The results from upgrade of an ionization beam profile monitor (IBPM) are presented. The IBPM consists of a conventional capacitor that extracts the ionization products of the residual gas and analyzing capacitors. The main objective of this upgrade was to create a device with uniform spatial resolution. For this purpose, an additional difference of potentials, the ramping of which allows the beam cross section to be scanned, is applied between the capacitors of the monitor, while the electric fields in the capacitors themselves remain constant. Two IBPMs have been developed as a result of the facility's upgrade: an IBPM for on-line monitoring of the vertical and horizontal beam current distributions in the beam line in an area of 8 × 8 cm 2 with a uniform 1-mm resolution, and an IBMP for detailed beam profile monitoring with a uniform resolution of 1 × 1 mm 2 over the scanning region. It was established experimentally that the proposed scanning technique provides good results in beam profile measurements when the ion component of the ionized residual gas is extracted; for the electron component, the result is much worse.
The design and the performance of the primary beam diagnostic system operating on a non-intercepting measurement method are described. It was assembled for operation under harsh environmental conditions. The main part of the beam detection system is the Ionization Beam Profile Monitor (IBPM) operating on the ionization of the residual gas principle. The primary beam diagnostic system provides data sufficient to plot spatial distributions of the beam current in the monitored area operating in on-line regime. It was used to monitor the profiles of 7 Li, 11 B, 32 S beams in the energy range of 30 50 AMeV and 20 Ne, 40 Ar, 86 Kr, 132 Xe beams at 4 5 AMeV. All measurements were performed under the conditions of high gamma and neutron flux. The diagnostic box was located in the vicinity of the accelerator, where the neutron flux was over 10 6 neutrons cm 2 s. The beam current was in the range of a few nA up to 15 A. The device operates in vacuum on the level of 10 6 10 3 mbar without loss of resolution power at the beam current as low as a few nA. Long operation time and emergency situations do not lead to decrease of its operability.Index Terms-Hard radiation conditions, heavy ion beams, ionization beam profile monitor, on-line beam monitoring, the U400M cyclotron of FLNR JINR.
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