Indirect detectors contain a layer of scintillator material, either gadolinium oxysulfide or cesium iodide, which converts the x-rays into light.
A thin gas of cesium atoms is released into the cavity where they are exposed to microwaves.
The earliest sensors were scintillation detectors, with photomultiplier tubes excited by (typically) cesium iodide crystals.
Later rubidium beam and cesium beam clocks were used.
The metallic titanium provides reducing conditions during ceramic synthesis and helps decrease volatilisation of radioactive cesium.
Frlez et al. recently reported using tomographic methods to track the passage of cosmic rays muons through cesium iodide crystals for quality control purposes.
The source is typically the radioactive isotope cesium-137, with a half-life of about 30 years.
There will possibly be a lot of unlocked cesium available in the soil for uptake this spring.
