X-Ray Spectrometry Using Cauchois Geometry For Temperature Diagnostics Jeffrey Zimmerman, Eric Galtier 1Your Affiliation. 2Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA. +Contact: egaltier@slac.stanford.edu Introduction Assessing Temperature Standard Configuration Experimental Setup The primary source of radiation from any hot plasma is from Bremstrahlung radiation. This occurs when thermally excited electrons are accelerated in the presence of the electric field created by positive ions. In order to accurately assess the electron temperature of an excited plasma, a temperature dependency of spectra must be established. To do this, Kramer’s law for free-free radiation is used. X-Ray Parameters Long Pulse Laser Photon energy: Lasing Medium: Glass 4 – 12 KeV Pulse duration: Wavelength: 527nm 60 – 300 fs Pulse energy: 2 – 200 ns 1 – 3 mJ Pulse energy: ~1 J/ns per arm, max. 40 J in 20ns PRF: 120 Hz Pulse shape: Square or ramp for steady drive shock. Beam diameter: 100 – 500 μm Varying the temperature, Te, allows us to plot the temperature dependence of the spectral lines. Here, we attempt to characterize the x-ray spectra created by short pule (fs) laser interactions with matter. A curved, Cauchois type crystal is used for a diffraction grating, allowing shorter focal length and larger spectral range. The spectra is then fitted to a temperature-spectra graph to determine the electron temperature. Keywords: Bremsstrahlung, radiation, x-ray, spectrometer, Cauchois Fig. 1: Intensity of X-Ray spectra from various different plasma temperatures. Cauchois Type Crystallography Cauchois spectrometers use a special crystal geometry. Cylindrically bent with crystal faces normal to the surface, a Cauchois crystal can view a greater spectral range while allowing for shorter focal lengths. Conclusions Experiments show that Bremsstrahlung X-Ray spectrometry is an accurate tool to measure the intensity of X-Rays emitted from hot plasmas. Furthermore, it can be used to determine the temperature of hot electrons in said plasmas. To improve results, better filtering of primary radiation from Kα and Kβ lines should be implemented. Observing a high energy laser pulse with the Cauchois spectrometer like the one pictured, a continuous spectrograph is obtained. Acknowledgments Rotation of the crystal with respect to the detector changes the spectral range of the crystal for photon energies between 8 KeV to 50 KeV. Use of the Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. [1] J. Seely, A. Henins, U. Feldman, Rev. of Scientific Instruments 87, 053101 (2016) [2] John Seely and Uri Feldman, Artep Inc., 5/4/2018 [3] U. Zastrau, Phys. Rev. E 78, 066406 (2008) [3] Quarts has a crystal lattice with six faces. This allows for a greater range of spectra to be measured with the bent face of the Cauchois spectrometer. Fig 2: X-Ray Spectrograph showing continuous and discreet spectra [2]. Plot of the intensity of spectrograph on left. [3] The spectrographs intensity at each point is then measured and plotted on a graph. The plot is fitted to the simulated graph of the bremsstrahlung radiation and the temperature discerned from there. [1] Date: MM/DD/YYYY