Characterization of the ALPIDE chip with Helium-4 ions for Proton Computed Tomography

Particle therapy has become an appealing therapeutic option for patients with various tumor types. The physical properties of charged particles allow for an improved dose distribution conformality compared to conventional photon-based radiotherapy. This advantage translates into a reduction of unwanted side effects from radiation treatment and in the long run will improve the patient’s quality of life. A team at the University of Bergen is developing a proton Computed Tomography (pCT) scanner prototype. This technology will primarily work as a supplement to particle therapy as it aims to enhance the accuracy of the pre-calculated dose plans applied during treatment. The pCT system is a Digital Tracking Calorimeter (DTC) consisting of multiple layers of the ALPIDE CMOS Monolithic Active Pixel Sensor with the aim of tracking protons and measure its energy. This thesis studies the ALPIDE chip towards its medical applications in the future DTC. It will describe the clusters created on the chip by helium ions and alpha particles with a focus on the parameters that affect the pixel size of the clusters. Results from an analysis of a helium microbeam indicate that the size of a cluster correlates with the position of the incoming particle on the pixel and hence, the interior location of the energy deposition. These clusters varied in size from 5 to 35 pixels when the beam scanned the chip in µm steps. Moreover, an experiment conducted during this project shows that the size of the clusters is dependent on the temperature of the chip and that the average size of the cluster gets larger with increasing temperature. In the end, the results obtained from an ALPIDE telescope irradiated with high energetic helium beams is described. This experiment shows that the clusters used in tracking increases in size at higher Linear Energy Transfer (LET) of the particles.Masteroppgave i fysikkMAMN-PHYSPHYS39

Radiation hard 3D silicon pixel sensors for use in the ATLAS detector at the HL-LHC

The High Luminosity LHC (HL-LHC) upgrade requires the planned Inner Tracker (ITk) of the ATLAS detector to tolerate extremely high radiation doses. Specifically, the innermost parts of the pixel system will have to withstand radiation fluences above 1 × 1016 neqcm-2. Novel 3D silicon pixel sensors offer a superior radiation tolerance compared to conventional planar pixel sensors, and are thus excellent candidates for the innermost parts of the ITk. This paper presents studies of 3D pixel sensors with pixel size 50 × 50 μm2 mounted on the RD53A prototype readout chip. Following a description of the design and fabrication steps, Test Beam results are presented for unirradiated as well as heavily irradiated sensors. For particles passing at perpendicular incidence, it is shown that average efficiencies above 96% are reached for sensors exposed to fluences of 1 × 1016 neqcm-2 when biased to 80 V.publishedVersio

Novel 3D Pixel Sensors for the Upgrade of the ATLAS Inner Tracker

The ATLAS experiment will undergo a full replacement of its inner detector to face the challenges posed by the High Luminosity upgrade of the Large Hadron Collider (HL-LHC). The new Inner Tracker (ITk) will have to deal with extreme particle fluences. Due to its superior radiation hardness the 3D silicon sensor technology has been chosen to instrument the innermost pixel layer of ITk, which is the most exposed to radiation damage. Three foundries (CNM, FBK, and SINTEF), have developed and fabricated novel 3D pixel sensors to meet the specifications of the new ITk pixel detector. These are produced in a single-side technology on either Silicon On Insulator (SOI) or Silicon on Silicon (Si-on-Si) bonded wafers by etching both n- and p-type columns from the same side. With respect to previous generations of 3D sensors they feature thinner active substrates and smaller pixel cells of 50 × 50 and 25 × 100 µm2. This paper reviews the main design and technological issues of these novel 3D sensors, and presents their characterization before and after exposure to large radiation doses close to the one expected for the innermost layer of ITk. The performance of pixel modules, where the sensors are interconnected to the recently developed RD53A chip prototype for HL-LHC, has been investigated in the laboratory and at beam tests. The results of these measurements demonstrate the excellent radiation hardness of this new generation of 3D pixel sensors that enabled the project to proceed with the pre-production for the ITk tracker.publishedVersio

Characterization of the ALPIDE chip with Helium-4 ions for Proton Computed Tomography

Particle therapy has become an appealing therapeutic option for patients with various tumor types. The physical properties of charged particles allow for an improved dose distribution conformality compared to conventional photon-based radiotherapy. This advantage translates into a reduction of unwanted side effects from radiation treatment and in the long run will improve the patient’s quality of life. A team at the University of Bergen is developing a proton Computed Tomography (pCT) scanner prototype. This technology will primarily work as a supplement to particle therapy as it aims to enhance the accuracy of the pre-calculated dose plans applied during treatment. The pCT system is a Digital Tracking Calorimeter (DTC) consisting of multiple layers of the ALPIDE CMOS Monolithic Active Pixel Sensor with the aim of tracking protons and measure its energy. This thesis studies the ALPIDE chip towards its medical applications in the future DTC. It will describe the clusters created on the chip by helium ions and alpha particles with a focus on the parameters that affect the pixel size of the clusters. Results from an analysis of a helium microbeam indicate that the size of a cluster correlates with the position of the incoming particle on the pixel and hence, the interior location of the energy deposition. These clusters varied in size from 5 to 35 pixels when the beam scanned the chip in µm steps. Moreover, an experiment conducted during this project shows that the size of the clusters is dependent on the temperature of the chip and that the average size of the cluster gets larger with increasing temperature. In the end, the results obtained from an ALPIDE telescope irradiated with high energetic helium beams is described. This experiment shows that the clusters used in tracking increases in size at higher Linear Energy Transfer (LET) of the particles

Study of the timing performance of the SKIROC2-CMS for the CMS HGCAL

The High Luminosity phase of the LHC (starting operation in 2025) will provide unprecedented instantaneous and integrated luminosity, with 25 ns bunch crossing intervals and up to 140 pileup events. In this context, the High Granularity Calorimeter will provide electromagnetic and hadronic energy measurement in the forward direction of the upgraded CMS. The test beam campaign of the first HGCal modules, started in Summer 2016 at CERN with 8 fully equipped layers of the EE section, will continue in Summer 2017 aiming at the test of a full prototype including the electronic and the hadronic parts. The assessment of the calorimeter performance on a beam test bench is a fundamental phase for the development of a new detector, allowing to test the mechanical structure and electronic chain, characterize the modules performance and measure the shower developments for electrons and hadrons. The aim of the work was to determine the timing performance and the timing characteristics of the single module tested in May 2016 at CERN

Test Beam Results of SINTEF 3D Pixel Silicon Sensors

The Inner Tracker (ITk) of the ATLAS detector must withstand extreme radiation conditions at the High Luminosity LHC (HL- LHC). 3D sensors are promising candidates for the innermost detector layers as their radiation tolerance are superior to that of conventional planar pixel sensors. The ATLAS groups in Oslo and Bergen have collaborated with SINTEF on the development of 3D sensors for many years. We present an efficiency analysis of SINTEF 3D silicon sensors. Results show high efficiencies above 96% at 60V (80V) after exposure to fluences of 1.0 (1.8) x 10ˆ16 n cmˆ-2

Radiation hard 3D silicon pixel sensors for use in the ATLAS detector at the HL-LHC

The High Luminosity LHC (HL-LHC) upgrade requires the planned Inner Tracker (ITk) of the ATLAS detector to tolerate extremely high radiation doses. Specifically, the innermost parts of the pixel system will have to withstand radiation fluences above 1 × 1016 neqcm-2. Novel 3D silicon pixel sensors offer a superior radiation tolerance compared to conventional planar pixel sensors, and are thus excellent candidates for the innermost parts of the ITk. This paper presents studies of 3D pixel sensors with pixel size 50 × 50 μm2 mounted on the RD53A prototype readout chip. Following a description of the design and fabrication steps, Test Beam results are presented for unirradiated as well as heavily irradiated sensors. For particles passing at perpendicular incidence, it is shown that average efficiencies above 96% are reached for sensors exposed to fluences of 1 × 1016 neqcm-2 when biased to 80 V.publishedVersio

Test Beam Results of SINTEF 3D Pixel Silicon Sensorsb

This paper presents test beam results of SINTEF 3D pixel sensors designed for the Inner Tracker (ITk) of the ATLAS detector at the High Luminosity LHC (HL-LHC). The sensors are required to withstand extreme radiation doses and to maintain efficiency above 96-97% after a lifetime operation at the ITk. We present details on the production and design of these sensors, the setup for the experiment at CERN, and the analysis of the test beam data. Results are promising, showing excellent position resolution and high efficiencies after irradiation. The sensors meet the operational efficiency targets for both perpendicular and tilted configurations, validating their design and performance for future HL-LHC operations

Novel 3D Pixel Sensors for the Upgrade of the ATLAS Inner Tracker

The ATLAS experiment will undergo a full replacement of its inner detector to face the challenges posed by the High Luminosity upgrade of the Large Hadron Collider (HL-LHC). The new Inner Tracker (ITk) will have to deal with extreme particle fluences. Due to its superior radiation hardness the 3D silicon sensor technology has been chosen to instrument the innermost pixel layer of ITk, which is the most exposed to radiation damage. Three foundries (CNM, FBK, and SINTEF), have developed and fabricated novel 3D pixel sensors to meet the specifications of the new ITk pixel detector. These are produced in a single-side technology on either Silicon On Insulator (SOI) or Silicon on Silicon (Si-on-Si) bonded wafers by etching both n- and p-type columns from the same side. With respect to previous generations of 3D sensors they feature thinner active substrates and smaller pixel cells of 50 × 50 and 25 × 100 µm2. This paper reviews the main design and technological issues of these novel 3D sensors, and presents their characterization before and after exposure to large radiation doses close to the one expected for the innermost layer of ITk. The performance of pixel modules, where the sensors are interconnected to the recently developed RD53A chip prototype for HL-LHC, has been investigated in the laboratory and at beam tests. The results of these measurements demonstrate the excellent radiation hardness of this new generation of 3D pixel sensors that enabled the project to proceed with the pre-production for the ITk tracker

Novel 3D Pixel Sensors for the Upgrade of the ATLAS Inner Tracker

The ATLAS experiment will undergo a full replacement of its inner detector to face the challenges posed by the High Luminosity upgrade of the Large Hadron Collider (HL-LHC). The new Inner Tracker (ITk) will have to deal with extreme particle fluences. Due to its superior radiation hardness the 3D silicon sensor technology has been chosen to instrument the innermost pixel layer of ITk, which is the most exposed to radiation damage. Three foundries (CNM, FBK, and SINTEF), have developed and fabricated novel 3D pixel sensors to meet the specifications of the new ITk pixel detector. These are produced in a single-side technology on either Silicon On Insulator (SOI) or Silicon on Silicon (Si-on-Si) bonded wafers by etching both n- and p-type columns from the same side. With respect to previous generations of 3D sensors they feature thinner active substrates and smaller pixel cells of 50 × 50 and 25 × 100 µm2. This paper reviews the main design and technological issues of these novel 3D sensors, and presents their characterization before and after exposure to large radiation doses close to the one expected for the innermost layer of ITk. The performance of pixel modules, where the sensors are interconnected to the recently developed RD53A chip prototype for HL-LHC, has been investigated in the laboratory and at beam tests. The results of these measurements demonstrate the excellent radiation hardness of this new generation of 3D pixel sensors that enabled the project to proceed with the pre-production for the ITk tracker