Design and development of a wide range ion chamber for reactor instrumentation

An innovative design small size ion chamber has been developed that is capable of measuring gamma radiation below 100 mR/h and reaches saturation current even at less than 200 V operating voltage for 25,900 R/h gamma background. This wide ranging capability was achieved with a special combination of electrode arrangement and guard rings placed together with the support of radiation-resistant poly ether ether ketone (PEEK) spacers. The use of machinable PEEK material removed the dead spaces and accurately defined the sensitive volume to achieve nearly ideal performance. The ion chamber is made of stainless steel with 64 cm3 sensitive volume and has 8.2 pA/100 mR/h gamma sensitivity. The chamber has been designed for reactor applications and therefore has been made rugged by separating and anchoring both the electrodes on both the ends to reduce any cantilever type vibrations with reduced noise pickup.