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question.gif  Charge transfer coefficient calculations in the GEMProcessor [message #1746] Fri, 29 May 2009 06:16
bakul
Messages: 1
Registered: January 2009
Location: University of Siegen, Ger...
Hello,

I have a question about GEM simulation in MarlinTPC (GEMProcessor). Please, correct me if I am wrong, I am assuming that libgem.cc (MarlinTPC/trunk/digitisation/src/libgem.cc) does all the calculations of the charge transfer coefficients. The code for electron extraction efficiency calculation starts with the following ‘if’ condition (line 64):
if  ( ( field / holefield( gemvoltage, 0, 0 ) - PAR_y_eext ) <= pow( PAR_r_eext, (1/PAR_s_eext) ) )

Is that condition correct? Is it required to subtract the parameter ‘y’ from the field ratio before that comparison? According to the published papers from Martin Killenberg, et al., the condition should be: E_ext/E_hole <= r^1/s. If the value of ‘PAR_y_eext’ is zero, it doesn’t matter, but in case of some gas-mixtures, the parameter files (MarlinTPC/trunk/simulation/inputs/) have a non-zero values of this parameter. Wouldn’t that affect the results?
Another thing I don’t understand is the reason for setting the external fields to zero when computing the hole field. I notice, almost everywhere the function ‘holefield’ is called with the last two parameters as zero: holefield( gemvoltage, 0, 0 )
Why is it like that?

Thanks,
Bakul.


Bakul Gaur
University of Siegen
 
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