Presently a conceptual design for a NIR-FIR FEL system at the National High Magnetic Field Lab. -... more Presently a conceptual design for a NIR-FIR FEL system at the National High Magnetic Field Lab. -Florida State University (NHMFL-FSU) is being undertaken in collaboration with the FEL group at the Thomas Jefferson Laboratory. The system is expected to combine high magnetic field research with an intense, tuneable photon source spanning the spectral region ~ 2 -1100 microns. Here, a design study involving the FIR/THz part of the NHMFL-FEL design proposal is presented. The suggested long-wavelength FEL encompasses in the first phase a thermionic injector with a ~2 mA average current and a ~10 MeV superconducting rf linac module operating at 1.3 GHz. The broadband outcoupling over the envisaged FIR/THz spectral range (100 -1100 microns) can be accomplished by adopting a variableoutcoupler scheme in a waveguided cavity. Besides the performance predictions of the suggested long wavelength FEL, techniques for the generation of high peak power, nanoseconds long THz pulses (for magnetic resonance applications) are also briefly discussed.
Jefferson Lab (JLab) is proposing JLAMP (JLab AMPlifier), a 4th generation light source covering ... more Jefferson Lab (JLab) is proposing JLAMP (JLab AMPlifier), a 4th generation light source covering the 10-100 eV range in the fundamental mode with harmonics stretching towards the oxygen k-edge. The new photon science user facility will feature a two-pass superconducting linac to accelerate the electron beam to 600MeV at repetition rates of 4.68MHz continuous wave. The average brightness from a seeded amplifier free electron laser (FEL) will substantially exceed existing light sources in this device's wavelength range, extended by harmonics towards 2 nm. Multiple photon sources will be made available for pump-probe dynamical studies. The status of the machine design and technical challenges associated with the development of the JLAMP are presented here.
Generation of THz radiation by excitation of InAs with a femtosecond free-electron laser
Ultrafast Electronics and Optoelectronics, 2001
Terahertz (THz) radiation is generated by exciting an un-doped InAs wafer with a femtosecond free... more Terahertz (THz) radiation is generated by exciting an un-doped InAs wafer with a femtosecond free-electron laser (FEL) at the Thomas Jefferson National Accelerator Facility. A microwatt level of THz radiation is detected from the unbiased InAs emitter when it is excited with the femtosecond FEL pulses operated at a wavelength of 1.06 μ-m and 10 W average power.
A new THz/IR/UV photon source at Jefferson Lab is the first of a new generation of light sources ... more A new THz/IR/UV photon source at Jefferson Lab is the first of a new generation of light sources based on an Energy-Recovered, (superconducting) Linac (ERL). The machine has a 160 MeV electron beam and an average current of 10 mA in 75 MHz repetition rate hundred femtosecond bunches. These electron bunches pass through a magnetic chicane and therefore emit synchrotron radiation. For wavelengths longer than the electron bunch the electrons radiate coherently a broadband THz ~ half cycle pulse whose average brightness is> 5 orders of magnitude higher than synchrotron IR sources. Previous measurements showed 20 W of 1 average power extracted[1]. The new facility offers simultaneous synchrotron light from the visible through the FIR along with broadband THz production of 100 fs pulses with>200 W of average power. The FELs also provide record-breaking laser power [2]: up to 10 kW of average power in the IR from 1 to 14 microns in 400 fs pulses at up to 74.85 MHz repetition rates and
Infrared and Millimeter Waves, Conference Digest of the 2004 Joint 29th International Conference on 2004 and 12th International Conference on Terahertz Electronics, 2004.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)
FEL Oscillators have been around since 1977 providing not only a test bed for the physics of Free... more FEL Oscillators have been around since 1977 providing not only a test bed for the physics of Free Electron Lasers and electron/photon interactions but as a workhorse of scientific research. More than 30 FEL oscillators are presently operating around the world spanning a wavelength range from the mm region to the ultraviolet using DC and rf linear accelerators and storage rings as electron sources. The characteristics that have driven the development of these sources are the desire for high peak and average power, high micropulse energies, wavelength tunability, timing flexibility, and wavelengths that are unavailable from more conventional laser sources. Substantial user programs have been performed using such sources encompassing medicine, biology, solid state research, atomic and molecular physics, effects of nonlinear fields, surface science, polymer science, pulsed laser vapor deposition, to name just a few. Recently the incorporation of energy recovery systems has permitted extension of the average power capabilities to the kW level and beyond. Moreover the use of collective radiation and Thompson/Compton scattering has produced substantial fluxes of THz radiation, X-rays, and gamma rays. This paper will discuss at a summary level the physics of such devices, survey existing and planned facilities, and touch on the applications that have driven the development of these popular light sources.
Observation of overdense infrared scattering from a post pinch plasma focus
Plasma Physics, 1981
Results of a collective CO2 laser scattering experiment performed on a dense plasma focus are rep... more Results of a collective CO2 laser scattering experiment performed on a dense plasma focus are reported. Scattering measurements were made at two incident beam polarizations both along the axis and transverse to the axis of a plasma focus in the pinch and post-pinch phases, and were combined with X-ray and neutron observations. Overdense scattering was observed in the post-pinch plasma and found to be spatially correlated with bright X-ray emitting regions detected by soft X-ray pinhole photographs. Underdense collective scattering was not observed, indicating that high-level turbulence is not present in the focus in the plasma frequency and wave vector domain measured, and suggesting that any localized turbulence may only be indirectly related to ion heating.
Pediatricians can alert children and their families to emerging issues they may not be aware of t... more Pediatricians can alert children and their families to emerging issues they may not be aware of that can help prevent illness. One such issue is an increased number of enteric illness outbreaks detected by public health surveillance that are linked to pet ownership and animal contact. Roughly 74 million U.S. households have one or more pets, according to the American Veterinary Medical Association. Pet ownership and other types of animal contact provide many benefits to people. However, certain animals are not appropriate pets for high-risk groups, including children under 5 years of age, immunocompromised persons and adults over 65 years of age. Enteric illnesses such as Salmonella, Escherichia coli O157:H7 and Campylobacter are most commonly transmitted through contaminated food. However, these bacteria are among the many zoonotic pathogens that pets and other animals can spread to people. Illnesses and outbreaks of enteric zoonotic diseases (i.e., zoonoses) have been linked to exposure to many different kinds of animals in public and private settings (MMWR Recomm Rep. 2011;60[RR-04]:1-24). In addition to pet ownership, public venues such as animal exhibits, farms, stores, schools and child care facilities offer opportunities for children to contact animals. Petting zoos and backyard poultry flocks also are becoming increasingly popular. Salmonella infections can occur in individuals who have contact with certain types of animals, such as turtles and other reptiles; aquatic frogs and other amphibians; live poultry; hedgehogs; and rodents such as mice, hamsters and guinea pigs. Campylobacter infections also can be transmitted though contact with animals, particularly farm animals such as cattle and poultry, as well as
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2001
A distributed optical klystron has the potential for dramatically shortening the total interactio... more A distributed optical klystron has the potential for dramatically shortening the total interaction length in high-gain free-electron lasers (INP 77-59, Novosibirsk, 1977; Nucl. Instr. and Meth A 304 (1991) 463) in comparison to a singlewiggler-segment configuration. This shortening can be even more dramatic if a nonlinear harmonic generation mechanism is used to reach the desired wavelength. An example operating at a 4.5 ( A fundamental and a 1.5 ( A harmonic is discussed.
High-power infrared and ultraviolet free electron lasers at CEBAF
AIP Conference Proceedings, 1992
ABSTRACT In response to requirements for national laboratory technology transfer, CEBAF has propo... more ABSTRACT In response to requirements for national laboratory technology transfer, CEBAF has proposed an industrial R&D initiative: a Free Electron Laser (FEL) User Facility based on an infrared FEL and an ultraviolet FEL, with the injector and the north linac of the CEBAF superconducting, recirculating accelerator serving as drivers. The initiative is a collaborative effort with four U.S. corporate partners and capitalizes on CEBAF's superconducting rf technology. The FELs will provide monochromatic, tunable (3.6 to 1.7 mum and 150 to 260 nm), high-average-power (-kW) light for technical applications and basic science studies. FEL capabilities will be competitive with those of similar initiatives worldwide. FEL operation will not impair beam delivered to CEBAF's nuclear physics experiments. Substational commitments are in hand from the industray partners and the Commonwealth of Virgina for cost-sharing the project with the Federal Government.
Bunch Length Measurements at the JLab FEL Using Coherent Transition and Synchrotron Radiation
AIP Conference Proceedings, 2006
The JLab FEL is routinely operated with sub‐picosecond bunches. The short bunch length is importa... more The JLab FEL is routinely operated with sub‐picosecond bunches. The short bunch length is important for high gain of the FEL. Coherent transition radiation has been used for the bunch length measurements for many years. This diagnostic can be used only in the pulsed ...
A high brightness sub-picosecond x-ray source can be created by installing an undulator at Jeffer... more A high brightness sub-picosecond x-ray source can be created by installing an undulator at Jefferson Lab's CEBAF, a nuclear physics electron accelerator. Although the beam current is only 100 microamps, the electron beam has an extremely small emittance and energy spread, with the result that one can produce x-ray beams tunable over the range 5-30keV with an average brightness quite comparable to beamlines at the Advanced Photon Source (APS) at Argonne National Lab. In addition, with rms bunch lengths measured down to 85 fsecs, peak brightness values are much higher than at the APS. Furthermore, this x-ray source has similar emittance in both horizontal and vertical directions, (a socalled round beam) making it of very high potential for many applications. In order to determine if indeed such a source is worth pursuing we present "tuning curve" calculations of peak and average flux and brightness for an undulator on CEBAF. They are compared with similar calculations for a dipole and for undulator-A at the APS. Finally we calculate the impact of such a device on the CEBAF beam itself itself and find it to be much smaller than the natural energy spread of the beam.
The availability of high-power, high-brilliance sources of tunable photons from energy-recovered ... more The availability of high-power, high-brilliance sources of tunable photons from energy-recovered Free Electron Lasers is opening up whole new fields of application of accelerators in industry. This will review some of the ideas that are already being put into production, and some of the newer ideas that are still under development.
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Papers by George Neil