sion of better than two percent, including drift effects, over a three-week period. The completed detector head, including ion chamber and electronics, was encapsulated in Hysol 6020 casting resin. A typical calibration curve for these detectors is given in Figure 2.2. 2.2.2 Residual Instrument System Recorder. The two-channel recorder used with this system consisted of an Esterline-Angus-chart drive to supply the time base and 10 ® io * te EF 0% he @ ° x o de 0? = ” ° a - tas o (10 : E = 7 February o 3 D A: 2! February \ ram = 8 Febru ary 107? | 107! 10 102 Frequency, pulse/min Figure 2.2 Graph showing a typical calibration curve for the Conrad detectors. These detectors were calibrated with the 200-curie Co® source and the 250-kv X-ray generatcr. two electric styluses writing on Teledeltos paper charts. The output from the detector head was fed through an amplifier directly to Stylus No. 1, which produced a mark for each detector-output pulse. In addition, the detector output was fed to a scale-of-1li counter, thence tu Stylus No. 2. Thus, Stylus No. 2 produced one mark for each 11 output pulses from the detectcr. In this manner, a chart speed siow enough for the required five-day operating period could be used while maintaing resolution of the fastest anticipated pulse-repetition rate. In operation, the record from Stylus No. 1 was used until 21