Performance of the upgraded multichannel neutron collimator

The original ZnS based NE451 detectors become saturated at the highest levels of D-D operation. A new less sensitive detector configuration, also based on ZnS crystals, was designed and tested at PPPL in order to extend the collimator capabilities to D-T plasma operation. The new detector design is composed of a thin layer of ZnS powder uniformly deposited between two layers of Plexiglas. The detector capabilities are further extended by upgraded signal processing electronics for a total enhancement of ∼1000x compared to the original detector system. An array of these detectors has been installed on TFTR in tandem with the original detector system. The current mode is presently being implemented on the original NE451 detectors. This will extend their capabilities and allow for greater overlap in data taken in the crossover region between the two detector systems. The performance of the collimator system will be illustrated by neutron data obtained during D-T operation