Alternative glues for the production of ATLAS silicon strip modules for the Phase-II upgrade of the ATLAS Inner Detector

The Phase-II upgrade of the ATLAS detector for the High Luminosity Large Hadron Collider (HL-LHC) includes the replacement of the current Inner Detector with an all-silicon tracker consisting of pixel and strip detectors. The current Phase-II detector layout requires the construction of 20,000 strip detector modules consisting of sensor, circuit boards and readout chips, which are connected mechanically using adhesives. The adhesive between readout chips and circuit board is a silver epoxy glue as was used in the current ATLAS SemiConductor Tracker (SCT). This glue has several disadvantages, which motivated the search for an alternative. This paper presents a study concerning the use of six ultra-violet (UV) cure glues and a glue pad for use in the assembly of silicon strip detector modules for the ATLAS upgrade. Trials were carried out to determine the ease of use, the thermal conduction and shear strength, thermal cycling, radiation hardness, corrosion resistance and shear strength tests. These investigations led to the exclusion of three UV cure glues as well as the glue pad. Three UV cure glues were found to be possible better alternatives. Results from electrical tests of first prototype modules constructed using these glues are presented.Comment: 23 pages, to be published in Journal of Instrumentatio

Flexible Bond Wire Capacitive Strain Sensor for Vehicle Tyres

The safety of the driving experience and manoeuvrability of a vehicle can be improved by detecting the strain in tyres. To measure strain accurately in rubber, the strain sensor needs to be flexible so that it does not deform the medium that it is measuring. In this work, a novel flexible bond wire capacitive strain sensor for measuring the strain in tyres is developed, fabricated and calibrated. An array of 25 micron diameter wire bonds in an approximately 8 mm × 8 mm area is built to create an interdigitated structure, which consists of 50 wire loops resulting in 49 capacitor pairs in parallel. Laser machining was used to pattern copper on a flexible printed circuit board PCB to make the bond pads for the wire attachment. The wire array was finally packaged and embedded in polydimethylsiloxane (PDMS), which acts as the structural material that is strained. The capacitance of the device is in a linear like relationship with respect to the strain, which can measure the strain up to at least ±60,000 micro-strain (±6%) with a resolution of ~132 micro-strain (0.013%). In-tyre testing under static loading has shown the ability of the sensor to measure large tyre strains. The technology used for sensor fabrication lends itself to mass production and so the design is considered to be consistent with low cost commercialisable strain sensing technology

The ABC130 barrel module prototyping programme for the ATLAS strip tracker

For the Phase-II Upgrade of the ATLAS Detector, its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100 % silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-25) and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests.Comment: 82 pages, 66 figure

Colossal thermal expansion and negative thermal expansion in simple halogen bonded complexes

The crystal structures of the simple monoclinic halogen-bonded complexes pyridine-ICl and pyridine-IBr have been redetermined using modern X-ray and neutron diffraction techniques. The representation quadric surfaces for the thermal expansion tensor have been found to consist of a hyperboloid of one sheet. Negative thermal expansion occurs parallel to the crystallographic b axis, whilst there is colossal thermal expansion in a direction approximately parallel to the a* direction. These effects arise because of a decrease in the strength of an already weak C-H ··· X (X = Br, Cl) hydrogen bond with increasing temperature. The decrease in strength of the hydrogen bonding originates because of the reduction in the strength of the halogen bond formed between the nitrogen atom and the IX moiety with increasing temperature. Thus since at 298 K the I-X bonds are shorter than at 110 K, there will be a smaller partial negative charge on the X halogen at 298 K, leading to a weaker C-H ··· X hydrogen bond

Colossal thermal expansion and negative thermal expansion in simple halogen bonded complexes

The crystal structures of the simple monoclinic halogen-bonded complexes pyridine–ICl and pyridine–IBr have been redetermined using modern X-ray and neutron diffraction techniques. The representation quadric surfaces for the thermal expansion tensor have been found to consist of a hyperboloid of one sheet. Negative thermal expansion occurs parallel to the crystallographic b axis, whilst there is colossal thermal expansion in a direction approximately parallel to the a* direction. These effects arise because of a decrease in the strength of an already weak C–H⋯X (X = Br, Cl) hydrogen bond with increasing temperature. The decrease in strength of the hydrogen bonding originates because of the reduction in the strength of the halogen bond formed between the nitrogen atom and the IX moiety with increasing temperature. Thus since at 298 K the I–X bonds are shorter than at 110 K, there will be a smaller partial negative charge on the X halogen at 298 K, leading to a weaker C–H⋯X hydrogen bond

ESTIMATING THE INEQUALITY OF HOUSEHOLD INCOMES: A STATISTICAL APPROACH TO THE CREATION OF A DENSE AND CONSISTENT GLOBAL DATA SET

The deficiencies of the Deininger and Squire data set on household income inequality are well known to include sparse coverage, problematic measurements, and the combination of diverse data types into a single data set. Yet many studies have relied on this data due to the lack of available alternatives. In this paper we show how the UTIP-UNIDO measures of manufacturing pay inequality can be used, with other information, to estimate measures of household income inequality. We take advantage of the systematic relationship between the UTIP-UNIDO estimates and those of Deininger and Squire. The residuals from this exercise provide a map to problematic observations in the Deininger and Squire data, and the estimated coefficients provide a way to construct a new panel data set of estimated household income inequality. This new data set provides comparable and consistent measurements across space and through time. Copyright 2005 Blackwell Publishing Ltd.

Comparison of one- And two-dimensional dielectric reflector geometries for high-energy laser pulse compression

The NA62 experiment at CERN aims to make a precision measurement of the ultra-rare decay $K^{+} \rightarrow \pi^{+}\nu\overline{\nu}$, and relies on a differential Cherenkov detector (KTAG) to identify charged kaons at an average rate of 50 MHz in a 750 MHz unseparated hadron beam. The experimental sensitivity of NA62 to K-decay branching ratios (BR) of $10^{-11}$ requires a time resolution for the KTAG of better than 100 ps, an efficiency better than 95% and a contamination of the kaon sample that is smaller than $10^{-4}$. A prototype version of the detector was tested in 2012, during the first NA62 technical run, in which the required resolution of 100 ps was achieved and the necessary functionality of the light collection system and electronics was demonstrated

Strip sensor performance in prototype modules built for ATLAS ITk

The ATLAS Phase-II Upgrade for the High-Luminosity LHC features replacement of the Inner Detector with an all-silicon Inner Tracker (ITk). The majority of the instrumented area in ITk is occupied by strip modules covering 165 m2. A vigorous R&D program has been on-going for many years to prepare for the scale of the project and to work out technical issues at all key components of the system, including the strip sensors, readout ASICs, hybrids, modules, and staves. In this submission we report on the performance of silicon strip sensors used in the last completed round of module prototyping. Over 80 modules were built and tested with electrical readout on the per-channel basis and the sensor performance was assessed. In general, an excellent performance was observed, consistent with previous ASIC-level and sensor-level tests. However, the lessons learned included two phenomena important for the future phases of the project. First was the need to store and test the modules in a dry environment due to humidity sensitivity of the sensors. The second was a rare observation of high noise on some channels, at the rate of about 3%. The high noise regions were tested further in several ways, including monitoring the performance as a function of time and bias voltage. Additionally, direct sensor-level tests were performed on the affected channels. The inter-strip resistance and bias resistance tests showed low values, indicating a temporary loss of the inter-strip isolation. A subsequent recovery of the noise performance was observed. We present the test details, an analysis of how the inter-strip isolation affects the module noise, and relationship with sensor-level quality control tests