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Mr. Fusion
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A Larger Pump and More Ranting
October 4, 2002 — 20:59

Well I got the D-16B upgrade on the pump back home today.   Yee
gods, what a beast.  But it sucks like a…  well, let’s not be
graphically lewd.  Got the BFABJ swapped out for a 12" x 12" glass bell jar
and cage.  Much smaller volume and a lot less surface area.  The base
of the TOPS is a about 8 inches or so deep, so the total clearance is 12" x 20". 
More than enough room to to silly things.

A downside is there’s no protection against x rays and such.  Everything
has an upside and a downside.  Spin always imposes polarity, so what can
you do?  Live with it and engineer compromises.

I had a load of work this week, as well as dinner at a friends today.  I was up
’till 11:30 writing code most nights, so I haven’t had much free time lately.  But I
naturally couldn’t wait to pump the sucker down and see what I could get out of
it.  With the larger fore pump, the system dropped to 40 micro torr within
4 minutes or so.  Amazing.  I was at 20 micro torr another 5 minutes. 
I let it run for another 10 minutes and ultimately reached 4 micro torr.


So
I am a pleased puppy.  The cage around the bell jar kinda bites from an
aesthetic point of view, but I can’t believe anyone would even think of putting
the weight of the atmosphere on one of these without one.  Been reading
about electrostatic optics, and managed to find a student copy of CPO-3D (it’s
legal).  I’ll crack that open and see if I can model the simple system I
think I can get away with – i.e. a diode design with a magnetic lens.  The
ultimate energies I’ll be working with will be pretty high, but the magnets are
pretty powerful.

I found a spreadsheet for doing coil calculations.  Very handy. 
I’ll be posting it shortly.  Just to get the field strength of the grade 5
ceramic magnets I’m using takes an awful lot of power.  Trying to get the
field strength from some of the rare earth magnets (11,000 gauss) takes some
hungry power supplies.  And superconductors.  I sure hope that someone
invents room temperature superconducting material REAL SOON NOW.  Or at
least liquid nitrogen temperature superconducting materials.

Got the 2.3" grade 5 ring magnets from
www.allmagnetics.com Tuesday.  Also included are some sweet 3" x .25" x
.25" grade 5 bar magnets.  My thought is that I can replace the rings with
these little puppies and improve my cross section.  Opens it up for pretty
pictures, as well.  We will see.

I also foolishly played around a bit with the 4.5" nasty boys.  Chipped
a couple of them, naturally.  Man, they are powerful.  Not powerful
enough to seriously wound you, but nasty none-the-less. 

I drew up parts for the cuboctahedron chamber.  Simple, but helped me
visualize the geometry a bit.  I’m back on a 4" radius for the chamber. 
If I take reasonable care even someone of my inadequate welding skills should be
able to make short work of it.  In any event, I can probably convince Dave
Leibs to weld it.  He’s been taking welding classes on Thursday nights. 
He wasn’t that bad of an amateur welder when he started, so he should be getting
good here any time soon.  He’s easy to convince to do stuff so if I have
the pieces all made he’d likely be over in a heart beat.

I’m worried about not having enough feed throughs.  I only have three on
the TOPS base, as one is taken by the cold cathode gauge.  Only the
electron gun should require high voltage.  The ion gun I have in mind is a
simple minded electron bombardment type.  Nice diagram in

Building Scientific Apparatus
.  By the way, this is the single most
useful book in the world.  I had a 1983 version sitting around since… 
well, 1985.  Full of darn useful stuff, and highly recommended.

In any event, in the design of
record, the ion gun can
simply use the electron gun’s negative potential to shoot D+ into the
chamber.  Producing the ions only uses 70 volts and I just need to come up
with a lens to focus the ion beam.  That hopefully shouldn’t take too high
a voltage.

So the upshot is that I have to have two high voltage feed throughs. 
Leaving one feed through to route the rest of the wires and the all important
Deuterium gas.  Sounds like T time.  <heh>  No problem.  I
know I’ll have to build a specialized chamber where I can mount the guns some
day.  But my first goal is to just play around with an electron gun, the
magnetic chamber and a whiff of argon or neon.  And make pretty pictures.

And do some experiments on how efficient my simple minded grid is at trapping
electrons.  What I have in mind is measuring the current flow out of the
cusps.  Inject the electrons in, measure what comes out.  Hopefully it
will be within acceptable tolerances.

I have to find time to clear out the section of the workshop where I’ll be
hosting this stuff.  I want to build a low platform at the level of the
TOPS base so I can have some space to work around it.  That’ll be fun.

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