Electronics > Projects, Designs, and Technical Stuff
Electron gun - salvage or build
LaserSteve:
Binding is an artform. There are some videos of tube manufacturing on YouTube that cover the process, search for "Phosphor Settling"
Silicate Solutions, Acetate Solutions, often with a buffer solution floating on top to mitigate turbulence. , then usually some means for decanting the buffer and un-used phosphor from the CRT bottle. usually by mechanically tilting very slowly to avoid any turbulence. In your case you probably can do it separate from inside your final structure.
The US Patent server is your friend on that one..
You then have to decide if you want your phosphor to be able to store charge, or add a conductive layer on top of it. (Aluminizing) Charge storage can be bad as it deflects the beam from a charged spot. Simple tubes generally do not have the bleed layer.
BTW, the black fluid stuff in the videos for conduction is called "Aquadag".
Steve
wizard69:
I'm laughing now because we run a vacuum process at about 250 mtorr. To think I thought that was high vacuum
--- Quote from: BreakingOhmsLaw on May 22, 2020, 10:52:22 am ---Hi,
Used to work in a Philips picture tube factory.
Evacuating CRT was done like this:
Step 1: Piston Pump to about 50mbar.
Step 2: Turbomolecular pump like the one you have in your setup.
Step 3: Diffusion Pump while heating the CRT to 200C. After that, CRT was sealed.
Step 4: Barium getter pill evaporated with an external RF Field.
Heating the CRT was essential to achieve full vacuum, otherwise many molecules stick to the internal parts.
--- End quote ---
ChristofferB:
--- Quote from: 1sciguy on May 22, 2020, 04:50:08 pm ---450kV power supply for my electron gun at work. I designed the pressure vessel so it can be filled with SF6 insulating gas. We use GaAs photocathodes that are laser driven. I designed the laser system. 50ps pulses at 500 MHz by gain-switching laser diodes and then amplifying with fiber lasers. I actually combined three of these lasers with 120 degree phase shift for a 1.5Ghz pulse train. This was all at a National Lab and I have retired. I would not attempt such a project on my own without serious funds. Photocathodes are cool because all you have to do is bias your cathode at HV and hit it with a laser to get the electrons off. Of course there is chemistry involved to process the cathode in vacuum to lower the work function so it will spit off electrons based on light energy striking it. Thermionic guns are pretty simple, so yes, you could easily take these items from a CRT if you have a means to float your drive electronics at high voltage.
--- End quote ---
Whoa that looks impressive!
I did read about laser electron sources, but since I haven't worked with lasers, I wanted to avoid nesting projects too deep.
ChristofferB:
--- Quote from: LaserSteve on May 22, 2020, 05:00:53 pm ---Binding is an artform. There are some videos of tube manufacturing on YouTube that cover the process, search for "Phosphor Settling"
Silicate Solutions, Acetate Solutions, often with a buffer solution floating on top to mitigate turbulence. , then usually some means for decanting the buffer and un-used phosphor from the CRT bottle. usually by mechanically tilting very slowly to avoid any turbulence. In your case you probably can do it separate from inside your final structure.
The US Patent server is your friend on that one..
You then have to decide if you want your phosphor to be able to store charge, or add a conductive layer on top of it. (Aluminizing) Charge storage can be bad as it deflects the beam from a charged spot. Simple tubes generally do not have the bleed layer.
BTW, the black fluid stuff in the videos for conduction is called "Aquadag".
Steve
--- End quote ---
If I were to coat an aluminium hemisphere with a phosphor (as used in LEED systems) wouldn't that issue solve itself?
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