Related Experiment Video
Updated: Jun 14, 2026
Automated Delivery of Microfabricated Targets for Intense Laser Irradiation Experiments
Published on: January 28, 2021
Development and validation of a novel pulse optimization and beam control system for conventional and ultra high
Luke Connell1,2, Nolan Esplen1, Rebecca Lim1,2
1Division of Radiation Oncology, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
Background:
FLASH radiotherapy requires precise control and minimal variation of dose per pulse (DPP). However, clinical linear accelerators and their beam control systems are designed to ensure accuracy of the temporally integrated dose and do not control for transient variations in DPP during radiation delivery.
Purpose:
We introduce a robust external beam control system (EBCS) with radiofrequency optimization and beam monitoring that addresses this need. This system was designed to precisely control the output of FLASH-capable electron linear accelerators within a clinical range of energies (6-20 MeV) and to monitor the output by using a beam current transformer.
Methods:
An EBCS, using either an internal transmission ion chamber or a multistage beam current transformer, was implemented to support delivery of conventional DPPs and ultrahigh DPPs (UH-DPPs) on a modified clinical linear accelerator. The EBCS was interfaced with the accelerator's gating system, and beam output and stability were maximized by optimizing the accelerating radiofrequency power efficiency through voltage inputs (VEXT) to the automatic frequency control interface while the beam was held. The EBCS performance was tested by characterizing the beam-off latency; beam output stability within and between pulsed deliveries; sensitivity to deviations from optimization solutions; and beam current transformer linearity from conventional DPPs to UH-DPPs.
Results:
The measured beam-off latency of the system was 56.7 µs (± 4.9 µs). The radiofrequency optimization was shown to reduce the DPP variability within the first five pulses from 26.7% to less than 0.5% for both conventional DPPs and UH-DPPs. Total output was reduced by up to 20% when VEXT voltage inputs varied from the optimal solution by more than ± 10%.
Conclusion:
We developed an EBCS capable of delivering reproducible doses and implemented it on a modified clinical linear accelerator. Through real time readout of the beam current transformer signal and automatic radiofrequency optimization, the uncertainty in DPP within and between each delivery was reduced to < 0.5%, offering unprecedented precision and accuracy.
