Doses and bunch by bunch fluctuations in BeamCal at the ILC Eliza Teodorescu FCAL Collaboration Meeting June 29-30, 2009, DESY-Zeuthen, Germany

RiRi RoRo ReRe 30 X 0 Suport tube (Iron) Absorber (W) Electronics Sensor Dead Area R To R i = 20 mm R 0 = 150 mm R e = 50 mm R Ti = 200 mm R To = 250 mm sandwich em. calorimeter : 30 layers of 1 X 0 3.5mm W + 0.3mm sensor ~ channels of ~0.8 R M ~ 20mm < R < 150mm (200 electronics 250 suport tube) each sensor layer divided into 8 sectors BeamCal R Ti

Simulate Collision: Guineapig (nominal parameter set) e+e- pairs ASCII File Simulate detector: BeCaS1.2 ROOT file BeCaS A Geant4 BeamCal simulation (A.Sapronov) Can be configured to run with: OUTPUT full GEANT4 simulation => energy, particle distributions … INPUT OUTPUT The simulation chain different crossing angles (corresponding geometry is chosen): here: 14 mrad magnetic field (solenoid, (Anti) DID, use field map): here: Anti DID

energy deposition vs. calorimeter depth: - the maximum of the shower in the 5 th and 6 th layers, ~30 GeV/bx - Edep < 5 GeV/bx in the first sensor layer and in the second half of BeamCal Electron-positron background 5 BX1 BX

Energy depositions along the sensor’s radius (layer 6) -statistics of 5 bunch-crossings -most of the energy is deposited in the innermost region of the sensor, then gradually decreases toward the outer radii - energy deposition decreases to less than 1% at a radius of about 80 mm - less than 0.1% at 100 mm Electron-positron background 5 BX

the absorbed dose in the sensor layers e+e- DOSE 3x10^11 BX/year 5 BX

The dose at different distances from the beampipe Closest to the beampipe : dose vs. layer number distribution : - the dose rises from 4x10^5 Gy/year (first layer) to 6x10^6 Gy/year (maximum), then slowly decreases to less than 2x10^4 Gy/year in the last layers of BeamCal. e+e- DOSE 4x10 5 Gy/year (front) 6x10 6 Gy/year (max) 2x10 4 Gy/year (back) R = 20 mm-28 mm 5 BX

Increase in the dose toward the final layers of BeamCal e+e- DOSE 2 causes: - natural developement of the shower - backscattered particles (from QD0) The innermost rings of the sensors are most affected R = 150 mm-158 mm R = 100 mm-108 mm The dose at different distances from the beampipe 5 BX

- remove QD0 from simulation: dose slowly decreases e+e- DOSE R = 100 mmR = 150 mm 5 BX

Bunch by bunch fluctuations Christian Grah Energy deposition and standard deviation for the whole calorimeter - one BX -closest to the beampipe – highest energy deposition ( ~10 MeV/pad) - for the outer pads ~keV - there are pads with no energy deposition each pad – independently read -> interesting to see how energy deposition fluctuates from bunch to bunch, in each pad For this: (r,  ) energy distributions First: one BX (comparison with older results provided by Ch. Grah) 1 BX

Bunch by bunch fluctuations 40 BX - Simulate more bunch crossings and find the medium energy deposition - In this case: N=40 BX - Calculate the standard deviation:  Energy deposition: tens of MeV – innermost pads keV – rest of the pads   0.1 MeV – innermost pads KeV – rest of the pads Mean E dep  What happens for more bunches?

Bunch by bunch fluctuations Energy deposition for a single high energetic electron GeV initial energy - hits the first layer of BeamCal

Layer 6 Layer 12 Layer 25 E tot = GeVE tot = 2.9x10-5 GeVE tot = GeV Bunch by bunch fluctuations Shower development throughout the calorimeter – 250 GeV electron

Bunch by bunch fluctuations Superimpose the high energetic electron over the backgroud

Layer 6Layer 12 Bunch by bunch fluctuations All BX  Typical layer of average background with high energetic electron  Typical layer of background standard deviation with high energetic electron

The distribution of the average deposited energy and standard deviation in a pad (layer 12)

Thank you!