Beam tests of a beam position monitor for ISOL operation

A beam position monitor (BPM) is built and tested to monitor the stability of high intensity proton beams accelerated by a 70 MeV cyclotron for ISOL operation in the aspects of beam position and current. The prototype BPM has four pick-up electrodes with a length of 19 cm and uses Libera Spark™ to process signals. It was firstly tested using a moving wire method to calibrate beam positions and further tested when installed in the beam line together with a beam profile monitor during beam commissioning of the cyclotron. The prototype system produced well-defined signals for two transverse directions with a resolution of 0.1 mm and for beam intensity up to 600 μA. A beam-stop signal can be issued by the readout program for the Spark when beam instabilities evaluated by the program reach certain limits set for each operation. The non-destructive BPM monitoring of high-current beams will be integrated into the safety PLC after a series of ISOL operation are carried out.