Hilbert spectroscopy of liquids for security screening

Abstract

Fast and reliable identification of bottled liquids is of great importance for security screening and, in principle, it can be done by electromagnetic measurements of dielectric permittivity functions of the liquids of concern in a frequency range, where bottles are transparent and liquids have specific dispersions. However, this frequency range is rather extended, from a few GHz to a few THz, and cannot be covered by any single conventional spectroscopy. A concept of liquid identifier, which is based on our new broadband Hilbert spectroscopy and high-Tc Josephson detectors, is presented. The identifier with a Josephson detector in a Stirling cooler will operate at the frequency range from 5 to 1000 GHz with scanning time of around 10 ms and identification time less than 1 second. The first proof-of-principle measurements of reflection spectra from various bottled liquids in the range 40-400 GHz with total scanning time of 1 second have been carried out by Hilbert spectroscopy. © 2008 Springer Science + Business Media B.V.