Tracker Modules Research Articles

Embedded pitch adapters for the ATLAS Tracker Upgrade

In the current ATLAS tracker modules, sensor bonding pads are placed on their corresponding strips and oriented along the strips. This creates a difference in pitch and orientation between sensor bond pads and readout electronics bond pads. Therefore, a pitch adapter (PA), or “fan-in”, is needed. The purpose of these PA is the electrical interconnection of every channel from the detector bonding pads to the read-out chips, adapting the different pad pitch. Our new approach is to build those PAs inside the sensor; this is what we call Embedded Pitch Adapters. The idea is to use an additional metal layer in order to define a new group of pads, connected to the strips via tracks with the second metal. The embedded PAs have been fabricated on 4-in. prototype sensors for the ATLAS-Upgrade Endcap Tracker to test their performance and suitability. The tests confirm proper fabrication of the second metal tracks, and no effects on detector performance. No indication of cross-talk between first and second metal channels has been observed. A small indication of possible signal pick-up from the bulk has been observed in a few channels, which needs to be further investigated.

Hybrid circuits for the CMS tracker upgrade frontend electronics

The upgrade of the CMS tracker at the HL-LHC requires the design of new front-end modules to cope with the increased luminosity and to implement L1 trigger functionality. The new modules under development are based on high density hybrid circuits with new flip-chip front-end ASIC, and are wire bonded to strip sensors and connected to a service board for the data transmission. The suitability of different substrate technologies considered for the design of the hybrids is discussed, aiming for a cost effective and reliable manufacturability of the CMS tracker modules.

Full-scale prototype of the circular track detector for the multipurpose detector facility at the NICA acceleration complex

The development of the NICA heavy ion collider, which is now under way, assumes the development of a Multipurpose Detector (MPD), including an end-cap tracker (EC) (which can be a wheel-type tracker based on thin-wall drift tubes (straws) similar to the inner detector of the transition radiation tracker (TRT) in the ATLAS experiment). The identical front and back tracker modules mounted behind the TPC are to ensure the detection of Au-Au ion collision products in the pseudorapidity range from 1.4 to 2.1 with good track parameters of reconstructed events. Each module will contain 60 circular straw planes and maximum straw occupancy will be no higher than 0.2 particle per collision. The NICA EC is substantially different from its analogue and requires a certain amount of R&D. The first results from applying new technology to make a full-scale prototype of the circular EC detector for NICA are presented.

DC-DC converters with reduced mass for trackers at the HL-LHC

The development at CERN of low noise DC-DC converters for the powering of front-end systems enables the implementation of efficient powering schemes for the physics experiments at the HL-LHC. Recent tests made on the ATLAS short strip tracker modules confirm the full electromagnetic compatibility of the DC-DC converter prototypes with front-end detectors. The integration of the converters in the trackers front-ends needs to address also the material budget constraints. The impact of the DC-DC converters onto the material budget of the ATLAS tracker modules is discussed and mass reduction techniques are explored, leading to a compromise between electromagnetic compatibility and mass. Low mass shield implementations and Aluminum core inductors are proposed. Also, the impact on emitted noise due to a size reduction of critical components is discussed. Finally, material reduction techniques are discussed at the board layout and manufacturing levels.

Development of a Miniaturized Multisensory Positioning Device for Laser Dicing Technology

In this study we propose a multisensory laser tracker system for measuring and tracking the TCP (Tool Center Point) of e.g. high precision motion systems. An experimental platform composed of four tracker modules is developed in order to track the TCP of a linear positioning system based upon the length measurement (multi-lateration). Concepts and first devices for miniaturization of the tracker system are presented.

The development of a high-resolution scintillating fiber tracker with silicon photomultiplier readout

We present test results from a novel modular scintillating fiber tracker using silicon photomultiplier (SiPM) arrays for readout. The tracker modules are made up from 250 μ m thin scintillating fibers that are arranged in five tightly packed layers on top and on bottom of a light carbon fiber/Rohacell foam support structure. Novel, custom made SiPM arrays from Hamamatsu with a channel pitch of 250 μ m and a photon detection efficiency of approximately 50% are used for readout. From a full GEANT4 simulation the expected position resolution is 0.05 mm at a tracking efficiency of 99%. Several 860 mm long and 32–64 mm wide tracker modules were tested at the PS facilities at CERN in summer 2008 and autumn 2009 achieving high light yields of about 20 photons for a minimal ionizing particle. We will show details on the characterization of the SiPM arrays and the quality control of scintillating fibers, the construction of the fiber modules and the results in terms of tracking efficiency, noise and position resolution.

Conceptual study of a trigger module for the CMS Tracker at SLHC

The CMS experiment is planning a major upgrade of its tracking system to adapt to an expected increase in luminosity of the LHC accelerator to 10 35 cm −2 s −1. It will then have to cope with several hundred interactions per bunch crossing and fluxes of thousands of charged particles emerging from collisions. CMS requires tracker data to contribute to the first level trigger, to maintain the present 100 kHz rate while increasing the trigger decision latency by only a few μs. It must be achieved without compromising the tracking performance which is very sensitive to the material budget. A key part of a system to achieve this will be the design of a suitable module to generate trigger primitives. One possible solution is based on the so-called “stacked tracker modules” using closely spaced, coarsely pixilated sensor layers situated at intermediate radius within the tracker volume. The pattern of hits in each layer is compared to identify high p T track candidates. Simulations have been carried out which support the basic concept. A basic readout architecture is proposed and some of the electronic implications are described. Estimates of likely power consumption are given, as well as data rates and link bandwidth requirements.

Modeling the performance of low concentration photovoltaic systems

A theoretical model has been developed to describe the response of V-trough systems in terms of module temperature, power output and energy yield using as inputs the atmospheric conditions. The model was adjusted to DoubleSun ® concentration technology, which integrates dual-axis tracker and conventional mono-crystalline Si modules. The good agreement between model predictions and the results obtained at WS Energia laboratory, Portugal, validated the model. It is shown that DoubleSun ® technology increases up to 86% the yearly energy yield of conventional modules relative to a fixed flat-plate system. The model was also used to perform a sensitivity analysis, in order to highlight the relevance of the leading working parameters (such as irradiance) in system performance (energy yield and module temperature). Model results show that the operation module temperature is always below the maximum working temperature defined by the module manufacturers.

Performance studies of the CMS Strip Tracker before installation

In March 2007 the assembly of the Silicon Strip Tracker was completed at the Tracker Integration Facility at CERN. Nearly 15% of the detector was instrumented using cables, fiber optics, power supplies, and electronics intended for the operation at the LHC. A local chiller was used to circulate the coolant for low temperature operation. In order to understand the efficiency and alignment of the strip tracker modules, a cosmic ray trigger was implemented. From March through July 4.5 million triggers were recorded. This period, referred to as the Sector Test, provided practical experience with the operation of the Tracker, especially safety, data acquisition, power, and cooling systems. This paper describes the performance of the strip system during the Sector Test, which consisted of five distinct periods defined by the coolant temperature. Significant emphasis is placed on comparisons between the data and results from Monte Carlo studies.

ATLAS Experiment Silicon Inner Detector Alignment

The ATLAS experiment at CERN is preparing for Large Hadron Collider data at the end of 2007. ATLAS Inner Detector track reconstruction uses drift tube and silicon based subdetectors. ATLAS physics goals require positions of the silicon tracker modules to a precision better than 10 μ m. Planned alignment of the silicon tracker combines a hardware system and track based algorithms. The silicon detector has 5832 modules with a corresponding 34992 degrees of freedom, requiring non-trivial alignment strategies to obtain the desired precision and novel software and hardware techniques. Silicon tracker alignment algorithms and their functionalities are described and initial results from a combined test beam setup and combined cosmic ray data taking are presented.

Signal-to-noise measurements on irradiated CMS tracker detector modules in an electron testbeam

The CMS experiment at the Large Hadron Collider at CERN is in the last phase of its construction. The harsh radiation environment at LHC will put strong demands in radiation hardness to the innermost parts of the detector. To assess the performance of irradiated silicon microstrip detector modules, a testbeam was conducted at the Testbeam 22 facility of the DESY research center. The primary objective was the signal-to-noise measurement of fully irradiated CMS Tracker modules to ensure their functionality up to 10 years of LHC operation. The paper briefly summarises the basic setup at the facility and the hardware and software used to collect and analyse the data. Some interesting subsidiary results are shown, which confirm the expected behaviour of the detector with respect to the signal-to-noise performance over the active detector area and for different electron energies. The main focus of the paper are the results of the signal-to-noise over reverse bias voltage measurements for CMS Tracker Modules which were exposed to different radiation doses.

The laser alignment system for the CMS silicon microstrip tracker

In the CMS Microstrip Tracker the algorithms that are used for the online track reconstruction, require the alignment of the tracker modules on a level of better than 100 μ m . A Laser Alignment System has been developed that is able to detect possible movements or deformations of the Tracker mechanical structure with this level of precision. This system works with infrared laser beams which are detected by the silicon microstrip sensors, allowing to monitor movements of a subset of the tracker modules with respect to each other. In this article an overview of the Laser Alignment System is given, and first measurements with the integrated system are presented. The system has been shown to work properly and it confirms the expected mounting precision of the sensor modules in the detector endcaps. During cooling cycles no significant deformation of the endcap structure was observed.

Serial powering of silicon strip detectors at SLHC

Serial powering is a technique to power a large numbers of detector modules using a single power cable and a constant current source. Module power is derived using local shunt regulators. Serial powering is of great interest for large-scale silicon tracking detectors for particle physics with many thousands of densely packed detector modules. We have been operating six ATLAS Semiconductor Tracker (SCT) modules using both serial powering and conventional independent powering. The modules operated stably with no indication of any extra noise sources. We present selected results and discuss the system aspects of serial powering.

Readout electronics testing of the CMS Tracker modules with LT setup

The tracking part of the CMS detector will be built with ∼16000 silicon detector modules, and kept at −10°C for the ten years of the operation of the LHC. All the model materials need to be verified of having a good performance at this low temperature, before their installation into the CMS Tracker. In order to track performance quality, assurance tests are done with two different systems. Of the two setups used, the LT system module is the one that is used to identify whether the performance of readout electronics and leakage current flowing on the silicon sensors is affected by low temperature. In this paper a detailed layout of the CMS TOB modules and their front-end hybrids are presented. In addition, the LT testing results of the 190 TOB modules that were produced and tested in 2004 by the FNAL-CMS group are given.

Enhanced tracking and recognition of moving objects by reasoning about spatio-temporal continuity

A framework for the logical and statistical analysis and annotation of dynamic scenes containing occlusion and other uncertainties is presented. This framework consists of three elements; an object tracker module, an object recognition/classification module and a logical consistency, ambiguity and error reasoning engine. The principle behind the object tracker and object recognition modules is to reduce error by increasing ambiguity (by merging objects in close proximity and presenting multiple hypotheses). The reasoning engine deals with error, ambiguity and occlusion in a unified framework to produce a hypothesis that satisfies fundamental constraints on the spatio-temporal continuity of objects. Our algorithm finds a globally consistent model of an extended video sequence that is maximally supported by a voting function based on the output of a statistical classifier. The system results in an annotation that is significantly more accurate than what would be obtained by by-frame evaluation of the classifier output. The framework has been implemented and applied successfully to the analysis of team sports with a single camera.

Induced radioactivity in the forward shielding and semiconductor tracker of the ATLAS detector

The radioactivity induced in the forward shielding, copper collimator and semiconductor tracker modules of the ATLAS detector has been studied. The ATLAS detector is a long-term experiment which, during operation, will require to have service and access to all of its parts and components. The radioactivity induced in the forward shielding was calculated by Monte Carlo methods based on GEANT3 software tool. The results show that the equivalent dose rates on the outer surface of the forward shielding are very low (at most 0.038 microSv h(-1)). On the other hand, the equivalent dose rates are significantly higher on the inner surface of the forward shielding (up to 661 microSv h(-1)) and, especially, at the copper collimator close to the beampipe (up to 60 mSv h(-1)). The radioactivity induced in the semiconductor tracker modules was studied experimentally. The module was activated by neutrons in a training nuclear reactor and the delayed gamma ray spectra were measured. From these measurements, the equivalent dose rate on the surface of the semiconductor tracker module was estimated to be < 100 microSv h(-1) after 100 d of Large Hadron Collider (LHC) operation and 10 d of cooling.

Beam-loss-induced electrical stress test on CMS Silicon Strip Modules

Based on simulated LHC beam loss scenarios, fully depleted CMS silicon tracker modules and sensors were exposed to 42 ns -long beam spills of approximately 10 11 protons per spill at the PS at CERN. The ionisation dose was sufficient to short circuit the silicon sensors. The dynamic behaviour of bias voltage, leakage currents and voltages over coupling capacitors were monitored during the impact. Results of pre- and post-qualification as well as the dynamic behaviour are shown.

Radioactivation of silicon tracker modules in high-luminosity hadron collider radiation environments

One of the consequences of operating detector systems in harsh radiation environments will be radioactivation of the components. This will certainly be true in experiments such as ATLAS and CMS, which are currently being built to exploit the physics potential at CERN's Large Hadron Collider. If the levels of radioactivity and corresponding dose rates are significant, then there will be implications for any access or maintenance operations. This paper presents predictions for the radioactivation of ATLAS's Semi-Conductor Tracker (SCT) barrel system, based on both calculations and measurements. It is shown that both neutron capture and high-energy hadron reactions must be taken into account. The predictions also show that the SCT barrel-module should not pose any serious radiological problems after operation in high radiation environments.

Design optimisation of silicon microstrip detector modules for operation in high radiation levels at the LHC

The Large Hadron Collider (LHC) operation conditions amount to considerable challenges in track and vertex detector design, which is driven by many conflicting requirements. The high luminosity, 10 34 cm −2 s −1, planned for the 10 years of LHC operation are at the expenses of a particle interaction rate of ∼10 9 Hz and, hence, high total hadron radiation fluences, about 2×10 14 n eq/cm 2. Such a luminosity is achieved using a bunch–bunch crossing frequency of 40 MHz that will require very fast and low noise signal processing, in order to separate signals from different bunch crossings, very long on-detector buffers to keep the data during the trigger latency together with fast and reliable data links for the off-detector data transmission. Since radiation effects are strongly temperature dependent, the thermal properties of the devices will drive severely the design options. This, together with the stringent requirements set by the expected performance of the LHC trackers translates into constraints on the mechanical precision and stability. Last but not least, access for maintenance and repair will be very restricted and, since radiation damage is severe, redundancy is another key point in the design. This paper describes the design options chosen for the ATLAS Semiconductor Tracker (SCT) modules and will show results on their performance.

A Technique for Testing the Si Tracker Modules for the D0 Collider Experiment (FNAL) and Comparative Analysis of the Test Results

The Skobel'tsyn Institute of Nuclear Physics (SINP) of Moscow State University participates in the development of a silicon tracker for the D0 experiment (FNAL, USA). The SINP specialists were engaged in assembling and testing of the end-disc detectors for the tracker. A technique for testing the disc modules is described, and the test results are presented. They are compared to the disc-detector parameters and measured before the assembling. This comparison can be used to create test procedures and the detector-selection criteria in the development of large-sized tracking systems on the basis of single-sided microstrip detectors.