  Alpha emissivity measurements are important in the semiconductor industry for
assessing the suitability of materials for use in production processes. A
recently published round-robin study that circulated the same samples to
several alpha counting centers showed wide center-to-center variations in
measured alpha emissivity. A separate analysis of these results hypothesized
that much of the variation might arise from differences in sample-to-entrance
window separations. XIA recently introduced an ultra low background counter,
the UltraLo-1800 (UltraLo), that operates in a fundamentally different manner
from the proportional counters used at most of the centers in the original
study. In particular, by placing the sample within the counting volume, it
eliminates the sample-to-entrance window separation issue noted above, and so
offers an opportunity to test this hypothesis. In this work we briefly review
how the UltraLo operates and describe a new round-robin study conducted
entirely on UltraLo instruments using a set of standard samples that included
two samples used in the original study. This study shows that, for LA (Low
Alpha between 2 and 50 alpha/khr-cm$^2$) sample measurements, the only
remaining site-to-site variations were due to counting statistics. Variations
in ULA (Ultra-Low Alpha < 2 alpha/khr-cm$^2$) sample measurements were reduced
three-fold, compared to the earlier study, with the measurements suggesting
that residual activity variations now primarily arise from site-to-site
differences in the cosmogenic background.
