The DELPHI silicon strip microvertex detector with double sided readout

Abstract

The silicon strip Microvertex detector of the DELPHI experiment at the CERN LEP collider has been recently upgraded from two coordinates (R only) to three coordinates readout (R and z). The new Microvertex detector consists of 125952 readout channels, and uses novel techniques to obtain the third coordinate. These include the use of AC coupled double sided silicon detectors with strips orthogonal to each other on opposite sides of the detector wafer. The routing of signals from the z strip to the end of the detector modules is done with a second metal layer on the detector surface, thus keeping the material in the sensitive area to a minimum. P airs of wafers are daisy chained, with the wafers within each pair ipped with respect to each other in order to minimize the load capacitance on the readout ampliers. The design of the detector and its various components are described. Results on the performance of the new detector are presented, with special emphasis on alignment, intrinsic precision and impact parameter resolution. The new detector has been taking data since spring of 1994, performing up to design specications.

Charge collection efficiency and resolution of an irradiated double-sided silicon microstrip detector operated at cryogenic temperatures

“…The DELPHI module used was a rejected half module of the 1994 DELPHI [3] vertex detector, described in detail in [4]. The module is illustrated schematically in figure 1.…”

The DELPHI Silicon Tracker at LEP2

“…Vertexing in the barrel region The central part of the Silicon Tracker must have a b -tagging performance which i s at least equivalent to that of the 1994-95 Vertex Detector [2], and in addition be extended down to around 25 , b e y ond which m ultiple scattering starts to dominate the impact parameter resolution for b hadron decay products. This is achieved with three layers of microstrip modules, termed Closer, Inner and Outer, at average radii of 6.6 cm, 9.2 cm and 10.6 cm.…”

“…To make the project a ordable components and systems were re-used from the previous silicon vertex detectors of DELPHI, namely some of the plaquettes and hybrids [2] and the data acquisition and service systems [4]. The complete Barrel and a large part of the VFT (the full set of ministrip detectors and 60% of the pixels) was in operation during the 1996 data taking.…”

“…In order to minimise the amount of material the Closer layer is composed of double-sided detectors. This layer is taken from the 1994-95 Vertex Detector [2]. For the Outer layer, where multiple scattering is less crucial, a cheaper back-to-back solution was chosen.…”

“…The Inner layer is built up of both double and single-sided detectors, allowing the re-use of double-sided detectors from the previous vertex detector. 2 Hamamatsu Photonics K.K., Hamamatsu City, Japan 3 The pixel plaquettes are divided into ten regions of 24 24 pixels at large radius and six regions of 24 16 pixels at smaller radius. Each region is read out by an SP8 [10] chip bump-bonded to the detector (see section 4).…”