Development of high-sensitivity beam profile monitor using multiscreen

In the development of a high-sensitivity two-dimensional profile monitor used in the incidence transport line toward the main ring of Japan Proton Accelerator Research Complex (J-PARC), the authors demonstrated that it is possible to measure from the core to the tail of beam with the sensitivity of six digits or higher. For measurement, optical transition radiation (OTR) from titanium and aluminum foils and fluorescence from chromium-doped alumina with were used. The three types of beams were corrected with measured light intensity values to obtain a profile of OTR light equivalent to fluorescence, and correction data were plotted to obtain a beam profile using a multiscreen. As a result, by combining the profiles of OTR and of fluorescence, it was possible to measure the spatial distribution of the beam in the lateral direction with a light intensity ratio of about six digits. A large amount of light can be obtained using a chromium-doped alumina screen. In the future, by extending the image intensifier gating time used in this measurement longer than 10 μs, it is considered possible to measure with higher sensitivity. By setting the alumina screen in the halo area just in front of the solid screen of OTR as viewed from the beam, it is considered possible to measure from the beam core to the halo in one shot by developing a target system capable of measuring OTR light and fluorescence simultaneously. (A.O.)