Optical Design of a Broadband Infrared Spectrometer for Bunch Length Measurement at the Linac Coherent Light Source

[摘要] The electron pulses generated by the Linac Coherent Light Source at the SLAC National Accelerator Laboratory occur on the order of tens of femtoseconds and cannot be directly measured by conventional means. The length of the pulses can instead be reconstructed by measuring the spectrum of optical transition radiation emitted by the electrons as they move toward a conducting foil. Because the emitted radiation occurs in the mid-infrared from 0.6 to 30 microns a novel optical layout is required. Using a helium-neon laser with wavelength 633 nm, a series of gold-coated off-axis parabolic mirrors were positioned to direct a beam through a zinc selenide prism and to a focus at a CCD camera for imaging. Constructing this layout revealed a number of novel techniques for reducing the aberrations introduced into the system by the off-axis parabolic mirrors. The beam had a recorded radius of less than a millimeter at its final focus on the CCD imager. This preliminary setup serves as a model for the spectrometer that will ultimately measure the LCLS electron pulse duration.

[发布日期] 2012-09-07

[学科分类] 核物理和高能物理

[关键词] CAMERAS;DESIGN;ELECTRONS;FERMILAB ACCELERATOR;HELIUM-NEON LASERS;INFRARED SPECTROMETERS;LIGHT SOURCES;LINEAR ACCELERATORS;MIRRORS;PRISMS;RADIATIONS;SPECTROMETERS;STANFORD LINEAR ACCELERATOR CENTER;TRANSITION RADIATION;WAVELENGTHS;ZINC SELENIDES Accelerators;OTHER