New Fusor Project

[Richard Hull]

Note the harbor freight meters, especially in voltage mode are high impedance and they are not noise shielded internally. This may explain the volt meter going nuts.

Richard Hull

[Cai Arcos]

Following from my own personal experience regarding those cheapos, I would second what Richard said. Noise is quite an important issue, specially in your setup where everything is packed close together. Sparking between the contacts of the rotary switch might also be a problem (as it happened to me). What's worse, the noise will show incorrect and inconsistent issues (see my recent threat in the matter).

I have since changed to a much simpler voltmeter like this one (https://www.amazon.es/MakerHawk-Voltmet ... ols&sr=1-1) and adapted it's impedance. Still sensitive to noise, but when it fails it stops working completely, thus letting me know something is wrong. Ultimately, I will move to analog metering I picked up in the recent HamFest.

I do not see the entire wire set up, so this might not help, but I often found that noise happened much more frequently when the wire coming from the resistor to the multimeter itself was close to that of the HV PS. Might be spacing them more (using separate tubing or similar) would help. I definitely do not see how the ballast resistor is at fault here.

Regards:
Cai Arcos

[Mark Rowley]

Thanks for the response Cal. After yesterday I’ve been considering going full analog. I’ve have access to quite a few 50uA meter so I may be testing one in the near future. Being an aficionado of vintage electronic gear, I’d like the appearance as well.

Mark Rowley

[Richard Hull]

Analog is fine if you have the old meters. The Harbor freight meters are great for pure DC and 60hz AC, and in relatively noise free environments. Digital meters will always read easier provided your voltage is not bouncing around. If it is moving about a specific voltage, an analog meter will be easier to read as its response is poor and will give you an average around the voltage present.

For the fusor, an analog voltmeter really needs to be a 20ua or 50ua meter movement to keep the power requirement of the dropping resistors low.
An analog current meter can be 500ua or less, although 1ma is OK.

For older meters made before or during WWII, make sure they are accurate to full scale as magnets weren't all that stable then. Used a harbor freight meter in series with you analog meter under test along with a variable power supply and a suitable dropping resistor. You might be surprised at how far off older d'arsonval meters might be.

Richard Hull

[Mark Rowley]

Deuterium Star
27.5kv / 2.85ma / 35mTorr

My corona tube seems to do well with a PoBe source but the electrical noise from the Fusor is wreaking havoc. Since I want to move forward with the Columbus-1 pinch tube project, I'll just bite the bullet and get the Bubble Detector. I'll need it anyway.

Mark Rowley

[Richard Hull]

Noise seems to be and has been an issue with the Corona tubes. Some folks seemed to have licked the issue. Nothing reports like the Bubble dosimeters or activation techniques.

Richard Hull

[Dennis P Brown]

I got around this problem by encasing my detector tube in a copper pipe with soldered end caps (one cap had a high voltage coaxial connector); of course, co-axial cable for all devices including the power feed. My power supply was an isolated battery/inverter/high voltage supply so noise from the fusor via the house wiring wouldn't create any issues via ground loops. Worked extremely well.

[Mark Rowley]

I was just about to do something similar. Last night and this morning I spend several hours going through the forums and found some good info from Lukas and Carl. Instead of going for the standard bias of 700v, I set it just for the cusp of corona mode at 670v (as suggested by Lukas). I then cleaned up my connections and swapped in a much heavier shielded cable. That was the fix. Practically removed all noise. And you’re not kidding, once dialed in, these corona tubes work good.

Mark Rowley

[Richard Hull]

"dialing in" is the issue with Corona tubes and boron lined tubes. They do not operate correctly, unless fine tuned by a careful hand. Like any such electronic adventure in neutron counting, once "dialed in" you can replicate it at any future time. You have learned what is good and what is bad in the process due to a good bit of hands-on effort. You know when it is right by the application of artifice as much as science.

Richard Hull

[Mark Rowley]

After multiple fusion runs, I can see that the following modifications will have to be made before I can proceed much further.

-Reduce grid size from 0.50” to 0.30”-
Uneven heating on the grid seems to suggest half inch is still too big. The outer ring seems to get red hot long before the inner ring which may be due to its slightly closer proximity to the shell. I’ve been told 0.30” dia is probably the best size for a 2.75” system.

-Pot HV supply in oil-
It’s totally clear 30kV is the corona ceiling for the precipitator supply which totally limits any performance improvements. At just over 30kV corona losses are huge.

-Increase deuterium purity-
My Horizon PEM cell tends to slow to a snails pace after 2 minutes. One 100ml charge currently takes over two hours to fill. The plastic syringe I’m using as a reservoir only lasts about 3-4hrs before air totally contaminates the deuterium. I’m considering a glass syringe or revisiting the Mylar balloon idea. Direct feed doesn’t seem feasible with the higher deuterium pressures and my oversized and thirsty HS2 diff pump. Regarding it’s slow production rate, the manufacturer recommends cycling it back and forth between generating electricity and gas about 6 times. Seems to help, but it’s still a far cry from when it was new.

-Install additional xray shielding-
Just a necessity. I already have shielding via the heavy bricks, but I’d like more. 1/8” lead sheeting is on the way.

-Install video camera-
Ive learned that operating the Fusor solely on IFR is pretty easy. There’s almost no requirement to see the plasma but not having the visual removes a lot of the fun! Its also probably good to monitor the integrity of the grid as you push the system.

-Install analog milliamp meter-
The cheap DVM I’m using for amperage monitoring does way better than the free HF units but it still gets a bit fluttery over 25kv. Ultimately I plan on using a good digital system but for now I’m going to install an analog milliamp meter.

Mark Rowley

[Richard Hull]

For me, the only reason for a view port is to monitor the grid heating as you push the system. I have long ago gotten rid of the "oh, look at the pretty star" fascination. Video monitoring is both safe and allows you to view the grid on a 50 inch flat screen is that is your "thing".

Analog metering is fine, but by 2004 I went all digital, when I could buy 4 digit bright red LED 200 millivolt, fixed panel meters for about $20.00 each. I tuned them into my system with dropping and shunting resistors and they are still there today. Such really good 1" tall LED digital panel meters are rare today and when found are more expensive.

Richard Hull