SPIDER neutron diagnostic: Overall System Description

This document presents design, installation and commissioning of the CNESM neutron diagnostic for SPIDER. It is submitted as Progress Report P1.1 of subtask T3.5 of the F4E contract F4E-RFX-PMS_A-WP-2019. This is an update of the previous version, RFX_SPIDER_TN_169_r7, submitted as deliverable of the F4E contract F4E-RFX-PMS_A-WP-2018. This report is devoted to the overall description of the design, installation and commissioning of the neutron diagnostic for SPIDER. The design was supported by exhaustive tests performed on three nGEM detector prototypes and on the full scale nGEM detector prototypes, reported in RFX_SPIDER_TN_170. In 2019 installation of the CNESM diagnostic was completed and commissioning has shown successful results in dry runs without vacuum pumping and RF operation. These two operating conditions introduced unacceptable noise level but tests in situ have demonstrated the cause and indicated a suitable remedy, which will be implemented next year, before significant deuterium beam operation. In 2019 a new time resolved neutron yield monitor based on a liquid scintillator was also installed and commissioned in dry runs. This monitor will benchmark the measurements performed by the CNESM system.