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

Electron Detection spectroscopy

  1. Jun 25, 2005 #1
    In the electron detection using Silicon Detector ,Liquid nitrogen is used to cool the system . why is it used. What is "sweating" which is caused if the detector is not in vaccum,when kept in liq. nitogen

    Thanking you in advance. :rofl:
  2. jcsd
  3. Jul 1, 2005 #2
    Hello--I don't know much about electron detection spectroscopy, but the reason why sensitive experiments are usually kept in cryogens (cooling the system) is to reduce thermal energy which might cause noise. (How does the electron detector work? Maybe the goal is to reduce thermal excitation of silicon electrons?) If the detector is not in vacuum but is cold, perhaps this "sweating" effect is just condensation of water from air?
  4. Jul 1, 2005 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I believe flip is right on both counts.

    Simply put, you want to be at temperatures much smaller than the band gap, lest you excite thermally rather than by the incident electrons - hence the liquid nitrogen.

    Sweating is merely the formation of condensation/frost on the outside of a cooled apparatus, that usually forms as a result of a thermal short to the (cooled) inside (often from insufficient evacuation).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook