L. Reuen

A DEPFET Based Beam Telescope With Submicron Precision Capability

For the detection of secondary vertices of long lived particles containing bottom and charm quarks at the International Linear Collider (ILC), a DEPFET pixel detector is one of the technologically favored options. In a DEPFET sensor a MOSFET pixel detector is integrated on a sidewards depleted silicon bulk sensor, thus combining the advantages of a fully depleted silicon sensor with in-pixel amplification. DEPFET pixel matrices have been characterized in a high energy particle beam. Since the DEPFET is a very high precision device, given its large S/N (> 100) and small pixel size (36 × 22 ¿m2), a DEPFET based pixel telescope consisting of 5 DEPFETs has been developed. The uncertainty on the predicted position for a device under test (DUT) positioned inside the telescope was found to be 1.4 ¿m with the existing device, due to the limited performance of two of the five DEPFET planes. A DEPFET telescope built of 5 modules equivalent to the best plane presented here, would have a track extrapolation error as low as 0.65 ¿m at the DUT plane.

Test Beam Characterization of 3-D Silicon Pixel Detectors

Three-dimensional (3-D) silicon detectors are characterized by cylindrical electrodes perpendicular to the surface and penetrate into the bulk material in contrast to standard Si detectors with planar electrodes on the top and bottom. This geometry renders them particularly interesting to be used in environments where standard silicon detectors have limitations, such as, for example, the radiation environment expected in an upgrade to the Large Hadron Collider at CERN. For the first time, several 3-D sensors were assembled as hybrid pixel detectors using the ATLAS-pixel front-end chip and readout electronics. Devices with different electrode configurations have been characterized in a 100 GeV pion beam at the CERN SPS. Here, we report results on unirradiated devices with three 3-D electrodes per 50times400 mum2 pixel area. Full charge collection is obtained already with comparatively low bias voltages around 10 V. Spatial resolution with binary readout is obtained as expected from the cell dimensions. Efficiencies of 95.9%plusmn0.1% for tracks incident parallel to the electrodes and of 99.9%plusmn0.1% for tracks incident at 15deg are measured. The homogeneity and charge sharing of the efficiency over the pixel area are measured.

Development of a prototype module for a DEPFET pixel vertex detector for a linear collider

For operation at a linear collider the excellent noise performance of depleted field effect transistor (DEPFET) pixels allows building very thin detectors with high spatial resolution and low power consumption. However, high readout speeds of 50 MHz line rate and 20 kHz for the full detector must be reached. A prototype system is presented, using a new DEPFET pixel matrix (128 /spl times/ 64 pixels), fast steering chips (Switcher II) for row wise operation and a fast current based readout chip (CURO II). The sensors with small linear DEPFET pixels (22/spl times/36 /spl mu/m/sup 2/) are optimized for fast readout and high spatial resolution. Measurements show that the complete removal of the accumulated signal charge from the internal gate (complete clear), which is fundamental for the foreseen readout mode, is feasible. The current based readout chip CUROII, containing current memory cells, pedestal subtraction and on chip zero suppression for a triggerless operation has been fabricated and tested. First results of a full prototype system are presented.

Performance of a DEPFET prototype module for the ILC vertex detector

For the detection of secondary vertices of long lived bottom and charm quarks at the proposed International Linear Collider (ILC) a DEPFET pixel detector is one of the favored technology options. DEPFET pixel sensors, in which the amplifying transistor structure is contained in the pixel cell itself on a fully depleted bulk, are unique devices in terms of their large signal and low noise capability and their obtainable spatial resolution with very thin detectors. DEPFET pixel prototype modules with close to ILC specifications have been tested in the laboratory and, for the first time, in a 6 GeV electron test beam. The different noise sources have been calculated and compared with the measured value of ENC/spl ap/225 e/sup -/ for the entire readout chain.

DEPFET Active Pixel Sensors

DEPFET pixels offer a unique possibility for a high resolution pixel vertex detector at a future linear collider (ILC) experiment. The key idea of DEPFET sensors is the integration of amplifying transistors into a fully depleted bulk. The excellent noise performance obtained through the low input capacitance in combination with the full signal from the depleted bulk leads to a large S/N ratio. The sensor itself can therefore be made very thin (50μm) without loss of efficiency. In this article the progress of the DEPFET development towards an ILC vertex detector is presented. Properties of prototype matrices and dedicated ASIC electronics have been characterized in various laboratory and test beam measurements. In particular a point resolution of less than 2 μm has been demonstrated (using 450 μm thick sensors). Based on these results larger matrices, improved readout and control electronics have been designed which are presently in production. In parallel software was developed to simulate the performance of a DEPFET based vertex detector in an ILC experiment.