Study of the spin-dependence of three-nucleon interactions by developing a high-intensity polarized neutron beam

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In order to study the spin-dependence of three-nucleon interaction via elastic scatterings of spin-polarized neutron off deuteron, we have developed a highly intense but inexpensive spin-polarized proton source. In this proposal, an atomic beam of polarized hydrogen is produced by exchanging spins with Rubidium vapor, which is polarized with optical pumping by a circularly polarized laser, and then ionized by an ECR ionizer. In the first year of the term, mainly the polarized Rubidium vapor generating system has been developed It is crucial to match the spectral widths between the high-intensity laser and the absorption of Rubidium vapor so that the laser power is efficiently absorbed and accordingly a high polarization and a high vapor pressure can be achieved at the same time. Although high-intensity semiconductor lasers are available at low prices in this spectral region, their widths are usually of order of 1 THz, which is thousand times broader than the Doppler width of 1 GHz, res … More ulting in very poor absorption efficiency. Conventionally very expensive Ti-Sapphire lasers are used for this purpose, employing optical modulators to broaden their extremely narrow widths. Although semiconductor lasers with external cavities are commercially available, they have 1 MHz super-narrow widths and a few mW small powers, as they are usually focused to spectroscopic use. Thus we have developed a laser system suitable for optical pumping, with a broader width of 100 MHz and a high power of 1 W, by employing a Fabry-Perot type external cavity instead of the ordinary grating type. A feedback system for stabilizing the wavelength in a long term and an atomic beam system has been developed in parallel. In the second year of the term, the superconducting ECR ion source started operation and various improVements have been made, e.g., in the beam extraction part and in the beam transport system, by using heavy noble gases. Although the acceleration of polarized ion beam has not been achieved in the term, the system will be completed in the near future, together with the development of polarimeters. Also closer collaboration with theoreticians has been promoted by holding several workshops. Less