[Lex Computer & Tech Group/LCTG] Nuclear fusion...

Sun Dec 18 16:40:13 PST 2022

Michael & All

Measuring the fusion output energy for Laser Inertial Confinement is not so
trivial -- there is no calorimeter
When you fuse D-T in a Laser ICF system everything happens really fast and
most of what is known is based on code

   1. First you have 192  beams of IR photons from the output of the
   flashlamp pumped Nd glass Final Amplifiers]
   2. Each of those 192 separate beams is then upconverted with some losses
   from the IR to the UV
   3. The UV beams enter the test chamber [10m dia] and then enter
   the Hohlraumn from the two ends [at several angles from the axis]
   4. The clock starts at  0+ ns -- the input pulse is over at about 8ns
   with the bulk of the UV energy delivered in less than 5 nsec [from about 3
   to 8 ns]
   5. The UV photons strike the inner surface of the Gold plated depleted
   Uranium hohlraum [roughly a cylinder]
   6. The Au vaporizes and then is heated further to become a plasma at
   about [300 ev or about 3M C]
   7.  The Au plasma at 300 eV emits soft x-rays inward -- the depleted U
   is there just to keep the Au plasma from expanding too quickly

In the center of the Holhlraum there is a hollow spherical diamond target
capsule [about 1 mm dia] containing D-T as gases or cryo-gas frost frost on
the inner surface of the capsule
The outer surface of the target capsule is coated to absorb the soft x-ray
flux

      8.    The ablating surface expands and the core of the capsule reacts
by imploding compressing the fusion fuel to enormous density and heating it
enough to start fusing first D-T and the later D-D
                       all the above happens about 9 ns after the start of
the laser pulse

basically the above [from 6 to  is very similar to the Teller-Ulam design
for the first true Thermonuclear Devices except the x rays come from the U
or Pu Fission Trigger explosion

fusing lasts for a fraction of a ns
fast D-T and then slightly slower  D-D neutrons escape outward
they are preceded by gamma rays and x-rays
and followed by escaping alpha particles
finally there is mechanical motion of the remnants of the experiment
capsule and hohlraum
all this is confined with a 10 m dia evacuated chamber

Lots of detectors located around the target chamber and some within it
measure neutrons, x-rays, alpha particles and do some imaging
All the data then is fed into a massive hydrodynamic simulation [same as
used for weapons test and verification]
Output power is calculated by the simulation calibrated by measured neutron
flux and spectra and some measurements of compression [hard x ray imaging]

In reality the only hard numbers are P[of the Xenon flash lamps used to
pump the Nd glass final amplifiers] and some measure of the output laser
power [tapped off the laser final amplifiers and upconverters]

see for example
  Experiments conducted in the burning plasma regime with inertial fusion
implosions J. S. Ross1,∗ , J. E. Ralph1,∗ , A. B. Zylstra1,∗ , A. L.
Kritcher1 , H. F. Robey2 , C. V. Young1 , O. A. Hurricane1
,...................
https://arxiv.org/pdf/2111.04640.pdf

 nature  nature physics  letters  article
Letter
Open Access
Published: 26 January 2022
Design of inertial fusion implosions reaching the burning plasma regime
A. L. Kritcher, C. V. Young, H. F. Robey, C. R. Weber, A. B. Zylstra, O. A.
Hurricane, D. A. Callahan, J. E. Ralph, J. S. Ross, K. L. Baker, D. T.
Casey, D. S. Clark, T. Döppner, L. Divol, M. Hohenberger, L. Berzak
Hopkins, S. Le Pape, N. B. Meezan, A. Pak, P. K. Patel, R. Tommasini, S. J.
Ali, P. A. Amendt, L. J. Atherton, …G. B. Zimmerman

https://iopscience.iop.org/article/10.1088/1741-4326/ab1ecf/pdf

A lot of the above is "kinda take it at face value" since neither the raw
data from the diagnostics nor the code are available [as they have a huge
overlap with the weapons stewardship efforts]

Ted

On Sun, Dec 18, 2022 at 2:11 PM Michael Alexander <mna.ma at yahoo.com> wrote:

> Mitch - Good for the WSJ, giving perspective beyond the hype.  Same for
> Physics Today (less surprising, given its audience).
>
> Question:  How did LLNL measure (quantitatively) the fusion output
> energy?  I may have missed a description.
>
>     – Mike Alexander
>
>
> On Sunday, December 18, 2022, 9:19 AM, Mitchell I. Wolfe <
> mwolfe at vinebrook.com> wrote:
>
> The WSJ had a recent article
> <https://www.wsj.com/articles/when-will-fusion-be-ready-for-prime-time-watch-these-three-numbers-11671159158?st=38p8tjeiybncyrb&reflink=desktopwebshare_permalink>
> about this. They differentiated between the scientific break-even
> (achieved), the engineering break-even (not even close), and the economic
> break-even.
>
> -- Mitch
>
> On 2022-12-13 18:45, Ted Kochanski wrote:
>
> George
>
> Yes -- the pump energy was between 300 and 400 MJ
>
> Ted
>
> On Tue, Dec 13, 2022 at 5:49 PM George Gamota <ggamota at stma-llc.com>
> wrote:
>
> They omitted to include the energy used to pump the lasers, which in
> magnitude was much larger than the output.
>
>
>
> *From:* LCTG <lctg-bounces+ggamota=stma-llc.com at lists.toku.us> *On Behalf
> Of *carllazarus at comcast.net
> *Sent:* Tuesday, December 13, 2022 4:02 PM
> *To:* 'Ted Kochanski' <tedpkphd at gmail.com>; 'Drew King' <
> dking65 at kingconsulting.us>
> *Cc:* 'Lex Computer Group' <lctg at lists.toku.us>
> *Subject:* Re: [Lex Computer & Tech Group/LCTG] Nuclear fusion...
>
>
>
> I read that "The LLNL said a team at its National Ignition Facility (NIF)
> conducted the first controlled fusion experiment in history on December 5,
> achieving what is known as "scientific energy breakeven.""
>
> What is counted in "scientific energy" and what does it omit?
>
>
>
> -- Carl
>
>
>
> *From:* LCTG <lctg-bounces+carllazarus=comcast.net at lists.toku.us> *On
> Behalf Of *Ted Kochanski
> *Sent:* Monday, December 12, 2022 7:32 PM
> *To:* Drew King (dking65 at kingconsulting.us) <dking65 at kingconsulting.us>
> *Cc:* Lex Computer Group <lctg at lists.toku.us>
> *Subject:* Re: [Lex Computer & Tech Group/LCTG] Nuclear fusion...
>
>
>
> All,
>
>
>
> Be careful about Hype versus simple reality
>
>
>
> Yes it does appear that LLNL National Ignition Facility may have hammered
> a poor defenseless target pellet into producing more fusion energy than was
> absorbed by the pellet
>
> so technically Q>1 [about 1.2]
>
>
>
> BUT -- and I'll admit a bias toward Magnetic Confinement Fusion -- the
> Energy used to produce the Energy delivered to the pellet was not part of
> the calculation
>
>
>
> While Magnetic Fusion with Superconducting Magnets in a Tokamak
> configuration probably need Q>2 to be a credible Eureka Moment -- The
> energy needed to fire the lasers probably needs a Q>30
>
>
>
> Ted
>
>
>
>
>
> On Mon, Dec 12, 2022 at 5:30 PM Drew King (dking65 at kingconsulting.us) <
> dking65 at kingconsulting.us> wrote:
>
> All,
>
> The Verge: A "scientific breakthrough" in nuclear fusion? How to watch the
> announcement tomorrow.
>
> https://www.theverge.com/2022/12/12/23505416/nuclear-fusion-scientific-breakthrough-how-to-watch-announcement-biden
>
> --
> Drew King
>
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