Multiwire Proportional-Chamber doesn't work

[quark.expr]

Hi there,

I bulit a kind of Multiwire Proportional Chamber in my Institute to detect cosmic muons on sea level. The chamber consists of Plexiglas and contains a double capacitor. The cathodes are two copper plates and in-between the plates the anode which is a grid of wires. The distance between the anode to one of the cathode plates is 10mm, the distance between the wires is 2mm. I worked with a silver coated copper wire with a diameter of 0.1mm. The chamber is airthigt, and filled with a gas mixture of 90% Ar and 10% CO2, the pressure is 1 bar (100000 Pa).

I calculated the whole event, with the Energy transformation of the muons to Ionisation of the gas (Bethe-Bloch-Equation), the number electron/ion pairs produced, the amplification in the proportional range. I calculated a voltage puls, that I should measure, of more then 10 V with an impressed voltage of 2.5 kV.

The Problem: I impressed a voltage up to 2.5 kV with no result of any voltage puls.

What should I do now? Should I raise the voltage until there is a discharge? Should I change the distance between anode and kathode? or what else?

Thank you for your help.

 

[Astronuc]

Has one tested the chamber with a known beta or gamma source?

I think 2.5 kV should be enough, but would depend on the geometry.

Compare one's design with - http://www.iop.org/EJ/article/1742-6596/18/1/011/jpconf5_18_011.pdf?request-id=tCit3xln3BGjno4U3Ai7Kg.


Make sure the impedances are properly matched among cables and instruments, particularly with the detector cable and preamp.

 

[quark.expr]

I tested the chamber with a gamma source, but there was still no signal. The electric background noise is bigger than the signal. I made sure the that the impedances are properly matched. The one problem that could be is the circuit diagramm, and the way we are trying to measure the signal...do you know any proper ways of a configuration from any other measurements?

I atatched two pictures of the detector and the configuration.

I could change the distancde between the plate and the wire to about 1cm, if necessary. With a distance of 10cm I could impress a voltage up to 5okV.

What could I do else?

 

[quark.expr]

Finally caught the muons!

Hi there,

I finally measured the muons. I can measure 2 microsec long and 0.4 V high Impulses which get more by a factor of 3.5 with a radioactive Source. The as well get more with less screening.

If anybody is interested, contact me for more information.