Computer acquisition and analysis of metastable transition data using electric sector voltage variation

A program and interface for a DEC PDP-8/I with 4K memory and two 32K discs have been devised to acquire peak intensity data from a double-focusing Hitachi RMU-7 mass spectrometer as a function of time while varying both the magnetic field intensity and the electric sector voltage. The electric sector voltage variation is accomplished by sweeping the electric sector voltage at selected rates: typically, 250 V is swept in 0.5 s. When a signal is detected from the detector amplifier, the sector that contains eight or more samples is reduced whenever data are not being acquired, and the compacted result is stored on the disc. After data acquisition, time-to-M/z conversion is accomplished using two peak identifications: the mass spectrum is determined from the rho=unity data; interpolations provided the value of msup(*) and rhosup(*); and the mass spectrum and identified metastable transitions are output off-line. The performance and current limitations of the system are discussed. (Auth.)