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

I Intensity of the background neutron radiation

  1. Mar 28, 2016 #1

    Garlic

    User Avatar
    Gold Member

    Hello everyone,
    What is the average intensity of the background neutron radiation?
     
  2. jcsd
  3. Mar 28, 2016 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    That will depend on your experiment.
     
  4. Mar 28, 2016 #3

    Garlic

    User Avatar
    Gold Member

    Sorry, but I don't understand what do you mean by that. Why should the intensity change depending on my experiment?
     
  5. Mar 28, 2016 #4

    mathman

    User Avatar
    Science Advisor
    Gold Member

    Neutron background
    Most of the natural neutron background is a product of cosmic rays interacting with the atmosphere. The neutron energy peaks at around 1 MeV and rapidly drops above. At sea level, the production of neutrons is about 20 neutrons per second per kilogram of material interacting with the cosmic rays (or, about 100-300 neutrons per square meter per second). The flux is dependent on geomagnetic latitude, with a maximum at about 45 degrees. At solar minimums, due to lower solar magnetic field shielding, the flux is about twice as high vs the solar maximum. It also dramatically increases during solar flares. In the vicinity of larger heavier objects, e.g. buildings or ships, the neutron flux measures higher; this is known as "cosmic ray induced neutron signature", or "ship effect" as it was first detected with ships at sea.[11]

    Above from Wikipedia
     
  6. Mar 29, 2016 #5

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Every piece of material in your experiment will (a) interact with high-energetic particles passing through (e.g. cosmic radiation) and release neutrons, and (b) absorb some neutrons. In addition, your experiment will have some shielding from the atmosphere above (depends on its height above sea level) and maybe from rock above (for unterground experiment).
    And that is just the influence on the raw neutron spectrum, the influence on your measurement devices is more complicated.

    How can the background of anything not depend on your experiment?
     
  7. Mar 29, 2016 #6
    I take it that your question is in regards to your earlier post regarding the measurement of low activity fast neutron sources. Since the energy of the background neutron flux peaks at 1 MeV. and may decrease rapidly above that I would still investigate the possibility of the need of a shield consisting of a high content hydrogen material as polyethylene or paraffin to thermalize those neutrons and reduce their possible interference with your subject radiation. Your source you say is 0.1 Bq so even small background radiation will be of concern in order to achieve data with good accuracy.
     
  8. Mar 29, 2016 #7

    Garlic

    User Avatar
    Gold Member

    Thank you for your replies, I understand it better. :smile:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Intensity of the background neutron radiation
  1. Background radiation (Replies: 1)

  2. Neutron radiation (Replies: 1)

Loading...