Fusor Forums

Hi fellows,
After many years lurking around on the Fusor consortium, our system is taking form.
Down South hemisphere, all Hi Tech parts became more expensive than in the North hemisphere. Flying them almost 10,000 km and paying Customs typically brings the price up to a factor 2.5/3.
And, yes, procrastination also adds up…
With German Mülller, friend and partner in some technological activities, we are assembling our small 2.75” cross fusor.
Vacuum and deuterium supply almost done. Now we need to devote time and brain to high voltage supply and electrical measurements.
Neutron quantification almost none; just planning to measure activity on silver sheets.
See picture of setup.
We appreciate and aknowledge the many comments and suggestions received along the years from a so excellent team! PS: note fancy clamps from Andrew Robinson!

I dont know what range the baratron you have there is but the more sensitive ones need to be in a vertical position to read accurately.

Hi Jerry

Good point, thanks!
That one is 100 torr but we have also 10 torr FS.
We will manage to put an elbow or swap positions with the viewport, now at cross lower port.

First off, nice fusor! (Aside, do you have a Geiger Counter to check on the X-ray threat?)

Second, activation of silver requires a high neutron output so don't be discouraged if you do not succeed in that neutron detection methodology.

Finally, what voltage and current can you supply?

Hi Dennis,

Thanks for your comments.
We have an old pancake Ludlum Model 2.
Also assembling a gamma spectrometer but at slow pace.

About HVPS we will try first with a low power one, as Mr. Rapp did. He succeded activating silver.
And working in modifying an old X-ray equipment, 100 kV 100 mA.
Lead sheet is in its way to our lab.

Wow, that is some power supply - 10,000 watts!!! Amazing. You have some massive input wiring, I bet for that monster.

Cables for 100 kV are rare and expensive. Diodes for that range are not too rare, at least, but expensive. Maybe you can string a large number of 20 kV/one amp diodes available from China to save money. They are less than $3 each.

Are you considering just operating at 50 kV or so making the cable/insulator feed thru and diodes issues easier and cheaper (you should seriously consider operating all diodes/resistors under oil (cheap synthetic motor oil works very well. I do that.))

Also, the input variac to handle that wattage, if they can be located, would be highly expensive, I'd think as well.

Ok, you should be fine. Its the ones around 2 torr or less that are position critical.

Jerry:
Thanks, good to know that.
Dennis:
We have an almost complete X-ray equipment.
Xformer is under oil, silicon diodes also.
We plan to run on the negative half only, with a variac for 220 V (our mains voltage) 20A.
As ballast resistor we plan to use a water one, avoiding to open the xformer container. Still managing to couple those conical terminals to our HV feedthrough.
As a matter of fact, the HV feedthrough limits the voltage to approx. 30 kV.

A water based ballast resistor is an excellent idea. You make your own? Is it a Cu based solution or are you just using highly purified water?

Why does the HV feed-thru limit you to 30 kV? Is that its rated max? Not that it matters - in a small chamber 30 kV will probably give you plenty of neutrons.

Hi Dennis,
Following Mr. Rosenstiel’s suggestion, our water resistor will be a plastic tube with water and a little of copper sulphate.
Yes, the maximum rated voltage for our HV feedthrough is 30 kV.

Roberto Ferrari wrote: ↑Mon Jan 22, 2018 4:47 pm Hi Jerry

Good point, thanks!
That one is 100 torr but we have also 10 torr FS.
We will manage to put an elbow or swap positions with the viewport, now at cross lower port.

Roberto,

Please be aware,that the 10 torr FS unit puts out 1mV per Micron of pressure, so that you are at the very far edge of the transducers usefull range.
With fusor pressures around 10-50 Micron, You will be measuring from 10-50mV, not a lot in a noisy environment. A better choice would be a 0.1torr unit, or even a 0.05 torr unit.
With a full scale output of 10V, the latter will still produce a full one volt at 5 Microns, and as such deliver a better resolution.
Another benefit of having a transducer with a FS close to the fusing pressure is, that it is able to deliver useful output at a couple of decades higher vacuum, prior to letting the deuterium into the fusor, the 10 torr unit will "bottom out" long before that.
In short, with a 10 torr unit, you will miss most of the action you get from the diff. or turbo pump, since it's output has fallen to 1mV at a pressure of 1 Micron.

Just some thoughts I did before choosing my Baratrons, both 0.05 torr FS. (One of which, by the way, clearly is marked, that it must be mounted horizontally to read correctly, go figure)

Cheers, Finn Hammer

Hi Finn
Thanks for bringing that issue. You are right.
We already had those Baratrons for other purposes. Now on eBay seems to be a restriction for exporting those devices, so we feel unsafe buying one and sending to our country.
With regard to high vacuum readings we already have a Bayard-Alpert gauge.

Finn is correct. My 10 torr unit is very good and accurate from 10 torr down to 150 microns but is very difficult to use below that (never been able to get a stable calibration in that extreme low end.) I use a very precise thermocouple type gauge and it works from 0.150 microns up to 50 microns (Calibrated both extreme's and agrees closely between) and is fine for up to 200 microns (though not too accurate in that upper range.) Finding solutions for pressure is not easy using e-bay surplus but can be done. Of course, I use an ion gauge below 0.1 micron.

Finn and Dennis,
Thanks for your advice.
We are getting a loaned capacitance manometer 1 torr FS.
As soon as installed, we will report results.