Diamond – Tungsten Calorimeter LCAL-group : K. Afanasiev, V. Drugakov, E. Kouznetsova, W. Lohmann, A. Stahl Workshop on Forward Calorimetry and Luminosity Measurement In the TESLA Detector November 2002, DESY-Zeuthen

 Location  Requirements Detection and measurement of electrons and photons at small angles Fast beam diagnostic Improvement of the energy flow measurement in forward/backward direction Shielding of the inner part of the detector

 Beam-beam Background GUINEAPIG + BRAHMS ( for √s = 500 GeV ) : Per bunchcrossing : ~15000 e ± hits ~20 TeV of deposited energy (R,  )-distribution of the deposited energy: High radiation resistivity is required Two options for calorimeter technology : Heavy scintillator Diamond-tungsten sandwich

 CVD DIAMOND properties SiliconCVD-Diamond Resistivity,  ×cm 2.3×10 5 [b3] [f] Carrier density, cm -3 15×10 10 [b3]<10 3 [b3] Dielectric constant11.9 [b3]5.7 [f] Capacity (1 cm 2, 500  m), pF 3517 Leakage current, pA/mm Breakdown field, V/cm3×10 5 [b3]10 7 [f] Band gap, eV1.12 [b3]5.45 [f] Cohesive energy, eV/atom4.36 [b3]7.37 [b2] Energy/(e - -h pair), eV3.6 [b3]13 [b3] Mobility, cm 2 /(V×s) e-e [b3]1800 [b3] [f] h480 [b3]1200 [b3] [f] Saturation velocity, ×10 7 cm/s e-e- ~ 0.8 (?)2.7 [b1] h 1.0 [b1] Saturation field E s, V/cm e-e- E s = f(L) 1.24×10 4 [b1] h0.63×10 4 [b1] Average e - -h number per 100  m (for MIP) 9200 [b3]3600 [b3] Energy deposition per 100  m (for MIP), keV 4050 Charge collection distance d c,  m ; d c = f(l) Radiation length, cm9.4 [Oh]18.8[Oh] Moliere radius, cm Comparison to silicon :

 CVD DIAMOND properties Radiation hardness :

 Sandwich LCAL geometry Tungsten absorber + Diamond sensor R M ~ 1 cm Z - Segmentation : Tungsten 3.5 mm Layer = Diamond 0.5 mm (R,  ) - Segmentation :

 Sandwich LCAL background Average energy deposited in “bad” cells: ~ 7 GeV Dose expected for “bad” cells : ~10 MGy/year 250 GeV e - + BG :

 Sandwich LCAL recognition Algorithm : “Suspected” cells :  E CELL > 3  BG reasonable z-location Requirement of longitudinal chain of such cells Choice of a proper ADC : sensorPA/discrADC reconstruction

 Sandwich LCAL recognition Efficiency vs radius :

 Sandwich LCAL recognition Energy resolution vs radius :

 Sandwich LCAL recognition Polar angle resolution vs radius :

 Sandwich LCAL Recognition Calibration : Averaged energy resolution :

 Sandwich LCAL Recognition Averaged angular resolution :

 Diamond/W LCAL following steps : Real sensor test : to see mip-signal : ~1.5 fC  CONCLUSIONS sandwich diamond-tungsten calorimeters seems to be a promising technology high energetic e ±,  can be detected with reasonable efficiency even near the beam pipe energy and angular resolution for diamond-tungsten are good VV50-3