Simulation of radiation-induced defects

Mainly due to their outstanding performance the position sensitive silicon detectors are widely used in the tracking systems of High Energy Physics experiments such as the ALICE, ATLAS, CMS and LHCb at LHC, the world's largest particle physics accelerator at CERN, Geneva. The foreseen upgrade of the LHC to its high luminosity (HL) phase (HL-LHC scheduled for 2023), will enable the use of maximal physics potential of the facility. After 10 years of operation the expected fluence will expose the tracking systems at HL-LHC to a radiation environment that is beyond the capacity of the present system design. Thus, for the required upgrade of the all-silicon central trackers extensive measurements and simulation studies for silicon sensors of different designs and materials with sufficient radiation tolerance have been initiated within the RD50 Collaboration. Supplementing measurements, simulations are in vital role for e.g. device structure optimization or predicting the electric fields and trapping in the silicon sensors. The main objective of the device simulations in the RD50 Collaboration is to develop an approach to model and predict the performance of the irradiated silicon detectors using professional software. The first successfully developed quantitative models for radiation damage, based on two effective midgap levels, are able to reproduce the experimentally observed detector characteristics like leakage current, full depletion voltage and charge collection efficiency (CCE). Recent implementations of additional traps at the SiO$_2$/Si interface or close to it have expanded the scope of the experimentally agreeing simulations to such surface properties as the interstrip resistance and capacitance, and the position dependency of CCE for strip sensors irradiated up to $\sim$$1.5\times10^{15}$ n$_{\textrm{eq}}\textrm{cm}^{-2}$.Comment: 13 pages, 11 figures, 6 tables, 24th International Workshop on Vertex Detectors, 1-5 June 2015, Santa Fe, New Mexico, US

Silicon Sensors for Trackers at High-Luminosity Environment

The planned upgrade of the LHC accelerator at CERN, namely the high luminosity (HL) phase of the LHC (HL-LHC foreseen for 2023), will result in a more intense radiation environment than the present tracking system was designed for. The required upgrade of the all-silicon central trackers at the ALICE, ATLAS, CMS and LHCb experiments will include higher granularity and radiation hard sensors. The radiation hardness of the new sensors must be roughly an order of magnitude higher than the one of LHC detectors. To address this, a massive R&D program is underway within the CERN RD50 collaboration "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" to develop silicon sensors with sufficient radiation tolerance. Research topics include the improvement of the intrinsic radiation tolerance of the sensor material and novel detector designs with benefits like reduced trapping probability (thinned and 3D sensors), maximized sensitive area (active edge sensors) and enhanced charge carrier generation (sensors with intrinsic gain). A review of the recent results from both measurements and TCAD simulations of several detector technologies and silicon materials at radiation levels expected for HL-LHC will be presented.Comment: 7 pages, 9 figures, 10th International Conference on Radiation Effects on Semiconductor Materials, Detectors and Devices (RESMDD14), 8-10 October, Firenze, Ital

Experimental and simulation study of irradiated silicon pad detectors for the CMS High Granularity Calorimeter

The foreseen upgrade of the LHC to its high luminosity phase (HL-LHC), will maximize the physics potential of the facility. The upgrade is expected to increase the instantaneous luminosity by a factor of 5 and deliver an integrated luminosity of 3000 fb-1 after 10 years of operation. As a result of the corresponding increase in radiation and pileup, the electromagnetic calorimetry in the CMS endcaps will sustain maximum integrated doses of 1.5 MGy and neutron fluences above 1e16 neq/cm2, necessitating their replacement for HL-LHC operation. The CMS collaboration has decided to replace the existing endcap electromagnetic and hadronic calorimeters by a High Granularity Calorimeter (HGCAL) that will provide unprecedented information on electromagnetic and hadronic showers in the very high pileup of the HL-LHC. In order to employ Si detectors in HGCAL and to address the challenges brought by the intense radiation environment, an extensive R&D program has been initiated, comprising production of prototype sensors of various types, sizes and thicknesses, their qualification before and after irradiation to the expected levels, and accompanying simulation studies. The ongoing investigation presented here includes measurements of current-voltage and capacitance-voltage characteristics, along with predicted charge collection efficiences of the sensors irradiated to levels expected for the HGCAL at HL-LHC. The status of the study and the first results of the performance of neutron irradiated Si detectors, as well as their comparison with numerical simulations, are presented.Comment: 3 pages, 3 figures, 1 table, 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC

Public reactions to utilization of everyman's rights in wild berry business

We investigated attitudes concerning recruiting of foreign wild berry pickers in Finland. The survey was directed for nature-orientated people, as 92 % of respondents (n=495) picked wild berries for household use (80 %) or incomes (12 %)

Complete, Single-Horizon Quantum Corrected Black Hole Spacetime

We show that a semi-classical polymerization of the interior of Schwarzschild black holes gives rise to a tantalizing candidate for a non-singular, single horizon black hole spacetime. The exterior has non-zero quantum stress energy but closely approximates the classical spacetime for macroscopic black holes. The interior exhibits a bounce at a microscopic scale and then expands indefinitely to a Kantowski-Sachs spacetime. Polymerization therefore removes the singularity and produces a scenario reminiscent of past proposals for universe creation via quantum effects inside a black hole.Comment: 5 pages, 2 figures. A shortened version with some new reference

Crossing Probabilities of Multiple Ising Interfaces

We prove that in the scaling limit, the crossing probabilities of multiple interfaces in the critical planar Ising model with alternating boundary conditions are conformally invariant expressions given by the pure partition functions of multiple SLE(\kappa) with \kappa=3. In particular, this identifies the scaling limits with ratios of specific correlation functions of conformal field theory.Comment: 30 pages, 1 figure; v3: removed an appendix & other minor improvement