Cherenkov radiation is a blue glow seen mostly in research reactors (where the water pool is visible, unlike power reactors). It is caused by various charged particles traveling at a speed higher than the local 'speed of light' in water (but not the absolute speed of light in vacuum) - this can also be done in air with very energetic particles. Thus, the appearance of this phenomenon is that water around a radioactive substance glows blue. While this looks pretty, it also involves dangerous levels of radiation and thus should not be re-created at home. This project attempts to match the appearance of Cherenkov radiation without the associated ionizing radiation, by using a high-UV lamp and a transparent fluorescent blue dye in water. While the UV light is intense, it is not very visible to the eye, but the dye down-scatters the UV to blue, which gives the appearance of the water glowing blue as desired.
The attenuation of UV light will be exponential in water mixed with the dye, so it does not take much to achieve this effect (a few drops were enough for a 0.5 L bottle). With too much dye, the glow will be limited to a small range but will be more intense, wherease with too little there will be a uniform dull glow.
The construction was quite simple. The main components are a handheld UV lamp (with a tube, not LEDs), the fluorescent dye, a transparent plastic water bottle, and water. The UV lamp is taken apart so the tube can be attached independently, all the tube requires is two power wires (one at either end) from the power supply. I drilled holes to match the UV tube diameter in the bottle cap and bottom, and used hot glue to seal the tube in place. (Note, the photos show an earlier version with the UV tube fully submerged in the water - with this approach the water was seen to leak into the tube and damage it within a few days)
For the little effort that this project took, the results were quite impressive! This made a pretty nightlight and did a decent job of simulating Cherenkov radiation. It could be made more convincing with a larger water bottle and a UV filter surrounding the bottle so that the UV tube appears black (as is, it glows a dim violet color).
Adding the fluorescent dye with the lamp on, interesting patterns are observed. After the dye is mixed, an exponentially attenuated glow surroungs the lamp.
A comparison between the lamp off (left) and on (right), showing that the blue glow is bright enough to be seen even with external illumination.