Z-Pinch Renaissance

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

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williatw
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Re: Z-Pinch Renaissance

Postby williatw » Mon Aug 26, 2019 4:37 pm

Skipjack wrote:I love the Fusion Driven Rocket. It is foil liner compressed FRCs. It has a lot of thrust compared to other fusion engine designs and a Isp of 5000 is still plenty good. That said, if the Sheared Flow Stabilized Z- Pinch works, it would have this design beat in terms of Isp and thrust, which is quite crazy.


I am not an engineer Skipjack BS degree in Chemistry. But I remember from molecular kinetics that the higher the exhaust velocity (ISP is exhaust velocity divided by g) the higher the temperature. And ISP of 356,800 seconds (from the posted link for Z-pinch using D-He3) corresponds to a likely exhaust/plasma temperature well into the millions of degrees. Even if the plasma isn't coming in contact with the walls of the rocket at that temp. it (the plasma) would radiate EM intensely. Probably well into the UV range if not maybe soft X-rays; don't know. A thrust of 3.3×105 N corresponding with a stated power output of 3.3×1012W indicates a large throughput of such super-heated plasma. How much supplemental shielding/coolant would that take and how much would that add to the mass of our Z-pinch fusion rocket? The beauty of John Slough's design is that it masses at I believe around 100 tons. He obviously wanted something that could be launched into orbit by current rocket technology. Having said that there is no reason with Musk's reusable BFR on the horizon that Slough's design couldn't be scaled larger; nuclear pulse rockets actually get more efficient with larger size/mass. A larger collapse radius for the coils of Lithium would produced longer acceleration times/faster velocity/higher compression temperature/pressure insuring more complete fusion for instance. That might increase ISP/thrust considerably; also it seems that Slough's approach is more doable with current technology.
Last edited by williatw on Mon Aug 26, 2019 5:26 pm, edited 1 time in total.

Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Mon Aug 26, 2019 4:47 pm

I don't want to have this thread drift too much off topic. I just want to add that I love MSNW's Fusion Driven Rocket design. I think it is amazing, since it does get a lot of thrust and has none of the problems you mentioned. I am not sure about the temperature problems of the Z- Pinch design. As for being mature. It seems that the SFS Z- Pinch is developing really quickly and the potential is huge. Meanwhile the FDR has seen very little funding in recent years and it is very different from Helion's Fusion Engine design (which has been making great progress). So I am not sure whose approach is more "doable". I think both have merit and both should be looked into.
What excites me about the Z- Pinch approach is that it has (indirect) funding through ZAP's work and it could have a very high T/W ratio, which is also important.

Giorgio
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Re: Z-Pinch Renaissance

Postby Giorgio » Mon Aug 26, 2019 5:34 pm

Same feelings. I guess that before the end of the year we should know more.
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Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Wed Sep 25, 2019 1:14 am

Uri and his team will present a lot of interesting new papers at the 61st Annual Meeting of the APS Division of Plasma Physics.
This one is standing out to me:
Zap Energy Inc. (ZEI) is scaling the sheared-flow stabilized (SFS) Z-pinch toward fusion reactor conditions. The UW and LLNL collaborated on the Fusion Z-Pinch Experiment (FuZE), sited at the UW. FuZE has demonstrated long-duration D-D fusion production periods of 8 μs [Zhang {\em et al}., PRL 2019], thousands of times longer than the 1 ns MHD m=0 (sausage) and m=1 (kink) instability growth times. FuZE has reached 300 kA pinch currents, 1-2 keV ion temperatures, 1−2×1023 m−3 densities, and neutron yields of >10^5 neutrons / pulse (for 20\% D2 / 80\% H2 admixtures). The UW and LLNL are presently upgrading the FuZE capacitor bank power supplies to push to 400 kA pinch currents. ZEI and the UW are teaming to measure electron temperatures on these 400 kA pinches. A new device will be built at ZEI with the goal of reaching equivalent scientific breakeven (scaling D-D operating conditions to “equivalent” Q if it were operated instead with D-T) at approximately 600 kA pinch currents. Status, plans, and reactor embodiment designs will be presented.


http://meetings.aps.org/Meeting/DPP19/Session/JP10.122

Judging by their progress over previous years, we "might" be seeing them reach "equivalent scientific breakeven" some time next year, or the year after that. That would put them ahead of contenders like TAE, TE and GF and most others (with the exception of Helion and maybe two or three others).
Hope that their presentation will be made public. Would be great to see where it is going.
Very exciting!
Last edited by Skipjack on Fri Oct 11, 2019 1:13 pm, edited 1 time in total.

Giorgio
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Re: Z-Pinch Renaissance

Postby Giorgio » Wed Sep 25, 2019 2:21 am

This is just published and related to FuZe investigation and characterization of the produced neutron flux:

"Measurements of temporally- and spatially-resolved neutron production in a sheared-flow stabilized Z-pinch"
https://www.sciencedirect.com/science/article/pii/S0168900219312173

Unfortunately is behind a paywall, so I couldn't read it.



Abstract

A novel approach using multiple scintillator detectors is applied to measure temporally- and spatially-resolved neutron production in the Fusion Z-pinch Experiment (FuZE) device, a Sheared-Flow Stabilized (SFS) Z-pinch. Diagnosing neutron production from FuZE is important for determining if fusion is thermonuclear and whether the FuZE device can be scaled toward reactor conditions. Absolute yields of up to 2 × 10^5 neutrons per discharge are measured with calibrated plastic scintillator detectors operating in pulse-counting mode.
Neutron emission durations of up to ~8 us are inferred by recording the time difference between the first and last pulses for each discharge. Multiple scintillator detectors located at different positions with respect to the fusing plasma are used to demonstrate that the axial extent of the neutron producing region is comparable to the device volume. Scintillator detectors are well-suited as neutron diagnostics for FuZE and other plasma devices with similar yields and emission durations. Increasing the neutron yield, duration, and volume of the neutron emitting region within the plasma column are significant experimental objectives for FuZE.
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Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Wed Sep 25, 2019 3:33 pm

Giorgio wrote:This is just published and related to FuZe investigation and characterization of the produced neutron flux:

From what I gather is just more confirmation of the neutron production in FuZe and that these neutrons are indeed thermonuclear in nature.
I am excited to see them move on to higher currents and a new machine. Will be interesting to see where 400kA will take them. It seems that the neutron production at 200 kA was better than what was originally expected, but I might be misinterpreting what I read.

Giorgio
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Re: Z-Pinch Renaissance

Postby Giorgio » Wed Sep 25, 2019 5:16 pm

Skipjack wrote:From what I gather is just more confirmation of the neutron production in FuZe and that these neutrons are indeed thermonuclear in nature.

The abstract of the paper seems to hint so. That would be indeed a welcome confirmation and a sure boost on the expectations for the higher power machine.
I will try to dig with some of my sources to see if anyone has access to the full paper.

Skipjack wrote:I am excited to see them move on to higher currents and a new machine. Will be interesting to see where 400kA will take them. It seems that the neutron production at 200 kA was better than what was originally expected, but I might be misinterpreting what I read.

If the 400kA will confirm the trend of the results obtained with the 200kA machine, than with their new 600kA machine we might indeed have an unexpected winner in this fusion race, which would be amazing if we consider the simplicity of this machine.
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Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Wed Sep 25, 2019 11:50 pm

From what I have seen, they are already at 300kA with the current setup, but they need to upgrade the power supply for 400 kA.

Giorgio
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Re: Z-Pinch Renaissance

Postby Giorgio » Thu Sep 26, 2019 8:01 am

Skipjack wrote:From what I have seen, they are already at 300kA with the current setup, but they need to upgrade the power supply for 400 kA.


I didn't notice that in the start..... its weird, because all the results they listed for this 300kA pinch (1-2 keV ion temperatures, 1-2x10^23 m-3 densities and neutron yields of >10^5 neutrons / pulse) are exactly the same values that they reported in the Arxiv paper for the 200 kA value.
I hope that us a typing mistake or that they will release more information during the meeting.
If indeed the 200kA and 300kA results are same (or very similar), than the expected improvement in neutron flux that was theorized in the Arxiv paper didn't materialize. Now I am even more eager to get my hands on these two papers....
A society of dogmas is a dead society.

Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Thu Sep 26, 2019 8:22 pm

Giorgio wrote:
Skipjack wrote:From what I have seen, they are already at 300kA with the current setup, but they need to upgrade the power supply for 400 kA.


I didn't notice that in the start..... its weird, because all the results they listed for this 300kA pinch (1-2 keV ion temperatures, 1-2x10^23 m-3 densities and neutron yields of >10^5 neutrons / pulse) are exactly the same values that they reported in the Arxiv paper for the 200 kA value.
I hope that us a typing mistake or that they will release more information during the meeting.
If indeed the 200kA and 300kA results are same (or very similar), than the expected improvement in neutron flux that was theorized in the Arxiv paper didn't materialize. Now I am even more eager to get my hands on these two papers....

I don't think the the actual 300kA results are in the papers yet. They just mentioned in several recent presentations that they are now operating at 300 kA and are going to increase to 400 kA. They probably did the most tests at 200 kA when they were working on establishing that their neutrons really were thermonuclear in nature. Then moved on to increase the currents for a few shots, measure results, then increase currents again and so on and so forth. I would assume that once they do reach 400kA, they will do more shots at that current again to have a large basis of experiments for the basis of a new series of publications. Don't forget that such publications have a lot of lead time and they are a small team. So they need to make sure they spend their time wisely.

Giorgio
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Re: Z-Pinch Renaissance

Postby Giorgio » Fri Sep 27, 2019 4:15 am

Skipjack wrote:I don't think the the actual 300kA results are in the papers yet.


Indeed yesterday I spent some time searching several sources and it seems that they didn't publish any 300kA result yet. They just published the 200kA results and announced that they have reached 300kA, withholding the results.
As you suggested, they probably want to get assurance from the 400kA experimental runs before releasing more data, and indeed it makes sense.
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AcesHigh
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Re: Z-Pinch Renaissance

Postby AcesHigh » Tue Oct 01, 2019 3:43 pm

Skipjack wrote:I do not know where people are seeing 10 million Isp. I read an Isp of ~360,000 seconds and 330 kN of thrust for the D+He3 configuration.


http://adsabs.harvard.edu/abs/2018APS..DPPC11163S
Building on the ZaP, ZaP-HD, and FuZE projects, scaling studies will be presented of an SFS Z-pinch as a fusion space thruster, which generates high exhaust velocities ( 10^7 m/s) and high thrust ( 10^6 N) with low system mass, as will be shown through calculations that account for input power, repetition rate, and duty cycle.

daveklingler
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Re: Z-Pinch Renaissance

Postby daveklingler » Tue Oct 01, 2019 6:24 pm

AcesHigh wrote:
Skipjack wrote:I do not know where people are seeing 10 million Isp. I read an Isp of ~360,000 seconds and 330 kN of thrust for the D+He3 configuration.


http://adsabs.harvard.edu/abs/2018APS..DPPC11163S
Building on the ZaP, ZaP-HD, and FuZE projects, scaling studies will be presented of an SFS Z-pinch as a fusion space thruster, which generates high exhaust velocities ( 10^7 m/s) and high thrust ( 10^6 N) with low system mass, as will be shown through calculations that account for input power, repetition rate, and duty cycle.


To be accurate, that's an exhaust velocity of 10 million, and an Isp of roughly 1/10 that. So just ho hum.

A DC-X-sized rocket with that drive could only have 731 km/s of delta-v.

Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Tue Oct 01, 2019 7:20 pm

daveklingler wrote:
AcesHigh wrote:
Skipjack wrote:I do not know where people are seeing 10 million Isp. I read an Isp of ~360,000 seconds and 330 kN of thrust for the D+He3 configuration.


http://adsabs.harvard.edu/abs/2018APS..DPPC11163S
Building on the ZaP, ZaP-HD, and FuZE projects, scaling studies will be presented of an SFS Z-pinch as a fusion space thruster, which generates high exhaust velocities ( 10^7 m/s) and high thrust ( 10^6 N) with low system mass, as will be shown through calculations that account for input power, repetition rate, and duty cycle.


To be accurate, that's an exhaust velocity of 10 million, and an Isp of roughly 1/10 that. So just ho hum.

A DC-X-sized rocket with that drive could only have 731 km/s of delta-v.

That can't be right. An Isp of 1 million seconds (even 360,000 seconds that I read) is huge. 360k seconds is 1000 times the efficiency of the SpaceX Raptor engine.
I did the math a while ago and with two of these engines, it would have enough DV to launch a Dragon 2 capsule (with slightly longer trunk) from Earth and get all the way to the Moon and back with propulsive braking and a constant acceleration of 1.2 g.

Giorgio
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Re: Z-Pinch Renaissance

Postby Giorgio » Wed Oct 02, 2019 2:07 am

The numbers are probably right, but according the way of working of the FuZe reactor is seems more to be an "Impulse ISP" than a prolonged time working engine ISP.
If you get a shot every 10 seconds it still is a pretty impressive ISP value for space application, but nowhere useful to get out of earth gravity well.
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