Boron Vapor Pressure

This question of Boron vapor pressure has come up a number of times in various discussions so I think a reference post is a good idea.

From Boron Properties:

Vapor Pressure: 4.6 x 10-4 to 8.5 x 10-3 mm @2200K

From Boron - Yahoo Answers:

Temperature/Vapor pressure:

2348K 1 Pa
2562K 10 Pa
2822K 100 Pa
3141K 1 k Pa
3545K 10 k Pa
4072K 100 k Pa

Constructing a Fusor - Joseph Zambelli

Joseph Zambelli has built a fusor. He starts out with a very nice picture of his device.

This Inertial Electrostatic Confinement Fusion (IECF) fast neutron generator is a complete, easy-to-operate tabletop system. As presently configured, it produces up to 6.75E5 2.5 MeV neutrons per second with an acceleration voltage of 42 KV and a current of 18mA, at a pressure of 11.5 mTorr, with a start-up time of 10 minutes or less. It can easily be upgraded to yield even higher neutron production rates if so desired. This design has extremely low operational costs, and requires only a single 120V outlet for power. It features an 8” UHV Stainless Steel spherical, multi-port chamber evacuated with turbo-drag and rotary backing pumps.

He has another picture and link page here. The link page has links to the following the following sections:

Theory
Construction
Operation
Demonstration System
Further Links

Constructing a Fusor - Longwood University

I just came across this interesting report on the construction of a Farnsworth Fusor by Andrew Grzankowski at Longwood University, Farmville, Virginia.

Over the Summer of 2007, physics major Andrew Grzankowski worked with Longwood faculty member Keith Rider (Chemistry) to construct a Farnsworth Fusion Reactor. Here’s a breakdown of the project.

In the end notes there are a series of links which I am going to reproduce here.

Fusor.net

Original patents (H-M Fusor)[pdf]

Thesis – Carl Dietrich 2007 (MIT)[pdf]

Tom Ligon – The world’s simplest fusion reactor, and how to make it work[pdf]

Todd Rider – Is there a better route to fusion? (MIT)[pdf]

Prof. Kim Molvig – Fusion without neutrons using p-B11 (MIT Fusion Seminar)[pdf]

EMC2 Fusion Development Corp. – Inertial Electrodynamic Fusion: The answer to interplanetary space travel? - Tom Ligon's Presentation, 26th International Space Development Conference, May 2007 [ppt]

Small Vacuum Vessel Suppliers

Here is a handy list of vacuum vessel suppliers suitable for Fusor Construction. I will be adding to the list from time to time.

Meyer Tool and Manufacturing Oak Lawn, Illinois

Kimball Physics Wilton, New Hampshire

Kurt J. Lesker Company Clairton, PA

MDC Vacuum Products, LLC Hayward, California

Nor-Cal Products Yreka, CA

Trinos Vacuum Systems, Inc. Chicago, Illinois

A&N Corporation Williston, FL

Atlas Technologies Port Townsend WA

Sci Quip - Used Eqpt.

Oerlikon Leybold Flanges and Fittings

Link Added To Sidebar

I have added IEC Fusion Web Ring to the sidebar. It links to amateur fusion efforts.

Fusion Report 15 May 008

In Picture Of WB-7 Bussard Fusion Test Reactor Available I reported that there was a picture of the WB-7 Fusion Test Reactor available. (Well duh). I must sadly report that it is no longer available. Instead EMC2 Fusion has replaced it with a picture of a plasma test of the fusion reactor using Helium gas. Yeah! We are another small step on the way to fusion power. Or to proving you can't get there from here. Depending.

Reactor Size

I was rereading Sekora's paper on POPS [pdf] and came across this gem.

It is very difficult to achieve field strength approximately 50-100 kV/cm without causing arcing.The maximum field strength is governed by the Paschen curve.

So let us look at what a decelerator BFR might look like. Reaction volume 1 meter radius. That is a given. Let us assume 200 KV drive voltage. If we assume a voltage of 20KV/cm that gives 10 cm to zero voltage. Then assume 2 MV decelerator voltage. That is 1 meter. So the total radius is 2.1 meter. At 40" per meter (roughly) That is 84" radius or 168" diameter. About 14 ft in diameter for a 100 MWth reactor. Suppose we go to 40KV/cm (about the limit). That would be 1 meter reaction space. About 5 cm to zero voltage. And 50 cm for the decelerator. That would be 1.55 m radius. 3.1 m diameter. About 124" or a little over 10 ft in diameter. So odds are the reactor will be between 10 ft and 15 ft in diameter for a design with direct energy conversion. That would fit on all but the smallest ships.

Standardizing Fusion Test Reactors

In my recent post Starting A Fusion Program In Your Home Town I talked about expanding the fusion design and testing environment to increase the rate of progress in the development of a power producing reactor.

The lead Bussard Fusion Reactor (BFR) experimenter, rnebel, has read that article and has chimed in here with his thoughts.

One of the things we have been considering is selling a "turnkey" version of the WB-7. In this case we would design, build, license and deliver an operating Polywell, probably on the scale of the present machine. Operator training and tech support would also be part of the deal. The model is to use a plug and play concept where the user could substitute their own parts (electron sources, for instance) in an open architecture system. This is similar to what IBM did with the PC in the early 80s. It would give people who are interested in Polywells a chance to develop their own new patentable concepts and new companies without having to go through the entire learning curve that we have been on for the past several years. This struck us as a way to jumpstart the industry and get a lot of new ideas and people involved in Polywells. These devices could be funded through government grants (we have found a mechanism) or privately. I think we could do a turnkey machine for a ~ $500k-$1000k depending on how many people are interested. The idea would be for the government to make grants to institutions and then we would be able to competitively bid on providing the hardware. Ideally, I would like to see at least one Polywell in every Congressional district in the US. Since the cost is cheap, this is a tractable. Is this something you might be interested in?

My reply went as follows:

Sign me up.

I think it might also be useful to do a $10K to $100K fusor type device for those on a more limited budget. Jr. Colleges etc. There is a lot that can be learned from such a device that would help with more efficient (Pollywell) devices.

BTW in other places (fusor forum) I have made the evolution of the computer hobby argument.

Great minds etc.

Also a range of devices and power supplies. i.e. 25KV, 50KV and 100KV pulsed supplies. Then the same range of continuous operation supplies. Same for the reactors. Pulsed and continuous operation. The equipment should be standardized as much as possible - at least for the starter kits so we could get the efficiencies of mass production. Also standardized test equipment. Standardized control.

If we had 435 tests going on at once in each district that would cause the Congress critters to all get behind the fusion push. Very astute. That was sort of my idea.

Again - contact me and tell me how I can help. I'm rarin' to go.

Simon

Any venture capital people who would like to start something - contact me.

Reaction Rate and Drive Voltage Spread Sheet

You can down load it at Reaction Rate and Drive Voltage.

Starting A Fusion Program In Your Home Town

It is getting to the point that to make advances in the field of IEC Fusion collaborative efforts will be required due to the range of knowledge required and the cost. The individual with the home built fusor is not a thing of the past by any means, but it is not the wave of the future. I have been contacted by people from Jr. Colleges who are interested in doing fusion research so that is probably the place to go. Get your local Jr. College or College interested.

Here is one College doing work in the field that I have provided some advice and direction to: Peninsula College Fusion experiments. Here is another link with more details to the Peninsula College Fusor Project.

In that vein I have contacted Rock Valley College and Rockford College (in Rockford, Illinois) to see if I couldn't get something started. We shall see if anything comes of it.

Here are some links to get those interested started:

IEC Fusion Technology blog
Open Source Fusor Research Consortium II
The World's Simplest Fusion Reactor Revisited
Disciplines and areas touched upon in fusor construction

Standardized Fusion Test Reactors.

I'm going to add a list of Colleges and Universities that are working on small fusion (budgets under $100,000 - places like The University of Wisconsin at Madison which has a rather well funded IEC program - well above $100,000 - will not be on the list). If you get something going in your home town send me some info. I'll add you to the list.

UMass Lowell.
A Community College - no name given

Fusion Report 06 May 008

Richard Nebel tells about plans for commercializing the Bussard Fusion Reactor (BFR) at Talk Polywell. Richard starts off discussing who owns the BFR technology and patents. DOD is The Department of Defense. Currently the US Navy is funding the research.

...EMC2 owns the patents and the commercialization rights. DOD retains the right to use the technology free of charge. That's a pretty standard arrangement.

As for DOD taking control of the technology, I think that's pretty unlikely. The most similar parallel to this that I can think of was the development of fission power. Both nuclear fission propulsion and commercial power were developed in parallel. It isn't a coincidence that both systems are LWRs. I expect a similar situation here. Everyone that I have talked to at the DOD understands that energy supply is a major national security issue. It's not in the national interest of the US to keep this technology from going commercial. Furthermore, this project has never been classified. Fusion research world-wide was declassified in 1958 by international treaty.

Finally, I appreciate your concern about research being slowed down by the lack of dialogue. My previous research at LANL (POPS for instance) was always public domain. The reason we did it that way is because we figured that the patents would run out before we could commercialize it and the benefits of having it critiqued outweighed the drawbacks of getting "scooped". I still feel that way, but I have a little different responsibilities at EMC2. We have a responsibility to get this technology developed in a timely manner and I also have a responsibility to look after the interests of our employees and the corporation.

From the way he is talking he seems pretty confidant of success. I sure hope he is right. Dr. Nebel also reports that the EMC2 contract with the Navy runs through August. So that gives some idea of when we might know the answer.

To get an idea of what success would mean check out:

Easy Low Cost No Radiation Fusion also check out the IEC Fusion Technology blog.

The side bar at IEC Fusion Technology blog has links to various discussion groups. They can be found under the heading Working Groups.

A good tutorial and a history of the project before the US Navy resumed funding can be found at: World's Simplest Fusion Reactor Revisited.

Fusion Report 05 May 008

Richard Nebel reports at Talk Polywell that the EMC2 contract with the Navy runs through August.

Fusion Report 02 May 008

Here is a progress report from MSNBC's Cosmic Log about the status of the Bussard Fusion Experiment, WB-7.

Currently, the most promising path toward electrostatic fusion runs through Santa Fe, N.M., where a team at EMC2 Fusion Development Corp. is currently trying to validate Bussard's results. The team's leader, Richard Nebel, told me this week that it's still too early to gauge how promising the Bussard fusion device could be.

"We're getting high-power plasma," he said. "We don't have answers ... [but] we're far enough along that we know we're going to get answers."

If you want to learn more about Bussard's IEC Fusion here is a good place to go:

Easy Low Cost No Radiation Fusion

The side bar here has links to various discussion groups. They can be found under the heading Working Groups. You might be especially interested in the Talk Polywell discussion group where Richard Nebel can often be found commenting and answering questions.

The World's Simplest Fusion Reactor Revisited

Tom has graciously provided a pdf of his most recent Analog article The World’s Simplest Fusion Reactor Revisited for your edification and enjoyment. Please read the following and then click on the link provided for your own copy. Tom sends his regards to all. Enjoy!

Copyright 2007, 2008, by Tom Ligon. This article was first published in the January- February 2008 edition of Analog Science Fiction and Fact. Special edition with postscript for iecfusiontech.blogspot.com and fusor.net. This document may be downloaded, printed out, or linked from other sites, but please do not re-post it on other websites, or re-publish it, without the author’s permission. If corrections or updates are needed, I’d like a limited number of copies to track down.

The World’s Simplest Fusion Reactor Revisited

For All Mankind

A lot of people have been asking me publicly and privately, if the Bussard Fusion Technology is successful, can it be bottled up by special interests? I think the we have an answer from Dr. Richard Nebel who is now running the experiments in New Mexico.

Your concern is something that EMC2 has thought about. The Polywell is what is generally described as a "disruptive technology". Namely, it is a technological surprise that changes everything. A lot of people have/are investing a lot of money in energy technologies. The Polywell is their worst nightmare. Consider for a moment who isn't going to like the Polywell:

1. The fusion people. They've already gone ballistic (but we're not going to go there).
2. The fission people. They're working on a "nuclear renaissance".
3. The solar people.
4. The wind people.
5. Big oil.
6. The gas and coal companies
7. The biofuels people.
8. A few of the environmentalists.

As you can see, we are pretty much an equal opportunity irritant. We are very well aware that any number of people would like to sit on this technology and keep it out of the market. This is one of the primary reasons that Dr. Bussard chose to have this project funded by the Navy rather than privately funded (where we probably would have had a much easier schedule). With the Navy contract, we retain the rights to the intellectual property for commercialization.

Dr. Bussards's desires for this technology were very clear: he wanted it developed and used by the public ASAP. We intend to honor those wishes.

Dr. Nebel, if the latest experiment (WB-7) works out and you read this, I want you to know that if you can use my help I'm good to go. I'm willing to sweep the floors if that is the way you think you can best use me.

Cross Posted at Power and Control

Picture Of WB-7 Fusion Test Reactor Available

There is a picture up at EMC2 Fusion showing the WB-7 Test Reactor vessel. All polished stainless steel with a nice logo.

H/T Tom Ligon

Reactions

I do believe plasma physics has gone astray by the unfortunate use of the term instability to describe how a plasma reacts on itself. I think the term reaction would help to open up people's mindset. A plasma is not a stable thing. It reacts to everything including itself.

Plasma kinking is not an instability, plasma kinking is a reaction.

LC POPS

A resonant circuit at the natural POPS frequency might be a way to generate POPS energy without an RF supply.

It should go in series with the DC supply and be just before the grid input connection to the reactor.

This would make any RF generated naturally synchronized with the internal oscillations of the reactor. Phasing could be adjusted some by detuning the tuned ckt.

A good low impedance capacitor from the HV input to the LC circuit to the ground side of the supply would be a very good idea.

This is beginning to look a lot like Tesla Coil country. In fact this Tesla Coil CAD program might be of some use for coil winding and calculating resonant frequencies. Or formulas if you want to check the prepackaged calculators or roll your own. A list of Tesla CAD programs. A self resonance coil calculator.

You can check them against this equation as long as the coil desired is at least as long as its diameter.

Fmhz = (29.85 x (H/D)^1/5)/(N*D)

F= self resonant frequency in Mhz of an 'isolated' coil
H= coil height in meters
D= coil diameter in meters
N= total number of turns

===========

Update: 03 Feb 008 0714z



If the coils are made close to self resonance then a very small capacitor can be used to resonate the coil. That means the unit could be tuned over a small range by putting a sheet of dielectric between the capacitor plates.

The first thing to do is to get your fusor operating properly and then use a spectrum analyzer or 100KHz to 30 MHz radio receiver to find out what the natural frequency is.

A high frequency capacitive voltage divider with a diode detector hooked to the HV between the LC and the grid would be a good idea for tuning the coil. Tune for maximum RF.

The HV side could be from .5 to 2 pF (depending on frequency). With the low side capacitance on the order of 50 to 200pF (dependent on the high side capacitance). What you want is 100:1 divide ratio. Roughly. To start. If you use a 1N4148 diode as a detector. You should be able to go from about 100 VAC to 3000 VAC (diode limit is 3750 VAC - actually 1/2 of 75 PIV guaranteed*100). If the voltages you get are outside that range adjust your divider accordingly. The exact range is not too important as you are using it for tuning and not measurement. A voltage in the range of 5 to 10 V at peak output should give plenty of margin and yet give good tuning indication.

A lot is going to depend on lead dress. Keep everything as short as possible. The leads and everything that they contact is now part of your tuned circuit. As much as possible on the HV DC go for a single point ground.

What I'm thinking is that we have a Q multiplier here. If we use Q multiplication to raise the RF at the grid that should enhance the production of RF further raising the RF drive.

It will be interesting to see if it has any effect on fusion output. And what it does to losses.

Any way there is something like a 10% or 20 % chance we will do it this way. If it works you could control the feedback by adjusting the tuning.

Another way to tune it to start would be to use a fluorescent tube in the vicinity and tune for maximum brightness. That should be good enough to start.

Let me add one minor word of caution. We may not use this on the initial test devices until we are sure of the stability and frequency of POPS. For testing it would be more useful to have a power amplifier driven system with octave band output filters.

I have put a bit up at fusor.net about this and it seems there is an interested party. If he gets results I might change my attitude.

A while back some folks were fantasizing about how to use a Tesla coil to run a fusion machine. It looks like it might be the other way around.

Update:

Here is another design idea for how to do POPS that will be a little safer. The coil and tuning capacitor both have one end grounded. Again. A star ground for the HV will tend to reduce common mode voltages and currents.

Note that C includes coil self capacitance.


If the output of POPS is low a good rough indicator would be a NE-2 neon lamp [pdf]. Get the ones with leads. You can also raise the sensitivity by applying an AC voltage (mains power) to the lamp.

I built one of these 50 years ago when I was in the process of getting my my first Amateur license, K0NMR. They work pretty good.

Update: 04 Feb 008 0521z

Have a look at the wiki on Klystron Tubes. It uses the natural bunching of electrons to create microwave frequencies. Since we will be using ions which weigh 3600 times as much as an electron (D-D) the frequencies will be 60 times lower.

POPS oscillation is proportional to (Vwell/Mion)^0.5/Rwell according to the POPS paper by Park. For a 30 KV supply voltage POPS should be around 6 MHz in a small Reactor. In any case it has a very high probability of being in the .1 to 30 MHz range.

Note that like a klystron the POPS oscillator frequency changes with operating voltage. Suppose we got an impossibly high Q of 1,000 for the tuned circuit. that would mean we needed to hold the frequency within better than .1% (1 part in 1,000) to get the maximum effect of the tuned circuit. That means holding the voltage steady to better than .2%. Difficult. Not impossible. Of course with lower Qs wider excursions are possible. It means low ripple and low voltage servo variations. Servo variations of under .1 % imply open loop gains in the passband of over 1,000. Some fun.

Say we use 80 stacked 1,000 V @ 10 A supplies. The supplies would have to regulate to better than 1 V at full output and have less than 1 V ripple. At 30 KHz operating frequency that implies an output capacitance of 22 uF @ 1500 V rating. Able to carry 5A 30KHz AC without excessive dissipation.

Since this will effectively be an 80 phase supply due to the sequential firing of the stacked modules there will be some reduction of output ripple due to the stacking. That will come in handy at lower voltages where the allowable ripple becomes less.

The allowable bandwidth of the voltage control servo is in the 1 KHz to 3 KHz range due to the 30KHz operating frequency of the switching supplies.

It may also be possible to mechanically slew the tuned circuit frequency by .2% with a speaker capable of 10 KHz response connected to a small segment of the tuning capacitor. If that was the case, as long as the system was relatively stable in the 100 microsecond time frame the tuned circuit could be kept on frequency. A VSWR detector in the HV line could do that. What you would do is compare the phase of the RF current in the line with the phase of the RF voltage on the tuned circuit and use that to servo the speaker.

Here is how POPS might be done with Amplifiers. We might need to add in an automatic phase adjuster or a PLL to keep things properly tuned up. You can click on the dwg to make it larger.


Back of the envelope calculations say that for a 50 KV DC 50 Amp grid supply (2.5 MW) an RF Amplifier capable of 250 w to 1,000 w should do the trick if using an LC circuit is not practical.

I used the wrong envelope. If the p-p voltage required is 4% of the DC voltage that represents 2,000 V p-p. That would be roughly 1,500 VRMS. Assuming a the real component of the load is 1,000 ohms (same as the DC load) that gives about 25 KW. Doubling the p-p voltage would require about 100 KW.

At those kinds of powers it may be useful to run the RF generators from the HV DC supply.

WB-100 Superconductor Magnet Cooling

I have been working on some of the cooling issues for WB-100 - the 100 MW test reactor using superconducting magnets.

The magnet will consist of a series of concentric pipes. The innermost will contain the superconductor and its coolant at 20K. Next will come a vacuum space and next will come LN coolant. In the vacuum space between the superconductor coolant and the LN coolant the walls will be silvered (or some such) to minimize the radiative heat flow between the superconductor coolant and the LN. Think thermos bottle.

Next space after LN coolant will be another vacuum space. It too will be silvered. Then H2O coolant at around 300K. Another silvered vacuum space. And finally H2O coolant at around 600K.

What we are going to have is a series of concentric vacuum bottles with LHe at 20K at the center and H2O at 600K at the outside. All this plumbed to allow enough flow to keep everything at the proper temperature.

Let me add that any electrons ejected from the surface of this contraption will carry away minimal energy. The alphas will be hitting with 2MeV+. The electrons (those that are not lost due to high energy) will be at 50KeV.

My current plan is to coat the outer surface of the coils with Boron which melts at 2349 K. The purpose is to prevent sputtering of the metallic pipes holding the coolant so the only material sputtered into the reactant space will be a reactant - B11. It has been suggested at Coulter Smithing that an outer sheath for the coil of Titanium might work well since any sputtered atoms would act as a getter. OTOH it might poison the reaction. Lots of unknowns here. We may just have to build one and see what happens.

If we use Boron, we will have to figure out how to balance Boron condensation on the outer magnet structure with Boron sputtering from the reaction.

Below is a picture of a cross section of the superconducting coil.

Update: 06 Feb 008 2046z

I was thinking. Since for a power reactor we will need to water cool the coils. Suppose we made the water jacket thick enough to thermalize neutrons. And then had a B10 layer to absorb them.

It should be possible to cut way down on coil damage and still run superconductors in a D-D machine.

MgB is interesting in that it becomes a better superconductor with some neutron damage

With MgB the resistivity goes up. Critical Field goes up. And critical temperature declines slightly.

The main problem seems to be defects caused by B10 absorbing neutrons.

If B10 was used in shielding and B11 used to make the superconducting wire much longer lifetimes in neutron fluxes should be possible.

The the cross section difference is six orders of magnitude B10 to B11. With B10 @ 10,000 barns at .025 eV and B11 @ .01 barns.

Magnesium has a cross section of about .75 for 2.5 MeV neutrons

Mg is .063 Barns for Thermal Neutrons.

Which says that if we can get an operational life of the superconductors at 10 hours with ordinary Boron, a year should be possible with five to six nines pure B11.

Reduce the Flux another factor of 10 with water moderation and a B10 absorption layer and you are up to 10 years operation. Double that Boron 10 thickness and you are up to 100 years. Which should allow for various inaccuracies and production variations.

10 B has a Maxwellian thermal neutron flux cross section of almost 4,000 barns.

11 B is around .1 barn.

At room temperature Borax B(OH)3 is soluble at about 57 g/ liter. Which is about 9.3 g/ liter of B10.

Maximum properties of MgB occur at 2E18/cm^2 total neutron flux. Let us say 1E18 and have some safety margin.

Typical fission reactor neutron flux is 1E12/second. Let us say because of the lower energy per reaction a D-D reactor would have 50X that flux.

So that is 20,000 seconds at full power with natural boron. Say 4 1/2 hours. If we go to B11 superconductors assume a 1,000 time improvement. That is 4,500 hours. Say 6 months roughly. So we need a B10 shield that can reduce the neutron flux at the coils by a factor of 10. Giving a life of 5 to 7 years continuous operation.

Since MgB is cheap, replacing the coils every 5 to 10 years should not be a big burden. In addition preconditioned coils capable of sustaining 30 T might get a premium.

Update: 07 Feb 008 0414z

revised thicknesses
I think it is worthwhile to look at the B10 thickness required to absorb 1/10th of the incident thermal neutrons. I calculated it and came up with .005 cm. That is right 5 thousandths of a cm. To slow the neutrons from an average of 2 MeV to .025 eV (thermal energy) requires a thickness of water of about 2 1/4 inches (5.7 cm). About what I would expect to need on the basis of heat transfer and pumping considerations alone. It might be possible to include that B10 thickness (or even 3X that) in the construction of the 300K coolant channel. Just deposit it on the interior since there is no heat transfer consideration (except pumping losses from wall roughness) involved.

At a flux of 1E12 neutrons a second per sq cm., 1 sq cm will have a total flux of 3.16E20 in 10 years. To handle that number of disintegrations would require a thickness of .003 cm. Not too tough. Since the actual density required could be cut in half without seriously affecting the required volume of absorber, it might work out to fill an extra layer with boron powder. That way any break up of "structure" from radiation damage would have little effect on the absorbing properties compared to initial conditions. A layer .1 cm thick could be adequate if you recompressed it from time to time. Certainly a cm or two would be overkill.

I forgot that a D-D reactor with the same thermal power out as a fission nuke will produce about 50X as many neutrons. The 1E12 factor is based on a fission nuke. Still not a show stopper.

Update:

I have a show stopper. Each neutron absorbed produces 2.8 MeV. In a D-D reactor there is no way to carry the heat away without adding more water layers. At best a very thin layer might buy us some operational time for a test reactor. The advantage may go to using a B11 superconductor even with its lower Tc. That still only gets us months of operation. Probably good enough for experimental work.

BTW the neutron flux in a D-D reactor with a coil radius of 2 m at the coil radius is on the order of 3E14 neutrons a second at 100 MW fusion output.

Further Update:

With an intermediate layer filled with borated water to absorb 99% of the neutron energy, or 99.9%, you might get the flux down to where powdered boron could handle the rest. Great idea. At 9.3 g/l that is 9.3E-4 g/cc. Compared to 2 g/cc that would require about 10 cm - vs .005 cm for a factor of 10 reduction. Not going to work. So it still looks like MgB11 superconductors with B11 at 4 nines or better. That still only buys you a total of 1,000 hours - probably enough for initial experimental work at 100 MW.

If you could maintain a slurry of boron particles and still keep the whole contraption cool - it might work.

The trouble is that it almost doubles the neutron thermal load (1.75X). The neutrons lose 3.65 MeV thermalizing and then the B10 adds a 2.8MeV alpha. Which increases the total heat load by about 40% in what was already a marginal situation.

WB-6 Shopping List

Peter in the comments at Making the Well posted this nice parts list and operating procedure for WB-6. With his permission I'm reposting it here. A lot of the material has already been covered, but this is a nice recap.

==

I've been working on a shopping list of the specifications and requirements of WB-6.

Most of the data comes from:
Dr. Bussard's Final Lab Notes
Valencia Paper
Google Video
Other bits are referenced.

If there are any mistakes or additions updates will be most welcome.

Polywell reactor specifications for a WB-6 equivalent reactor:

Vacuum chamber

• 2m diameter tank with a Faraday cage inside (WB-6 was 2m by 3.5 m) that can go down to 1*10^-9 Torr

Vacuum pump

• Able to pump (2m diameter chamber) down to less than 1*10^-9 Torr

Electron emitters

• Banks of headlight filaments


• Grounded


• Activated by fiber optically isolated Siemens switch


• Heating current of about 40 amps


• (Stainless steel?) poles to place them at a standoff distance approximately equal to the mean radius of the cusp face through which they are injected.
  (to minimize electrostatic droop in the potential well at these corners)


• poles attached to the corners of the 'square' Faraday cage.

Microwave generator

• "microwaves at the ECR frequency corresponding to the magnetic field makes a death zone for neutral gas". (What is the ECR freq in WB-6?) Tom Ligon at the Fusor Forum

Magnetic field

• Preferably superconducting magnets (greatly reduces power requirements and magnet strength possible in a smaller space.)


• Otherwise 200 turns of approx 1000m of 0.15mm diameter copper magnet windings.


• Cross-sectional diameter of toroid about 3cm, inner diameter about 20cm and outer diameter about 30cm


• Linked in series with up to 2000A of current running through them for just over 20ms.


• Make sure no tight bends in the windings.

Magnetic Grid Shell

• Stainless steel tubing welded and then polished. (Laser or electron beam welding should do the trick, so as not to damage the windings inside) M Simon in the comments


• Tightly conformal to the magnetic coils inside.


• Joined by small (approx 1cm long) tubing just outside the midplane of the magnetic field of the coils.


• Structural strength required to survive vacuum and force produced by six 0.2T magnets trying to separate from each other.


• No metal surface may penetrate the magnetic fields by more than 1*10^-4 of the total surface available to the recirculating electrons.

Structural support of Magnetic Grid

• Four support stands on the base toroid (or three or four on each with no (or slimmer) pipes joining the toroids.)


• (Stainless steel again?) encased and thus ˜hidden" from electrons by tapered ceramic supports.


• Has current carrying conductors inside helping to protect it from electrons by magnetic shielding.


• Make sure no tight bends in power supplies through the legs or the joins.

Gas supply

• Supplied by a (or several) tubes of a known tiny finite
  o volume (less than 5cm^3)
  o and pressure (300mili Torr too high. Must be small enough that the resulting gas pressure in the chamber is less than 3*10^-6 Torr).(This allows for the volume of gas in the reactor to be increased by tiny discrete intervals to ensure complete ionization and no flooding of the outer chamber with neutral gas.)


• Last section of tubing is glass to minimize electron losses.


• Gas input from tubes controlled by a fast acting (<1ms) solenoid valve


• Glass tube releases gas just inside the inner perimeter of the magnets. To one of the coil/coil spaced seam areas. The magnetic fields here are very strong and that reduces the likelihood of electron losses by electrons impacting the tube.

Sensors

• Sensitive Photomultiplier system
• Pressure sensors (sensitive down to 1*10^-9 Torr)


• Optical spectrometer


• Sensors for all currents and voltages on all supplies and lines and grounding cables.


• 3 neutron detectors at varying distances (of a type not affected by high voltage and able to give quick electronic output.)


• Cameras (They had two black and white ccd and 1 color camcorder) High speed color cameras operating at frame rates of much less than 0.1miliseconds would be best.

"The earliest Polywell, HEPS, was also verified to make a potential well, I believe by using four 94 GHz microwave beams across the chamber to map electron density.

The more recent machines have used at least Langmuir Probe methods (stick a wire in the thing and see what happens). And generating DD fusion is fairly convincing evidence, as well." Tom Ligon at Fusor.Net board.


Power supplies

• Car batteries for the electron emitters


• 240 RV batteries connected via an IGBT switch(able to safely produce at least 2000A)


• Twelve 225uF capacitors producing up to 15kV, 400kJ at 5A current (or 30kV at 2.5A) these can be discharged through the magnet windings.


• Fast acting pneumatic-driven copper block switch to connect capacitors.


• At least 1200W supply for microwave generator

Check Dr. Bussard's Final Lab Notes for operating procedure.

It Doesn't Get Any Better Than This

Dr. Nebel, who is working on the Bussard Fusion Project has taken some time out of his busy schedule to thank the bloggers supporting the WB-7 Project.

Also, I would like to thank M Simon, TallDave and their fellow bloggers for their continued interest in this technology. We appreciate that a great deal, but as you might imagine we have been a little too busy to communicate very much with the on-line people.

This is the head of the current research project. Everyone who has supported this in any way, including just reading the articles, can take a bow.

Special thanks go to my friend Eric and his pal Justin at Classical Values for getting me started on this. Also I am very grateful to Tom Ligon for being patient with me while he helped me learn the ropes. We have been manning the anchor capstan. Soon the anchor will be secured, the sails hoisted, and the ship under way. May the Maker Bless us all.

If any one wants to help man the rigging may I suggest reading this short post and using the urls provided in it to contact your Congress Critter. We need a gale to get us where we want to go in the shortest time possible. As they like to say in another Navy that is yet to be. Warp speed Mr. Sulu.

Tom Wrote A Short Story

It covers the very basics of The Bussard Reactor and the trials and tribulations of developing new technology in a very engaging way. You can read it here:

Getting Tuned Up

WB-7 First Plasma

MSNBC Reports first plasma on WB-7 Reactor.

Bussard's mantle has been picked up by a small team led by Richard Nebel, who has taken a leave from Los Alamos National Laboratory to head up Bussard's EMC2 Fusion Development Corp. Backed by a Navy contract, Nebel's five-person team is trying to pick up the technology where Bussard left it.

"What's there is interesting, OK?" Nebel told me today. "And the bottom line of it is, what we've been charged to do is reproduce that. Find out if it's real. Find out if or if not all this stuff is what it seems to be."

EMC2 Fusion has built an upgraded model of Bussard's last experimental plasma containment device, which was known as WB-6. (The WB stands for Wiffle Ball, a whimsical reference to the structure of the device.) "We got first plasma yesterday," Nebel said - but he and his colleagues in Santa Fe, N.M., still have a long way to get the WB-7 experiment up to the power levels Bussard was working with.

"We're not out trying to make a big splash on any of this stuff at this point," Nebel said. But he said he's hoping to find out by this spring whether or not Bussard's concept is worth pursuing with a larger demonstration project.

The initial analysis showed that Bussard's data on energy yields were consistent with expectations, Nebel said.

"We don't know for sure whether all that's right," he said, "but it'd be horrible for Mother Nature to give you what you expect to see, and have it all be bogus."

If you want to learn more about this technology may I suggest:

Bussard Fusion Reactor
Easy Low Cost No Radiation Fusion

If you want to get deeper into the technology visit:

IEC Fusion Technology blog

Start with the sidebar which has links to tutorials and other stuff.

The First Wall Problem

I have been discussing with Dr. Mike the problem of alpha sputtering. What Dr. Mike calls the First Wall problem.

Alpha impacts on the grid(s) is going to be a problem. If alpha impacts knock metallic elements from the grid(s) they could poison the reactions or at the very least waste electrons and energy.

One solution is to coat the grids with a sufficiently thick layer of Boron and run the machine such that the Boron in the reactor replenishes the Boron on the grid(s).

Thus - any elements knocked off the grids are a reaction species and thus do no harm to the reaction.

Dr. Mike replied that Boron is not very structurally strong. A fact I was unaware of. Dr. Mike suggested that embedding the Boron in some kind of plastic might do the trick. I had some objections to that.

So I went to the 'net and did some research.

I believe ITER uses a Boron coating evaporated on the surfaces to solve the sputtering problem.

If you use pure Boron you have one segment of the problem solved (reaction species) the other problem is to maintain a balance between the coating and the reactants.

Once you get into hydrocarbons you have problems with non-reactant species.

The question then is do thin films have significantly different properties from bulk Boron.

This might be a place to start:

really long url

Search Boron on this page:

Diagnostic Needs

also a look here:

Energy Citations

and here:

Abstract of an interesting Paper

I'm pretty confident that the thermal problems can be solved. So this is the next hump IMO. BTW I'll go into my ideas on how the thermal problems can be solved in another post.

Let me note that Dr. Mike thought this was a good approach. At least to start.

Bussard Fusion Update

The New Mexican has some interesting news about the progress on Bussard Fusion Reactor.

Last August, as Bussard was losing his battle with cancer, the funds were restored with the support of Alan Roberts, EMC2's longtime Navy contract monitor. The company now has $1.8 million to pursue his work. If it is successful verifying the 2005 results, it would seek funding for a full-scale model, big enough to make net power, Nebel said. Bussard has estimated that such a demonstration model would cost about $200 million to build.

"Unless somebody can repeat and show other people that it's operating, it's really not scientifically acceptable," Hirsch said. But "if the idea works the way he thinks it could, and there's a good chance he's right, it will not take very big machine to show net energy."

The latest device, WB-7 (the WB refers to the children's toy Wiffle Ball), is currently under construction at a machine shop in San Diego and will be shipped to Santa Fe, where a small group of scientists is setting up a testing facility in an office park off Rufina Street. The device, like previous ones, was designed by engineer Mike Skillercorn.

"These are garage-scale experiments," said Nebel, pointing to the stock tank purchased at a local feed store. "We shop at interesting places," he added, mentioning both Home Depot and the Black Hole in Los Alamos.

Although Europeans are building a huge device to demonstrate the scientific and technical feasibility of fusion power, the U.S. has spent relatively little — about $300 million a year — on fusion research. Much of that has been focused on a competing idea called Tokamak, a program that Bussard and Hirsch started at the Atomic Energy Commission in the 1970s, which uses deuterium and tritium as fuel. Later both determined that the concept, which produces a lot of radioactivity, was impractical from an engineering standpoint.

With his own device, Hirsch said, Bussard was "swimming upstream as far as fusion community was concerned." Still, he was able to get about $14 million in funding from the Navy for his work.

Bussard felt enormous pressure to solve the fusion problems. In a letter to an Internet forum on his 2005 results, Bussard wrote that he believed that "the survival of our high-tech civilizations depends on getting off of fossil fuels ASAP, and — if we do not — we will descend into a growing series of 'oil wars' and energy confrontations that can lead only to a huge cataclysm. Which CAN be circumvented if only we build the clean fusion machines in our time."

That is one of the reasons I support this research. Civilization depends on it.

Nearly a year after shutting down the lab, Bussard presented his work — for the first time in more than a decade — to the International Astronautical Congress. He later discussed his results with Google, the online search engine company in a talk titled, "Should Google Go Nuclear?" that is widely available on the Internet. Before his death, he also set up a nonprofit organization to solicit donations to restart the work. Information is at www.EMC2Fusion.org.

Bussard's wife, Dolly Gray, who co-founded EMC2 with him in 1985 and served as its president and CEO, has helped assemble the small team of scientists in Santa Fe. Besides Nebel, 54, the group includes Jaeyoung Park, a 37-year-old physicist who is also on leave from LANL; Mike Wray, the physicist who ran the key 2005 tests, and Wray's brother, Kevin, who is the computer guru for the operation.

"If this works, it's going to be a big deal. It could take the entire energy market," Nebel said. "And drag the oil companies into the 21st century," Gray added.

Someday, they said, if they're right, a machine just 20 times bigger than the one sitting in the corner on Parkway Drive could run the city of Santa Fe.

Park and Nebel [pdf] are the researchers who discovered the POPS effect which was corroborated in part by computer simulations done at MIT by McGuire[pdf] and Dietrich[pdf].

I estimate we will see the results of these experiments some time between March and May of the coming year. I have my fingers crossed.

The New Mexican article has a great review of Dr. Bussard's life. You should go and read the whole thing.

Here is a tribute I wrote to Dr. Bussard. It has lots of links to the science of the Bussard reactor.

ITER Budget Cut

Science Magazine reports that the Federal Science budget has cut ITER funds to zero.

The bill set the budget at DOE's Office of Science at $4.055 billion--$342 million short of the requested amount--and the shortfall comes mainly out of two programs: fusion sciences and high-energy physics. Congress realized some savings by allotting nothing for U.S. participation in the international fusion reactor experiment, ITER, which is set to begin construction next year in Cadarache, France (ScienceNOW, 21 November 2006). Although appropriators expressly forbid DOE to shuffle money from other programs to satisfy its planned $149 million contribution in 2008, Marburger predicts that the prohibition will not stand. "I can't see DOE not living up to its obligations," he says. "The department will have to use its money to stay in the project, so [the language] really just amounts to another earmark."

I have heard rumors that Congress is interested in the Bussard Fusion Reactor. If it works out (Bussard Fusion Reactor Funded) ITER (a tokamak design) would be a waste. Or as Plasma Physicist Dr. Nicholas Krall said, "We spent $15 billion dollars studying tokamaks and what we learned about them is that they are no damn good."

We will know the answer in 3 to 6 months. At that point in time if Bussard IEC Fusion Reactors look like a dead end the budget for ITER can always be restored. Or the money could be put into other IEC devices. The advantage of IEC is that the budgets required for confirming experiments are small and the time frame for proof or disproof is short. Years, not decades or centuries.

Transimpedance Amplifiers

A while back I made an off hand comment (can't remember where) about using a transimpedance amplifier to bring broader bandwidth diagnostics to the plasma community in general and IEC Fusion in particular.

Let me start with the MIT paper [pdf] by Carl C. Dietrich. Let us look at his Ion Detector on page 49 of the pdf. He has a nice picture of the probe on that page. On the following page he gets to the heart of the matter, a schematic representation of the detector circuitry. For frequency response estimation purposes the detector can be modeled as a 100K resistor in parallel with a 100 pF capacitor (which accounts for a probe capacitance of 5pF). The 3 dB roll off point is = .15/(R*C) - within 5%. which would be .15/(1E5*1E-10) = .15E5 = 15KHz. Pitiful. I think the scope impedance and frequency response is so limited because he has to use the very highest gain (where scope bandwidth is less) to see any signal at all. So we can estimate the signal at 1 mV p-p. Into 100 K ohms that means a current of 1E-8 Amps. About 10 nano Amps.

Can we do better? Yes. But we have to do a couple of things. One is to reduce the input impedance to get wider bandwidth and second we are going to have to amplify that current. Thanks to the proliferation of fiberoptic technology we have exactly the tool we need to do the job.

I like the Philips SA5211. It is low noise and high gain with a maximum output swing of a few volts with a 5 volt supply. It is also bipolar technology tending to make the input a bit more robust than JFET or MOSFET input technology.

So let us start with gain. The transimpedance gain (minimum) is about 20K ohms differential. What does that mean? A current of 1E-8 Amps will be multiplied by that resistance to give 2E-4 volts change between the two outputs. About 200 uV p-p or about 70 uV rms. That is a fair signal for spectrum analyzer and other RF work. Feed that into a transformer like the Mini-Circuits T1-6T and you have a package with good gain from 30 KHz out to 150 MHz and almost flat from 300KHz to 50 MHz. To look at lower frequency signals I'd use an ordinary instrumentation op amp from the differential output of the transimpedance amplifier. The AD8253[pdf] looks nice with a bandwidth of 3 MHz at a gain of 100 (40 dB). That gets us to 20 mV p-p at the output for signals in the audio to low RF range. Not bad. For the higher frequency signals I'd follow the transimpedance amplifier with a couple of 20 dB gain stages (at least) to get the signals up to the mid mV range. I like the Mini-Circuits MAR-8A which is rated out to 1,000 MHz (25 dB gain typ) and is not too hot in the high frequency gain department so that taming the circuit will not be too difficult. It also has gain from DC to 1,000 MHz - meaning we can use it to amplify RF in the mid kHz range without problems. Some amplifiers of the type do not like low frequencies because the slow waves can cause the circuits to either over heat or become unstable.

So now we are facing the last question. Bandwidth. The feedback resistance for the transimpedance amp is about 14K (I used 10 K - above multiplied by 2X to account for the differential output) with the gain of the input stage a factor of 70. So what is the input impedance seen by our current (ion) source? That would be 14K divided by the gain of the input stage (70) or 200 ohms. It has an input capacitance of 4 pF. Let us say the probe is another 6 pF or 10 pF total. Double that to account for a lot of slop in the installation.

Let us plug that into our frequency formula: .15/(200*2E-11) = 37 MHz. Not too shabby. We can double that without too much effort if we work to keep stray capacitance down. Which means that our SA5211 at 200 MHz bandwidth should be more than adequate for the job with the subsequent Mini-Circuits amplifiers making a very small contribution to reduced high frequency gain.

So there you have it - a very nice high frequency ion probe. With a minimum AC signal of 1E-8 Amps p-p and a maximum signal of 4E-5 Amps p-p (at the transimpedance amplifier - gains of the other amplifiers would need adjusting if the signal is near maximum).

Update: The 1E-8 Amp current limit is where the signal = the noise for a 50 MHz bandwidth. If a narrow band detector is used (1 KHz) the detection limit goes down to 1E-10 Amps p-p.

ITER Control

Emerging Technologies takes a look at ITER control and safety systems. They plan to sample at 5 MHZ for data acquisition.

Here is a nice pdf to get you started.

Vacuum Pumping

I'd like to go a little deeper into the subject of vacuum pumping and easily attainable ultimate pressures.

Since this is a paper exercise we can pick any pumps we want. I'm going to look at 3 pump mfgrs. and pick their highest capacity turbo molecular pumps.

Adixen - Mag Lev [pdf]
Pfeiffer - Mag Lev
Varian [pdf]

There are two critical specifications for us. H2 pumping speed in liters/second and H2 compression ratio.

Turbo Molecular Pump Comparison

	H2 Speed l/s	H2 Compression Ratio
Adixen ATH-2300M	1200	3.0X103
Pfeiffer HiMag 3400	2850	4X104
VarianTurbo V 3K-T	2300	1.5X104

It looks like the Pfeiffer HiMag 3400 all the way.

Next lets look at a Roots fore pumps. I really like the Adixen RSV [pdf] series. The link has a great look at pumping capacities vs vacuum pressure and shows the limitations of roots blowers. Let us look at the RSV-1002. The largest standard pump. It has a pumping speed of 800 M³/hr with the model 2100 SD [pdf] roughing pump. That is about 225 l/s at a pressure of 3E-1 mbar (which for out Rough Order of Magnitude (ROM) purposes can be considered equal to 3E-1 torr). At 1E-2 mbar (where you can turn on your turbo pumps) it is about 100 l/sec. At 1E-3 mbar it is about 40 l/s. Ultimate pressure is 2E-4 mbar.

The Roots fore pumps basically stops pumping at 2E-4 torr. Given a turbo pump compression ratio in the neighborhood of 1E4 that gets us down to 2E-8 torr. Not enough. In addition the closer you get to the Roots ultimate pressure the lower your capacity. To get us lower we are going to need another turbo pump in series with the chamber pumps. Tom Ligon in an e-mail suggested using one pump to service all the chamber pumps. Brilliant idea. This should work fine as the volume of gas to be moved will be 1/10,000th of the amount (in liters) of the gas being pumped out of the chamber. Even with 10 or 20 chamber pumps you would still have a lot of excess capacity if you used a turbo pump with 1/100th the capacity of the total of all your chamber pumps. A pump of 600 l/s should be more than adequate. We leave the choice of that pump as an exercise for the reader.

So let us look at the chain of pumps. Say 6 or 10 reactor chamber turbo molecular pumps. A smaller turbo pump drawing from those pumps. A Roots blower next followed by a roughing pump. This all has to be properly sequenced to avoid damage to the pumps and systems. Then you have to sequence the various pressure reading devices depending on pressure. There should be enough work to keep the vacuum guy busy for at least a couple of weeks. Especially if s/he is budget constrained.

Update 21 Nov 007 0642z

I messed up pump volume calculations so let us go over them.

20 turbopumps X 3,000 l/s = 60,000 l/s. 1/100th of that is 600 l/sec.

Corrected in the text.

Data Collection

Dr. Bussard in his lab notes says that the ionization and other quick gas processes happen in 1 to 2 microseconds. Nyquist says that to be sure of capturing the highest frequency of interest you have to sample at 2X that frequency. Even so, if you sample at the zero crossings you will miss it. So much for Nyquist.

What we want is not just to measure process completions, but also look at what is happening in those processes. We might gain some insights. To do that you have to sample at least 3X the frequency of interest and much better 20X.

That says we need to sample at 20 MSPS. Front your sampler with a nice high speed fiber optic transimpedance amplifier in parallel with a DC (relatively) amplifier for low frequency fidelity and you have a very nice front end for a lot of the instrumentation we will need.

Stuff that will be sampled less frequently can of course use a much less expensive design.

With memory as cheap as it is these days I think that you decide what your maximum data collection time is at high speed and keep that amount of memory local. Then you have some kind of stupid simple protocol (say RS-485 as the physical layer) to collect the data. 5 MBPS shouldn't be too tough. With a 60% efficient protocol you should be able to collect the data from 1 high speed channel in 100 seconds. About 2 minutes. Twenty such channels in under 35 minutes. If you used 100 Base T Ethernet in a command-response type network you should get transmission time to come it at around 3 1/2 minutes. The slower RS-485 might be better if you have to collect data in an operational situation. Command-response Ethernet in relatively quieter environments (do a shot - recharge everything - hit it again).

Of course to see what the actual timings are like you have to pass around a synchronizing signal. Getting everything to start within 10% of the actual start time means passing out nice pulses on cables that differ in length from each other by no more than 20 inches. Not too tough.