Browsing by Subject "RADIATION"

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  • Yang, Qigui; Hu, Zhiwei; Makkonen, Ilja; Desgardin, Pierre; Egger, Werner; Barthe, Marie-France; Olsson, Pär (2022)
    Tungsten is considered to be used in the future fusion reactors as plasma-facing material. In such extreme environments, defects are induced in materials that modify their macroscopic properties such as the mechanical ones. It is of paramount importance to be able to determine concentration and size of the vacancy defects, from the mono vacancy to the large cavities, to validate the models developed to predict the evolution of the microstructure of irradiated materials. Positrons are very useful non-destructive probes that can characterize vacancy-type defects in materials. We present a combined experimental and theoretical study on detecting and estimating the sizes of vacancy clusters that are invisible with electron microscopy in tungsten, using positron annihilation spectroscopy. We here model the positron annihilation in the tungsten lattice and in vacancy-type defects using state-of-the-art first principles methodology. The Doppler broadening spectra and positron lifetimes in tungsten are calculated with two-component density functional theory with local density approximation and weighted density approximation. Our calculations are in excellent agreement with our experimental results. We show that the sizes of vacancy clusters in tungsten can be well estimated by combining both positron lifetimes and Doppler broadening spectra. We also determine the limit of validity of the canonical calculation method, which here is shown to fail when the vacancy clusters grow beyond their nucleation stage. This work is a first step needed to better interpret the measured positron annihilation characteristics (Doppler and lifetime) in tungsten and then extract quantitative data on small vacancy defects required to improve the understanding of early-stage vacancy defect evolution in tungsten. The method used in this paper could be used to study other metallic materials.
  • Purisha, Zenith; Karhula, Sakari S.; Ketola, Juuso H.; Rimpeläinen, Juho; Nieminen, Miika T.; Saarakkala, Simo; Kröger, Heikki; Siltanen, Samuli (2019)
    X-ray tomography is a reliable tool for determining the inner structure of 3-D object with penetrating X-rays. However, traditional reconstruction methods, such as Feldkamp-Davis-Kress (FDK), require dense angular sampling in the data acquisition phase leading to long measurement times, especially in X-ray micro-tomography to obtain high-resolution scans. Acquiring less data using greater angular steps is an obvious way for speeding up the process and avoiding the need to save huge data sets. However, computing 3-D reconstruction from such a sparsely sampled data set is difficult because the measurement data are usually contaminated by errors, and linear measurement models do not contain sufficient information to solve the problem in practice. An automatic regularization method is proposed for robust reconstruction, based on enforcing sparsity in the 3-D shearlet transform domain. The inputs of the algorithm are the projection data and a priori known expected degree of sparsity, denoted as 0 <C-pr
  • Gielen, Bert; Acosta, Manuel; Altimir, Nuria; Buchmann, Nina; Cescatte, Alessandro; Ceschia, Eric; Fleck, Stefan; Hortnagal, Lukas; Klumpp, Katja; Kolari, Pasi; Lohile, Annalea; Loustau, Denis; Maranon-Jimenez, Sara; Manisp, Languy; Matteucci, Giorgio; Merbold, Lutz; Metzger, Christine; Moureaux, Christine; Montagnani, Leonardo; Nilsson, Mats B.; Osborne, Bruce; Papale, Dario; Pavelka, Marian; Saunders, Matthew; Simioni, Guillaume; Soudani, Kamel; Sonnentag, Oliver; Tallec, Tiphaine; Tuittila, Eeva-Stiina; Peichl, Matthias; Pokorny, Radek; Vincke, Caroline; Wohljahrt, Georg (2018)
    The Integrated Carbon Observation System is a Pan-European distributed research infrastructure that has as its main goal to monitor the greenhouse gas balance of Europe. The ecosystem component of Integrated Carbon Observation System consists of a multitude of stations where the net greenhouse gas exchange is monitored continuously by eddy covariance measurements while, in addition many other measurements are carried out that are a key to an understanding of the greenhouse gas balance. Amongst them are the continuous meteorological measurements and a set of non-continuous measurements related to vegetation. The latter include Green Area Index, aboveground biomass and litter biomass. The standardized methodology that is used at the Integrated Carbon Observation System ecosystem stations to monitor these vegetation related variables differs between the ecosystem types that are represented within the network, whereby in this paper we focus on forests, grasslands, croplands and mires. For each of the variables and ecosystems a spatial and temporal sampling design was developed so that the variables can be monitored in a consistent way within the ICOS network. The standardisation of the methodology to collect Green Area Index, above ground biomass and litter biomass and the methods to evaluate the quality of the collected data ensures that all stations within the ICOS ecosystem network produce data sets with small and similar errors, which allows for inter-comparison comparisons across the Integrated Carbon Observation System ecosystem network.
  • Zhu, Xudan; Chen, Liang; Pumpanen, Jukka; Keinänen, Markku; Laudon, Hjalmar; Ojala, Anne; Palviainen, Marjo; Kiirikki, Mikko; Neitola, Kimmo; Berninger, Frank (2021)
    Quantification of dissolved organic carbon (DOC) and iron (Fe) in surface waters is critical for understanding the water quality dynamics, brownification and carbon balance in the northern hemisphere. Especially in the remote areas, sampling and laboratory analysis of DOC and Fe content at a sufficient temporal frequency is difficult. Ultraviolet-visible (UV-Vis) spectrophotometry is a promising tool for water quality monitoring to increase the sampling frequency and applications in remote regions. The aim of this study was (1) to investigate the performance of an in-situ UV-Vis spectrophotometer for detecting spectral absorbances in comparison with a laboratory benchtop instrument; (2) to analyse the stability of DOC and Fe estimates from UV-Vis spectrophotometers among different rivers using multivariate methods; (3) to compare site-specific calibration of models to pooled models and investigate the extrapolation of DOC and Fe predictions from one catchment to another. This study indicates that absorbances that were measured by UV-Vis sensor explained 96% of the absorbance data from the laboratory benchtop instrument. Among the three tested multivariate methods, multiple stepwise regression (MSR) was the best model for both DOC and Fe predictions. Accurate and unbiased models for multiple watersheds for DOC were built successfully, and these models could be extrapolated from one watershed to another even without site-specific calibration for DOC. However, for Fe the combination of different datasets was not possible.
  • Jouhi, Susanna; Heikkonen, Jorma; Reijonen, Vappu; Raivio, Virpi; Täll, Martin; Kivelä, Tero T. (2021)
    Purpose: To compare tumor control, vision, and complications between patients with a choroidal melanoma of Design: Retrospective, comparative case series. Participants: One hundred sixty-four consecutive patients with a choroidal melanoma of Methods: Diagnosis was based on growth or high-risk characteristics. The apical dose was 100 to 120 Gy aiming to deliver >= 250 Gy to the sclera. Plaque positioning was modeled retrospectively. An increase of >= 0.3 mm in thickness and >= 0.5 mm in LBD indicated local recurrence. Outcomes were compared with cumulative incidence analysis and Cox regression. Median follow-up time for patients still alive was 8.4 years. Main Outcome Measures: Recurrence rate, low vision, blindness, radiation maculopathy, and optic neuropathy. Results: Melanomas treated with the 10-mm plaque were smaller (median thickness, 1.9 mm vs. 2.6 mm; LBD, 7.1 mm vs. 8.6 mm) and located closer to foveola (median, 2.0 mm vs. 2.8 mm) than those treated with the 15-mm plaque (P <0.001). The 2 plaques provided a safety margin in 43% versus 40% eyes, provided no safety margin to guard foveola in 17% versus 33%, and did not entirely cover tumor mainly close to the disc in 32% versus 18% of eyes, respectively (P = 0.052). The incidence of a local recurrence was comparable (13% vs. 15% at 10 years; P = 0.31) and associated with plaque positioning (hazard ratio [HR], 2.81 for no safety margin; P = 0.041). At 5 years, the incidence of low vision was 14% versus 24%, and that of blindness was 3% versus 6%. Distance to the foveola was associated with loss of both levels of vision (HR, 0.65 per 1 mm vs. 0.68 per 1 mm; P Conclusions: The 10-mm ruthenium plaque contributes to better visual preservation, particularly with tumors close to fovea, without increase in local recurrence rate, and may therefore be preferable to the 15-mm plaque. (C) 2020 by the American Academy of Ophthalmology
  • Kröger, Björn (2018)
    Near-equatorial peak diversities are a prominent first-order feature of today's latitudinal diversity gradient (LDG), but were not a persistent pattern throughout geological time. In an analysis of Ordovician (485-444 Ma) fossil occurrences, an equatorward shift of the latitudinal diversity peak can be detected. A modern-type LDG and out-of-the-tropics range shift pattern were synchronously established during emerging icehouse conditions at the climax of the Great Ordovician Biodiversity Event. The changes in the LDG pattern and range shift trends can be best explained as a consequence of global cooling during the Middle Ordovician and of diversification in the tropical realm following a greenhouse period with temperatures too hot to support diverse tropical marine life. These results substantiate a fundamental role of temperature changes in establishing global first-order diversity patterns.
  • Vihma, Timo; Kilpeläinen, Tiina; Manninen, Miina; Sjöblom, Anna; Jakobson, Erko; Palo, Timo; Jaagus, Jaak; Maturilli, Marion (2011)
  • Kainulainen, Kimmo; Leskinen, Juuso; Nurmi, Sami; Takahashi, Tomo (2017)
    We investigate the CMB mu distortion in models where two uncorrelated sources contribute to primordial perturbations. We parameterise each source by an amplitude, tilt, running and running of the running. We perform a detailed analysis of the distribution signal as function of the model parameters, highlighting the differences compared to single-source models. As a specific example, we also investigate the mixed inflaton-curvaton scenario. We find that the mu distortion could efficiently break degeneracies of curvaton parameters especially when combined with future sensitivity of probing the tensor-to-scalar ratio r. For example, assuming bounds mu <0.5 x 10(-8) and r <0.01, the curvaton contribution should either vanish or the curvaton should dominate primordial perturbations and its slow-roll parameter eta(chi) is constrained to the interval -0.007 <eta(chi) <0.045.
  • Saarikko, Anne; Mellanen, Eero; Kuusela, Linda; Leikola, Junnu; Karppinen, Atte; Autti, Taina; Virtanen, Pekka; Brandstack, Nina (2020)
    Summary Purpose Black Bone (BB) magnetic resonance imaging (MRI) is a nonionizing imaging method and a recent alternative to computed tomography (CT) in the examination of cranial deformities. The purpose of this study was to compare BB-MRI and routine 3D-CT in the preoperative evaluation of patients with craniosynostosis. Methods At our center, we have routinely performed preoperative CT of the skull and brain MRI for patients with clinical suspicion of craniosynostosis. We recently changed our MRI protocol into one that includes sequences for the evaluation of both brain anatomy and skull bone and sutures by BB-MRI. A semi-automatic skull segmentation algorithm was developed to facilitate visualization. Both BB-MRI and 3D-CT were performed on 9 patients with clinical craniosynostosis, and the images were evaluated by two craniofacial surgeons, one pediatric neurosurgeon, and two neuroradiologists. Results We obtained informative 3D images using BB-MRI. Six (6/9) patients had scaphocephaly, 1 (1/9) patient had unicoronal synostosis, and 2 (2/9) patients had lambdoid synostosis. The affected synostotic sutures could be identified both by BB-MRI and by 3D-CT in all patients. Intra-rater and inter-rater reliability for rating the calvarial sutures was high. However, the reliability for rating the intracranial impressions was low by both imaging methods. Conclusion BB-MRI is an alternative to 3D-CT in the preoperative evaluation of patients with craniosynostosis. BB-MRI provides information not only on cranial sutures and intracranial impressions but also on the brain structure in one imaging session. This method can replace ionizing radiation-based methods in analyzing skull deformities.
  • Sporre, Moa K.; O'Connor, Ewan J.; Håkansson, Nina; Thoss, Anke; Swietlicki, Erik; Petäjä, Tuukka (2016)
    Cloud retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard the satellites Terra and Aqua and the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard the Suomi-NPP satellite are evaluated using a combination of ground-based instruments providing vertical profiles of clouds. The ground-based measurements are obtained from the Atmospheric Radiation Measurement (ARM) programme mobile facility, which was deployed in Hyytiala, Finland, between February and September 2014 for the Biogenic Aerosols - Effects on Clouds and Climate (BAECC) campaign. The satellite cloud parameters cloud top height (CTH) and liquid water path (LWP) are compared with ground-based CTH obtained from a cloud mask created using lidar and radar data and LWP acquired from a multi-channel microwave radiometer. Clouds from all altitudes in the atmosphere are investigated. The clouds are diagnosed as single or multiple layer using the ground-based cloud mask. For single-layer clouds, satellites overestimated CTH by 326 (14 %) on average. When including multilayer clouds, satellites underestimated CTH by on average 169 m (5.8 %). MODIS collection 6 overestimated LWP by on average 13 g m(-2) (11 %). Interestingly, LWP for MODIS collection 5.1 is slightly overestimated by Aqua (4.56 %) but is underestimated by Terra (14.3 %). This underestimation may be attributed to a known issue with a drift in the reflectance bands of the MODIS instrument on Terra. This evaluation indicates that the satellite cloud parameters selected show reasonable agreement with their ground-based counterparts over Finland, with minimal influence from the large solar zenith angle experienced by the satellites in this high-latitude location.
  • von Weissenberg, Ella; Jansson, Anna; Vuori, Kristiina A.; Engström-Öst, Jonna (2022)
    The marine ecosystems are under severe climate change-induced stress globally. The Baltic Sea is especially vulnerable to ongoing changes, such as warming. The aim of this study was to measure eco-physiological responses of a key copepod species to elevated temperature in an experiment, and by collecting field samples in the western Gulf of Finland. The potential trade-off between reproductive output and oxidative balance in copepods during thermal stress was studied by incubating female Acartia sp. for reproduction rate and oxidative stress measurements in ambient and elevated temperatures. Our field observations show that the glutathione cycle had a clear response in increasing stress and possibly had an important role in preventing oxidative damage: Lipid peroxidation and ratio of reduced and oxidized glutathione were negatively correlated throughout the study. Moreover, glutathione-s-transferase activated in late July when the sea water temperature was exceptionally high and Acartia sp. experienced high oxidative stress. The combined effect of a heatwave, increased cyanobacteria, and decreased dinoflagellate abundance may have caused larger variability in reproductive output in the field. An increase of 7 degrees C had a negative effect on egg production rate in the experiment. However, the effect on reproduction was relatively small, implying that Acartia sp. can tolerate warming at least within the temperature range of 9-16 degrees C. However, our data from the experiment suggest a link between reproductive success and oxidative stress during warming, shown as a significant combined effect of temperature and catalase on egg production rate.
  • Djurabekova, F.; Fridlund, C.; Nordlund, K. (2020)
    We present molecular dynamics simulations of atomic mixing over a Si/SiO2 heterostructure interface, induced by focused Ne+ and broad Si(+ )ion-beam irradiations, using a speed-up scheme that significantly reduces the relaxation time of the cascading recoils. To assess the qualitative reliance of the chosen method, two different potential models for Si-O, Si-Si, and O-O interactions were used: the Stillinger-Weber-like Watanabe-Samela potential and the Tersoff-like Munetoh potential. Furthermore, the molecular dynamics simulations were assessed by simulating a similar case, at a total fluence of 1 x10(15) cm(-2), with the binary collision approximation. The same general atomic density profile distributions were achieved with both models; however, the binary collision approach showed shallower penetration of Si into the SiO(2 )layer. Coordination analysis of the molecular dynamics results provides strong evidence that ion mixing at high fluences leads to coordination defects, which will affect the electronic properties of the structures unless removed with annealing.
  • Andritsch, Elisabeth; Beishon, Marc; Bielack, Stefan; Bonvalot, Sylvie; Casali, Paolo; Crul, Mirjam; Delgado-Bolton, Roberto; Donatih, Davide Maria; Douis, Hassan; Haas, Rick; Hogendoorn, Pancras; Kozhaeva, Olga; Lavender, Verna; Lovey, Jozsef; Negrouk, Anastassia; Pereira, Philippe; Roca, Pierre; de Lempdes, Godelieve Rochette; Saarto, Tiina; van Berck, Bert; Vassal, Gilles; Wartenberg, Markus; Yared, Wendy; Costa, Alberto; Naredi, Peter (2017)
    Background: ECCO essential requirements for quality cancer care (ERQCC) are checklists and explanations of organisation and actions that are necessary to give high-quality care to patients who have a specific tumour type. They are written by European experts representing all disciplines involved in cancer care. ERQCC papers give oncology teams, patients, policymakers and managers an overview of the elements needed in any healthcare system to provide high quality of care throughout the patient journey. References are made to clinical guidelines and other resources where appropriate, and the focus is on care in Europe. Sarcoma: essential requirements for quality care Sarcomas - which can be classified into soft tissue and bone sarcomas - are rare, but all rare cancers make up more than 20% of cancers in Europe, and there are substantial inequalities in access to high-quality care. Sarcomas, of which there are many subtypes, comprise a particularly complex and demanding challenge for healthcare systems and providers. This paper presents essential requirements for quality cancer care of soft tissue sarcomas in adults and bone sarcomas. High-quality care must only be carried out in specialised sarcoma centres (including paediatric cancer centres) which have both a core multidisciplinary team and an extended team of allied professionals, and which are subject to quality and audit procedures. Access to such units is far from universal in all European countries. It is essential that, to meet European aspirations for high-quality comprehensive cancer control, healthcare organisations implement the requirements in this paper, paying particular attention to multidisciplinarity and patient-centred pathways from diagnosis and follow-up, to treatment, to improve survival and quality of life for patients. Conclusion: Taken together, the information presented in this paper provides a comprehensive description of the essential requirements for establishing a high-quality service for soft tissue sarcomas in adults and bone sarcomas. The ECCO expert group is aware that it is not possible to propose a 'one size fits all' system for all countries, but urges that access to multidisciplinary teams is guaranteed to all patients with sarcoma. (C) 2016 The Authors. Published by Elsevier Ireland Ltd.
  • Harju, Jorma; Pineda, Jaime E.; Vasyunin, Anton; Caselli, Paola; Offner, Stella S. R.; Goodman, Alyssa A.; Juvela, Mika; Sipilä, Olli; Faure, Alexandre; Le Gal, Romane; Hily-Blant, Pierre; Alves, Joao; Bizzocchi, Luca; Burkert, Andreas; Chen, Hope; Friesen, Rachel K.; Guesten, Rolf; Myers, Philip C.; Punanova, Anna; Rist, Claire; Rosolowsky, Erik; Schlemmer, Stephan; Shirley, Yancy; Spezzano, Silvia; Vastel, Charlotte; Wiesenfeld, Laurent (2020)
    We present Atacama Large Millimeter/submillimeter Array maps of the starless molecular cloud core Ophiuchus/H-MM1 in the lines of deuterated ammonia (ortho-NH2D), methanol (CH3OH), and sulfur monoxide (SO). The dense core is seen in NH2D emission, whereas the CH3OH and SO distributions form a halo surrounding the core. Because methanol is formed on grain surfaces, its emission highlights regions where desorption from grains is particularly efficient. Methanol and sulfur monoxide are most abundant in a narrow zone that follows the eastern side of the core. This side is sheltered from the stronger external radiation field coming from the west. We show that photodissociation on the illuminated side can give rise to an asymmetric methanol distribution but that the stark contrast observed in H-MM1 is hard to explain without assuming enhanced desorption on the shaded side. The region of the brightest emission has a wavy structure that rolls up at one end. This is the signature of Kelvin-Helmholtz instability occurring in sheared flows. We suggest that in this zone, methanol and sulfur are released as a result of grain-grain collisions induced by shear vorticity.
  • Kirschenmann, S.; Bharthuar, S.; Brücken, E.; Golovleva, M.; Gädda, A.; Kalliokoski, M.; Luukka, P.; Ott, J.; Winkler, A. (2021)
    While Cadmium Telluride (CdTe) excels in terms of photon radiation absorption properties and outperforms silicon (Si) in this respect, the crystal growth, characterization and processing into a radiation detector is much more complicated. Additionally, large concentrations of extended crystallographic defects, such as grain boundaries, twins, and tellurium (Te) inclusions, vary from crystal to crystal and can reduce the spectroscopic performance of the processed detector. A quality assessment of the material prior to the complex fabrication process is therefore crucial. To locate the Te-defects, we scan the crystals with infrared microscopy (IRM) in different layers, obtaining a 3D view of the defect distribution. This provides us with important information on the defect density and locations of Te inclusions, and thus a handle to assess the quality of the material. For the classification of defects in the large amount of IRM image data, a convolutional neural network is employed. From the post-processed and analysed IRM data, 3D defect maps of the CdTe crystals are created, which make different patterns of defect agglomerations inside the crystals visible. In total, more than 100 crystals were scanned with the current IRM setup. In this paper, we compare two crystal batches, each consisting of 12 samples. We find significant differences in the defect distributions of the crystals.
  • Lindholm, C.; Pekkarinen, A.; Sipilä, O.; Manninen, A. -L.; Lehtinen, M.; Siiskonen, T. (2020)
    The eye lens exposure among 16 technicians in two nuclear medicine departments at university hospitals in Finland was investigated by measuring the operational quantity H-p(3) using EYE-D dosemeters. For all workers, the annual mean H-p(3) was estimated to be 1.1 mSv (max. 3.9 mSv). The relation between H-p(3) to routinely monitored personal dose equivalent H-p(10) was clearly correlated. Considering individual dose measurement periods (2-4 weeks), the H-p(3)/H-p(10) ratio was 0.7 (Pearson's coefficient r = 0.90, p <0.001, variation of ratio 0.1-2.3). The variation decreased considerably with increasing H-p(10) (sigma(2) = 0.04 vs. 0.43 for H-p(10) > 0.1 mSv vs. <0.1 mSv, respectively), i.e. higher Hp(10) predicts H-p(3) more reliably. Moreover, annual H-p(10) data from national dose register during 2009-2018 were used to derive the annual H-p(3) applying the H-p(3)/H-p(10) ratio. The data from Finnish nuclear medicine departments imply that routine measurements of H-p(3) among nuclear medicine technicians are not justified.
  • CORE Collaboration; Melin, J. -B.; Kiiveri, K.; Kurki-Suonio, H.; Lindholm, V.; Väliviita, J. (2018)
    We examine the cosmological constraints that can be achieved with a galaxy cluster survey with the future CORE space mission. Using realistic simulations of the millimeter sky, produced with the latest version of the Planck Sky Model, we characterize the CORE cluster catalogues as a function of the main mission performance parameters. We pay particular attention to telescope size, key to improved angular resolution, and discuss the comparison and the complementarity of CORE with ambitious future ground-based CMB experiments that could be deployed in the next decade. A possible CORE mission concept with a 150 cm diameter primary mirror can detect of the order of 50,000 clusters through the thermal Sunyaev-Zeldovich effect (SZE). The total yield increases (decreases) by 25% when increasing (decreasing) the mirror diameter by 30 cm. The 150 cm telescope configuration will detect the most massive clusters (> 10(14) M-circle dot) at redshift z > 1.5 over the whole sky, although the exact number above this redshift is tied to the uncertain evolution of the cluster SZE flux-mass relation; assuming self-similar evolution, CORE will detect similar to 500 clusters at redshift z > 1.5. This changes to 800 (200) when increasing (decreasing) the mirror size by 30 cm. CORE will be able to measure individual cluster halo masses through lensing of the cosmic microwave background anisotropies with a 1-sigma sensitivity of 4 x 10(14)M(circle dot), for a 120 cm aperture telescope, and 10(14)M(circle dot) for a 180 cm one. From the ground, we estimate that, for example, a survey with about 150,000 detectors at the focus of 350 cm telescopes observing 65% of the sky would be shallower than CORE and detect about 11,000 clusters, while a survey with the same number of detectors observing 25% of sky with a 10 m telescope is expected to be deeper and to detect about 70,000 clusters. When combined with the latter, CORE would reach a limiting mass of M-500 similar to 2-3 x 10(13)M(circle dot) and detect 220,000 clusters (5 sigma detection limit). Cosmological constraints from CORE cluster counts alone are competitive with other scheduled large scale structure surveys in the 2020's for measuring the dark energy equation of-state parameters w(0) and w(a) (sigma(w0) = 0.28, sigma(wa) = 0.31). In combination with primary CMB constraints, CORE cluster counts can further reduce these error bars on w(0) and w(a) to 0.05 and 0.13 respectively, and constrain the sum of the neutrino masses, Sigma m(nu), to 39 meV (1 sigma). The wide frequency coverage of CORE, 60-600 GHz, will enable measurement of the relativistic thermal SZE by stacking clusters. Contamination by dust emission from the clusters, however, makes constraining the temperature of the intracluster medium difficult. The kinetic SZE pairwise momentum will be extracted with S/N = 70 in the foreground cleaned CMB map. Measurements of T-CMB (z) using CORE clusters will establish competitive constraints on the evolution of the CMB temperature: (1 + z)(1-beta), with an uncertainty of sigma(beta) less than or similar to 2.7 x 10(-3) at low redshift (z less than or similar to 1). The wide frequency coverage also enables clean extraction of a map of the diffuse SZE signal over the sky, substantially reducing contamination by foregrounds compared to the Planck SZE map extraction. Our analysis of the one-dimensional distribution of Compton-y values in the simulated map finds an order of magnitude improvement in constraints on sigma(8) over the Planck result, demonstrating the potential of this cosmological probe with CORE.
  • CORE Collaboration; Challinor, A.; Kiiveri, K.; Kurki-Suonio, H.; Lindholm, V.; Väliviita, J. (2018)
    Lensing of the cosmic microwave background (CMB) is now a well-developed probe of the clustering of the large-scale mass distribution over a broad range of redshifts. By exploiting the non-Gaussian imprints of lensing in the polarization of the CMB, the CORE mission will allow production of a clean map of the lensing deflections over nearly the full-sky. The number of high-SAN modes in this map will exceed current CMB lensing maps by a factor of 40, and the measurement will be sample-variance limited on all scales where linear theory is valid. Here, we summarise this mission product and discuss the science that will follow from its power spectrum and the cross-correlation with other clustering data. For example, the summed mass of neutrinos will be determined to an accuracy of 17 meV combining CORE lensing and CMB two-point information with contemporaneous measurements of the baryon acoustic oscillation feature in the clustering of galaxies, three times smaller than the minimum total mass allowed by neutrino oscillation measurements. Lensing has applications across many other science goals of CORE, including the search for B-mode polarization from primordial gravitational waves. Here, lens-induced B-modes will dominate over instrument noise, limiting constraints on the power spectrum amplitude of primordial gravitational waves. With lensing reconstructed by CORE, one can "delens" the observed polarization internally, reducing the lensing B-mode power by 60 %. This can be improved to 70 % by combining lensing and measurements of the cosmic infrared background from CORE, leading to an improvement of a factor of 2.5 in the error on the amplitude of primordial gravitational waves compared to no delensing (in the null hypothesis of no primordial B-modes). Lensing measurements from CORE will allow calibration of the halo masses of the tens of thousands of galaxy clusters that it will find, with constraints dominated by the clean polarization-based estimators. The 19 frequency channels proposed for CORE will allow accurate removal of Galactic emission from CMB maps. We present initial findings that show that residual Galactic foreground contamination will not be a significant source of bias for lensing power spectrum measurements with CORE.
  • Morosan, Diana E.; Räsänen, Juska E.; Kumari, Anshu; Kilpua, Emilia K. J.; Bisi, Mario M.; Dabrowski, Bartosz; Krankowski, Andrzej; Magdalenic, Jasmina; Mann, Gottfried; Rothkaehl, Hanna; Vocks, Christian; Zucca, Pietro (2022)
    The Sun is an active star that often produces numerous bursts of electromagnetic radiation at radio wavelengths. Low frequency radio bursts have recently been brought back to light with the advancement of novel radio interferometers. However, their polarisation properties have not yet been explored in detail, especially with the Low Frequency Array (LOFAR), due to difficulties in calibrating the data and accounting for instrumental leakage. Here, using a unique method to correct the polarisation observations, we explore the circular polarisation of different sub-types of solar type III radio bursts and a type I noise storm observed with LOFAR, which occurred during March-April 2019. We analysed six individual radio bursts from two different dates. We present the first Stokes V low frequency images of the Sun with LOFAR in tied-array mode observations. We find that the degree of circular polarisation for each of the selected bursts increases with frequency for fundamental emission, while this trend is either not clear or absent for harmonic emission. The type III bursts studied, that are part of a long-lasting type III storm, can have different senses of circular polarisation, occur at different locations and have different propagation directions. This indicates that the type III bursts forming a classical type III storm do not necessarily have a common origin, but instead they indicate the existence of multiple, possibly unrelated acceleration processes originating from solar minimum active regions.
  • Mattila, K.; Lehtinen, K.; Väisänen, P.; von Appen-Schnur, G.; Leinert, Ch. (2017)
    We present the method and observations for the measurement of the Extragalactic Background Light (EBL) utilizing the shadowing effect of a dark cloud. We measure the surface brightness difference between the opaque cloud core and its unobscured surroundings. In the difference the large atmospheric and Zodiacal light components are eliminated and the only remaining foreground component is the scattered starlight from the cloud itself. Although much smaller, its separation is the key problem in the method. For its separation we use spectroscopy. While the scattered starlight has the characteristic Fraunhofer lines and 400 nm discontinuity, the EBL spectrum is smooth and without these features. Medium resolution spectrophotometry at lambda = 380-580 nm was performed with VLT/FORS at ESO of the surface brightness in and around the high-galactic-latitude dark cloud Lynds 1642. Besides the spectrum for the core with AV greater than or similar to 15 mag, further spectra were obtained for intermediate-opacity cloud positions. They are used as proxy for the spectrum of the impinging starlight spectrum and to facilitate the separation of the scattered starlight (cf. Paper II; Mattila et al.). Our spectra reach a precision of less than or similar to 0.5 x 10(-9) erg cm(-2) s(-1) sr(-1) angstrom(-1) as required to measure an EBL intensity in range of similar to 1 to a few times 10(-9) erg cm(-2) s(-1) sr(-1) angstrom(-1). Because all surface brightness components are measured using the same equipment, the method does not require unusually high absolute calibration accuracy, a condition that has been a problem for some previous EBL projects.