High-rate axial-field ionization chamber for particle identification of radioactive beams

TL;DR

This paper introduces a high-rate axial-field ionization chamber optimized for radioactive beam identification, featuring fast response and good energy resolution at high particle rates, suitable for low-energy radioactive beams.

Contribution

The paper presents a novel axial-field ionization chamber with integrated fast charge amplifier, capable of high-rate operation and precise ion identification in radioactive beam experiments.

Findings

Energy resolution of ~8% at 3.5 MeV with alpha source

Maintains ~14% resolution at 2.5-4.0 MeV/A with radioactive beams

Operates effectively at rates up to 3 x 10^5 ions/sec

Abstract

The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. Optimized for use with low-energy radioactive beams (< 5 MeV/A) the detector presents only three 0.5 $\mu$m/cm$^2$ foils to the beam in addition to the detector gas. A fast charge sensitive amplifier (CSA) integrated into the detector design is also described. Coupling this fast CSA to the axial field ionization chamber produces an output pulse with a risetime of 60-70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate. Tests with an $\alpha$ source establish the detector energy resolution as $\sim$8 $\%$ for an energy deposit of $\sim$3.5 MeV. The energy resolution with beams of 2.5 and 4.0 MeV/A $^{39}$K ions and the dependence of the energy resolution on beam intensity is measured. At an instantaneous rate of 3 x 10$^5$ ions/s the energy resolution has degraded to 14% with a pileup of 12%. The good energy resolution of this detector at rates up to 3 x 10$^5$ ions/s makes it an effective tool in the characterization of low-energy radioactive beams.