A review of results obtained with the MPC time interval processor

The Time Interval Processor (TIP) was part of the Monitor Proportional Counter (MPC) of the Einstein Observatory. The MPC was an UHURU class argon-gas-filled proportional counter. The TIP provided high time resolution data, but no photon energy information, over the entire 1.1-22 keV bandwidth by measuring the time between events. The time intervals were accurate to one microsecond or 1.6 percent, whichever was greater, and so this depended on the counting rate. The TIP was also severely telemetry limited and utilized a buffer memory to attempt to cope with high counting rates. When the memory filled, no data were recorded until all the stored information was read out. This resulted in 2.56 second gaps whenever the counting rate exceeded approximately 30 counts per second, unless the crystal spectrometer was at the focus of the telescope when the corresponding numbers were 0.852 seconds and approximately 100 counts per second, respectively. The frequency of these gaps increased as the counting rate increased. Although the TIP suffered from the drawbacks described above, and the MPC received the lowest priority relative to the other instruments, many interesting results were obtained. These are highlighted in this paper. (author)