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

Characterization of a CdZnTe detector for a low-power CubeSat application

We report spectral and imaging performance of a pixelated CdZnTe detector custom designed for the MeVCube project: a small Compton telescope on a CubeSat platform. MeVCube is expected to cover the energy range between 200 keV and 4 MeV, with a sensitivity comparable to the one of the last generation of larger satellites. In order to achieve this goal, an energy resolution of few percent in full width at half maximum (FWHM) and a 3-D spatial resolution of few millimeters for the individual detectors are needed. The severe power constraints present in small satellites require very low power read-out electronics for the detector. Our read-out is based on the VATA450.3 ASIC developed by Ideas, with a power consumption of only 0.25 mW/channel, which exhibits good performance in terms of dynamic range, noise and linearity. A 2.0 cm× 2.0 cm× 1.5 cm CdZnTe detector, with a custom 8 × 8 pixel anode structure read-out by a VATA450.3 ASIC, has been tested. A preliminary read-out system for the cathode, based on a discrete Amptek A250F charge sensitive pre-amplifier and a DRS4 ASIC, has been implemented. An energy resolution around 3% FWHM has been measured at a gamma energy of 662 keV; at 200 keV the average energy resolution is 6.5%, decreasing to ≲ 2% at energies above 1 MeV. A 3-D spatial resolution of ≈ 2 mm is achieved in each dimension.Peer Reviewe

Characterization of a CdZnTe detector for a low-power CubeSat application

We report spectral and imaging performance of a pixelated CdZnTe detector custom designed for the \emph{MeVCube} project: a small Compton telescope on a CubeSat platform. \emph{MeVCube} is expected to cover the energy range between $200\;\mathrm{keV}$ and $4\;\mathrm{MeV}$, with performance comparable to the last generation of larger satellites. In order to achieve this goal, an energy resolution of few percent in full width at half maximum (FWHM) and a $3$-D spatial resolution of few millimeters for the individual detectors are needed. The severe power constraints present in small satellites require very low power read-out electronics for the detector. Our read-out is based on the VATA450.3 ASIC developed by \emph{Ideas}, with a power consumption of only $0.25\;\mathrm{mW/channel}$, which exhibits good performance in terms of dynamic range, noise and linearity. A $2.0\;\mathrm{cm} \times 2.0\;\mathrm{cm} \times 1.5\;\mathrm{cm}$ CdZnTe detector, with a custom $8 \times 8$ pixel anode structure read-out by a VATA450.3 ASIC, has been tested. A preliminary read-out system for the cathode, based on a discrete \emph{Amptek} A250F charge sensitive pre-amplifier and a DRS4 ASIC, has been implemented. An energy resolution around $3\%$ FWHM has been measured at a gamma energy of $662\;\mathrm{keV}$; at $200\;\mathrm{keV}$ the average energy resolution is $6.5\%$, decreasing to $\lesssim 2\%$ at energies above $1\;\mathrm{MeV}$. A $3$-D spatial resolution of $\approx 2\,\mathrm{mm}$ is achieved

Mapping the depleted area of silicon diodes using a micro-focused X-ray beam

For the Phase-II Upgrade of the ATLAS detector at CERN, the current ATLAS Inner Detector will be replaced with the ATLAS Inner Tracker. The ATLAS Inner Tracker will be an all-silicon detector, consisting of a pixel tracker and a strip tracker. Sensors for the ITk strip tracker are required to have a low leakage current up to bias voltages of -700 V to maintain a low noise and power dissipation. In order to minimise sensor leakage currents, particularly in the high-radiation environment inside the ATLAS detector, sensors are foreseen to be operated at low temperatures and to be manufactured from wafers with a high bulk resistivity of several k{\Omega} cm. Simulations showed the electric field inside sensors with high bulk resistivity to extend towards the sensor edge, which could lead to increased surface currents for narrow dicing edges. In order to map the electric field inside biased silicon sensors with high bulk resistivity, three diodes from ATLAS silicon strip sensor prototype wafers were studied with a monochromatic, micro-focused X-ray beam at the Diamond Light Source. For all devices under investigation, the electric field inside the diode was mapped and its dependence on the applied bias voltage was studied. The findings showed that the electric field in each diode under investigation extended beyond its bias ring and reached the dicing edge

Understanding the Humidity Sensitivity of Sensors with TCAD Simulations

The breakdown voltage of silicon sensors without special surface is known to be affected by the ambient humidity. To understand the sensor's humidity sensitivity, Synopsys TCAD was used to simulate n-in-p test structures for different effective relative humidity. Photon emission of hot electrons was imaged with a microscope to locate breakdown in the edge-region of the sensor. The Top-Transient Current Technique was used to measure charge transport near the surface in the breakdown region of the sensor. Using the measurements and simulations, the evolution of the electric field, carrier densities and avalanche breakdown in the periphery of p-bulk silicon sensors is presented

Investments in Gas Pipelines and Liquefied Natural Gas Infrastructure. What is the Impact on the Security of Supply?

This paper addresses the question of the infrastructure investment required for gas pipeline and liquefied natural gas (LNG) connections to meet growing gas demand in an enlarged EU over the next 20 years. Several issues are presented, bearing in mind the major objective of the security of supply for EU countries. First, to set the scene, recent projections of gas demand in an enlarged EU are presented along with the corresponding need for additional imports. Then a scenario is developed showing possible supply routes to meet the import gap, relying on increasingly remote routes. An impressive bill of $150 to 200 billion will have to be paid for extending and building the required infrastructure in pipeline links and LNG-receiving facilities. The expected major development of LNG markets is subject to a particular discussion, as far as the progressive globalisation of this market and its inherent flexibility provide major advantages in terms of the security of supply, despite more costly infrastructure than pipeline links. The impact of technological progress is expected to reduce both capital investment and unit transport costs, offering access to new supply opportunities. Finally, the question of major obstacles to the realisation of the required huge investments in gas infrastructure over the next 20 years is addressed, opening hot debate on the subjects of future gas price, market liberalisation and financing issues

Equilibrium with a Market of Permits

In this paper we present the main results of three original studies on the equilibrium with a market of tradeable permits in a static framework. In first study, we have considered an international equilibrium of two countries which depend on the quantity of permits to each country. The allocation is efficient if and only if it is proportional to efficient labor. A redistribution in favor of the less developed country implies a redistribution to this country but leads to a dilemma with efficiency. In the second study, we analyze the consequences of the choice between giving free permits to firms and other possibilities. We show that for equalizing incomes of production factors with there marginal productivities, each factor should receive a quantity of free permits proportional to its contribution to production. In the third study, we consider the partial equilibrium of an industry where each firm is characterized by a parameter combining production efficiency and pollution effect. We define a theoretical indicator of environmental efficiency and we analyze its properties