GB1501154A - Detection or determination of heavy ions - Google Patents

Abstract

1501154 Ion detectors COMITATO NAZIONALE PER L'ENERGIA NUCLEARE 18 April 1975 [22 April 1974] 16237/75 Heading H1K [Also in Division H5] To count and estimate the energy spectrum of heavy ions, e.g. Cf<SP>252</SP> fission products, a capacitor with thin electrode 2 on thin dielectric 1 over a conducting or semi-conducting base 3 is fed with adjustable voltage 8 below breakdown level via a protective circuit 7; ions above a threshold energy cause local breakdown registered on a counter 9 and microscopically visible (Fig. 4, not shown) holes on the electrode 2. The lower the voltage the higher the energy threshold to breakdown the dielectric; a differentiated plot of count versus voltage (Fig. 3, not shown) provides the energy spectrum. The protective circuit 7 may be a resistor >10<SP>4</SP> ohm or quenching circuit; before putting into service the device is exposed to increasing voltage via protective circuit 7 to burn out defects in dielectric 1. The electrode 2 can accept a total of some 10<SP>6</SP> holes/cm.<SP>2</SP>; when at least 10% of this level has been recorded a correction factor for loss of area can be applied (Fig. 5, not shown), inversely proportional to the capacitance. The dielectric is thickened, 4, under the connection to the electrode, e.g. by extra SiO on an SiO 2 layer 1 formed on P<SP>+</SP> Si base 3, with a thin Al electrode 2, smaller in area than the base 3 and dielectric 1 (Fig. 1, not shown), also thickened 6 to take a pin or welded connection. The electrode 2 is made negative.