Re: Micro-cyclotron progress
Posted: Thu May 27, 2010 7:00 pm
Carl - My plan for sealing the top cover on is the same as the bottom: solder. I'll close the dee gaps with small pieces of glass and epoxy them in. With a small mirror I should be able to see any lightshows that may occur.
The ion source was originally going to be a modified nuvistor triode. Now I realize that it was not as good a choice as a simple biased hot filament. I'll start with some light bulbs of the grain of wheat variety. A separate small test system will allow me to measure emission currents. Cutting the glass bulb away shouldn't be a big problem. This same test system should also allow the design of the world's smallest hot cathode ion gauge. This would be just to keep everything to scale.
The Q of the dee sections and coil ranges from 66 at 12 MHz to 59 at 14 MHz with the top clamped on. I'm aiming for successful operation in that range. The homemade cyclotron at Houghton claims a Q of 22. The one at Rutgers claims 150. (Rutgers calculated a Q of something like 1600. Ha-ha). I saw another reference (that I can't find now) which stated that most cyclotrons operate with Qs of between about 10 and 25. Seems the values are all over the place. No measurements that I've seen so far have claimed to use a Q meter. Poor guys. Well, I'm happy with the numbers I've got for the time being.
I've tested the dees with an insulation breakdown meter and they passed with flying colors - 5 KVDC and 3.5 KVAC at 25 KHz. I don't think I'll be seeing those voltages on the dees because I'm only after a measurable beam of nano or pico amps. A clean and well defined beam plot is all l need to move me on to the new and improved machine that is now festering in my head.
As far as outgassing goes, we'll see. I don't plan on the device overheating. If outgassing really interferes (which I doubt), I can easily evaporate a layer of silicon monoxide over the exposed material in the gap.
The ion source was originally going to be a modified nuvistor triode. Now I realize that it was not as good a choice as a simple biased hot filament. I'll start with some light bulbs of the grain of wheat variety. A separate small test system will allow me to measure emission currents. Cutting the glass bulb away shouldn't be a big problem. This same test system should also allow the design of the world's smallest hot cathode ion gauge. This would be just to keep everything to scale.
The Q of the dee sections and coil ranges from 66 at 12 MHz to 59 at 14 MHz with the top clamped on. I'm aiming for successful operation in that range. The homemade cyclotron at Houghton claims a Q of 22. The one at Rutgers claims 150. (Rutgers calculated a Q of something like 1600. Ha-ha). I saw another reference (that I can't find now) which stated that most cyclotrons operate with Qs of between about 10 and 25. Seems the values are all over the place. No measurements that I've seen so far have claimed to use a Q meter. Poor guys. Well, I'm happy with the numbers I've got for the time being.
I've tested the dees with an insulation breakdown meter and they passed with flying colors - 5 KVDC and 3.5 KVAC at 25 KHz. I don't think I'll be seeing those voltages on the dees because I'm only after a measurable beam of nano or pico amps. A clean and well defined beam plot is all l need to move me on to the new and improved machine that is now festering in my head.
As far as outgassing goes, we'll see. I don't plan on the device overheating. If outgassing really interferes (which I doubt), I can easily evaporate a layer of silicon monoxide over the exposed material in the gap.