Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Critical mass for nuclear fusion

  1. May 13, 2018 #1
    Hello, can you please confirm this statement "Nuclear fusion does not require a minimum mass to occur (critical mass), which is instead a characteristic limit of fission. So you can make small fusion bombs as much as you want."?
    Thanks!
     
  2. jcsd
  3. May 13, 2018 #2

    anorlunda

    Staff: Mentor

  4. May 13, 2018 #3
    Thanks! In this case we are considering the ignition with a laser or relativistic electron beam, so is it true that we can have a micro-bomb according to you?
     
  5. May 13, 2018 #4

    anorlunda

    Staff: Mentor

    Who is we? It sounds like you're working on a SF story, is that right?

    In theory, the answer to that question is yes. But in practice nobody has come even close to making that succeed.
    One idea for a fusion power plant was to implode fuel pellets the size of a grain of a sesame seed. It is still a dream, not reality.
     
  6. May 13, 2018 #5
    Oh yes, I didn't mean that I'm working on this kind of fusion bomb :D I only meant that I am considering this system of ignition in the reasoning I am doing with other people.
    Thanks for your help!
     
  7. May 15, 2018 #6

    berkeman

    User Avatar

    Staff: Mentor

    Have you read about Inertial Confinement Fusion with lasers? You should look at the size of the target spheres and read how much energy is released per shot. I don't know if that qualifies as your "bomb" or not. Also, I guess you need to include the size of the building housing the laser system in the "size" of the "bomb"... :smile:

    https://cdn.arstechnica.net/wp-cont...plifier_at_the_National_Ignition_Facility.jpg

    640px-Preamplifier_at_the_National_Ignition_Facility.jpg
     
  8. May 15, 2018 #7
    Thank you! Actually, I'm considering this kind of bombs for advanced space propulsion systems, not on the Earth. Anyway thanks for your suggestion.
     
  9. May 15, 2018 #8

    anorlunda

    Staff: Mentor

  10. May 18, 2018 #9
    For fusion reactions there has to be a sufficient quantity of very tightly confined plasma.
    Not that much though, less than a gram will do the trick, IIRC
     
  11. May 20, 2018 #10
  12. May 22, 2018 #11
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted