Spherical ion chamber under pressure

The spherical ion chamber under pressure is designed for the secondary calibration of alpha, beta and gamma radioactive sources. Very low activity of such sources can be measured by placing them inside the ion chamber and using air or krypton and xenon gases up to 10 Atm. The ion chamber is made by two hemispherical metallic electrodes polarized with 100 - 500 V d.c. and a special inner collecting electrode having the radioactive source placed in a central position. The main insulation material is Teflon. The sphere diameter is 200 mm. The pressure control is made by an external proper instrument. The tightness of chamber is good enough: at 5 atm. pressure during 6 days the pressure loose is 0.15 bar. Measurements made for several experimental studies were performed using a complete computing chain: Keithley 617 Programmable Electrometer, DTK Computer (486 type), Test Point and IEEE-488 Interface. (authors)