Patrick O'Shea

Professor & Chair of Electrical & Computer Engineering

Distinguished Scholar Teacher

A. James Clark School of Engineering

 

Affiliate Appointments:

Institute for Research in Electronics & Applied Physics

Department of Physics

Maryland Nano Center  

Maryland Energy Research Center

 

 

Land mail: 

Dept. of Electrical & Computer Engineering

2415 A. V. Williams Hall

University of Maryland

College Park, MD 20742

 

Phone: (301) 405-3683
Email: search here for O'Shea

 

Patrick G. O’Shea is Professor and Chair of the Department of Electrical & Computer Engineering at the University of Maryland’s A. James Clark School of Engineering. He is also Executive Director of the Center for Applied Electromagnetics. He holds affiliate appointments in Institute for Research in Electronics & Applied Physics, Department of Physics, Maryland Nano Center, and Maryland Energy Research Center.

Prior to becoming Chair of ECE, he was Director of the Institute for Research in Electronics and Applied Physics (IREAP) at the University of Maryland.  He played a major role in establishing the Maryland  Nano Center, and the new Maryland Center for Applied Electromagnetics.  Previously he was a project leader at the University of California Los Alamos National Laboratory, and a faculty member at Duke University working on the Medical Free-Electron Laser Program. He was born in Cork, Ireland. He is an alumnus of Coláiste Chríost Rí secondary school in Cork. He holds a BS degree from the National University of Ireland, University College Cork, and MS and Ph.D. degrees from the University of Maryland all in physics.

He is a Fellow of the American Physical Society, a Fellow of the Institute of Electrical and Electronic Engineers, and a Fellow of the American Association for the Advancement of Science, and a member of the Washington Academy of Sciences, and a University of Maryland Distinguished Scholar Teacher.

Professor O’Shea’s technical expertise lies in the field of applied electromagnetics, nonlinear dynamics and particle accelerator technology, and applications. 

O'Shea Group Projects 

Photo: Tim Koeth

University of Maryland Electron Ring Project - UMER   Continuing A Space Charge Odyssey

The nonlinear dynamics of electron swarms is important for several applications, including high energy physics accelerators where we are exploring space charge dominated beams for advanced accelerators;  particle beam driven high energy density physics, including, inertial fusion energy; applications to galactic dynamics; and free-electron light sources. 

The group began studying space charge dominated beams (AKA intense beams) in the 1980s under the direction of Professor Martin Reiser, who is now Professor Emeritus. UMER is the culmination of Prof. Reiser's dream of a dedicated facility for the study of intense beam physics and engineering.  

See The Perfect Swarm here

Photo: Chip Simons

Free-Electron lasers: Creating coherent light where there is darkness since 1990.  

Regions of the spectrum were there is a need for brighter light include the x-ray (coherent x-ray probes for Nanoscale Science and Technology); UV and infrared radiation for industrial processing, and far infrared THz sources for biological probes. Prof. O'Shea began exploring the development of free-electron light sources and enabling technologies in 1990 at Los Alamos where he was project leader of the APEX Free-Electron Laser. This was the first photoinjector linear accelerator driven ultra-violet FEL. Photoinjectors use laser switched photoemitters to generate the bright beams required for certain kinds of FELs.  Recently the research group has been working on several aspects of the generation of bright electron beams including: novel photocathodes, the dynamics of beams with space charge, and beam diagnostic probes, and FEL theory and simulation.

Review article: Free-Electron Lasers, Science 8 June 2001, Vol. 292, page 1853 

Review Article: Electron Sources for Accelerators, Physics Today, February, 2008, page 44

National Academy Report: Scientific Assessment of High-Power Free-Electron Laser Technology (December 2008)

 

Some recent Publications:

 

Click here complete  publication list

Terahertz laser modulation of electron beams, J.G Neumann, R.B. Fiorito, P.G. O'Shea, H. Loos, B. Sheehy, Y. Shen, Z. Wu, J. Appl. Phys. 105, 053304 (2009)

Time-dependent Phase Space Characterization of Intense Charged Particle Beams," Physical Review Special Topics - Accelerators & Beams  D. Stratakis, R.A. Kishek, R.B. Fiorito, K. Tian, I. Haber, P.G. O'Shea, M. Reiser, and J.C.T. Thangaraj,12, 020101 (2009).

Aperture effects and mismatch oscillations in an intense electron beam, J.R Harris, P.G. O’Shea, Phys. Plasmas 15, 123106 (2008)

Multicomponent measurements of the Jefferson Lab energy recovery linac electron beam using optical transition and diffraction radiation M.A. Holloway, R.B. Fiorito, A.G. Shkvarunets, P. G. O’Shea, S.V. Benson, D. Douglas, P. Evtushenko, and K. Jordan, Phys. Rev. ST Accel. Beams 11, 082801 (2008)

Theory of photoemission from cesium antimonide using an alpha-semiconductor model, K L Jensen, BL Jensen, EJ Montgomery, DW Feldman, PG O'Shea, and NA Moody, J. Appl. Phys. 104, 044907 (2008)

Electron emission contributions to dark current and its relation to microscopic field enhancement and heating in accelerator structures, K L. Jensen, Y. Y. Lau, D. W. Feldman and P. G. O’Shea, Phys. Rev. ST Accel. Beams 11, 081001 (2008)

Application of a general electron emission equation to surface nonuniformity and current density variation KL Jensen, JJ Petillo,  EJ Montgomery, ZG Pan, DW Feldman  PG O'Shea, NA Moody, M. Cahay, JE Yater, JL Shaw  J. Vac. Sc. & Tech B, 26, 831 (2008) 

Negative transconductance in apertured electron guns, J. R. Harris and P. G O'Shea, Journal of Applied  Physics. 103, 113301 (2008)

 

Time-Dependent Imaging of Space-Charge-Dominated Electron Beams, K. Tian, R.A. Kishek, P.G. O'Shea, R.B. Fiorito, D.W. Feldman, and M. Reiser,  Physics of Plasmas 15, 056707 (2008).

 

Longitudinal density modulation and energy conversion in intense beams J. R. Harris, J. G. Neumann, K. Tian, and P. G. O’Shea, Phys. Rev. E, 76 026402 (2007)

 

Theoretical model of the intrinsic emittance of a photocathode, K. L. Jensen P. G. O'Shea, D. W. Feldman, and N. A. Moody, Applied  Physics Letters. 89, 224103 (2006)

A photoemission model for low work function coated metal surfaces and its experimental validation, Kevin L. Jensen, Donald W. Feldman, Nathan A. Moody, and Patrick G. O'Shea, J. Appl. Phys. 99, 124905 (2006)

Field-enhanced photoemission from metals and coated materials, Kevin L. Jensen, Donald W. Feldman, Nathan A. Moody, and Patrick G. O'Shea, Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures 863, (2006)

Fixed-Geometry RMS Envelope Matching of Electron Beams from 'Zero' Current to Extreme Space-Charge, S. Bernal, H. Li, R.A. Kishek, B. Quinn, M. Walter, M. Reiser, P.G. O'Shea, and C.K. Allen,  Physical Review ST - Accelerators & Beams  9, 064202 (2006).

Tomography as a Diagnostic Tool for Phase Space Mapping of Intense Particle Beams, D. Stratakis, R.A. Kishek, H. Li, S. Bernal, M. Walter, B. Quinn, M. Reiser, and P.G. O'Shea, Physical Review Special Topics - Accelerators & Beams 9, 112801 (2006).

Gridded Electron Guns and Modulation of Intense Beams, J.R. Harris and P.G. O'Shea, IEEE Transactions on Electron Devices 53(11), 2824-2829 (2006).

Experimental observations of longitudinal space-charge waves in intense electron beams, K. Tian, Y. Zou, Y. Cui, I. Haber, R. A. Kishek, M. Reiser, and P. G. O’Shea, Physical  Review. ST Accel. Beams 9, 014201 (2006)

Governing factors for production of photoemission-modulated electron beams J. R. Harris, J. G. Neumann, and P. G. O'Shea, J. Appl. Phys. 99, 093306 (2006)

RMS envelope matching of electron beams from “zero” current to extreme space charge in a fixed lattice of short magnets, Bernal, H. Li, R. A. Kishek, B. Quinn, M. Walter, M. Reiser,  P. G. O’Shea, and C. K. Allen.  Phys. Rev. ST Accel. Beams 9, 064202 (2006)

Nonlinear Harmonic Generation in Free-Electron Lasers with Helical Wigglers, H.P. Freund, P.G. O’Shea, S. Biedron, Physical Review Letters, 94, 074802 (2005)  

Observation of anomalous increase of longitudinal energy spread in a space-charge dominated electron beam, Y. Zou, Y. Cui, M. Reiser, and P. G. O'Shea, Physical Review Letters,  94, 134801 (2005) 

 The quantum efficiency of dispenser photocathodes: Comparison of theory to experiment K. L. Jensen, D. W. Feldman and P.G. O’Shea, Applied  Physics  Letters. 85, 5448 (2004)

 

 

Vincit veritas


"Restraint in the pursuit of excellence is no virtue"

You and your career by Richard Hamming

Last updated March  2009