[Halld-cpp] Fe55 signal in Argon

[Rory Miskimen]

Hi Beni, 

Thanks, yes, we’re going to look into this in more detail.   I’ve looked at this paper.   I know that at 5.9 keV about 90% of the total photo-electric effect cross section in Ar is from K-shell knockout, which is followed by emission of a 2.9 keV x-ray.  The absorption length of a 2.9 keV x-ray in argon is about 3 cm.   Since our cell is 1 x 2 x 10 cm^3, much of this energy does not get reabsorbed, and escapes. 

As soon as we finish the gas study tests we’re going to gang together 3 adjacent cells, to create a cell with effective size 3 x 2 cm^2, and we can test if the escape peak diminishes. 

Cheers,
Rory

> On Jun 11, 2015, at 3:54 PM, Beni Zihlmann <zihlmann at jlab.org> wrote:
> 
> 
> Hi All,
> 
> today we saw the energy response of the chamber to an Fe55 source.
> The escape peak should be much smaller than the main peak. In particular,
> the escape peak is a feature of the argon gas and should disappear if
> the argon is less than 70% of the gas mixture.
> 
> see for example http://arxiv.org/pdf/1307.6154.pdf figure 6.
> 
> cheers,
> Beni
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