Masahiko Utsuro

POLARIZED HD TARGET FOR FUTURE LEPS EXPERIMENTS AT SPRING-8 IN JAPAN

We are carrying out hadron photoproduction experiments by using polarized photon beams with energies of 1.5-2.9 GeV at SPring-8 in Japan. In 2005, we started developing a polarized HD target for future LEPS experiments using both the polarized photon beams and the polarized target. To introduce a polarized target plays an important role in upgrading the LEPS experiments to the next higher step. The measurement of double polarization asymmetries is expected to give important informations to investigate the nucleon hidden structure, hadron photoproduction dynamics, and exotic hadron property. We report on the present status of the development of the polarized HD target at RCNP. We will carry out a test experiment to confirm that the polarized HD target can be transported from Osaka university to SPring-8 without any problems in 2010. If we succeed in the test experiment, we will carry out a long experiment to take physics data in 2011-2012.

HD gas analysis with Gas Chromatography and Quadrupole Mass Spectrometer

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-H2 and para-D2 gas mixtures (�0.01%) in the purified HD gas are a key to realize a frozen-spin polarized target. However, there was an intrinsic diffi culty to measure these small mixtures in the HD gas with a quadrupole mass spectrometer (QMS) because D + and [H2D] + produced from the ionization of HD molecules were misidentified as H 2 and D2 molecules, respectively, and became backgrounds for the measurement of the H2 and D2 concentrations. In addition, the ortho-H 2 and para-D2 are not distinguished from the para-H2 and ortho-D2, 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 the gas chromatography and the QMS. Helium or neon gas was used as a carrier gas for the gas chromatography which was cooled at�110 K. The para-H2, ortho-H2, HD, and D2 are separated using the retention time of the gas chromatography and the mass/charge ratio. Although the para-D2 is not separated from the ortho-D2, the total amount of the D2 is measured without the [H2D] + background. The ortho-H2 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 otho-H2 and D2 with good S/N ratios.

Experimental Test of the Polarization Persistence in Inertial Confinement Fusion

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.