The ATLAS experiment is going to replace the current Inner Detector with an all new inner tracker (ITk) in the ATLAS detector for HL-LHC at CERN. Silicon strip detectors cover the outer layers of the ...barrel and the endcap sections. We have designed and fabricated a prototype single-sided n+-in-p AC-coupled silicon strip sensor for the outer barrel layer with long strips (LS), ATLAS17LS. It is of the maximum allowable size to fit in a 6-in. silicon wafer, with an outer dimension of 9.80(width)×9.76(length)cm2. The sensor features two rows of LS strip segments, 4.83 cm strip length per segment, a strip pitch of 75.5 μm, and a slim edge design. We have implemented technology for high voltage operation of up to 1000V, with a good signal collection after irradiation fluence of 5.6 × 1014neq∕cm2at the end of HL-LHC operation.
We had two objectives for the ATLAS17LS fabrication: qualification of the sensor design and fabrication quality, and providing an adequate number of the sensors for prototyping the building blocks of the strip detector. The sensors were fabricated in 3 batches by HPK with standard wafers from the foundry (320 μm physical thickness). Additional 10 sensors were fabricated with a thinner active thickness of 240 μm to investigate the influence of active thickness on charge collection. Another additional 5 sensors, with special passivation to investigate the influence of passivation on humidity sensitivity. The visual inspection of fabricated sensors revealed an inadequacy that the designed metal width of 10 μm was too narrow. The initial measurements by the vendor showed that the sensors fulfilled the specifications: onset voltages of Microdischarge VMD above the operation voltage VOP (700V for the 1st and 2nd batches; 500V for the 3rd batch, which has improved the yield), leakage currents of < 0.1μA/cm2 at VOP, full depletion voltages VFD< 330V, and rates of bad strips <<1%.
The search for neutrinoless double beta decay requires increasingly advanced methods of background reduction. A bold approach to solving this problem, in experiments using
136
Xe, is to extract and ...identify the daughter
136
Ba ion produced by double beta decay. Tagging events in this manner allows for a virtually background-free verification of double beta decay signals. Various approaches are being pursued by the nEXO collaboration to achieve Ba-tagging. A Multi-Reflection Time-of-Flight Mass Spectrometer (MR TOF) has been designed and optimized as one of the ion-identification methods, where it will investigate the ion-extraction efficiency, as well as provide further identification of the Ba isotope. The envisioned mode of operation allows the MR TOF to achieve a quickly adjustable mass-range and resolution, with simulations suggesting that a mass-resolving power of 140,000 is within reach. This work will discuss the MR TOF design and the methods employed to simulate and optimize it.
Initial tests of large format sensors for the ATLAS ITk strip tracker Klein, C.T.; Hommels, L.B.A.; Fadeyev, V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2021, Volume:
986, Issue:
C
Journal Article
Peer reviewed
Open access
For the construction of the Inner Tracker (ITk) as part of the phase-II upgrade programme of the ATLAS detector for the High-Luminosity (HL) LHC, batches of Long Strip (LS) and Short Strip (SS) ...n+-in-p type micro-strip sensors have been produced by Hamamatsu Photonics and Infineon.
The full size sensors measure approximately 98 × 98 mm2 and are designed and engineered for tolerance against the 9.7 × 1014 1 MeV neq/cm2 fluence expected at the HL-LHC, including a safety factor of 1.5. Each sensor has 2 or 4 columns of 1280 individual channels arranged at 75.5 μm horizontal pitch.
To ensure the sensors comply with their specifications, a Quality Control (QC) procedure has been implemented, comprising measurements on every individual sensor as well as on a sample basis. Every sensor is subjected to an initial visual inspection, after which the full surface of the sensor is captured with very high resolution by an automated camera setup. Non-contact metrology is performed to obtain the sensor surface profile. Electrical measurements establishing the reverse bias leakage current and depletion voltage are then conducted automatically. Sample sensors from every batch are subjected to 40 h of leakage stability checks in controlled atmosphere, and tests on every channel measuring leakage current, coupling capacitance and bias resistance are done. The recorded results are uploaded to a production database following data quality checks.
In this paper, QC test validation data and the compiled results for the first batches of production grade sensors are presented. The QC protocol was validated, and the first production sensors were confirmed to be within specification. The results are compared to those from the previous generation of prototype sensors.
Strip sensor performance in prototype modules built for ATLAS ITk Helling, C.; Allport, P.; Affolder, A.A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2020, Volume:
978, Issue:
C
Journal Article
Peer reviewed
Open access
ATLAS experiment is preparing an upgrade of its detector for High-Luminosity LHC (HL-LHC) operation. The upgrade involves installation of the new all-silicon Inner Tracker (ITk). In the context of ...the ITk preparations, more than 80 strip modules were built with prototype barrel sensors. They were tested with electrical readout on a per-channel basis. 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 an observation of high noise regions for 2 modules.
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 the relationship with sensor-level quality control tests.
Humidity sensitivity of large area silicon sensors: Study and implications Fernández-Tejero, J.; Allport, P.P.; Aviñó, O. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2020, Volume:
978, Issue:
C
Journal Article
Peer reviewed
Open access
The production of large area sensors is one of the main challenges that the ATLAS collaboration faces for the new Inner-Tracker full-silicon detector. During the prototype fabrication phase for the ...High Luminosity Large Hadron Collider upgrade, several ATLAS institutes observed indications of humidity sensitivity of large area sensors, even at relative humidities well below the dew point. Specifically, prototype Barrel and End-Cap silicon strip sensors fabricated in 6-inch wafers manifest a prompt decrease of the breakdown voltage when operating under high relative humidity, adversely affecting the performance of the sensors. In addition to the investigation of these prototype sensors, a specific fabrication batch with special passivation is also studied, allowing for a deeper understanding of the responsible mechanisms.
This work presents an extensive study of this behaviour on large area sensors. The locations of the hotspots at the breakdown voltage at high humidity are revealed using different infrared thermography techniques. Several palliative treatments are attempted, proving the influence of sensor cleaning methods, as well as baking, on the device performance, but no improvement on the humidity sensitivity was achieved. Furthermore, a study of the incidence of the sensitivity in different batches is also presented, introducing a hypothesis of the origins of the humidity sensitivity associated to the sensor edge design, together with passivation thickness and conformity. Several actions to be taken during sensor production and assembly are extracted from this study, in order to minimize the impact of humidity sensitivity on the performance of large area silicon sensors for High Energy Physics experiments.
The high luminosity upgrade of the Large Hadron Collider, foreseen for 2027, requires the replacement of the ATLAS Inner Detector with a new all-silicon Inner Tracker (ITk). The expected total ...integrated luminosity of 4000 fb−1 means that the strip part of the ITk detector will be exposed to a large radiation fluence of up to Φeq = 1.6 × 1015 1 MeV neq/cm and an ionizing dose of 0.66 MGy, including a safety factor of 1.5. Radiation-hard n+-in-p micro-strip sensors for use in the ITk have been developed by the ATLAS ITk Strip Sensor collaboration and produced by Hamamatsu Photonics K.K. In this paper, the results obtained from the electrical characterization of the latest barrel ATLAS17LS sensor prototype, before and after irradiation, are shown.
Surface properties of the long-strip barrel, full-sized and miniature sensors have been studied before and after proton, neutron and gamma irradiation up to the maximal fluences and radiation doses specified for the ITk Strip tracker. Sensors have been irradiated by protons at CYRIC, Tohoku University (Japan), the Proton Irradiation Facility at CERN, Karlsruhe Inst. Tech. (Germany) and at the University of Birmingham (UK), by neutrons from the Ljubljana TRIGA reactor (Slovenia) and by gamma rays from the 60Co source in UJP Praha (Czech Republic).
It has been verified that the surface radiation damage does not influence the sensor functionality. The breakdown voltage is well above the maximum operational voltage. All the tested surface parameters, such as the inter-strip resistance and capacitance, coupling capacitance and bias resistance satisfy the ATLAS ITk specifications for strip sensors.
The instantaneous luminosity of the Large Hadron Collider at CERN will be increased up to a factor of five with respect to the present design value by undergoing an extensive upgrade program over the ...coming decade. The most important upgrade project for the ATLAS Muon System is the replacement of the present first station in the forward regions with the so-called New Small Wheels (NSWs). The NSWs will be installed during the LHC long shutdown in 2019/2020. Small-Strip Thin Gap Chamber (sTGC) detectors are designed to provide fast trigger and high precision muon tracking under the high luminosity LHC conditions. To validate the design, a full-size prototype sTGC detector of approximately 1.2×1.0m2 consisting of four gaps has been constructed. Each gap provides pad, strip and wire readouts. The sTGC intrinsic spatial resolution has been measured in a 32GeV pion beam test at Fermilab. At perpendicular incidence angle, single gap position resolutions of about 50μm have been obtained, uniform along the sTGC strip and perpendicular wire directions, well within design requirements. Pad readout measurements have been performed in a 130GeV muon beam test at CERN. The transition region between readout pads has been found to be 4mm, and the pads have been found to be fully efficient.
PDF
