Thanks so much for your remarks.
By the way, I have just noticed that the T3B can also be found in degrad.f
that is placed in the garfieldpp-5.0/Degrade directory.
For all runs so far, I have modified only magboltz.f setting T3B = 0.01 for Oxygen of 1%.
I suppose I should modify the degrad.f as well?
It is written there that:
C THREE BODY ATTACHMENT
C ***************************************************************
C ENTER HERE SCALING FACTOR FOR THREE BODY ATTACHMENT IN MIXTURES:
C FOR NORMAL SCALING T3B=1.0
T3B=1.0
C SCALING FACTOR NORMALLY PROPORTIONAL TO OXYGEN FRACTION
C IN RARE GAS MIXTURES
C
C***********************************************************
By the way, the 2 // plate simplified micromegas simulation reproduces very well the experimental results even if the geometry does not include the mesh element in a periodic repetition as in neBEM.
I am sharing the results where top right is our measured amplitude spectra on the pad and at the bottom the 2 plots from simulations concerning electrons at the end of drift and pad respectively.
I think the gain as indicated by simulations is on Fe peak ~ 4650.
The calculations also give:
Field intensity in the middle of drift region:
At y = 0.505 cm:
E = 0.3 kV/cm
Field intensity in the middle of avalanche region:
At y2 = 0.0025 cm:
E = 64 kV/cm
that agrees with literature for a field of ~ 65 kV/cm as it can be seen in:
So, if it not just a coincidence, there is a good matching between measurements and simulations for Ar/isobutane 5% for a gain ~ 4000-5000 at 65 kV/cm.
In the picture above are the results for a mixture of Ar/CO2 (93:7)% with the admixture of 1% O2.
Where top 3 plots are for Ar 93%, CO2 7%
middle 3 plots for Ar/CO2/O2 (92.07/6.93/1)% with T3B = 0.01
bottom 3 plots for Ar/CO2/O2 (92.07/6.93/1)% with T3B = 1
It is strange indeed that in the middle plots the gain as indicated by the #entries on the pad in the right one, is higher than the case where there is no O2 (pure Ar-CO2 93/7% → top plots). (???)
In the literature like: R Guida et al 2020 J. Phys.: Conf. Ser. 1498 012036
even 0.1% of O2 (1000 ppm) in a Ar/CO2 (70/30) gas mixture leads to a drop of ~ 50% in the gain…
The simulations, provided are correct, indicate that 1% of O2 increase the gain if T3B = 0.01 is used… I could provide code and gas files as well…
