2nd Austrian Fusor in progress ...

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Werner Engel
Posts: 145
Joined: Sun Aug 18, 2013 11:51 am
Real name: Werner Engel
Location: Vienna, Austria
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2nd Austrian Fusor in progress ...

Post by Werner Engel »

Hi fusioneers!
My new roughing pump (Edwards RV8) finally motivated me to change from my old glass based chamber (see my avatar) to the new steel chamber with the 75kV HV feedthrough. The old Pfeiffer DUO-08B was too loud to operate in my small office room. I decided to use mostly ISO-K instead of CF - this made it possible to build the new chamber almost in one day. I’m very proud of the mounting system I used (see the picture). The chamber “hangs” on 3 points and can be adjusted in height.

The rouging pump part consists of a foreline trap and a magnetic valve to separate the pump from the turbo. I’m using two PKR251 to measure roughing pressure and chamber pressure. I also introduced a metal mesh between the chamber and the turbo and the PKR251 to avoid any unwanted plasma discharges due to different voltage levels inside.
For venting I use a small magnetic valve which is controlled by the DCU of the turbo pump. Venting gas is pure and dry nitrogen (99.99999%) coming from a special pressure reducing valve. Actually that’s not working as planned, as the valve tends to overshoot the final venting pressure at the end of the automated venting cycle. The viewports are not allowed to be exposed to overpressure – so until now I have to manually end the venting procedure and always keep an eye on this.

You can also see that the mass flow controller is not yet connected to the gas manifold I built. I adjusted it to a target of 10e-9mbar which closes it completely.
Today I added some bakeout-heating-wires and aluminum foil isolation to heat the chamber up to 60°C. I used a JUMO PID controller which works fine after activating the self-optimizing algorithm. This made it possible to obey the 2K/min ramp up speed. Actually I used 0.5K/min just to be sure not to destroy the viewports. There are two of them (size DN100) in 90° angle so I can see the grid from two sides.

The first tests (last week) showed that everything seems to be tight. So today I connected some “mild” HV to the electrode (Tungsten-Rhenium) to speed up the cleaning process. Having switched on the roughing pump I got some very nice pictures in the higher pressure regime. After adding the turbo the HV was not high enough anymore. But I saw my fist ions cleaning the inner side of the chamber – that was great!
Currently I’m at 1.5 x10e-6 mbar (with 1.1x10e-2 at the roughing pump) – still going down from minute to minute. This looks very fine to me!
Next steps will be improving the HV-power supply (42,5kV and 1 kW), finishing the gas supply/MFC and integrating the HV-PS in my LABVIEW GUI.

Greetings from Austria,
Werner
Plasma just after starting the pump
Plasma just after starting the pump
after some time - during the cleaning and bake out process
after some time - during the cleaning and bake out process
main chamber and Turbo to the right
main chamber and Turbo to the right
roughing pump wit foreline trap and magnetic shut off valve
roughing pump wit foreline trap and magnetic shut off valve
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