Bench Degree·PLASMAchapter

Before You Start

One page. Appendix A at the back carries the full parts list. Chapter 16 is the real safety chapter of this volume, with the numbers and the reasoning; this page exists to stop you buying the wrong thing before you get there.

The most important purchasing decision in this book is which high-voltage supply you buy, and it is a decision about current, not voltage.

Buy a current-limited module: a cold-cathode or flyback inverter, 5 to 20 kV from a 12 V input, $15 to $30, rated in hundreds of microamps. At 15 kV that will sting you and startle you.

Do not buy a neon sign, oil burner or microwave oven transformer. Same voltage, tens or hundreds of milliamps. 10 to 20 mA is the let-go threshold, where your grip closes and stays closed, and 50 to 100 mA across the chest can fibrillate a heart. That is the difference between a shock you talk about and a shock somebody else has to explain.

Stored energy gets the people who already know about the first hazard. A capacitor that reads zero can recover a lethal charge by itself within minutes, as trapped charge migrates out of the dielectric. The rule is mechanical: short it through a resistor, then short it with a bar, and leave the bar in while you work. Not measured and found to be zero. Shorted, with metal you can see.

X-rays are the hazard nobody expects on a hobby bench. An electron stopping in metal emits a photon whose maximum energy in keV equals your accelerating voltage in kV. No threshold, no off switch, and at 30 kV ordinary glass is not a shield. This volume sets a ceiling: keep the jar at or below 20 kV unless you own a dosimeter.

Chapter 16’s rules, worth pinning above the bench. One hand. Enclose the high voltage. Ballast every discharge. Short it and leave the bar in. Never alone above 1 kV. Ventilate mechanically, because ozone deadens your nose to itself in ten minutes. Polycarbonate glasses on, and sunglasses are worse than nothing because they open your pupil. Twenty kilovolts is the ceiling. Never a chlorinated solvent near an arc, because it decomposes to phosgene. Close the cylinder valve, not just the torch. Discharge stick with a resistor, never a screwdriver. Know where the breaker is, and make sure somebody else does too.

Bench Degree

Get the degree without the diploma.

Learn the material, not how to pass the exam.