First Name: R
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Last Name: Tatchyn
Full Name: R. Tatchyn
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10 papers
| title: | Research and development toward a 4.5-1.5 angstrom linac coherent light source (LCLS) at SLAC |
| format: | conference procceeding |
| conference: | 17th International Free Electron Laser Conference |
| year: | 1996 |
| 32 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | In recent years significant studies have been initiated on the feasibility of utilizing a portion of the 3 km S-band accelerator at SLAC to drive a short wavelength (4.5-1.5 Angstrom) Linac Coherent Light Source (LCLS), a Free-Electron Laser (FEL) operating in the Self-Amplified Spontaneous Emission (SASE) regime. Electron beam requirements for single-pass saturation in a minimal time include: 1) a peak current in the 7 kA range, 2) a relative energy spread of <0.05%, add 3) a transverse emittance, epsilon [rad-m], approximating the diffraction-limit condition epsilon=lambda/4 pi, where lambda[m] is the output wavelength. Requirements on the insertion device include field error levels of 0.02% for keeping the electron bunch centered on and in phase with the amplified photons, and a focusing beta of 8 m/rad for inhibiting the dilution of its transverse density. Although much progress has been made in developing individual components and beam-processing techniques necessary for LCLS operation down to similar to 20 Angstrom, a substantial amount of research and development is still required in a number of theoretical and experimental areas leading to the construction and operation of a 4.5-1.5 Angstrom LCLS. In this paper we report on a research and development program underway and in planning at SLAC for addressing critical questions in these areas. These include the construction and operation of a linac test stand for developing laser-driven photocathode rf guns with normalized emittances approaching 1 mm-mrad; development of advanced beam compression, stability, and emittance control techniques at multi-GeV energies; the construction and operation of a FEL Amplifier Test Experiment (FATE) for theoretical and experimental studies of SASE at IR wavelengths; an undulator development program to investigate superconducting, hybrid/permanent magnet (hybrid/PM), and pulsed-Cu technologies; theoretical and computational studies of high-gain FEL physics and LCLS component designs; development of X-ray optics and instrumentation for extracting, modulating, and delivering photons to experimental users; and the study and development of scientific experiments made possible by the source properties of the LCLS. |
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| title: | Short wavelength FELs using the SLAC linac |
| format: | journal article |
| year: | 1994 |
| 30 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | We have studied the use of the SLAC linac to drive FELs at wavelengths down to a few angstroms. Lasing would be achieved in a single pass of a low emittance, high peak current, high energy eelctron beam through a long undulator by Self-Amplified-Spontaneous-Emissin (SASE). About 10(13) photons per pulse can be produced in 100 fs pulses at a 120 Hz rate, corresponding to brightness levels of about 10(22) average and 10(32) peak. Peak power levels are tens of GW. Electron energies of 10-20 GeV are required. Signifcant imporvement of FEL performance seems possible using harmonic generation techniques according to results from numerical simulations. |
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| title: | Prospects for high power linac coherent light source (LCLS) development in the 1000 angstrom-1 angstrom wavelength range |
| format: | conference procceeding |
| conference: | 4th International Colloquium on X-Ray Lasers |
| year: | 1994 |
| 26 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | Electron bunch requirements for single-pass saturation of a free-electron laser (FEL) operating at full transverse coherence in the self-amplified spontaneous emission (SASE) mode include: 1) a high peak current, 2) a sufficiently low relative energy spread, and 3) a transverse emittance epsilon (r-m) satisfying the condition epsilon <= lambda /4 pi , where lambda (m) is the output wavelength of the FEL. In the insertion device that induces the coherent amplification, the prepared electron bunch must be kept on a trajectory sufficiently collinear with the amplified photons without significant dilution of its transverse density. In this paper we discuss a Linac coherent light source (LCLS) based on a high energy accelerator such as, e.g., the 3 km S-band structure at the Stanford Linear Accelerator Center (SLAC), followed by a long high-precision undulator with superimposed quadrupole (FODO) focusing, to fulfill the given requirements for SASE operation in the 1000 angstrom-1 angstrom range. The electron source for the linac, an RF gun with a laser-excited photocathode featuring a normalized emittance in the 1-3 mm-mrad range, a longitudinal bunch duration of the order of 3 ps, and approximately 10(-9) C/bunch, is a primary determinant of the required low transverse and longitudinal emittances. Acceleration of the injected bunch to energies in the 5-25 GeV range is used to reduce the relative longitudinal energy spread in the bunch, as well as to reduce the transverse emittance to values consistent with the cited wavelength regime. Two longitudinal compression stages are employed to increase the peak bunch current to the 2-5 kA levels required for sufficiently rapid saturation. The output radiation is delivered, via a grazing-incidence mirror bank, to optical instrumentation and a multi-user beam line system. Technological requirements for LCLS operation at 40 angstroms, 4.5 angstroms, and 1.5 angstroms are examined. |
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| title: | The SLAC soft X-ray high power FEL |
| format: | conference procceeding |
| conference: | 15th International Free Electron Laser Conference |
| year: | 1994 |
| 23 authors: | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | We discuss the design and performance of a 2 to 4 nm FEL operating in self-amplified spontaneous emission (SASE), using a photoinjector to produce the electron beam, and the SLAC linac to accelerate it to an energy of about 7 GeV. Longitudinal bunch compression is used to increase the peak current to 2.5 kA, while reducing the bunch length to about 40 mu m. The FEL field gain length is about 6 m, and the saturation length is about 60 m. The saturated output power is about 10 GW, corresponding to about 10/sup 14/ photons in a single pulse in a bandwidth of about 0.1%, with a pulse duration of 0.16 ps. Length compression, emittance control, phase stability, FEL design criteria, and parameter tolerances are discussed. (15 References). |
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| title: | Design considerations for a 60 meter pure permanent magnet undulator for the SLAC Linac Coherent Light Source (LCLS) |
| format: | conference procceeding |
| conference: | 1993 Particle Accelerator Conference |
| year: | 1993 |
| 7 authors: | | | | | | | |
| abstract: | In this paper we describe design, fabrication, and measurement aspects of a pure permanent magnet (PM) insertion device designed to operate as an FEL at a 1st harmonic energy of 300 eV and an electron energy of 7 GeV in the self-amplified spontaneous emission regime. (13 References). |
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| title: | A 2-4 nm Linac Coherent Light Source (LCLS) using the SLAC linac |
| format: | conference procceeding |
| conference: | 1993 Particle Accelerator Conference |
| year: | 1993 |
| 20 authors: | | | | | | | | | | | | | | | | | | | | |
| abstract: | We describe the use of the SLAC linac to drive a unique, powerful, short wavelength Linac Coherent Light Source (LCLS). Operating as an FEL, lasing would be achieved in a single pass of a high peak current electron beam through a long undulator by self-amplified spontaneous emission. The main components are a high-brightness rf photocathode electron gun; pulse compressors; about 1/5 of the SLAC linac; and a long undulator with a FODO quadrupole focusing system. Using electrons below 8 GeV, the system would operate at wavelengths down to about 3 nm, producing [right angle bracket]or=10 GW of peak power in sub-ps pulses. At a 120 Hz rate the average power is approximately=1 W. (6 References). |
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| title: | A 2 to 4 nm high power FEL on the SLAC linac |
| format: | conference procceeding |
| conference: | 14th International Free Electron Laser Conference |
| year: | 1993 |
| 13 authors: | | | | | | | | | | | | | |
| abstract: | The authors report the results of preliminary studies of a 2 to 4 nm SASE FEL, using a photoinjector to produce the electron beam, and the SLAC linac to accelerate it to an energy up to 10 GeV. Longitudinal bunch compression is used to increase ten fold the peak current to 2.5 kA, while reducing the bunch length to the subpicosecond range. The saturated output power is in the multi-gigawatt range, producing about 10/sup 14/ coherent photons within a bandwidth of about 0.2% r.m.s., in a pulse of several millijoules. At 120 Hz repetition rate the average power is about 1 W. The system is optimized for X-ray microscopy in the water window around 2 to 4 nm, and will permit imaging a biological sample in a single subpicosecond pulse. (21 References). |
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| title: | 40 Angstrom FEL designs for the PEP storage ring |
| format: | conference procceeding |
| conference: | 13th International Free Electron Laser Conference |
| year: | 1992 |
| 6 authors: | | | | | | |
| abstract: | Explores the use of the 2.2 km PEP storage ring at SLAC to drive a 40 angstrom free-electron laser in the self-amplified spontaneous emission configuration. Various combinations of electron-beam and undulator parameters, as well as special undulator designs, are discussed. Saturation and high peak, in-band, coherent power (460 MW) are possible with a 67 m, hybrid permanent-magnet undulator in a ring bypass. A 100 m, cusp-field undulator can achieve high average, in-band, coherent power (0.25 W) in the main ring. The existing, 25.6 m Paladin undulator at LLNL, with the addition of optical-klystron dispersive sections, is considered for both peak and average power. (35 References). |
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| title: | Short wavelength FELs on large storage rings |
| format: | conference procceeding |
| conference: | 7th National Conference on Synchrotron Radiation Instrumentation |
| year: | 1992 |
| 6 authors: | | | | | | |
| abstract: | The use of a large-circumference, high-energy, electron-positron collider such as PEP, TRISTAN or PETRA to drive a free-electron laser (FEL), producing high levels of coherent power at short wavelengths around 40 AA is explored. The authors consider self-amplified spontaneous emission (SASE), in which electron bunches with low emittance, high peak current and small energy spread radiate coherently in a single pass through a long undulator. As the electron beam passes down the undulator, its interaction with the increasingly intense spontaneous radiation causes a bunch density modulation at the optical wavelength, resulting in stimulated emission and exponential growth of coherent power in a single pass. The need for optical-cavity mirrors, which place a lower limit on the wavelength of a conventional FEL oscillator, is avoided. Various combinations of electron-beam and undulator parameters, as well as special undulator designs, are discussed. Saturation and high peak, in-band, coherent power (460 MW) are possible with a 67 m, hybrid permanent-magnet undulator in a ring bypass. A 100 m, cusp-field undulator can achieve high average, in-band, coherent power (0.25 W) in the main ring. The existing, 25.6 m Paladin undulator at LLNL, with the addition of optical-klystron dispersive sections, is considered for both peak and average power. |
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| title: | Coherent X-rays from PEP |
| format: | conference procceeding |
| conference: | 1991 Particle Accelerator Conference |
| year: | 1991 |
| 7 authors: | | | | | | | |
| abstract: | The authors explore the use of a large-circumference, high-energy electron-positron collider such as PEP to drive a free-electron laser (FEL), producing high levels of coherent power at short wavelengths. They consider self-amplified spontaneous emission (SASE), in which electron bunches with low emittance, high peak current, and small energy spread radiate coherently in a single pass through a long undulator. The authors also explore various combinations of electron-beam and undulator parameters, as well as special undulator designs and optical klystrons (OKs), to reach high average or peak coherent power at wavelength around 40 AA by achieving significant exponential gain or full saturation. Examples are presented for devices that achieve high peak coherent power (up to about 400 MW) with lower average coherent power (about 20 mW) and other devices which produce a few watts of average coherent power. (22 References). |
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