Simulation study of signal formation in position sensitive planar p-on-n silicon detectors after short range charge injection

Segmented silicon detectors (micropixel and microstrip) are the main type of detectors used in the inner trackers of Large Hadron Collider (LHC) experiments at CERN. Due to the high luminosity and eventual high fluence of energetic particles, detectors with fast response to fit the short shaping time of 20-25 ns and sufficient radiation hardness are required. Charge collection measurements carried out at the Ioffe Institute have shown a reversal of the pulse polarity in the detector response to short-range charge injection. Since the measured negative signal is about 30-60% of the peak positive signal, the effect strongly reduces the CCE even in non-irradiated detectors. For further investigation of the phenomenon the measurements have been reproduced by TCAD simulations. As for the measurements, the simulation study was applied for the p-on-n strip detectors similar in geometry to those developed for the ATLAS experiment and for the Ioffe Institute designed p-on-n strip detectors with each strip having a window in the metallization covering the p(+) implant, allowing the generation of electron-hole pairs under the strip implant. Red laser scans across the strips and the interstrip gap with varying laser diameters and Si-SiO2 interface charge densities (Q(f)) were carried out. The results verify the experimentally observed negative response along the scan in the interstrip gap. When the laser spot is positioned on the strip p(+) implant the negative response vanishes and the collected charge at the active strip increases respectively. The simulation results offer a further insight and understanding of the influence of the oxide charge density in the signal formation. The main result of the study is that a threshold value of Q(f), that enables negligible losses of collected charges, is defined. The observed effects and details of the detector response for different charge injection positions are discussed in the context of Ramo's theorem.Peer reviewe

Properties of a radiation-induced charge multiplication region in epitaxial silicon diodes

Charge multiplication (CM) in p$^+$n epitaxial silicon pad diodes of 75, 100 and 150 \upmum thickness at high voltages after proton irradiation with 1 MeV neutron equivalent fluences in the order of $10^{16}$ cm$^{-2}$ was studied as an option to overcome the strong trapping of charge carriers in the innermost tracking region of future Super-LHC detectors. Charge collection efficiency (CCE) measurements using the Transient Current Technique (TCT) with radiation of different penetration (670, 830, 1060 nm laser light and $\alpha$-particles with optional absorbers) were used to locate the CM region close to the p$^+$-implantation. The dependence of CM on material, thickness of the epitaxial layer, annealing and temperature was studied. The collected charge in the CM regime was found to be proportional to the deposited charge, uniform over the diode area and stable over a period of several days. Randomly occurring micro discharges at high voltages turned out to be the largest challenge for operation of the diodes in the CM regime. Although at high voltages an increase of the TCT baseline noise was observed, the signal-to-noise ratio was found to improve due to CM for laser light. Possible effects on the charge spectra measured with laser light due to statistical fluctuations in the CM process were not observed. In contrast, the relative width of the spectra increased in the case of $\alpha$-particles, probably due to varying charge deposited in the CM region.Comment: 11 pages, accepted by NIM

Direct observation and measurements of neutron induced deep levels responsible for N{sub eff} changes in high resistivity silicon detectors using TCT

Neutron induced deep levels responsible for changes of space charge concentration {ital N{sub eff}} in high resistivity silicon detectors have been observed directly using the transient current technique (TCT). It has been observed by TCT that the absolute value and sign of {ital N{sub eff}} experience changes due to the trapping of non- equilibrium free carriers generated near the surface (about 5 micrometers depth into the silicon) by short wavelength laser pulses in fully depleted detectors. Electron trapping causes {ital N{sub eff}} to change toward negative direction (or more acceptor-like space charges) and hole trapping causes {ital N{sub eff}} to change toward positive direction (or more donor-like space charges). The specific temperature associated with these {ital N{sub eff}} changes are those of the frozen-up temperatures for carrier emission of the corresponding deep levels. The carrier capture cross sections of various deep levels have been measured directly using different free carrier injection schemes. 10 refs., 12 figs., 3 tabs

Evidence-based medicine: new in the search for evidence

The review is focused on discussing new trends in DM, rethinking the evidence base medicine with an emphasis on demonstrating the efficacy and safety of new therapeutic agents and medical technologies, from gene editing to AI algorithms. At the same time, clinical trials of drugs are also not standing still, there is active development, new approaches, methods and designs are being developed. The process of drug development, registration and market launch of any drug takes a significant period of time, requires high financial costs and human resources. The gold standard of evidence-based medicine was initially considered to be RCTs, but at the same time, they have objective disadvantages: limited sample, inability to control all factors; insufficient follow-up time,negative impact on participants, inability to determine cause-and-effect relationships; limited measurement methods, limited budget and others. This review discusses the trends in the methodology of clinical research. The active implementation of new designs such as Adaptive Clinical Trials, "Master" protocols including Umbrella Study, Basket Study, Platform Studies, Master Observational Trials and the increased use of Single Patient Trials (N-of-1 trials) are allowing studies to become more efficient, relevant and applicable to real-life health care practice settings and patient-centered. In the review, we also look at both the pros and cons of the expanded use of biomarkers and Digital Endpoints in clinical trials and virtual clinical trials, which use mathematical models to study patient heterogeneity and its impact on various therapeutic questions. The process of expertise and regulatory approval continues to slow down the entry of drugs into the pharmaceutical market. The review considers changes in the approaches of regulators (FDA, EMEA and Russian Ministry of Health) to the drug registration procedure. The COVID-19 pandemic and sanctions have led to the need to expand the list of drugs with authorized accelerated registration. However, accelerated registration raises many questions regarding the sufficiency of the level of evidence and safety. As we can see a deep synthesis and integration of all available data is needed to achieve the next generation of evidence-based medicine. The major challenge in the next two decades will be to exploit the potential of multidimensional evidence generation by extracting, collating and generating large data sets of natural course of disease, genomics and all other omics analyses, all published clinical trials, RWD to provide next generation evidence

Long term instability in the defect assembly in irradiated high resistivity silicon detectors

Different kinetic behavior has been revealed for the two types of irradiated high resistivity silicon detectors in the reactions of the interstitial carbon (C{sub i}) annealing and the formation of the C{sub i}-O{sub i} complex. In the detectors with an increased oxygen contents prolonged growth of the C{sub i}-O{sub i} complex concentration obeyed the second order reaction due to an additional source of C{sub i} atoms which were not detected by DLTS measurements. Transformation of carbon related defects has been analyzed concerning the long term instability of irradiated silicon detectors. 5 refs., 2 figs

Scanning transient current study of the I-V stabilization phenomena in silicon detectors irradiated by fast neutrons

Investigation of the I-V stabilization phenomena in neutron irradiated silicon detectors has been carried out using scanning transient current technique (STCT) on non-irradiated PP{sup +}-p-n{sup +} detectors. The PP{sup +}-p-n{sup +} detectors were used to simulate the PP{sup +}-n-n{sup +} detectors irradiated beyond the space charge sign inversion (SCSI). Two mechanisms partially responsible for the I- V stabilization have been identified

Factors associated with adverse outcome among hospitalized patients with moderate to severe COVID-19

Aims. To consider factors associated with adverse outcome among hospitalized patients with moderate and severe COVID-19.Materials and methods. Data from 345 case histories of adult patients hospitalized with moderate to severe COVID-19 were analyzed in a single-center retrospective study. Characteristics by sex, age, number of days from disease onset to admission to hospital, duration of hospitalization, duration of disease, population characteristics by medical history of comorbidities and self-medication, outcome of hospitalization and medical technologies used in hospital conditions were given for the whole cohort of patients. All parameters were analyzed using descriptive statistics methods. Qualitative variables are given in absolute (n) and relative (%) values with 95% confidence interval. Continuous variables were presented as median and quartiles. Risk factors for mortality were determined across groups using the χ2  criterion and odds ratio.Results. There was no demonstrated effect of gender, degree of pulmonary tissue lesions on computed tomography data, or time of initiation of respiratory support on disease outcome. At the same time, the age older than 65 years as well as neoplasms, type 2 diabetes mellitus, dementia, Stage 3 arterial hypertension, chronic heart failure, coronary heart disease, myocardial infarction and stroke history, chronic obstructive pulmonary disease, bronchiectatic disease, urogenital diseases were the predictors of unfavorable outcome in patients with moderate and severe COVID-19 form. Prehospital use of antiplatelet agents, direct and indirect oral anticoagulants, drugs affecting the renin-angiotensin system, systemic glucocorticosteroids, antibiotics, antiviral drugs, and analgesics was associated with a decrease in the mortality rate in patients with moderate-to-severe COVID-19, as well as timely use of pronposition and transfer to intensive care unit.Conclusions. Our findings are partially consistent with previous reports on the effect of risk factors on COVID-19 outcomes

Systemic characteristic of safety profile of monoclonal antibodies used in rheumatology practice

Monoclonal antibodies are highly effective medications, which made a breakthrough in medicine. Taking into consideration the properties of monoclonal antibodies safety plays a key role in “risk-benefit” assessment. For monoclonal antibodies this remains studied insufficiently. The article presents a systemic characteristic of safety profile of monoclonal antibodies used in rheumatology, based on the database of spontaneous reports of the Federal Service for the Supervision of Healthcare. Specified greater alertness of Russian practitioners regarding the risk of developing tuberculosis infections in comparison to their foreign counterparts. Spontaneous reports of the development of neoplasms and deviations of laboratory tests, according to our data, on the contrary, are reported less. It is advisable to draw the attention of practitioners to the peculiarities of work with isolated deviations in laboratory tests and keep alert about the safety issues of monoclonal antibodies in general. It is important to continue monitoring to characterize delayed type D adverse drug reactions

Investigation of epitaxial silicon layers as a material for radiation hardened silicon detectors

Epitaxial grown thick layers ({ge} 100 micrometers) of high resistivity silicon (Epi-Si) have been investigated as a possible candidate of radiation hardened material for detectors for high-energy physics. As grown Epi-Si layers contain high concentration (up to 2 {times} 10{sup 12} cm{sup {minus}3}) of deep levels compared with that in standard high resistivity bulk Si. After irradiation of test diodes by protons (E{sub p} = 24 GeV) with a fluence of 1.5 {times} 10{sup 11} cm{sup {minus}2}, no additional radiation induced deep traps have been detected. A reasonable explanation is that there is a sink of primary radiation induced defects (interstitial and vacancies), possibly by as-grown defects, in epitaxial layers. The ``sinking`` process, however, becomes non-effective at high radiation fluences (10{sup 14} cm{sup {minus}2}) due to saturation of epitaxial defects by high concentration of radiation induced ones. As a result, at neutron fluence of 1 {times} 10{sup 14} cm{sup {minus}2} the deep level spectrum corresponds to well-known spectrum of radiation induced defects in high resistivity bulk Si. The net effective concentration in the space charge region equals to 3 {times} 10{sup 12} cm{sup {minus}3} after 3 months of room temperature storage and reveals similar annealing behavior for epitaxial as compared to bulk silicon