The Beam-Handling Magnet System for the J-PARC Neutrino Beam Line

The facility of the long baseline neutrino oscillation experiment using the J-PARC's 50 GeV-0.75 MW proton beam is now under way. The primary proton beam line consists of three sections, i.e. the first preparation (PP) section with normal conducting magnets, the second arc (ARC) section with superconducting magnets and the third final focus (FF) section with normal conducting magnets. In the PP section, we have to clean the primary proton beam extracted from the 50 GeV-PS and transport halo-less pure beam only to the ARC section. In the FF section the magnets have to be placed very close to the pion production target and horns. Therefore the normal conducting magnets have to work in the very high radioactive environment. The R&D works on the radiation resistant magnets for handling a high-intensity proton beam have already been continued at KEK as reported in . Another important point regarding high-intensity beam handling is to realize easy maintenance of the beam line. Any magnet experiencing trouble can be easily removed from beam line and repaired remotely. For this purpose, we developed new tools for the magnet maintenance. These are automatic sling apparatus, quick alignment and installation guide, and the quick disconnect devices of cooling water and electric power. In this paper, we will report the beam line maintenance scheme developed for the neutrino beam line, as well as the design of normal conducting magnet sections

1. Introduction

THE NEUTRINO beam facility started construction for the long baseline oscillation experiments combining with Super-KAMIOKANDE cosmic neutrino observatory [2]. It will use the J-PARC [3] 50 GeV 0.75 MW proton beam to create a high intensity neutrino beam. The primary proton beam line transporting the proton beam to a production target consists of the first preparation (PP) section, the arc (ARC), and final focus (FF) section (Fig. 1). The PP section consists of 12 normal conducting magnets and collimators. The ARC section is composed of 28 combined function superconducting magnets and bends the proton beam about 80 degrees toward Super Kamiokande. The FF section, using 10 normal conducting magnets, shapes the beam from ARC section to be suitable for the production target. Construction of the J-PARC neutrino beam line started in 2004 and the first beam is expected in 2009. Fig. 1.

Schematic illustration of the j-parc neutrino beam line.