The value of the scaling parameter Eeff of the temperature dependence for current generated in silicon bulk is investigated for highly irradiated devices. Measurements of devices irradiated to ...fluences above 1×1015neqcm-2 have shown a different temperature scaling behaviour than devices irradiated to lower fluences. This paper presents the determination of the parameter Eeff for diodes irradiated with protons up to fluences of 3×1015 neqcm-2 in the bias range from 0 V to 1000 V at temperatures from −36° to 0° at different stages of annealing. It is shown that Eeff for highly irradiated devices depends on the applied electric field: below depletion voltage, Eeff is observed to have a lower value than above depletion voltage.
The innermost part of the tracking detector of the ATLAS experiment consists mainly of planar n+-in-n silicon pixel sensors. During the phase-0 upgrade, the Insertable B-Layer (IBL) was installed ...closest to the beam pipe. Its pixels are arranged with a pitch of 250 μm×50μm with a rectangular shaped n+ implantation. Based on this design modified pixel designs have been developed in Dortmund.
Six of these new pixel designs are arranged in structures of ten columns and were placed beside structures with the standard design on one sensor. Because of a special guard ring design, each structure can be powered and investigated separately. Several of these sensors were bump bonded to FE-I4 read-out chips. One of these modules was irradiated with reactor neutrons up to a fluence of 5×1015neqcm−2.
This contribution presents important sensor characteristics, charge collection determined with radioactive sources and hit efficiency measurements, performed in laboratory and test beam, of this irradiated device. It is shown that the new modified designs perform similar or better than the IBL standard design in terms of charge collection and tracking efficiency, at the cost of a slightly increased leakage current.
Planar silicon pixel sensors with modified n+-implantation shapes based on the IBL pixel sensor were designed in Dortmund. The sensors with a pixel size of 250μm× 50μm are produced in n+-in-n sensor ...technology. The charge collection efficiency should improve with electrical field strength maxima created by the different n+-implantation shapes. Therefore, higher particle detection efficiencies at lower bias voltages could be achieved. The modified pixel designs and the IBL standard design are placed on one sensor to test and compare the designs. The sensor can be read out with the FE-I4 readout chip. At the iWoRiD 2018, measurements of sensors irradiated with protons and neutrons respectively at different facilities were presented and showed incongruent results. Unintended annealing during irradiation was considered as an explanation for the observed differences in the hit detection efficiency for two neutron irradiated sensors. This hypothesis will be examined and confirmed in this work, presenting first annealing studies of sensors irradiated with neutrons in Ljubljana.
In Dortmund, planar silicon pixel sensors were designed with modified n+-implantations and produced in n+-in-n sensor technology. Baseline for these new designs was the layout of the IBL planar ...silicon pixel sensor with a 250μm×50μm pitch. The different implantation shapes are intended to cause electrical field strength maxima to increase charge collection after irradiation and thus increase particle detection efficiency. To test and compare the different pixel designs, the modified pixel designs and the standard IBL design are placed on one sensor which can be read out by a FE-I4. After irradiation with protons and neutrons respectively the performance of several sensors is tested in laboratory and test beam measurements. The presented laboratory results verify that all sensors are fully functional after irradiation. The the test beam measurements show different results for sensors irradiated to the same fluence with neutrons in Sandia compared to sensors irradiated with neutrons in Ljubljana or with protons at CERN PS.
In order to meet the requirements of the High Luminosity LHC (HL-LHC), it will be necessary to replace the current tracker of the ATLAS experiment. Therefore, a new all-silicon tracking detector is ...being developed, the so-called Inner Tracker (ITk). The use of quad chip modules is intended in its pixel region. These modules consist of a silicon sensor that forms a unit along with four read-out chips. The current ATLAS pixel detector consists of planar n-in-n silicon pixel sensors. Similar sensors and four FE-I4 read-out chips were assembled to first prototypes of planar n-in-n quad modules. The main focus of the investigation of these modules was the region between the read-out chips, especially the central area between all four read-out chips. There are special pixel cells placed on the sensor which cover the gap between the read-out chips. This contribution focuses on the characterization of a non-irradiated device, including important sensor characteristics, charge collection determined with radioactive sources as well as hit efficiency measurements, performed in the laboratory and at testbeams. In addition, first laboratory results of an irradiated device are presented.
Measurements of the leakage current scaling and tuning of front-end electronics due to temperature changes in a range between −30°C and 0°C are presented. Assemblies have been irradiated to fluences ...of 6.8×1015neqcm−2. A leakage current temperature scaling parameter Eg,eff=(1.108±0.047)eV is found, which is compatible within errors to earlier measurements of non-irradiated or lower irradiated silicon. Secondly, sensitivity of tuning parameters of the employed front-end electronics in terms of threshold and ToT values can be seen. A study of current and charge collection efficiency in an assembly irradiated to a fluence of 2×1016neqcm−2 has been carried out, showing a current related damage factor αI compatible to studies at lower irradiation levels. Charge collection stays constant with consecutively applied annealing steps and front-end electronics shows only slight changes in tuning parameters.
A novel microstrip sensor geometry, the stereo annulus, has been developed for use in the end-cap of the ATLAS experiment’s strip tracker upgrade at the HL-LHC. Its first implementation is in the ...ATLAS12EC sensors, a large-area, radiation-hard, single-sided, AC-coupled, n+-in-p design produced by the ITk Strip Sensor Collaboration and fabricated by Hamamatsu Photonics in early 2017. The results of the initial testing of two ATLAS12EC batches are presented here with a comparison to specification. The potential of the new sensor shape to reinvigorate endcap strip tracking is explained and its effects on sensor performance are isolated by comparing the bulk mechanical and electrical properties of the new sensor to the previous iteration of prototype, the conventional barrel ATLAS12A sensor. The surface properties of the new sensor are evaluated for full-size unirradiated sensors as well as for mini sensors unirradiated and irradiated with protons up to a fluence of 2.2×1015neq cm−2. The results show that the new stereo annulus ATLAS12EC sensors exhibit excellent performance and the expected irradiation evolution.
Measurements of the leakage current scaling and tuning of front-end electronics due to temperature changes in a range between -30 degree C and 0 degree C are presented. Assemblies have been ...irradiated to fluences of 6.81015neqcm-2. A leakage current temperature scaling parameter Eg,eff=(1.108 plus or minus 0.047)eV is found, which is compatible within errors to earlier measurements of non-irradiated or lower irradiated silicon. Secondly, sensitivity of tuning parameters of the employed front-end electronics in terms of threshold and ToT values can be seen. A study of current and charge collection efficiency in an assembly irradiated to a fluence of 21016neqcm-2 has been carried out, showing a current related damage factor alpha sub(I) alpha delta compatible to studies at lower irradiation levels. Charge collection stays constant with consecutively applied annealing steps and front-end electronics shows only slight changes in tuning parameters.
For the Phase-II Upgrade of the ATLAS Detector 1, 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-250) 2,2 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.
A novel microstrip sensor geometry, the stereo annulus, has been developed for use in the end-cap of the ATLAS experiment’s strip tracker upgrade at the HL-LHC. Its first implementation is in the ...ATLAS12EC sensors, a large-area, radiation-hard, single-sided, AC-coupled, n+ -in-p design produced by the ITk Strip Sensor Collaboration and fabricated by Hamamatsu Photonics in early 2017. The results of the initial testing of two ATLAS12EC batches are presented here with a comparison to specification. The potential of the new sensor shape to reinvigorate endcap strip tracking is explained and its effects on sensor performance are isolated by comparing the bulk mechanical and electrical properties of the new sensor to the previous iteration of prototype, the conventional barrel ATLAS12A sensor. The surface properties of the new sensor are evaluated for full-size unirradiated sensors as well as for mini sensors unirradiated and irradiated with protons up to a fluence of 2.2 x 1015 neq cm-2. The results show that the new stereo annulus ATLAS12EC sensors exhibit excellent performance and the expected irradiation evolution.
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