Implementation and validation of a beam-current transformer on a medical pulsed electron beam LINAC for FLASH-RT beam monitoring

Abstract
Purpose: To implement and validate a beam current transformer as a passive
monitoring device on a pulsed electron beam medical linear accelerator (LINAC)
for ultra-high dose rate (UHDR) irradiations in the operational range of at least
3 Gy to improve dosimetric procedures currently in use for FLASH radiotherapy
(FLASH-RT) studies.
Methods: Two beam current transformers (BCTs) were placed at the exit of
a medical LINAC capable of UHDR irradiations. The BCTs were validated as
monitoring devices by verifying beam parameters consistency between nominal
values and measured values, determining the relationship between the charge
measured and the absorbed dose, and checking the short- and long-term stability
of the charge-absorbed dose ratio.
Results: The beam parameters measured by the BCTs coincide with the nominal
values. The charge-dose relationship was found to be linear and independent
of pulse width and frequency. Short- and long-term stabilities were measured
to be within acceptable limits.
Conclusions: The BCTs were implemented and validated on a pulsed electron
beam medical LINAC, thus improving current dosimetric procedures and allowing
for a more complete analysis of beam characteristics. BCTs were shown
to be a valid method for beam monitoring for UHDR (and therefore FLASH)
experiments.