Vacuum system design for the 3 GeV-proton synchrotron of JAERI-KEK joint project

Abstract

A rapid-cycling magnetic field is necessary to operate a synchrotron with a high repetition rate for the 3 GeV proton synchrotron of JAERI-KEK joint project. Since an eddy-current effect in a metal duct would produce an unacceptable perturbation of the magnetic field and unnecessarily large ohmic losses, an alumina ceramic is a candidate material for vacuum ducts in the dipole and quadrupole magnets. The required beam apertures, being a circular cross section, are 187 and 247 mm in diameter for the vacuum ducts to be installed in the dipole and quadrupole magnets, respectively. The duct lengths for each magnet are 3.5 and 1 m. Since such a long duct is difficult to make with accuracy in the radial dimension, when sintered at once, it can only be manufactured by jointing duct segments of about 0.5 m long. The mechanical strength and deterioration under a high level of radiation were examined for various kinds of alumina ceramic and for the joint. Almost all of the ceramics to be tested have a sufficiently high flexural strength of 300 MPa, or more, before irradiating with a 2.5 GeV-electron beam, and they did not show any significant deterioration in the flexural strength as far as an absorption dose is up to 1000 MGy.

Measurement of radioactivity and evaluation of activated nuclides due to secondary particles produced in stripper foil in J-PARC RCS

“…Pure copper plates measuring 20 mm in length, 5 mm in width, and 1 mm in thickness were prepared as secondary particle-irradiating targets. We performed measurements at four points, namely, upstream titanium (Ti) sleeve that connected the titanium flange and the ceramic beam duct for the shift bump magnet 1 (SB1u) [15], downstream sleeve for the shift bump magnet 2 (SB2d), upstream sleeve for the shift bump magnet 3 (SB3u), and downstream sleeve for the shift bump magnet 4 (SB4d). The angles between the beam direction and the direction of the four measured points seen from the stripper foil were approximately 175°, 135°, 50°, and 5°, respectively.…”

Alumina Ceramics Vacuum Duct for the 3GeV-RCS of the J-PARC

“…Alumina ceramics vacuum ducts have been under development at JAERI [1], [2], [3]. There are two types of alumina ceramics vacuum ducts needed, one being 1.5m-long duct with a circular cross section of 378 mm inner diamater for use in the quadrupole magnet, the other being 3.5m-long and bending 15 degrees, with a racetrack cross section for use in the dipole magnet.…”