A monitor for heavy ion flux density control based on detection of recoil protons during irradiation of polymer films

Abstract

An monitor for control of accelerated particle flux density used in irradiation of polymer films with heavy ions with a low track density (103−5 × 107 cm−2) is based on detection of recoil protons. It has been designed to control irradiation of a film with a width of up to 650 mm and is composed of five PIN diodes with a hydrogenous target placed in front of each diode. The sensitivity of the monitor with a polyethylene target to the density of a xenon ion beam is described by a linear function; its value is (4.0±0.5) × 10−3 pulses/(ion/cm2). The instrument is capable of monitoring ion flux densities of <106 cm−2, for which all other methods are ineffective. It can be used to determine the track density in a finished product, bypassing the stage of a check with an electron microscope. The signals from the monitor can also be used to introduce a feedback in a system of automatic beam tuning in order to improve the film irradiation quality. The radiation hardness of silicon detectors is ≈ 1012 protons/cm2. At an average detector load of ≈ 104 protons/cm2, the average service life of the monitor is 108 s of continuous operation.