Remote sensing of an elevated level of background ionization with a 1 THz, 1 kW Gyro-BWO

One application of the THz gyro- BWO under development at the University of Maryland is remote sensing of an elevated level of background ionization in air at NTP; such an elevated level might be found in the vicinity of radioactive material. The aim of the gyro-BWO development is to produce $\sim $1 kW of THz power in a 100 microsecond pulse. When such radiation is focused to a spot of cross-sectional area $\sim \lambda ^{2}$, the electric field would be sufficient to break down the air if the background ionization level were sufficiently elevated. With the time to breakdown dependent on background electron density n$_{o}$, an elevated value of n$_{o}$ will manifest itself by causing a shortening of the transmitted or reflected THz pulse. The range and sensitivity of such a detection scheme will be discussed.