The optical links of the ATLAS SemiConductor tracker

Optical links are used for the readout of the 4088 silicon microstrip modules that make up the SemiConductor Tracker of the ATLAS experiment at the CERN Large Hadron Collider (LHC). The optical link requirements are reviewed, with particular emphasis on the very demanding environment at the LHC. The on-detector components have to operate in high radiation levels for 10 years, with no maintenance, and there are very strict requirements on power consumption, material and space. A novel concept for the packaging of the on-detector optoelectronics has been developed to meet these requirements. The system architecture, including its redundancy features, is explained and the critical on-detector components are described. The results of the extensive Quality Assurance performed during all steps of the assembly are discussed

The ATLAS SCT Optoelectronics and the Associated Electrical Services

The requirements for the optical links of the ATLAS SCT are described. From the individual detector modules to the first patch panel, the electrical services are integrated with the optical links to aid in mechanical design, construction and integration. The system architecture and critical elements of the system are described. The optical links for the ATLAS SCT have been assembled and mounted onto the carbon fibre support structures. The performance of the system as measured during QA is summarised and compared to the final performance obtained after mounting modules onto the support structures

Reliability of Various Size Oxide Aperture VCSELs,"

Abstract This paper presents Honeywell's most recent work on 850-nm oxide aperture vertical cavity surface emitting laser (VCSEL) reliability. The VCSELs studied have a range of aperture diameters from about 5 to 20 µm and the reliability effect of aperture diameter is of principal interest in this paper. Larger apertures generally exhibit greater reliability. Electrostatic discharge (ESD) sensitivity thresholds of the various oxide aperture VCSELs is discussed, again showing dependence on diameter, with larger being better. Results for humidity exposure are presented. Here we find no aperture size dependence, because none of the tested designs show significant susceptibility to humidity-induced degradation. It is demonstrated that, in addition to end-of-life degradation, VCSELs generally exhibit variation of performance characteristics during the early part of operating life. This often leads to a requirement for device burn-in. Honeywell's work in the area of wafer stabilization (trademarked under the name STABILAZE, patent pending) is introduced, showing how critical device parameters such as threshold and slope efficiency can be made to be unvarying over the product's life without the need for costly component or module-level burnins

Radiation effects in optical link components for future particle physics detectors

Optical link components used in future particle physics experiments will typically be exposed to intense radiation fields during the lifetime of the experiment and the qualification of these components in terms of radiation tolerance is thus required. Data on semiconductor lasers and photodiodes for use in 10 Gb/s datalinks tested during high-fluence (in excess of 10[to the power of 15] particles/cm2) neutron and pion irradiation in 2009 and 2010 are presented with annealing data. In order to predict the behaviour of a laser irradiated with the different particle fluxes at different locations inside a particle physics experiment, radiation damage in lasers has been modelled. The model describes the degradation of the L-I characteristic of a semiconductor laser undergoing irradiation with the annealing processes taken into account. The robustness of the model has been checked against the experimental data. Additionally, the author’s method to estimate Single Event Upsets in photodetectors using GEANT4 is presented. Use of optoelectronic devices in digital data transmission systems in HEP detectors is also discussed.Open Acces

Characterisation of on-chip electrostatic discharge waveforms with sub-nanosecond resolution: design of a differential high voltage probe with high bandwidth

Bliksem werd tot aan de ontdekking van de bliksemafleider (18e eeuw) gezien als een van de gevaarlijkste bedreigingen voor het stadsleven. Door het gebruik van micro-elektronica werden ingenieurs gewaar dat ditzelfde fysische verschijnsel, elektrostatische ontlading of ESD genoemd, zich ook op microscopische schaal voordoet. In de jaren zeventig was meer dan 30% van al het chipfalen te wijten aan ESD. Om dit tegen te gaan werd met het onderzoek naar ESD-protecties en -meetsystemen aangevangen. Om meer informatie over het gedrag van een ESD-protectie te verkrijgen wordt een ESD-puls op dit systeem losgelaten. Het antwoord van de protectie op deze puls wordt dan bepaald m.b.v. spannings- en stroomgolfvormmetingen. In dit werk wordt een nieuwe nauwkeurige ESD-golfvormmeettechniek voorgesteld die directe metingen op protecties kan uitvoeren. De karakterisering van ESD-golfvormen op chip wordt enorm bemoeilijkt door de grote hoeveelheid elektromagnetische interferentie die de ESD-puls veroorzaakt. Dit wordt omzeild door het gewenste signaal naar een veilige omgeving te transporteren, waar een standaard meettoestel de meting kan uitvoeren. Dit transport wordt gerealiseerd m.b.v. optische communicatie, wat immuun is voor elektromagnetische interferentie. Zo kan nauwkeurige in-situ-informatie worden verkregen waarmee de ESD-protecties in de toekomst verbeterd kunnen worden.Up to the 18th century, lightning was considered one of nature’s most dangerous threats in city life. This all ended with the lightning rod, protecting thousands of homes during lightning storms. The large-scale use of microelectronics has made engineers aware of the same physical phenomenon occuring on a microscopic scale. This phenomenon is called electrostatic discharge or ESD. In the seventies, more than 30% of all chip failure was attributed to static electricity. To counter this effect, the research for on-chip ESD protections was born. Today ESD is a buzzing line of research, as with new and faster chip technologies comes a higher ESD vulnerability. This makes ESD protection and measurement increasingly important. Although ESD is now a major subject in chip design, it copes with a lack of accurate device models. To gain more information on the exact operation of an ESD protection, an ESD pulse is unleashed upon this device. The response of the protection on this pulse is then assessed by performing voltage or current waveform measurements. This work presents a waveform measurement technique able to accurately perform direct measurements on the ESD protection. Due to the high amount of electromagnetic interference caused by the ESD pulse, direct waveform characterisation near the protection is hard. This is solved by transporting the target signal into a clean area, where the measurement is performed by standard lab equipment. The key is that this transportation is realized by means of optical communication, which is immune to electromagnetic interference. This way, accurate in situ information can be used to protect tomorrow’s chips

High Frequency Open Air Optical Communication System

The goal of this project is to create a wireless optical communication system that operates at high frequencies (up to 3 GHz). The system will function by taking a digital electric input signal, converting it to a photonic signal, recovering the signal at the other end of a short distance (~1 foot) and converting it back into a digital signal. Unlike the more common fiber-optic data transmission systems, this system will transmit light through air, instead of fiber, as its medium. Doing so will have the benefits of a wireless system combined with the benefits from an optical system, including voltage isolation, no interference from electromagnetic waves, and no cross talk from other electrical signals. Research for this project will consist of how to optimize an optical isolator system for high frequencies. This includes determining optimal wavelength of the light to be transmitted, the power necessary to successfully transmit the signal, and LED’s and photo-detectors that are well suited for these requirements. Also, since these systems are useful in industry, cost of materials and production are important factors, and will be taken into consideration when selecting components

Results from the Commissioning of the ATLAS Pixel Detector

The ATLAS pixel detector is the innermost tracking detector of the ATLAS experiment at the Large Hadron Collider (LHC) at CERN. It has a total active area of 1.7 m2 of silicon read out by approximately 80 million electronic channels, which will detect particle tracks and decay vertices with a very high precision. After more than 10 years of development and construction it is the first time ever the whole detector has been operated together. The paper will illustrate the detector performance and give first results from the combined ATLAS cosmics runs

Thermomechanical issues of high power laser diode catastrophic optical damage

Catastrophic optical damage (COD) of high power laser diodes is a crucial factor limiting ultra high power lasers. The understanding of the COD process is essential to improve the endurance of the high power laser diodes. COD is observed as a process in which the active part of the laser diode is destroyed, forming characteristic defects, the so called dark line defects (DLDs). The DLDs are formed by arrays of dislocations generated during the laser operation. Local heating associated with non-radiative recombination is assumed to be at the origin of the COD process. A summary of the methods used to assess the COD, both in real time and post-mortem is presented. The main approaches developed in recent years to model the heat transport in the laser structures under non homogeneous temperature distribution are overviewed. Special emphasis is paid to the impact of the low dimensionality of QWs in two physical properties playing a major role in the COD process, namely, thermal conductivity and mechanical strength. A discussion about the impact of the nanoscale in both physical properties is presented. Finally, we summarize the main issues of the thermomechanical modelling of COD. Within this model the COD is launched when the local thermal stresses generated around the heat source overcome the yield stress of the active zone of the laser. The thermal runaway is related to the sharp decrease of the thermal conductivity once the onset of plasticity has been reached in the active zone of the laser.Junta de Castilla y León (Projects VA081U16 and VA283P18)Spanish Government (ENE 2014-56069-C4-4-R, ENE 2017-89561-C4-3-R, FPU programme 14/00916)