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[Hugo Pereira Da Costa <hugo.pereira-da-costa AT cea.fr>]

On 9/1/20 4:44 PM, Ross Corliss wrote:

      Hi Hugo et al.

As always, Prakhar's webpage is very useful:  http://skipper.physics.sunysb.edu/~prakhar/tpc/HTML_Gases/split.html (pertinent snippet attached)

From his plot, at 400V/cm, I estimate 40um/sqrt(cm) transverse diffusion at 1.4T, 120um/sqrt(cm) longitudinal diffusion.

-Ross

Thanks a lot !

(I did not have the full link to Prakhar's web page. Just the one for 90/10, as documented in the eletron drift code:

https://www.phenix.bnl.gov/WWW/p/draft/prakhar/tpc/HTML_Gas_Linear/Ne_CF4_90_10.html

This one is very usefull indeed

Hugo

On Sep 1, 2020, at 5:07 PM, Hugo Pereira Da Costa via sPHENIX-calibration-l <sphenix-calibration-l AT lists.bnl.gov> wrote:

Hi Ross,

Thanks for the updated numbers.

The other two numbers we need for updating the code with the new gaz mixture is the longitudinal and transverse diffusion for electrons (in cm/sqrt(cm)). Do you have them on top of your mind ? Otherwise I can look them up.

On 9/1/2020 12:02 PM, Ross Corliss via sPHENIX-calibration-l wrote:

Thanks, Hugo and all who attended.

Per discussion in the meeting today, future spacecharge simulations will use Ne:CF4 50:50 gas, with the following parameters:

double Ne_dEdx = 1.56;   // keV/cm
double CF4_dEdx = 7.00;  // keV/cm
double Ne_NTotal = 43;    // Number/cm
double CF4_NTotal = 100;  // Number/cm

double dEdx=Ne_dEdx*0.5+CF4_dEdx*0.5;
double NTot=Ne_NTotal *0.5+CF4_NTotal *0.5;
these produce an expected 71.50 e-/cm for MIP tracks.
double ionMobility=1.65; //cm^2/(V*sec)
double elecDriftVelocity=8;//cm/us)

the elecDriftVelocity is essentially the same for 50:50 and 90:10 (if you have a more precise number, please feel free to propose it).  The ionMobility, however, has changed by a factor of two, and the ionization is 50% higher.

To keep the overall gain the same, the amplification gain should be scaled by the ratio 48.7/71.5 -- the 90:10 ionization per cm over the 50:50 ionization per cm.


-Ross

On Sep 1, 2020, at 10:47 AM, Hugo Pereira Da Costa via sPHENIX-calibration-l <sphenix-calibration-l AT lists.bnl.gov> wrote:

Friendly reminder: we meet in 15 minutes. Talk to you soon !

Hugo


On 8/31/20 8:45 AM, Hugo Pereira Da Costa via sPHENIX-calibration-l wrote:

 Dear all,
Last week it was decided that the next meeting dedicated to space charge distortions in the TPC wil occur tomorrow, Sept. 1st, at 11AM EST
It will cover activities related to both the TPC monitoring detector (Outer Tracker) and space charge calibration software.

Outer Tracker specific matters, if any, will be discussed first.

The indico page is at https://indico.bnl.gov/event/9302/
contributions are welcome.

Connection details are below.

Best,


Hugo


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