Plasma!

September 23, 2018 at 1:55 pm

Last weekend the Fusor produced a plasma for the first time, shown in the photograph below.  That plasma was at a voltage of about 4.5kV and 20mA current.  Pressure was roughly 10 microns.

Plasma is the first sign of a Fusor really working.  It’s not fusion yet, but shows what happens when multiple systems are working in tandem.  In this case, the vacuum pumps and high voltage line, along with related instrumentation.  To strike a plasma like the one shown, the chamber is first evacuated to low pressure (vacuum).  Next, a voltage is applied, causing molecules to be ionised, or electrically charged.  When they become charged, they start flowing in one direction or another (towards the central grid or towards the chamber’s wall) and this is current flow.

The plasma in the picture is coloured purple-blue because the chamber is filled with air being turned into a plasma.  Air is made up of mostly Nitrogen, and Nitrogen glows purple-blue when it’s ionised.

One problem I’m having is that the plasma draws a lot of current for a low voltage.  Ideally I could operate at 20kV without drawing full current (20mA).  However, the plasma shown is already maxing out my supply’s current at only 4.5kV.  I’m told that it takes some tweaking and operational experience to get the voltage desired.  Switching on the turbopump allows me to go up to 30kV, with almost no current though, so there’s no plasma.  This is because of the extremely low pressure… The balance of plasma current, voltage and pressure are largely governed by Paschen’s Law.

Purple plasma in Fusor

This is a significant milestone – fusion is not far away.  It confirms that my high voltage supply is working fine.  Also, a plasma enables me to gauge the performance of my vacuum line as I can infer pressure (roughly) from the plasma current and voltage.