Radiation Induced Point and Cluster-Related Defects with Strong Impact to Damage Properties of Silicon Detectors

This work focuses on the investigation of radiation induced defects responsible for the degradation of silicon detectors. Comparative studies of the defects induced by irradiation with 60Co- rays, 6 and 15 MeV electrons, 23 GeV protons and 1 MeV equivalent reactor neutrons revealed the existence of point defects and cluster related centers having a strong impact on damage properties of Si diodes. The detailed relation between the microscopic reasons as based on defect analysis and their macroscopic consequences for detector performance are presented. In particular, it is shown that the changes in the Si device properties after exposure to high levels of 60Co- doses can be completely understood by the formation of two point defects, both depending strongly on the Oxygen concentration in the silicon bulk. Specific for hadron irradiation are the annealing effects which decrease resp. increase the originally observed damage effects as seen by the changes of the depletion voltage. A group of three cluster related defects, revealed as deep hole traps, proved to be responsible specifically for the reverse annealing. Their formation is not affected by the Oxygen content or Si growth procedure suggesting that they are complexes of multi-vacancies located inside extended disordered regions.Comment: 14 pages, 15 figure

Design and First Tests of a Radiation-Hard Pixel Sensor for the European X-Ray Free-Electron Laser

The high intensity and high repetition rate of the European X-ray Free-Electron Laser, presently under construction in Hamburg, requires silicon sensors which can stand X-ray doses of up to 1 GGy for 3 years of operation at high bias voltage. Within the AGIPD Collaboration the X-ray-radiation damage in MOS Capacitors and Gate-Controlled Diodes fabricated by four vendors on high-ohmic n-type silicon with two crystal orientations and dif- ferent technological parameters, has been studied for doses between 1 kGy and 1 GGy. The extracted values of oxide-charge and surface-current densi- ties have been used in TCAD simulations, and the layout and technological parameters of the AGIPD pixel sensor optimized. It is found that the op- timized layout for high X-ray doses is significantly different from the one for non-irradiated sensors. First sensors and test structures have been de-livered in early 2013. Measurement results for X-ray doses of 0 to 10 MGy and their comparison to simulations are presented. They demonstrate that the optimization has been successful and that the sensors fulfill the required specifications

Themenkonkurrenz in der Coronapandemie. Thematisierungsprozesse am Beispiel medialer Verdrängung der Themen «Klima» und «Geflüchtete» in der Coronakrise

In der vorgelegten Studie werden klassische Annahmen zur Drama-tisierungstendenz medialer Krisenberichterstattung bei gleichzeitiger Verdrängung übriger gesellschaftlich relevanter Themen auf den Prüfstand gestellt. Anwendungsbeispiel ist die Corona-Thematisierung (September 2019 bis Dezember 2020) und ihr Einfluss auf die Thema-tisierungsprozesse von «Klima» und «Geflüchtete». Anhand einer multivariat dynamischen Zeitreihenanalyse von 437 784 Onlineartikeln wird als übergeordnete Hypothese untersucht, ob Themenverdrän-gung festgestellt werden kann. Die Mechanismen der Verdrängung werden dann differenziert als phasenabhängige Aufmerksamkeits-verschiebung und als direkte also zeitgleiche Themenverdrängung untersucht. Die Ergebnisse bestätigen die Annahme der Themen-konkurrenz und zeigen je nach Thematisierungsphase unterschiedliche Verdrängungsprozesse. Im Trend hat Corona die Thematisierung der beiden anderen Krisenphänomene zwar nicht komplett verdrängt, aber sehr deutlich reduziert. Bezüglich der direkten Verdrängung sind Effekte messbar, aber eher klein. Als Fazit zeigt sich Themenverdrän-gung im Onlinejournalismus hier also eher als Effekt der Fokusver-schiebung öffentlicher Aufmerksamkeit als ein Problem direkter Ver-drängung aufgrund beschränkten Berichterstattungsraums. In the following, classical hypotheses on the dramatization tendency of media crisis reporting and the assumed simultaneous suppression of other socially relevant topics are put to the test. For this case study, we rely on news reporting during the first year of the COVID19 pandemic (September 2019 to December 2020) to evaluate its influence on the thematization processes of «climate» and «refu-gees.» Based on a multivariate dynamic time series analysis of 437 784 online articles, we first confirm whether overall issue displace-ment can be detected and then delve deeper by differentiating into two possible mechanisms of displacement: 1) as a phase-dependent but global shift in attention and 2) as a direct i.e., simultaneous effect pointing toward editorial competition. Results from our analysis con-firm the overarching hypothesis of topic competition, clearly showing displacement processes depending on the thematization phase. Globally, while not being rendered invisible, media attention for the other two crisis phenomena was reduced significantly following the onset of the pandemic. Regarding direct displacement, effects are measurable, but rather small. We conclude that the displacement of media attention seems to be attributable more to a shift in public attention and overall trends than to classic assumptions based on limited resources in the editorial process

Investigation of X-ray induced radiation damage at the Si-SiO2 interface of silicon sensors for the European XFEL

Experiments at the European X-ray Free Electron Laser (XFEL) require silicon pixel sensors which can withstand X-ray doses up to 1 GGy. For the investigation of X-ray radiation damage up to these high doses, MOS capacitors and gate-controlled diodes built on high resistivity n-doped silicon with crystal orientations and produced by two vendors, CiS and Hamamatsu, have been irradiated with 12 keV X-rays at the DESY DORIS III synchrotron light source. Using capacitance/conductance-voltage, current-voltage and thermal dielectric relaxation current measurements, the surface densities of oxide charges and interface traps at the Si-SiO2 interface, and the surface-current densities have been determined as function of dose. Results indicate that the dose dependence of the surface density of oxide charges and the surface-current density depend on the crystal orientation and producer. In addition, the influence of the voltage applied to the gates of the MOS capacitor and the gate-controlled diode during X-ray irradiation on the surface density of oxide charges and the surface-current density has been investigated at doses of 100 kGy and 100 MGy. It is found that both strongly depend on the gate voltage if the electric field in the oxide points from the surface of the SiO2 to the Si-SiO2 interface. Finally, annealing studies have been performed at 60 and 80 degree C on MOS capacitors and gate-controlled diodes irradiated to 5 MGy and the annealing kinetics of oxide charges and surface current determined.Comment: 10 pages, 6 figures, 3 table

Silicon Sensors implemented on p-type substrates for high radiation resistance applications

Silicon based micropattern detectors are essential elements of modern high energy physics experiments. Cost effectiveness and high radiation resistance are two important requirements for technologies to be used in inner tracking devices. Processes based on p-type substrates have very strong appeal for these applications. Recent results and prototype efforts under way are reviewed.Comment: 7 pages, 2 figures; invited paper at Vertex 2006, Perugia, Italy, september 200

3-D Printed Protective Equipment during COVID-19 Pandemic

While the number of coronavirus cases from 2019 continues to grow, hospitals are reporting shortages of personal protective equipment (PPE) for frontline healthcare workers. Furthermore, PPE for the eyes and mouth, such as face shields, allow for additional protection when working with aerosols. 3-D printing enables the easy and rapid production of lightweight plastic frameworks based on open-source data. The practicality and clinical suitability of four face shields printed using a fused deposition modeling printer were examined. The weight, printing time, and required tools for assembly were evaluated. To assess the clinical suitability, each face shield was worn for one hour by 10 clinicians and rated using a visual analogue scale. The filament weight (21-42 g) and printing time (1:40-3:17 h) differed significantly between the four frames. Likewise, the fit, wearing comfort, space for additional PPE, and protection varied between the designs. For clinical suitability, a chosen design should allow sufficient space for goggles and N95 respirators as well as maximum coverage of the facial area. Consequently, two datasets are recommended. For the final selection of the ideal dataset to be used for printing, scalability and economic efficiency need to be carefully balanced with an acceptable degree of protection