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Novel probe for determining the size and position of a relativistic electron beam

Description: In order to determine the size and position of a relativistic electron beam inside the wiggler magnetic field of a Free Electron Laser (FEL), we have developed a new probe which intercepts the electron beam on a high Z target and monitors the resulting bremsstrahlung radiation. The probe is designed to move along the entire three meters of the wiggler. This FEL is designed to operate in the microwave region (2 to 8 mm) and the interaction region is an oversized waveguide with a cross section 3 cm x 9.8 cm. The axial probe moves inside this waveguide. The probe stops the electron beam on a Tantalum target and the resulting x-rays are scattered in the forward direction. A scintillator behind the beam stop reacts to the x-rays and emits visible light in the region where the x-rays strike. An array of fiber optics behind the scintillator transmits the visible light to a Reticon camera system which images the visible pattern from the scintillator. Processing the optical image is done by digitizing and storing the image and/or recording the image on video tape. Resolution and performance of this probe will be discussed.
Date: July 23, 1984
Creator: Orzechowski, T.J.; Koehler, H.; Edwards, W.; Nelson, M. & Marshall, B.
Partner: UNT Libraries Government Documents Department

Chirping for efficiency enhancement of the free-electron laser

Description: One-dimensional numerical studies have been made of free-electron laser oscillators in which the incident electron energy varies (chirps) as a function of time over each micropulse. Optical radiation resonant with such micropulses is chirped in frequency. Highest calculated efficiency (up to 8.1% for wavelengths near 10 ..mu..m) has been obtained in cases where the optical pulse at saturation is short compared to the slippage. 8 refs., 7 figs., 1 tab.
Date: January 1, 1988
Creator: Moore, G.T. & Goldstein, J.C.
Partner: UNT Libraries Government Documents Department

New concepts in microwave sources for e/sup -/e/sup +/ supercolliders

Description: The realization of e/sup -/e/sup +/ supercolliders will require advances in tehnology including the development of x-band microwave amplifiers with pulse energy > 60 J. Candidate microwave amplifiers include klystrons, lasertrons, free electron lasers (FEL's), and gyrotrons; gyrotron amplifiers employing a multicavity gyroklystron configuration appear advantageous at lambda approx. = 3 cm. Measurements on a 50 kW, 1 ..mu..s gyroklystron show phase jitter < 0.75/sup 0/ indicating compatibility of this type of amplifier with collider requirements. The University of Maryland is currently developing an x-band, TE/sup 0//sub 01/ mode gyroklystron driven by 500 keV, 160 A, 2 ..mu..s electron beam pulses; combining this tube with a TE/sup 0//sub 01/ binary pulse compression circuit under development at SLAC could produce 475 MW, 120 ns microwave pulses which imply the feasibility of achieving linac accelerating fields in the range 100-200 MV/m.
Date: January 1, 1986
Creator: Granatstein, V.L.; McAdoo, J.H.; Striffler, C.D.; Lawson, W.; Latham, P.E. & Reiser, M.
Partner: UNT Libraries Government Documents Department

Optimization of the parameters of a storage ring for a high power XUV free electron laser

Description: In this paper we describe the operation of an XUV high gain FEL operating within a bypass of an electron storage ring, and discuss the implications on storage ring optimization imposed by FEL requirements. It transpires that, in the parameter regime of interest, collective effects within the beam play an important role. For example, intrabeam scattering dilutes the transverse emittance of the beam and the microwave instability increases the momentum spread. Both phenomena reduce the effectiveness of the FEL. A computer code, ZAP, has been written which, for a given lattic design, takes all such effects into consideration and produces a figure of merit for FEL operation for that machine. We show the results of ZAP for several storage ring designs, all optimized for FEL operation, and present a design example of a facility capable of producing coherent radiation at 400 A with tens of megawatts of peak power.
Date: October 1, 1985
Creator: Jackson, A.; Bisognano, J.; Chattopadhyay, S.; Cornacchia, M.; Garren, A.; Halbach, K. et al.
Partner: UNT Libraries Government Documents Department

Short-pulse free-electron-laser amplifier

Description: Method and apparatus for amplification of a laser pulse in a free-electron-laser amplifier where the laser pulse duration may be a small fraction of the electron-beam-pulse duration used for amplification. An electron-beam pulse is passed through a first wiggler magnet and a short laser pulse to be amplified is passed through the same wiggler so that only the energy of the last fraction, f, (f < 1) of the electron-beam pulse is consumed in amplifying the laser pulse. After suitable delay of the electron beam, the process is repeated in a second wiggler magnet, a third, ..., where substantially the same fraction f of the remainder of the electron-beam pulse is consumed in amplification of the given short laser pulse in each wiggler magnet region until the useful electron-beam energy is substantially completely consumed by amplification of the laser pulse.
Date: January 26, 1982
Creator: Schlitt, L.G. & Szoke, A.
Partner: UNT Libraries Government Documents Department

Analysis of self-amplified spontaneous emission

Description: The analysis develops a classical theory of how a signal evolves from the initial incoherent spontaneous emission in long undulators. The theory is based on the coupled Klimontovich-Maxwell equations. Formulas for the radiated power, spectral characteristics and electron correlations are derived. The saturation due to nonlinear effects is studied using a quasi-linear extension of the theory. The results agree reasonably well with the recent Livermore experiment in the microwave range. Performance of a possible high-gain free electron laser in a short-wavelength region is evaluated.
Date: November 1, 1985
Creator: Kim, K.J.
Partner: UNT Libraries Government Documents Department

Experimental and theoretical investigation of high gradient acceleration. Progress report, June 1, 1991--February 1, 1992

Description: This report contains a technical progress summary of the research conducted under the auspices of DOE Grant No. DE-FG0291ER-40648. ``Experimental and Theoretical Investigations of High Gradient Acceleration.`` This grant supports three research tasks: Task A consists of the design and fabrication of a 17GHz of photocathode gun, Task B supports the testing of high gradient acceleration using a 33GHz structure, and Task C comprises theoretical investigations, both in support of the experimental tasks and on critical physics issues for the development of high energy linear colliders. This report is organized as follows. The development of an rf gun design and research progress on the picosecond laser system is summarized in Sec. 2, the status of the studies of the LBL/Haimson high gradient structure, using a 50 MW free-electron laser is summarized in Sec. 3, and theoretical research progress is described in Sec. 4. Supporting material is contained in Appendices A-G.
Date: February 1, 1992
Creator: Bekefi, G.; Chen, C.; Chen, S.; Danly, B.; Temkin, R. J. & Wurtele, J. S.
Partner: UNT Libraries Government Documents Department

New techniques for particle accelerators

Description: A review is presented of the new techniques which have been proposed for use in particle accelerators. Attention is focused upon those areas where significant progress has been made in the last two years--in particular, upon two-beam accelerators, wakefield accelerators, and plasma focusers. 26 refs., 5 figs., 1 tab.
Date: June 1, 1990
Creator: Sessler, A.M.
Partner: UNT Libraries Government Documents Department

Proposed UV-FEL user facility at BNL

Description: The NSLS at Brookhaven National Laboratory is proposing the construction of a UV-FEL operating in the wavelength range from visible to 1000{angstrom}. Nano-Coulomb electron pulses will be generated at a laser photo-cathode RF gun at a repetition rate of 10 KHz. The 6 ps pulses will be accelerated to 250 MeV in a superconducting linac. The FEL consists of an exponential growth section followed by a tapered section. The amplifier input is a harmonic of a tunable visible laser generated either by nonlinear optical material or the non-linearity of the FEL itself. The FEL output in 10{sup {minus}4} bandwidth is 1 mJ per pulse, resulting in an average power of 10 watts. The availability of radiation with these characteristics would open up new opportunities in photochemistry, biology and non linear optics, as discussed in a recent workshop held at BNL. 10 refs., 4 figs., 1 tab.
Date: January 1, 1990
Creator: Ben-Zvi, I.; Di Mauro, L.F.; Krinsky, S.; White, M.G. & Yu, L.H.
Partner: UNT Libraries Government Documents Department

The Ion-Channel Laser

Description: A relativistic electron beam propagating through a plasma in the ion-focused regime exhibits an electromagnetic instability at a resonant frequency {omega} {approximately} 2{gamma}{sup 2} {omega}{sub {beta}}. Growth is enhanced by optical guiding in the ion channel, which acts as dielectric waveguide, with fiber parameter V {approximately} 2 (I/I{sub A}){sup 1/2}. A 1-D theory for such an ion-channel laser'' is formulated, scaling laws are derived and numerical examples are given. Possible experimental evidence is noted. 23 refs., 1 fig., 1 tab.
Date: January 1990
Creator: Whittum, D. H.; Sessler, A. M. & Dawson, J. M.
Partner: UNT Libraries Government Documents Department

The performance of a superconducting micro-undulator prototype

Description: We report on the performance of a prototype of a super-ferric micro-undulator. The micro-undulator consists of a continuous winding of niobium-titanium wire wound on a low carbon steel yoke. It is about 3 periods long with a period of 8.8 mm and a gap of 4.4 mm. The undulator achieves the a peak magnetic field on axis of over 0.5 Tesla. Asymmetry of the field pattern due to a dipole component was identified, analyzed and a correction has been applied to the undulator ends to produce a symmetric field distribution. Within the precision of the measurement the field pattern produced by the super-ferric undulator needed no correction. 4 refs., 7 figs.
Date: May 1, 1990
Creator: Ben-Zvi, I.; Jiang, Z.Y.; Ingold, G.; Yu, L.H. & Sampson, W.B.
Partner: UNT Libraries Government Documents Department

Development of the MIT tabletop soft x-ray laser

Description: We have been developing a small-scale EUV laser facility at MIT with which we hope to observe gain in nickel-like molybdenum at 191 {angstrom}. The physics involved in the formation of laser gain is examined through the use of simple models, and optimum operating temperatures and electron densities are determined. The upper state population is determined primarily through a balance between direct collisional excitation to and from the upper laser state; the lower state population follows primarily from a balance between indirect excitation and radiative decay. Models describing these balances are used to estimate optimum conditions and the resulting population inversions.
Date: December 31, 1991
Creator: Hagelstein, P. L.
Partner: UNT Libraries Government Documents Department

Photoelectrons beam measurement from a magnesium cathode in a RF electron gun

Description: The performance of a magnesium cathode in a one-and-half cell photocathode RF gun measured at the Brookhaven Accelerator Test Facility (ATF). The frequency quadrupled Nd:YAG laser (266 nm) was used to stimulate the photoelectron emissions. For a normal incident laser pulse, the quantum efficiency of the magnesium at 10{sup {minus}7} torr was measured to be 5 {times} 10{sup {minus}4}, which is more than 20 times the value for copper under similar conditions.
Date: September 1, 1994
Creator: Wang, X. J.; Srinivasan-Rao, T.; Batchelor, K.; Ben-Zvi, I. & Fischer, J.
Partner: UNT Libraries Government Documents Department

The visible Smith-Purcell radiation search

Description: We report here the results of an experiment at the Accelerator Test Facility at Brookhaven National Laboratory to search for the production of visible radiation from the Smith-Purcell effect using a 3 MeV electron beam. After running the experiment under a variety of conditions we were unable to isolate a definite signal from Smith-Parcell effect. Any Smith-Purcell signal present in the measured radiation was less than 10% of the background signal.
Date: March 1, 1994
Creator: Fernow, R. C.; Kirk, H. G. & Ulc, S. Wang, X.
Partner: UNT Libraries Government Documents Department

Laser powered beam conditioner for free-electron lasers and synchrotrons

Description: A new method of using an additional laser for electron beam conditioning in free-electron lasers (FELs) and synchrotrons is proposed. Theoretical analysis and calculations are presented, showing that the axial energy spread of electrons due to their betatron motion in undulators can be dramatically reduced by interacting with a quasi-TEM{sub 10} Gaussian mode optical beam. It is requried that the electrons be prebunched over half an optical cycle in advance.
Date: June 1, 1993
Creator: Liu, H.; Neil, G. R.; Sinclair, C. & Yunn, B.
Partner: UNT Libraries Government Documents Department

The UV-FEL at the NSLS: Straight injection configuration

Description: We present a design of a colinear RF-photocathode gun and linac sections for the ultraviolet free-electron laser under study at the National Synchrotron Light Source. Inverse Helmholtz solenoid pair is used to control the divergence of the electron beam and present a slightly convergent and small beam into a conventional SLAC linac. The relative distance of the gun to the linac and the strength of the solenoidal field are chosen to minimize the emittance growth of the beam due to space charge. The simulation codes PARMELA and TRACE-3D are used to model the beam from the cathode to the entrance to the wiggler.
Date: July 1, 1993
Creator: Zhang, Xiaohao & Gallardo, Juan C.
Partner: UNT Libraries Government Documents Department

A proposal for the generation of ultra-short x-ray pulses

Description: In this paper it is shown that optical stochastic cooling in a 150 MeV electron storage ring will allow production of a beam with longitudinal emittance 4.5 {times} 10{sup {minus}6} MeV{center_dot}m. Such a small emittance accompanied with a bunch compression technique based upon the transformation in the longitudinal phase space will allow achieving a bunch length 30 {mu}m. This bunch could then be used for the generation of ultra-short x-ray pulses by the Compton scattering of laser photons.
Date: August 1, 1994
Creator: Zholents, A. A. & Zolotorev, M. S.
Partner: UNT Libraries Government Documents Department

Inverse free electron laser beat-wave accelerator research. Annual progress report, [August 1992--September 1993]

Description: A calculation on the stabilization of the sideband instability in the free electron laser (FEL) and inverse FEL (IFEL) was completed. The issue arises in connection with the use of a tapered (``variable-parameter``) undulator of extended length, such as might be used in an ``enhanced efficiency`` traveling-wave FEL or an IFEL accelerator. In addition, the FEL facility at Columbia was configured as a traveling wave amplifier for a 10-kW signal from a 24-GHz magnetron. The space charge field in the bunches of the FEL was measured. Completed work has been published.
Date: September 1, 1993
Creator: Marshall, T. C. & Bhattacharjee, A.
Partner: UNT Libraries Government Documents Department

Grazing incidence absorption measurements. Final report

Description: This final report summarizes the results of a series of different measurements to characterize various mirrors of interest to Los Alamos National Laboratory and the Boeing Aerospace free electron laser program. Most of the measurements were of the glancing incidence characteristics of different overcoated silver mirrors. These included the absolute absorptance as a function of angle of incidence (0--88{degrees}), laser wavelength (0.5145 and 1.06 {mu}m), polarization, and exposure to room air. The latter measurement examined the ability of the overcoated silver mirrors to resist tarnishing. Overcoating materials used were single-layer ThF{sub 4} and MgF{sub 2}, a very thin layer of Al{sub 2}O{sub 3}, and diamond. As a result of the work performed during this program, significant progress has been made to find a better alternative to bare silver mirrors for high-power laser applications. Thick dielectric overcoats do protect the silver mirrors from tarnishing, but problems associated with accurately controlling the optical constants of the dielectric during the coating process appear to make it difficult to achieve the desired optical properties of the mirrors at high angles of incidence.
Date: July 31, 1989
Partner: UNT Libraries Government Documents Department

Design of dispersion section for the ATF harmonic generation FEL

Description: We present an analysis of the dispersion magnet for the high gain harmonic generation experiment to be carried out at the Accelerator Test Facility at BNL. The purpose of the dispersion magnet is to convert energy modulation of the electron beam into spatial bunching. For the dispersion magnet, we discuss the physical requirements, analyze the magnetic design, determine the focusing properties, and consider the effect on the FEL gain of departures from idea behavior on the FEL gain.
Date: October 1, 1992
Creator: Zhang, X.; Ben-Zvi, I.; Ingold, G.; Krinsky, S. & Yu, L. H.
Partner: UNT Libraries Government Documents Department

End effects and orbit correction in the wiggler for the ATF harmonic generation FEL

Description: In this paper, we consider the superconducting wiggler magnet under construction for the High Gain Harmonic Generation experiment (HGHG) at the Accelerator Test Facility (ATF) at BNL. We analyze the effects due to the ends of the wiggler and discuss their correction. In addition, the localized field produced by a trim coil for horizontal beam steering is investigated.
Date: October 1, 1992
Creator: Zhang, X.; Ben-Zvi, I.; Ingold, G.; Krinsky, S. & Yu, L. H.
Partner: UNT Libraries Government Documents Department

Photoemission from Ag, Cu, and CsI

Description: Photoemission characteristics of three different cathodes, CsI, Ag film and Cu were investigated. CsI, upon irradiation by 213 nm, 10ps laser pulse yields a quantum efficiency of 4% at O.2{mu}J input energy. The saturation mechanism observed at higher input energies require further investigation. Ag film, upon irradiation by 630 nm, 300 fs laser emit prompt photoelectrons after absorbing 2 photons. There was no evidence of optical damage of the film up to 10{sup 11} W/cm{sup 2}. At low intensities, photoemission from Cu is a simple {nu}-e{sup {minus}} interaction, the nonlinearity of the process depending strongly on trace impurities. At higher intensities, there appears to be a change in the emission mechanism.
Date: June 1, 1992
Creator: Srinivasan-Rao, T.; Fischer, J. & Tsang, T.
Partner: UNT Libraries Government Documents Department

Microcavity structures

Description: The feasibility of building mm-wave cavities using deep x-ray lithography techniques is being investigated. These cavities could be considered for linac accelerating structures, undulators, free electron lasers, or mm-wave amplifiers. The construction process includes making precision x-ray masks, x-ray exposure of poly-methyl-methacrylate (PMMA), removal of PMMA, and electroplating a metal. Highly precise two-dimensional features can be machined onto wafers by this technique. The challenge is to fabricate the wafers onto three-dimensional rf structures. Rectangular cavity geometry is best suited to this fabrication technique. Status of wafer manufacture, fabrication and alignment techniques using capillaries bonded in precision grooves, 2{pi}/3 120-GHz linac structures, heat extraction analysis, and beam dynamics in a 5-meter-long 50-MeV linac will be discussed. Measurements made on 10X larger scale models that were built with conventional techniques will also be discussed.
Date: October 1, 1994
Creator: Kustom, R. L.; Grudzien, D. & Feinerman, A. D.
Partner: UNT Libraries Government Documents Department

Demonstration of ultraviolet lasing with a low energy electron beam

Description: We report on the design details of the first ultraviolet (UV) free-electron laser (FEL) oscillator driven by low-energy electrons from a radio-frequency linear accelerator. In our experiment we used a high-current, high brightness electon beam in combination with a wiggler of novel design to produce an FEL that lased at wavelengths from 369--380 nm using 45.9--45.2 MeV electrons. In addition we performed a proof-of principle experiment that demonstrated the first ever photolithography on a photoresist-coated silicon wafer using an FEL light source.
Date: August 10, 1993
Creator: O`Shea, P. G.; Bender, S. C. & Byrd, D. A.
Partner: UNT Libraries Government Documents Department