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Circular polarization control for the LCLS baseline in the soft X-ray regime

Abstract

The LCLS baseline includes a planar undulator system, which produces intense linearly polarized light in the wavelength range 0.15-1.5 nm. In the soft X-ray wavelength region polarization control from linear to circular is highly desirable for studying ultrafast magnetic phenomena and material science issues. Several schemes using helical undulators have been discussed in the context of the LCLS. One consists in replacing three of the last planar undulator segments by helical (APPLE III) ones. A second proposal, the 2nd harmonic helical afterburner, is based on the use of short, crossed undulators tuned to the second harmonic. This last scheme is expected to be the better one. Its advantages are a high (over 90%) and stable degree of circular polarization and a low cost. Its disadvantage is a small output power (1% of the power at the fundamental harmonic) and a narrow wavelength range. We propose a novel method to generate 10 GW level power at the fundamental harmonic with 99% degree of circular polarization from the LCLS baseline. Its merits are low cost, simplicity and easy implementation. In the option presented here, the microbunching of the planar undulator is used too. After the baseline undulator, the electron beam is sent  More>>
Authors:
Geloni, Gianluca; [1]  Kocharyan, Vitali; Saldin, Evgeni [2] 
  1. European XFEL GmbH, Hamburg (Germany)
  2. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
Publication Date:
Dec 15, 2010
Product Type:
Technical Report
Report Number:
DESY-10-252
Subject:
43 PARTICLE ACCELERATORS; BEAM BUNCHING; BEAM PRODUCTION; BEAM TRANSPORT; BERYLLIUM; COULOMB SCATTERING; ELECTRON BEAMS; ELECTRON COLLISIONS; EV RANGE 100-1000; FOILS; FREE ELECTRON LASERS; HARMONIC GENERATION; HELICAL CONFIGURATION; KEV RANGE 01-10; ONDULATOR RADIATION; PHOTON BEAMS; POLARIZATION; SOFT X RADIATION; WIGGLER MAGNETS; X-RAY LASERS; X-RAY SOURCES
OSTI ID:
21401037
Research Organizations:
Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
Country of Origin:
Germany
Language:
English
Other Identifying Numbers:
Other: ISSN 0418-9833; TRN: DE11F1941
Availability:
Commercial reproduction prohibited; INIS; OSTI as DE21401037
Submitting Site:
DEN
Size:
18 pages
Announcement Date:
Mar 15, 2011

Citation Formats

Geloni, Gianluca, Kocharyan, Vitali, and Saldin, Evgeni. Circular polarization control for the LCLS baseline in the soft X-ray regime. Germany: N. p., 2010. Web.
Geloni, Gianluca, Kocharyan, Vitali, & Saldin, Evgeni. Circular polarization control for the LCLS baseline in the soft X-ray regime. Germany.
Geloni, Gianluca, Kocharyan, Vitali, and Saldin, Evgeni. 2010. "Circular polarization control for the LCLS baseline in the soft X-ray regime." Germany.
@misc{etde_21401037,
title = {Circular polarization control for the LCLS baseline in the soft X-ray regime}
author = {Geloni, Gianluca, Kocharyan, Vitali, and Saldin, Evgeni}
abstractNote = {The LCLS baseline includes a planar undulator system, which produces intense linearly polarized light in the wavelength range 0.15-1.5 nm. In the soft X-ray wavelength region polarization control from linear to circular is highly desirable for studying ultrafast magnetic phenomena and material science issues. Several schemes using helical undulators have been discussed in the context of the LCLS. One consists in replacing three of the last planar undulator segments by helical (APPLE III) ones. A second proposal, the 2nd harmonic helical afterburner, is based on the use of short, crossed undulators tuned to the second harmonic. This last scheme is expected to be the better one. Its advantages are a high (over 90%) and stable degree of circular polarization and a low cost. Its disadvantage is a small output power (1% of the power at the fundamental harmonic) and a narrow wavelength range. We propose a novel method to generate 10 GW level power at the fundamental harmonic with 99% degree of circular polarization from the LCLS baseline. Its merits are low cost, simplicity and easy implementation. In the option presented here, the microbunching of the planar undulator is used too. After the baseline undulator, the electron beam is sent through a 40 m long straight section, and subsequently passes through a short helical (APPLE II) radiator. In this case the microbunch structure is easily preserved, and intense coherent radiation is emitted in the helical radiator. The background radiation from the baseline undulator can be easily suppressed by letting radiation and electron beamthrough horizontal and vertical slits upstream the helical radiator, where the radiation spot size is about ten times larger than the electron bunch transverse size. Using thin Beryllium foils for the slits the divergence of the electron beam halo will increase by Coulomb scattering, but the beam will propagate through the setup without electron losses. The applicability of our method is not restricted to the LCLS baseline setup. Other facilities e. g. LCLS II or the European XFEL may benefit from this work as well, due to availability of sufficiently long free space at the end of undulator tunnel. (orig.)}
place = {Germany}
year = {2010}
month = {Dec}
}