Faculty Directory

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: 

Design Considerations for Compact High-Average Power Free-Electron Lasers/Masers at Terahertz Frequencies (2023)

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:

How radiotherapy became a lifesaver – from X-rays to the proton beam

Will Proton Therapy Market Reach $1.6 Billion by 2031?

New Discoveries:

CERN's Large Hadron Collider poised to unlock more secrets of the universe

Exciting discovery from CERN

5 Myths About Patricle Acelerators 

Making Smaller Accelerators

Unresolved questions: Does warm water freeze faster than cool water?

Quantum News

Highlights

• Demonstrated space-charge limited current phenomena in the propagation of high-current, low-energy electron beams in solenoidal and gas-focused regimes.
• Demonstrated and studied an advanced accelerator concept known as the laser-controlled collective ion accelerator. Achieved an accelerating gradient for protons of 30 MV/m
• Developed record high brightness 1-MeV H^-and H^o beams on Beam Experiments Aboard Rocket (BEAR) test stand.
• Demonstrated autonomous operation of a directed energy experiment in space using a radio-frequency quadrupole H- accelerator. Studied propagation H^o, H^-, and H⁺ beams in geomagnetic field at an altitude of 200 km
• Demonstrated a high-current radio-frequency photocathode electron source as a driver for a high-gain infrared free-electron laser - first operation of a high-current RF photoinjector coupled to a linear accelerator.
• Demonstrated operation of electron photoinjector with space-charge emittance compensation whose brightness exceeded that of conventional sources by two orders of magnitude. Experimental confirmation of the theory of space charge emittance growth compensation.
• Demonstrated free-electron lasing from 370 nm to 11 µm using low-energy, high-brightness electron beam, and achieved a record short wavelength for a linear accelerator-driven FEL
• Member of the team that demonstrated inverse Compton γ-ray production using an FEL
• Developed a theory of reversible and irreversible emittance growth
• Electron beam production of medical radioisotopes
• Developed the nitrogen-laser-driven RF photoinjector
• Compact electron ring (UMER), an analog computer for beam physics studies in the space charge dominated regime; thermodynamics of beams and energy transfer mechanisms in beam systems. Discovery of solitary waves in electron beams.
• Developed dispenser photocathode electron source.
• Flat to round and round to flat transformation of beams with space charge and canonical angular momentum.
• New methods for generating high average power THz Free-Electron lasers
• Generating ultra-high peak power X-ray Free-Electron lasers

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)

ORCID ID

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 (2024)

Design Considerations for Compact High-Average Power Free-Electron Lasers/Masers at Terahertz Frequencies (2023)

A presentation by graduate student Liam Pocher won a best student paper award at NAPAC22

Watch Liam's talk, Optimizing the Discovery of Underlying Nonlinear Beam Dynamics, here

Some other interesting publications

Theory and Design of Charged Particle Beams   Martin Reiser, with contributions by Patrick O’Shea, Santiago Bernal, and Rami Kishek.

Free-Electron Lasers: Status and Applications

P.G. O’Shea and H. P. Freund, Science, 292, 1853 (2001)

 Electron Sources for Accelerators

C. Hernandez-Garcia, M. Stutzman, and P. G. O'Shea Physics Today, February 2008, page 44

Experimental Observations of Soliton Wave Trains in Electron Beams

Y.C. Mo, R.A. Kishek, D. Feldman, I. Haber, B. Beaudoin, P.G. O'Shea, and J.C.T. Thangaraj, Physical Review Letters 110, 084802 (2013).

Smooth Approximation of Dispersion with Strong Space Charge, S. Bernal, B.L. Beaudoin, T. Koeth, and P.G. O'Shea, Physical Review Special Topics - Accelerators & Beams 14, 104202 (2011).

Longitudinal Confinement and Matching of an Intense Electron Beam,

B. Beaudoin, I. Haber, R.A. Kishek, S. Bernal, T. Koeth, D. Sutter, P.G. O'Shea, and M. Reiser, " Physics of Plasmas 18, 013104 (2011).

Experimental study of large-amplitude perturbations in space-charge dominated beams,

 K. Tian, R.A. Kishek, I. Haber, M. Reiser, and P.G. O'Shea, Physical Review Special Topics - Accelerators & Beams 13, 034201 (2010).

Experimental veri

ion afication of tomographic phase-space imaging for beams with space-charge using a pinhole-scan,

D. Stratakis, R.A. Kishek, I. Haber, R.B. Fiorito, M. Reiser, and P.G. O'Shea Journal of Applied Physics 107, 104905 (2010)

Emittance of a field emission electron source,

K. L. Jensen, P. G. O'Shea, D. W. Feldman, and J. L. Shaw, J. Appl. Phys. 107, 014903 (2010)

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)

A 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)

Two-color operation in high-gain free-electron lasers

H. P. Freund and P.G. O’Shea, Physical Review Letters, 84 2861 (2000)

Publication Archive