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Taking current from an insulator?

  1. Dec 10, 2011 #1
    taking current from an insulator??

    I am working on a project that uses a Faraday cup. Its consists of a metallic cylinder(pipe like) with an electrode at the bottom.The ions enter the cylinder and hit the electrode.The resulting current is carried away from the electrode to an amplifier by a wire .Now.the electrode that i am using is an insulator. So how do i provide the electrical connection.the electrode being an insulator,will it give any charge for the wire to carry
     
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  3. Dec 10, 2011 #2

    Bobbywhy

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    Re: taking current from an insulator??

    A Faraday detector consists of a metal cup, that is placed in the path of the particle beam. The aerosol has to pass the filter inside the cup. The filter has to be isolated. It is connected to the electrometer circuit which measures the current.

    Insulators do not permit current flow. Conductors, like wire, for example, pass current. How can an electrode be an insulator? Sounds contradictory. Can you post a diagram of your apparatus? Do you have a reference source for your experiment?
     
    Last edited: Dec 10, 2011
  4. Dec 11, 2011 #3
    Re: taking current from an insulator??

    www.chm.bris.ac.uk/ms/theory/detection.html [Broken]
    in the above website its given that the BeO ,CsSb,GaP can be used as electrode material and BeO is definitely an insulator....
     
    Last edited by a moderator: May 5, 2017
  5. Dec 11, 2011 #4

    Bobbywhy

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    Re: taking current from an insulator??

    The Faraday cup or cylinder electrode detector is very simple. The basic principle is that the incident ion strikes the dynode surface which emits electrons and induces a current which is amplified and recorded.

    The dynode electrode is made of a material like CsSb, GaP or BeO. The secondary emission from the dynode electrode produces one level of signal amplification.

    Those secondary electrons represent the desired signal and are collected by an electrical lead (often the center conductor of a coaxial cable). It conducts the current to a measuring instrument. Detection can be as simple as an ammeter in the conducting lead to ground or a voltmeter or oscilloscope displaying the voltage developed across a resistor from the conducting lead to ground.
     
  6. Dec 12, 2011 #5
    Re: taking current from an insulator??

    to what is this conducting lead connected??the electrode??
     
  7. Dec 12, 2011 #6

    Bobbywhy

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    Re: taking current from an insulator??

    The material inside the Faraday Cup (FC) that emits electrons (secondary emission) when ions impact on it is called the dynode electrode.

    The reliable operation of a FC as a detector depends on the ability of the device to recapture those electrons ejected when energetic particles strike its interior dynode electrode.

    In the below tech note a graphite cup is used to collect those electrons. The output braided wire is attached to the back side of the graphite.

    http://www.scribd.com/doc/20191210/Faraday-Cup-Tech-Note
     
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