HID Shortwave UV Source

[n2ize]

I was going through my gadget/parts box today and came across an interesting little item. It's a fused quartz tube about 4 inches long. The tube is sealed at both ends and holds a vacuum and a tiny amount of mercury. It looks like the inner tube of a 400 watt mercury vapour lamp. I was thinking that with a currentl limiting resistor in series with the tube and a proper size ballast it could function as a high intensity source of shortwave UV radiation. Since the tube is quarts and not glass it will not block and of the shortwave UV. Therefore if used it would require proper shielding and enclosures to protect against eye or skin damage. But it could serve as a great UV source for an experimenter where short UV is needed. I personally have no use for it but it is something to keep in mind if I ever do any experiments requiring strong UV... I guess it would also make a powerful germicidal lamp...

[KC2UGV]

This is actually kind of good to know. Where did this part come from?

[n2ize]

This is actually kind of good to know. Where did this part come from?

If I remember correctly it came from inside a broken 400 watt mercury vapour lamp that I salvaged from a highway street lamp. Mercury vapour lamps are safe provided that when they burn the outer glass envelope is intact as it blocks the shortwave UV from exiting the lamp. But, if the outer envelope breaks and the lamp continues to operate with only the inner quartz envelope it is advised to get away from it immediately and shut it down. In fact many manufacturers incorporate a safety mechanism so if the outer glass envelope is broken the lamp will shut down to protect occupants from dangerous shortwave UV.

However, with the proper value resistor..to limit current draw and a suitable ballast the quartz tube can be made to operate, in which case its a high intensity emitter of shortwave UV. But, I emphasize extreme caution as shortwave UV can cause serious eye damage in a short time frame. When I was working for Polychrome we used a HID shortwave UV source but when in operation everything was kept enclosed so as not to expose anyone to short UV.

Another source of short UV are quartz enclosed xenon lamps provided the same precautions are taken.

[NQ6U]

Fire that mother up and get to work on your tan.

[KC2UGV]

If I remember correctly it came from inside a broken 400 watt mercury vapour lamp that I salvaged from a highway street lamp. Mercury vapour lamps are safe provided that when they burn the outer glass envelope is intact as it blocks the shortwave UV from exiting the lamp. But, if the outer envelope breaks and the lamp continues to operate with only the inner quartz envelope it is advised to get away from it immediately and shut it down. In fact many manufacturers incorporate a safety mechanism so if the outer glass envelope is broken the lamp will shut down to protect occupants from dangerous shortwave UV.

However, with the proper value resistor..to limit current draw and a suitable ballast the quartz tube can be made to operate, in which case its a high intensity emitter of shortwave UV. But, I emphasize extreme caution as shortwave UV can cause serious eye damage in a short time frame. When I was working for Polychrome we used a HID shortwave UV source but when in operation everything was kept enclosed so as not to expose anyone to short UV.

Another source of short UV are quartz enclosed xenon lamps provided the same precautions are taken.

The UV source is handy to know, because I'm working on a water filtration system. UV seems to be a bit more controllable than ozone.

[kb2vxa]

HID lamps used in street lights like HPS require a special ballast to operate rated for the lamp wattage. It contains a HV igniter circuit about 4KV to start the arc, when the gas is sufficiently ionized the reactor in series takes over. Other lamps used for indoor lighting have a tungsten filament and bi-metal switch in parallel with the mercury capsule to pre heat it and internal resistor ballast. Not knowing type or wattage makes selecting a ballast a guess at best, then there is fashioning a mount (it gets extremely hot) and enclosure, filters for wavelength, eye protection and all that makes what looks simple into quite a project.

"I guess it would also make a powerful germicidal lamp."
That's the understatement of the year. You could send it aloft in a high altitude balloon and create artificial sporadic E propagation...........

[n2ize]

HID lamps used in street lights like HPS require a special ballast to operate rated for the lamp wattage. It contains a HV igniter circuit about 4KV to start the arc, when the gas is sufficiently ionized the reactor in series takes over. Other lamps used for indoor lighting have a tungsten filament and bi-metal switch in parallel with the mercury capsule to pre heat it and internal resistor ballast. Not knowing type or wattage makes selecting a ballast a guess at best, then there is fashioning a mount (it gets extremely hot) and enclosure, filters for wavelength, eye protection and all that makes what looks simple into quite a project.

All that is known. It's a 400 watt tube. I have the appropriate ballast sitting in my garage somewhere... probably buried along with my old motorbike under 20 tons of wood and junk my Dad stacked up in the garage. Yeah, fashioning a mount is the tricky part. For shortwave UV apps the lamp would have to be operated in an enclosure to assure that the operator is not exposed to any shortwave UV radiation. This would require some sort of fan to keep the apparatus cool.

Another interesting thing I experimented during my high school days (in addition to Wilson cloud chambres and spinthariscopes and radiation detectors) was carbon arc lamps. I usually used carbon rods salvaged from zinc-carbon batteries mounted on some makeshift system so I could adjust the rods. I fed the thing with 120 VAC from the wall and used either a 1500 watt electric heater as a current limiting resistance or, sometimes a salt water bath to serve as a rheostat. The thing was hot, bright as the sun, made wonderful hissing and buzzing noises as it spit out intense light covering a huge wavelength with plenty of shortwave UV. One night I put a reflector behind it and lit up the night sky over my neighborhood. The lady down the corner was asking "what the hell is the mad scientist doing now ???". What was a real miracle is that I didn't lose my eyesight. I operated the damned thing with no protective goggles.

These days I experiment with solid state lasers but for any close up work I wear protective goggles for the particular wavelength in use. Since I was a kid I was fascinated by things that produce light.











"I guess it would also make a powerful germicidal lamp."
That's the understatement of the year. You could send it aloft in a high altitude balloon and create artificial sporadic E propagation...........

Hah ! That would be awesome,,, Sporadic E propagation on demand.