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I try to detect a flow of positive charged ions. These ions produce an electrical current in the order of 10^-12 Ampers. My question is that, what is the simplest set up for detecting these ions?

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Charged particles traveling in vacuum and hitting a metal box, When an ion hits the metal box, its charge is neutralized by an electron jumping from the metal on to the ion . That leaves a space amongst the electrons in the metal, and the electrons in the wire shuffle along to fill it.

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What is the setup? A solution, a wire, charged particles traveling in vacuum? Please give some more details... – Count Zero May 27 '12 at 11:27

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Since you try to measure pico-Amps, take a look at the Low Level Measurement Handbook (pdf) from Keithley.

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Is it possible to build an amplifier that amplifies 10^4 order? – peaceman May 27 '12 at 13:37
@Ehsan you may need to chain multiple stages together, but in general ... sure – suha May 27 '12 at 16:58
+!. What a great link, Suha – Rocket Surgeon May 27 '12 at 22:58
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The simpliest schematics is probably amplifier from any ion smoke detector. Connect base of n-p-n darlington (the one without internal resistors) to metal box and emitter to ground. Apply 50% of transistor rated c-e voltage (10..20v) through 1..10k resistor with LED.

Possible curcuit. For positive ions.

For fun, try 4-6 transistors in enourmous darlington chain with LED. It will work like "detector of everything". In my experiment it detected a lit match few feet away with "antenna" 1 inch long. (Sorry no proof of working in vacuum due to budget limitations)

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Could you please add a schematic of circuit that you say. I'm new in electrical engineering. – peaceman May 28 '12 at 5:20
Added. The transistors, especially first one should be from factory packaging and never handled by bare hands, only with gloves to maintain low leakage. Avoid spills of flux and never wash the assembly. It is pA build after all. – Rocket Surgeon May 28 '12 at 5:42
thanks for your response – peaceman May 28 '12 at 6:29
neato! Normally I shun Darlingtons but you bring up an interesting use case. +1. – Jason S May 28 '12 at 12:28

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