Advice for using microwaves to ionize deuterium?

[Sven Andersson]

Hello all,

Let's say you were to use microwaves from a magnetron from a microwave oven to ionize deuterium; what kind of general advice can people give me? In the old article I attached, the cavity is smaller than the wavelength. How can that work? The QK-62 magnetron gives radiation with a wavelength of 9 cm, but the cavity is 7.5 cm high and wide.

They mention "tuning stubs"; what is that?

Let's say you build a cavity like the one in the picture; how do you attach a magnetron to it? A microwave magnetron has only a short stub protruding, see bottom picture. How do you get the radiation into the cavity, so to speak?

Inside the cavity there is a "coupling loop"; what is that?

Sven

[Jerry Biehler]

Doug Coulter has done it. The problem is generic magnetrons do not like to be ran at low powers and typical microwave ovens operate and many times the power you need. You might just go with inductive or capacitively coupled plasma like other have done here. You can run those off a cheap RF power source.

[Dennis P Brown]

Anyone trying to use standard microwave oven sources that isn't an expert is asking for major safety trouble. Creating an absolutely EMF shielded fusor or other device is extremely difficult and any failure results in the experimenter getting bathed in microwaves that are ideal to cook human flesh - especially eyes. Lower doses are likely to lead to cancer. There is no up side to generating a plasma from these devices rather than via a transformer /RF source but massive safety issues. This is a terrible idea.

[Richard Hull]

Correct! The oven maggies are tuned to, ideally, heat water molecules. Human's are big bags of water. Thus a biological death from within one's self can be achieved quickly and easily from oven maggies in the hands of the blundering experimenter.

Ever had the water in your eyes come to a boil?

Richard Hull

[Bob Reite]

I wouldn't say that building a shielded fusor for 2.4 GHz would be that difficult. You hopefully are using a stainless steel chamber of some sort. The viewport would require a screen, like is seen on a microwave oven window. The vacuum inlet would probably require a screen as well.

I do agree that experimenting with 2.4 GHz at any sort of power requires the investment in a personal RF safety monitor and training in RF safety procedures.

But other challenges await! Unlike the home microwave oven, which (as long as you put food in it) is a mostly resistive load, who knows what gosh awful impedance the plasma will present. You would be operating with no load until the plasma lit as well! The way around this is to use a circulator and reject load, then the magnetron will be happy. You'll probably need to build an adjustable matching section between the circulator and the chamber that you can tune for maximum power transfer once you get the plasma to light.

However we want to accelerate just the deuterons, which requires a DC source. Or is your thought to add the microwave exciter to use in place of ion guns?

[John Futter]

Sven
I do not get how you pick out of the box ideas then do absolutly no research
and then want hand holding help

your drawing referenced a QK62 magnetron which is a 60-70watt 2999 to 3330MHz tuneable unit
it has no similarity to a cooking microwave oven magnetron which is on a completely different frequency and 30 times more powerful
time to learn and do your own research

[Dennis P Brown]

And do be aware that leakage via a microwave heater for a fusor will occur through the vacuum system - mechanical pumps are not emf shielded nor do KF fittings offer any seal against that - unless screen shielded ports are used for all such ports and ditto for many vacuum gauge detector heads - these are some items that can be a dangerous source and must be tested and then shielded as needed - and properly. It isn't the obvious port window that is the sole danger; also, proper electrical sealing for dissimilar metals (a screen mounted in the window port or an inlet port) can be a very tricky issue due to thermal expansion issues. This methodology just isn't viable for someone that has no microwave experience with safe, low level systems.

Fusors have a number of special safety issues but microwave heating isn't something that offers much in the way of benefit but since oven units are cheaply available as junk, I find this a very dangerous and tempting possibility for someone with no knowledge who might then think this is an obvious, cheap and fast solution to the power issue. It is certainly not for anyone without prior experience in the field.

I do not like to normalize this type of approach in any manner. As I said, it is for very advanced people - through, frankly, I see no benefit overall even for them.

[Sven Andersson]

Thanks for all the advice! I realize now that microwaves are too difficult and too dangerous to use for my purpose. What Niels Grundsø is doing is safer apparently. If you try his approach and fail, you may squander money and/or time but will not injure yourself at least. Where can I read up on what he is doing so I don't have to pester you unnecessarily with questions?

Sven