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Title |
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| THPPH055 |
Nonintercepting Beam Size and Position Monitor Using ODR for X-Ray FELs
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710 |
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- A. H. Lumpkin, W. Berg, N. Sereno, B. X. Yang, C. Yao
ANL, Argonne, Illinois
- D. W. Rule
NSWC, West Bethesda, Maryland
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Interest in nonintercepting (NI) beam size and position diagnostics in the undulators of x-ray free-electron lasers (XFELs) is driven by the requirement of beam-emittance matching, as well as by the need to minimize radiation damage to the undulator's permanent magnets from scattered beam produced by the insertion of converter screens. For these reasons, our investigations on optical diffraction radiation (ODR) as NI relative beam size and position diagnostics are particularly relevant to XFELs. We report the extensions of our studies at 7-GeV beam energy to aspects of the vertical and horizontal polarization components of the ODR near-field and far-field images. The near-field, vertically polarized data are particularly interesting since the vertical field lines at the metal more directly reflected the actual beam sizes. Although our experiments to date are with larger beams and impact parameters of 1-2 mm, our analytical model indicates that this technique scales with beam size and has sensitivity at the 20- to 50-micron regime with an impact parameter, d = 5 times σ-y =100 microns. This is the x-ray FEL intraundulator beam size regime.
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| THPPH056 |
Initial Search for 9-keV XTR from a 28-GeV Beam at SPPS*
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714 |
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- A. H. Lumpkin
ANL, Argonne, Illinois
- J. B. Hastings
SLAC, Menlo Park, California
- D. W. Rule
NSWC, West Bethesda, Maryland
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The potential to use x-ray transition radiation (XTR) as a beam diagnostic and coherent XTR (CXTR) as a gain diagnostic in an x-ray FEL was proposed previously. At that time we noted that the unique configuration of the SLAC Sub-picosecond Photon Source (SPPS) with its known x-ray wiggler source, a special three-element x-ray monochromator, x-ray transport line, and experimental end station with x-ray detectors made it an ideal location for an XTR feasibility experiment. A test of XTR intensity with respect to the x-rays emitted by the SPPS wiggler was proposed. The three-element monochromator was first adjusted to transport 9-keV or 1.3-Angstrom x rays from the SPPS wiggler source to the camera. The expected source strength in the bandpass of the monochromator was about 2x107 photons per 3 nC electron pulse, and our calculated XTR intensity was about 103 photons. We first successfully imaged the SPPS x-ray beam with the ANDOR x-ray CCD by using an Al-foil attenuation of 4x103. The wiggler gap was then opened, and x-ray images recorded with the Ti foils out for background evaluation and with the Ti foils inserted to search for XTR. Initial images will be presented.
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