DIY: Nuclear Fusor #diy

There’s a nice tutorial on Makezine.com on how to create your very own Nuclear Fusor. Of course there are some harmful elements to this project and I don’t think you’ll get as much power out of it than you would initially think, but it’s a very cool to show off to your friends. Below is a brief description of it’s operation.

The typical Farnsworth-Hirsch fusor has two concentric electrical grids inside a vacuum chamber: an inner grid charged to a high negative potential, and an outer grid held at ground potential. Our benchtop version has a stainless steel wire inner grid, and uses the aluminum chamber walls as the outer grid.

A variac controls the AC mains voltage input to a neon sign transformer, which steps up standard 110V AC to the 10kV range. A homemade rectifier converts AC to DC power to charge the grid.

A vacuum pump evacuates the chamber to a pressure of about 0.025mm of mercury, clearing the playing field so the few remaining gas molecules can accelerate without premature low-energy collisions. A vacuum gauge indicates the pressure inside.

High voltage across the grids causes gas molecules to ionize; that is, they lose an electron and become positively charged. Electrostatic forces then accelerate the ions — mainly O2+, N2+, Ar+, and H2O+ — toward the high negative charge at the center. Some ions collide; those that miss the first time are arrested by the electric field and re-accelerated toward the center for another go.

Guides: Grounding Principles

In a previous blog on supply bypassing, I cautioned that poor bypassing could increase distortion of an amplifier. A reader, Walter, asked an interesting question… where should you connect the ground of a bypass capacitor to avoid problems?

This raises questions regarding proper grounding techniques. Wow. Big topic, but I may be able provide some insight with a couple of simple examples.

Figure 1 shows inverting and non-inverting amplifier stages with unintended, parasitic resistance or inductance in the ground connections (highlighted in red). The nodes A, B and C are all intended to be ground. But if current flows in parasitic ground impedances, these nodes will not be at the same potential. It is these parasitic ground impedances that can allow distorted ground currents to contaminate signals.

 

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