Year
2010
Abstract
Proportional counters (PCs) are a type of gas-filled radiation detection device capable of distinguishing between a wide range of radiation types and energies. In this application, however, these devices are limited by high power consumption and high bias potentials required to operate in the proportional detection regime. Previous work performed with a single carbon nanotube (CNT) anode has shown that nanoscale-based PCs can operate at bias potentials of ~10 V rather than the 1000 V range required for traditional PCs. “Proof of concept” experiments with a single CNT as the anode exhibit a small detection volume and consequently required long count times (24 hrs). To make this a practical detector technology (i.e., decrease the count time), the effective detection volume has to be increased. Experimental data and electric field modeling show that if the pitch (spacing between individual nanotubes) of the arrays is too small, the electric field of the individual nanostructure will collapse and the nanoscale array will behaved as a single macro-scale field with the associated high bias potential required to reach the proportional region. Electric-field modeling of the influence of nanostructure pitch on the electric field distribution of these arrays predicted that a pitch of about two-and-a-half times the height of the nanostructure was required to retain the nanoscale electric field. In this work, we report on the fabrication and electrical property testing of nanoscale arrays with a range of controlled pitches. Arrays of differing composition (VACNFs and Si posts) and synthesis routes were produced and characterized. As an indirect measurement of electric field strength, we conducted high voltage breakdown studies under Ar and He atmospheres. The results qualitatively show that the electric field strength associated with the nanoscale arrays is higher than that of a control, particularly at pitches above two-and-a-half times the nanostructure height, as predicted by electric field modeling.