diamond – tungsten calorimeter
DESCRIPTION
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 13-14 November 2002, DESY-Zeuthen. Location. Requirements. - PowerPoint PPT PresentationTRANSCRIPT
Diamond – TungstenCalorimeter
LCAL-group : K. Afanasiev, V. Drugakov,
E. Kouznetsova, W. Lohmann,
A. Stahl
Workshop on Forward Calorimetry and Luminosity Measurement
In the TESLA Detector13-14 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 DIAMONDproperties
Silicon CVD-Diamond
Resistivity, ×cm 2.3×105 [b3] 1013-1016 [f]
Carrier density, cm-3 15×1010 [b3] <103 [b3]
Dielectric constant 11.9 [b3] 5.7 [f]
Capacity (1 cm2, 500 m), pF 35 17
Leakage current, pA/mm2 550 35
Breakdown field, V/cm 3×105 [b3] 107 [f]
Band gap, eV 1.12 [b3] 5.45 [f]
Cohesive energy, eV/atom 4.36 [b3] 7.37 [b2]
Energy/(e--h pair), eV 3.6 [b3] 13 [b3]
Mobility, cm2/(V×s)
e- 1350 [b3] 1800 [b3] - 2200 [f]
h 480 [b3] 1200 [b3] - 1600 [f]
Saturation velocity, ×107 cm/s
e- ~ 0.8 (?) 2.7 [b1]
h 1.0 [b1]
Saturation field Es, V/cm
e-
Es = f(L)1.24×104 [b1]
h 0.63×104 [b1]
Average e--h number per 100 m (for MIP)
9200 [b3] 3600 [b3]
Energy deposition per 100 m (for MIP), keV
40 50
Charge collection distance dc, m 60 - 250; dc = f(l)
Radiation length, cm 9.4 [Oh] 18.8[Oh]
Moliere radius, cm 5.28 12.31
Comparison to silicon :
CVD DIAMONDproperties
Radiation hardness :
www.desy.de/~ghodbane
Sandwich LCALgeometry
Tungsten absorber + Diamond sensor
RM ~ 1 cm
Z - Segmentation :
Tungsten 3.5 mm Layer = Diamond 0.5 mm
(R,) - Segmentation :
Sandwich LCALbackground
Average energy deposited in “bad” cells:
~ 7 GeV
Dose expected for “bad” cells :
~10 MGy/year
250 GeV e- + BG :
Sandwich LCALrecognition
Algorithm :
• “Suspected” cells : ECELL > 3 BG
reasonable z-location
• Requirement of longitudinal chain of such cells
Choice of a proper ADC :
sensor PA/discr ADC
reconstruction
Sandwich LCALrecognition
Efficiency vs radius :
Sandwich LCALrecognition
Energy resolution vs radius :
Sandwich LCALrecognition
Polar angle resolution vs radius :
Sandwich LCALRecognition
Calibration :
Averaged energy resolution :
Sandwich LCALRecognition
Averaged angular resolution :
Diamond/W LCALfollowing 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
y = -2.3952x - 0.0672
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VV50-3