# Measuring Tiny changes in Electric Field Strength

#### jonlg_uk

Hi all I am looking to measure minute changes in electric field strength. I found this article http://www.physorg.com/news74876394.html" [Broken] which describes how scientists at harvard isolated a single electron in a highly evacuated, absolute zero chilled chamber and manipulated its movement using electrodes.

I have been thinking about doing something similar to solve the problem of measuring such tiny changes in electric field. I would like to create an electron trap, cost effectively. I basically need a FIXED amount of charge in the form of a "ball of electrons" or a "ring of electrons". I then want to control the movement of the electrons using electrodes like the scientist did. Does any one have any ideas of how to do this cost effectively.

Any one got any other ideas how to measure these minute changes in electric field strength?

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#### cragar

Maybe you could do what Robert Millikan did and spray oil droplets into an electric field and balance the charges against gravity. And then maybe push them around with a magnet. I know this isn't an electron trap but it might help. Or maybe if you have an electron gun accelerate the electrons over an electric potential and push them around using the Lorentz force . These are just some ideas .

#### jonlg_uk

Maybe you could do what Robert Millikan did and spray oil droplets into an electric field and balance the charges against gravity. And then maybe push them around with a magnet. I know this isn't an electron trap but it might help. Or maybe if you have an electron gun accelerate the electrons over an electric potential and push them around using the Lorentz force . These are just some ideas .
Hi cragar, thanks for your ideas, that is outside the box thinking. Unfortunately the Millikian oil drop experiment has fundamental problems associated with it. First of all you are using a heavy particle i.e an oil drop with a radius of ~0.1um. That adds to the momentum at which it travels at and hence the sensitivity is limited. Also there is a limiting factor of air viscosity.

Also using any type of magnets are out of the question as they have poor temp coefficents and drift more than the electric fields.

Any one got any more ideas?

#### f95toli

Gold Member
What do you mean by "cost effectively"? The kind of experiment you are describing (I guess you need a Penning trap of some sort) requires fairly well-equipped lab and a lot of expertise; it is most definitely not something you can try at home, the vacuum equipment alone will cost you tens of thousands of dollars.

#### jonlg_uk

What do you mean by "cost effectively"? The kind of experiment you are describing (I guess you need a Penning trap of some sort) requires fairly well-equipped lab and a lot of expertise; it is most definitely not something you can try at home, the vacuum equipment alone will cost you tens of thousands of dollars.
Yeh something like a penning trap would be ideal. However it would need to be custom built to adapt a range of electric fields. I would want to measure the variations in fields created by say a 1kV DC power supply right upto say a 60kV.

By cost effectively I don't want to spend more than \$15k dollars ...

#### jonlg_uk

Does anyone have any other ideas? I am open to all types of new and existing methods

#### jonlg_uk

Does anyone have any other ideas? I am open to all types of new and existing methods

#### Zarqon

Trapping and controlling single electrons is VERY difficult, and also costly. At the end of the article you linked, they even state it took 20 years and half a dozen PhD's to do it. The reason is that an electron is so light, that basically anything you can think of disturbs it so much it won't get trapped, let alone cooled properly.

I would say that you are much better off with trapping ions, rather than electrons, as this is much easier and has been done by a lot more groups. Ion traps have also been shown to be useable for detecting electric fields with high precision, although the voltage you specified is fairly large. Just note however, that even ion trapping takes a good amount of expertise and money to get going, so it won't be easy either.

#### jonlg_uk

Thanks for your replies, I am aware of the difficulties of ion/electron traps. Does anyone have any other ideas apart from an ion traps?

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