A new large-area 2pi proportional counting system at NIST

A new large-area gas flow multi-wire proportional counter has been developed to replace the large-area counting system that is currently in use at the National Institute of Standards and Technology (NIST) and several Department of Defense counting facilities for calibrating large-area alpha and beta sources. The current systems are over 20 years old and part replacement is very difficult. The new systems have been built using specifications that will improve on the current systems and allow collecting data at pressures up to 0.2MPa. The ability to operate at higher pressures will increase the beta efficiency of the counter and lead to improved precision in the final measured results. Comparison of the results from the old and new systems is presented for both alpha and beta sources.