Preliminary Neutronics Analysis of 
ITER Tip Diagnostic Corner Cube Retroreflectors

Authors: K.R. Tresemer, R. Wood, R. Feder, L. Konkel Jr., J. Klabacha

Abstract:  ITER is an international project under construction in France that will demonstrate nuclear fusion at a power plant-relevant scale.  The Toroidal Interferometer and Polarimeter (TIP) Diagnostic will be used to measure the plasma electron line density along 5 laser-beam chords.  This line-averaged density measurement will be input to the ITER feedback-control system.  The TIP is considered the primary diagnostic for these measurements, which are needed for basic ITER machine control.  Therefore, system reliability and accuracy is a critical element in TIP's design.  There are two major challenges to the reliability of the TIP system.  First is the survivability and performance of in-vessel optics and second is maintaining optical alignment over long optical paths and large vessel movements.  Both of these issues greatly depend on minimizing the overall distortion due to neutron & gamma heating of the Corner Cube Retroreflectors (CCRs).  These are small optical mirrors embedded in five locations in the vacuum vessel wall, corresponding to certain plasma tangency radii.  During the development of the design and location of these CCRs, several iterations of neutronics analyses were performed to determine and minimize the total distortion due to nuclear heating of the CCRs.

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Presented at:  TOFE 2014, Anaheim, CA, November 9-13th, 2014

Submitted to:  Fusion Science and Technology
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Download PPPL-5175 (pdf 2 MB 7 pp)
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