Re: Inside Out Thermo Nuke



Phil Weldon wrote:
> By reflection at a grazing angle, the high Z outer casing creates the
> channel for the x-rays emitted by the initiating fission device.
>
> The 10 KV to 200 KV range of soft X-rays emitted by the initiating fission
> device are reflected when the grazing angle is less than 0.3 degrees (10 KV)
> to 0.015 degrees (200 KV).

I don't believe that grazing reflection is a plausible mechanism for
radation transport down the channel. Let's start with the best case of
10KeV, which is about what Carey cites for starting energy. Using your
figures, that requires a grazing angle less than 0.3 degrees.

I don't have much information on channel widths, but surely they must
be greater than 1cm. In the ideal case of X-rays traveling axially
down the secondary, and reflecting at 0.3 degrees, they would not cross
a 1cm channel and hit the other side until they had travelled a length
of 1.9m. A secondary isn't that long (Mike was 6m long, but would have
had a much wider channel). So any X-rays that reflect are at too
shallow of an angle to hit the other side of the channel before
reaching the end.

Any X-rays at a significant angle to the axis will see some curvature
to the outer radiation case wall, and will have a grazing angle greater
than 0.3 degrees. So only a tiny fraction of the solid angle with
which X-rays could enter the channel will reflect (perhaps one
millionth of it), so only that tiny fraction of the energy would be
reflected. And those X-rays won't hit the other wall before the end of
the channel. Simple geometry rules this mechanism out.

And then there are devices with spherical secondaries. There the outer
casing has curvature in all directions, so it is rather difficult to
get low grazing angles.

> Maybe these geometries don't exist in thermonuclear weapons, but I'd always
> considered it the justification of the channel arrangement since it would
> provide more even creation and heating of plasma than
> absorption/re-radiation down the channel.

Exactly the opposite is true. There is nothing in your reflection
mechanism that guarantees even distribution of energy down the channel.
There is uneven distribution by direct radiation based on the angle
subtended by an area of outer casing, which differs with distance down
the channel. The reflected energy reaching a given ablation surface
will depend on the distribution of the direct radiation being
reflected. The dependence may be slightly weaker than for the original
distribution, but will still be a strong function of distance down the
channel.

On the other hand, absorption/re-radiation inherently tends to produce
an even distribution of energy down the channel. You have a hohlraum,
or black-body cavity, which tends toward equilibrium with all the
internal walls reaching the same temperature. You may consider this a
slow process, which it would be at everyday temperatures. But
radiation emission increases as the 4th power of temperature, and we
are talking 10-100 million K. That is 20 orders of magnitude more
radiation density than anything you are used to. Even if you consider
the total energy of the primary as being 10 orders of magnitude higher
than what you are used to, that still leaves the rate of emission 10
orders of magnitude faster (and of course it transmits at the speed of
light between emission and re-absorption).

Symmetrical compression of the secondary requires a very even
distribution of energy across the ablation surface.
Absorption/re-radiation automatically tends to give you that
distribution, by the statistics of thermodynamics. Reflection does not.

.

Relevant Pages

  • Re: Inside Out Thermo Nuke
    ... >> By reflection at a grazing angle, the high Z outer casing creates the ... >> channel for the x-rays emitted by the initiating fission device. ... >> device are reflected when the grazing angle is less than 0.3 degrees (10 ...
    (sci.physics.fusion)
  • Re: Inside Out Thermo Nuke
    ... | radation transport down the channel. ... >> By reflection at a grazing angle, the high Z outer casing creates the ... >> device are reflected when the grazing angle is less than 0.3 degrees (10 ...
    (sci.physics.fusion)
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  • Re: Basic quetion about domain model and design pattern
    ... loading the channel object into the application context. ... on the Type object called GetProperties ... One note on this technique tough, reflection is slow. ...
    (microsoft.public.dotnet.general)