Internal targets for monitoring the characteristics of particle beams in synchrotrons
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rnal Targets for Monitoring the Characteristics of Particle Beams in Synchrotrons A. S. Artemov and S. V. Afanas’ev Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia Abstract—This overview is devoted to methods and devices with different wire, foil, and gaseous internal targets for online monitoring of the space–time characteristics of the circulating particle beam. Examples of the proposed and developed profilometers based on scanning the diagnosed beam by probes in the form of precision beams of charged or neutral particles are given. Capabilities, advantages, and disadvantages of the methods of virtually nonperturbing diagnostics described above are analyzed. Examples of elementary interactions with large analyzing power of the nuclear polarization of the beam nuclei are given. A number of polarimeters of circulating nuclear beams proposed and developed on their basis for synchrotrons using the appropriate internal targets are considered. PACS numbers: 07.85.Qe, 29.20.Lq, 29.27.Fh DOI: 10.1134/S1063779606040022
1. INTRODUCTION For the efficient operation of synchrotrons, it is important to have quick access to information on the circulating beam. First of all, this is related to its spatial characteristics and polarization. This information is most relevant in tuning operation modes of the synchrotron and during the performance of physical experiments using different internal targets. At the same time, internal targets themselves can serve as diagnostics. In this case, however, they must affect the circulating beam only minimally, and the secondary particles or photons produced on them should carry the necessary information on the beam. It is important that it be possible to monitor this information during acceleration. In the literature, a wide spectrum of methods based on this approach and adapted to particular synchrotrons is described. Therefore, this overview covers only a number of the most original, in the authors' opinion, methods of such diagnostics and some typical devices for their implementation. 2. MONITORING SPACE–TIME CHARACTERISTICS OF THE PARTICLE BEAM USING INTERNAL TARGETS 2.1. Diagnostic Devices with Gas Ionization in the Beam Guide The basic principle of operation of diagnostic devices of this type is registering charged particles produced in the internal gas target (including residual gas) inside the beam guide. The example of the classical version of such diagnostics is the profilometer schematically shown in Fig. 1 and described in [1]. Ion transfer to the detecting microchannel plate (MCP) is performed by electric field. The beam profile is determined from the distribution of
electric signals from the collecting strips behind the MCP. In this work, for the amplifiers to operate identically, the strips were rotated by 90° perpendicular to the beam at regular intervals. It should be noted that due to a possible difference in registration efficiency of the MCP over its area (especially when the plate is “aging”), it is reasonable to rotate the whole system (MCP + cha
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