IONIZINGEVENTS INSMALL DEVICE STRUCTURES

A theoretical modelisdescribed forcalculating the numberandaverageenergyofionizing eventsproducedbyx-raysinregionswithcharacteristic dimensionsrangingfrommm tofractions ofa,;m.Microdosimetrytheoryisapplied toestimatethevariance oftheeventdistribution anditisfoundthatwhen devicedimensionsareinthetLmrangeorlessthe distribution approaches lognormality. Themodel doesnotinvolve extensive calculations andusesonly readily available datatabulations. Itindicates that dosefluctuations couldbecomesignificant ifpresent trendstowardssmallerdeviceelementscontinue.