Overcoming High Energy Backgrounds at Pulsed Spallation Sources

Instrument backgrounds at neutron scattering facilities directly affect the quality and the efficiency of the scientific measurements that users perform. Part of the background at pulsed spallation neutron sources is caused by, and time-correlated with, the emission of high energy particles when the proton beam strikes the spallation target. This prompt pulse ultimately produces a signal, which can be highly problematic for a subset of instruments and measurements due to the time-correlated properties, and different to that from reactor sources. Measurements of this background have been made at both SNS (ORNL, Oak Ridge, TN, USA) and SINQ (PSI, Villigen, Switzerland). The background levels were generally found to be low compared to natural background. However, very low intensities of high-energy particles have been found to be detrimental to instrument performance in some conditions. Given that instrument performance is typically characterised by S/N, improvements in backgrounds can both improve instrument performance whilst at the same time delivering significant cost savings. A systematic holistic approach is suggested in this contribution to increase the effectiveness of this. Instrument performance should subsequently benefit.Comment: 12 pages, 8 figures. Proceedings of ICANS XXI (International Collaboration on Advanced Neutron Sources), Mito, Japan. 201

Neutron Position Sensitive Detectors for the ESS

The European Spallation Source (ESS) in Lund, Sweden will become the world's leading neutron source for the study of materials. The instruments are being selected from conceptual proposals submitted by groups from around Europe. These instruments present numerous challenges for detector technology in the absence of the availability of Helium-3, which is the default choice for detectors for instruments built until today and due to the extreme rates expected across the ESS instrument suite. Additionally a new generation of source requires a new generation of detector technologies to fully exploit the opportunities that this source provides. The detectors will be sourced from partners across Europe through numerous in-kind arrangements; a process that is somewhat novel for the neutron scattering community. This contribution presents briefly the current status of detectors for the ESS, and outlines the timeline to completion. For a conjectured instrument suite based upon instruments recommended for construction, a recently updated snapshot of the current expected detector requirements is presented. A strategy outline as to how these requirements might be tackled by novel detector developments is shown. In terms of future developments for the neutron community, synergies should be sought with other disciples, as recognized by various recent initiatives in Europe, in the context of the fundamentally multi-disciplinary nature of detectors. This strategy has at its basis the in-kind and collaborative partnerships necessary to be able to produce optimally performant detectors that allow the ESS instruments to be world-leading. This foresees and encourages a high level of collaboration and interdependence at its core, and rather than each group being all-rounders in every technology, the further development of centres of excellence across Europe for particular technologies and niches.Comment: 8 pages, 1 figure. Proceedings from the 23rd International Workshop on Vertex Detectors, 15-19 September 2014, Macha Lake, The Czech Republic. PoS(Vertex2014)02

ZrTiO4 materials obtained by Spark Plasma Reaction Sintering

Zirconium titanate (ZrTiO4), have many attractive properties such as high resistivity, high dielectric constant, high permittivity at microwave frequencies and excellent temperature stability for microwave properties. Zirconium titanate dense materials are proposed for many structural applications, but fully reacted and completely dense pieces are difficult to obtain by conventional routes. In this work, fully dense zirconium titanate materials ( 98%) were obtained at lower temperatures (1300 1400 C) and short processing time by non-conventional technique; spark plasma-reaction sintering (SPRS). Homogeneous and stable starting powders mixture with the adequate composition was prepared from the raw materials: m-ZrO2 ( 0.3 lm) and anatase-TiO2 ( 40 nm). Dense materials were mechanically and microstructural characterised. The fracture strength was measured by biaxial testing, giving values of about 200 MPa.This study has been supported by the Spanish Ministry of Science and Innovation MAT2009-14144-C03-02, MAT2012-38364-C03-02 and MAT2012-31090. A. Borrell, acknowledges the Spanish Ministry of Science and Innovation for her Juan de la Cierva contract (JCI-2011-10498) and the Generalitat Valenciana for the BEST/2012/302 grant and the financial support for ACOMP/2012/166.Borrell Tomás, MA.; Salvador Moya, MD.; García-Rocha, V.; Fernández, A.; Gómez, A.; López-López, E.; Moreno, R. (2014). ZrTiO4 materials obtained by Spark Plasma Reaction Sintering. Composites Part B: Engineering. 56:330-335. https://doi.org/10.1016/j.compositesb.2013.08.046S3303355

Cobalt and precious metals in sulphides of peridotite xenoliths and inferences concerning their distribution according to geodynamic environment: A case study from the Scottish lithospheric mantle

Abundances of precious metals and cobalt in the lithospheric mantle are typically obtained by bulk geochemical analyses of mantle xenoliths. These elements are strongly chalcophile and the mineralogy, texture and trace element composition of sulphide phases in such samples must be considered. In this study we assess the mineralogy, textures and trace element compositions of sulphides in spinel lherzolites from four Scottish lithospheric terranes, which provide an ideal testing ground to examine the variability of sulphides and their precious metal endowments according to terrane age and geodynamic environment. Specifically we test differences in sulphide composition from Archaean-Palaeoproterozoic cratonic sub-continental lithospheric mantle (SCLM) in northern terranes vs. Palaeozoic lithospheric mantle in southern terranes, as divided by the Great Glen Fault (GGF). Cobalt is consistently elevated in sulphides from Palaeozoic terranes (south of the GGF) with Co concentrations > 2.9 wt.% and Co/Ni ratios > 0.048 (chondrite). In contrast, sulphides from Archaean cratonic terranes (north of the GGF) have low abundances of Co (< 3600 ppm) and low Co/Ni ratios (< 0.030). The causes for Co enrichment remain unclear, but we highlight that globally significant Co mineralisation is associated with ophiolites (e.g., Bou Azzer, Morocco and Outokumpu, Finland) or in oceanic peridotite-floored settings at slow-spreading ridges. Thus we suggest an oceanic affinity for the Co enrichment in the southern terranes of Scotland, likely directly related to the subduction of Co-enriched oceanic crust during the Caledonian Orogeny. Further, we identify a distinction between Pt/Pd ratio across the GGF, such that sulphides in the cratonic SCLM have Pt/Pd ≥ chondrite whilst Palaeozoic sulphides have Pt/Pd < chondrite. We observe that Pt-rich sulphides with discrete Pt-minerals (e.g., PtS) are associated with carbonate and phosphates in two xenolith suites north of the GGF. This three-way immiscibility (carbonate-sulphide-phosphate) indicates carbonatitic metasomatism is responsible for Pt-enrichment in this (marginal) cratonic setting. These Co and Pt-enrichments may fundamentally reflect the geodynamic setting of cratonic vs. non-cratonic lithospheric terranes and offer potential tools to facilitate geochemical mapping of the lithospheric mantle

NASH limits anti-tumour surveillance in immunotherapy-treated HCC.

Hepatocellular carcinoma (HCC) can have viral or non-viral causes1-5. Non-alcoholic steatohepatitis (NASH) is an important driver of HCC. Immunotherapy has been approved for treating HCC, but biomarker-based stratification of patients for optimal response to therapy is an unmet need6,7. Here we report the progressive accumulation of exhausted, unconventionally activated CD8+PD1+ T cells in NASH-affected livers. In preclinical models of NASH-induced HCC, therapeutic immunotherapy targeted at programmed death-1 (PD1) expanded activated CD8+PD1+ T cells within tumours but did not lead to tumour regression, which indicates that tumour immune surveillance was impaired. When given prophylactically, anti-PD1 treatment led to an increase in the incidence of NASH-HCC and in the number and size of tumour nodules, which correlated with increased hepatic CD8+PD1+CXCR6+, TOX+, and TNF+ T cells. The increase in HCC triggered by anti-PD1 treatment was prevented by depletion of CD8+ T cells or TNF neutralization, suggesting that CD8+ T cells help to induce NASH-HCC, rather than invigorating or executing immune surveillance. We found similar phenotypic and functional profiles in hepatic CD8+PD1+ T cells from humans with NAFLD or NASH. A meta-analysis of three randomized phase III clinical trials that tested inhibitors of PDL1 (programmed death-ligand 1) or PD1 in more than 1,600 patients with advanced HCC revealed that immune therapy did not improve survival in patients with non-viral HCC. In two additional cohorts, patients with NASH-driven HCC who received anti-PD1 or anti-PDL1 treatment showed reduced overall survival compared to patients with other aetiologies. Collectively, these data show that non-viral HCC, and particularly NASH-HCC, might be less responsive to immunotherapy, probably owing to NASH-related aberrant T cell activation causing tissue damage that leads to impaired immune surveillance. Our data provide a rationale for stratification of patients with HCC according to underlying aetiology in studies of immunotherapy as a primary or adjuvant treatment

The European spallation source and future opportunities for materials science

The European Spallation Source is Europe's next generation high-power neutron source utilising a linear accelerator and a rotating tungsten target to produce neutrons that will be used for fundamental research and industrial applications. The facility is co-hosted by the states of Denmark and Sweden, and while the main site will be placed in Lund, Sweden, the Data Management and Software Centre will be located in Copenhagen, Denmark. The facility will cover a broad range of scientific applications in the fields of physics, chemistry, biology, or life sciences. A focus will also be materials science and engineering, and dedicated instruments will gradually become available to the user community once neutrons will be produced neutrons from 2019 onwards