When helium leak detecting is hindered by a system or atmosphere saturated with helium, leak checking can be continued by modifying the DuPont 120SSA/24-120 Mass Spectrometer Leak Detector to detect neon. Although DuPont markets a three gas leak detector (helium, neon and argon), the DuPont 120SSA/24-120 is convertible to neon by simply changing the magnet and retuning for neon peak. The sensitivity is 2 x 10/sup -9/ Atm/cc/sec/division neon. If an increase in sensitivity is desired, throttle diffusion pump with valve or install choke. Modification procedures and tuning procedures are described. (WHK)

The advantages of conversion from Diatron 20 to Diatron 4 are discussed including economics, multi-gas detection capability, and improved helium sensitivity. Conversion procedures are described. (WHK)