Radiation portal monitor

They provide limited information on energy of detected photons, and as a result, they were criticized for their inability to distinguish gamma rays originating from nuclear sources from gamma rays originating from a large variety of benign cargo types that naturally emit radioactivity, including cat litter, granite, porcelain, stoneware, bananas etc.

[7] In attempt to reduce the high nuisance alarm rates of first generation RPMs, the Advanced Spectroscopic Portal (ASP) program was called into life.

These devices, having better energy resolution than PVT, were supposed to reduce nuisance alarm rates by distinguishing threats from benign sources on the basis of the detected gamma radiation spectra.

[8] The ASP program was canceled in 2011[9] after continued problems, including a high rate of false positives and difficulty maintaining stable operation.

HPGe, having significantly better energy resolution than NaI(Tl), allows rather precise measurement of the isotopes contributing to gamma ray spectra.

However, due to very high costs and major constraints such as cryo-cooling requirements, US government support for HPGe based portal monitors was dropped.

Utilizing recoil nuclei following neutron scatter events, natural helium glows (scintillates), allowing photomultipliers (e.g. SiPMs) to produce an electrical signal.

As the name suggests, an RDD aims at dispersing radioactive material over an area, causing high cleanup costs, psychological, and economic damage.

Causes of nuisance alarms can be broken up into several large categories: This article relates primarily to RPMs deployed for screening trucks at ports of entry.

Over 1400 RPMs are deployed at US borders and a similar number at foreign locations for the purpose of interdicting illicit radiological and nuclear material.