In this paper we describe the technical design of an ongoing proof-of-principle echo-enabled harm... more In this paper we describe the technical design of an ongoing proof-of-principle echo-enabled harmonic generation (EEHG) experiment at the Next Linear Collider Test Accelerator (NLCTA) at SLAC. We present the design considerations and the technical details of the experiment.
The Linac Coherent Light Source (LCLS) has used three copper photocathodes since its commissionin... more The Linac Coherent Light Source (LCLS) has used three copper photocathodes since its commissioning in 2007. Two of three copper cathodes had low initial quantum efficiency (QE) (<1×10) in the LCLS radio frequency (RF) gun. The two cathodes were exposed to the plasma cleaning in the cathode test chamber before installation in the RF gun. Recent studies at the SLAC RF gun test bed at the Accelerator Structure Test Area (ASTA) reveals that the pre-cleaning in the test chamber followed by cathode exposure to air for installation in the gun is the major factor leading to the low initial QE. All four cathodes, without the plasma pre-cleaning prior to the installation in the gun, have demonstrated initial QE>4×10 at the ASTA. Systematic studies also demonstrate that high-power RF gun operation provides an initial QE boost. In-situ laser cleaning for three new cathodes in the RF gun is extensively investigated, and a robust laser cleaning procedure is established at the ASTA with impr...
Physical Review Special Topics - Accelerators and Beams
The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project presentl... more 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.
Surface characterization of the LCLS RF gun cathode A. Brachmann On behalf of the LCLS commission... more Surface characterization of the LCLS RF gun cathode A. Brachmann On behalf of the LCLS commissioning team The first copper cathode installed in the LCLS RF gun was used during LCLS commissioning for more than a year. However, after high charge operation (~ 500 pC), the cathode showed a decline of quantum efficiency due to surface contamination caused by residual ionized gas species present in the vacuum system. We report results of SEM, XPS and XAS studies that were carried out on this cathode after it was removed from the gun. X-ray absorption and X-ray photoelectron spectroscopy reveal surface contamination by various hydrocarbon compounds. In addition we report on the performance of the second installed cathode with emphasis on the spatial distribution of electron emission.
In addition to its normal operation at 250pC, the LCLS has operated with 20pC bunches delivering ... more In addition to its normal operation at 250pC, the LCLS has operated with 20pC bunches delivering X-ray beams to users with energies between 800eV and 2 keV and with bunch lengths below 10 fs FWHM. A bunch arrival time monitor and timing transmission system provide users with sub 100 fs synchronization between a laser and the X-rays for pump / probe experiments. We describe the performance and operational experience of the LCLS for short bunch experiments.
Ultrafast optical lasers play an essential role in exploiting the unique capabilities of recently... more Ultrafast optical lasers play an essential role in exploiting the unique capabilities of recently commissioned X-ray free-electron laser facilities such as the Linac Coherent Light Source (LCLS). Pump–probe experimental techniques reveal ultrafast dynamics in atomic and molecular processes and reveal new insights in chemistry, biology, material science and high-energy-density physics. This manuscript describes the laser systems and experimental methods that enable cutting-edge optical laser/X-ray pump–probe experiments to be performed at LCLS.
The Early Injector Commissioning program for LCLS-II aims to demonstrate CW electron beam product... more The Early Injector Commissioning program for LCLS-II aims to demonstrate CW electron beam production this year in the first two meters of the injector that includes the room-temperature 185.7 MHz single-cell gun and the 1.3 GHz two-cell buncher cavity. These cavities were designed and built by LBNL based on their experience with similar ones for their Advanced Photo-Injector Experiment (APEX) program. With the 258 nm laser system and Cs2Te cathodes, bunches of up to 300 pC are expected at rates as high as 1 MHz. The paper presents results from this program including the vacuum levels achieved, RF processing and field control experience, dark current measurements and laser and beam characterization.
The LCLS FEL began user operations in September 2009 with photon energies from 800eV to 2 KeV and... more The LCLS FEL began user operations in September 2009 with photon energies from 800eV to 2 KeV and pulse energies above 2 mJ. Both long pulse (50-200 femtosecond FWHM) and short pulse (<10 femtosecond FWHM at 150 uJ) pulses were delivered at user request. In addition the FEL was operated at fundamental photon energies up to 10 KeV in preparation for hard X-ray experiments. FEL operating parameters, performance and reliability results will be presented, in addition to plans for upgrades to the facility. LCLS LINAC The LCLS project modified the last 1 kilometer of the SLAC high energy physics LINAC to provide a 15 GeV driver for an X-ray FEL. An RF gun and laser heater system were installed in an off-axis tunnel to produce a 250pC, beam with a typical normalized emittance of 0.5um. Two bunch compressors were added at the 250MeV and 4.3 GeV points on the LINAC to provide peak currents typically between 1 and 3 KA. (Fig. 1) [1]
The Linac Coherent Light Source (LCLS) X-ray FEL utilizing the last km of the SLAC linac has been... more The Linac Coherent Light Source (LCLS) X-ray FEL utilizing the last km of the SLAC linac has been operational since April 2009 and finished its first successful user run last December. The various diagnostics for electron beam properties including beam position monitors, wire scanners, beam profile monitors, and bunch length diagnostics are presented as well as diagnostics for the X-ray beam. The low emittance and ultra-short electron beam required for X-ray FEL operation has implications on the transverse and longitudinal diagnostics. The coherence effects of the beam profile monitors and the challenges of measuring fs long bunches are discussed.
For the Linac Coherent Light Source II (LCLS-II) project at SLAC, a 1.3 GHz superconducting rf (S... more For the Linac Coherent Light Source II (LCLS-II) project at SLAC, a 1.3 GHz superconducting rf (SRF) linac is being constructed that will generate 4 GeV electron bunches at a high repetition rate to drive x-ray free electron lasers. The LCLS-II electron source, which comprises the first three meters of the electron injector, includes two normal-conducting, continuous-wave rf cavities: a one-cell, 185.7 MHz gun and a two-cell, 1.3 GHz buncher. It also includes a gun load-lock system that allows photocathodes to be changed under vacuum. The components in this beam-line section were designed and built by Lawrence Berkeley National Laboratory based on experience from their advanced photoinjector experiment program. In combination with the SLAC UV laser system, the electron source is designed to produce beam rates up to 1 MHz with average currents up to $30\text{ }\text{ }\ensuremath{\mu}\mathrm{A}$ initially. The source was installed in mid-2018, well in advance of the SRF linac, which ...
Three temporal diagnostic techniques are considered for use in the FACET facility at SLAC, which ... more Three temporal diagnostic techniques are considered for use in the FACET facility at SLAC, which will incorporate a unique two-bunch beam for plasma wakefield acceleration experiments. The results of these experiments will depend strongly on the the inter-bunch spacing as well as the longitudinal profiles of the two bunches. A reliable, singleshot, high resolution measurement of the beam's temporal profile
In this paper we describe the technical design of an ongoing proof-of-principle echo-enabled harm... more In this paper we describe the technical design of an ongoing proof-of-principle echo-enabled harmonic generation (EEHG) experiment at the Next Linear Collider Test Accelerator (NLCTA) at SLAC. We present the design considerations and the technical details of the experiment.
The Linac Coherent Light Source (LCLS) has used three copper photocathodes since its commissionin... more The Linac Coherent Light Source (LCLS) has used three copper photocathodes since its commissioning in 2007. Two of three copper cathodes had low initial quantum efficiency (QE) (<1×10) in the LCLS radio frequency (RF) gun. The two cathodes were exposed to the plasma cleaning in the cathode test chamber before installation in the RF gun. Recent studies at the SLAC RF gun test bed at the Accelerator Structure Test Area (ASTA) reveals that the pre-cleaning in the test chamber followed by cathode exposure to air for installation in the gun is the major factor leading to the low initial QE. All four cathodes, without the plasma pre-cleaning prior to the installation in the gun, have demonstrated initial QE>4×10 at the ASTA. Systematic studies also demonstrate that high-power RF gun operation provides an initial QE boost. In-situ laser cleaning for three new cathodes in the RF gun is extensively investigated, and a robust laser cleaning procedure is established at the ASTA with impr...
Physical Review Special Topics - Accelerators and Beams
The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project presentl... more 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.
Surface characterization of the LCLS RF gun cathode A. Brachmann On behalf of the LCLS commission... more Surface characterization of the LCLS RF gun cathode A. Brachmann On behalf of the LCLS commissioning team The first copper cathode installed in the LCLS RF gun was used during LCLS commissioning for more than a year. However, after high charge operation (~ 500 pC), the cathode showed a decline of quantum efficiency due to surface contamination caused by residual ionized gas species present in the vacuum system. We report results of SEM, XPS and XAS studies that were carried out on this cathode after it was removed from the gun. X-ray absorption and X-ray photoelectron spectroscopy reveal surface contamination by various hydrocarbon compounds. In addition we report on the performance of the second installed cathode with emphasis on the spatial distribution of electron emission.
In addition to its normal operation at 250pC, the LCLS has operated with 20pC bunches delivering ... more In addition to its normal operation at 250pC, the LCLS has operated with 20pC bunches delivering X-ray beams to users with energies between 800eV and 2 keV and with bunch lengths below 10 fs FWHM. A bunch arrival time monitor and timing transmission system provide users with sub 100 fs synchronization between a laser and the X-rays for pump / probe experiments. We describe the performance and operational experience of the LCLS for short bunch experiments.
Ultrafast optical lasers play an essential role in exploiting the unique capabilities of recently... more Ultrafast optical lasers play an essential role in exploiting the unique capabilities of recently commissioned X-ray free-electron laser facilities such as the Linac Coherent Light Source (LCLS). Pump–probe experimental techniques reveal ultrafast dynamics in atomic and molecular processes and reveal new insights in chemistry, biology, material science and high-energy-density physics. This manuscript describes the laser systems and experimental methods that enable cutting-edge optical laser/X-ray pump–probe experiments to be performed at LCLS.
The Early Injector Commissioning program for LCLS-II aims to demonstrate CW electron beam product... more The Early Injector Commissioning program for LCLS-II aims to demonstrate CW electron beam production this year in the first two meters of the injector that includes the room-temperature 185.7 MHz single-cell gun and the 1.3 GHz two-cell buncher cavity. These cavities were designed and built by LBNL based on their experience with similar ones for their Advanced Photo-Injector Experiment (APEX) program. With the 258 nm laser system and Cs2Te cathodes, bunches of up to 300 pC are expected at rates as high as 1 MHz. The paper presents results from this program including the vacuum levels achieved, RF processing and field control experience, dark current measurements and laser and beam characterization.
The LCLS FEL began user operations in September 2009 with photon energies from 800eV to 2 KeV and... more The LCLS FEL began user operations in September 2009 with photon energies from 800eV to 2 KeV and pulse energies above 2 mJ. Both long pulse (50-200 femtosecond FWHM) and short pulse (<10 femtosecond FWHM at 150 uJ) pulses were delivered at user request. In addition the FEL was operated at fundamental photon energies up to 10 KeV in preparation for hard X-ray experiments. FEL operating parameters, performance and reliability results will be presented, in addition to plans for upgrades to the facility. LCLS LINAC The LCLS project modified the last 1 kilometer of the SLAC high energy physics LINAC to provide a 15 GeV driver for an X-ray FEL. An RF gun and laser heater system were installed in an off-axis tunnel to produce a 250pC, beam with a typical normalized emittance of 0.5um. Two bunch compressors were added at the 250MeV and 4.3 GeV points on the LINAC to provide peak currents typically between 1 and 3 KA. (Fig. 1) [1]
The Linac Coherent Light Source (LCLS) X-ray FEL utilizing the last km of the SLAC linac has been... more The Linac Coherent Light Source (LCLS) X-ray FEL utilizing the last km of the SLAC linac has been operational since April 2009 and finished its first successful user run last December. The various diagnostics for electron beam properties including beam position monitors, wire scanners, beam profile monitors, and bunch length diagnostics are presented as well as diagnostics for the X-ray beam. The low emittance and ultra-short electron beam required for X-ray FEL operation has implications on the transverse and longitudinal diagnostics. The coherence effects of the beam profile monitors and the challenges of measuring fs long bunches are discussed.
For the Linac Coherent Light Source II (LCLS-II) project at SLAC, a 1.3 GHz superconducting rf (S... more For the Linac Coherent Light Source II (LCLS-II) project at SLAC, a 1.3 GHz superconducting rf (SRF) linac is being constructed that will generate 4 GeV electron bunches at a high repetition rate to drive x-ray free electron lasers. The LCLS-II electron source, which comprises the first three meters of the electron injector, includes two normal-conducting, continuous-wave rf cavities: a one-cell, 185.7 MHz gun and a two-cell, 1.3 GHz buncher. It also includes a gun load-lock system that allows photocathodes to be changed under vacuum. The components in this beam-line section were designed and built by Lawrence Berkeley National Laboratory based on experience from their advanced photoinjector experiment program. In combination with the SLAC UV laser system, the electron source is designed to produce beam rates up to 1 MHz with average currents up to $30\text{ }\text{ }\ensuremath{\mu}\mathrm{A}$ initially. The source was installed in mid-2018, well in advance of the SRF linac, which ...
Three temporal diagnostic techniques are considered for use in the FACET facility at SLAC, which ... more Three temporal diagnostic techniques are considered for use in the FACET facility at SLAC, which will incorporate a unique two-bunch beam for plasma wakefield acceleration experiments. The results of these experiments will depend strongly on the the inter-bunch spacing as well as the longitudinal profiles of the two bunches. A reliable, singleshot, high resolution measurement of the beam's temporal profile
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Papers by S. Gilevich