Design, Construction, and Test of Compact, Distributed-Charge, X-Band Accelerator Systems that Enable Image-Guided, VHEE FLASH Radiotherapy

• Main Authors: Barty, Christopher P. J, Algots, J. Martin, Amador, Alexander J, Barty, James C. R, Betts, Shawn M, Casteñada, Marcelo A, Chu, Matthew M, Daley, Michael E, Lopez, Ricardo A. De Luna, Diviak, Derek A, Effarah, Haytham H, Feliciano, Roberto, Garcia, Adan, Grabiel, Keith J, Griffin, Alex S, Hartemann, Frederic V, Heid, Leslie, Hwang, Yoonwoo, Imeshev, Gennady, Jentschel, Michael, Johnson, Christopher A, Kinosian, Kenneth W, Lagzda, Agnese, Lochrie, Russell J, May, Michael W, Molina, Everardo, Nagel, Christopher L, Nagel, Henry J, Peirce, Kyle R, Peirce, Zachary R, Quiñonez, Mauricio E, Raksi, Ferenc, Ranganath, Kelanu, Reutershan, Trevor, Salazar, Jimmie, Schneider, Mitchell E, Seggebruch, Michael W. L, Yang, Joy Y, Yeung, Nathan H, Zapata, Collette B, Zapata, Luis E, Zepeda, Eric J, Zhang, Jingyuan
• Format: Journal Article
• Language: English
• Published: 07-08-2024
• Subjects: Physics - Accelerator Physics; Physics - Medical Physics; Physics - Optics
• DOI: 10.48550/arxiv.2408.04082

The design and optimization of laser-Compton x-ray systems based on compact
distributed charge accelerator structures can enable micron-scale imaging of
disease and the concomitant production of beams of Very High Energy Electrons
(VHEEs) capable of producing FLASH-relevant dose rates. The physics of
laser-Compton x-ray scattering ensures that the scattered x-rays follow exactly
the trajectory of the incident electrons, thus providing a route to
image-guided, VHEE FLASH radiotherapy. The keys to a compact architecture
capable of producing both laser-Compton x-rays and VHEEs are the use of X-band
RF accelerator structures which have been demonstrated to operate with over 100
MeV/m acceleration gradients. The operation of these structures in a
distributed charge mode in which each radiofrequency (RF) cycle of the drive RF
pulse is filled with a low-charge, high-brightness electron bunch is enabled by
the illumination of a high-brightness photogun with a train of UV laser pulses
synchronized to the frequency of the underlying accelerator system. The UV
pulse trains are created by a patented pulse synthesis approach which utilizes
the RF clock of the accelerator to phase and amplitude modulate a narrow band
continuous wave (CW) seed laser. In this way it is possible to produce up to 10
{\mu}A of average beam current from the accelerator. Such high current from a
compact accelerator enables production of sufficient x-rays via laser-Compton
scattering for clinical imaging and does so from a machine of "clinical"
footprint. At the same time, the production of 1000 or greater individual
micro-bunches per RF pulse enables > 10 nC of charge to be produced in a
macrobunch of < 100 ns. The design, construction, and test of the 100-MeV class
prototype system in Irvine, CA is also presented.