J Matheson

Evaluation of commercial programmable floating gate devices as radiation dosimeters

Programmable floating gate MOSFET transistors were tested with gamma radiation with doses up to approximately 100Gy (air equivalent), to evaluate their suitability as dosimeters in radiotherapy. After characterization and programming at different threshold voltages, the devices were irradiated and their Vgs shift with dose monitored in real time. Post-irradiation analysis was carried out to evaluate sensitivity, linearity, reproducibility and voltage threshold annealing. A subsequent re-programming phase followed by characterization was performed to asses their post-irradiation charge restoring capabilities. It was found that up to 73% of the initial maximum threshold voltage could be recovered. A sensitivity of up to 9 mV/Gy with an uncertainty of less than 1%, an excellent linearity up to the maximum programmable threshold voltage and low noise suggest the use of this technology for in vivo dosimetry applications.

A double-sided, shield-less stave prototype for the ATLAS Upgrade strip tracker for the High Luminosity LHC

A detailed description of the integration structures for the barrel region of the silicon strips tracker of the ATLAS Phase-II upgrade for the upgrade of the Large Hadron Collider, the so-called High Luminosity LHC (HL-LHC), is presented. This paper focuses on one of the latest demonstrator prototypes recently assembled, with numerous unique features. It consists of a shortened, shield-less, and double sided stave, with two candidate power distributions implemented. Thermal and electrical performances of the prototype are presented, as well as a description of the assembly procedures and tools.

Progress and advances in Serial Powering of silicon modules for the ATLAS Tracker Upgrade

Future detector systems will face technical difficulties with the supply of electrical power to a multitude of sub-detectors. The Serial Powering (SP) scheme is an elegant solution which leads to a great reduction in cable mass, whilst increasing efficiency and reducing cost. In recent years, substantial developments in SP have been made by the ATLAS Tracker Upgrade Community. Initial demonstrator modules and supermodules (known as Staves) used the ABCD chip, with shunt regulators made from discrete components. Continuous development of the SP architecture has led to shunt regulation within the latest ABCN-25 ASICs themselves. From a system point of view, studies of protection schemes and current sources have advanced greatly. We report recent progress, including first results from a serially powered Stavelet using the ABCN-25 chip.

HVMUX, the High Voltage Multiplexing for the ATLAS Tracker Upgrade

The increased luminosity of the HL-LHC will require more channels in the upgraded ATLAS Tracker, as a result of the finer detector segmentation. Thus, an upgraded and more efficient HV biasing of the sensors will also be needed and is among the many technological challenges facing the ATLAS Tracker Upgrade. A number of approaches, including the sharing of the same HV line among several sensors and suitable HV switches, along with their control circuitry are currently being investigated for this purpose. The proposed solutions along with latest test results and measurements will be described.

A double-sided silicon micro-strip Super-Module for the ATLAS Inner Detector upgrade in the High-Luminosity LHC

The ATLAS experiment is a general purpose detector aiming to fully exploit the discovery potential of the Large Hadron Collider (LHC) at CERN. It is foreseen that after several years of successful data-taking, the LHC physics programme will be extended in the so-called High-Luminosity LHC, where the instantaneous luminosity will be increased up to 5 × 1034 cm−2 s−1. For ATLAS, an upgrade scenario will imply the complete replacement of its internal tracker, as the existing detector will not provide the required performance due to the cumulated radiation damage and the increase in the detector occupancy. The current baseline layout for the new ATLAS tracker is an all-silicon-based detector, with pixel sensors in the inner layers and silicon micro-strip detectors at intermediate and outer radii. The super-module is an integration concept proposed for the strip region of the future ATLAS tracker, where double-sided stereo silicon micro-strip modules are assembled into a low-mass local support structure. An electrical super-module prototype for eight double-sided strip modules has been constructed. The aim is to exercise the multi-module readout chain and to investigate the noise performance of such a system. In this paper, the main components of the current super-module prototype are described and its electrical performance is presented in detail.

High voltage multiplexing for the ATLAS Tracker Upgrade

The increased luminosity of the HL-LHC will require more channels in the upgraded ATLAS Tracker, as a result of the finer detector segmentation, stemming from the otherwise too high occupancy. Among the many technological challenges facing the ATLAS Tracker Upgrade there is more an efficient power distribution and HV biasing of the sensors. The solution adopted in the current ATLAS detector uses one HV conductor for each sensor, which makes it easy to disable malfunctioning sensors without affecting the others, but space constraints and material budget considerations renders this approach impractical for the Upgraded detector. A number of approaches, including the use of the same HV line to bias several sensors and suitable HV switches, along with their control circuitry, are currently being investigated for this purpose. The proposed solutions along with latest test results and measurements will be described.

Evaluating the influence of MCM-D post-processing on silicon microstrip sensors

Silicon micro-strip modules are traditionally built as a composite object of sensors, front-end ASICs, electronics hybrid, pitch adapters and passive components. This paper reports on a novel approach to use Multi-chip Module-Deposited (MCM-D) technology to build the electronics hybrid and pitch adapter directly on the silicon sensor, by post-processing the sensor wafers. A first prototype was made to evaluate the influence of the post-processing on the sensors in terms of the electrical performance, mechanical stability and the radiation hardness. The processing was done on a wafer with miniature strip sensors and featured one dielectric layer, one metal layer and one passivation layer. This paper summarises the results from this prototype run. It reports on the sensor leakage current, strip capacitance, inter-strip resistance and charge collection efficiency. These measurements are done on non-irradiated devices and devices subjected to proton irradiation. Furthermore it reports on the mechanical integrity of the post-processed assembly.