1. Update on Ecal simulation
Dr. Mauro Raggi Sapienza Universita’ di Roma
PADME ECal meeting LNF, 17 January 2017

2. Simulating effect of crystals gap
In order to understand the constraints on the mechanical assembly of the PADME Ecal it is very important to study the effect of dead spaces.
PADME MC has been modified to include TiO2 based paint and a paint surface of 100um surrounding each crystal.
M. Raggi PADME Ecal
09/05/2019

3. Simulation of the gap in PADMEMC
New MC configuration with:
Crystals 21x21x230mm3
Reflective paint 100mm
Vacuum gap (50mm)
To study the effect on the Ecal performance due to the gap the size of the gap has been changed from 50mm to 500mm
No changes of the paint thickness
A 30K photon of different energies ( ) MeV have been fired on the Ecal to study the energy containment and the energy resolution.
PAMDE MC crystals gaps
Crystal
TiO2 paint 100um
M. Raggi PADME Ecal
09/05/2019

4. Effect of the angle
Due to the non pointing geometry of the PADME ecal the energy leakage and energy resolution depend on the azimuthal angle
Each simulation generates a spot of 5cm diameter centered at at a precise position
Two different central positions where used
X=0, Y=12
X=12 , Y=12
M. Raggi PADME Ecal
09/05/2019

5. Position of the spots
Due to the non pointing geometry of the PADME ecal the energy leakage and energy resolution depend on the azimuthal angle
Each simulation generates a spot of 5cm diameter centered at user defined position
Two different central positions where used
X=0, Y=17
X=12 , Y=12 1 2
M. Raggi PADME Ecal
09/05/2019

6. E coll. and E resolution spot1
M. Raggi PADME Ecal
09/05/2019

7. E coll. and E resolution spot2
The lower azimuthal angle gives a worst energy collection and resolution with larger gaps
The total dead region is given by:
200mm paint + gap
M. Raggi PADME Ecal
09/05/2019

8. Ecal and SAC radiation dose
We tried to simulate the total dose of radiation accumulated by Ecal and SAC exposed to MeV pot (e+ on target)
The integrated energy in each of the Ecal crystals was simulated and the result converted into radiation dose.
400M e+ on target fully simulated and energy deposit scaled to 1E13 e+
Energy converted from MeV to Joule (*1E6*1.6E-19)
To convert in Gy we used the average weight of a single crystal 0.7Kg so just divide by 0.7 (not properly true most of the energy is released in the first 1-2 cm)
M. Raggi PADME Ecal
09/05/2019

9. Dose in Gy in the SAC 1E13 e+
In the central crystal the accumulated dose is ~1Gy
The dose scales by ~ one order of magnitude per column
M. Raggi PADME Ecal
09/05/2019

10. X vs Z energy profile Energy fraction deposit in the X vs Z profile
M. Raggi PADME Ecal
09/05/2019

11. Ecal accumulated dose
In the Ecal central crystals the accumulated dose is ~10-4 Gy per 1013 e+
There is a visible effect of the synchrotron radiation on the left side of the Ecal
M. Raggi PADME Ecal
09/05/2019

12. Conclusion on dose rate
On all the padme detector the dose rate accumulated during 1 year of run ~1E13 pot is modest
Order 1Gy is the maximum dose on the SAC crystals
Dose rate on the Calorimeter in below 1E-3 Gy in one year of data taking
The simulation does not include for the moment the beam dump
Non negligible radiation dose may come from back-splash from beam dump
Need to define beam dump geometry before repeating the simulation
M. Raggi PADME Ecal
09/05/2019

13. Simulating shower development
To better understand the test beam data is necessary to study the distribution of the energy deposit in the 5x5 crystals prototype
After measuring the threshold induced by the pedestal during the data taking the amount of crystals to be included in the cluster can be extracted for different positron energy
4 different energy have been simulated using
M. Raggi PADME Ecal
09/05/2019

14. Fraction of energy in each crystal
500MeV
250MeV
10MeV
100MeV
M. Raggi PADME Ecal
09/05/2019

15. Energy deposit in each crystal
500MeV
250MeV
100MeV
50MeV
10MeV
M. Raggi PADME Ecal
09/05/2019

16. Conclusions on shower development
Given a minimum energy threshold of MeV all the crystals except the inner 9 have an average signal below or near the threshold.
There is no need to use a cluster including 25 crystals
In general we may expect worst resolution in data wrt 9 crystals
For energies below 50 MeV is most probably better to use the seed crystal only.
The calorimeter performance may benefit more from a lower thr (higer gain) wrt to extended linearity range.
M. Raggi PADME Ecal
09/05/2019