Fusion Science and Technology / Volume 53 / Number 3 / April 2008 / Pages 841-853
Recent study of fusion reactions within an inertial electrostatic confinement (IEC) device revealed several significant modes of fusion: converged core, beam-target, beam-background, and charge-exchange reactions. In an attempt to understand the fusion product proton measurements in the IEC device, the advanced fuel D-D and D-3He fusion proton energy spectra were analyzed. For D-3He fusion, the beam-target reactions were found to dominate. Hence, the present study focuses on understanding the beam-target reactions and the corresponding proton energy spectra from such sources. This information helps in accurately calculating the proton flux for optimizing medical isotope production and other near-term applications, besides calibration of the proton detectors.
A proton detector was used to measure the experimental data and the Monte Carlo stopping power and range in matter (SRIM) simulation code was used to explain the corresponding experimental observations. While the D-D proton spectrum from the IEC device showed combined Doppler and scatter broadening, the D-3He proton spectrum, besides showing the broadening, also shows some interesting characteristics such as a high-energy tail and a detector thickness-dependent energy spectrum. An extended high-energy tail occurs in the observed energy spectrum from the detector because some of the protons go through the wire before being detected, which reduces their total energy. Due to the higher proton stopping power in the detector at somewhat lower energies than the initial 14.7 MeV, these protons thus deposit a larger fraction of their energy and create the high-energy tail. These measurements show that the high-energy tail of the proton energy spectrum should be excluded from the total proton counts for an accurate proton rate measurement.