Gamma-ray Spectroscopy with DDC-10
The DDC-10 can be used as a 10-input multichannel analyzer with NaI(Tl) and other scintilation detectors performing environmental monitoring or hazardous substance detection. Several examples of gamma-ray spectra collected with the DDC-10 and an NaI(Tl) detector are presented below.
Gas Lantern Mantle with Thorium
Incandescent gas mantles (Welsbach mantles) are still used for portable camping lanterns. Until a few years ago the mantles were made by saturating a cotton fabric with thorium oxide to take advantage of its candoluminescence. Unfortunately, both thorium and its decay products are slightly radioactive, what led to replacing thorium with slightly less effective rare earth in more recent mantles. The old thorium-based mantles are still used in many Physics labs for testing detectors.
We measured the gamma ray spectrum emitted by a thorium-based mantle with the NaI(Tl) detector (Solon Technologies 6S4/2, diameter 1.5") connected to DDC-10. The screen shot shows the online web display of the measurement.
The gamma ray energies shown in the following plot were identified according to the list of gamma rays emitted by 232-Th and its decay products. Please pay attention to a large dynamic range of this measurement, from X-rays all the way up to 3 MeV.
During early 1900's, watch, clock and other instrument dials were painted with radioluminescent paint containing radium. The last-century radium dials are increasingly difficult to find. We were lucky enough to come across a wrist watch from early 1950's, which was presented to one of our family members upon his graduation. The watch has lost its luminescence, but the radium in its dial is still active. We measured the gamma ray spectrum emitted by the watch with the same NaI(Tl) detector (Solon Technologies 6S4/2, diameter 1.5") connected to DDC-10. The gamma ray energies were identified according to the list of gamma rays emitted by 226-Ra and its decay products.
It is important to realize that low-activity measurements are always performed in the presence of the environmental radiation background due to trace radioactive elements such as potassium-40 produced in upper atmosphere by cosmic-ray interactions. We measured the gamma ray spectrum with the NaI(Tl) detector (Solon Technologies 6S4/2, diameter 1.5") connected to DDC-10, without any radioactive source present in the vicinity of the detector. The gamma ray line at 1.46 MeV, which is a characteristic of 40K decay, was clearly seen after one hour measurement.
We hope that we have convinced the reader that our DDC-10 instrument is an invaluable tool for performing radiation measurements with Nai(Tl) and other scintillation detectors. The instrument is available for purchase. Please inquire by sending an e-mail from the contact page.