Implementation and testing of the JET gamma-ray cameras neutron filters pneumatic system

Neutron filters/attenuators have been designed and constructed as an upgrade of the JET gamma-ray cameras (GRC's). This diagnostics upgrade should reduce the neutron flux at the gamma-ray detectors in a way that it would make possible gamma-ray imaging measurements in high power deuterium JET pulses, and eventually in deuterium-tritium discharges. The attenuators will be placed within the GRC diagnostics system between the vacuum vessel port and the camera collimator radiation shields in the case of both the horizontal camera and the vertical one and they have to be moved out of the detector line of sight when the neutron/gamma camera diagnostics is used for neutron measurements. The neutron filters will operate in a very harsh electromagnetic environment. It is thus recommended to avoid as much as possible the use of electrical and electronic components for the attenuator steering and control (in particular, for attenuator steering). Therefore a steering and control system based on pneumatic components was designed and constructed. The attenuators together with the steering and control system have been installed on a test stand, which is a 1-1 scale replica of the JET structures where neutron filters are to be installed and successfully tested.