Taking current from an insulator?

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Discussion Overview

The discussion centers around the use of an insulator as an electrode in a Faraday cup setup, exploring the implications for current flow and electrical connections in the context of particle detection. Participants examine the principles of operation for Faraday cups and the materials used in their construction.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions how an insulator can function as an electrode, noting that insulators do not permit current flow and asking for clarification on the setup.
  • Another participant references a source that lists materials like BeO, CsSb, and GaP as electrode materials, asserting that BeO is indeed an insulator.
  • A participant explains the basic principle of a Faraday cup, detailing how incident ions strike the dynode surface, leading to secondary electron emission and current amplification.
  • There is a query about the connection of the conducting lead, seeking clarification on whether it connects to the electrode.
  • A later reply discusses the importance of recapturing electrons ejected from the dynode electrode and mentions the use of a graphite cup for this purpose, along with a reference to a technical note.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of using an insulator as an electrode, with some asserting it is contradictory while others provide examples of insulator materials used in similar contexts. The discussion remains unresolved regarding the practical implications of using an insulator in this application.

Contextual Notes

There are limitations regarding the definitions of electrode materials and their conductive properties, as well as the specific configurations of the Faraday cup setup that may affect the discussion.

d.sonali20
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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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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?
 
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www.chm.bris.ac.uk/ms/theory/detection.html
in the above website its given that the BeO ,CsSb,GaP can be used as electrode material and BeO is definitely an insulator...
 
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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.
 


to what is this conducting lead connected??the electrode??
 


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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