Flux Measurements at CG-1D

The measurements performed in August and October of 2024 indicate that the capture flux averaged over a 5 mm diameter region at the Optics Box exit for CG-1D (MARS) ranges from 7.5E7 to 1.9E9 n/cm²/s, depending on instrument aperture selection. Corresponding number fluxes are estimated to be approximately a factor two lower, consistent with an average wavelength of 3.6 Å, although that estimate is driven by assumptions that the measured spectra and the calculated spectra are generally consistent. At the largest instrument aperture, the measured capture flux (1.9E9 n/cm²/s) is nearly a factor three lower than the capture flux estimated from the 2011 measurement (5.3E9 n/cm²/s), and nearly a factor five lower than the 2001 prediction (8.2E9 n/cm²/s), which are for different locations and/or instrument configurations.