Frontiers in Physics (Dec 2024)

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

  • Christopher P. J. Barty,
  • Christopher P. J. Barty,
  • Christopher P. J. Barty,
  • J. Martin Algots,
  • Alexander J. Amador,
  • James C. R. Barty,
  • Shawn M. Betts,
  • Marcelo A. Castañeda,
  • Matthew M. Chu,
  • Michael E. Daley,
  • Ricardo A. De Luna Lopez,
  • Derek A. Diviak,
  • Haytham H. Effarah,
  • Haytham H. Effarah,
  • Haytham H. Effarah,
  • Roberto Feliciano,
  • Adan Garcia,
  • Keith J. Grabiel,
  • Alex S. Griffin,
  • Frederic V. Hartemann,
  • Leslie Heid,
  • Leslie Heid,
  • Yoonwoo Hwang,
  • Gennady Imeshev,
  • Michael Jentschel,
  • Christopher A. Johnson,
  • Kenneth W. Kinosian,
  • Agnese Lagzda,
  • Russell J. Lochrie,
  • Michael W. May,
  • Everardo Molina,
  • Christopher L. Nagel,
  • Henry J. Nagel,
  • Kyle R. Peirce,
  • Zachary R. Peirce,
  • Mauricio E. Quiñonez,
  • Ferenc Raksi,
  • Kelanu Ranganath,
  • Trevor Reutershan,
  • Trevor Reutershan,
  • Trevor Reutershan,
  • Jimmie Salazar,
  • Mitchell E. Schneider,
  • Michael W. L. Seggebruch,
  • Michael W. L. Seggebruch,
  • Joy Y. Yang,
  • Nathan H. Yeung,
  • Collette B. Zapata,
  • Luis E. Zapata,
  • Eric J. Zepeda,
  • Jingyuan Zhang

DOI
https://doi.org/10.3389/fphy.2024.1472759
Journal volume & issue
Vol. 12

Abstract

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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.

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