phys.org reports on a theoretical advance in magnetism:

A general property of magnetic fields is that they decay with the distance from their magnetic source. But in a new study, physicists have shown that surrounding a magnetic source with a magnetic shell can enhance the magnetic field as it moves away from the source, allowing magnetic energy to be transferred to a distant location through empty space.

The basis of the technique lies in transformation optics, a field that deals with the control of electromagnetic waves and involves metamaterials and invisibility cloaks. While researchers have usually focused on using transformation optics ideas to control light, here the researchers applied the same ideas to control magnetic fields by designing a magnetic shell with specific electromagnetic properties.

Although no material exists that can perfectly meet the requirements for the magnetic shell’s properties, the physicists showed that they could closely approximate these properties by using wedges of alternating superconducting and ferromagnetic materials.

The Polywell depends greatly on advances in magnet technology. This approach may be applicable, I don’t know.

A practical realization of a magnetic metamaterial still requires all the inconvenience of superconductors which tempers my enthusiasm. Still, this idea glimmers with potential.

Also, I bet I could build and test one. In fact I have almost all the materials on hand. Submit your ideas for an experiment in the comments.

FIG. 4: Enhanced magnetic coupling of two dipoles through free space. In (a), magnetic energy density of two identical cylindrical dipoles separated a given gap. When separating and enclosing them with two of our shells with R2=R1 = 4 [(b)], the magnetic energy density in the middle free space is similar to that in (a). When the inner radii of the shells are reduced to R2=R1 = 10 [(c)], the magnetic energy is concentrated in the free space between the enclosed dipoles, enhancing the magnetic coupling.

I’ve been thinking about it ever since.

Here is a brief book report.

tl/dr

• There are two causes to the decline of a civilization: loss of energy and loss of energy quality.
• Peak oil is happening now, not 100 years from now.
• Falling supply paired with rising demand leads to ever rising oil prices, moderated only by damaging demand reduction.
• Post peak oil might bring economic depression or collapse.
• Gave me a new appreciation for oil. Stuff is useful – foundation of our modern world.
• Introduced me to energy returned on energy invested (EROEI)
• Introduced me to energy quality. See also exergy.
• Unconventional oils have a lower energy quality.
• Upside: rising oil prices will force us off oil, like it or not.

Peak Oil

At some point in the last decade I learned about peak oil. It seemed inevitable, but 100 years away.

“Energy Civilization: The Zenith of Man” argues that global peak oil happened in 2005.

Although it is up for debate whether we are post peak oil,  we only know for sure after it has happened.

Peak Cheap Oil

While it’s true that there is a lot of oil left in the ground, the easy, sweet oil is long gone. What’s left is increasingly sour, deep, tight, low EROEI, and low energy quality.

More expensive extraction = more expensive oil.

The oil price shock of 2008 was our first taste of demand bumping hard against supply.

So basically you have a situation where oil supply constraints put a cap economic growth.

Debt based economies don’t work in reverse. I image there would be a *cough* discontinuity in the face of persistent negative growth.

Collapse

Peak cheap oil could lead to some kind of economic depression or collapse. Look out for the burgeoning genre of collapse fiction.

I will leave it to the doomers to fill you in on the collapse discussion.

Oil is Useful (and our world is based on it!)

Ignore for a moment the negative externalities of oil: pollution, co2 emission, resource conflict, etc; and consider the utility of oil:

Transportation and construction totally depend on oil. Nothing comes close to oil’s energy density, which is especially important when you are taking your fuel with you.

Almost all plastic comes from oil.

Oil is a primary feedstock for chemical and medical supply industries.

Most frighteningly, our food supply depends heavily on natural gas for fertilizer, farm equipment, produce transportation, etc. We use 10 calories of oil to make one calorie of food.

Energy returned on energy invested (EROEI)

So lets take a break from the dooming and look and some interesting physics.

Energy returned on energy invested (EROEI) is the ratio of the amount of usable energy acquired from a particular energy resource to the amount of energy expended to obtain that energy resource.

When we first started drilling for oil it took one barrel of oil to extract 100. So an EROEI of 100.
Over time the EROEI of oil has dropped as we have extracted the easy stuff.

Note that if EROEI drops below 1, you are just wasting your time (and energy).

Some unconventional oils like tar-sands have such poor EROEI that using them may just be an exercise in pollution.

Energy Quality

Energy quality from best to worst:

liquid, gas, solid , field (nuclear, wind, solar)

Upside: We use less oil

Many feel we should use less oil. We will be forced to, like it or not.

See Also

• The Oil Drum
• M. King Hubbert

EDIT: Fixes links in TL/DR

Received a 3D printed ceramic calibrations piece from shapeways. As you can see the glazing adds about 0.11mm to the surface:

By Mark Suppes

It’s as though instead of running one experiment a thousand times, we run a hundred slightly different experiments ten times each.

In a word, the three main problems with the old polywell assembly are alignment, structural integrity, and vacuum compatibility. I designed a new assembly which should remedy these problems. instead of multiple separate components, it will be one solid piece of 3D printed ceramic which include a core, acclerator anode, hot cathode, and langmuir probe, all bolted to the 8” conflat flange:

The two feet (bottom left) will be bolted to the conflat flange.

Close-up of the hot cathode holder:

The cathode holder is actually two pieces which sandwich two 2o mm lengths of 10-gauge solid copper wire between them into the inside grooves (A). The grooves on the outside of the cathode holder accept zip ties which will hold the copper wires firmly in place (B). Once the wires are secured, the whole thing is put into place against the left column, and another zip tie is slipped through the hole (C) on the extreme left of the cathode holder and looped around the column. This connection will be strong  enough to prevent the cathode holder from moving during setup/normal operation.  A light bulb filament, serving as the cathode itself, is soldered to the ends of the copper wires.

Close-up of the anode holder:

The anode, a copper cylinder,  is put into the crescent moon shaped space (A), and a zip tie goes around it and through the hole (B), and secures it to the assembly.

Langmuir probe holder:

The langmuir probe fits int the groove in the cylinder (A), and attached with a zip tie or perhaps teflon tape. It extends into the center of the core, indicated by the blue sphere (B). The cylinder is oriented and positioned such that the langmuir probe will extend into the center of the core.

Here’s the new langmuir probe:

The new langmuir probe is a strand of wire inside a very thin ceramic tube. The 9-volt battery on the right is for scale.

Core

The coils fit into the cavities in the core, and then covers go over them. The covers will be secured with zip ties or perhaps hose clamps.

Other than the zip ties and wires, all of this will be made of ceramic. The zip ties will be made of tefzel, a strong, heat tolerant, and highly vacuum compatible material similar to teflon. All wire insulation will be teflon.  This assembly will be heat resistant, electrically insulating, and much more rugged than previous designs. Ideally, we will be able to put it together, put it into the chamber, pump down to much deeper vacuum, and do hundreds of trails without anything breaking. moving, or changing shape.

In order to work at all, this design has to be compatible with the vaccum chamber and conflats that we already had. If one dimension is even slightly off, then the whole thing fails. To prevent that, I first took measnurements of the chamber and flange, and maodeled exact copies of them in OpenSCAD, and built this assembly inside the chamber :

Here you can see the conflat flange (left) and the chamber. Notice that the blue sphere, which indicate the center of the polywell is not centered in the chamber. By offsetting the core slightly, I was able to get more clearance between the walls of the chamber and the core, which in turn allowed for a larger coil radius.

Another pic of the whole thing:

While I have uploaded these models to shapeways, they will probebly not be the ones we actually have printed. This is more of a first draft.

The source code is here

Domenick Bauer

While there were a few interesting results few interesting results, on the whole the experiment was inconclusive, and totaled our electron gun assembly.

The first problem we encountered was the vacuum level. We barely got into the 10^-4 Torr range, and when we turned on the electron beam, the pressure went up into the 10^-3 Torr range. High pressures like these don’t render the experiment impossible, but they certainly don’t help. Ideally, the only particles in the chamber would be electrons, and so everything else just adds to the list of unknown factors.

The e-gun was running normally, giving us readings of about -50VDC on the oscilloscope.

The glow from the hot cathode

For the first shot we did a control. We hooked up one probe to the center langmuir, and one the the shunt resistor on the on power supply, and we got a small well.

So everything was working as expected, despite the unusually high pressure. This is good, but also strange in light of the last test results, in which the charge at charge at the center of the core became less negative when we fired the coils.

Then we switched the oscilloscope probe on the coil power supply to the left langmuir probe, and fired.

Top: Left langmuir probe
Bottom: center langmuir probe

Nothing on the left langmuir. We tried again with more power going into the coils.

Here’s what we got

The charge at the leftmost extreme of the well is about -3VDC, and the charge at the center is about -10VDC. Not surprisingly, electron density has some relationship to distance from the center of the core. We intend to eventually define this relationship precisely, but to do so would require much more data.

Notice how even before the coils were fired, the top line is a slightly below its zero point (indicated by the crosses at the left of the screen). This means that for some reason, the left langmuir is brought to a slightly negative potential by the electron gun, even though it’s not pointed anywhere near the probe

We then switched the oscilloscope probe on the left langmuir to the right langmuir, and fired the core again. The moment we did, we heard a metallic noise from inside the chamber, like a coin dropping onto a metal surface. Can’t be good. This was the readout on the oscilloscope

Not especially meaningful to us.

We rightly assumed that the noise meant our trial was over, so we opened up the chamber.

We found the accelerator anode laying in the bottom of the chamber. The heat from the filament melted the plastic enough for the screw mounted in it to come loose. Everything around it was coated in a thin film of blue plastic, and much of the wire insulation was burnt as well.

Obviously, ABS plastic and rubber insulated wires just aren’t right for this experiment. They can’t take the heat of the cathode, and they out-gas so much that they ruin the vacuum.

Back to the drawing board.

Domenick Bauer

All Photos (1/2)
All Photos (2/2)

The capacitor bank which powers the coils is very lethal; when fully charged, it dumps more than a megawatt into the coils. Needless to say, If I were to accidentally complete the circuit through my body, it would rearrrange my insides. To decrease the likelihood of such an occorence, I’ve done my best to idiot-proof it. Here’s how it looked before:

Pretty easy to thoughtlessly reach in and touch the dangerous parts.

So first, I took a broken shipping pallet that someone across the street was throwing away, and made a box out of it

The box fits nicely on the crate that we’ve been using as a controls stand

I also left the front partially open so they we could get at the controls

With this setup, the only thing you can touch is wood, plastic controls, and the grounded metal face of the box, so it would be pretty hard to blow your hand off.

The next step was making the HVDC out wires safer. (the fat green and yellow ones in the first pic) The way we had it, the only way to dissconnect them was to reach into the supply and unscrew the ring terminlas to which they were connected. Not great. To fix this, I installed a high current outlet onto the back of the box and connected some shorter wires.

The other hole is where the cord which plugs into the wall goes

Took the wires we had and connected them to a matching high current plug

Assembled (and labeled):

So now it’s pretty safe. In fact, it’s so safe that getting into the power supply at all istoo much of a pain. We don’t want to have to move this box every time we need to reset the breaker. To make access easier, I put hinges on the bottom of it (see above), and chains on the side, so it opens like a tool box.

MakerBot mailed me an iron-on patch with some supplies I ordered, so I taped it on for good luck. (top right)

Look’s pretty badass, kinda like a ten-cylinder car engine.

Here’s one more safety feature I added:

If you open the “hood”, the power cord is automatically pulled out. This way, it’s impossible to open the power supply while it’s plugged in.

The coil supply is idiot-proof, but isn’t so locked down that minor repairs and upgrades are too much of a hassle. This is one more step towards a streamlined, repeatable, experiment procedure.

Domenick Bauer

This project is moving into a new phase. Now that we have a working electron gun/polywell setup, it’s time to begin studying the way they interact. To do this, we need a more comprehensive measurement apparatus.

In light of last week’s murky trial results, It’s apparent that a single langmuir probe in the center of our polywell core does not give us a clear picture of the whole well. I think a good first step would be to try to understand how the differs at different distances from the center.

In other words, how is the well different at different points on the red line?

Before I try to answer this question,  I want to make sure that each of the six coils behaves in more or less the same way. In other words, I want to make sure  If the red line above was pointing in the direction of the left coil instead of the right one, it would made no difference. I’m going to call this a symmetry test, because it will reveal whether or not the well is electromagnetically ”symmetrical” about the x, y and z axes.

The symmetry test will work like this: Two more langmuir probes into the core, one on the extreme right of the chamber, and the other at the extreme left.

Right Langmuir

Left Langmuir

If our oscilloscope readings from the two probes are the same, then we may safely assume that the faces are interchangeable.

We’re rapidly running out of feedthrough pins

Core, from the right.

I can’t imagine that the thing’s not symmetrical, because the construction of each coil is identical to that of all others. However, thoroughness never hurt anybody. Also, I’m going to leave the center probe in, so we will be able to compare the center of the well to the edge, which will be interesting in its own right.

Domenick Bauer

We weren’t satisfied with the layout of the inside of the chamber last time. The alignment between the center of the polywell core, the electron gun and the lagmuir probe wasn’t very good, so I upgraded it.

The main advantage of this version is simplicity. It puts the filament, accelerator, and probe, and polywell core all on one flange, rather than two, which means the whole thing can be assembled on a desk and then put into the chamber Much easier than trying to make electrical connections and get alignment right with the thing half way in — something which, rest assured, is a royal pan in the ass.

Another advantege of this one is strength.

Dosn’t look like it, but that’s actually a very strong connection

A big problem last time was that we were unable to get the whole assembly into the chamber without accidentally bumping it a little, and ruining the alignment. This version is more securely attached to the flange, making it easier to keep all the components in the right place and pointing the right way.

Another flaw in the earlier version: The screw which attached the accelerator to the armature extended pretty far inside the copper sleeve which we were using as the accelerator anode, so it was partially blocking the beam.

In this version, that connection has a much lower profile.  I also switched out the old copper sleeve – which was too big and full of holes — for a new smaller one.

While trivial things like holes in the accelerator probably don’t matter, I’m trying to correct them because at this stage of the game, our goal is to eliminate as many variables as possible before we really start collecting data on a large scale. The cleaner the setup, the better.

We also took Remy Dyer’s advice and grounded the positive side of the DC output going to the hot cathode, in order to maximize the potential difference between the accelerator anode and the cathode.

Then, I pumped down the chamber and tested the electron gun.

If you look closely, it’s clear that all the components are aligned pretty well

The lower line is the voltage picked up by the Langmuir probe. The little cross shaped marker on the left side indicates the zero point. Every box in the y direction is equal to fifty volts, so our electron bean is delivering -50 volts to the Langmuir probe, with almost no AC disturbance! Not bad, and this is with the voltage across the hot cathode at about 60 volts out of a possible 120, so it could get even higher.

With this bigger, badder electron gun, we ran another set of trials.

We pumped down.

Hooked everything up.

And took our first shot.

As before, the lower line indicates the voltage on the Langmuir probe at the center of the Polywell core, where the potential well should be. Instead of a well, we have a hill! The magnetic fields generated by the Polywell are supposed to compress all the electrons within the core into its center, so the voltage detected by the Langmuir probe should go even lower. Instead, it goes up, from about -50 to -25. Very confusing.

We rant it a few more times, increasing the current sent through the coils each time, which translates to stronger containment fields. The results were similar.

Here’s a strange one where the center of the core seemed to become very positive. We suspected an arc.

Sure enough, we couldn’t get the core to discharge after this, so we worried that we fried the coils. When it was safe to do so, we opened the chamber and saw that there was an arc, but thankfully not on the core.

Evidently, there was a bad connection between this din rail connector and the core feed throughs on the inside of the chamber, and so an arc occurred, and broke the connection entirely.

So that was that for our trial.

It’s left me confused. What on earth could be making our well positive instead of negative, whereas in the last trial, we got good, negative wells?

Domenick Bauer

During the first trial, our langmuir probe told us that our electron beam intensity was fluctuating at 60 Hz.

This is a problem, because one of the main things we are trying to study is the way changes in beam intensity affect potential well depth, so we want a steady intensity. The frequency of the fluctuations suggest that the AC-powered hot cathode is to blame.  I don’t totally understand the details of how a hot cathode running on AC 120v 60Hz translates to this waveform:

data from the langmuir probe displayed on the oscilloscop

The important thing is to prevent it. To do that, I put a full wave bridge rectifier in the power supply. It converts the AC coming from the wall to DC

It has three essential components.

1) The bridge rectifier

This change the AC sine wave into a waveform expressed by the function abs(sin(x)):

Better, but still not steady DC.

2) The filter capacitor

This gets rid of the ripple. you could compare the capacitor to a bucket with a hole in the bottom. Even if I vary the rate at which putting water into the bucket, the rate at which it come out is always going to be more or less the same, provided that it is sufficiently large compared to the volume of water going in.

However, its impossible to get an absolutely perfect DC output with this setup, because the ammount of charge on the capacitor does affect the voltage at which the current comes out.

This 680 uF capacitor takes away enough of the ripple for our purposes:

the output of the power supply when hooked up to a light bulb

3) An isolation transformer

Usually, the diode bridge and the capacitor would be enough, but our AC isn’t coming from the wall, its coming from a grounded auto transformer. this is a problem because the rectifier only works if the AC input is floating. A transformer with an equal number of primary and secondary wingdings accomplishes this without stepping the voltage up or down.

Nest step is to test it in the chamber.

Domenick Bauer

Today, we tested the electron gun in tandem with the Polywell core. Right now, our goal is to simply understand effect the e-gun has on the potential well, if it has any effect at all.

We had the pump running since 3AM the night before, and so by about 2PM today, we had a vacuum in the 5 x 10^-5 range.

Not super amazing, but certainly good enough for out purposes.

First, we mounted the power supplies in the rack.

Hooked them up to their proper feed-through pins.

Attached the langmuir probe and the shunt resistor to to the oscilloscope, allowing us to monitor the potential well depth and current going through the coils simultaneously and in real time.

Then we began testing. The coils in the core worked great.

The spike on the top line is the power supply’s capacitor bank discharging. The smaller spike on the lower line is a current induced in the langmuir probe by the sudden appearence and dissappearence of a magnetic field generated by the coils in the core. So the Polywell works.

Then we tried the electron gun, and it didn’t work at all. the filament was glowing, and we were getting high voltage on the accelerator’s feedthrough pins, but no reading on the langmuir probe.

After extensive thinking, speculating, and white-board writing, we decided we had to open the chamber up to see if the connections to the accelerator were right.

Here’s what we found

That’s your problem right there, ma’am

It’s a little hard to see, but a gray plastic piece which connects the core to the feed-through pins was right in front of the accelerator, totally blocking the beam.

Funny how sometimes the causes of problems are so obvious that you don’t even think of them.

Anyway, I got that fixed, tried it again, and got a beam. The readings on the langmuir probe attached to the multimeter were more or less the same as those from the last test. When we attached it to the oscilloscope however, things were a little more complicated.

The beam intensity was not static, but periodic. It fluctuated with a frequency of 60 Hz, pointing to the AC current which powers the hot cathode.

We expected something like this, because the availability of electrons to accelerate fluctuates with the AC powering the hot cathode.

Ideally, our electron beam would be have a perfectly even intensity, because then we could eliminate it as a variable.

Fixing that would involve rectifying the AC, a major upgrade to the power supply, so we decided to leave that for another day and run the experiment.

Here are some of the results

A really good one. The downward spike on the lower line signifies a a potential well. Nice!

Here we see a well, but it’s at the wrong time, it seems to have appeared just after we pulsed the core.

Here’s a strange one in which the Polywell core pulse seems to cause some change in the voltage on the langmuir, but not a well.

This one really demonstrates why the periodic electron beam is such a problem. The top spike came at a moment when the langmuir probe was reading zero. This means that there was no beam when we pulsed the core, so it’s no surprise that we just got an induced current.

The most tantalizing and baffling run we did. The well appears to be extremely deep, greater than 100V, but it’s unclear whether thats credible, because there’s so much other confusing stuff going on.

All in all, our results are little confusing, but good. We were able to create the well, which is a big win, but we weren’t able to do so consistently. In order to really study how the well is affected by tweaking variables, we need consistent baseline well to compare against.

Domenick Bauer