About filled gas inside a Geiger Muller meter

[aznsaiyan1029]

Hi,

I have a dumb question about the filled gas inside a Geiger Muller meter. I know it is considered as a gas detector. It requires a filled and quench gas for the probe. My question is: where does the gas get injected into for like a pancake probe. (Let's use Ludlum Model: 44-9 as example). How often do you have to refill the gas in the probe. Thanks.

 

[davenn]

How often do you have to refill the gas in the probe. Thanks.

as far as I'm aware, as with any other G-M type tubes ( who-ever the manufacturer), they are factory gassed and sealed.
there shouldn't be any leakage. If the tube is damaged and it leaks, then you are in for a replacement tube

neither of my 2 detector tubes are regassableDave

 

[Astronuc]

Hi,

I have a dumb question about the filled gas inside a Geiger Muller meter. I know it is considered as a gas detector. It requires a filled and quench gas for the probe. My question is: where does the gas get injected into for like a pancake probe. (Let's use Ludlum Model: 44-9 as example). How often do you have to refill the gas in the probe. Thanks.

One may have to contact the manufacturer. I suspect one would have to return the pancake detector to Ludlum.

The 44-9 is described as a halogen quenched GM detector.
http://ludlums.com/images/stories/data_sheets/M44-9.pdf

Fill Gas

The pressure of the gas inside the GM detector is usually a few tenths of an atmosphere. By reducing the pressure below atmospheric, the strength of the electric field necessary to reach the Geiger-Mueller region, and hence the required operating voltage, is lowered. The reduced pressure also increases the drift velocity of the positive ions towards the cathode and thereby reduces the dead time.

The gas of a Geiger Mueller detector consists of two components: a fill gas and a quench gas.

The fill gas is usually neon but other gases are sometimes used, e.g., helium, argon, or krypton.

There are two main types of quench gas: halogen quench gases and organic quench gases Chlorine is the most common halogen quench gas, but bromine is also used. Although the textbooks usually mention alcohol as an example of an organic quench gas, isobutane is far more common. A halogen quenching agent is used if the fill gas is neon, argon or krypton, while helium filled tubes usually employ an organic quench gas.

Ref: https://www.orau.org/ptp/collection/GMs/introgms.htm

For more general information
http://www.canberra.com/literature/fundamental-principles/pdf/Gamma-Xray-Detection.pdf

During my university program, we used GM/proportional counters with P10 (0.9 Ar, 0.1 CH₄) gas.