The ATLAS detector (CERN/LHCC/94-43 (1994)) is designed to study a wide range of physics at the CERN Large Hadron Collider (LHC) at luminosities up to 1034 cm−2 s−1 with a bunch-crossing rate of 40 MHz. The Semiconductor Tracker (SCT) forms a key component of the Inner Detector (vol. 1, ATLAS TDR 4, CERN/LHCC 97–16 (1997); vol. 2, ATLAS TDR 5, CERN/LHCC 97-17 (1997)) which is situated inside a 2 T solenoid field. The ATLAS Semiconductor Tracker (SCT) utilises 4088 silicon modules with binary readout mounted on carbon fibre composite structures arranged in the forms of barrels in the central region and discs in the forward region. The construction of the SCT is now well advanced. The design of the SCT modules, services and support structures will be briefly outlined. A description of the various stages in the construction process will be presented with examples of the performance achieved and the main difficulties encountered. Finally, the current status of the construction is reviewed.

The ATLAS semiconductor tracker (SCT)

As a part of the quality assurance procedure of the ATLAS SCT (Semiconductor Tracker) barrel modules, the response of the microstrip detector is measured by injecting focused Nd:YAG laser at each strip. The test is sensitive to sensor originated problems and a cross check to the results obtained from the electrical tests performed with the test pulse system implemented in the readout ASICs. Combining these results with the probing results obtained by the silicon sensor manufacturer, we verified the reliabilities of these tests and classified the type of defects for overall performance evaluation of the modules.

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Test of ATLAS SCT barrel modules with Nd:YAG laser

PANDA is the multi-purpose detector that is under construction to cover most of the measurements using antiprotons from the high-energy storage ring (HESR), which will become possible at the GSI future facility. The detector setup has to meet the requirements of a broad physics programme, which ranges from high-resolution resonance spectroscopy in the charmonium region to the production of open charm in annihilations of antiprotons on heavy nuclei. The interaction rate of up to 107 annihilations/s requires sophisticated trigger concepts, which are in part based on vertex detection. To this end, PANDA will be equipped with a compact state-of-the-art micro-vertex detector. Its data shall be used for D meson identification at data acquisition time. Layout of the vertex detector and its interaction with the other detector parts are discussed and an introduction into the physics programme is given.

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PANDA at the GSI future facility

Among the 981 silicon microstrip modules fabricated by the ATLAS SCT Japan group, 111 modules showed a micro-discharge, a rapid leakage current increase when the bias is raised, below 500 V bias at least once in the series of the quality assurance testing. We have conducted a systematic study to understand the causes, including the hot spot localization using an infrared sensitive camera, and measurement of leakage current decay time.

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Systematic study of micro-discharge characteristics of ATLAS barrel silicon microstrip modules

With signal to noise ratio ( S / N ) being a key parameter of a high performance detector, reducing the detector noise has been one of the main tasks in detector development. A new low capacitance silicon pixel detector is proposed, which is based on a new electrode geometry with reduced effective electrode area while keeping the sensitive volume unchanged. Detector electrical characteristics including electrostatic potential, electric field, full depletion voltage, and capacitance have been simulated in detail using a 3D TCAD tool. From these simulations and calculations, we confirm that the new detector structure has a much reduced capacitance (by a factor of 3) as compared to the traditional pixel detectors with the same sensitive volume. This reduction in detector capacitance can certainly improve the detector signal to noise ratio. However, the full depletion voltage for the new structure is larger than that of the traditional one due to the small electrode effect.

3D simulations and modeling of new low capacitance silicon pixel detectors

We have developed a semi-automated assembly system and constructed 124 silicon microstrip modules so far for the ATLAS SCT barrel. This article describes the assembly procedure, evaluations of precisions and the module survey results. A precision of ∼2 μm is achievable with this assembly system.

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T Miyamoto

Papers

Construction of the ATLAS semi-conductor tracker (SCT) barrel modules in Japan