Fusion chain reaction?

  1. [SOLVED] Fusion chain reaction?

    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
     
  2. jcsd
  3. 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
     
  4. "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.
     
  5. 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
     
  6. 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.
     
  7. 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
     
  8. 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
     
  9. [SOLVED] Fusion chain reaction?

    "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.
     
Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook

Have something to add?