Dear Azzeddine,

Yes it is possible. But you cannot control the peak power. You can only control the duty cycle. For that you have to make one power supply of -4KV 400mA and use the filament power supply from the oven transformer itself.

Or you have to do litting bit of modifications as follows.

Use normal power to power the rest of the microwave oven circuits and separate variable transformer (variac) to power the transmer that supplies the power to magnetron and also the same transformer will supply the filament current also. It is the easier method. But you have to bypass some interlocks.

Nabhiraj

India

Yes it is quite possible.

In fact I designed such a generator by separating out the magnetron head from the microwave oven, and successfully generated plasma during my Masters project. However, I used the built in supplies of the oven by attaching extra wires.

As Nabhiraj pointed out, to have a control on the power you need to make separate supply. Also you need to cool the head properly for prolonged operation.

Actually you can buy 2nd hand Magnetron heads from microwave repair shops very cheaply and try it out by making a circuit. I had such a plan, but finally did not go through because we got a proper generator.

I am attaching the schematic below.

Few notes:

The spectrum of the radiation is usually broadened because the magnetrons are not of very high quality usually.

Secondary peaks may occur due to recirculating electrons in a 2nd hand magnetron due to ageing.

The above problems can be somewhat rectified by imposing extra ring magnets on the magnetron (there are papers on this). But it will require some effort and time.

If you are interested in the final plasma only, then these would not pose much problem.

Hope this helps

You can use the microwave generator for ECR source at low gas pressures. The broad spectrum of the signal will not be a problem as you advised Professor Tynan.

If you would like to work at high pressures in a resonant mode of the discharge in the metal chamber you may have problems with the production of dense plasma.

You can also consider generating a microwave using US patent number 3467471. This patent is available using freepatentsonline.com, and is probably expired since the filing date was in 1964. This is a tube circuit and would require some engineering to determine the parts; oftentimes such a high-powered tube can be purchased from vendors in Russia and the Ukraine. You can also get the glass parts for a few hundred dollars. Used "networks" (the glass parts plus the coil and cooling plumbing) run around $3k used.

I'm very curious how it turns out if you choose this option.

Yes, it is possible, last month demonstrated on a small device in Pakistan. Ordinary kitchen microwave oven was used.

The simplest setup would be to perhaps ignite the microwave glow discharge at pressure of ~ 100 Pa.

Here is the video of such experiment: http://www.youtube.com/watch?v=8rUrHVuBlc8

Please make sure that the whole thing is screened with grounded metal mesh as advised above, so no microwave power is leaking. One can get severe burns otherwise.

Thank you all for your contribution on this subject; I have some questions ; we all know that we should not put metalique objects inside a microwave oven, doest it mean that my vacuum chamber and substrates must not be metallique?

The gaz pressure inside my chamber will be around 10Torr is this OK or I will have to work in a higher or lower pressure in order to get a stable microwave plasma ?.

What would be the temperature inside my vacuum chamber when this microwave plasma is runing?

Instead of adding a magneique field in the chamber can we just add to this plasma an electrons emeter ( a negatively biased hot tugsten filament) in order to enhance the plasma density like we do in DC glow discharge plasma?

Best regards

Metal parts would absorb the microwave power and would be heated up. More power is dissipated on the metal parts - the less goes into the plasma.

The maximal gas pressure is defined by your MW source power. The higher the pressure - the shorter is the electron mean free path between collision with the neutrals - the less energy electrons are getting between collisions. Please check this paper for details: http://arxiv.org/abs/1207.1901

Hello,

If the plasma strikes correctly, you will not have problem of metallic objects, if there is plasma then there will be lots of arcing that may take place. In fact you may chose to place a small pin in the set up so that it can easily strike plasma be sparks generated on the pin. If you dont use any attenuators, then the full 800 - 900W of microwave power will reach your targets and indeed the temperature will go up quite substantially. But, in a normal microwave oven, you pl keep a glass of water besides your vacuum chamber which will absorb microwave power and reduce the available power in the chamber. If you wish to increase the plasma density, then you need to go in for better chamber design with proper magnetic field and microwave feed system etc.....

good luck

Nabhiraj

Yes. It's actually been done before by Aaaron Ribner in NJ. The product is called Plasmapreen and is bought & sold commercially & is quite successful. Google the name & you will find the company.

Yes, is possible to build a microwave power supply from the accessories of a microwave oven. You could look for on internet my paper (Experimental research for the mass flow control of the metal vaporized and ionized with microwave used in electric propulsion) where you will find an electrical schematic for you work.

Dar George

As far as I know the système shown in Fig 4of your interesting paper that you have used to adjust the duration pulse, works without any problems only for resistive loads because the current and the voltage are in phase for resistive loads ; when the voltage is cut the current will cut also, but in your case the load is the primary winding of the high voltage transformer which is not resisitive . I don’t understand why you did not have any problems with this “electronique variac” applied to a non resistive load.

Best regards

There is an interesting experiment with a microwave oven where you can put a lit candle within a microwave oven, close the door and switch on the microwave oven. You'll actually see an aurora because the thermal energy of the flame will ionize the air molecules. Thus, the electrons will be accelerated under the action of the microwave field and they will radiate, provoking the aurora colors.

Therefore, naively I'd say that yes, you can build a plasma directly with a microwave oven and a candle, so it must be possible to do it externally with the components of the microwave oven. On the other hand, I know that this may not results in a very useful plasma because I see no way to control its dynamics, but I think it's a good example. I suggest you try within a dark room to check the aurora onset, otherwise the low intensity of the radiation won't let you observe the aurora.

A possible problem that you may encounter is that, as microwave ovens have a fan inside, it may happen that the fan puts out the candle, but in general it should work. Let me know if you could observe it or if you had some problems.

Regards

Researchers at my university have taken a microwave oven and placed a glass vacuum chamber inside of the oven. They then evacuate the chamber and fill it with inert gas such as argon at lower pressure. Then, just by turning on the microwave (as you would if you were to cook popcorn), they develop a diffuse argon plasma, which can be used for quite a few tasks.

Long story short, it is very easy to do, just put a chamber in microwave, with a pressure inside of the chamber below atmosphere, and it should be easy to ionize the gas.

Thankyou jacob, I will do it. And i will let you know what kind of surface treatement I did.

Best regards

Yes, with using the accessories of the microwave oven, one can built the power supply for magnetron for generation of the microwave power. The magnetron requires a low voltage, high current AC power supply, floated at negative high voltage for the filament (thoriated tungsten coil, directly heated by AC or DC) and a high voltage negative and low current DC cathode power supply. The body of the magnetron is at ground potential. To energize this magnetron, a DC power supply of -5 kV, 1 A for cathode, and an AC power supply of 5 V, 20 A for filament (floating) is required. One has to take care about this.

Best Regards

RE: Sunil Kumar: Nope, sure no!!

Atmospheric MW plasma in AC PS gives a dull-load 100 Hz noise which is just damn laud. Thus if the aim is atmospheric, then DC PS is the solely choice. BUT V-A characteristics for typical owen magnetron has damn narrow generation part, few to ten volts out of 3 or 4 kV slope. Thus, if DC, the PS must be a CC-SMPS.

The MW cahnnel must consist of the parts below - the Launcher box with magnetron on top. With Isolator box aka magnetic circulator to kill the back-flash killing the magnetron. This box have attached the Waterload aka water-cooled resistor to damp the backfiring heatflux and GHz diode helping to measure the back-wawe intensity. Without of this is impossible to conjugate the impedances.

Next box is three-knob Tuner aka impedance matching filter. Avoid the two-knob cheap versions.

After that stays lambda/half waveguide with closed end, scattering back the wave to it`s length quarter. Thus in qarter it creates the double intensity field. In that point make a drilling with quartz tube of double walls, in outhern circulates the "electronic fluid " damn expensive coolant with neutral dielectric factor, but in innner tube one push an argon carrier gas, exerting out in upper end like a candle flame.To get the first ignition anyway one needs to apply the high voltage pulse in this pipe against the walls of waweguide. 1 MHz spark is the optimums as being rather cold.

Other method is MW mosfets and Royer circuit, but then the power is far not so high, frequency is rarely over 1 GHz and flame zone is so small as few mm3 in contrast with magnetron where is stays several cm3.