On the accelerator front - really just an oversized ion gun - the out gassing has improved further: less than 100 microns/hour for the entire system with the new gun/accelerator tube. Decided to try the turbo and the system pumped down to 5*10^-5 torr in under 5 minutes (from 500 microns existing base pressure. This is similar to my best previous performance so leakage issues are under control - for now. Getting into the mid 10^-6 torr is another matter and I'll let it run for a while to see if/now long to get to the upper 10^-6 torr.
Again, first light is once again doable in the not too distant future if I can resolve the high voltage issue. Also, still have to build the mini-voltage multiplier for the internal, battery operated 25 kV deuterium ionizer. That will be a relatively easy build now I have the parts and know-how. I plan to put that in a small tube and fill that with oil, as well. Will simplify volt arcing issues inside the accelerator globe. Also, have to order the Einzel lens collector plates. These will be plastic with a metal coating. A lot easier both to install and in weight on the accelerator tube.
Been at this point before - that is, before new issues de-railed me and major rebuilds occurred. Again, three steps back, four steps forward. Wish it had just been one back and two forward!
Post edit: the system was hung up on 1.0/1.1 *10^-5 torr so I explored the accelerator tube/fittings etc and no luck. Couldn't find a leak. So, I check other locations (these have been checked before and withstood 5*10^-6 torr) and of course, a new one occurred; a window port for the beam target had its O=ring leaking a little. Some alcohol forced it to 9.5 *10^-6 torr.
So I shut the system down, back filled with dry air, and disassembled the offending KF joint. Carefully examined all surfaces and all seemed good. Then cleaned off all the surfaces and O-ring. Used some high vac grease (put on, then wipe off - while I generally avoid using that stuff, sometimes I just give in. The o-ring/surfaces looked perfect so I decided to try a more drastic step) and re-installed. Will try again.
Nice (not) when a previously sealed connector springs a new leak ... .
Post, post edit: success to start. After less than 45 minutes (from atmosphere, no less) the system (accelerator tube) hit 9*10^-6 torr. I will say, the use of a can of dust off (compress gas for cleaning key boards) really works well for high vac leak detection! That was a great suggestion!.) Very pleased by this result.
Add on post to the post, post edit - the system reached 6.1*10^-6 torr after an hour and half. Sufficient for deuteron work so I'll stop at this point and worry about the high voltage systems (one is a simple build for the deuterium ionizer, the other is more art, apparently, than science. Creating the high voltage for the electric acceleration field has been up/down even within five minutes!) Still, progress is progress and getting the new accelerator tube to sufficiently low vacuum to operate is a nice goal to check off. Still, amazing the number of techniques one has to use to deal with leaks.
Maybe dealing with the Van da Graff will run somewhat more smoothly (hasn't in the past; hence, the VM project-which has become its own disappointment) ... not going to believe that one- I think I will make a new, better belt for the VdG (since the company that made it is out of business I've no choice in the matter. Still, a somewhat wider belt with better material properties might solve most the HV problems - then again, that will not be known until I manage to get to that point; once more, another project, new skills to master and problems to solve - these sub-projects to enhance/improve an existing system is getting old.)
Relative to that program, I've tried installing a number of HV static pick ups/corona generators (pins/needles/screens/mess/high current braided cable (to name the major ones) but really most have failed and few perform as advertised - again, apparently art, not science. Even the 25-30 kV sprays to develop a positive potential on the belt has been a rather depressing no effect on VdG performance - strange.
Well, back to the small VM supply - order the parts I will need for the belt & accelerator tube and do more waiting.
Electro-Static Linear Deuteron Accelerator
-
Dennis P Brown
- Posts: 3187
- Joined: Sun May 20, 2012 10:46 am
- Real name: Dennis Brown
-
Dennis P Brown
- Posts: 3187
- Joined: Sun May 20, 2012 10:46 am
- Real name: Dennis Brown
Re: Electro-Static Linear Deuteron Accelerator
Well, a few up dates on trying to finish my deuteron accelerator project (or at least, just get to first light ...):
First off, the project was delayed for good reasons. I was rather busy last week since my daughter (Jeannette, who some of you meet at Richard's place during the previous year's "forum") was home from MIT for a few days. This was the only time she could visit me this year since she is working full time for a Professor @ MIT all of this summer. Very glad she is working in her chosen field (theoretical Physics) but very sorry I cannot get more time with her this summer ... .
On the deuteron accelerator front (or also called an ion gun on steroids) I just received the new low voltage (3 kV) battery operated power supply (boy, are those things delicate - one mistake and the power transistor fries instantly - very bad design. I've order some of these transistors so hopefully, I can than fix these darn units when they do fail - these things border on being junk.)
The voltage multiplier for the accelerator's own ion gun is now complete, sealed in oil and works great (easily achieves 25 kV using the a fore mentioned HV supply.) The cap/diode stack of the multiplier system fits nicely in a small plastic bellows tube (just the end piece of a plastic drain pipe tube - what's nice is that a KF-25 vac plastic end cap covers fit's perfectly on one end of the plastic pipe!) The complete unit works far better than I had hoped (at least this voltage multiplier system does ... one nice thing about building voltage multiplier units is that I now know a bit more about their problems/limitations and issues. I guess that really is a good way to learn about real world issues, sometimes.
While this unit really does not need oil coverage to operate well, by placing the HV multiplier stack in oil anyway I can better enable all the system's pieces - the 12 volt lead-acid battery, HV power supply, voltage multiplier, rheostat, low and high voltage wiring - to fit nicely within the stainless steel globe while significantly lessening the danger of any flash over by the really high voltage output; the issue is that all these pieces in the globe are rather a tight fit; besides the metal surfaces of the globe itself, all the wires are just too close for comfort with this HV unit.
This SS globe also fits on the end of the deuteron accelerator tube and contains the ion gun/deuterium gas line and the rather large ring magnet for the gun. Since the globe will be charged to 150 - 250 kV (if I can get the Van da Graaff working again like it use to do!), this globe must float (i.e. be electrically isolated) in the "air" so all this weight must be carried by the end of the accelerator tube.
Speaking of the VdG, I have made a series of replacement belts for the unit and look forward to testing them this weekend. This so-called "minor" mini-project has been more of a pain than I thought (or the article prepared me for.) Learning to properly cut and then piece together/glue these belts is a bit more complex than I ever imagined - getting the length correct is really an issue. The new belt material does not stretch at all so getting the exact length is very critical and, of course, more difficult to determine than I realized. Glade I had a lot of the material ... .
If this new belt does not fix the problem with the VdG performance issues than I guess I will be forced to return to my alternate power supply approach and restart backup plan #1 again. One good thing that came out of my failed attempt to build a 400 kV voltage multiplier stack is the unit I did build easily reaches + 60 kV and works well as an ionizer for the VdG belt spray system (this controls VdG polarity - rather critical if one wants to accelerate the deuterons rather than electrons ... .)
The "sub" project for the new plastic collector plates - i.e. to charge the accelerator Einzil lens - has developed into a major issue of its own (what else is new) since these "mirrored" disks are insulated by "paint". Did not see that problem/issue coming - so, I will now attempt to vapor coat the plastic disks (paint side) with some copper in a few days - really need that to work since my regular copper plates are a bit heavy and weight on the accelerator tube is getting serious.
So far, not a single subsystem with this accelerator project has run smoothly - each and every one of these support systems has become its own mini-project and major headache ... . I guess that is SOP for any system of this complexity but I think an accelerator just seems to attracts far more serous problems than most other projects I have read about here. While I am learning a lot as a result, I am starting to realize that assuming people's designs as posted in articles, just will work as well as they claim. I do believe this is for a number of reasons - most, honest errors but still I feel careless. For instance, I now realize that for some of the posted accelerator projects that one finds online, that their HV power sources just didn't work any were near as well as they think. Also, for the few projects that did work, they left out a host of problems/issues that they did end up facing in achieving their working equipment but just wanted the project to appear faultless.
I think I'm starting to understand ITER's real issues ... lol.
First off, the project was delayed for good reasons. I was rather busy last week since my daughter (Jeannette, who some of you meet at Richard's place during the previous year's "forum") was home from MIT for a few days. This was the only time she could visit me this year since she is working full time for a Professor @ MIT all of this summer. Very glad she is working in her chosen field (theoretical Physics) but very sorry I cannot get more time with her this summer ... .
On the deuteron accelerator front (or also called an ion gun on steroids) I just received the new low voltage (3 kV) battery operated power supply (boy, are those things delicate - one mistake and the power transistor fries instantly - very bad design. I've order some of these transistors so hopefully, I can than fix these darn units when they do fail - these things border on being junk.)
The voltage multiplier for the accelerator's own ion gun is now complete, sealed in oil and works great (easily achieves 25 kV using the a fore mentioned HV supply.) The cap/diode stack of the multiplier system fits nicely in a small plastic bellows tube (just the end piece of a plastic drain pipe tube - what's nice is that a KF-25 vac plastic end cap covers fit's perfectly on one end of the plastic pipe!) The complete unit works far better than I had hoped (at least this voltage multiplier system does ... one nice thing about building voltage multiplier units is that I now know a bit more about their problems/limitations and issues. I guess that really is a good way to learn about real world issues, sometimes.
While this unit really does not need oil coverage to operate well, by placing the HV multiplier stack in oil anyway I can better enable all the system's pieces - the 12 volt lead-acid battery, HV power supply, voltage multiplier, rheostat, low and high voltage wiring - to fit nicely within the stainless steel globe while significantly lessening the danger of any flash over by the really high voltage output; the issue is that all these pieces in the globe are rather a tight fit; besides the metal surfaces of the globe itself, all the wires are just too close for comfort with this HV unit.
This SS globe also fits on the end of the deuteron accelerator tube and contains the ion gun/deuterium gas line and the rather large ring magnet for the gun. Since the globe will be charged to 150 - 250 kV (if I can get the Van da Graaff working again like it use to do!), this globe must float (i.e. be electrically isolated) in the "air" so all this weight must be carried by the end of the accelerator tube.
Speaking of the VdG, I have made a series of replacement belts for the unit and look forward to testing them this weekend. This so-called "minor" mini-project has been more of a pain than I thought (or the article prepared me for.) Learning to properly cut and then piece together/glue these belts is a bit more complex than I ever imagined - getting the length correct is really an issue. The new belt material does not stretch at all so getting the exact length is very critical and, of course, more difficult to determine than I realized. Glade I had a lot of the material ... .
If this new belt does not fix the problem with the VdG performance issues than I guess I will be forced to return to my alternate power supply approach and restart backup plan #1 again. One good thing that came out of my failed attempt to build a 400 kV voltage multiplier stack is the unit I did build easily reaches + 60 kV and works well as an ionizer for the VdG belt spray system (this controls VdG polarity - rather critical if one wants to accelerate the deuterons rather than electrons ... .)
The "sub" project for the new plastic collector plates - i.e. to charge the accelerator Einzil lens - has developed into a major issue of its own (what else is new) since these "mirrored" disks are insulated by "paint". Did not see that problem/issue coming - so, I will now attempt to vapor coat the plastic disks (paint side) with some copper in a few days - really need that to work since my regular copper plates are a bit heavy and weight on the accelerator tube is getting serious.
So far, not a single subsystem with this accelerator project has run smoothly - each and every one of these support systems has become its own mini-project and major headache ... . I guess that is SOP for any system of this complexity but I think an accelerator just seems to attracts far more serous problems than most other projects I have read about here. While I am learning a lot as a result, I am starting to realize that assuming people's designs as posted in articles, just will work as well as they claim. I do believe this is for a number of reasons - most, honest errors but still I feel careless. For instance, I now realize that for some of the posted accelerator projects that one finds online, that their HV power sources just didn't work any were near as well as they think. Also, for the few projects that did work, they left out a host of problems/issues that they did end up facing in achieving their working equipment but just wanted the project to appear faultless.
I think I'm starting to understand ITER's real issues ... lol.