Yoshinori Hashimoto

Multi-pole magnets to focus an O2 sheet beam for a non-destructive beam-profile monitor

Abstract An oxygen molecular sheet beam was generated using the nozzle beam method, focused with multi-pole magnets, and was then used as the target of a non-destructive beam-profile monitor. The method used for focusing the sheet beam with multi-pole magnets is based on the fact that an oxygen molecule has a magnetic moment as large as two Bohr magnetons and a spin of 1. Using focusing magnets, the density of an oxygen sheet beam at the median plane increased up to about twice compared with the value obtained without focusing magnets. The principle of focusing and the focusing multi-pole magnets have been studied.

Development of a nondestructive beam profile monitor using a gas sheet

A nondestructive beam profile monitor using a neutral gas sheet is developed for ion synchrotron beams. To produce the intense gas sheet, a nozzle beam method is employed. The typical sizes of the sheet are 100 mm width and 1 mm thickness. Up to now the pressure of the gas sheet has been achieved 5/spl times/10/sup -7/ Torr. As the sheet is inclined 45 degrees in the transverse direction to the beam, a cross-sectional profile of the beam would be measured. As a performance test, a profile of an extracted proton beam from NIRS-Cyclotron was successfully measured.

Optics Tuning for Beam Collimation in the J-PARC 3-50 Beam Transport Line

The Japan Proton Accelerator Research Complex (J-PARC) 3-50 Beam Transport line (3-50BT) is a beam transport line from 3-GeV rapid-cycling synchrotron (RCS) to 50-GeV main ring (MR). The RCS is a high-intensity proton accelerator, where the designed beam power is 1 MW, and has the complex source of space charge effect and beam instability, etc. Therefore, the uncontrolled emittance growth and beam halo increase nonlinearly with the beam power ramp up. Additionally, the physical aperture of 81  mm mrad in the MR is smaller than physical aperture of 486  mm mrad in the RCS. Therefore, the 3-50BT line has the collimators in order to remove the unwanted beam tail or halo from the RCS. The designed collimator aperture is 54  mm mrad. It is required to measure and optimize the optics parameters in the collimator area for taking full advantage of the beam collimation. Especially, it is very important to make the dispersion functions free in the collimator area and optimize the beta function to remove beam tail or halo over predefined transverse emittance. This paper introduces the method of optics measurement and reports the results of the measurement and optimization based on an accelerator model.