Paper | Title | Page |
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MOC02 |
Correlated Energy Spread Removal with Space Charge for High Gain Harmonic Generation | |
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We study the effect of longitudinal space charge on the correlated energy spread of a relativistic beam that has been microbunched for the emission of coherent, high harmonic radiation. We show that, in the case of microbunching induced by a laser modulator followed by a dispersive chicane, longitudinal space charge forces can act to significantly reduce the induced energy spread of the beam without a reduction in the harmonic bunching content. This effect may be optimized to significantly increase the harmonic number achievable in seeded HGHG free electrons lasers, which are otherwise limited by the induced energy spread from the laser.
The work presented here has been published in Reference [1]. [1] E. Hemsing et al., to appear in Phys. Rev. Lett. (2014) |
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Slides MOC02 [4.092 MB] | ||
MOT01 |
FEL Theory | |
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Tutorial | ||
Slides MOT01 [5.100 MB] | ||
TUB03 | FEL Overcompression in the LCLS | 337 |
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Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515 Overcompression of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center is studied. The studies and operational implications are summarized in this talk. |
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Slides TUB03 [4.493 MB] | ||
TUP035 | Investigation of Reverse Taper to Optimize the Degree of Polarization for the Delta Undulator at the LCLS | 465 |
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Funding: U.S. Department of Energy under contract No. DE-AC02-76SF00515 A 3.2 m adjustable phase Delta undulator* will soon be installed on the last girder of the LCLS undulator line. The Delta undulator will act as an afterburner terminating the 33 undulator line, providing arbitrary polarization control to users. Two important figures of merit for users will be the degree of polarization and the x-ray yield. In anticipation of this installation, machine development time at the LCLS was devoted to maximizing the final undulator x-ray contrast and yield with a standard canted pole undulator acting as a stand in for the Delta undulator. Following the recent suggestion** that a reverse taper (dK/dz > 0) in the main undulator line could suppress linearly polarized light generated before an afterburner while still producing the requisite microbunching, we report on a reverse taper study at the LCLS wherein a yield contrast of 15 was measured along the afterburner. We also present 1D simulations comparing the reverse taper technique to other schemes. * Nuhn, H.-D., Anderson, S., Bowden, G., Ding, Y., Gassner, G., et al., (2013). ** Schneidmiller, E. A. and Yurkov, M. V., Phys. Rev. ST Accel. Beams 16, 110702 (2013). |
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TUC02 |
Soft X-ray Self-seeding Setup and Results at LCLS | |
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The soft X-ray self seeding program was designed to provide near transform-limited pulses in the range of 500 eV to 1000 eV. The project was a three-way collaboration between SLAC, Lawrence Berkeley National Lab, and the Paul Scherrer Institute in Switzerland. Installation finished in the Fall of 2013, and after the early stages of commissioning we have measured up to 0.5mJ pulse energy and resolving powers of up to 5000 across the design wavelength range, representing a several-fold increase in the brightness compared to the normal LCLS operating mode. Future work will aim to increase the total pulse energy and establish self-seeding as a robust user operation mode. | ||
Slides TUC02 [10.464 MB] | ||
THP025 | Linear Accelerator Design for the LCLS-II FEL Facility | 743 |
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Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-76SF00515. The LCLS-II is an FEL facility proposed in response to the July 2013 BESAC advisory committee, which recommended the construction of a new FEL light source with a high-repetition rate and a broad photon energy range from 0.2 keV to at least 5 keV. A new CW 4-GeV electron linac is being designed to meet this need, using a superconducting (SC) L-band (1.3 GHz) linear accelerator capable of operating with a continuous bunch repetition rate up to 1 MHz at ~16 MV/m. This new 700-m linac is to be built at SLAC in the existing tunnel, making use of existing facilities and providing two separate FELs, preserving the operation of the existing FEL, which can be fed from either the existing copper or the new SC linac. We briefly describe the acceleration, bunch compression, beam transport, beam switching, and electron beam diagnostics. The high-power and low-level RF, and cryogenic systems are described elsewhere. |
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Poster THP025 [0.627 MB] | ||
THC01 |
Double Bunch X-ray Free Electron Laser for High-intensity Two Color X-rays | |
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Two color x-ray pulses have been the subject of intense research at fourth generation light sources, as they enable a wide range of new applications, from anomalous diffraction imaging to ultra-fast x-ray pump x-ray probe experiments. To extend the two color capabilities of the LCLS, double bunch operation has been recently demonstrated and successfully delivered to user experiments. In this scheme two closely spaced bunches are generated in the injector and accelerated off-crest to two different energies. The resulting bunch train radiates a two-color x-ray pulse in the undulator. The relative time delay and energy difference of the two pulses are tunable independently, by taking advantage of the LCLS two stage compression system. The distinct advantage of this approach is the possibility of using the entire undulator length on both colors, thus allowing applications that require high-intensity and/or self-seeding with a large spectral separation (up to ~1-2%). We review the experimental results and discuss our operational experience with user experiments. | ||
Slides THC01 [2.156 MB] | ||