The impacts of the ballistic deficit and electron attachment on the pulse shapes of the Frisch-grid ionization chamber

Abstract The pulse shapes of the Frisch-grid ionization chamber (GIC) will be affected by the ballistic deficit and electron attachment. Theoretical derivations and experiments are carried out to clarify the impacts of the two effects on the pulse shapes of the GIC. It is found that the anode amplitude increases with the decrease of the cosine of the emitting angle under the influence of the ballistic deficit, while the anode amplitude decreases with the decrease of the cosine of the emitting angle under the influence of the electron attachment. These opposite variation trends caused by the ballistic deficit and electron attachment could cancel each other out when the attachment probability per unit time equals the inverse of the time constant of the GIC circuit, which improves the energy resolution of the GIC, although the anode amplitude is reduced. The difference of the two variation trends provides a method to judge whether the working gas of the GIC contains electronegative gases.