Ulrich Parzefall

Test beam results of 3D silicon pixel sensors for the ATLAS upgrade

Results on beam tests of 3D silicon pixel sensors aimed at the ATLAS Insertable B-Layer and High Luminosity LHC (HL-LHC) upgrades are presented. Measurements include charge collection, tracking efficiency and charge sharing between pixel cells, as a function of track incident angle, and were performed with and without a 1.6 T magnetic field oriented as the ATLAS inner detector solenoid field. Sensors were bump-bonded to the front-end chip currently used in the ATLAS pixel detector. Full 3D sensors, with electrodes penetrating through the entire wafer thickness and active edge, and double-sided 3D sensors with partially overlapping bias and read-out electrodes were tested and showed comparable performance.

Charge Collection Studies and Electrical Measurements of Heavily Irradiated 3D Double-Sided Sensors and Comparison to Planar Strip Detectors

Three-dimensional (3D) silicon detectors offer advantages over standard planar devices as more radiation hard sensors. These detectors and their applications in the upgrades of the LHC experiments are discussed. 3D detectors with a double-sided geometry have been fabricated as very short strip detectors with similar inter-column spacing as proposed for the ATLAS pixel detector and LHCb vertex locator upgrades. The detectors have been irradiated up to a fluence of 2 × 1016 cm-2 1 MeV equivalent neutrons, which is twice the expected dose of the inner pixel layer of the ATLAS detector and of the upgraded LHCb vertex locator for LHC high luminosity upgrade (HL-LHC) operation. Electrical measurements show a lateral depletion voltage of only 4 V for the device before irradiation which increases to 200 V after an irradiation to a fluence of 1 × 1016 cm-2 1 MeV equivalent neutrons. The strip isolation of the p-type detectors was robust to the maximum fluence. Charge collection studies have been performed with analogue readout with 25 ns shaping time, as required for LHC experiments. The response of the detectors to high energy electrons from a 90Sr source and a collimated pulsed laser light source are shown and compared with planar devices. The 3D detector, operated at no more than 350 V, is shown to have superior charge collection characteristics to planar devices for all the fluence range expected at HL-LHC even when compared to planar devices operating at 1000 V. When operated at a bias voltage of 350 V the 3D detector collects 2.8 times more charge than a p-type planar device operated at 1000 V after a fluence of 1016 cm-2 1 MeV equivalent neutrons. Charge multiplication in 3D detectors is also reported, in both 90Sr and laser tests, which leads to further enhancement in the charge collection and signal-to-noise ratio of the detector. The effect is demonstrated, through laser tests, to occur close to the junction electrode.

Beam Test Measurements With Planar and 3D Silicon Strip Detectors Irradiated to sLHC Fluences

The planned luminosity upgrade of the CERN LHC to the super LHC (sLHC) requires investigation of new radiation hard tracking detectors. Compared to the LHC, tracking detectors must withstand a 5-10 times higher radiation fluence. Promising radiation hard options are planar silicon detectors with n-side readout and silicon detectors in 3D technology, where columnar electrodes are etched into the silicon substrate. This article presents beam test measurements per formed with planar and 3D n-in-p silicon strip detectors. The detectors were irradiated to different fluences, where the maximum fluence was 3 × 1015 1 MeV neutron equivalent particles per square centimeter (neq/cm2) for the planar detectors and 2 × 1015 neq/cm2 for the 3D detectors. In addition to signal measurements, charge sharing and resolution of both detector technologies are compared. An increased signal from the irradiated 3D detectors at high bias voltages compared to the signal from the unirradiated detector indicates that charge multiplication effects occur in the 3D detectors. At a bias voltage of 260 V, the 3D detector irradiated to 2 × 1015 neq/cm2 yields a signal almost twice as high as the signal of the unirradiated detector. Only 30% of the signal of an unirradiated detector could be measured with the planar detector irradiated to 3 × 1015 neq/cm2 at a bias voltage of 600 V, which was the highest bias voltage applied to this sensor.

Functional characterization of 3D-DDTC detectors fabricated at FBK-irst

We present selected results from the functional characterization of 3D-Double-Sided Double-Type Column (3D-DDTC) detectors fabricated at FBK, Trento. This technology features columnar electrodes etched perpendicularly to wafer surface and not passing all the way through the wafer thickness, stopping at short distance from the opposite surface. The detectors under investigation come from the first batch of these devices, made on n-type substrates. We report on the performances of microstrip sensors before and after irradiation up to 2×1015cm−2 fluences. The characterization has been carried out using a micrometer position resolved infrared laser scan and a 90Sr Beta source setup.

Short strips for the SLHC: A P-Type Silicon microstrip detector in 3D-technology

The luminosity upgrade of the Large Hadron Collider (LHC), the sLHC, will constitute an extremely challenging radiation environment for tracking detectors. With respect to the LHC, massive improvements in radiation hardness are required. In this paper we investigate the superior radiation hardness of the 3D-design, where rows of 3D-columns are etched in substrate material and joined together to form strips. To demonstrate the feasibility of 3D silicon strip detectors (SSDs) for the sLHC, we have built prototype modules using 3D single type column (3D-STC) strip detectors with short strips and front-end electronics from the present ATLAS SemiConductor Tracker (SCT). The modules were tested with a beta source setup before and after irradiation to sLHC fluences with 26 MeV protons. We report on the performance of these 3D-modules, compare it to the results prior to irradiation, and draw conclusions about options for using 3D SSDs for tracking at the sLHC.

Performance evaluation of 3D-DDTC detectors on p-type substrates

We report on the electrical and functional characterization of 3D Double-side, Double-Type-Column (3D-DDTC) detectors fabricated on p-type substrates. Results relevant to detectors in the diode, strip and pixel configurations are presented, and demonstrate a clear improvement in the charge collection performance compared to the first prototypes of these detectors.

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.

Beam Test Measurements With 3D-DDTC Silicon Strip Detectors on n-Type Substrate

For the planned luminosity upgrade of the CERN LHC to the sLHC new radiation hard technologies for the tracking detectors are investigated. Corresponding to the luminosity increase, the radiation dose will be approximately a factor of ten higher than for the detectors currently installed in the LHC experiments. One option for radiation tolerant detectors are 3D silicon detectors with columnar electrodes penetrating into the silicon bulk. This article reports results of beam test measurements performed with 3D-DDTC (Double-Sided, Double Type Column) silicon strip detectors, where the columns do not pass through the detector completely. The devices were produced by IMB-CNM (Barcelona, Spain) and by FBK-irst (Trento, Italy). Important properties like space-resolved charge collection and efficiency are investigated.

Characterization of 3D-DDTC detectors on p-type substrates

We report on the electrical and functional characterization of 3D Double-side, Double-Type-Column (3D-DDTC) detectors fabricated on p-type substrates. Results relevant to detectors in the diode, strip and pixel configurations are presented, and demonstrate a clear improvement in the charge collection performance compared to the first prototypes of these detectors.

Short Strips for the sLHC: A P-Type Silicon Microstrip Detector in 3-D Technology

The luminosity upgrade of the Large Hadron Collider (LHC), the sLHC, will constitute an extremely challenging radiation environment for tracking detectors. With respect to the LHC, large improvements in radiation hardness are required. In this paper, we investigated the expected radiation hardness of the 3-D-design, where rows of 3-D-columns are etched in substrate material and joined together to form strips. To investigate the feasibility of 3-D silicon strip detectors (SSD) for the sLHC, we have built prototype modules using 3-D single type column (3-D-STC) strip detectors with short strips and front-end electronics from the present ATLAS SemiConductor Tracker (SCT). The modules were tested with a beta source setup before and after irradiation to sLHC fluences with 26 MeV protons. We report on the performance of these 3-D-modules, compare it to the results prior to irradiation, and draw conclusions about options for using 3-D SSD detectors for tracking at the sLHC.