Space Charge Effects in the S$\pi$RIT Time Projection Chamber

TL;DR

This paper investigates how space charge from ionized gas affects the electric field and measurement accuracy in the S$$RIT TPC during heavy ion collision experiments, proposing correction algorithms to improve data precision.

Contribution

It introduces a new observable for fixed target experiments and presents an algorithm to correct space charge effects in TPC measurements.

Findings

Quantifies the impact of space charge on electric field distortion.

Develops an algorithm for correcting space charge effects.

Improves momentum measurement accuracy in TPCs.

Abstract

Time projection chambers (TPCs) are widely used in nuclear and particle physics. They are particularly useful when measuring reaction products from heavy ion collisions. Most nuclear experiments at low energy are performed in a fixed target configuration, in which the unreacted beam will pass through the detection volume. As the beam intensity increases, the buildup of positive ions created from the ionization of the detector gas by the beam creates the main source of space charge, distorting the nominal electric field of the TPC. This has a profound effect on the accuracy of the measured momenta of the emitted particles. In this paper we will discuss the magnitude of the effects and construct an observable more appropriate for fixed target experiments to study the effects. We also will present an algorithm for correcting the space charge and some of the implications it has on the momentum determination.