5 Solid State Detectors
183
Fig. 5.45 Principle of a macro-pixel cell: A DEPFET located at the centre of a drift detector serves
as storage and readout device
New DEPFET Developments
The DEPFET concept allows a variety of further functionalities that have partially
been proven experimentally but not yet implemented into a large area pixel
detector:
(a) As signal charge is not destroyed by the readout process this charge can be read
repeatedly and the measurement precision improves with the square root of the
number of measurements. This has been verified with a pair of neighbouring
DEPFET transistors arranged in such a way as to allow the transfer of
signal charge from one internal gate to the other and in reverse direction. A
measurement precision of 0.25 electrons has been achieved independently of
the amount of signal charge [39].
(b) Gatable DEPFETs [40] are developed for applications in High Time Resolution
Astronomy (HTRA) and Adaptive Optics. They collect signals in preselected
time intervals only, whereas the charge generated outside of these gate periods
are drained towards a clear electrode.
183
Fig. 5.45 Principle of a macro-pixel cell: A DEPFET located at the centre of a drift detector serves
as storage and readout device
New DEPFET Developments
The DEPFET concept allows a variety of further functionalities that have partially
been proven experimentally but not yet implemented into a large area pixel
detector:
(a) As signal charge is not destroyed by the readout process this charge can be read
repeatedly and the measurement precision improves with the square root of the
number of measurements. This has been verified with a pair of neighbouring
DEPFET transistors arranged in such a way as to allow the transfer of
signal charge from one internal gate to the other and in reverse direction. A
measurement precision of 0.25 electrons has been achieved independently of
the amount of signal charge [39].
(b) Gatable DEPFETs [40] are developed for applications in High Time Resolution
Astronomy (HTRA) and Adaptive Optics. They collect signals in preselected
time intervals only, whereas the charge generated outside of these gate periods
are drained towards a clear electrode.