Fusor Forums

Stick with it! you will get there with the kind of effort we see here.

As a lone wolf with no internet and no fusor.net and being the first amateur fusor builder, it took me 2 1/2 years from beginning until fusion.

Richard Hull

Thanks Richard. Meaningful words coming from you, I appreciate it. Slow & Steady wins. Usually

While you're here, take a look at something I dug up when going through some of my archived Tesla material... these were from around 1991 or 1992 apparently. Time flies...

Dave

Yes, them were th' days. Once I worked up the last magnifier, (10E), as part of the TCBOR around 1997, I started my early fusor work which overtook coiling and I changed the name to HEAS around 2000 to encompass more cool show and tells in the world of high energy.

The VHS tapes are now distributed as DVD's of course. I actually stopped advertising them about 5 years ago.

Richard Hull

Well, it's been a while. New contract, new vehicle, new roof, and gutting my living room for a complete renovation. And yet I found time to seriously upgrade my fusor with a fantastic little vacuum chamber and high voltage feedthrough that will support my efforts well past "demo" fusor levels. Just mounted the assembly back into the File Cart today, now I need to rewire the HV feed and get a longer vacuum bellows and a few adapters. I also have a second Edwards WRG coming so I can verify vacuum levels between the two. More when I have something significant to show

--Dave

Looking good. Getting back to an old effort temporarily set aside is always fun and you have had time to muse over improvements and make them happen. Given time and some retrospective thought, we can easily see improvements that can benefit the effort and make things work better.

This is one of the benefits of slow going.

Richard Hull

Progress continues, thanks to my machinist friend, Scott Walker (no, he's not running for office! ) Scott does great work. Anyone else want a Deuterium Generator like this one? It's just a consolidated version of the one depicted in the forum thread for Deuterium Generation, but custom made to look cool Polycarbonate and Stainless Steel. VERY tight tolerances, oil won't leak out of this! PM me if anyone is interested in any.

Nice! Although I'll bet oil will leak out of the bottom unless you plan to solvent weld the cylinders to the base.

I did, in fact, seal the cylinder bases. Nothing can make a futuristic looking cool thing look like old tech faster than oily dust

Very well done and professional. Thanks for both the posts and photo's.

Deuterium Generator installed on the portable demo fusor...

Finally... Some photos of the demo plasma in the File Cart Fusor. I still have a lot to do, mostly re-installing the vacuum gauges and making a PC board for the microcontroller that will automate and monitor everything... But I couldn't wait any more, so I just twisted some wires together and ran it up. Works pertty well. The glow of the plasma is beautiful, the photo doesn't quite catch the lavender hues. So now... on to a test run with hydrogen from light water... then Deuterium.

I'm dig'n the red foreground (led somewhere I assume) on the white background. Neat picture.

Lol... This is my portable demo unit, so I have all sorts of lights on this. The red light was good timing... It's the HV Enabled Warning Flasher that is mounted atop the white post, visible in the upper picture, upper right corner.

Dave, I have placed you on the Plasma Club lisitng. That is a very nice looking rig. It looks capable of going all the way.

Richard Hull

Thank you Richard, I'm honored to be listed among such fine company!

Looking forward to the next steps.

Dave

https://youtu.be/cpzH6Cx2SPw

Cathode grid heating, plasma extinguishment at highest vacuum, and re-bloom after vac pump turned off. A little tedious to watch, but interesting if you're so inclined.

Voltage I'm estimating at 7500, pressure not measured yet.... just me playing with voltage, vacuum, and making my stainless steel grid glow:

https://youtu.be/cpzH6Cx2SPw

https://youtu.be/oIlBSijWj0k

Melted my first cathode... Made a new, larger one. In playing with vacuum and voltage levels, there were some very distinct rays or jets of plasma as I passed through a point of the vacuum... is that "star mode", or just some escaping plasma exiting through the grid aperture?

NEXT PHASE: X-RAYS

ZVS Driver paired with fat flyback from amazing1.com. Schematic & PC BOard Mask included if anyone wants. Using IRFP250 MOSFETs, but I hear IRFP260s are better... If the 250s work well, I'll try the 260s.

Note the FAT traces on the PC Board, combined with a thick solder slathering over all the high current runs. This circuit can sling tens of amps into the flyback primary, so the runs have to be fat as possible to keep them from cooking themselves off of the board.

I'm hoping for >30kV at >20mA to get me into real fusion range from my current half-side NST 7.5kV 30mA demo supply using the 15kV 60mA unit I just got... it'll make a nice Jacob's Ladder

The next phase of my Fusor will be this ZVS supply, and I'm expecting to be able to get a fairly hefty X-Ray flux out of my 4" viewport at max V & A once I tweak out the issues...

Videos of the arc this puts out at the moment are here: https://www.youtube.com/watch?v=Zn5Xdoe08SU

It only works intermittently, and I have posted in the HV section for some assistance as to why... I have to physically POKE the primary coils to get it to jump into action. Number of turns in the primary? Capacitor issues? Torroidal Inductor issues? Need help from smarter-than-me people.

Just a few revisions to the Deuterium Generator - the small inner diameter of the crossover dropdown tubes made it so that the PEM cell had to generate too much pressure to displace the vacuum oil. So I put in larger (0.25" OD x .005" wall thickness) stainless steel tubes. The gas line tubes are fine, only the crossover needs the adjustment. I also added a terminal block for the electrical connections so I don't have to keep bothering my PEM cell. Adding this to my historical post archive...

Finally had the time to get the High Voltage Guard (formerly a KitchenAid Polycarbonate Store Display) installed, and then the High Voltage Divider for the Monitor... and of course, the Monitor Panel. I have been unhappy with the video monitor due to the poor quality of the cheap camera I used which couldn't seem to pick up the colors, or even the difference between plasma and background light for that matter, so I replaced the video monitor for now with the panel shown in the photos below. I'll put some $$ into a real camera setup later in the process, when I have to worry about X-Rays and Neutron Flux... The panel displays the grid voltage (I have to relocate the decimal point, I have it one off) - in the photo it's showing -8800v; the grid current is showing 24mA (I have a special 15kV 60mA Non-GFI NST from Amazing Devices, Amherst, NH), and the vacuum output is 7.16 (which calculates to 41 militorr). It also displays the logic voltage (5.08) and I have to connect the last meter to 12Vdc). I also have switches now to activate the vacuum pump & high voltage. Much cleaner operation and I no longer have to guess at voltage and current being delivered to the grid. Plasma shown is atmospheric gasses at the V & I indicated. The voltage divider is a 100 Meg and a 1k, with a neon across the 1k, and numerous grounding points for the ground lead along the run, plus twisted-pair on the wire.... just in case any ground fails so it'll arc over rather than energize/cook anything (like me) if the 100Meg ever fails/arcs.

I'm now actively building the Neutron Detector based on the really nice PMTs I got from Richard. I found perfectly sized aluminum water bottles that I can stuff the PMTs, Mu-Metal Shields, Scintillator Crystals and HV Power Supplies into so it will be optical-photon-proof and should only detect the fast neutrons the BC Scintillator is designed to pick up.

I might not get much time to move forward on this project... but I do take advantage of the time I do get!

Neutron Detector build underway.

Using Richard Hull's Last Two PMTs!

Burn-in testing of a few different HV Supplies for the PMTs. These guys run up to around 1800Vdc, not bad for $8 eBay Hong Kong specials. Pictures show voltage running around 1500Vdc through a 10M/1k voltage divider.

I'll be using BC720, I know it's got a low efficiency... but I like the concept. And I get to play

More pics to follow of the nicely machined-to-match-the-PMT scintillator plastic, etc. My machinist is fabricating a really nice housing.

Dave, looks like you are ahead of me on biasing PMT's.

You are probably over-volting your 10 megohm metering resistor. I bet its rated working voltage is 350 V (see https://www.seielect.com/catalog/SEI-CF_CFM.pdf).

Each resistor series is rated for max power and max voltage. For very high resistance values (and/or low duty cycle pulse applications), the voltage limit gets you first. If you want your voltage divider to have positive design margins, you could use five or six of the high-value resistors in series, or get HV-rated resistors. Ohmite makes some similar-looking resistors (Mini-Mox) whose 1/4 and 1/2 watt sizes are rated at 500 and 1000 volts. http://www.ohmite.com/cat/res_minimox_200_300.pdf At 1 watt size you can find resistors rated for 10,000 volts, as presented here by John Futter: viewtopic.php?f=11&t=10332&p=70119#p70119

Hi Rich,

I bet you're right!

This was just a test setup for a burn-in. Are you suggesting that the measurements may be inaccurate? I've not usually had issues with mA level measurements with standard resistors below 2kV. I am very aware of the resistor issues/requirements when measuring my fusor grid voltage/current, but for testing my PMT supply (an order of magnitude or more lower than fusor supply) for drift over time, I am admittedly being a little less than impeccable

Since ultimately my serious testing will be mid-range biasing the PMT and watching the output on my scope with a low-level fast neutron source irradiating the BC720 bonded to the PMT, I only need to be in the ballpark initially, and be able to distinguish neutrons from background reliably. I have no plans to continuously meter my PMT supply once I dial the voltage in to get best neutron response from the PMT. After that, amplification, pulse shaping and counters will be designed in.

All that said, am I missing something important? Are you thinking that my voltage measurements are off by such a significant factor by using that 1/4 W 10M that it is creating a false reading? It seems to be correct based on the specified range of the supply and the position of the pot relative to min/max, so at the moment I feel confident that my readings are within at least 10%... but I'm certainly open to the possibility that I'm very wrong... please advise.

Thanks,

Dave

Sorry to be cluttering your post, Dave. I bet the resistor in your picture will be OK for short-term use, and for bottom-line accuracy on the order of 5% as indicated by resistor stripes.

I'm no expert with high voltage resistors. Somebody in another thread did some Googling, and said that excess voltage (without excess power, or flashover between the leads) affects linearity and long-term stability of resistance. I would question a commercial design that exposed any resistor to 5x its rated voltage for extended periods, unless its designer knew how to safely venture far away from the road.

Note***** Few if any PMT's ever need much over 1200 volts for proper operation and most work just under 1KV!! The higher the voltage, the more noise pours into your amplifier system. No one needs super amplified noise!

I am somewhat of an expert on HV resistors. There are high ohm resistors (very special above 1 gigohm); then there are high voltage resistors (also very special above 10kv). The two types are often very separate in construction and very expensive, though today's technology has made both easier to fabricate and this would reduce their price, save for demand for them being near zero as few applications demand either in the modern world of solid state electronics.

Precison is extremely expensive in either type. This is due almost solely due to temperature variability of their environment, (temperature coefficient) which is often a function of the current forced through them.

Common, modern film reisistors are cheap, sturdy and accurate. For voltages under about 5kv I tend to prefer these 3 cent each resistors, (in bulk pricing). For my most common range of 1kv-2kv made up dividers using these types, I tend to prefer a string of 9, one megohm 1/4 w 2% resistors. I measure across a special 10th resistor setup placed at the bottom of this string that is a special set, "net", 1 megohm resistor that connects to ground, (1/10 HV reading). I am careful to use a 100 meg input impedance, digital panel meter set into this lower most, one meg calibration resistor. 2% or better accuracy is easily obtained....Provided.... you tweek the meter leg's potentiometer against a good standard across the HV input to match. I have such a high voltage standard calibrated system.

Such "lower voltage", high voltage metering is found in testing and using, PMT's, Neutron proportional tubes, GM tubes, etc. Yes, 1,000 to 3,000 volts in our biz is a "lower" high voltage!!

All of the good digital panel meters are 0.2 volt meters and it can be a daunting task to put them in a series-parallel situation in this special lower 10th, bottom one meg, "net" resistor. It is left as an exercise to the student to noodle-out this electronic-hack to avoid blowing up the 200mv meter as part of a 100 volt potential placed across this net 1meg reistance metering rig with 1,000 volts across the entire divider.

The result can be a highly accurate and stable 1-2kv meter that will place no more than a 100ua load on a 1kv power supply. Supplies for the above nuclear instrumentation are nefariously low current supplies and will not suffer even a weak loading by normal electronic standards before buckling.

At voltages up to about 20kv, A pack of 100 of these cheap resistors, placed in separated series strings of 10 within a divider ladder is still acceptable, using good practices. Above 20kv special resistors, (expensive), are demanded. Sometimes these very special, HV rated, resistors are found surplus at only $2.00 each. Only a good scrounger can win without spending much money.

The quickie little pigtal divider seen in this post is fine for Q&D, (Quick and Dirty), order of magnitude measurements. Where they fail or lie to such Q&D users is their failure to consider the load on their supply or the impedance of their meter. Remember, accuracy is no better that the distributed net division of final impedances in the divider and the meter is a big, big part of it. In the case of this post, Dave did good for a Q&D setup

I do not like to stress a modern, high ohm, film resistor beyond 200 volts across it or 100ua through it when in a high voltage circuit.

Richard Hull