[Clas12_high_luminosity] CLAS12 Luminositiy Upgrade Meeting - follow up

[Maurizio Ungaro]

Hi Whitney,

I was referring to the second order (radiated electrons) moller processes, I’m not sure if they are implemented in geant4, I thought they were in the low EM processes.

To calculate the occupancy, here are my two main ingredients:

1. the hit definition, which is tied up with the detector electronics, in particular its time window. In gemc all geant4 steps in a detector element within the TW constitute a hit.
You can find more details about this here: 

https://gemc.jlab.org/gemc/html/documentation/hitDefinition.html

2. the beam structure and event time window. At 10^35, for a time window of 250 ns, we have ~130K e- on a 5cm LH2 target. This constitutes one gemc event. These electrons are bunched up every 2 (or 4) nanoseconds, following CEBAF structure. A transverse size of 100 microns spreads the beam radially (uniformly). 
I ran 10K of these events (1.3B events) for each configuration. The R2 and R3 occupancy are scaled because their time window is 500 ns. 

You can find more details here:

https://gemc.jlab.org/gemc/html/documentation/generator/luminosity.html

The occupancy is then simply the average number of hits / event.

Hope this helps.
Mauri

> On Jan 25, 2016, at 7:30 PM, Whitney R. Armstrong <warmstrong at anl.gov> wrote:
> 
> Hi Maurizio,
> 
> Thanks for the information. What is not clear from the presentation is how exactly you arrive at a given luminosity.
> 
> Do you just calculate the flux of electrons for a given time interval and simulate that number of events? 
> The Moller process would be part of geant4's ionization process.
> 
> Cheers,
> Whit
> 
> 
> On Mon, Jan 25, 2016 at 01:38:54PM -0600, Maurizio Ungaro wrote:
>> Hi all, 
>> Following today’s discussion, you can find attached the latest (last week)
>> slides on the shield configurations.
>> 
>> Last week plots are also summarized online:
>> 
>> https://userweb.jlab.org/~ungaro/tmp/beamline/dc.html
>> 
>> Ongoing is another round of simulation with further improvements on the
>> beamline - results will be shown at the beamline meeting tomorrow. 
>> The new geometry can be found here:
>> 
>> https://github.com/gemc/detectors/tree/master/clas12/beamline
>> 
>> 
>> The torus geometry can be found here:
>> 
>> https://github.com/gemc/detectors/tree/master/clas12/magnets
>> 
>> 
>> 
>> The electronic time window are:
>> 
>> 
>> double TWINDOWR[3] = {250.0e-9, 500.0e-9, 500.0e-9};
>> 
>> 
>> The threshold use to produce the occupancy plot is 50 eV.
>> 
>> 
>> Finally, I’m investigating wether all moller processes are included in the
>> low-EM-energy in geant4. 
>> I will simulate clas12 setup at 6 GeV.
>> 
>> All this will be summarized in a CLAS note.
>> 
>> 
>> Cheers,
>> 
>> Mauri
>> 
>> 
>> 
> 
> 
> 
> -- 
> Whitney R. Armstrong