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UltravioletPhotography

Last and final 185nm attempt


dabateman

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Warnings and information:

Don't image in UVC, it will not get you much. DO NOT BUY a mercury bulb that is clear for UV photography. YOU will most likely hurt your self.

Two types of germicidal clear UVC bulbs are available and outside of looking a glowing rocks, Neither should be purchased for looking at things.

Most germicidal bulbs will have titanium dopped glass, called ozone free germicidal bulbs. The Ti dopping cuts off all wavelengths below 220nm and they do produce very little ozone. But you can still smell some, so its still dangerous. These are very monochrome 254nm, but do have some other mercury wavelengths, so you can see some light. BUT NEVER LOOK AT ONE!!!

Ozone bulbs or 185nm bulbs are clear, not always marked as Ozone bulbs and will get hotter than the other type of germicidal bulb and is intended to kill things.

 

The Pentax UAT lens manual says the coating is rated from 220nm to 1000nm. I have a feeling its cutting off wave lengths below that 220nm specification.

 

The KSS100B 60mm f3.5 C-mount quartz macro lens indicates a minimum wavelength of 230nm in its specification sheet. I think that is real and its cutting off at that wavelength.

 

The Sirchie KRIMESITE Imager has a S20 (500S or 500U multialkali) photocathode by Hamamatsu with 180nm to 700nm range. The QE at 185 is about 5%, peak is 26% at 254nm and drops down to 2% at 700nm. This passes electrons to a P22 phosphor that emits 530nm light to be viewed or photographed.

 

Remember that QE is % of light captured. So if I give it 100 photons of 185nm light, then it will only see 5 of those 100 photons.

 

Ozone light is high temperature and needs about 15 to 30 minutes to warm up to be at medium pressure, for mostly 185nm. That is not safe to be around. So I ran it short and will have mix of 254nm and 185nm light as it was mostly at low pressure.

 

 

The filter I have is not great but is 190bp20 filter with following spectra:

post-188-0-95640700-1579338300.jpg post-188-0-00904800-1579338314.jpg

 

For this test I first looked at 99% IPA next to Acetone. IPA has an absorbance at 205nm and Acetone is around 280nm.

 

KSS 60mm lens with UVC imager and 190bp20:

post-188-0-37787900-1579338508.jpg

 

See clear IPA, and dark acetone. It was noisy so not much lighting hitting the photocathode, which has 5% QE at 185nm and 26% at 254nm.

 

Testing Pentax UAT lens in same setup:

post-188-0-02388800-1579338701.jpg

 

Again nothing good. Then I thought about the lens specification and that it might be filtering out the wavelength that no one in their right mind should be imaging. So I tested a Pinhole lens.

 

Pinhole pro, with 0.25 pinhole with 190bp20 filter and same dangerous Ozone light.

This is Water (absorbance starting to come back 190nm) next to 99% IPA (absorbance start 205nm). To get better contrast I placed a white virgin PTFE board behind to help reflect some of that supper dangerous light.

post-188-0-14316900-1579338715.jpg

 

In the pinhole image you can first see that its a horible image and imaging at 185nm will be a waste of time. However, you can see that the 99% IPA on the right is darker than the tap water on the left!

 

Excellent, Now I know its just barley possible to image at 185nm, PLEASE no one try this.

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I wander how low can we get in UV? Can we reach 150 nm in air? With CaF2 you can reach (not very easily but you can) ~120 nm. You have to remove air with a vacuum pump at that point. Would it be possible to see black air inside a container?

 

At 100 nm nothing should be transparent in normal thicknesses, but vacuum (pinhole) is still transparent of course. You would see black, nothing bright, maybe not very reflective metals. A truly alien world. Then, at even shorter waves, down to X-Rays wavelengths, there is just mystery.

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I wander how low can we get in UV? Can we reach 150 nm in air? With CaF2 you can reach (not very easily but you can) ~120 nm. You have to remove air with a vacuum pump at that point. Would it be possible to see black air inside a container?

 

At 100 nm nothing should be transparent in normal thicknesses, but vacuum (pinhole) is still transparent of course. You would see black, nothing bright, maybe not very reflective metals. A truly alien world. Then, at even shorter waves, down to X-Rays wavelengths, there is just mystery.

 

I am at the limit here. Water has absorption coming back at 190nm. If I were imaging at 185nm, the water would be darkish too. However, only the IPA is dark, so I am between 190nm and 205nm.

That is the dry air winter limit.

 

I will not test in a vacuum.

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To go lower than 185 nm you would need excimer lamps or something like that, anyway.

 

I know that this experiments are crazy dangerous if you don't know exactly what you are doing (you are dealing with 6.7 eV photons, and that's a LOT), but I like them. It would be interesting to see how things look like in that "black hole" region. Yes, probably black and not much else, but think about it. Practically nobody has ever seen into that mysterious, I would say almost forgotten band (for good reasons). Only NASA has imaged the Sun at wavelengths in that range, for example at 30.4 nm.

 

Anyway reaching below 200 nm is still a notable accomplishment.

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Yes, this is nice work! I think you need to build a contained rig that has an ozone exhaust to outdoors and isolated from the room air.
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Fascinating results David!

 

The warning on my Verilux 253.7nm sanitizer, is enough to scare me away from extreme UV photography.

 

"... disrupts DNA structure and either kills it or renders it unable to reproduce - and therefore harmless. As a result, the use of UVC light to sanitize and kill germs has many applications."

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Fascinating results David!

 

The warning on my Verilux 253.7nm sanitizer, is enough to scare me away from extreme UV photography.

 

"... disrupts DNA structure and either kills it or renders it unable to reproduce - and therefore harmless. As a result, the use of UVC light to sanitize and kill germs has many applications."

Are there any risks of creating superbugs with that lamp? It should also induce mutations.
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Are there any risks of creating superbugs with that lamp? It should also induce mutations.

 

If any earth-bound virus could survive and mutate, we are indeed in trouble. My toothbrush sanitizer hasn't developed any superbugs, and seems to prevent any traces of mold from forming.

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To go lower than 185 nm you would need excimer lamps or something like that, anyway.

 

I know that this experiments are crazy dangerous if you don't know exactly what you are doing (you are dealing with 6.7 eV photons, and that's a LOT), but I like them. It would be interesting to see how things look like in that "black hole" region. Yes, probably black and not much else, but think about it. Practically nobody has ever seen into that mysterious, I would say almost forgotten band (for good reasons). Only NASA has imaged the Sun at wavelengths in that range, for example at 30.4 nm.

 

Anyway reaching below 200 nm is still a notable accomplishment.

 

Nope I had an image of my teeth taken using 70nm x-rays. So you can go lower with digital detctors. You just need to be very careful.

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Nope I had an image of my teeth taken using 70nm x-rays. So you can go lower with digital detctors. You just need to be very careful.

Shouldn't air be opaque there? Not saying you are wrong, but maybe you were referring to 70 KeV hard X-Rays?
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Yeah, something sounds odd about that. 70nm is EUV, not x-rays. I think Stefano is probably right. 70 keV is pretty typical for oral x-rays. 70 keV = 0.017 nm.
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Bill De Jager
Thanks for investigating this David so we don't have to. I considered getting a 254nm lamp long ago but decided it was just too risky seeing how absent-minded I am.
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