2 research outputs found
Signal and noise of Diamond Pixel Detectors at High Radiation Fluences
CVD diamond is an attractive material option for LHC vertex detectors because
of its strong radiation-hardness causal to its large band gap and strong
lattice. In particular, pixel detectors operating close to the interaction
point profit from tiny leakage currents and small pixel capacitances of diamond
resulting in low noise figures when compared to silicon. On the other hand, the
charge signal from traversing high energy particles is smaller in diamond than
in silicon by a factor of about 2.2. Therefore, a quantitative determination of
the signal-to-noise ratio (S/N) of diamond in comparison with silicon at
fluences in excess of 10 n cm, which are expected for the
LHC upgrade, is important. Based on measurements of irradiated diamond sensors
and the FE-I4 pixel readout chip design, we determine the signal and the noise
of diamond pixel detectors irradiated with high particle fluences. To
characterize the effect of the radiation damage on the materials and the signal
decrease, the change of the mean free path of the charge
carriers is determined as a function of irradiation fluence. We make use of the
FE-I4 pixel chip developed for ATLAS upgrades to realistically estimate the
expected noise figures: the expected leakage current at a given fluence is
taken from calibrated calculations and the pixel capacitance is measured using
a purposely developed chip (PixCap). We compare the resulting S/N figures with
those for planar silicon pixel detectors using published charge loss
measurements and the same extrapolation methods as for diamond. It is shown
that the expected S/N of a diamond pixel detector with pixel pitches typical
for LHC, exceeds that of planar silicon pixels at fluences beyond 10
particles cm, the exact value only depending on the maximum operation
voltage assumed for irradiated silicon pixel detectors