Profile Measurement by the Ionization Profile Monitor with 0.2T Magnet System in J-PARC MR

Abstract

A nondestructive Ionization Profile Monitor (IPM) is widely used to measure transversal profile. At J-PARC Main Ring (MR), three IPM systems have been used not only to measure emittances but also to correct injection miss matchings. To measure injection 3GeV beam profiles, the high external E field of +50kV/130mm at the maximum is used to guide ionized positive ions to a position sensitive detector; transversal kick force originating from space charge E field of circulating beam is a main error source which deteriorates profile. The strong B field is also used to compensate the kick force. To measure 30GeV bunched beam at the flat top on the fast extraction mode in good resolution, the strong B field of about 0.2T is needed. One set of magnet system, which consists of a C-type and two H-type magnets, were developed and installed in one IPM system. The IPM chamber was inserted between the 2 poles of the C-type magnet. To make the line integral of B field along the beam axis zero, the H-type magnets have the opposite field polarity to that of the C-type magnet and were installed on both sides of the C-type magnet. Details of the magnet system and its first trials will be presented.