Abstract
In this study, the objective is to realize a Gated Integrator (GI) circuit for silicon strip, Si(Li), CdZnTe and CsI detectors etc. With the development of radioactive ion beam physics, heavy-charged particles like carbon ions have been applied to the treatment of deep-seated inoperable tumors in the therapy terminal of the Heavy ion Research Facility in Lanzhou (HIRFL) located at the Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS). A high resolution current measurement circuit was developed to monitor the beam current at 1pA range. The circuit consisted of a low current high sensitivity I/V converter and gated integrator in an energy spectroscopy. A low offset voltage precision amplifier and new guarding and shielding techniques were used in the I/V converter circuit which allowed to measure low current. This paper will show a MOS switch configuration which is used to prevent leakage current and novel technique to compensate a charge injection in the reset switch.
Highlights
IntroductionThe basic concept of gated integrator is to integrate signal as well as background when the image appears, to block or subtract the background when there is no image signal
The basic concept of gated integrator is to integrate signal as well as background when the image appears, to block or subtract the background when there is no image signal. Such procedures are executed numerous times for summation and averaging. Used imaging systems such as Si Charge Coupled Device (CCD), Complementary Metal-Oxide field effect transistor Active Pixel Sensor (CMOS APS), Schottky-Barrier Detector (SBD), InGaAs, InSb and HgCdTe FPAs are all based on the concept of current integration to accumulate signal in the purpose of improving the Signal-to-Noise Ratio (SNR), dynamic range and sensitivity
From November 2006, to 2012, around 106 patients have been irradiated in Lanzhou (HIRFL) at Institute of Modern Physics (IMP), where carbon-ion beams with energies up to 100 MeV/μ can be supplied and a passive beam delivery system has been developed and commissioned (Li and Sihver, 2011)
Summary
The basic concept of gated integrator is to integrate signal as well as background when the image appears, to block or subtract the background when there is no image signal. In Cooling Storage Ring (CSR) IMP Lanzhou, the main works are heavy ion beam accumulation, experiments related to cancer therapy, patients’ treatment, mass measurement and prophase experiments on recombination (Kong et al, 2010; Zhang and Wu, 2011; Zhou et al, 2012). The current signal from the Faraday cup (FC), which was pulsed for 0.5ms a period of 4ms, was converted into a voltage signal through a I/V Converter, the output of which was integrated by the GI in order to measure the charge of the beam (Kong et al, 2010; Redondo et al, 2007; Hori and Hanke, 2008).
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