DESIGN OF AN ELECTRONIC CHARGED-PARTICLE SPECTROMETER TO MEASURE [RHO-R] ON INERTIAL FUSION EXPERIMENTS

The design and fabrication of a new diagnostic that measures the energ y spectra of charged particles from targets on the Omega Upgrade are a ctively underway. Using seven 512x512 charge coupled devices (CCDs) an d a 7.5 kG permanent magnet, this instrument will uniquely determine p article identities and measure particle energies from 1 MeV up to the maximum charged particle energies of interest for rho R measurements ( 10.6 MeV knock-on tritons, 12.5 MeV knock-on deuterons and 30.8 MeV te rtiary protons). The resolution of the diagnostic will be better than 5%. We have tested the response of SITe back-illuminated CCDs to 1.2-1 3.6 MeV protons from our Cockcroft-Walton accelerator and to alpha par ticles from an Am-241 source, and the results agree extremely well wit h predictions. With its high density picture elements, each CCD has 10 (5) single-hit detectors. In the case of a low DT yield of 10(9) neutr ons, about 100 knock-on charged particles will be detected when the sp ectrometer aperture is 60 cm from the implosion. Measurements of pR up to 150 mg/cm(2) can be obtained from knock-on D and T spectra, and va lues up to 300 mg/cm(2) can be determined from secondary proton spectr a. The sensitivity of the CCDs to 14 and 2.5 MeV neutrons has been exp erimentally determined using our Cockcroft-Walton accelerator source a nd indicates that by incorporating neutron shielding, the signal to ne utron noise ratio at a yield of 10(11) will be better than 100:1. Ln t he development phases of this program, we plan to utilize CR-39 track detectors concurrently with the CCDs. (C) 1997 American Institute of P hysics.