AUTHOR=Barty Christopher P. J. , Algots J. Martin , Amador Alexander J. , Barty James C. R. , Betts Shawn M. , Castañeda Marcelo A. , Chu Matthew M. , Daley Michael E. , De Luna Lopez Ricardo A. , 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 

TITLE=Design, construction, and test of compact, distributed-charge, X-band accelerator systems that enable image-guided, VHEE FLASH radiotherapy

JOURNAL=Frontiers in Physics

VOLUME=Volume 12 - 2024

YEAR=2024

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2024.1472759

DOI=10.3389/fphy.2024.1472759

ISSN=2296-424X

ABSTRACT=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 (∼ 10 Gy in less than 100 ns). The physics of laser-Compton x-ray scattering ensures that the x-rays produced by this process follow exactly the trajectory of the electrons from which the x-rays were produced, thus providing a route to not only compact VHEE radiotherapy but also image-guided, VHEE FLASH radiotherapy. This manuscript will review the compact accelerator architecture considerations that simultaneously optimize the production of laser-Compton x-rays from the collision of energetic laser pulses with high energy electrons and the production of high-bunch-charge VHEEs. The primary keys to this optimization are 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 µA 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 1,000 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.