Accurate Low Current Measurement Electronics With Self-Calibration Function for Ionization Chamber of Slow Extraction in HIAF

Abstract

The new wide-range readout electronics with a self-calibration function are designed for ionization chambers (ICs) in the slow extraction of high-intensity heavy-ion accelerator facility (HIAF), booster ring (BRing). These electronics consist of a programmable trans-impedance amplifier (TIA), a self-calibration circuit, an 18-bit analog-to-digital converter (ADC), and a ZYNQ-7015 field-programmable gate array (FPGA). It is capable of monitoring weak current signals of 40 pA–4 mA with a sampling rate of 5 MHz. The ZYNQ-7015 FPGA manages the operation mode of the analog front-end (AFE) and the gain of the TIA. It also performs digital signal processing algorithms and data communication with the host computer. The self-calibration circuit uses a combination of a Schmitt trigger and voltage-to-current (V–I) converters to generate two square wave current signals with different peaks ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 \mu \text{A}$ </tex-math></inline-formula> and 2 mA). During offline tests, the effective number of bits (ENOB) is 12.98 bits, and the nonlinearity is less than 0.075% for a full scale. Finally, the readout electronics are deployed for ICs’ slow extraction measurements at the extraction line of the cooling storage ring of the heavy-ion research facility in Lanzhou (HIRFL). With the help of a commercial dc-transformer in the cooling storage ring project of heavy ion research facility in Lanzhou (HIRFL-CSR), these electronics not only execute an accurate current measurement, but also can monitor the extraction efficiency reliably. In a word, these electronics play an important role in the fields of extremely weak and high dynamic current signal measurements.