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Greetings!

Posted: Thu Jun 22, 2017 10:06 pm
by Joshua Turbyfill
I'm a high school student and as a summer project I'm constructing a high-powered fusor. I'm well in to the project, with about half of the system built. At the moment I'm setting up a He-3 detection system. I have to say the surplus of information that you have on this forum is invaluable, and has been a great resource for me. Its nice to meet you all.

Best Regards,
Joshua Turbyfill

Re: Greetings!

Posted: Fri Jun 23, 2017 5:29 am
by Dennis P Brown
Welcome.

You might want to post on a He-3 detector system (your design) and read some FAQ's on detecting fusion in a fusor; (a He-3 detector will not work on a fusor, ) oops; LOL - misread the post! A He-3 detector is ideal. Sorry about the mis-read.

Posting on your current build and what you are going to build would be a good start.

Building a real neutron detector would be extremely useful since it can be used with a fusor and is required for proving fusion in a fusor.

Re: Greetings!

Posted: Fri Jun 23, 2017 5:36 am
by John Futter
Dennis
You wrote
"You might want to post on a He-3 detector system (your design) and read some FAQ's on detecting fusion in a fusor; a He-3 detector will not work on a fusor, frankly (rate of fusion is many orders of magnitude too low for a He-3 signal"


Not quite right. A He3 detector will work beautifully on a fusor with a moderator
It is the most sensitive detector available to hobbyists albeit very expensive compared with other options such as BF3 and corona tubes ( russian).

And it doesn't crap out after about a year like bubble detectors - and yes the metrology has to be right to elliminate gammas and HV noise from clouding the results with false positives

Re: Greetings!

Posted: Fri Jun 23, 2017 10:34 am
by Joshua Turbyfill
For the detection system I have a Russian СИ-19Н He-3 detector tube with a BNC splitter. Quoting the seller on eBay, "the splitter contains a 500K resistor for HV bias and 100pF capacitor for HV bias filtering". Its powered by a Fluke 423A 0-3kV power supply and connected to a PicoScope 2204A PC oscilloscope which in turn is connected to my laptop. Custom software, written by the same guy on eBay, utilized the PicoScope's SDK and outputs neutron counts, neutron spectrum, and a few other things that are apparently rather useful. As for a neutron moderator I'm planning on using paraffin wax, although I'm not sure how much so if you have any suggestions I'd greatly appreciate them.

Re: Greetings!

Posted: Fri Jun 23, 2017 10:52 am
by Dennis P Brown
As for the amount of paraffin, not too critical if one has at least 4 cm or more (exact amount not critical. One is just thermalizing the 3 MeV (or so) neutrons.) Its a good idea to surround the detector since neutrons scatter and tend to "randomly walk" from all directions when a modulator is present. Also, shielding for x-rays is a good; these tend to be line of sight. If you chamber has fairly thick steel walls (a few millimeters) and the power supply energy is 30 kV or so, or less, that should be sufficient shielding. For mine, I did use a 2.5 mm lead shield to be on the safe side to prevent issues but again, not critical.

Re: Greetings!

Posted: Fri Jun 23, 2017 12:47 pm
by Joshua Turbyfill
Thats great, thanks for the info. Now the chamber is pretty thick, but the power supply is way over 30kV.
MDC 8" chamber during first stages of assembly
MDC 8" chamber during first stages of assembly
120kV X-ray transformer as it arrived
120kV X-ray transformer as it arrived
The transformer is rated at 120kV, but apparently X-ray transformers output several times their rated output when not under load. I was going to operate the fusor in my workshop but at that input voltage I'm assuming I'll need to be a fair ways behind some sort of shielding, like lead as you suggested, or maybe even cadmium and concrete.

Re: Greetings!

Posted: Fri Jun 23, 2017 1:49 pm
by Dennis P Brown
You will need serious radiation shielding if you operate in the highest ranges of that transformer. Also, do not leave any area that could expose someone to a dangerous level of x-rays without proper shielding. While current does matter (will control total flux, not x-ray energy), generally, if you operate above the 25 kV range one starts to get into issues where a steel shell will start to become transparent to the x-rays.

Since you don't need to go much above 60 kV since the very high range buys little extra performance, consider limiting the x-former to that max (you can, with experience, raise that when you are ready; remember, good fusion levels occur in the 30/35 kV range and even the 20 - 25 kV range with good detector systems.) Until you can handle high voltages, consider experimenting at far lower voltages but in no case, exceed the rated voltage of your cables!

Current (power) for fusion is important, too and transformer's provide less power the higher in voltage one goes. Also, voltage insulation becomes difficult above 25 kV and above 60 kV exposed points can act in dangerous (read unpredictable) ways. Few ever try voltages in that top range (over 70 kV) and those that do are very experienced with high voltage.

You need to really understand high voltage systems and related safety - issues such as proper (fail safe) chamber grounding, properly insulated cables (rated for the max voltage/power), and feed-thru's (very power dependent) are all critical issues that get very difficult the higher in voltage one goes. Corona issues are significant above 30/40 kV and especially severe above 60 kV. The list goes on. If that X-ray x-former is rated to 120 kV that is a supply that requires extreme caution in use - one mistake is death and could kill others trying to help the person. Posting High Voltage signs (warnings with the max rated voltage) are important; as is having proper radiation signs. You are responsible for not exposing innocent parties so how you shield around the chamber will depend on various parameters - keep that in mind, too.

An aside: one can buy any advanced equipment but experience is earned; read the FAQ's and read web based information and ask questions here before exciting a x-former and taking needless risks - fusors are deadly on many levels and for many reasons.

Looks like you are well on your way; so, keep at it and ask questions after reading up on the desired topic.

Re: Greetings!

Posted: Sat Jun 24, 2017 2:30 am
by Richard Hull
Obviously, you will have to variac that transformer to hold it back to the beginner's range of voltages, ~20kv, and work up with operational experience. I can't tell the size from your image. I hope it can deliver a continuous current of about 15-20ma at high voltage. Once you have a fully functional 3He system check your background count. Let us know what you get in the way of a background in counts per minute.

Richard Hull

Re: Greetings!

Posted: Mon Jun 26, 2017 9:17 pm
by Joshua Turbyfill
Thank you for the information. As per your suggestions I will start low and work up to 60kV. If very little performance is gained above that then I don't find it worth the radiation and HV issues that will arise. I plan on remotely operating it from 20m away, so I doubt that shielding should be an issue considering the inverse square law (correct me if I'm wrong). I'll also make sure to give you the background readings once I get everything setup.

The power supply setup includes a variac as well as a rectifier diode and a metal oxide varistor. It was explained to me that the diode in front of the transformer will make it output negative pulsed DC, and that the varistor will protect the input somehow. Will this regulate the current to keep it from sucking into too much current? Also, the transformer is rated at 120kV @ 15mA, so it should fit within the FAQ's suggestions of a 60kV @ 30mA power supply.

I'm a bit confused on how to setup the transformer. There are two wires with screw connections on them, which I assume to be AC inputs. Theres a naked wire on one end, which is apparently for a mA meter. Then on one side there are two pins and one pad. If I'm inputting DC current because of the rectifier, which input wire do I use? As for the output, the seller said to use just one of the pins as the HV output.
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The seller also said something which I don't entirely understand: "You will want a three grid farnsworth fusor system to use [the transformer] as it is. The outer one breaks down and ionized the gas with +60kV HV on the outer electrode, the center is the common earth and ground point, and the third is -60kV which accelerates nuclei to the center. This method works great since the hard work of ionization and electron stripping is being done by the two outer electrodes while the inner one does the actual confeinement and fusion." If the fusor outputs -60kV, where would I get the +60kV from? In the FAQ's it says that the positive lead of the power supply should be grounded.

Re: Greetings!

Posted: Tue Jun 27, 2017 12:10 am
by MatthewL
Hi Joshua,

You are correct that the two wires with the bolts on them in the first photo are your input wires, and the bare wire you say is for your mA meter is the center tap of the secondary winding and should be grounded along with you outer grid. The two pins are your secondary (AC) outputs. I would recommend you use an ohmmeter and familiarize yourself with what wires are connected to what. Do you plan on inputing a direct current or were you talking about your output? I know that there are posts in the FAQs that give greater detail as to an X-ray transformer power supply setup and the wiring within the transformer.
As for the three grid fusor I haven't heard anything about that elsewhere, but if you construct your power supply correctly it will work fine for the classic two grid design.

Re: Greetings!

Posted: Tue Jun 27, 2017 6:36 am
by Dennis P Brown
Good post on your part (except the wrong forum!) and it is important to know what does what in a very high voltage and power transformer before connecting any input power! Again, that transformer can be lethal when energized; as Richard mentioned and you need to do, get a variac rated for the required power and voltage to control the input to the transformer - I will not waste time explaining these ideas; you need to study up on x-formers, how they work (basics, not detailed theory!) before attempting any wiring or testing. When testing, use the smallest possible input voltage to keep the x-former output low enough to be "relatively" safe. There are a huge number of youtube and other sites that explain transformers operation/theory in many levels of detail. Visit some and study this subject - including rectifying x-former outputs. These basics must be learned to even begin to be safe around such lethal devices like an x-ray x-former.

Your statement
If I'm inputting DC current because of the rectifier

indicates that you don't know much about simple electrical theory of circuits/devices. You are dealing with exceedingly dangerous and lethal devices when building a real fusor. You get no second chances if you make a mistake with an x-ray x-former nor radiation above 25 - 30 kV. You really must read all the related FAQ's and study these subjects like x-formers!

The x-former, and diodes will need to be under oil (especially when used for a fusor supply or for any high voltage work; not necessarily needed for testing at lower voltages (say, a few kV or under) and very low power draw); however,one does not just place a x-former in oil. There is a procedure so research that in this forum and learn about that subject.

Richard raises a good point - whether the x-former can output 10-20 ma at 20 kV. This will be determined by the rated x-former power. Exceeding its rated load can quickly burn out a x-former (another reason these are placed under oil; to help with heat load, besides helping to suppress voltage shorting between the HV secondary winding's.)

Be aware that diodes have to be rated to handle the max voltage and an AC voltage has a rated value and a peak value - your diodes must be rated for the peak, not average voltage. If this isn't clear, you need to read up on this subject as well. A ballast resistor for the x-former output is another issue you will need to know but not important yet; however, Richard covers that subject in detail in the FAQ's so do read that.

Also, as Richard said, get your He-3 detector working - that will educated you a great deal on high voltage systems (in the low kilo-voltage range) that is also low current. Once you get the He-3 detector going, calibrating it for background and signal is very useful. If you have funds to burn, possibly consider renting (for six months so have the detector working first!) a powerful (but legal and safe) polonium source. Combined with a very thin and small (!) sheet of beryllium (extremely toxic so know the safe handling and disposal of Be!) and one can have a safe and low flux neutron source to calibrate the detector. However, getting a bubble detector is the easiest (but these are a little pricey) way to calibrate a detector but that does require that one has a working fusor ... .

Consider getting some type of Geiger-counter to scan for x-ray issues around your chamber. A surplus unit (ancient CD units) that works (can be rather low cost) is all one needs. A uranium ore (small amount; Richard sells these) can be used to confirm proper operation. This need not be calibrate - just knowing roughly if there is an x-ray flux is what's critical. Shielding isn't very difficult; I use sheets of slate available from any home depot - extremely cheap, non-toxic (unlike lead), easy to cut (use an abrasive blade) and can be stacked/glued together to form thick enough shielding for any x-ray threat. Doesn't conduct so safe around high voltage.

From now on, post your questions in the appropriate section; this belongs in the High voltage forum.

Re: Greetings!

Posted: Wed Jun 28, 2017 5:47 pm
by Joshua Turbyfill
I was talking about putting a 20A 1000V rectifier between the variac and the transformer. According to the seller on eBay the transformer will operate on a pulsed DC input and then output DC. As such I'll just use one of the inputs and one of the outputs unless that ends up being idiotic in some way, and add some ballast alongside the metal oxide varistor. I'm aware of the degassing and drying process for the oil, however I'm not finding proper transformer oil anywhere so I might end up using mineral oil, with active cooling and maybe mA and voltage readouts if I really need them. And with some more research I'll probably end up changing a few things but either way I'll get this properly setup soon. On another note, slate sounds like a great alternative to lead, but I wonder how much neutron radiation it would block at 60kV. Either way I might just skip shielding all together and operate from 50-70 ft outside. I'll keep the rest in mind, thanks.

Re: Greetings!

Posted: Wed Jun 28, 2017 10:03 pm
by John Futter
Joshua

WHOA
What a lot of bullS&*T

Time you learn't what to do before blowing up your local supply transformwer making your house and several others dark because of back feeding DC into a supply transformer. sometimes 1 -2 amps of DC is all it needs to saturate the core and BANG Darkness

You need a mentor before going further ---for your own and others safety

Re: Greetings!

Posted: Thu Jun 29, 2017 6:03 am
by Dennis P Brown
John is correct and please take what he says to heart; do not blindly add power to such a x-former. Getting help, as John has suggested is a good idea.

Also, not aware of anyone cooling x-former oil for a fusor; the power draw is just too low - my x-former is air rated and I added a fan just to be careful. But mine is NOT an x-ray transformer, however.

You can post questions about how to wire your high voltage x-former in the fusor power section (High voltage section.) Also, one uses a vacuum to get a x-former transformer (really within its winding's) to fill with oil so there are no trapped air pockets. Drying should not be an issue. I use synthetic motor oil (extremely good for HV; there was a study done so this isn't just wag) but most here use mineral oil or proper x-former oil - always a good idea when one isn't experienced.

Again, never just try stuff with such a lethal x-former. One needs proper proper cabling (60 kV is not cheap or easy to make connectors), oil tank for the x-former, ability to measure the input voltage, output voltage and currents and have a safe way to load the system. These are not easy tasks even for someone experienced - I spent over a month setting up and testing mine and I had both a lot of HV experience and a nearly turn-key system!

I strongly suggest that you get a cheap neon sign x-former (NST) and use that to test and gain experience with high voltage systems - powering, measuring and creating rectified outputs. A NST is a far safer (but even those can be dangerous if one is really careless - I am not saying they are fool proof.)

Calculating the stopping thickness of slate for a 80 keV X-ray (safety factor!) is trivial (called google.) Slate can be drilled so bolting in place is easy as is stacking. I will say that remote operation is not easy for an expert and no way a novice has the time and patience to remain that far away (and frankly, you haven't looked into x-rays if you think that distance is required.)

Again, as John added, you need to get a mentor; also, I feel you are not studying the issues carefully enough (taking what that person said about the x-former and not know that wasn't correct indicates you know very little on that subject.)

Learning is critical if one wants to be: 1) safe 2) not killed (ok, really part of one) and 3) ever get a fusion system up and running. Having little knowledge/experience is how we all start. The difference in people who make successful fusor's and those that don't is often that successful people read, study, practice/experiment on simple systems and work their way up to full level systems - buying advanced equipment and not understanding the HV power systems is a dangerous approach. What you have is not turnkey and you really need to learn about that system before attempting to construct such a dangerous x-former system.

Re: Greetings!

Posted: Thu Jun 29, 2017 9:42 am
by Dennis P Brown
A few more thoughts: first, please start posting in the correct forum! This is really for introductions only.

Next, consider buying a turnkey supply like a Spellman or Glassman that can supply 30 - 40 kV at 10 -20 ma (at least. Check the power rating before buying and the polarity! Negative only (but some allow both which is ok.) Also, make sure you get a working unit with the proper control electronics (some higher wattage units have separate control boxes and main supply box.) Also, you will need a proper cable (rated to handle the max. voltage) and a vacuum feed-thru (also correctly correctly rated.) Sell that x-ray transformer to someone with the knowledge to work with it safely.

Finally, maybe focus for now on other issues like the neutron detector and gas supply since these are both critical and needed as well. This will allow you to both gain experience and knowledge to help you handle HV issues when you get ready for that part of the project.

Re: Greetings!

Posted: Thu Jun 29, 2017 10:47 am
by Joshua Turbyfill
Dennis, I understand these things. Do you think I would jump into such a complex project without proper research? I only posted that question here because of how confused I was about that guys instructions, I wanted to know if they were legitimate since they obviously differ from how you all seem to be doing things, as well as pretty much every other reference online. In a couple of weeks I'll post my nearly-finished or maybe even completed fusor build.

And thanks Matthew for clarifying that it about the inputs.

Regards,
Josh

Re: Greetings!

Posted: Wed Jul 19, 2017 10:15 pm
by Andrew Seltzman
As far as the wires go, the bare wire connected to the frame is secondary ground, the 2 bolted ones are AC input. For the secondary outputs, the copper pad is the output of one secondary, the other two pins on the other secondary are the filament winding in series with the other secondary. Check with an ohm meter that they are connected to the black insulated wire on the back of that secondary, if so connecting to either of the two pins or the black wire would give the HV output of that secondary.

Remember that that transformer can only give -60kV with respect to ground. The secondaries produce AC that is 180 degrees out of phase, or 120kV differential between them. In the x-ray tube this would produce 120kV x-rays, but once rectified with diodes for a fusor it will only give -60kV peak DC. The secondaries can not be connected in parallel as this would cause a short, nor can the core ground be floated as it would arc to the primary.

I would also recommend what others said about going with a spellman supply, they are pretty common on ebay for a reasonable cost and will give you a much nicer, regulated DC output with short/arc current limiting. Here's a -30kv one, though I'd hold out for a -40kv one with at least 5mA output (the PTV40n200x2113) is a nice supply that will definitely give you detectable fusion.
http://www.ebay.com/itm/Spellman-PTV30N ... SwyWZZQHPl