You are bidding on a quantity of One (1) Scintillation Crystal Detector made of Bismuth Germanate, commonly called BGO for short.
The exact crystal type is Bi4Ge3O12 or sometimes known as BGO12. Each BGO crystal is 30mm x 12mm x 6mm. The end faces are 12mm by 6mm, and at least one end is polished (often both ends), the sides are an un-polished matte finish, overall length of each crystal is 30mm.
The purpose of a scintillation crystal such as BGO is to convert radiation into a visible light. When radiation such as a gamma-ray passes through the crystal it scintillates, meaning it gives off a tiny burst of light. The light is too dim and too brief to detect without amplfying it first, so normally a Photo-Multiplier Tube (PMT) is used to amplify the burst of light into an electrical pulse that is used to trigger a geiger counter or other counting devices.
For some background information on gamma-ray detecytors and scintillation check the nasa website www.nasa.gov and search on BGO, also check this link:
All the crystals I offer are clean and in very good condition with no large chips. Most of the crystals have some minor flaking or roughness on the edges and corners (see pictures below) but this commonly occurs during manufacturing and should not have any measurable effect on performance.
Will ship by USPS First Class mail to any address in United States for $1.95 (estimated delivery time is about 3 business days), or worldwide by USPS First Class International Mail for $4.95 USD (estimated delivery time is about 6 to 10 business days).
The picture below shows how the BGO crystal will actually produce a blue glow while it is being directly hit by a constant radiation beam from an X-ray machine. Once the radiation source is removed the BGO stops scintillating (glowing), the crystal does not become radio-active. This is not the normal application for BGO crystals, its only to help illustrate their scintillation properties. The BGO crystal by itself will not make a good indicator of unsafe levels of radiation in the enviroment. It is possible that only an X-ray beam will produce this eye visible glow, so plan to use a PMT to detect radiation.
All pictures shown are representative, all my crystals have the same specs and quality, but exact item shipped will have minor cosmetic differences.
I am also selling separately square faced Photo-Multiplier Tubes ( PMT's ) that work well when coupled with these scintillation crystals. I have other listings that include both the PMT and BGO's combined at a lower price and shipping. For more information see my other listings.
Below is some information on the properties and specifications of BGO:
Bismuth Germanate, also called BGO, is a high density scintillation material. Due to the high atomic number of bismuth (83) and its high density, BGO is a very efficient Gamma-ray absorber. Because of its high effective Z value, the photofraction for Gamma-ray absorption is high, which results in a very good photo-peak to Compton ratio. The scintillation light can be detected with standard photomultiplier tubes. The scintillation intensity of Bismuth Germanate is a strong function of the temperature. The decay time of BGO is about 300 ns at room temperature, which is comparable to that of NaI(Tl). However, the afterglow is much lower, typically about 0.005% after 3 ms.
BGO is relatively hard, rugged, non-hygroscopic crystal which does not cleave. The material does not show any significant self absorption of the scintillation light. The crystal housing can be kept simple since no hermetic air-tight sealing is required. BGO can be machined to various shapes and geometries. BGO scintillation crystals are used in applications where a high photofraction is required (as in PET scanners) or because of its high density (as in Compton suppression spectrometers).
Summary of Properties
Density; 7.13 g/cm3
Cleavage plane -- none
Hardness; 5 Mho
Wavelength of emission maximum; 480 nm
Lower wavelength cutoff; 320 nm
Refractive index at emission maximum; 2.15
Primary decay time; 300 ns
Afterglow (after 3ms); 0.005 %
Light yield; 8 - 10 x 103 photons/MeV
NOTE: Some of my customers in Germany and Italy have experienced very long delays at their local customs office. If you have not received your package after 2 weeks you should inquire at your local post office to see if the package is being held in customs, this can help speed up the release.