[SOLVED] Fusion chain reaction?

eastmond@yahoo.com

Hi,

I was wondering what would happen if a roughly 10 MeV proton or
neutron was fired into a large dense target consisting of a mixture of
deuterium and tritium - let's say several cubic metres of gas held at
high pressure but low temperature so that it is almost at the density
of liquid water. I imagine that the target is large and dense enough
so that the projectile particle is guaranteed to scatter off a
deuterium or tritium atom rather than pass straight through the
target.


Would the high energy particle transfer enough kinetic energy to a
number of deuterium or tritium atoms so that they scatter with a high
kinetic energy and fuse with other deuterium/tritium atoms and thus
produce tritium, helium-3, helium-4 and further protons and neutrons
with varying kinetic energies?

Could one end up with a self-sustaining chain reaction occurring at a
relatively low temperature?

This would be different from the standard fusion schemes in which the
whole of the fuel is heated up to a temperature high enough to produce
fusion reactions.

John

Uncle Al

eastmond@yahoo.com wrote:
>
> Hi,
>
> I was wondering what would happen if a roughly 10 MeV proton or
> neutron was fired into a large dense target consisting of a mixture of
> deuterium and tritium - let's say several cubic metres of gas held at
> high pressure but low temperature so that it is almost at the density
> of liquid water. I imagine that the target is large and dense enough
> so that the projectile particle is guaranteed to scatter off a
> deuterium or tritium atom rather than pass straight through the
> target.
>
> Would the high energy particle transfer enough kinetic energy to a
> number of deuterium or tritium atoms so that they scatter with a high
> kinetic energy and fuse with other deuterium/tritium atoms and thus
> produce tritium, helium-3, helium-4 and further protons and neutrons
> with varying kinetic energies?
>
> Could one end up with a self-sustaining chain reaction occurring at a
> relatively low temperature?
>
> This would be different from the standard fusion schemes in which the
> whole of the fuel is heated up to a temperature high enough to produce
> fusion reactions.

Light element fusion requires the product of density, time, and
temperature exceed a critical value. Fusion spontaneously
disassembles without propagation (second order reaction) unless
actively confined - implosion, gravitation, external EM fields,
possibly inertia. Deuterium is nobody's idea of inertial confinement
- including deuterated polyethylene. You only have a few shakes (tens
of nanoseconds) to get the job done before the mass thermally expands,
reaction rate dropping as the inverse square of concentration.

You could dump in muons. That works on paper and nowhere else.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2

Joseph Warner

"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:46E89E93.C0A22070@hate.spam.net...
> eastmond@yahoo.com wrote:
>>
>>> Light element fusion requires the product of density, time, and
> temperature exceed a critical value. Fusion spontaneously
> disassembles without propagation (second order reaction) unless
> actively confined - implosion, gravitation, external EM fields,
> possibly inertia. Deuterium is nobody's idea of inertial confinement
> - including deuterated polyethylene. You only have a few shakes (tens
> of nanoseconds) to get the job done before the mass thermally expands,
> reaction rate dropping as the inverse square of concentration.
>
> You could dump in muons. That works on paper and nowhere else.
>
As I remember that doesn't work on paper. The muon's half-life is too short.

J. J. Lodder

Uncle Al <UncleAl0@hate.spam.net> wrote:

> Light element fusion requires the product of density, time, and
> temperature exceed a critical value. Fusion spontaneously
> disassembles without propagation (second order reaction) unless
> actively confined - implosion, gravitation, external EM fields,
> possibly inertia. Deuterium is nobody's idea of inertial confinement
> - including deuterated polyethylene. You only have a few shakes (tens
> of nanoseconds) to get the job done before the mass thermally expands,
> reaction rate dropping as the inverse square of concentration.
>
> You could dump in muons. That works on paper and nowhere else.

It does work in a bubble chamber.
In fact, muon catalysed fusion was discovered experimentally,
instead of predicted on a piece of paper.

The only thing that's wrong with it
is that muons are too expensive.

Best,

Jan

Edward Ruden

Colliding a beam of deuterium ions into a target loaded with tritum is
a common way to produce a burst of high energy neutrons via D-T fusion
(there are applications for that). The shortcoming of this approach is
that net nuclear energy gain is impossible this way because the fusion
cross section is relatively small, and not every collision results in
one. Once the D starts bouncing around inside the target, momentum
transfer to the T's due to collisions causes the D to loose energy too
fast for the stray fusion reaction to make up for it, on average.

This is why the target must be very hot. If the target is hot enough
(10 keV or more), and in thermal equilbrium, collisions no longer
result in an average loss of energy, and the energy is effectively
confined within the plasma. If it's hot enough and confined long
enough (the Lawson Criterion), net energy gain is achieved.

eastmond@yahoo.com

On 14 Sep, 13:36, Edward Ruden <rudenbz...@yahoo.com> wrote:
> Colliding a beam of deuterium ions into a target loaded with tritum is
> a common way to produce a burst of high energy neutrons via D-T fusion
> (there are applications for that). The shortcoming of this approach is
> that net nuclear energy gain is impossible this way because the fusion
> cross section is relatively small, and not every collision results in
> one. Once the D starts bouncing around inside the target, momentum
> transfer to the T's due to collisions causes the D to loose energy too
> fast for the stray fusion reaction to make up for it, on average.
>

Maybe the problem is that the deuterium ions are loosing their energy
by
scattering off other more highly charged nuclei in the target rather
than
the tritium. Perhaps if one only used pure tritium for the target then
the
scattering cross-section would be comparable to the fusion cross-
section.

John

J. J. Lodder

Joseph Warner <Joseph.D.Warner@nasa.gov> wrote:

> "Uncle Al" <UncleAl0@hate.spam.net> wrote in message
> news:46E89E93.C0A22070@hate.spam.net...
> > eastmond@yahoo.com wrote:
> >>
> >>> Light element fusion requires the product of density, time, and
> > temperature exceed a critical value. Fusion spontaneously
> > disassembles without propagation (second order reaction) unless
> > actively confined - implosion, gravitation, external EM fields,
> > possibly inertia. Deuterium is nobody's idea of inertial confinement
> > - including deuterated polyethylene. You only have a few shakes (tens
> > of nanoseconds) to get the job done before the mass thermally expands,
> > reaction rate dropping as the inverse square of concentration.
> >
> > You could dump in muons. That works on paper and nowhere else.
> >
> As I remember that doesn't work on paper. The muon's half-life is too short.

It's long enough for producing many muon-catalyzed fusion events.
The problem is producing muons cheaply enough.
When some clever soul invents a way to produce muons
for a few hundred MeV apiece the proces
will become quite practical.

Jan

Joseph Warner

"J. J. Lodder" <nospam@de-ster.demon.nl> wrote in message
news:1i4fjql.kjluji1gjo4yxN@de-ster.xs4all.nl...
> Joseph Warner <Joseph.D.Warner@nasa.gov> wrote:
>
>> "Uncle Al" <UncleAl0@hate.spam.net> wrote in message
>> news:46E89E93.C0A22070@hate.spam.net...
>> > eastmond@yahoo.com wrote:
>> >>
>> >> >
>> > You could dump in muons. That works on paper and nowhere else.
>> >
>> As I remember that doesn't work on paper. The muon's half-life is too
>> short.
>
> It's long enough for producing many muon-catalyzed fusion events.
> The problem is producing muons cheaply enough.
> When some clever soul invents a way to produce muons
> for a few hundred MeV apiece the proces
> will become quite practical.

I may be wrong and my information was based on my knowledge from 1977 when I
did a literature search on "exotic" atoms where a muon would replace an
electron in a D-T or D-D molecule that would draw the two nuclei closer
together so that the wavefunctions of the nuclei would overlap and cause
fusion. I knew at that time "hot" muons could induce the fusion because the
of time dilation. But I don't think thermallized muons have a lifetime long
even to cause many fusion events. If there has been more data since 1975 on
the topic, it would be interesting to see what it is and how it impacted the
prior conclusions.