Recovery.Gov Project Tracker

Point out news stories, on the net or in mainstream media, related to polywell fusion.

Moderators: tonybarry, MSimon

D Tibbets
Posts: 2775
Joined: Thu Jun 26, 2008 6:52 am

Postby D Tibbets » Tue Feb 07, 2012 2:25 am

A PS: to my next to last post.

Concerning size and B field targets. I mentioned several considerations. Another important consideration is the gyroradius of the fusion produced ions. Nebel mentioned several years ago that in order to turn these hot ions (alphas) a B field of ~ 3.5 T in a ~ 3 meter (?) machine might be needed. Smaller B fields would result in the alphas impacting the magrid before they could complete one gryo turn. So the location of the Wiffleball border and the strength of the B field and the overall radius of the magrid must fall within an interacting range.

For example a 10 M magrid radius with the Wiffleball border 1 meter inside the magrid, and a modest B field of ~ 1 T may not allow for cusp magnetic containment of the alphas. Many would hit the magrid. This results in perhaps unwanted heating of the magrid and precludes any efficient direct conversion scheme. This may also be significant for D-D reactors. The tritium, He3, and protons resulting from the reaction carry ~ 50% of the kinetic energy . If they are not kept away from the magrid surface, the heat loads on theses exposed parts would be perhaps twice what it would be if the magnetic shielding was adequate. The vessel walls are less vulnerable to this heating because they are further away and thus have greater surface area to handle the thermal loads.

Dan Tibbets
To error is human... and I'm very human.

ladajo
Posts: 6204
Joined: Thu Sep 17, 2009 11:18 pm
Location: North East Coast

Postby ladajo » Tue Feb 07, 2012 5:00 pm

For example a 10 M magrid radius with the Wiffleball border 1 meter inside the magrid, and a modest B field of ~ 1 T


Dan, these numbers make no sense to me. Also, the plasma pressure plays as you well know. B=1 could be a wide range of diameters, but those diameters should be of a limited range to produce useful fusion levels.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

Roger
Posts: 788
Joined: Fri Jul 06, 2007 2:03 am
Location: Metro NY

Postby Roger » Tue Feb 07, 2012 8:07 pm

As a follow up, From WB-7 to WB-8 What are the changes we know about?
- Nubs replaced by standoffs.
- Larger size magnets
- More power to magnets.
- Beveled magnets?

The graphic on the website shows a magnet with a bevel. Does this change cusp geometry, I'll guess yes. Does it improve containment by itself?

Could these 4 changes all take part in improved containment? I'll guess yes.
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.

KitemanSA
Posts: 6114
Joined: Sun Sep 28, 2008 3:05 pm
Location: OlyPen WA

Postby KitemanSA » Tue Feb 07, 2012 8:41 pm

My comments in red.
Roger wrote:As a follow up, From WB-7 to WB-8 What are the changes we know about?
- Nubs replaced by standoffs . . . This is NOT known.
- Larger size magnets . . . . . . . . This is derived from a graphic of the chamber
- More power to magnets. . . . . . This is a contractual requirement
- Beveled magnets? . . . . . . . . . .There is no reason to think this.

The graphic on the website shows a magnet with a bevel. What web site are YOU looking at? There is no such feature in any graphic I see! Does this change cusp geometry, I'll guess yes. Does it improve containment by itself? Good question. Ask Rogers. That is HIS feature I think.

Could these 4 changes all take part in improved containment? I'll guess yes.

D Tibbets
Posts: 2775
Joined: Thu Jun 26, 2008 6:52 am

Postby D Tibbets » Tue Feb 07, 2012 9:55 pm

The beveled magnets are on an engineering drawing of WB8 that was once on the EMC2 website. The wall standoffs were also shown. In fact each magnet was separately mounted on its own pedestal that was inserted into the vacuum chamber. This makes sense as it allows each magnet to be handled separately. If one fails or does not meet spec, it can be replaced without effecting the other 5 magnets.

As for a bevel vs a round shape for the magrid cross section, I suspect that this was an artifact of the drawer. I'm sure the round (or at least oval) form was retained for the two reasons stated by Bussard. - to prevent field lines from penetrating the metal case and thus compromising confinement. Even if these bevels are outside the cusps proper, they would increase ExB drift losses.
The other concern is arcing. Any surface with a sharp corner greatly increases arcing vunerability. The radius of curvature of any surface should be maximized within the limits of other design considerations. Any Tesla Coil enthusiast is aware of this consideration.

PS: Let me clarify, the picture of the WB8 chamber shown on the EMC 2 website is compatible with the above, but is not conclusive.

http://www.emc2fusion.org/

The drawing showing the beveled magrids and the pedestal arrangement comes, I believe from one of Joel Rogers drawings.

Second slide from presentation:

http://www.physics.usyd.edu.au/~khachan ... Rogers.pdf

Dan Tibbets
Last edited by D Tibbets on Tue Feb 07, 2012 11:04 pm, edited 1 time in total.
To error is human... and I'm very human.

ladajo
Posts: 6204
Joined: Thu Sep 17, 2009 11:18 pm
Location: North East Coast

Postby ladajo » Tue Feb 07, 2012 10:40 pm

What we know in public is only one thing: That they have upped the B-field by a factor of 10, designing, per the contract for .8

The other thing we can surmise in public is that the coils are larger. This, as Kite has stated, is based purely on some thumbnail engineering and standard parts lookup by forum members. As I recall, it was Tom Ligon who noted the bolt patterns, and equated that to parts lookup.

The rest we have in the public realm is supposition, mixed with a few tidbits here and there from EMC2 comments.

I remain hopeful and positive, whereas for Rossi, I do not.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

D Tibbets
Posts: 2775
Joined: Thu Jun 26, 2008 6:52 am

Postby D Tibbets » Tue Feb 07, 2012 11:01 pm

ladajo wrote:
For example a 10 M magrid radius with the Wiffleball border 1 meter inside the magrid, and a modest B field of ~ 1 T


Dan, these numbers make no sense to me. Also, the plasma pressure plays as you well know. B=1 could be a wide range of diameters, but those diameters should be of a limited range to produce useful fusion levels.


The numbers were made up in order to illustrate the point. The Wiffleball border as a percentage of the machine size may vary with the plasma pressure, though I think that at Beta= one the optimal radius of the Wiffleball will be relatively close to the magnets. Looking at the geometry of the cusps this would occur at the mid plane of the magnets. This is an area where the cusp is extending outward, and is not the average radius of the Wiffleball, but since the Wiffleball is nearly spherical except for these narrow spikes the optimal average radius would not be far inside the magrid radius.

The actual Beta= one condition is dependent on the density * KE / B .

A small KE with the same density and B field would result in a smaller radius Wiffleball. But, it is important to remember that the Wiffleball inflation is a range of effects, not one arbitrary size or Beta value. A Beta of zero would be a zero Wiffleball trapping factor- pure cusp confinement as described in the patent application. A Beta of 0.5 is better and does result in inflation of the plasma volume so it qualifies as being described as Wiffleball , but the trapping factor is nowhere near optimal. To optimize the Wiffleball effect, Beta= one has to be closely approached. This means that the radius of the Wiffleball approaches the radius of the magrid to the maximum amount allowed without blowing out the cusps. You can increase the B field strength and this would decrease the Wiffleball radius but it would also decrease the Bets ( the B variable is in the denominator).

Using a paint program, you can apply a warp tool to a picture of the mag fields in a pre Wiffleball Polywell. As the central area is warped outward in a circular geometry, it becomes obvious that the circle approaches the magrid, and the surface area of the cusp openings becomes less absolutely and compared to the total surface area of the circle. This is the whole point of the Polywell. The cusp confinement is similar to a biconic cusp mirror machine except of course the effective conversion of most of the line cusp loss area into point cusp comparable equivalents. A small volume of plasma is confined, with a determined cusp surface area loss ratio. The Polywell increases the confined volume without a corresponding increase in cusp loss area. In fact due to the shape of the cusps, the cusp loss surface area decreases by a factor of ~ 5(?). With the corresponding increased Wiffleball surface area as it inflates by a factor of perhaps 5-10, a net benefit of perhaps 20-50X. That combined with the benefit of what was called cusp confinement over mirror confinement (~ 60cusp confinement/5-8 mirror confinement) gives the final Wiffleball trapping factor of several thousand over no confinement. The cusp confinement represents low Beta operation, while the ~ several thousand represents high beta. and that represents the maximum inflation of the Wiffleball. My arbitrary ball park figure for this size is ~ 80-90% of the magrid radius.

Certainly by manipulating the three parameters you may achieve a smaller Wiffleball radius at Beta= one conditions, but why? The goal is to maximize containment efficiency and volume, and that goal is reached by pushing the Wiffleball radius to the maximum possible. This both increases the surface area and volume of the Wiffleball while minimizing the cusp loss surface area both directly and as a percentage of the total Wiffleball surface area.

Dan Tibbets
To error is human... and I'm very human.

ladajo
Posts: 6204
Joined: Thu Sep 17, 2009 11:18 pm
Location: North East Coast

Postby ladajo » Wed Feb 08, 2012 9:34 pm

Certainly by manipulating the three parameters you may achieve a smaller Wiffleball radius at Beta= one conditions, but why?


That was exactly my point entering.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

ladajo
Posts: 6204
Joined: Thu Sep 17, 2009 11:18 pm
Location: North East Coast

Postby ladajo » Wed Feb 08, 2012 9:36 pm

Well, I ran across this...

http://www.navair.navy.mil/osbp/index.c ... ost_id=119

and thought it was interesting.

See line #316.

Hmmm....

:D
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

Skipjack
Posts: 6045
Joined: Sun Sep 28, 2008 2:29 pm

Postby Skipjack » Wed Feb 08, 2012 10:29 pm

Well, I ran across this...

http://www.navair.navy.mil/osbp/index.c ... ost_id=119

and thought it was interesting.

See line #316.


Very encouraging! So it seems like they will be getting another 2 years of funding and 5 to 10 million USD more ? Or am I reading this wrong?
Kinda funny though that the Navy is spending the same amount of money on fusion research that they are spending on some furniture ;)

ladajo
Posts: 6204
Joined: Thu Sep 17, 2009 11:18 pm
Location: North East Coast

Postby ladajo » Wed Feb 08, 2012 11:05 pm

It would appear to be a place holder, but they normally do this with intention of floating a contract. The 1QFY12 part would seem to indicate another contract is imminent. How so, hard to tell.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

choff
Posts: 2432
Joined: Thu Nov 08, 2007 5:02 am
Location: Vancouver, Canada

Postby choff » Thu Feb 09, 2012 1:52 am

It mentions China Lake or Pt. Muga as an alternate site.
CHoff

mvanwink5
Posts: 1808
Joined: Wed Jul 01, 2009 5:07 am
Location: N.C. Mountains

Postby mvanwink5 » Thu Feb 09, 2012 2:52 am

It looks like enough money to keep the team from looking for employment elsewhere and reflects old ballpark yearly expenses. Certainly it is enough to fund WB-8.1 and some next level design work. If it were me, I would still want to see continuous operation before marshaling for a prototype size. It also gets them past November.
Best regards

PS Ladago, you really know how to find stuff, many thanks again.
Near term, cheap, dark horse fusion hits the air waves, GF - TED, LM - Announcement. The race is on.

bennmann
Posts: 227
Joined: Sun May 17, 2009 5:56 pm
Location: Southeast US

Postby bennmann » Thu Feb 09, 2012 5:20 am

New thread based on the NAVAIR funding placeholder? Or too soon? ladajo should do as he pleases.

KitemanSA
Posts: 6114
Joined: Sun Sep 28, 2008 3:05 pm
Location: OlyPen WA

Postby KitemanSA » Thu Feb 09, 2012 12:27 pm

Just went to double check and yup, this is the same contract as before. The contract already had a J&A for ~10M so this is nothing new.

Spreadsheet . . . N68936-09-C-0125
Recovery Site . . N68936-09-C-0125


Return to “News”

Who is online

Users browsing this forum: No registered users and 5 guests