temperature region. Approximate calculations of the anisotropic thermal conductivity in the HD crystal are performed using an analytical formulation of the two-dimensional anisotropic heat conduction, while taking into account cross-plane coupling of phonon Umklapp scattering. The approximate calculations are found to be in reasonable agreement with the experimental results.
The complete deuteron and triton polarization in the DT fusion increases the reactivity by 50%. For Inertial Confinement Fusion (ICF), due to the dynamics of the fusion reaction process, the fusion ...rate could even be further increased. It has been argued that the polarization would survive as well in magnetic as in inertial confinements. Recently, we have proposed an experiment to test the persistence of the polarization in a fusion process, using a powerful laser hitting a polarized HD target.The polarized deuterons heated in the plasma induced by the laser can fuse. The corresponding reaction is: D + D → 3He + n. The angular distribution of the emitted neutrons and the change in the corresponding total cross section are signatures to estimate the polarization persistency. A proposal to test the persistence of the polarization in ICF has been accepted at ILE: the POLAF project (POlarization in LAser Fusion Process). It uses the polarized HD targets produced at RCNP and the powerful ILE lasers, as well as the neutron detectors existing there. Both institutions are on the same campus at Osaka University. The description of the POLAF experiment and of the corresponding set-up is given.
Development of portable NMR polarimeter system for polarized HD target Ohta, T.; Fujiwara, M.; Fukuda, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2011, Letnik:
633, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A portable NMR polarimeter system has been developed to measure the polarization of a polarized Hydrogen-Deuteride (HD) target for hadron photoproduction experiments at SPring-8. The polarized HD ...target is produced at the Research Center for Nuclear Physics (RCNP), Osaka university and is transported to SPring-8. The HD polarization should be monitored at both places. We have constructed the portable NMR polarimeter system by replacing the devices in the conventional system with the software system with PCI eXtensions for Instrumentation (PXI). The weight of the NMR system is downsized from 80 to 7
kg, and the cost is reduced to 25%. We check the performance of the portable NMR polarimeter system. The signal-to-noise (
S/
N) ratio of the NMR signal for the portable system is about 50% of that for the conventional NMR system. This performance of the portable NMR system is proved to be compatible with the conventional NMR system for the polarization measurement.
Numerical simulations on the spin interferometry in transmission through magnetic resonators of very cold neutrons are performed with three different approaches of the conventional plane wave theory, ...the Schrödinger wave-packet model with a Gaussian packet structure, and of the recently proposed de Broglie wave-packet solution. Experiments are also carried out with a very cold neutron spin interferometer at a high flux reactor. The experimental results in tunneling resonance transmission agree better with the calculated results of the de Broglie wave-packet solution.
We report the first measurement of an angular correlation parameter in neutron beta decay using polarized ultracold neutrons (UCN). We utilize UCN with energies below about 200 neV, which we guide ...and store for approximately 30 s in a Cu decay volume. The interaction of the neutron magnetic dipole moment with a static 7 T field external to the decay volume provides a 420 neV potential energy barrier to the spin state parallel to the field, polarizing the UCN before they pass through an adiabatic fast passage spin flipper and enter a decay volume, situated within a 1 T field in a 2x2pi solenoidal spectrometer. We determine a value for the beta-asymmetry parameter A_{0}=-0.1138+/-0.0046+/-0.0021.
Theoretical solution for the de Broglie wave packet in subcritical condition for total reflection was obtained. The solution for the wave function shows characteristic features different from the ...results of the conventional plane wave analysis. The possibility to explain the reported anomalous reflection loss of ultracold neutrons in the storage experiment is indicated, and an estimation for the wave packet parameter from the magnitude of such a loss probability of 3×10
−5 for the beryllium bottle leads to the packet width of about 2 μm for the present solution of the de Broglie wave packet for the neutron.
We present the first measurements of the survival time of ultracold neutrons (UCNs) in solid deuterium (SD2). This critical parameter provides a fundamental limitation to the effectiveness of ...superthermal UCN sources that utilize solid ortho-deuterium as the source material. These measurements are performed utilizing a SD2 source coupled to a spallation source of neutrons, providing a demonstration of UCN production in this geometry and permitting systematic studies of the influence of thermal up-scatter and contamination with para-deuterium on the UCN survival time.
HD gas analysis with gas chromatography and quadrupole mass spectrometer Ohta, T.; Bouchigny, S.; Didelez, J.-P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2011, Letnik:
640, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A gas analyzer system has been developed to analyze Hydrogen–Deuteride (HD) gas for producing frozen-spin polarized HD targets, which are used for hadron photoproduction experiments at SPring-8. ...Small amounts of ortho-H
2 and para-D
2 gas mixtures (
∼
0.01
%
) in a purified HD gas are a key to realize a frozen-spin polarized target. However, there was an intrinsic difficulty to measure these small mixtures in the HD gas with a quadrupole mass spectrometer (QMS) because D
+ and H
2D
+ produced from the ionization of HD molecules were misidentified as H
2 and D
2 molecules, respectively, and became backgrounds for the measurement of the H
2 and D
2 concentrations. In addition, the ortho-H
2 and para-D
2 are not distinguished from the para-H
2 and ortho-D
2, respectively, with the QMS. In order to obtain reliable concentrations of these gas mixtures in the HD gas, we produced a new gas analyzer system combining two independent measurements with a gas chromatograph and the QMS. Helium or neon gas was used as a carrier gas for the gas chromatograph which was cooled at
∼
110
K
. The para-H
2, ortho-H
2, HD, and D
2 are separated using the retention time of the gas chromatograph and the mass/charge ratio. Although the para-D
2 is not separated from the ortho-D
2, the total amount of the D
2 is measured without the H
2D
+ background. The ortho-H
2 concentration is also measured separately from the D
+ background. It is found that the new gas analyzer system can measure small concentrations of
∼
0.01
%
for the ortho-H
2 and D
2 with good
S
/
N
ratios.
Ultracold neutrons (UCNs) are neutrons whose kinetic energy is around a few hundred nanoelectronvolts. Neutrons with such small kinetic energy can be trapped in a material vessel or magnetic fields. ...Because of these unique characteristics, UCNs are used for some important experiments of fundamental physics. The Doppler shifter is a device to produce UCN by slowing them down by the reflection on a mirror moving with half of the velocity of incoming neutrons. A Doppler shifter using a quadruple-stack of monochromatic supermirrors that reflects neutrons with a velocity around 68m/s 1, Hino et al.(2010) was fabricated, and operated with a pulsed neutron source of J-PARC. An important feature of the Doppler shifter is the use of a pulsed neutron beam. Unlike in continuous neutron beams, the neutron velocity can be selected by choosing a time slice in a pulsed neutron bunch. Thus the UCN production improves by ~80 times in the case of J-PARC. We successfully produced the UCNs by the Doppler shifter: the measured UCN production rate is consistent with the simulations.
A new materials irradiation facility at the Kyoto university reactor Yoshiie, T; Hayashi, Y; Yanagita, S ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2003, Letnik:
498, Številka:
1
Journal Article
Recenzirano
A new materials irradiation facility with improved control capabilities has been installed at the Kyoto University Reactor (KUR). Several deficiencies of conventional fission neutron material ...irradiation systems have been corrected. The specimen temperature is controlled both by an electric heater and by the helium pressure in the irradiation tube without exposure to neutrons at temperatures different from the design test conditions. The neutron spectrum is varied by the irradiation position. Irradiation dose is changed by pulling the irradiation capsule up and down during irradiation. Several characteristics of the irradiation field were measured. The typical irradiation intensity is 9.4×10
12
n/cm
2
s (>0.1
MeV) and the irradiation temperature of specimens is controllable from 363 to 773
K with a precision of ±2
K.
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