Diamond pixel VELO. To cope with higher radiation dose, LHCb might consider CVD diamond pixels for the VELO. Piggy back on ongoing developments (ATLAS, RD42, …) Polycrystyalline vs Single-Crystal CVD diamond. One possibility is to make an “all-diamond” ladder – cost compared to Silicon?
To cope with higher radiation dose, LHCb might consider CVD diamond pixels for the VELO. • Piggy back on ongoing developments (ATLAS, RD42, …) • Polycrystyalline vs Single-Crystal CVD diamond. • One possibility is to make an “all-diamond” ladder – cost compared to Silicon? • Another possibility is to just put diamond where you need the high radiation tolerance • Particle fluence reduced by ~10x in going from 1 cm3 cm (JC) • Smaller area may make single-crystal CVD diamond more viable • Exploration of “edgeless detectors” • would reduce the inactive material in active area • Would allow Si pixel and diamond pixel to be “butted” up close to one another on a single ladder. (see pages 3-4) • Some indication that can get active area ~50um from edge (see Totem NIM A paper http://dx.doi.org/10.1016/j.nima.2009.01.056) • Impact of small square frame of inactive area where Si pixel sensor and diamond sensor meet up? (see layouts on next pages)
Diamond vs Silicon ~ pCVD achieving about 10Kelectrons, saturates there…(carrier mobility saturates) scCVD signal grows with thickness(mobility doesn’t saturate up to~mm)… but only small piecesgrown so far Room temp. operation(but need cooling for electronics) LHCC-2005-003
Hybrid Si/Diamond DetectorPrecision X View Front Back
Hybrid Si/Diamond Detector Precision Y View Front Back
Edgeless detectorshttp://dx.doi.org/10.1016/j.nima.2009.01.056 (NIMA) I
Summary • We could build on RD42/ATLAS R&D on pCVD/scCVD to instrument innermost region of VELO (or entire VELO?) • Many pros for diamond.. • Rad hard, no cooling required, stable capacitance with radiation, low leakage current no thermal runaway.. • Signal at fluence~2x1016/cm2 is about 1/3 of starting value Low noise electronics • How close to edgeless can they be fabricated? • Same question for Si pixels?