Notes: Modified Magnetron Experiments/
With Vacuum Exhaust / Experimental Objective/
Results
19 Oct 2012
Back in the latter part of 2010 I was interrested in conducting magnetron experiments; initially for old WW II magnetrons requiring
extermal magnets, see
Magnetron Page. Several of these and those with magnets were
purchased from Ebay , I quickly discovered that many
of these were severely out gassed; that is the gas inside the tube ionized shorting the anode and cathode. Examples of this is illustrated
in the following links:
725_1,
725_2, and
2J50_3; I also discovered that gassy tubes conductivity was
enhanced when the magnet was used.
In addition to the "purchased from Ebay" link I have provised an
additional link listing the out gassed magnetons. Later I decided
to try something much more intense than magnetron aging; these tubes were gassy well beyond where this technique could be used. I
decided to try what I call
self ION pumping based on my experience with cathode sputtering effects. I have had very positive results
using this technique; was able to detect RF output at various degrees; at first the RF pulse width was very narrow but as the pressure
decreased the width widened.
Introduction:
Objective/ Modifying the magnetron:
When I first investigating the out gassing many of the tubes displayed gas illumination like as in a gas discharge tube, when HV was applied. This suggested that the pressure was somewherein the tens of micron pressure. I also observed RF output in both cold and hot cathode modes. In the former , to my supprise, cold cathode RF output was generated while the tube seemed slightly gassy. Since the tubes in question were sealed I had no way of measuring the partial vacuum pressure. Many of the tubes were useless to me as they were so I decided to modify at least three of them with vacuum exhaust:
The idea I had in mind was to start off using a two stage mechanical vacuum pump ( later use a diffusion pump) to see if at various stages of evacuation I could get the same results as observed with self ION pumping with the sealed tubes. I also wanted to document and measure the various stages of evacuation using a thermocouple vacuum gauge verses the voltage current waveforms. Additionally at what pressure does RF output occur; the effects of RF output pulse widths and pressure.
The First Experiment and Results:
The initial experiment was tested using a Welch 1400 twe stage vacuum pump,no TC gauge was used; a photo of this experiment is shown below:
To vacuum pump
RF excited Neon Bulb