T. Nakashima

Rotating-disc type high voltage generator

Abstract A very compact electrostatic generator, making use of a rotating insulator disc equipped with charge-carrying metallic pieces in an SF 6 atmosphere, has been constructed and used for a preacceleration voltage source of a tandem accelerator. The maximum usable voltage is 400 kV, generating a current of 500 μA. The charge transfer to and from the moving charge carriers at the ground and high voltage terminals is performed by means of a contact with running conducting rubber belts.

Strong-focusing in tandem accelerator with alternating voltage gradient

Abstract A new method to obtain low-energy high-intensity beams from a tandem accelerator of a high design-voltage is presented. In this method, the beam undergoes repeated actions of acceleration and deceleration from alternating voltage gradient along the beam axis, so that the beam divergence is minimized. The practical test was carried out at the 10 MV tandem accelerator at Kyushu University, and the beam transmission efficiency at a low operation voltage of 1 MV was found to be an order of magnitude increased. The method also enables the accelerator to stand a high beam load. The necessary changes in the accelerator configuration are quite simple and easily achievable at a low cost.

Polarization monitors for proton and deuteron beams below 20 MeV

Abstract Two polarimeters for proton and deuteron beams using the p+ 4 He scattering and the 3 He(d, p) reaction, respectively, are described. They are placed downstream from a scattering chamber so as to monitor the beam polarization throughout an experiment. Two of the three components of proton spin and six of the eight components of deuteron spin can be measured simultaneously.

A high efficiency proton polarimeter using a liquid helium target

Abstract A high efficiency (−1 × 10 −3 at A y = −0.45) polarimeter used for a secondary proton beam of 14–18 MeV energy is described. The polarimeter target is liquid helium held in a conical cell. Protons scattered at 52° ± 8° are detected by twelve Si detectors placed symmetrically around the beam axis. This polarimeter has been used for polarization transfer studies.

Difference between nd Ay and pd Ay below 16 MeV

Analyzing power Ay(θ) of nd scattering was accurately measured at En=12 and 16 MeV. Polarization of the n-beam produced by spin transfer 2H(d,n)3He reaction at 0° was determined in a separate experiment using 4He(n,n) scattering. The present nd Ay(θ) data are consistent with the existing nd Ay(θ) data below En=14.1 MeV. It was confirmed that the difference between nd Ay and pd Ay becomes large above 14 MeV and the assumption on slow-down effects by Coulomb force breaks down. The observed large difference in Ay(θ) requires systematic calculations with exact treatment of Coulomb force to study charge symmetry in nuclear force.

Measurement of Axx, Ayy and Azz for p+d↘→3He+γ reaction at 17.5 MeV

Angular distributions of tensor analyzing powers Axx, Ayy and Azz of p+d↘→3He+γ reaction at Ed=17.5 MeV have been measured precisely. The experimental data on Ayy agree with a Faddeev calculation based on a realistic NN potential. However, Axx and Azz show apparent disagreements with the calculation, and the inclusion of a three‐nucleon force increases the disagreement.