October 17, 1951

• a. The chambers used by Brookhaven in the area monitoring are bakelite wall
  air chambers with a volume of 6.25 liters. These are sealed chambers
  filled with dry air.
•  
• b. The collecting voltage is 390 volts.
•  
• c. Teflon or fluorothene insulation is recommended between the guard ring
  and the collecting electrode.
•  
• d. The rate of drift method is used at Brookhaven with one charge cycle
  occurring every 30 or 40 minutes. The number of charging cycles is
  recorded photographically and graphically on the Brown recorder chart.
•  
• e. The constant deflection seems feasible if automatic periodic zero checks
  are made.
•  
• f. There is no provision for automatic calibration for any of the detectors
  used in the Brookhaven area monitoring.
•  
• g. Details of the ionization chamber-electrometer assembly are described
  in the Area Survey Manual BNL-I-8 which Mr. Weiss has given us.