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Lcls Injector Drive Laser
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Download or read book LCLS Injector Drive Laser written by and published by . This book was released on 2007 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: Requirements for the LCLS injector drive laser present significant challenges to the design of the system. While progress has been demonstrated in spatial shape, temporal shape, UV generation and rep-rate, a laser that meets all of the LCLS specifications simultaneously has yet to be demonstrated. These challenges are compounded by the stability and reliability requirements. The drive laser and transport system has been installed and tested. We will report on the current operational state of the laser and plans for future improvements.
Book Synopsis What Have We Learned from the LCLS Injector? by :
Download or read book What Have We Learned from the LCLS Injector? written by and published by . This book was released on 2012 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The LCLS injector reliably delivered a high quality electron beam since it started operations three years ago. Some initial commissioning results were described in Ref. [1]. This note is to summarize what we have understood from the LCLS injector including drive laser, cathode, RF gun, injector beam line elements, beam modeling and operations. What we have learned during the LCLS injector commissioning and operation has lead to modified specifications for the UV drive laser system. A flat temporal profile originally required in the LCLS design is not necessary to achieve a low emittance electron beam for the LCLS operations. According to our recent studies, a laser pulse with 3 ps Gaussian temporal profile (FWHM) can achieve a similar emittance compared to a flat temporal profile laser. The sensitivity of the emittance to the laser pulse length at 250 pC of bunch charge was studied, as shown in Figure 1. Only slight variations were observed for both projected and time-sliced emittances with laser pulses from 2.2 ps to 4.5 ps FWHM. Space charge forces certainly become weak but RF emittance which is proportional to the bunch length square increases due to the longer laser pulse. Thus, the projected emittance optimum may be a trade-off between space charge forces and RF emittance, while the time-sliced emittance determined by space charge forces may be slightly improved with a longer laser pulse length. Simulations and theory also show that spatial Gaussian-cut laser profile produces a better emittance compared to uniform profiles due to increased linearity of the space charge forces. Preliminary experimental data show that the emittance with a Gaussian-cut is almost as good as the one with uniform although not better than. In addition, the laser transmission through the iris for spatial Gaussian-cut is about twice the one for spatial uniform. More experimental studies with the new Coherent laser system are needed to make a more solid conclusion.
Book Synopsis Commissioning the LCLS Injector by :
Download or read book Commissioning the LCLS Injector written by and published by . This book was released on 2007 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project presently under construction at SLAC. The injector section, from drive laser and RF photocathode gun through first bunch compressor chicane, was installed in fall 2006. Initial system commissioning with an electron beam was completed in August 2007, with the goal of a 1.2-micron emittance in a 1-nC bunch clearly demonstrated. The second phase of commissioning, including second bunch compressor and full linac, is planned for 2008, with FEL commissioning in 2009. We report experimental results and experience gained in the first phase of commissioning, including the photo-cathode drive laser, RF gun, photocathode, S-band and X-band RF systems, first bunch compressor, and the various beam diagnostics.
Book Synopsis Commissioning Results of the LCLS Injector by :
Download or read book Commissioning Results of the LCLS Injector written by and published by . This book was released on 2007 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Linac Coherent Light Source (LCLS) is a SASE xray Free-Electron Laser (FEL) project presently under construction at SLAC. The injector section, from drive-laser and RF photocathode gun through first bunch compressor chicane, was installed in fall 2006. Initial system commissioning with an electron beam has recently been completed. The second phase of construction, including second bunch compressor and full linac, is planned for 2008. In this paper, we report experimental results and experience gained during the first phase of machine commissioning. This includes the cathode, drive laser, RF photocathode gun, linac booster section, S-band and X-band RF systems, first bunch compressor, and the various beam diagnostics.
Book Synopsis Initial Commissioning Experience With the LCLS Injector by :
Download or read book Initial Commissioning Experience With the LCLS Injector written by and published by . This book was released on 2007 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Linac Coherent Light Source (LCLS) is a SASE xray Free-Electron Laser (FEL) project presently under construction at SLAC [1]. The injector section, from drive-laser and RF photocathode gun through first bunch compressor chicane, was installed in fall 2006. Initial system commissioning with an electron beam is taking place during the spring and summer of 2007. The second phase of construction, including second bunch compressor and full linac, will begin later, in the fall of 2007. We report here on experience gained during the first phase of machine commissioning, including RF photocathode gun, linac booster section, S-band and X-band RF systems, first bunch compressor, and the various beam diagnostics.
Book Synopsis UV Laser Pulse Temporal Profile Requirements for the LCLS Injector - Part I - Fourier Transform Limit for a Temporal Zero Slope Flattop by :
Download or read book UV Laser Pulse Temporal Profile Requirements for the LCLS Injector - Part I - Fourier Transform Limit for a Temporal Zero Slope Flattop written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The temporal profile of the uv drive laser pulse for the LCLS injector is specified by the duration, the rise/fall time, and the maximum rms amplitude (for all frequencies) of residual modulation in the plateau region. The bandwidth of the uv laser system should accommodate pulses with a rise/fall time as low as 0.7 ps and an rms residual amplitude modulation (on the plateau) below 0.5% in the absence of a laser heater. Computations including the laser heater [3] relax this requirement to the 5% level. Numerical analyses of Fourier transform limited uv pulses show that the extent of frequency sidebands should extend to at least 1.5 THz on either side of the central uv frequency. For simplicity, we assume that the emitted electron beam profile matches the laser profile. The evolution of those electron beam distributions in the longitudinal phase space along the beamline as calculated with PARMELA/ASTRA are shown. Related spectral and shaping requirements on the fundamental ir pulses are briefly addressed.
Book Synopsis Location of Maximum Credible Beam Losses in LCLS Injector by :
Download or read book Location of Maximum Credible Beam Losses in LCLS Injector written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The memo describes the maximum credible beam the LCLS injector can produce and lose at various locations along the beamline. The estimation procedure is based upon three previous reports [1, 2, 3]. While specific numbers have been updated to accurately reflect the present design parameters, the conclusions are very similar to those given in Ref 1. The source of the maximum credible beam results from the explosive electron emission from the photocathode if the drive laser intensity exceeds the threshold for plasma production. In this event, the gun's RF field can extract a large number of electrons from this plasma which are accelerated out of the gun and into the beamline. This electron emission persists until it has depleted the gun of all its energy. Hence the number of electrons emitted per pulse is limited by the amount of stored RF energy in the gun. It needs to be emphasized that this type of emission is highly undesirable, as it causes permanent damage to the cathode.
Book Synopsis First Results of the LCLS Laser-Heater System by :
Download or read book First Results of the LCLS Laser-Heater System written by and published by . This book was released on 2011 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Linac Coherent Light Source (LCLS) is an x-ray Free-Electron Laser (FEL) project that has just achieved its first lasing at 1.5 Å radiation wavelength. The very bright electron beam required to drive this FEL is susceptible to a microbunching instability in the magnetic bunch compressors that may increase the slice energy spread beyond the FEL tolerance. To control the slice energy spread and to suppress the microbunching instability, a laser heater (LH) system is installed in the LCLS injector area at 135 MeV, right before the RF deflector that is used for the time-resolved electron diagnostics. This unique component is used to add a small level of intrinsic energy spread to the electron beam in order to Landau damp the microbunching instability before it potentially breaks up the high brightness electron beam. The system was fully installed and tested in the fall of 2008, and effects of heating on the electron beam and the x-ray FEL were studied during the 2009 commissioning period. The laser heater system is composed of a 4-dipole chicane; a 9-period, planar, permanent-magnet, adjustable-gap undulator at the center of the chicane; one OTR screen on each side of the undulator for electron/laser spatial alignment; and an IR laser (up to 15-MW power) which co-propagates with the electron beam inside the undulator generating a 758-nm energy modulation along the bunch. The final two dipoles of the 4-dipole chicane time-smear this modulation leaving only a thermal-like intrinsic energy spread within the bunch. Table 1 lists the main parameters for this system. The very bright electron beam required for an x-ray free-electron laser (FEL), such as the LCLS, is susceptible to a microbunching instability in the magnetic bunch compressors, prior to the FEL undulator. The uncorrelated electron energy spread in the LCLS can be increased by an order of magnitude to provide strong Landau damping against the instability without degrading the FEL performance. To this end, a 'laser-heater' system has been installed in the LCLS injector, which modulates the energy of a 135-MeV electron bunch with an IR laser beam in a short undulator, enclosed within a four-dipole chicane. The last half of the chicane time-smears the energy modulation leaving an effective thermal energy spread increase. We present the first commissioning results of this system, its operational issues, its impact on the microbunching instability, and finally its effect on the FEL performance.
Book Synopsis Emittance Measurements from a Laser Driven Electron Injector by :
Download or read book Emittance Measurements from a Laser Driven Electron Injector written by and published by . This book was released on 2003 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Gun Test Facility (GTF) at the Stanford Linear Accelerator Center was constructed to develop an appropriate electron beam suitable for driving a short wavelength free electron laser (FEL) such as the proposed Linac Coherent Light Source (LCLS). For operation at a wavelength of 1.5 Å, the LCLS requires an electron injector that can produce an electron beam with approximately 1 [pi] mm-mrad normalized rms emittance with at least 1 nC of charge in a 10 ps or shorter bunch. The GTF consists of a photocathode rf gun, emittance-compensation solenoid, 3 m linear accelerator (linac), drive laser, and diagnostics to measure the beam. The rf gun is a symmetrized 1.6 cell, s-band high gradient, room temperature, photocathode structure. Simulations show that this gun when driven by a temporally and spatially shaped drive laser, appropriately focused with the solenoid, and further accelerated in linac can produce a beam that meets the LCLS requirements. This thesis describes the initial characterization of the laser and electron beam at the GTF. A convolved measurement of the relative timing between the laser and the rf phase in the gun shows that the jitter is less than 2.5 ps rms. Emittance measurements of the electron beam at 35 MeV are reported as a function of the (Gaussian) pulse length and transverse profile of the laser as well as the charge of the electron beam at constant phase and gradient in both the gun and linac. At 1 nC the emittance was found to be ≈ 13 [pi] mm-mrad for 5 ps and 8 ps long laser pulses. At 0.5 nC the measured emittance decreased approximately 20% in the 5 ps case and 40% in the 8 ps case. These measurements are between 40-80% higher than simulations for similar experimental conditions. In addition, the thermal emittance of the electron beam was measured to be 0.5 [pi] mm-mrad.
Book Synopsis Penetration of the LCLS Injector Shield Wall at Sector 20 by :
Download or read book Penetration of the LCLS Injector Shield Wall at Sector 20 written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Penetrations through the LCLS injector shield wall are needed for the alignment of the accelerator, a diagnostic laser beam and utilities, and are shown in figure 1. The 1-inch diameter LCLS injector beam tube is blocked by the PPS stopper when the injector side of the wall is occupied. The two 3-inch diameter penetrations above and to the left of the beam tube are used by Precision Alignment and will be open only during installation of the injector beamline. Additional 3-inch diameter penetrations are for laser beams which will be used for electron beam diagnostics. These will not be plugged when the injector occupied. Other penetrations for the RF waveguide and other utilities are approximately 13-inch from the floor and as such are far from the line-of-sight of any radiation sources. The waveguide and utility penetrations pass only through the thicker wall as shown in the figure. The principal issue is with the two laser penetrations, since these will be open when the linac is operating and people are in the LCLS injector area. A principal concern is radiation streaming through the penetrations due to direct line-of sight of the PEP-2 lines. To answer this, fans of rays were traced through the 3-inch diameter laser penetrations as shown in Figures 2 and 3. Figure 2 gives the top view of the shield walls, the main linac and PEP-2 lines, and the ray-fans. The fans appear to originate between the walls since their angular envelope is defined by the greatest angle possible when rays are just on the 3-inch diameter at the inner most and outermost wall surfaces. The crossovers of all possible rays lie half way between these two surfaces. As the end-on view of Figure 3 clearly shows, there is no direct line-of-sight through the laser penetrations of the PEP-2 or linac beamlines.
Book Synopsis Inverse Free Electron Laser Heater for the LCLS. by : P. Bolton
Download or read book Inverse Free Electron Laser Heater for the LCLS. written by P. Bolton and published by . This book was released on 2005 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Linac Coherent Light Source (LCLS) free electron laser employs an RF photocathode gun that yields a 1nC bunch a few picoseconds long, which must be further compressed to yield the high current required for Self Amplified Spontaneous Emission (SASE) gain. The electron beam from the RF photocathode gun is quite sensitive to microbunching instabilities such as coherent synchrotron radiation (CSR) in the compressor chicanes and longitudinal space charge (LSC) in the linac. These effects can be Landau damped by adding energy spread to the electron bunch prior to compression. They propose to do this by co-propagating an infrared laser beam with the electron bunch in an undulator in the LCLS injector beamline. The undulator is placed in a four bend magnet chicane to allow the Ir laser beam to propagate colinearly with the e-beam while it oscillates in the undulator. The IR laser beam is derived from the photocathode gun drive laser, so the two beams are synchronized. Simulations presented elsewhere in these proceedings show that the laser interaction damps the microbunching instabilities to a very great extent. This paper is a description of the design of the laser heater.
Book Synopsis Simulations of Ion Migration in the LCLS RF Gun and Injector by :
Download or read book Simulations of Ion Migration in the LCLS RF Gun and Injector written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The motivation for this work was the observed surface contamination of the first LCLS RF gun copper cathode. We will present the results of simulations in regards to ion migration in the LCLS gun. Ions of residual gases will be created by interaction of molecular gas species with the UV drive laser beam and by the electron beam itself. The larger part of those ionized molecules remain in the vicinity of creation, are transported towards beam line walls or away from the cathode. However a small fraction gains enough kinetic energy, focused by RF and magnetic fields and propagates to the cathode, producing an undesirable increase of the cathode's surface work function. Although this fraction is small, during long term operation, this effect may become a significant factor limiting the source performance.
Book Synopsis Commissioning of the LCLS Linac and Bunch Compressors by :
Download or read book Commissioning of the LCLS Linac and Bunch Compressors written by and published by . This book was released on 2008 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project under construction at SLAC [1]. The injector section, from drive-laser and RF photocathode gun through the first bunch compressor, was commissioned in the spring and summer of 2007. The second phase of commissioning, including the second bunch compressor and various main linac modifications, was completed in January through August of 2008. We report here on experience gained during this second phase of machine commissioning, including the injector, the first and second bunch compressor stages, the linac up to 14 GeV, and beam stability measurements. The final commissioning phase, including the undulator and the long transport line from the linac, is set to begin in December 2008, with first light expected in July 2009.
Book Synopsis Laser Shaping and Streaking for X-ray Free-electron Lasers by : Siqi Li (Physics student)
Download or read book Laser Shaping and Streaking for X-ray Free-electron Lasers written by Siqi Li (Physics student) and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Lasers have been a versatile tool in facilitating x-ray free-electron lasers in various components of the machine. At the beginning of photocathode injectors, the properties of the drive laser determine the initial distribution of the electrons. Laser heater has been widely used to modulate electron bunch energy spread in order to suppress collective instabilities arising from dispersive sections in the accelerator. Interaction between optical lasers and the electron beam can be used to manipulate the phase space of the electron bunch to produce desirable shapes in the x-ray emission. After the x-ray photons have been generated, optical lasers are used in synchronization with the x-ray pulse to study dynamics in atomic and molecular systems. Moreover, they can provide single-shot diagnosis of the x-ray pulse, such as laser streaking, to extract valuable information about the x-ray pulse itself and the dynamic system under analysis, which can be challenging to probe directly. In this work we examine laser applications specifically in the Linac Coherent Light Source (LCLS). In the first half of the thesis, we focus on laser shaping techniques applied to the injector drive laser and the laser heater, in both spatial and temporal domains. We further discuss ghost imaging as an application of laser shaping in accelerators and its potential to be used in other x-ray and electron imaging experiments. In the second half, we switch gear to laser streaking as a measurement tool for attosecond x-ray pulses. We discuss in detail the generation of attosecond x-ray pulses at LCLS and present exciting results of the first single-shot characterization of such extremely short pulses using laser streaking.
Book Synopsis The Los Alamos FEL Photoinjector Drive Laser by :
Download or read book The Los Alamos FEL Photoinjector Drive Laser written by and published by . This book was released on 1991 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: The drive laser system of the photoelectric injector for the Los Alamos free -- electron laser (FEL) is described. the bright electron beams required for high performance FELs demand stringnt specifications on drive laser output levels, beam quality, and stability. The laser system generates 7--15 ps (FWHM) Gaussian pulses of 527 nm light at a repetition rate of 21.67 MHz. These micropulses'' are contained within a
Book Synopsis Global developments towards continuous-wave free-electron lasers by : Ye Chen
Download or read book Global developments towards continuous-wave free-electron lasers written by Ye Chen and published by Frontiers Media SA. This book was released on 2023-11-09 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Development of the Linac Coherent Light Source RF Gun by :
Download or read book The Development of the Linac Coherent Light Source RF Gun written by and published by . This book was released on 2008 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Linac Coherent Light Source (LCLS) is the first x-ray laser user facility based upon a free electron laser (FEL) requiring extraordinary beam quality to saturate at 1.5 angstroms within a 100 meter undulator.[1] This new type of light source is using the last kilometer of the three kilometer linac at SLAC to accelerate the beam to an energy as high as 13.6 GeV and required a new electron gun and injector to produce a very bright beam for acceleration. At the outset of the project it was recognized that existing RF guns had the potential to produce the desired beam but none had demonstrated it. Therefore a new RF gun or at least the modification of an existing gun was necessary. The parameters listed in Table 1 illustrate the unique characteristics of LCLS which drive the requirements for the electron gun as given in Table 2. The gun beam quality needs to accommodate emittance growth as the beam is travels through approximately one kilometer of linac and two bunch compressors before reaching the undulator. These beam requirements were demonstrated during the recent commissioning runs of the LCLS injector and linac [2] due to the successful design, fabrication, testing and operation of the LCLS gun. The goal of this paper is to relate the technical background of how the gun was able to achieve and in some cases exceed these requirements by understanding and correcting the deficiencies of the prototype s-band RF photocathode gun, the BNL/SLAC/UCLA Gun III. This paper begins with a brief history and technical description of Gun III and the Gun Test Facility (GTF) at SLAC, and studies of the gun's RF and emittance compensation solenoid. The work at the GTF identified the gun and solenoid deficiencies, and helped to define the specifications for the LCLS gun. Section 1.1.5 describes the modeling used to compute and correct the gun RF fields and Section 1.1.6 describes the use of these fields in the electron beam simulations. The magnetic design and measurements of the emittance compensation solenoid are discussed in Section 1.1.7. The novel feature of the LCLS solenoid is the embedded quadrupole correctors. The thermo-mechanical engineering of the LCLS gun is discussed in Section 1.1.8, and the cold and hot RF tests are described in Section 1.1.9. The results of this work are summarized and concluding remarks are given in Section 1.1.10.
