Sry for asking a photochemistry question here but I couldn't find an AAC chemistry forum

Anywho since HP the x-ray guru is gone fishing I hope someone here can help me?
After total exposure of around 100,000 Gy (extrapolated from electrostatic dosimeter readings) to 120 kev energy, initially clear pyrex is almost totally opaque to optical wavelengths b/c of solarization. I know it's a well known phenomenon but I can't find a resource that explains the actual chemical changes? If anyone here has technical details or knows where I can find them I'll be grateful for your sharing!

 

@GopherT and
@jpanhalt
are your likely candidates for this one.

 

It's an effect we see in high energy system glass view-ports.

https://www.orau.org/ptp/collection/xraytubescoolidge/coolidgeinformation.htm

With use, the clear colorless glass of an x-ray tube can become colored. Such a color change is either due to the absorption of radiation energy, or the deposition of tungsten on the inside surface of the glass. The absorption of x-ray energy by electrons in the glass promotes them to a higher energy state (the conduction band). The now mobile electrons move to positively charged impurities in the glass where they become trapped. Since these trapped electrons are at a higher energy level than they were prior to the exposure to radiation, the absorption spectrum and the color of the glass is affected.The resulting color depends on the type of the impurities: the softer glass of the older tubes (e.g., 1920s vintage) tended to turn purple, while the harder glass of the more modern tubes (e.g., post 1930) tended to take on an amber color.

https://e-reports-ext.llnl.gov/pdf/243450.pdf

 

JC, HP was all through this on her thread which you said you totally read through It's all to do with farbe centers cuz of ions in the xtal lattice. For interesting experiment you can heat the glass to make it clear again

PS JC I know glass isn't crystalline in normal sense but it contains suspended crystals so don't go all nitpicky on me!

 

It's an effect we see in high energy system glass view-ports.

https://www.orau.org/ptp/collection/xraytubescoolidge/coolidgeinformation.htm


https://e-reports-ext.llnl.gov/pdf/243450.pdf

Nsaspook thanks! But I know JC's setup. He's not talking about the tube envelope glass. It's his transparency plate on table to adjust collimator. I know cuz he was complaining about expense of replacing it last week

 

JC, HP was all through this on her thread which you said you totally read through

Yo Aleph! I searched the whole site. Hp only mentions solarization twice in passing on two different threads but not on EHT design thread So it must have been among the, as she termed it, "extraneous" material she deleted from the tutorial post?

It's all to do with farbe centers cuz of ions in the xtal lattice. For interesting experiment you can heat the glass to make it clear again
PS JC I know glass isn't crystalline in normal sense but it contains suspended crystals so don't go all nitpicky on me!

Thankie thankie!

For interesting experiment you can heat the glass to make it clear again

To what temp? I could save $600 a go if I can do it without deforming the plate!

 

Not my area of photochemistry, but from what I understand of farbe centers, annealing temperature (1050°F) should work, maybe lower. I would start at, say 600°F and see if that makes any change. When annealing glass, as when glassblowing, you can often get sufficient stress relief well below dull red.

When you say you do not want distortion, how much is acceptable? Is this an optically flat window? If so, you might need a flat to repolish it after annealing.

John

 

Not my area of photochemistry, but from what I understand of farbe centers, annealing temperature (1050°F) should work, maybe lower. I would start at, say 600°F and see if that makes any change. When annealing glass, as when glassblowing, you can often get sufficient stress relief well below dull red.

jpanhalt thanks! Is nice to know cuz I thought it would have to be heated to incandescence (like 1500F) for sure!

When you say you do not want distortion, how much is acceptable? Is this an optically flat window? If so, you might need a flat to repolish it after annealing.

I know the machine he's talking about, it's just a pane with frosted marks to cast calibrated shadows from visable light from collimator. I don't know if it's tempered or not but now that I think about it heating tempered glass could be interesting but I hope not as exciting as demolition of prestressed concrete!

@Jazz2C Try breaking one of the junked out plates! If it breaks like window that's good but if it breaks into little cubes lake autoglass except windshield then it's tempered so be careful heating it and know that even if you can do it without shattering, it will lose its temper so try not to lose yours!

I could save $600 a go if I can do it without deforming the plate!

JC you are worse cheapskate than me! If you can get direct replacement for $600 why muck around with reusing solarized plate?
If you are insisting on being cheap you can just etch thick window glass with HF solution to get graduations but be careful with enchant! If low PH doesn't get you, hypocalcaemia will!

 

TNX to everyone for the replies!

When you say you do not want distortion, how much is acceptable? Is this an optically flat window?

Actually minor refractive inclusions wouldn't matter, like Aleph says it's really nothing more than a transparency for optical light (wavelength centered around 550 nm)

I don't know if it's tempered or not but now that I think about it heating tempered glass could be interesting but I hope not as exciting as demolition of prestressed concrete!

@Jazz2C Try breaking one of the junked out plates! If it breaks like window that's good but if it breaks into little cubes lake autoglass except windshield then it's tempered

Glad to know its disruption pattern is very similar to that of a residential window pane

JC you are worse cheapskate than me! If you can get direct replacement for $600 why muck around with reusing solarized plate?

I know, you're right But student that I am even $600 is worth saving

you can just etch thick window glass with HF solution to get graduations but be careful with enchant! If low PH doesn't get you, hypocalcaemia will!

IMNSHO HF is a bad agent to be totally avoided outside the lab!

 

IMNSHO HF is a bad agent to be totally avoided outside the lab!

Yup!