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[Ross Corliss <rcorliss AT mit.edu>]

Hi Hugo,

Though eventually that would be strictly correct, I think we are not very 
sensitive to that detail.  The energy loss across the length of the tpc 
(assume path of 100cm) goes from 210keV for a MIP to 428keV, small compared 
to the scales we're concerned with.

We could for the moment get the approximately correct primary ionization 
regardless of the HIJING by scaling the TPC hit->eion by:
double gasCorrection=( 0.50 * Ne_dEdx + 0.50 * CF4_dEdx)/( 0.90 * Ne_dEdx + 
0.10 * CF4_dEdx)

This would give us the amount of energy that would have been deposited in the 
proper gas, and all will proceed correctly, save that at the end of its path 
the MIP will have 200keV more energy than it should, and slightly less 
deflection of its path.

Chris, can you confirm the energy loss (or the gas mixture) assumed in the 
current hijing events?

Are there other impacts we need to consider?

-Ross
> On Sep 1, 2020, at 2:08 PM, Hugo Pereira Da Costa via sPHENIX-calibration-l 
> <sphenix-calibration-l AT lists.bnl.gov> wrote:
> 
> Hi Ross, others
> 
> Thinking more about this Gas change: I guess that means that all Hijing 
> simulations from Chris need to be redone (due to the ionization/cm change) 
> correct ?
> 
> Is this really what we want to do, now, with the pressing deadlines ?
> 
> 
> 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/cmI
>> 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
>>>> 
>>>> 
>>>> ----------------------------------
>>>> 
>>>> Meeting URL
>>>> https://bluejeans.com/676999731?src=join_info
>>>> 
>>>> Meeting ID
>>>> 676 999 731
>>>> 
>>>> Want to dial in from a phone?
>>>> 
>>>> Dial one of the following numbers:
>>>> +1.408.419.1715 (United States(San Jose))
>>>> +1.408.915.6290 (United States(San Jose))
>>>> (see all numbers - https://www.bluejeans.com/premium-numbers)
>>>> 
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