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Title: Shaping X-Ray Pulses at LCLS - Oral Presentation

Authors:
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1213173
Report Number(s):
SLAC-WP-127
DOE Contract Number:
AC02-76SF00515
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
OTHER

Citation Formats

West, Gavin. Shaping X-Ray Pulses at LCLS - Oral Presentation. United States: N. p., 2015. Web. doi:10.2172/1213173.
West, Gavin. Shaping X-Ray Pulses at LCLS - Oral Presentation. United States. doi:10.2172/1213173.
West, Gavin. 2015. "Shaping X-Ray Pulses at LCLS - Oral Presentation". United States. doi:10.2172/1213173. https://www.osti.gov/servlets/purl/1213173.
@article{osti_1213173,
title = {Shaping X-Ray Pulses at LCLS - Oral Presentation},
author = {West, Gavin},
abstractNote = {},
doi = {10.2172/1213173},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2015,
month = 8
}

Technical Report:

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  • This presentation covers data collected on two commercial laser stabilization systems, Guidestar-II and MRC, and two optical imaging systems. Additionally, general information about LCLS-II and how to go about continuing-testing is covered.
  • The LCLS injector must operate at 120 Hz repetition frequency but to date the maximum operating frequency of an S-band rf gun has been 50 Hz. The high fields desired for the LCLS gun operation limit the repetition frequency due to thermal expansion causing rf detuning and field redistribution. One method of addressing the thermal loading problem is too reduce the power lost on the cavity walls by properly shaping the rf pulse incident on the gun. The idea is to reach the steady state field value in the gun faster than the time constant of the gun would allowmore » when using a flat incident rf pulse. By increasing the incident power by about a factor of three and then decreasing the incident power when the field reaches the desired value in the gun, the field build up time can be decreased by more than a factor of three. Using this technique the heat load is also decreased by more than a factor of three. In addition the rf coupling coefficient can be increased from the typical critically coupled designs to an overcoupled design which also helps reduce the field build up time. Increasing the coupling coefficient from 1 to 2 reduces the heat load by another 25% and still limits the reflected power and coupling hole size to manageable levels.« less
  • A proposal has been made to generate femtosecond and sub-femtosecond x-ray pulses in the Linac Coherent Light Source (LCLS) SASE FEL by using a slotted spoiler foil located at the center of the second bunch compressor chicane. This previous study highlighted a simple case, using the nominal LCLS parameters, to produce a 2-fsec FWHM, 8-keV x-ray pulse. The study also pointed out the possibility of attaining sub-femtosecond pulses by somewhat modifying the LCLS compression parameters, but did not undertake a full study for this more aggressive case. We take the opportunity here to study this ''attosecond'' case in detail, includingmore » a full tracking simulation, exploring the limits of the technique.« less
  • The free-electron laser at LCLS produces X-Rays that are used in several facilities. This light source is so bright and quick that we are capable of producing movies of objects like proteins. But making these movies would not be possible without a device that can detect the X-Rays and produce images. We need X-Ray cameras. The challenges LCLS faces include the X-Rays’ high repetition rate of 120 Hz, short pulses that can reach 200 femto-seconds, and extreme peak brightness. We need detectors that are compatible with this light source, but before they can be used in the facilities, they mustmore » first be characterized. My project was to do just that, by making a computer simulation program. My presentation discusses the individual detectors I simulated, the details of my program, and how my project will help determine which detector is most useful for a specific experiment.« less
  • Carbon dioxide (CO 2) emission into the atmosphere has increased tremendously through burning of fossil fuels, forestry, etc.. The increased concentration has made CO 2 reductions very attractive though the reaction is considered uphill. Utilizing the sun as a potential energy source, CO 2 has the possibility to undergo six electron and four proton transfers to produce methanol, a useable resource. This reaction has been shown to occur selectively in an aqueous pyridinium solution with a gallium phosphide (GaP) electrode. Though this reaction has a high faradaic efficiency, it was unclear as to what role the GaP surface played duringmore » the reaction. In this work, we aim to address the fundamental role of GaP during the catalytic conversion, by investigating the interaction between a clean GaP surface with the reactants, products, and intermediates of this reaction using X-ray photoelectron spectroscopy. We have determined a procedure to prepare atomically clean GaP and our initial CO 2 adsorption studies have shown that there is evidence of chemisorption and reaction to form carbonate on the clean surface at LN2 temperatures (80K), in contrast to previous theoretical calculations. These findings will enable future studies on CO 2 catalysis.« less