Thomas C. Marshall
289A Engineering Terrace, Mail Code: 4701
New York, NY 10027
Phone: +1 212 854 3116
Email:
Research specialty
Accelerator concepts, relativistic beams and radiation, free-electron lasers
Education
Ph.D. University of Illinois, 1960
Research
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.
To develop some novel accelerator concepts, we have also established a connection with the Wright Nuclear Structure Laboratory at Yale University. A new device, LACARA, is a laser accelerator that relies on a gyro-resonant interaction between 50MeV electrons moving in a 6T magnetic field and a TW CO2 laser beam, and begins operation in November 2007. Acceleration of bunches of charge to 100MeV should be possible using the LACARA apparatus in this new experiment being assembled at ATF. This project also has the potential to develop fsec-duration charge bunches.
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.
Selected Publications
S.V. Shchelkunov, T.C. Marshall, J.L. Hirshfield, M.A. Babzien, and M.A. LaPointe, "Experimental Observation of Constructive Superposition of Wake Fields Generated by Electron Bunches in a Dielectric-Lined Waveguide", Physical Review Science & Technology, Accelerators and Beams 9, 011301 (2006)
S.V. Shchelkunov, T.C. Marshall, J.L. Hirshfield, and M.A. LaPointe, "Nondestructive Diagnostic for Electron Bunch Length in Accelerators Using the Wakefield Radiation Spectrum", Physical Review Science & Technology, Accelerators and Beams, 8, 062801 (2005)
C. Wang, J.L. Hirshfield, J-M. Fang, and T.C. Marshall, "Strong Wake Fields Generated by a Train of Femtosecond Bunches in a Planar Dielectric Microstructure", Physical Review Special Topics - Accelerators and Beams, 7, 051301 (2004)
Changbiao Wang, T.C. Marshall, V.P. Yakovlev, and J.L. Hirshfield, "Rectangular Dielectric-Lined Two-Beam Accelerator Structure", Particle Accelerator Conference (Proceedings), May 2005, Knoxville Tennessee, paper TPAE-013, p.1333; C. Horak, Editor; IEEE Catalog Number 05CH37623C
T.C. Marshall, "Free Electron Lasers", Macmillan, New York (1985)