Measurement of apparent ion temperature using the magnetic recoil spectrometer at the OMEGA laser facility

The Magnetic Recoil neutron Spectrometer (MRS) at the OMEGA laser facility has been routinely used to measure deuterium-tritium (DT) yield and areal density in cryogenically layered implosions since 2008. Recently, operation of the OMEGA MRS in higher-resolution mode with a new smaller, thinner (4 cm2, 57 μm thick) CD2 conversion foil has also enabled inference of the apparent DT ion temperature (Tion) from MRS data. MRS-inferred Tion compares well with Tion as measured using neutron time-of-flight spectrometers, which is important as it demonstrates good understanding of the very different systematics associated with the two independent measurements. The MRS resolution in this configuration, ΔEMRS = 0.91 MeV FWHM, is still higher than that required for a high-precision Tion measurement. We show how fielding a smaller foil closer to the target chamber center and redesigning the MRS detector array could bring the resolution to ΔEMRS = 0.45 MeV, reducing the systematic Tion uncertainty by more than a factor...