The Physics Analysis of a Gas Attenuator with Argon as a Working Gas

A gas attenuator is an important element of the LCLS facility. The attenuator must operate in a broad range of x-ray energies, provide attenuation coefficient between 1 and 10 with the accuracy of 1% and, at the same time, be reliable and allow for many months of un-interrupted operation. S. Shen [1] has recently carried out a detailed design study of the attenuator based on the use of nitrogen as a working gas. In this note we assess the features of the attenuator based on the use of argon. We concentrate on the physics issues, not the design features. Disclaimer This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. 1 This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. Work supported in part by the DOE Contract DE-AC02-76SF00515. This work was performed in support of the LCLS project at SLAC. UCRL-TR-217980 LCLS-TN-06-1 January 11, 2006