Thomas C. Marshall
Professor Emeritus of Applied Physics and Special Research Scienstist
Accelerator concepts, relativistic beams and radiation, free-electron lasers
Ph.D. University of Illinois, 1960
In the past, our group has pioneered the development of free electron lasers (FEL), which have been shown to generate very large amounts of power, tunable in bands from the microwave to the visible spectrum and beyond. FEL physics has a close relationship with laser and accelerator physics, and it is the latter which is receiving most of my attention now. In the FEL, electrons lose energy and the light wave gains energy, via stimulated emission. In many advanced accelerators, the process is reversed, and a laser beam loses intensity while the electrons gain energy (stimulated absorption). So it should come as no surprise that we have centered most of our research activity in advanced acceleration concepts as the field of FEL matured. In the past we have investigated FEL photonics, which is now relevant to the development of an X-Ray FEL which starts from photon and particle noise, the production of TW-level ultra-short pulses of radiation from the FEL, and the "inverse FEL" (IFEL) which is a promising advanced concept laser accelerator of electrons. Some of the IFEL work was done in collaboration with the Accelerator Test Facility (ATF) at Brookhaven National Laboratory, where a 50MeV rf linac is available for outside investigators.
It is an objective of high energy physics to develop a linear accelerator which can deliver bunches of charge at energy ~ 1TeV. Current technology can provide this energy, but size and cost of the facility could be prohibitive. Thus there is motivation to explore different methods of accelerating particles. An IFEL is one example, and is now being refined by other investigators.
Another device being studied is the dielectric wake field accelerator, which has the potential to accelerate charges to very high energy using a sequence of "stages". This wake field accelerator requires no laser or microwaves to energize a bunch of electrons, using instead a train of “drive” bunches provided by an efficient, lower energy, conventional accelerator. Bunches set up by these fields will in turn accelerate a correctly timed, co-moving bunch of "test" particles. The rectangular configuration of these wakefield structures promises to accelerate a comparatively large amount of charge in a way which permits stable motion of the charges. We are currently working on a “two-channel” device, which separates the line of drive bunches from the accelerated bunches.
Sotnikov, Gennadij & Marshall, T & V. Shchelkunov, Sergey & L. Hirshfield, Jay. (2018). "The Dielectric Resonator Wakefield Accelerator." 1-5. 10.1109/AAC.2018.8659430.
G.V. Sotnikov, T.C. Marshall, S.V. Shchelkunov, and J.L. Hirshfield, “The Dielectric Wakefield Resonator Accelerator”, August 16, 2017 in arXiv:1708.04599v1 [physics.acc-ph]
G.V. Sotnikov, R.R. Kniaziev, O.V. Manuilenko, P.I. Markov, T.C. Marshall, I.N. Onishchenko, “Analytical and Numerical Studies of Underdense and Overdense Regimes in Plasma Dielectric Wakefield Accelerators”, Nuclear Instruments and Methods in Physics Research A 740, p.124 (2014); (presented at EAAC2013, La Biodala, Isola d’Elba Italy, June 2013)
S.V. Kuzikov, Y. Jiang, T.C. Marshall, G.V. Sotnikov and J.L. Hirshfield, "Configurations for Short Period RF Undulators", Phys. Rev. ST Accel. And Beams, 16, 070701 (2013)
S.V. Shchelkunov, T. C. Marshall, G.V. Sotnikov et al., "Comparison of Experimental Tests and Theory for a Rectangular Two-Channel Dielectric Wakefield Accelerator Structure", Phys. Rev. ST ?Accel. and Beams, 15, 031301 (2012)
Sotnikov, G.V. and Marshall, T.C., "An improved ramped bunch train to increase the transformer ratio of a two-channel multimode dielectric wakefield accelerator", Phys. Rev. ST-Accel. and Beams 14, 031302 (2011)
G.V. Sotnikov, T.C. Marshall, and J.L. Hirshfield, "Coaxial Two-Channel High Gradient Dielectric Wakefield Accelerator", Phys. Rev. ST Accel. and Beams, 12, 061302, (2009)
T.C. Marshall, "Free Electron Lasers", Macmillan, New York (1985)