Why Is It Not Producing First Light?

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Tyler Christensen
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Why Is It Not Producing First Light?

Post by Tyler Christensen »

We finished building the whole system today and attempted to get a first light. The problem is, it didn't. First we hooked it all up with a rectified 12kv 60ma neon sign transformer in oil since the chasis of each transformer is floating on the center tap voltage and got a reading of 15,000V DC unfiltered. There was nothing from the camera on the viewport. Next we hooked up a meter in AC current on the primary of the transformer and noticed a reading of .36A at 6600V secondary (50 volts primary on variac), then we disconnected the grid and ran only metered rectifiers and saw that it was still .36A at 6600V. This tells us that there is no draw at all on the chamber. All tests were run at a 0 micron reading.

The grid is aproximately 1.5" in diameter and is made of tantulum wire. Would using a different metal perhaps help? I'm not sure how it would since the tantulum obviously conducts electricity.

The feedthough consists of 2 spark plugs held back to back through a pvc female joiner which is filled with oil. The inner plug (the one going into the chamber) has the voltage (note I didn't say current because there apparently is none!) going through the center pin, and the outer plug has the ground tab still in place so that one contacts the inner pin, explaining why the wire connects to the ground of the outer plug rather than the pin. We tested all this with a continuity meter and noticed that there was resistance and then researched spark plugs online and found that there is actually a resistor in them. Perhaps this is the issue. We did run the power through a spark plug however and found that we were still getting the full voltage (perhaps the issue is that current can't get past the resistor but the voltage is?)

Posted some picts of the setup below.

Any thoughts as to why this is having issues?
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Mike Beauford
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Re: Why Is It Not Producing First Light?

Post by Mike Beauford »

Hi Tyler,

Yeah, the spark plug with the resistor inside it won't work. Get one without the resistor inside it and try it again.
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Re: Why Is It Not Producing First Light?

Post by Tyler Christensen »

Any ideas why this is happening?

http://www.youtube.com/watch?v=0gS0LmPf_N0

Even with the grid disconnected, just the transformers and rectifiers operating do it. Is it just a lot of RF noise can actually cause that?
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Re: Why Is It Not Producing First Light?

Post by John Futter »

Tyler

If the voltage is there the current is also there if there is a path to ground ie through a discharge.

0 microns??? if this is right there is not enough gas to get a discharge.

As to Mikes comment about the spark plug resistors these are usually about 10K ohms ie a good start to a ballast resistor in the system -- make sure you measure what the value is.


have you got an earth return to your oil filled plastic box???


Draw out your wiring using standard techniques for a DC circuit labelling the spark plugs , the chamber ionisation space and all other wires -- make sure that all make sense

hang in there
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Re: Why Is It Not Producing First Light?

Post by Dan Tibbets »

[EDIT]
I clicked on your images and see your PVC pipes are diodes, not resisters. It is hard to trace the wires but it lookes like you tried to set up up a full wave bridge rectifier. But I am uncertain of the labels on two of the diodes. From an AC lead one diode should have the cathode pointing at the AC connection and the other diode should have the cathode pointing away from the same AC lead. Presumably, if you measured a negative DC voltage beyond the rectifier it is arranged correctly.
Additionally on the vacuum gauge- thermocouple gauges generally only start responding once the presure has droped to ~ 5000 microns ( well beyond the point where your dial vacuum meter will have bottomed out). My gauge displayed dashed lines till this level was reached. Make sure your gauge does not display "0" at this thresold level. I see alot of joints with teflon tape and I've seen references that some type of silicone glue/ gasket sealer or thread sealing fluid is much better- the teflon tape often leaks to much. [end EDIT]

Spark plugs the problem? I'd guess not so long as the continuaty test was ok.. I used a resistive plug as a feed through. It had ~ 5000 Ohms resistance, and finally burned out due to the current that my microwave oven transformer was providing (and my poor to modest vacuum levels). 5,000 or even 10,000 additional ohms of resistance should not dim the glow that much. I couldn't quite read the labels on your PVC contained resisters(?) but presumably they are providing alot more resistance, how much?
I can get a visible glow with a 5,000,000 ohm resister and a 9,000 volt NST with the variac at low levels ( maybe 15-20 volts in). In the image I'm not sure what kind of vacuum pump you have, if it is a piston or diaphram pump it probably cannot reach adiquite vacuum. The zero micron reading on the vacuum gauge is suspisious. Even a very good dual vane rotery pump cannot reach that level, is there a diffusion or turbomolecular pump somewhere? With the vacuum pump pumping down the chamber did you watch the mumbers droping on the meter?
If the wire wraped around the wing nut is your ground it is poorly secured and dangerous, and if not a good contact then that might effect the glow discharge.

Finally, if you are indeed reaching a vacuum of zero microns there is not enough residual gas to ignite a glow discharge. I have seen repeated references that ~ 5 microns is the lower limit where you can get a glow discharge without supplimental ion guns and/or electron guns (?), ie- do your initial tests at ~ 50-200 microns or even up to ~ 1000 microns.


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Mike Beauford
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Re: Why Is It Not Producing First Light?

Post by Mike Beauford »

I'm wondering if you have a good ground on your fusor shell. It wasn't apparent in the pictures if you've got a proper ground within the system.
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Re: Why Is It Not Producing First Light?

Post by Tyler Christensen »

I have a diffusion pump running behind a welch 1400 and it is definitely reading 0 microns. I thought the best vacuum possible was the best. Is this true when actually performing fusion but not for a glow discharge? I'll cut the diffusion on the next test.

It has several grounding points, that is just one of them. Continuity was tested and it is definitely grounded to multiple places.

The PVC is actually rectifiers. I stupidly did not have a ballast resistor hoping that the spark plugs would be enough of a resistance. After testing I have now found that the plugs were instantly burned out at their internal resistor. I'm going to try to buy some non-resistance spark plugs tomorrow and then add in a resistor. Would a water resistor work well?
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Re: Why Is It Not Producing First Light?

Post by Tyler Christensen »

Here is a schematic

The oil tank is not grounded at all since it is all floating due to the unfortunate nature of the transformers being center tapped.

Can the two transformers be operated in series rather than parallel? I remember once reading that putting secondaries in series can cause transformer burn-outs due to the two coils being in a different phase. Would this not be a problem if it is put in series post-rectification? I know 30kv at 60ma would be a lot more beneficial than 15kv at 120ma.
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Re: Why Is It Not Producing First Light?

Post by Dan Tibbets »

I'm surprised your two spark plug arrangment burned out so quickly, my single resistive spark plug lasted several weeks with a much higher current MOT. Check carefully that your feedthrough is not shorting out some where. If there is a location where it can jump a small gap/ crack (such as a few millimeters) it may measure fine with an ohm meter, but short with high voltage.

Concerning using multiple NST (oil ignition transformers are the same) this site has some information
http://www.kronjaeger.com/hv/hv/src/obit/index.html

My limited understanding of water resisters is that they are fine so long as they are on the AC side of the circuit. If used on the DC side it is essentially an electrolysis cell. At the low amperages they probably wouldn't explode but the gas produced could pop a seal. Also, in a DC circuit any ions will accumulate near one or the other electrodes and the resistance will not be constant.



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Richard Hull
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Re: Why Is It Not Producing First Light?

Post by Richard Hull »

It is all so simple. It you take a well insulated rod and hook the hot lead to it and put it close to the spark plag cap an draw and arc then you have a path to ground, (effective short), that the transformer thinks is a lot prettier than going to the trouble to break down the rarified gas in the chamber. You have a low resistance ground path and it is most certainly in the spark plug or its mounting somewhere.

Non resistive spark plugs work great in demo systems, but will not work well or for long periods in real fusing systems. Most plugs are not that vacuum tight either. They are meant to seal from pressure from below and not from above. In my early days, I always epoxy filled the lip outside where the inuslator hit the metal.

Your problem is in the plug or its mounting system.

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