If you're building your own Scintillator detector, or if you've got an old one with a crystal that's become opaque & yellow, here's what you've been looking for.
These are brand new, 1" diameter x 1" tall Sodium Iodide (Thallium Doped) Scintillation Crystals.
When doped with the element Thallium, Sodium Iodide crystals emit light when exposed to Gamma or X-Ray radiation. They are extremely sensitive and even a single Gamma ray will cause photon emission. Normally, a Photomultiplier Tube is placed on the clear part of the crystal and is used to convert the tiny flashes of light (scintillations) into electrical impulses that can be used in counting or detection circuitry.
The crystals are permanently hermetically sealed in an Aluminum can with a clear plastic cover & 'O' ring.
Overall outside dimensions are approximately 1-1/4" diameter x 1-1/2" tall.
Place on top of a Photomultiplier tube & associated circuitry and you've got a Scintillation detector.
Perfect for bringing antique Scintillators back to life.