---------- Forwarded message ---------- Date: Thu, 2 Oct 1997 21:15:20 -0400 (EDT) From: richard hull To: hvlist@Anchorage.ab.umd.edu Subject: Farnworth/Hirsch fusor (II) All, It seems there is some interest in this project. So here goes another installment. Basic fusor structure and design: The simple fusor discussed here involves two spherical grid systems. This is not the only number of grids or types of fusor designs possible. It is just the simplest with the greatest viewing area. This is a basic system, but can be amplified as built with only minor modifications to actually do D-D fusion. To play this game you must have the following, or at least be able to beg, borrow, or buy them. 1. A vacuum pump A tolerably decent one will work. A refrigeration pump will work but not allow you near the "sacred land". (neutron production) I am using a Precision 25l/min unit (.9CFM). The pump should be capable of 1 micron (10^-3 torr) or better in real life. Have enough pump oil on hand for three oil changes. 2. A High Voltage DC Supply This should be capable of 5KV or so for the demo model, but a 2 KV supply will serve well for higher pressures. (above 50 microns). It should be well filtered and be capable of at least 60 ma of current! This is stiff by most HV supply standards. You should be fully metered for both voltage and current. The supply's negative terminal must float and not be ground referenced!!!!! An ideal supply is a crude one made from a 2kv HV microwave transformer (not a grounded Neon) capable of at least 60ma. Four HV diodes in a bridge and a 2uf capacitor @ 4KV will work well. Use a good high watt bleeder of about 10megohms. Bring the voltage up and down with a 5 amp variac. 3. A clear chamber capable of holding and surviving a vacuum of 1 micron. This is a real biggy!!! Bell jars cost hundreds but are safe. Regular glass can implode killing you, the experimenter. I used a large Laboratory dessicator made of Nagalene (about $80.00) from a lab supply house. Plastic outgasses a bit, but with the pump running continuously, it can be made to work well. 4. A willing and capable experimenter mindful of the numerous hazards This is always the toughest of all components to secure. With this project, you can be killed instantly in so, so, many ways! Electrocution. Gas explosions. Being burned severly. Flying glass and metal shards like hundreds of high velocity knife blades are a reality. You can be irradiated. (at very low pressures and higher voltages). Cautions will try to be covered during the discusssions. I don't warrant your safety... only you can work toward that goal. Living to see your fusor work is a goal in itself. 5. A ton of extras...Th' small stuff which can eat a pocket book out real quick, just about the time you think you have it all covered. This means valves, plumbing that won't outgas, vacuum gauges (not absolutely necessary but highly recommended.), clamps, vacuum waxes and or greases, etc. ............ The above requriements should keep out the rift raff, arm chair computer freaks, pipe dreamers, theoreticians, greenpeacers and fraidy cats. ............ A tested and well running fusor should pose little threat to anyone, but a nice wire mesh implosion shield would be a great thing when showing your stuff to the regular "down-at-heel" plebian public traffic. ............ Basic construction part I 1. Obtain a chamber and pump it down. This assumes you have a hose and barb on your pump and chamber. NOTE..Keep the impedance of your lines low!!! I used 5/8" ID vacuum hose which is steel reinforced. I used a plastic 5/8" barb for the hose to chamber interface. Forget the other attachments for now. We are testing for implosion! It would be great if you had at least a Thermocouple gauge. One can be had complete and ready for battle from Duniway Stock Room 1-800-446-8811. ( p/n DTC-531-115/BX - $283.00). Take the chamber down to at least 100 microns (10^-2mm or torr). If you have no blast shield, vacate the room until the lower pressures are reached. This is were the lab dessicator of plastic is a great first chamber. It can't really break and is designed to take a stiff vacuum. The above is a must do, as we must be sure at each baby step that we are reasonably safe and are standing on firm ground to this point. 2. Next, if we haven't installed a gauge on our chamber, it is time to add it. Gauges on or in the lines are not a good idea. They should stare right into the chamber. However you mount the gauge, be sure you don't weaken the chamber by stressing it with over tightened bolts or hardware. Seal with a good vacuum grease. (Duniway catalog DC-150 - $15.00/tube). I used a lot of "o" ring type rubber gaskets found at the local HQ home shops. Pump the chamber down now to test this latest addition. 3. I chose to put on a small teflon bleeder valve (came free with my dessicator). It is handy for taking the chamber slowly back to atmosphere. Add this item now, if desired. Pump down again. Gaskets and grease are the key to good sealing of chamber entries. 4. Finally, put a valve in the pump line. I use a 5/8" pvc and then a 5/8" (clear aperture) ball valve. (Home Quarters) Make sure to vacuum grease this after you remove the grease supplied on it when purchased. Good high vacuum valves cost hundreds. 5. Now you will get a feeling for real leaks and virtual leaks. Pump the chamber down and close the valve with the pump running. Watch your gauge, it will climb back upwards!! This could be a real leak or a virtual leak. Real leaks are cracks, holes, chinks, whatever which leak air back into the chamber. It is actually a good idea to check for leaks as you go above provided you have a gauge. Without a guage, you are somewhat blind here. Leaks can be found by sparying alcohol near the suspected leak and watching a guage. If it goes up in pressure then you have found a real leak. Virtual leaks are no fixes. These are outgassing elements. Some internal components will ultimately outgass with time. Others will never cease to outgass. This is why component selection in a vacuum system is so critical. We are not really hitting good vacuums until 1 micron and this project is designed to work between 10 and 50 microns of so. Thus component selection can be a little more "free". Water and things which absorb water are a big no-no in the chamber. Hopefully, we now have a fully equipped, non-leaking vacuum chamber. For plastic chambers it is important to run the pump rather continuously when in operation. Mine, when valved off drops back about 1 micron every 10 seconds. This means that over a couple of non-pumping days, I still have a good rough vacuum and only moderate outgassing is seen. As the chamber is used,and kept sealed, this will improve, usually. I can pump my chamber back to operating pressure in under 30 minutes now. More to follow. Richard Hull, TCBOR