Charge Carrier Density and Signal Induced in a CVD Diamond Detector from NIF DT Neutrons, x-rays, and Electrons

摘要

This report investigates the use of x-rays and electrons to excite a CVD polycrystalline diamond detector during a double pulse experiment to levels corresponding to those expected during a successful (1D clean burn) and a typical failed ignition (2D fizzle) shot at the National Ignition Facility, NIF. The monitoring of a failed ignition shot is the main goal of the diagnostic, but nevertheless, the study of a successful ignition shot is also important. A first large neutron pulse is followed by a smaller pulse (a factor of 1000 smaller in intensity) after 50 to 300 ns. The charge carrier densities produced during a successful and failed ignition shot are about 10(sup 15) e-h+/cm(sup 3) and 2.6* 10(sup 12) e-h+/cm(sup 3) respectively, which is lower than the 10(sup 16) e-h+/cm(sup 3) needed to saturate the diamond wafer due to charge recombination. The charge carrier density and the signal induced in the diamond detector are calculated as a function of the incident x-ray and electron energy, flux, and detector dimensions. For available thicknesses of polycrystalline CVD diamond detectors (250 (micro)m to 1000 (micro)m), a flux of over 10(sup 11) x-rays/cm(sup 2) (with x-ray energies varying from 6 keV to about 10 keV) or 10(sup 9) (beta)/cm(sup 2) (corresponding to 400 pC per electron pulse, E(sub (beta)) > 800 keV) is necessary to excite the detector to sufficient levels to simulate a successful ignition's 14 MeV peak.