O'Shea, Patrick G.
Professor
Distinguished Scholar-Teacher
FIEEE, FIAE, FRSA, FAPS, FAAAS
Institute for Research in Electronics & Applied Physics
New Publications:
Electric Ivy (July 2024)
Superpower E-Beam Sources and Performance Estimates for Compact THz FELs (July 2024)
Harmonic generation in a terawatt x-ray free-electron laser (May 2024)
Abstract: Terawatt x-ray free-electron lasers (XFELs) represent the frontier in further development of x-ray sources and require high current densities with strong transverse focusing. In this paper, we investigate the implications/potentialities of TWXFELs on generating harmonics at still shorter wavelengths and higher photon energies. The simulations indicate that significant power levels are possible at high harmonics of the XFEL resonance and that these XFELs can be an important coherent source of hard X-rays through the gamma-ray spectrum. For this purpose, we use the MINERVA simulation code, which self-consistently includes harmonic generation. Both helical and planar undulators are discussed in which the fundamental is at 1.5Åand study the associated harmonic generation. While tapered undulators are needed to reachTWpowers at the fundamental, the taper does not enhance the harmonics because the taper must start before saturation of the fundamental, while the harmonics saturate before this point is reached. Nevertheless, the harmonics reach substantial powers. Simulations indicate that, for the parameters under consideration, peak powers of the order of 180MWare possible at the fifth harmonic with a photon energy of about 41 keV and still high harmonics may also be generated at substantial powers. Such high harmonic powers are certain to enable a host of enhanced applications.
We're looking for a student to work on creating light where darkness exists in the electromagnetic spectrum, specifically with ultra-high-power Terawatt X-ray Free-electron Lasers.
Since the first x-ray free-electron laser (XFEL) was demonstrated at the Stanford Linear Accelerator Center (SLAC) in 2009, XFEL facilities have expanded worldwide for many applications. Due to the lack of seed lasers at these wavelengths, most of these facilities rely on self-amplified spontaneous emission (SASE) to produce x-ray pulses with peak powers of the order of 10s of GW. However, XFELs have the potential to achieve Terawatt peak powers, and this will require substantial improvements in the optical extraction efficiency (defined as the ratio of the optical power out to the electron beam power in). Currently, XFELs have rather low optical extraction efficiencies, typically less than 0.1%. We believe that significant increases in optical extraction efficiency can be achieved using novel technology. We expect that such dramatic increases in the output power of XFELs will lead to a host of new applications.
Recent THZ Publications:
Abstract: Interest is increasing in high-power terahertz (THz) radiation sources. The terminology is fluid, but researchers typically refer to frequencies ranging from about 300 GHz to 10 THz as THz radiation. This article describes design considerations for a compact, high-average power free-electron laser. At present, THz radiation is generated by a variety of mechanisms, including laser-based sources and electron-beam-based sources. We provide a short description of current THz source technology to give background against which to compare the present concept; however, this should not be considered a comprehensive discussion of such technologies.
Superpower E-Beam Sources and Performance Estimates for Compact THz FELs (October 2024)
Abstract: High peak and average power free-electron lasers (FELs) in the terahertz (THz) region require small-diameter, low-emittance, and high-voltage electron beams. This article presents two 1.5–2-MV, 100–200-A, thermionic cathode electron source approaches for compact megawatt range peak power, multikilowatt average power, high repetition rate, THz FELs. The preferred beam generation system includes grading electrodes and is quite compact compared to standard diode gun approaches. Both provide highly compressed beams at the waist having low values of normalized rms emittance. In particular, the new injector approach with grading electrodes, operating at a body voltage of 1.5–2 MV and 100 A, has a normalized rms emittance of roughly 10 μ m at the beam waist. Power supply switching considerations are considered in this article and for very high-voltage multistage depressed collectors for device efficiency enhancement. Based on these designs, we provide performance estimates for FELs operating in the THz spectral region.
A presentation by graduate student Liam Pocher won a best student paper award at NAPAC22
See details, and watch Liam's presentation under the Publications tab above
Bright Beams at Work News:
IS THE FUTURE OF MOORE’S LAW IN A PARTICLE ACCELERATOR? Chip Fab using EUV Free-Electron Lasers
High Energy Physics
US particle physicists envision the future of the field.
Cancer Treatment:
Ultra-Fast Accelerator Based Therapies Could Revolutionise Cancer Treatment
How radiotherapy became a lifesaver – from X-rays to the proton beam
Will Proton Therapy Market Reach $1.6 Billion by 2031?
New Discoveries:
Compact, cheaper, laser-powered particle accelerators get real
CERN's Large Hadron Collider poised to unlock more secrets of the universe
5 Myths About Patricle Acelerators
Unresolved questions: Does warm water freeze faster than cool water?
A flock of birds exhibiting swarming behavior ( photo by D. Dibenski)
Space Charge Dreams (photo by Chip Simons)
BACKGROUND
Professor O'Shea is Principal Investigator in the Bright Beams Collective Research Group
He was born in Cork, Ireland, and holds a BSc degree in Experimental Physics from the National University of Ireland, University College Cork, and an M.S. and Ph.D. in Physics from the University of Maryland.
Having made significant contributions to education and research, he is a Fellow of the American Association for the Advancement of Science, American Physical Society, Institute of Electrical and Electronic Engineers, Irish Academy of Engineering, Royal Society for the Arts, and won the University of Maryland's Distinguished Scholar-Teacher Award.
Professor O’Shea’s technical expertise lies in the field of applied electromagnetics, nonlinear dynamics, and charged particle beam technology, and applications.
Currently: Chair of the following UMD committees: Research Conflict of Interest, Institutional Conflict of interest, and Organisational Conflict of Interest
Professor O'Shea has previously served as:
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President of University College Cork, Ireland,
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Vice President for Research at the University of Maryland,
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Chair of the Department of Electrical & Computer Engineering at the University of Maryland’s A. James Clark School of Engineering.
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Director of the Institute for Research in Electronics and Applied Physics (IREAP) at the University of Maryland.
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Faculty member at Duke University
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Project Leader at the University of California Los Alamos National Laboratory.
Professional Societies and Honors
- American Association for the Advancement of Science, Fellow
- Irish Academy of Engineering, Fellow
- American Physical Society, Fellow
- Institute for Electrical and Electronic Engineering, Fellow
- Royal Society for the Encouragement of Arts, Manufactures, and Commerce (RSA), Fellow
- Distinguished Scholar-Teacher, University of Maryland
- Phi Kappa Phi Honor Society
- President Emeritus, University College Cork
ENEE 686 Charged Particle Dynamics: Learn how to make a better brighter. By “beam” we mean a swarm of charged particles (electrons or ions) that is collectively heading off to do something useful. The collective dynamics of these swarms are really interesting. We are particularly interested in beams where the self-forces resulting from space-charge are very strong, at the extreme frontier of intensity. They exhibit nonlinear phenomena such as solitary waves (solitons)They exhibit nonlinear phenomena such as solitary waves (solitons) Understanding beam swarms, and how to control them is important for many applications, such as creating light where there is darkness in the electromagnetic spectrum, cancer treatment, radiographic imaging, tomography, high-energy-density physics, inertial fusion energy; and galactic dynamics.
A flock of birds exhibiting swarming behavior (D. Dibenski)