Bench Degree·PLASMAchapter
Appendix A: The Bench
The whole volume’s kit in one place. Every experiment in this book is on this list, so you should never have to stop mid-chapter and wait two days for a delivery. Each chapter names what it needs when it needs it and points back here; if you would rather order once and be done, order from this list.
The first four chapters cost almost nothing. A candle, a comb, a 9 V battery, a multimeter and two pieces of copper wire will get you a measured current through a flame, the effect of a pinch of salt on it, and a fluorescent tube whose electrons are at 11,600 K while its glass is warm to the touch. Chapter 1’s central result costs under $20 and probably nothing.
Then there is one rig, and the rest of the book runs on it. A vacuum-rated jar, a hand pump, an adjustable current-limited high-voltage supply and a ballast resistor. That is about $150 assembled from scratch, it is the apparatus in Chapters 5, 6, 9, 10, 11, 15 and 17, and it is the same jar and the same brake-bleeder pump used in the Refrigeration volume, so if you have that one you are already halfway.
Bought new from nothing, the whole volume is roughly $300, and one optional instrument in Section 4 can add up to $150 more.
Nothing here is specified by brand or by part number. Every item is described by function, range or rating, so the list stays orderable from anyone, anywhere, for as long as the book exists. Suppliers change and a printed link dies permanently. A specification does not.
Section 1: The starter set, for Chapters 1 to 4
| Item | Specification | Rough cost |
|---|---|---|
| Multimeter | Must have a microamp range, because Chapter 1’s flame current is tens of microamps. A 10 MΩ input impedance, which nearly all of them have, matters again in Chapter 15. | $20 |
| Candles and a plastic comb | Chapter 1’s conducting flame, Chapter 3’s salted flame, and Chapter 7’s ion wind target. | owned |
| Stiff bare copper wire | Two lengths of 150 mm (6 in), 1.5 mm (0.06 in) or heavier, as flame electrodes. Plus pliers, because the ends get hot. | owned |
| A 9 V battery | The entire power supply for Chapter 1’s first experiment. It cannot hurt you and that is worth noticing on page one of a book about high voltage. | owned |
| Table salt | Chapter 3 raises a flame’s conductivity by orders of magnitude with a pinch of it. | owned |
| One grape, and a microwave you can risk | Chapter 1’s plasma in a kitchen. Eight seconds, on an upturned ceramic dish, never in an oven you depend on. | owned |
| Fluorescent tube or CFL in a fitting | Chapter 4’s two temperatures: an electron population at thousands of kelvin behind glass you can hold. Plus a compass or magnet, and a small AM radio to hear it. | owned |
| Infrared thermometer | Reads the tube’s glass at 47 °C (117 °F) while the electrons inside it are at 11,600 K. Shared with several other volumes in this series. | $20 |
| A CD or DVD you can destroy, and a cereal box | Chapter 9’s spectroscope, which costs nothing and works properly. A craft knife and black tape. | free |
Starter set total: about $40, and most households have all of it except the meter.
Section 2: The rig, for Chapters 5 to 11 and 15 to 17
| Item | Specification | Rough cost |
|---|---|---|
| Current-limited high-voltage supply | 5 to 20 kV, adjustable, output rated in hundreds of microamps, 12 V input. Sold as a cold-cathode inverter or a small flyback module. Read the safety notes above before buying: the current rating is the specification that matters. | $15 to $30 |
| Vacuum-rated chamber | A chamber sold for degassing resin, or a jar explicitly rated for vacuum. A decorative jar can implode. If you own Refrigeration, this is the same chamber. | $25 to $40 |
| Hand vacuum pump | An automotive brake-bleeder type with a gauge reading to at least 25 in Hg, which is about 85 kPa below atmosphere. That is enough to cross the Paschen minimum, and its inability to do much better is a safety feature in Chapter 16’s terms. | $25 |
| Ballast resistor | High-voltage, of the order of 1 to 10 MΩ, or a spaced series string of smaller ones. Not optional in any box. Chapter 6 Section 3 explains what it does, and the glow-to-arc transition is where equipment gets destroyed. | $10 |
| Electrode feedthroughs | Two blunt-ended stainless rods or machine screws through the lid, 5 mm (0.2 in) apart, sealed with epoxy. Make the gap adjustable if you can. | $10 |
| Sewing needle and a metal ring | The corona rig. The ring about 40 mm (1.6 in) across, or a flat plate. Chapters 1, 7 and 10. | free |
| Kitchen scale | Reading to 0.1 g (0.004 oz). This is how you weigh ionic thrust in Chapters 7 and 14, and how you measure magnetic pressure in Chapter 11. | $15 |
| Spring or luggage scale | To 20 kg (44 lb), for the magnetic pressure measurement. | $10 |
| Neodymium disc magnet | 20 mm (0.8 in) or larger, plus a flat steel plate. Held on a wooden stick, never in your fingers near the jar. | $8 |
| A 12 V battery and a headlight bulb | Chapter 8’s switch arc, with the bulb always in circuit as a load. Fifty turns of thick wire on a nail is the inductor. Safety glasses, because the arc spits molten copper. | owned, or free |
| Probe materials | A length of tungsten from a broken TIG electrode or the support wire of a dead halogen bulb; a glass or ceramic sleeve, which can be a ballpoint barrel; high-temperature epoxy. Chapter 15’s Langmuir probe, and it is the instrument the volume’s subject is named for. | $10 |
| Sweep supply | Settable from about minus 40 V to plus 40 V. Two 30 V supplies back to back will do, or a stack of nine-volt batteries and a potentiometer. Its case must be treated as live, so use one you are willing to lose. | $0 to $40 |
| A 10 kΩ resistor and a second multimeter | Current sense and the second reading for Chapter 15’s sweep. | $15 |
| Discharge stick parts | A hardwood dowel or acrylic rod 500 mm (20 in) long, a 47 kΩ high-voltage resistor or five spaced 10 kΩ units, an earth lead with a crocodile clip, a copper hook, cable ties. Plus a 1 µF high-voltage capacitor to prove the point on. | $20 |
| Graph paper | Chapters 5, 10, 15 and 17 all ask you to plot points and look at the shape. Do it on paper. | $4 |
Rig total: about $150, or nearer $110 if you already own the pump and chamber from another volume.
Section 3: Free, and worth more than most of what is above
| Item | Where | Chapter |
|---|---|---|
| A dead fluorescent tube, a dead CFL, a dead halogen bulb | Your own bin. The halogen gives you tungsten wire for the probe, and the tube is Chapter 4’s whole experiment. | 4, 11, 15 |
| A broken TIG electrode | Any welding shop’s floor. Thoriated or lanthanated, it does not matter here. This is the best probe wire there is and it is waste. | 15 |
| Milk bottles, food tubs, plastic bags | Chapter 10’s surface activation. A water drop on treated polypropylene behaves visibly differently from one on the same plastic untreated, and that is how every printed food wrapper in your kitchen is made to take ink. | 10 |
| A short-wave receiver, or a public one on the internet | Chapter 13 sounds the ionosphere at noon and at midnight. A remote receiver online is genuinely the same measurement and costs nothing. | 13 |
| Space weather data, and your phone’s magnetometer | Published free, updated continuously. Chapter 13 has you watch an event arrive. | 13 |
| 2 m (about 6 ft) of garden hose | Chapter 12 builds the rotational transform out of it, which is the idea that took fusion from an unstable pinch to a stellarator. | 12 |
| A calculator and one sheet of paper | Chapter 12’s Lawson arithmetic. The gatekeeping calculation of a twenty-billion-dollar machine fits on one sheet, and doing it yourself is the fastest way to see which term the money is actually fighting. | 12, 14 |
Section 4: The one expensive thing, and whether you need it
A radiation instrument for your own bench. A Geiger-Müller counter with a thin end-window or pancake tube is about $100 used; an electronic personal dosimeter is about $40. This is the one piece of test equipment in this volume that is about you rather than about the experiment, and Chapter 16 has a box that uses it.
Whether you need it depends entirely on one number. Stay at or below 20 kV with a hand pump, and the X-ray output is soft enough that the wall of the jar absorbs essentially all of it, and you do not need an instrument to tell you that. Go above 20 kV, or fit a better pump, and you need one before the next session, because you have built a small X-ray tube whether you meant to or not. The honest position is that the ceiling is what keeps this bench safe, and an instrument is what you buy when you decide to leave the ceiling behind.
The other item that costs real money is the sweep supply for Chapter 15, at up to $40, and there are two ways round it: two cheap fixed supplies back to back, or a stack of nine-volt batteries with a potentiometer, which is what a great many first probes have actually been swept with.
And if the budget is one item, it is the vacuum chamber. Not the supply, which is $20, and not the pump, which most garages already contain in the form of a brake bleeder. Seven chapters happen inside that jar.
Section 5: What you already own more of than you think
You have made a plasma by accident. Chapter 1 starts from that: a candle flame conducts a measurable current, and a grape in a microwave will produce a genuine plasma ball for as long as you let it, which should be eight seconds.
There is a plasma in your ceiling. Every fluorescent tube and every compact fluorescent is a low-pressure glow discharge with a mercury spectrum, and Chapter 9’s cereal-box spectroscope will resolve its lines well enough to identify them. Every streetlight on your road is a different gas, and once you have the spectroscope you will not be able to stop.
Your phone is a magnetometer, which Chapter 13 uses to watch a geomagnetic storm arrive, and its camera is the detector for every spectrum in Chapter 9.
Your car has an arc in it several thousand times a minute, and Chapter 8 measures a much slower one on a battery and a headlight bulb, with an inductor made from a nail.
Your kitchen contains the entire surface-treatment industry. Chapter 10 corona-treats a milk bottle and proves it with a drop of water, which is how ink is made to stick to plastic film.
And the ionosphere is free. The nearest plasma outside your kitchen starts about 60 km (37 miles) above your head, and Chapter 13 sounds it with a portable radio and a notebook, at noon and at midnight, for a result that would have been a research paper in 1930.
Section 6: The experiments, and where they are
Twenty-eight, and the whole list fits on the kit above.
| Experiment | Chapter | What it costs |
|---|---|---|
| A flame that conducts | 1 | under $20, and likely nothing |
| The grape | 1 | nothing, plus a microwave you can risk |
| Ionic wind, and the safety rule for the rest of this book | 1 | $30 |
| Salting a flame | 3 | nothing |
| Two thermometers on one lamp | 4 | nothing beyond the infrared thermometer |
| Finding the Paschen minimum | 5 | $70, and the rig is reused seven times |
| Walking the zoo | 6 | nothing beyond Chapter 5 |
| Measuring ionic wind | 7 | $40 |
| A generator driven by a candle | 7 | nothing beyond Chapter 1 |
| Watch a switch arc, and then measure one | 8 | nothing if you own a battery |
| A spectroscope from rubbish | 9 | nothing |
| Read your own discharge | 9 | nothing beyond Chapter 6 |
| Measure the sheath | 10 | nothing beyond Chapter 6 |
| Surface activation, and the water drop that proves it | 10 | nothing beyond Chapter 7 |
| Bend a discharge with a magnet | 11 | $8 |
| Measure a magnetic pressure with a kitchen scale | 11 | nothing beyond the magnet |
| Build the twist out of a garden hose | 12 | nothing |
| Do the Lawson arithmetic yourself | 12 | nothing |
| Sound the ionosphere with a radio | 13 | $0 to $40 |
| Watch a space weather event happen | 13 | nothing |
| Weigh the push | 14 | nothing |
| Run the rocket equation on two real missions | 14 | nothing |
| Read the floating potential | 15 | $10 |
| Sweep the probe and get an electron temperature | 15 | $0 to $40 |
| Put a meter on it rather than an opinion | 16 | $40 to $150 |
| Build the discharge stick, then prove why you need it | 16 | $20 |
| If you do one thing, do this one | 17 | $70 if you own the pump |
| The inventory | 17 | nothing |
The five in bold are the ones to do if you do only five. The first measures a current through a candle flame with a battery that cannot hurt you, and the whole book follows from it. The second finds the Paschen minimum, which is the one curve in this subject that explains breakdown, spark plugs, vacuum insulation and why a partial vacuum is worse than either extreme. The third builds a working spectrometer from a disc and a cereal box and turns every lamp you pass into a readable measurement. The fourth puts a wire into a plasma and reads the potential it settles at, on the instrument that carries the name of the man on the cover. And the fifth is a safety device you build yourself and then prove you needed, which is the only honest way to learn that lesson.
Sixteen of the twenty-eight cost nothing at all beyond kit already listed, and six of those need nothing but a phone, a radio, a hose or a calculator. This is a cheap subject to learn honestly, and the reason is that the fourth state of matter is not rare: it is in your ceiling, in your kitchen, in your car, and 60 km (37 miles) over your head.
The safety gear, which is not optional
Wear this for the experiments the book says to wear it for. The reasons are on the Before You Start page at the front, and in the chapter that owns each experiment.
| Item | Specification | Cost |
|---|---|---|
| Clear polycarbonate safety glasses | Worn for every experiment in this volume, because they are the ultraviolet protection and the flying-glass protection at the same time. | $8 |
| Polycarbonate sheet | A piece 300 mm (12 in) square, propped in front of the jar. | $10 |
| Clear packing tape | Wrapped round the jar so an implosion stays in one place. | $3 |
| A shorting bar | A length of bare copper wire with a clip at each end. Left in place while you work, every time. | free |
| A window fan or extractor | Mechanical ventilation, pointing out. Ozone is the reason. | owned, or $20 |
Section 7: Kits
A single collection covering the chamber, the pump, the supply and the ballast, ordered once, is the obvious convenience and it is being worked on. When it exists it will be at benchdegree.com/kit/plasma, and that address is deliberately the only place it will be published: suppliers and product listings change, and a link printed in a book cannot be corrected. The specifications above can be taken to any supplier and will still make sense in twenty years.
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