Merry Christmas! ^^So... I woke up at 2am in the morning to set up the Christmas lights... i.e. the preliminary test for the thermionic heater proton source. The purpose of the test was to make sure that I have the correct current/filament size/resistance calculations, and that the DC supply is working as expected, and perhaps attempt to ionize atmospheric air (nitrogen).
The experiments that ensued were plenty of fun and excitement, because my calculations were correct. I muted the audio on the video, since it isn't very entertaining to hear our triumphant "Woahhhhh!" and fast-spoken scientific speculations, or our relatively nerdy Christmas celebrations.
The experiments that ensued were plenty of fun and excitement, because my calculations were correct. I muted the audio on the video, since it isn't very entertaining to hear our triumphant "Woahhhhh!" and fast-spoken scientific speculations, or our relatively nerdy Christmas celebrations.
Fernando and I are rather... random people... so you see, I didn't prepare a 'ground plate' for the electrons to be directed towards. I decided to take apart an old CPU case, clean it off as much dust as I can with a tissue (you'll see from the pics that it's still very dirty) and find a convenient spot to hook up the plate to the ground.
Makeshift ground.I made 3 lengths of wire, 2cm, 10cm, and 30cm - which makes about 0.536 ohms, 2.68 ohms and 8 ohms. The first two were to test the hypothesis if the resistance would reach a 'breakdown' or respond infinitely to the current (increase its resistance to suppress the current), thereby preventing the wire from vaporizing. We could just dump an arbitrarily high current on the wire if it doesn't vaporize, you see. The second also tests a suggestion from the handbook. (The handbook suggested dividing the recommended current by half if we were using a filament source of an equal length as would have been a straight wire... didn't sound right to me.)
The third, by my calculation, would sustain a little higher than 1144K of temperature on the wire for a long period of operation.
The third, by my calculation, would sustain a little higher than 1144K of temperature on the wire for a long period of operation.
From my previous post, the wire hasdiameter 0.26mm (AWG30), resistance 26.8 ohm/m.
Coiling a filament with a test pen.
This experiment is obviously ill-fated. I calculated 45A of current running through the wire.
Another ill-fated experiment, with 9.0A of current.
8 ohms, 3A with a 30cm filament coil.
Color of glow in white light.
Color of glow in the dark. Green LED indicates operation of the DC supply.Note how the connectors have melted pretty badly. It was necessary to ventilate the place with a fan. Eventually, we stretched out the wire and were able to keep the wire distant enough from the plastic to prevent the melting, while we watched the wire in action for 7 minutes. I halted the experiment after 7 minutes because the wire was clearly going to work for a very, very long time. The fan of the DC supply didn't start running either... the 72W load isn't going to cause major heating issues.
The wire acted very interestingly... once it reached a glowing temperature, it would go brighter, then dimmer, repeated in a cycle.
The wire acted very interestingly... once it reached a glowing temperature, it would go brighter, then dimmer, repeated in a cycle.
Final experiment with the wire stretched out to test the duration of operation.The tests were particularly successful. The suggested currents on handbooks are working as expected, 30cm of wire is just nice to make a filament fitting the 2cm gap (if I recall correctly) on the base plate. The wire would clearly operate for a long period of time - much longer (7++min) than we expect the beam to run (~1min). We didn't have time and the resources to set it up in negative bias.
Only thing is, I need to test for the ionization of nitrogen and apply a negative voltage this time. I think I need a DC-DC converter to apply a negative voltage across the wire, and a photoelectric sensor to test for UV emissions. I should also hook up the filament with a multimeter that has a temperature gauge to see if we're getting the expected temperatures. It would be interesting to observe the behaviour at the point at which it alternately glows brighter and dimmer.
Only thing is, I need to test for the ionization of nitrogen and apply a negative voltage this time. I think I need a DC-DC converter to apply a negative voltage across the wire, and a photoelectric sensor to test for UV emissions. I should also hook up the filament with a multimeter that has a temperature gauge to see if we're getting the expected temperatures. It would be interesting to observe the behaviour at the point at which it alternately glows brighter and dimmer.
******
I posted yesterday about "specing up" on QFT. I'm currently using Radovanovic's Problem Book in Quantum Mechanics, Peskin & Schroeder's Introduction to QFT and Zee's QFT in a Nutshell. I have Weinberg's 3 volumes on QFT, but I know I won't have that level of mathematics in a short time.
Anyway, Anthony Zee's treatment is DAMN FUN...
[On the double slit experiment]
Suddenly, a very bright student, let us call him Feynman, asked... "...What if I put a screen and drill an infinite number of holes in it so that the screen is no longer there?"
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