|Author||Sangster, T. C. ♦ Glebov, V. Yu. ♦ Lerche, R. A. ♦ Phillips, T. W. ♦ Stoeckl, C. ♦ Padalino, S. J. ♦ Olliver, H. ♦ Thompson, S.|
|Source||United States Department of Energy Office of Scientific and Technical Information|
|Publisher||The American Physical Society|
|Subject Keyword||PHYSICS OF ELEMENTARY PARTICLES AND FIELDS ♦ CALIBRATION ♦ DISCRIMINATORS ♦ IMPLOSIONS ♦ LASERS ♦ NEUTRON SPECTROMETERS ♦ NEUTRONS ♦ PRODUCTION ♦ RESOLUTION ♦ RESPONSE FUNCTIONS ♦ TARGET CHAMBERS ♦ TIME-OF-FLIGHT SPECTROMETERS|
|Abstract||The MEDUSA array is a multielement, scintillator-based neutron time-of-flight spectrometer designed primarily to measure primary and secondary neutron production from indirect drive DD and DT capsule implosions at the Omega Laser in Rochester, NY. The array consists of 824 identical scintillator-photomultiplier tube detectors coupled to analog signal discriminators and high resolution, multihit time-to-digital converters, and is located 19.4 m from the center of the Omega target chamber. It is possible to accurately measure the neutron energy spectrum by simply measuring an adequate sample of neutron flight times to the array (the burn time width is negligible). However it is essential to understand the response of the array detectors to the fusion neutrons before an energy spectrum can be deduced from the data. This array response function is generally given in terms of a calibration constant that relates the expected number of detector hits in the array to the number of source neutrons. The calibration constant is a function of the individual detector gains, the thresholds of the discriminators, and the amount of neutron attenuating material between the array and the target. After gain matching the detectors, a calibration constant can be generated by comparing the array response against a known yield of neutrons (this requires dozens of implosions) or from a first principles measurement of the individual detector efficiencies. In this article, we report on the results of both calibrations of the MEDUSA array. In particular, we will focus on the issues and errors associated with the very different measurements required and discuss a new technique being considered for rapid in situ future calibrations.|
|Learning Resource Type||Article|
|Publisher Place||United States|
|Journal||Review of Scientific Instruments|
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