Xenon-filled ionization counters utilizing a virtual Frisch grid

A new design for a compact and rugged high- pressure xenon-fill ionization detector is being explored at Constellation Technology Corporation (Constellation). The basic design approach is to use a detector geometry that eliminates the effect of the induced charge from uncollected ions without using any shielding mesh. This approach is called a virtual grid ionization chamber and can be employed in a variety of different configurations. We have built several prototypes of slightly different design, and some have yielded a FWHM resolution of 2% at 662 keV. These prototypes, being small, are best suited for use in hand held nuclear identifiers and Unmanned Aerial Vehicles (UAVs). However, this technology easily lends itself to being scaled up to large meter-sized panels that will provide high resolution, large area, and position sensitivity on a scale of 1 cm or better. This paper discusses Constellation´s current status of this virtual Frisch grid technology and plans for the future.