Abstract: This technical report consists of series of drawings of the instrument with the following explanation. The modification of the Simpson Methane flow proportional counter consists of a means for inserting and replacing samples into the chamber through an air-lock device which avoids the introduction of even a small quantity of air into the active volume of the chamber. This is accompanied by sweeping out the small volume of the air-lock containing the sample with methane gas before the sample is introduced into the chamber -- this sweeping out requiring only a few seconds. The mechanical construction is somewhat simplified over that employed in the Simpson counter design, although the electrical and counting characteristics are essentially duplicates of those employed in the Simpson version. Voltage plateaus about 400 volts long, flat within 1% per 100 volts are obtained with the counter, with the operating point at about 2500 volts for methane at one atmosphere pressure. A plateau extending over a range of about 40% variation in amplification factor is obtained. Standard samples have been checked to standard deviation of +/-0.3% over a period of one year. The counter is rather gas-tight and is ready for use within about ten minutes …

Technical report which includes a description of scaling action in a Higinbotham circuit, of operation of the output circuit, of operation of the regulated high voltage supply. Acceptance and performance specifications are given. also included are cuts showing the bottom and top view of a scaler of this type. The scaling circuit diagram and major parts list is attached. To facilitate testing, the circuit of a satisfactory pulse generator is included together with a cathode - follower.