140 research outputs found
Lithium ion-induced damage in silicon detectors
No full textSilicon diodes processed by CNM on standard and oxygenated silicon substrates have been irradiated by 58MeV lithium ions. The radiation-induced effects are very similar to the one observed after proton irradiation: substrate space charge sign inversion (SCSI), lower increase of the effective substrate doping concentration after SCSI for the oxygenated devices. The experimental radiation hardness factor has been determined to be 45.01, within 8.2% with the expected value. These results suggest that 58MeV Li ions are a suitable radiation source for radiation hardness studies by ions heavier than protons for the future very high luminosity hadron colliders
Radiation hardness of silicon detectors for high-energy physics applications
No full textOxygenated and standard (not oxygenated) silicon diodes processed by CNM and IRST have been irradiated by 27 MeV protons and compared with standard devices from ST Microelectronics. As expected, the leakage current density increase rate (α) and its annealing do not show any significant dependence on starting material, oxygenation and/or device processing. On the contrary, oxygenation improves the radiation hardness by decreasing the acceptor introduction rate (β) and mitigating the depletion voltage (Vdep) increase, with the β parameter depending also on starting material and/or effects related to device processing for standard diodes. Finally, these results are included in a general review on the state of the art for silicon detector radiation hardening, confirming the good performance of the considered technologies
Lithium ion irradiation of standard and oxygenated silicon diodes
No full textThe next generation silicon detectors for future very high luminosity colliders or a possible LHC upgrade scenario will require radiation-hard detectors for fluences up to 10^(16) 1-MeV equivalent neutrons/cm^(2). These high fluences present strong constraints because long irradiation times are required at the currently available proton irradiation facilities. Energetic (58 MeV) Lithium ions present a non-ionizing energy loss higher than protons and neutrons, and could consequently be a new promising radiation source for investigating the radiation hardness of silicon detectors up to very high particle fluences. Starting from this premise, we have investigated the degradation, as measured by the leakage current density increase and depletion voltage variations in the short- and long-term characteristics, induced by 58 MeV Li ions in state-of-the-art silicon diodes processed by two different manufacturers on standard and oxygenated silicon substrates. Finally, the correlation between the radiation damage induced by 58 MeV Li ions and 27 MeV protons is discussed
Radiation hardness of silicon detectors for high-energy physics applications
No full textOxygenated and standard (not oxygenated) silicon diodes processed by CNM and IRST have been irradiated by 27 MeV protons and compared with standard devices from ST Microelectronics. As expected, the leakage current density increase rate (alfa) and its annealing do not show any significant dependence on starting material, oxygenation and/or device processing. On the contrary, oxygenation improves the radiation hardness by decreasing the acceptor introduction rate (beta) and mitigating the depletion voltage (Vdep) increase, with the beta parameter depending also on starting material and/or effects related to device processing for standard diodes. Finally, these results are included in a general review on the state of the art for silicon detector radiation hardening, confirming the good performance of the considered technologies
Radiation Hardness of Silcon Diodes for High Energy Physics Aplications
No full textOxygenated and standard (not oxygenated) silicon diodes processed by CNM and IRST have been irradiated by 27 MeV protons and compared with standard devices from ST Microelectronics. As expected the leakage current density increase rate (α) and its annealing do not show any significant dependence on the starting material, oxygenation and/or processing of the considered devices. On the contrary, oxygenation improves the radiation hardness by decreasing the acceptor introduction rate (β) and mitigating the depletion voltage (Vdep) increase, with the β parameter depending also on starting material and/or effects related to device processing for standard diodes. Finally these results are included in a general review on the state of the art for silicon detector radiation hardening, confirming the good performance of the considered technologies
Quality Assurance methodology for the ATLAS Inner Tracker strip sensor production
No full textThe production of the strip sensors for the ATLAS Inner Tracker (ITk) will start in 2020. Nearly 22,000 large area sensors will be produced over a period of about five years by Hamamatsu Photonics K.K. (HPK). The institutes involved in the sensor development and production are committed to deliver and maintain the highest quality sensors for the experiment. A Quality Assurance (QA) strategy has been prepared to be carried out during the whole production period. Once the process has been characterized as providing the required pre-irradiation specifications and the proper radiation hardness, the onus is on the manufacturer to rigidly stick to that qualified process. Still, sample testing with specific device-element structures and irradiation of devices should be implemented by the ITk sensor collaboration. A detailed irradiation and testing plan has been prepared by the ATLAS-ITk Collaboration, together with a newly designed test chip with specific structures to monitor different key technological and device parameters during the whole production. The tests and irradiations will be carried out on a sample basis. In order to have a practical methodology, samples from alternating batches will be sent for irradiations with protons, neutrons and gammas, and then tested in order to check that the characteristics remain within specifications. The detailed plan and the design and test methods for the structures in the test chip are presented here
Student and teacher perceptions of preparation in mathematics in middle school and its impact on students' self-efficacy and performance in an upper secondary school in Western Australia
No full textMiddle school initiatives (including heterogeneous classes and an integrated, flexible curriculum together with promotion of student input) have been implemented in schools in Western Australia in response to a perceived need to align schools more closely with a more student-centred approach to learning, in the expectation of meeting more students' needs and thereby reducing student dissatisfaction and increasing the possibility of students pursuing life long learning. Specific goals underlying the initiative include the development of independent learning and student responsibility for learning through a series of strategies such as self-paced learning, student involvement in negotiating their own learning, and a strong emphasis on respecting and valuing student input into the implementation of curricula. However, owing to the way that the curricula for Middle and Upper secondary school mathematics are currently structured, problems might arise for students in the transition from a relaxed to a highly discipline-based organization of content (as described by Venville, Wallace, Rennie, Malone (1998). Students accustomed to the current approaches implemented in Middle schools (Years 8 to 10) may be disadvantaged in the transition to Upper secondary school courses (Years 11 and 12) compared with those students who have been exposed to a more discipline-based organization of content throughout early adolescence and prior to entry into courses leading to tertiary entrance (T.E.E. courses). The aim of this project was to investigate the possible effects of Middle school initiatives in a group of students from three Middle schools in Western Australia in one subject area - mathematics - on the perceptions of self-efficacy and preparation in mathematics once the students encounter Year 11 Upper school courses.
A survey containing Likert-type rating scales pertinent to four areas of interest - Self-efficacy in mathematics; Self-Directed Regulation; Views on current teaching; and Views on prior teaching were administered to students transferring from three 'feeder' Middle schools to Year 11 (Upper secondary school) classes in one Senior College in Western Australia for each of 4 consecutive years. Students were also asked for their comments regarding preparation for the challenges of their chosen courses in mathematics. In addition, their levels of performance in a range of mathematical skills were assessed using a teacher-developed test. The perceptions of their Middle and Senior School teachers were also sought. As the survey was administered to all students as a routine part of action research within the mathematics faculty at the Senior College, only the results of those students who subsequently agreed to be participants in the study are reported in this dissertation. Results indicated that a mismatch existed in approaches and skills between Middle School and Senior College Mathematics. The reliance on students making suitable choices for themselves, the absence of specialist teachers of mathematics in middle schools, mixed ability classes in which specialist teachers of mathematics find it difficult to operate successfully and a curriculum that was so flexible that teachers omitted key elements required for later studies were the main factors that resulted in a significant number of students making the transition from middle to senior school with insufficient preparation. Implications for the teaching of mathematics in these three Middle schools and the Upper school are discussed
Testbeam Studies on Pick-Up in Sensors with Embedded Pitch Adapters
No full textFor silicon strip sensors, the tracking information specifications can lead to challenging requirements for wire bonding. A common strategy is to use external pitch adapters to facilitate this step in the production of detector modules. A novel approach previously discussed in [1], is to implement the pitch adapters in the sensor, by embedding a second layer of metal tracks. The use of these embedded pitch adapters (EPAs) decouples the bond pad layout of the sensor from its implant layout by moving the adaption to the sensor production step. This solution, however, can yield the risk of performance losses due to the increase of inter-strip capacitance, or unwanted capacitive coupling between the metal layers (cross-talk) or the silicon bulk and the second metal layer (pick-up). In the prototyping stage of the ATLAS tracker end-cap upgrade, where different bond-pad layouts on sensor and readout chip lead to extremely challenging wire-bonding conditions, sensors with different geometries of EPA implementations have been produced at Centro Nacional de Microelectronica (IMB-CNM, CSIC), Barcelona, Spain. In order to study the influence of the EPA on the sensor performance, these sensors, built into a prototype detector module, were investigated in an x-ray beam. In this contribution, results of a study on the pick-up phenomenon in sensor regions with a high density of second-metal-layer tracks are presented. The performed measurements were taken in 15~m by 10~m steps with a micro-focussed 15~keV photon beam which allows resolution of the details of the EPA geometry. The amount of signal degradation in primary strips in the presence of second-metal tracks as well as the size of the pick-up-induced signal in the deployed test setup are quantified. Recommendations regarding the geometry of the embedded pitch adapter are given, resulting in limits and opportunities for future applications. [1] M. Ullan et al., Embedded Pitch Adapters: a High-Yield Interconnection Solution for Strip Sensors, NIM A, 201
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