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Coherent transition radiation produced by a 1.2 MeV electron beam

Description: We describe a method of generating very high-frequency coherent radiation using an electron beam source with a maximum beam energy of 1.2 MeV. We show that, though the high frequency cutoff for the radiation generated when the beam impacts a target at normal incidence is reduced by transverse beam size effects, it is nevertheless possible to generate much higher frequencies by a judicious choice of the angles of incidence and observation. 5 refs., 4 figs., 1 tab.
Date: December 31, 1995
Creator: Benson, S.V.; Dutta, J.M.; Jones, C.R.; Kosai, H. & Swartz, J.
Partner: UNT Libraries Government Documents Department

Radio-Frequency Beam Conditioner for Fast-Wave Free-Electron Generators of Coherent Radiation

Description: A method for conditioning electron beams is proposed, making use of the TM{sub 210} mode of microwave cavities, to reduce the axial velocity spread within the beam, in order to enhance gain in resonant electron beam devices, such as the free-electron laser (FEL). Effectively, a conditioner removes the restriction on beam emittance. The conditioner is analyzed using a simple model for beam transport and ideal RF cavities. Analysis of an FEL is employed to evaluate performance with reduced axial velocity spread. Examples of FELs are presented showing the distinct advantage of conditioning.
Date: July 1, 1991
Creator: Sessler, Andrew M.; Whittum, D.H. & Yu, L.
Partner: UNT Libraries Government Documents Department

Transverse Coherence Properties of the LCLS X-Ray Beam

Description: Self-amplifying spontaneous radiation free-electron lasers, such as the LCLS or the European X-FEL, rely on the incoherent, spontaneous radiation as the seed for the amplifying process. Though this method overcomes the need for an external seed source one drawback is the incoherence of the effective seed signal. The FEL process allows for a natural growth of the coherence because the radiation phase information is spread out within the bunch due to slippage and diffraction of the radiation field. However, at short wavelengths this spreading is not sufficient to achieve complete coherence. In this presentation we report on the results of numerical simulations of the LCLS X-ray FEL. From the obtained radiation field distribution the coherence properties are extracted to help to characterize the FEL as a light source.
Date: April 16, 2007
Creator: Reiche, S.
Partner: UNT Libraries Government Documents Department

Measurement of subpicosecond electron pulse length

Description: A new frequency-resolved bunch-length measuring system has been developed at the Stanford SUNSHINE facility to characterize subpicosecond electron pulses. Using a far-infrared Michelson interferometer, this method measures the spectrum of coherent transition radiation emitted from electron bunches through optical autocorrelation. The electron bunch length is obtained from the measurement with a simple and systematic analysis which includes interference effects caused by the beam splitter. This method demonstrates subpicosecond resolving power that cannot be achieved by existing time-resolved methods. The principle of this method and experimental results are discussed.
Date: April 1, 1996
Creator: Lihn, Hung chi
Partner: UNT Libraries Government Documents Department

Electron beam instrumentation techniques using coherent radiation

Description: Much progress has been made on coherent radiation research since coherent synchrotron radiation was first observed in 1989. The use of coherent radiation as a bunch length diagnostic tool has been studied by several groups. In this paper, brief introductions to coherent radiation and far-infrared measurement are given, the progress and status of their beam diagnostic application are reviewed, different techniques are described, and their advantages and limitations are discussed.
Date: June 1, 1997
Creator: Wang, D.X.
Partner: UNT Libraries Government Documents Department

Coherent synchrotron radiation in the isochronous muon collider ring

Description: To achieve the luminosity of L = 10{sup 35} cm{sup {minus}2}s{sup {minus}1} in a {mu}{sup +}{mu}{sup {minus}} collider, two bunches per sign of N = 2 {times} 10{sup 12} particles each and a betatron function of {beta}* = 3 mm at the interaction point (IP) are required. This small {beta}* at the IP constrains the size of the bunch to be {sigma}{sub z} {approximately} {beta}*. To maintain this rather short bunch without excessive rf power consumption, an isochronous lattice has been chosen for the final collider ring. One of the important advantages of muons as opposed to electrons is that at up to at least TeV energy it is possible to accelerate muons in circular machines as their synchrotron radiation is reduced by a factor of (m{sub e}/m{sub {mu}}){sup 2} {approximately} 23 {times} 10{sup {minus}6} with respect to electrons. Nevertheless, the large number of muons in a short bunch suggests the possibility of strong shielded coherent synchrotron radiation. First, the author uses the well known formulae to evaluate the power of shielded coherent synchrotron radiation in the isochronous muon collider ring. Finally, following the results obtained by Kheifets and Zotter for a bunch with a Gaussian longitudinal charge distribution the author shows that the coherent synchrotron radiation in the isochronous {mu}{sup +}{mu}{sup {minus}} collider ring is negligible if the rms bunch length is larger than {approx} 0.3 mm.
Date: October 1, 1996
Creator: Gallardo, J.C.
Partner: UNT Libraries Government Documents Department

Nonuniform Liouville transformers for quasi-homogeneous optical fields. Final technical report, September 25, 1989--January 22, 1993

Description: During the last two decades, there have been dramatic improvements in the development of optical sources. Examples of this development range from semiconductor laser diodes to free electron beam lasers and synchrotron radiation. Before these developments, standards for the measurement of basic optical parameters (quantities) were less demanding. Now, however, there is a fundamental need for new, reliable methods for providing fast quantitative results for a very broad variety of optical systems and sources. This is particularly true for partially coherent optical beams, since all optical sources are either fully or partially spatially coherent (including Lambertian sources). Until now, there has been no satisfactory solution to this problem. During the last two decades, however, the foundations of physical radiometry have been developed by Walther, Wolf and co-workers. By integrating physical optics, statistical optics and conventional radiometry, this body of work provides necessary tools for the evaluation of radiometric quantities for partially coherent optical beams propagating through optical systems. In this program, Physical Optics Corporation (POC) demonstrated the viability of such a radiometric approach for the specific case of generalized energy concentrators called Liouville transformers. We believe that this radiometric approach is necessary to fully characterize any type of optical system since it takes into account the partial coherence of radiation. 90 refs., 57 figs., 4 tabs.
Date: March 1, 1993
Creator: Jannson, T.
Partner: UNT Libraries Government Documents Department

Smith-Purcell radiation from a 50 MeV beam

Description: A 50 MeV electron beam and a 1 mm period, 5{degree} blaze, echelle grating have been used to produce radiation in the mid-infrared spectral region. The emission is highly collimated and forward-directed. The intensity level in the few ps pulse (2 nJ/sr) indicates a degree of coherent enhancement.
Date: October 1, 1996
Creator: Brownell, J.H.; Walsh, J.; Kirk, H.G.; Fernow, R.C. & Robertson, S.H.
Partner: UNT Libraries Government Documents Department

Analysis on the steady-state coherent synchrotron radiation with strong shielding

Description: There are several papers concerning shielding of coherent synchrotron radiation (CSR) emitted by a Gaussian line charge on a circular orbit centered between two parallel conducting plates. Previous asymptotic analyses in the frequency domain show that shielded steady-state CSR mainly arises from harmonics in the bunch frequency exceeding the threshold harmonic for satisfying the boundary conditions at the plates. In this paper the authors extend the frequency-domain analysis into the regime of strong shielding, in which the threshold harmonic exceeds the characteristic frequency of the bunch. The result is then compared to the shielded steady-state CSR power obtained using image charges.
Date: June 1, 1997
Creator: Li, R.; Bohn, C. L. & Bisognano, J. J.
Partner: UNT Libraries Government Documents Department

Coherent synchrotron radiation and stability of a short bunch in a compact storage ring

Description: It should be possible to observe coherent synchrotron radiation at millimeter wavelengths in a compact electron storage ring, provided that the bunch can be made sufficiently short. On the other hand, for a short bunch the radiation reaction is so strong that it could cause a longitudinal instability if the current exceeded some threshold. This might cause bunch lengthening, and cut off or reduce the coherent radiation. Using wake fields from simple models of the vacuum chamber, the authors estimate the threshold current for a proposed upgrade of the Brookhaven small x-ray light source, SXLS-Phase 1.
Date: June 1, 1995
Creator: Warnock, R.L. & Bane, K.
Partner: UNT Libraries Government Documents Department

Evidence for millimeter-wave coherent emission from the NSLS VUV ring

Description: Coherent synchrotron radiation from the NSLS VUV ring has been detected and partially characterized. The observations have been performed at the new far infrared beamline U12IR. The coherent radiation is peaked near a wavelength of 7mm and occurs in short duration bursts. The bursts occur only when the electron beam current (I) exceeds a threshold value (I{sub th}), which itself varies with ring operating conditions. Beyond threshold, the average intensity of the emission is found to increase as (I-I{sub th}). The coherent emission implies micro-bunching of the electron beam due to a longitudinal instability.
Date: July 19, 1999
Creator: Carr, G.L.
Partner: UNT Libraries Government Documents Department

EVIDENCE FOR MILLIMETER-WAVE COHERENT EMISSION FROM THE NSLS VUV RING.

Description: Coherent synchrotron radiation from the NSLS VUV ring has been detected and partially characterized. The observations have been performed at the new far infrared beamline U12IR. The coherent radiation is peaked near a wavelength of 7mm and occurs in short duration bursts. The bursts occur only when the electron beam current (I) exceeds a threshold value (I{sub th}), which itself varies with ring operating conditions. Beyond threshold, the average intensity of the emission is found to increase as (I-I{sub th}). The coherent emission implies micro-bunching of the electron beam due to a longitudinal instability.
Date: July 19, 1999
Creator: CARR,G.L.
Partner: UNT Libraries Government Documents Department

Phase mixing of chaotic orbits as an irreversible ''relaxation'' mechanism

Description: Orbits that are chaotic will tend to phase-mix exponentially through their accessible phase space. This phenomenon, commonly called ''chaotic mixing'', stands in marked contrast to phase mixing of regular orbits. It is inherently irreversible, and thus its associated e-folding time scale sets a condition on any process envisioned for emittance compensation. Accordingly, two questions arise. First, under what conditions does chaotic mixing manifest itself in beams? Second, when it is active, over what time scale does it operate? The work described here is part of an ongoing effort to answer these questions.
Date: January 15, 2002
Creator: al., C.L. Bohn et
Partner: UNT Libraries Government Documents Department

Intense, broadband far-IR/THZ radiation from the Jlab FEL

Description: The authors calculate the spectral output from a dipole magnet in the energy recovery system of the Jefferson Laboratory Free Electron Laser (FEL) in the 1--10,000 cm{sup {minus}1} (1 micron to 1 cm) range. They show that due to multiparticle coherent enhancement (coherent synchrotron radiation or CSR), the emission contains almost 1 watt/cm{sup {minus}1} of power emitted into the diffraction limit. For the purpose of this illustrative calculation they assume some typical parameters for the machine, namely that they have 100 pico-coulomb electron bunches at a 37.4 MHz repetition rate. They also assumed full width half maximum (fwhm) horizontal and vertical beam sizes of 200 microns. They took the electron beam energy to be 40 MeV, the bending radius to be 1m, and they extracted 90 x 90 milliradians of light (approximately an {line_integral}/11 beam).
Date: February 12, 2001
Creator: Williams, Gwyn P.
Partner: UNT Libraries Government Documents Department

THE DUV-FEL DEVELOPMENT PROGRAM

Description: We discuss the design and output radiation parameters for the Deep Ultra-violet Free Electron Laser at BNL, which will generate coherent output down to 100 nm using High Gain Harmonic Generation. The result of FEL calculation and the status of the experiment are presented.
Date: June 18, 2001
Creator: YU,L.H.; DIMAURO,L.F.; DOYURAN,A.; GRAVES,W.; JOHNSON,E.; KRINSKY,S. et al.
Partner: UNT Libraries Government Documents Department

Millimeter wave coherent synchrotron radiation in a compact electron storage ring

Description: Installation of a 2,856 MHz RF system into the XLS compact electron storage ring would allow the generation of millimeter wave coherent synchrotron radiation. Operating at 150 MeV, one could produce bunches containing on the order of 2 {times} 10{sup 7} electrons with a bunch length {sigma}{sub L0} = 0.3 mm, resulting in coherent emission at wavelengths above 0.8 mm. The characteristics of the source and the emitted radiation are discussed. In the case of 100 mrad horizontal collection angle, the average power radiated in the wavelength band 1 mm {le} {lambda} {le} 2 mm is 0.3 mW for single bunch operation and 24 mW for 80 bunch operation. The peak power in a single pulse of a few picosecond duration is on the order of one watt. By reducing the momentum compaction, the bunch length could be reduced to {sigma}{sub L0} = 0.15 mm, resulting in coherent synchrotron radiation down to 500 {micro}m.
Date: January 1, 1998
Creator: Murphy, J.B.; Blum, E.; Heese, R.; Keane, J. & Krinsky, S.
Partner: UNT Libraries Government Documents Department

Free-Electron Lasers: Vacuum electronic generators of coherent radiation

Description: Vacuum electronic sources have shown marked improvement since the invention of the magnetron before World War II, and dramatic increases in both average powers and frequencies have been achieved. Of course, much of these gains have been achieved by the development of different devices. The typical development pattern for a given device exhibits an initial period of rapid improvement followed by a plateau determined by technological or physical limitations on the concept. Slow wave devices such as magnetrons and/or klystrons operate efficiently at frequencies up through X-band or the source of the relationed cavity traveling wave tubes are used for various applications at frequencies ranging up through W-band. At still higher frequencies fast wave devices such as gyrotrons and free-electron lasers are required are required for high power operation. The free-electron laser concept is unique in that the mechanism is applicable across the entire electromagnetic spectrum, and free-electron lasers have been built at wavelengths from microwaves through the ultraviolet, and plans are under development for X-ray systems. The purpose of this paper is to describe the principal directions of free-electron laser research at the present time. To this end, they first give a brief tutorial of the physics underlying the concept, and then describe the principal development paths under way.
Date: May 1, 1995
Creator: Neil, G. & Freund, H.
Partner: UNT Libraries Government Documents Department

Calculation of coherent emissions and gain from a prebunched Free Electron Laser

Description: This report advances a theoretical model for the single pass growth of coherent radiation in a prebunched FEL system. The FEL system includes a radio frequency linear accelerator (fr linac) as the injector, a resonator cavity with a wiggler magnet, and two highly reflective plano-concave mirrors, typically 99{percent} of the radiation is reflected inside the resonator. The model is based upon the following assumptions: a) the electron beam is cold, b) a super- electron is a particle with {approximately} 10{sup 8} elementary charges inside a bunch; the bunch length is much smaller than the radiation wavelength and the super-electron scatters with the rf wave in a single pass through the resonator, c) a smooth phase space transition must exist between the rf linac and the resonator, d) the energy gain is low per pass and consequently in the linear gain regime, and e) if condition (b) is satisfied and the bunch is resonant with the FEL beat wave, all electrons lose energy to the wave, in the lowest order approximation. A simple scaling technique is used to calculate the output power given the number of particles in a bunch and the efficiency for retrieving coherent radiation from the resonator. 4 refs., 8 figs., 2 tabs.
Date: August 1, 1995
Creator: Treadwell, E.A.
Partner: UNT Libraries Government Documents Department

Coherent sychrotron radiation detector for a non-invasive subpicosecond bunch length monitor

Description: This CSR detector was developed to monitor nondestructively the length of a subpicosecond bunch with high sensitivity. The monitor uses a state of the art GaAs Schottky whisker diode which is operated at room temperature at a wavelength of a few hundred microns. The detector is capable of detecting radiation power as low as 10 nW, depending on wavelength. This paper describes design specifications, parameter ranges, and monitor features and also reports its performance and comparison between measurement and calculation. The measurement results are cross-compared with an independent bunch length measurement using phase modulation. It was found that the output power varies with bunch length and that detectors at shorter wavelengths are preferred.
Date: December 31, 1995
Creator: Krafft, G.A.; Wang, D.; Price, E.; Feldl, E.; Porterfield, D.; Wood, P. et al.
Partner: UNT Libraries Government Documents Department

Coherent Harmonics in the Super-radiant Regime from an FEL

Description: Early work that quantified the ratio of coherent harmonic power to the fundamental power as a function of cavity length found that the ratio peaked for a large cavity length detuning. This is consistent with an overbunching model of coherent harmonic production. Recent measurements on the IR Demo FEL at Jefferson Lab have shown that the ratio is also high very near the synchronous point. In this regime the laser is operating a super-radiant mode, similar to what might be present in a SASE device. The recent data is compared to predictions of harmonic production in both long pulse oscillators and SASE FELs.
Date: June 1, 2001
Creator: Benson, Stephen V.; Gubeli, Joe & Shinn, Michelle D.
Partner: UNT Libraries Government Documents Department

Experimental Studies on Coherent Synchrotron Radiation at an Emittance Exchange Beamline

Description: One of the goals of the Fermilab A0 photoinjector is to experimentally investigate the transverse to longitudinal emittance exchange (EEX) principle. Coherent synchrotron radiation in the emittance exchange line could limit the performance of the emittance exchanger at short bunch lengths. In this paper, we present experimental and simulation studies of the coherent synchrotron radiation (CSR) in the emittance exchange line at the A0 photoinjector. We report on time-resolved CSR studies using a skew-quadrupole technique. We also demonstrate the advantages of running the EEX with an energy chirped beam.
Date: April 1, 2012
Creator: Thangaraj, J.C.T.; Thurman-Keup, R.; Ruan, J.; Johnson, A.S.; Lumpkin, A.H.; Santucci, J. et al.
Partner: UNT Libraries Government Documents Department

An Autocorrelation Technique for Measuring Sub-Picosecond Bunch Length Using Coherent Transition Radiation

Description: A new technique for determining sub-picosecond bunch length using infrared transition radiation and interferometry is proposed. The technique makes use of an infrared Michelson interferometer for measuring the autocorrelation of transition radiation emitted from a thin conducting foil placed in the beam path. The theory of coherent radiation from a charged particle beam passing through a thin conducting foil is presented. Subsequently, the analysis of this radiation through Michelson interferometry is shown to provide the autocorrelation of the longitudinal bunch profile. An example relevant to the CEBAF front end test is discussed.
Date: April 1, 1991
Creator: Barry, Walter
Partner: UNT Libraries Government Documents Department