Bunch shape is one of the most important and interesting characteristics of a beam in ion linear accelerators. Recently detectors of bunch shape with a transverse scanning of low energy secondary electrons found application in several accelerators. The principle of operation of the detectors is based on a coherent transformation of a longitudinal structure of a beam under study into a transverse distribution of a secondary electron beam through rf scanning. There are three modifications of the detectors: Bunch Shape Monitor, Bunch Length (Shape) and Velocity Detector and Three Dimensional Bunch Shape Monitor. The principle of operation of the detectors as well as the peculiarities of the structure and the design of the detectors are described. To demonstrate the possibilities of the detectors the results of measurements with different detectors made at different accelerators are presented.

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In the Japan Proton Accelerator Research Complex linac, an energy upgrade project was started in 2009 using annular-ring coupled structure (ACS) linac cavities. We decided to use bunch shape monitors (BSM) for monitoring longitudinal beam width measurement to achieve longitudinal matching using two bunchers located upstream of the ACS cavities, where the radio frequency jumps from 324 to 972 MHz. Three BSMs were fabricated and installed in the original beam line. The BSMs were commissioned with the beam and their operability was demonstrated. In this study, we introduce the mechanism of the BSMs, its operability, measurement results with the 181 MeV beam, and consistency check with the respective cavity amplitude. Furthermore, we describe the operational vacuum conditions and outline the improvements to the BSMs' vacuum system.

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A profile monitor is described that makes use of a low-intensity and low-energy ion beam to measure the transverse profile of a dense proton beam of small dimensions. Three techniques are considered based on the use of ion beams having a pencil, curtain, or cylindrical shape. The detector is almost non-interceptive for the proton beam and does not introduce disturbances in the machine environment. The theoretical aspects of the techniques used, together with experimental results obtained at the CERN SPS and Linac, are presented.