المؤلفون: Walter, Katie

المصدر: Science & Technology Review; Jan/Feb2013, p12-15, 4p

مصطلحات موضوعية: GRAPHITE, LIGHT sources, LINEAR accelerators

مصطلحات جغرافية: MENLO Park (Calif.), CALIFORNIA

People: RIEGE, Stefan Hau

مستخلص: The article focuses on the experiment in which graphite crystals melted, conducted at the Linac Coherent Light Source (LCLS) lead by Livermore physicist Stefan Hau Riege at SLAC National Accelerator Laboratory in Menlo Park, California. It states that the LCLS experiment uses SLAC's portion with 3.2-kilometer-long linear accelerator (linac) wherein beam of electrons were created that give x-ray laser light. Result shows that the solid graphite crystal became dense matter in 40 femtoseconds. INSET: At the Linac Coherent Light Source.

المصدر: Science & Technology Review; Jan2011, Issue 1, p5-11, 7p

مصطلحات موضوعية: ULTRASHORT laser pulses, LINEAR accelerators, X-ray lasers, X-ray optics

مصطلحات جغرافية: MENLO Park (Calif.), CALIFORNIA

مستخلص: The article focuses on the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory in Menlo Park, California. It states that LCLS uses linear accelerators to produce the brightest ultrashort x-ray pulses on earth. LCLS is designed to allow scientists to take stop-action pictures of molecules and atoms, and to shed light of the fundamental processes of chemistry, physics, and electronics.

المؤلفون: Marsh, R A, Albert, F, Anderson, S G, Gibson, D J, Wu, S S, Hartemann, F V, Barty, C J

المساهمون: United States. Department of Energy.

المصدر: Presented at: IPAC 2012, New Orleans, LA, United States, May 20 - May 25, 2012

مصطلحات موضوعية: Quantum Efficiency, Lawrence Livermore National Laboratory, Security, Cathodes, Manufacturing, Testing, 43 Particle Accelerators, Processing, Simulation, 42 Engineering, Klystrons, Electric Fields, Design, Verification, Implementation, Compton Effect, Accelerators, Commissioning, Transport, Linear Accelerators

الوصف: This presentation reported on the technology choices and progress manufacturing and testing the injector and accelerator of the 250 MeV ultra-compact Compton Scattering gamma-ray Source under development at LLNL for homeland security applications. This paper summarizes the status of various facets of current accelerator activities at LLNL. The major components for the X-band test station have been designed, fabricated, and await installation. The XL-4 klystron has been delivered, and will shortly be dressed and installed in the ScandiNova modulator. High power testing of the klystron into RF loads will follow, including adjustment of the modulator for the klystron load as necessary. Assembly of RF transport, test station supports, and accelerator components will follow. Commissioning will focus on processing the RF gun to full operating power, which corresponds to 200 MV/m peak electric field on the cathode surface. Single bunch benchmarking of the Mark 1 design will provide confidence that this first structure operates as designed, and will serve as a solid starting point for subsequent changes, such as a removable photocathode, and the use of various cathode materials for enhanced quantum efficiency. Charge scaling experiments will follow, partly to confirm predictions, as well as to identify important causes of emittance growth, and their scaling with charge. Multi-bunch operation will conclude testing of the Mark 1 RF gun, and allow verification of code predictions, direct measurement of bunch-to-bunch effects, and initial implementation compensation mechanisms. Modeling will continue and focus on supporting the commissioning and experimental program, as well as seeking to improve all facets of linac produced Compton gamma-rays.

وصف الملف: PDF-file: 7 pages; size: 1.5 Mbytes; Text

العلاقة: rep-no: LLNL-PROC-557854; grantno: W-7405-ENG-48; osti: 1044231; http://digital.library.unt.edu/ark:/67531/metadc839214Test/; ark: ark:/67531/metadc839214

الإتاحة: http://digital.library.unt.edu/ark:/67531/metadc839214Test/

المؤلفون: Hartemann, F. V., Albert, F., Anderson, S. G., Bayramian, A. J., Cross, R. R., Ebbers, C. A., Gibson, D. J., Houck, T. L., Marsh, R. A., Messerly, M. J., Siders, C. W., McNabb, D. P., Barty, C. J., Adolphsen, C. E., Chu, T. S., Jongewaard, E. N., Tantawi, S. G., Vlieks, A. E., Wang, F., Wang, J. W., Raubenheimer, T. O., Ighigeanu, D., Toma, M., Cutoiu, D.

المساهمون: United States. Department of Energy.

المصدر: Presented at: 2nd International Particle Accelerator Conference, San Sebastian, Spain, Sep 04 - Sep 09, 2011

مصطلحات موضوعية: Spectrometers, Light Sources, Energy Range, Radiations, Photocathodes, Brightness, Fluorescence, 43 Particle Accelerators, 42 Engineering, Optimization, Linear Accelerators, Electrons, Detection, Lasers, Accelerators, Acceleration, Photons, Fibers, Mev Range, Electron Beams, Illuminance, Compton Effect, Gamma Sources

الوصف: Nuclear photonics is an emerging field of research requiring new tools, including high spectral brightness, tunable gamma-ray sources; high photon energy, ultrahigh-resolution crystal spectrometers; and novel detectors. This presentation focuses on the precision linac technology required for Compton scattering gamma-ray light sources, and on the optimization of the laser and electron beam pulse format to achieve unprecedented spectral brightness. Within this context, high-gradient X-band technology will be shown to offer optimal performance in a compact package, when used in conjunction with the appropriate pulse format, and photocathode illumination and interaction laser technologies. The nascent field of nuclear photonics is enabled by the recent maturation of new technologies, including high-gradient X-band electron acceleration, robust fiber laser systems, and hyper-dispersion CPA. Recent work has been performed at LLNL to demonstrate isotope-specific detection of shielded materials via NRF using a tunable, quasi-monochromatic Compton scattering gamma-ray source operating between 0.2 MeV and 0.9 MeV photon energy. This technique is called Fluorescence Imaging in the Nuclear Domain with Energetic Radiation (or FINDER). This work has, among other things, demonstrated the detection of {sup 7}Li shielded by Pb, utilizing gamma rays generated by a linac-driven, laser-based Compton scattering gamma-ray source developed at LLNL. Within this context, a new facility is currently under construction at LLNL, with the goal of generating tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range, at a repetition rate of 120 Hz, and with a peak brightness in the 10{sup 20} photons/(s x mm{sup 2} x mrad{sup 2} x 0.1% bw).

وصف الملف: PDF-file: 5 pages; size: 0.8 Mbytes; Text

العلاقة: rep-no: LLNL-PROC-497653; grantno: W-7405-ENG-48; osti: 1026922; https://digital.library.unt.edu/ark:/67531/metadc836332Test/; ark: ark:/67531/metadc836332

الإتاحة: https://digital.library.unt.edu/ark:/67531/metadc836332Test/

المؤلفون: Hamm, R. W., Pearce-Percy, H., Pearson, D., Rougieri, M., Weir, J., Zografos, A., Guethlein, G., Hawkins, S., Falabella, S., Poole, B., Blackfield, D.

المساهمون: United States. Department of Energy.

المصدر: Presented at: AccApp '11 - Tenth International Topical Meeting on Nuclear Applications of Accelerators, Knoxville, TN, United States, Apr 03 - Apr 07, 2011

مصطلحات موضوعية: Acceleration, Protons, 43 Particle Accelerators, Dielectric Materials, Fast Neutrons, Targets, Linear Accelerators, Plates, Accelerators, Quadrupole Linacs, Synchrotrons

الوصف: A Radio Frequency Quadrupole (RFQ) linac system has been developed to provide a single pulse of 2 MeV protons with a beam pulse width of {approx}300 ps and a charge of 30 pC, either for injection into a pulsed Dielectric Wall Accelerator or for bombardment of a target to produce a fast neutron pulse. The 1.2 m long RFQ structure operates at 425 MHz and bunches and accelerates a single 2.35 ns beam pulse injected into it at 35 keV using a parallel plate deflector placed directly in front of the RFQ entrance. The input acceptance properties of the RFQ allow a simple dc bias voltage on the plates to block acceleration of the unwanted beam, with a short rf voltage pulse applied to null the deflection field for the ions within the 8 mm 'kicker' plate length. The use of the RFQ as the accelerating structure allows one to efficiently produce a large charge in a single sub-ns bunch. In addition, the kicker can also be used without the dc bias voltage to produce a 'notch' in the normal RFQ output beam for synchrotron injection.

وصف الملف: PDF-file: 9 pages; size: 0.8 Mbytes; Text

العلاقة: rep-no: LLNL-CONF-477421; grantno: W-7405-ENG-48; osti: 1022151; https://digital.library.unt.edu/ark:/67531/metadc845736Test/; ark: ark:/67531/metadc845736

الإتاحة: https://digital.library.unt.edu/ark:/67531/metadc845736Test/

المؤلفون: Qin, H., Davidson, R. C., Chung, M., Barnard, J. J., Wang, T. F.

المساهمون: United States. Department of Energy.

المصدر: Presented at: Particle Accelerator Conference, New York, NY, United States, Mar 28 - Apr 01, 2011

مصطلحات موضوعية: Light Sources, 43 Particle Accelerators, 70 Plasma Physics And Fusion, Lasers, Heavy Ions, Electron Beams, Energy Density, Linear Accelerators, Accelerators, Focusing, Physics

الوصف: The effect of a weakly coupled periodic lattice in terms of achieving emittance exchange between the transverse and longitudinal directions is investigated using the generalized Courant-Snyder theory for coupled lattices. Recently, the concept and technique of transverse-longitudinal emittance coupling have been proposed for applications in the Linac Coherent Light Source and other free-electron lasers to reduce the transverse emittance of the electron beam. Such techniques can also be applied to the driver beams for the heavy ion fusion and beam-driven high energy density physics, where the transverse emittance budget is typically tighter than the longitudinal emittance. The proposed methods consist of one or several coupling components which completely swap the emittances of one of the transverse directions and the longitudinal direction at the exit of the coupling components. The complete emittance exchange is realized in one pass through the coupling components. In the present study, we investigate the effect of a weakly coupled periodic lattice in terms of achieving emittance exchange between the transverse and longitudinal directions. A weak coupling component is introduced at every focusing lattice, and we would like to determine if such a lattice can realize the function of emittance exchange.

وصف الملف: 5 p. (0.1 MB); Text

العلاقة: rep-no: LLNL-PROC-480557; grantno: W-7405-ENG-48; osti: 1022879; https://digital.library.unt.edu/ark:/67531/metadc837409Test/; ark: ark:/67531/metadc837409

الإتاحة: https://digital.library.unt.edu/ark:/67531/metadc837409Test/

المؤلفون: Nilsen, J, Rohringer, N

المساهمون: United States. Department of Energy.

المصدر: Presented at: SPIE 2011 Optics and Photonics, San Diego, CA, United States, Aug 21 - Aug 25, 2011

مصطلحات موضوعية: Stanford Linear Accelerator Center, Light Sources, 70 Plasma Physics And Fusion Technology, 43 Particle Accelerators, Ground States, X-Ray Lasers, 74 Atomic And Molecular Physics, Excited States, Free Electron Lasers, Lasers, Quenching, Optics, Physics, Linear Accelerators

الوصف: Nearly four decades ago H-like and He-like resonantly photo-pumped laser schemes were proposed for producing X-ray lasers. However, demonstrating these schemes in the laboratory has proved to be elusive because of the difficulty of finding a strong resonant pump line. With the advent of the X-ray free electron laser (X-FEL) at the SLAC Linac Coherent Light Source (LCLS) we now have a tunable X-ray laser source that can be used to replace the pump line in previously proposed laser schemes and allow researchers to study the physics and feasibility of resonantly photo-pumped laser schemes. In this paper we use the X-FEL at 1174 eV to photo-pump the singly excited 1s2p state of He-like Ne to the doubly excited 2p3p state and model gain on the 2p3p-2p2s transition at 175 eV and the 2p3p-1s3p transition at 1017 eV. One motivation for studying this scheme is to explore possible quenching of the gain due to strong non-linear coupling effects from the intense X-FEL beam We compare this scheme with photo-pumping the He-like Ne ground state to the 1s3p singly excited state followed by lasing on the 3p-2s and 3d-2p transitions at 158 and 151 eV. Experiments are being planned at LCLS to study these laser processes and coherent quantum effects.

وصف الملف: PDF-file: 10 pages; size: 0.7 Mbytes; Text

العلاقة: rep-no: LLNL-PROC-496573; grantno: W-7405-ENG-48; osti: 1026921; http://digital.library.unt.edu/ark:/67531/metadc840215Test/; ark: ark:/67531/metadc840215

الإتاحة: http://digital.library.unt.edu/ark:/67531/metadc840215Test/

المؤلفون: Kreitzer, B R, Houck, T L, Luchterhand, O C

المساهمون: United States. Department of Energy.

المصدر: Presented at: SUPPRESSING THERMAL ENERGY DRIFT IN THE LLNL FLASH X-RAY ACCELERATOR USING LINEAR DISK RESISTOR STACKS, Chicago, IL, United States, Jun 19 - Jun 23, 2011

مصطلحات موضوعية: Temperature Coefficient, Heating, Sodium, Resistors, Beam Transport, 43 Particle Accelerators, Linear Accelerators, Pulse Rise Time, Lawrence Livermore National Laboratory, Thiosulfates, 42 Engineering, Water, Design, Magnets, Configuration, Accelerators, Induction

الوصف: This paper addresses thermal drift in sodium thiosulfate liquid resistors and their replacement with linear disk resistors from HVR Advanced Power Components. Sodium thiosulfate resistors in the FXR induction linear accelerator application have a temperature coefficient of {approx}1.8%/C. The FXR Marx banks send an 8kJ pulse through eight 524 cm{sup 3} liquid resistors at a repetition rate of up to 1 every 45 seconds. Every pulse increases the temperature of the solution by {approx}0.4 C which produces a 0.7% change in resistance. The typical cooling rate is {approx}0.4 C per minute which results in {approx}0.1% energy drop per pulse during continuous pulsed operations. A radiographic accelerator is extraordinarily sensitive to energy variations. Changes in beam energy produce movement in beam transport, changes in spot size, and large dose variations. If self-heating were the only problem, we could predict the increase in input voltage required to compensate for the energy loss. However, there are other variables that influence the temperature of the resistors such as focus magnet heating, changes in room temperature, changes in cooling water, where the cell is located, etc. Additionally not all of the resistors have equivalent cooling rates and as many as 32 resistors are driven from a single power source. The FXR accelerator group elected to replace the sodium thiosulfate resistors with HVR Linear Disk Resistors in a stack type configuration. With data limited for these resistors when used in oil and at low resistance values, a full characterization needed to be performed. High currents (up to 15kA), high voltages (up to 400kV), and Fast Rise times (<10ns) made a resistor choice difficult. Other solid resistors have been tried and had problems at the connection points and with the fact that the resistivity changed as they absorbed oil. The selected HVR resistors have the advantage of being manufactured with the oil impregnated in to them so this characteristic is minimized while still offering the desired ...

وصف الملف: PDF-file: 7 pages; size: 0.8 Mbytes; Text

العلاقة: rep-no: LLNL-CONF-491238; grantno: W-7405-ENG-48; osti: 1022930; http://digital.library.unt.edu/ark:/67531/metadc837027Test/; ark: ark:/67531/metadc837027

الإتاحة: http://digital.library.unt.edu/ark:/67531/metadc837027Test/

المؤلفون: Hartemann, F. V., Albert, F., Anderson, G. G., Anderson, S. G., Bayramian, A. J., Betts, S. M., Chu, T. S., Cross, R. R., Ebbers, C. A., Fisher, S. E., Gibson, D. J., Ladran, A. S., Marsh, R. A., Messerly, M. J., O'Neill, K. L., Semenov, V. A., Shverdin, M. Y., Siders, C. W., McNabb, D. P., Barty, C. P., Vlieks, A. E., Jongewaard, E. N., Tantawi, S. G., Raubenheimer, T. O.

المساهمون: United States. Department of Energy.

المصدر: Presented at: IPAC 2010, Kyoto, Japan, May 23 - May 28, 2010

مصطلحات موضوعية: Amplification, Photons, Light Sources, Energy Range, Brightness, Electron Beams, Stanford Linear Accelerator Center, Lasers, Resonance Fluorescence, Wastes, 42 Engineering, Construction, Nuclear Fuels, Design, Stockpiles, Electrons, Compton Effect, Accelerators, Security, Physics, Linear Accelerators

الوصف: Recent progress in accelerator physics and laser technology have enabled the development of a new class of tunable gamma-ray light sources based on Compton scattering between a high-brightness, relativistic electron beam and a high intensity laser pulse produced via chirped-pulse amplification (CPA). A precision, tunable Mono-Energetic Gamma-ray (MEGa-ray) source driven by a compact, high-gradient X-band linac is currently under development and construction at LLNL. High-brightness, relativistic electron bunches produced by an X-band linac designed in collaboration with SLAC NAL will interact with a Joule-class, 10 ps, diode-pumped CPA laser pulse to generate tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range via Compton scattering. This MEGa-ray source will be used to excite nuclear resonance fluorescence in various isotopes. Applications include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. The source design, key parameters, and current status are presented, along with important applications, including nuclear resonance fluorescence. In conclusion, we have optimized the design of a high brightness Compton scattering gamma-ray source, specifically designed for NRF applications. Two different parameters sets have been considered: one where the number of photons scattered in a single shot reaches approximately 7.5 x 10{sup 8}, with a focal spot size around 8 {micro}m; in the second set, the spectral brightness is optimized by using a 20 {micro}m spot size, with 0.2% relative bandwidth.

وصف الملف: PDF-file: 5 pages; size: 1 Mbytes; Text

العلاقة: rep-no: LLNL-PROC-432680; grantno: W-7405-ENG-48; osti: 1018004; https://digital.library.unt.edu/ark:/67531/metadc843624Test/; ark: ark:/67531/metadc843624

الإتاحة: https://digital.library.unt.edu/ark:/67531/metadc843624Test/

المؤلفون: Shverdin, M. Y., Bayramian, A., Albert, F., Anderson, S. G., Betts, S. M., Chu, T. S., Cross, R. R., Gibson, D. J., Marsh, R., Messerly, M., Phan, H., Prantil, M., Wu, S., Ebbers, C., Scarpetti, R. D., Hartemann, F. V., Siders, C. W., McNabb, D. P., Bonanno, R. E., Barty, C. P.

المساهمون: United States. Department of Energy.

المصدر: Presented at: IPAC 2010, Kyoto, Japan, May 23 - May 28, 2010

مصطلحات موضوعية: Amplification, Lawrence Livermore National Laboratory, Fibers, Brightness, Electron Beams, Ytterbium, Electrons, Oscillators, Efficiency, 42 Engineering, Construction, Linear Accelerators, Amplifiers, Compton Effect, Lasers, Scattering, Accuracy, Photons

الوصف: Generation of mono-energetic, high brightness gamma-rays requires state of the art lasers to both produce a low emittance electron beam in the linac and high intensity, narrow linewidth laser photons for scattering with the relativistic electrons. Here, we overview the laser systems for the 3rd generation Monoenergetic Gamma-ray Source (MEGa-ray) currently under construction at Lawrence Livermore National Lab (LLNL). We also describe a method for increasing the efficiency of laser Compton scattering through laser pulse recirculation. The fiber-based photoinjector laser will produce 50 {micro}J temporally and spatially shaped UV pulses at 120 Hz to generate a low emittance electron beam in the X-band RF photoinjector. The interaction laser generates high intensity photons that focus into the interaction region and scatter off the accelerated electrons. This system utilizes chirped pulse amplification and commercial diode pumped solid state Nd:YAG amplifiers to produce 0.5 J, 10 ps, 120 Hz pulses at 1064 nm and up to 0.2 J after frequency doubling. A single passively mode-locked Ytterbium fiber oscillator seeds both laser systems and provides a timing synch with the linac.

وصف الملف: PDF-file: 5 pages; size: 1.5 Mbytes; Text

العلاقة: rep-no: LLNL-PROC-428250; grantno: W-7405-ENG-48; osti: 992277; https://digital.library.unt.edu/ark:/67531/metadc1012195Test/; ark: ark:/67531/metadc1012195

الإتاحة: https://digital.library.unt.edu/ark:/67531/metadc1012195Test/