Jochen's High Voltage Page

The Fusor III project

---------- Forwarded message ----------
Date: Thu, 07 Jan 1999 14:14:24 -0500
From: Richard Hull 
To: HV list 
Subject: FUSOR III


I have enclosed (6) low to moderate resolution 400X600 B&W images of the
new fusor III, which I have been working on over the last quarter year,
but bullheaded to completion with 18 hour workdays while on my 2 week
holiday vacation.

This is an all stainless steel system (316) and is well instrumented and
positions me for heavy neutron production possibilities unlike Fusor II
which was a sort of advanced demo/ultra-lightduty fusor.  Each step
along the way since 1997 has been a well though out baby step.  Each
fusor iteration has supplied me with new knowledge and improved

The power supply for this model was well thought out.  It is capable
within the bed railed supply box of handling up to 25kvdc at 60ma  based
on external transformer.  I am currently just exercising the unit at
around 10kv (just under the X-ray region).  The system uses full wave
rectification and solid state diode of 25kv piv rating at 100ma.  I have
opted for a  .1ufd, 30 kvdc filter cap (ceramic).  The reason being that
anomolous discharge phenomena can quickly blast a grid to pieces.  I
ruined (increased) the surge impedance by inserting a 60k ohm 200 watt
resistor and 1 henry 20kv choke in series with the fusor's hot
terminal.  This will grossly limit and slow down the di/dt to safe

I have a 1.5" diameter pyrex viewport which allows a medical high res
B&W video camera to image the poissor and central grid area.  This helps
with control and limits exposure to the operator to a number of possible
nasties, among which are implosion (eye full of glass), x-ray radiation,
neutron radiation, UV radiation, etc.

The following photos are just a quick overview of what happened up to 1

There are two shots of just the finished fusor chamber by itself.
There is a shot of the fusor in situ.
There is a shot of star mode with white hot tatalum grid struture.
There are two nornal shots of  cold grid star mode at different contrast

My hope is to ultimately hit 60kv or more, but that will require some
fancy pumping to around 10-6 mm and backfilling of differentially
pumping with Deuterium to 10-5mm.
I'll probably settle on diff pumping.

More as the project jels

Richard Hull, TCBOR

Fusor III 28 Jan 1999.............An Update

The fusor III is now performing even better than could be expected.  The
pressures inside due to ion pumping action can take a normal
mechanically pumped 5 micron pressure and send it sub-micron!  At this
level of vacuum I have nursed the system up to 17KV @ 10ma.  This
represents a new high in voltage.

A check for X-radiation indicated, as expected, well below .01 mr/hr.
point contact with case. This is due to the thick stainless steel
spherical casing.  I have no idea where to expect X-ray troubles, but
imagine to be producing neutrons long before the X-rays start making it
out of the fusor chamber.( ~30KV?).

A trip to calibrate my neutron counter is off in the future.  For now, I
will work with air dynamics of the system to become familiar with the
unusual nature of the system control at this level (new to me).  Tom
Ligon noted that I should now be well over the threshold for neutron
production and only a Deuterium gas load is needed to see neutrons.

The chamber wall temperature, as noted by my thermocuple, will quickly
reach 100 degrees F. above ambient.  With a 70 degree room temp., that
will burn you real quickly.

Internal pulsed discharges due to a faulty HV feedthrough destroyed my
TC gauge meter and I have replaced it with a new one.  Be careful of
your TC gauge with extreme fusor voltages.

New photos are enclosed mostly of the machine and myself and one grid
shot at 16KV

Richard Hull

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