•Stable crack propagation of tungsten reinforced with tungsten fibers.•Fracture surface observations.•Using fiber reinforcement improves the fracture toughness of tungsten.•The fracture toughness of ...tungsten fibre-reinforced tungsten composites was investigated with different methods.•Discussion of the applicability of the used methods for tungsten fibre-reinforced tungsten composites.
Tungsten fibre-reinforced tungsten composites (Wf/W) have been developed to overcome the inherent brittleness of tungsten, which is a promising candidate for the plasma-facing material in a future fusion power plant. As the development of Wf/W evolves, the fracture toughness of the composite is in the focus of interest for further component design. In this contribution fracture mechanical tests on two different types of chemical vapour deposited (CVD) Wf/W are presented. Three-point bending tests according to ASTM E399 as a standard method for brittle materials were used to get a first estimation of the toughness. A provisional fracture toughness value of up to 241 MPa m1/2 was calculated for the as-fabricated and of up to 20.5 MPa m1/2 for a heat-treated and thus embrittled state. As the material does not show a brittle fracture in the as-fabricated state, the J-Integral approach based on the ASTM E1820 was additionally applied for this state. A maximum value of the J-integral of 7.5 kJ/m2 (57.6 MPa m1/2) was determined. A detailed post mortem investigations was used to obtain the active mechanisms.
Higgs physics at CMS Holzner, André G.
Hyperfine interactions,
12/2016, Letnik:
237, Številka:
1
Journal Article
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This article reviews recent measurements of the properties of the standard model (SM) Higgs boson using data recorded with the CMS detector at the LHC: its mass, width and couplings to other SM ...particles. We also summarise highlights from searches for new physical phenomena in the Higgs sector as they are proposed in many extensions of the SM: flavour violating and invisible decay modes, resonances decaying into Higgs bosons and searches for additional Higgs bosons.
•Fabrication of tungsten fibre-reinforced tungsten (Wf/W) for divertor applications by a chemical deposition process.•A layered deposition process to produce Wf/W tiles suitable for divertor mock-up ...applications.•Charpy impact tests at room temperature including an estimation of the fracture toughness.•Temperature window for Wf/W and investigation of crack growing resistance by FEM modelling.•Advanced fabrication methods including textile techniques, a new deposition device and infiltration modelling.
The development of advanced materials is essential for sophisticated energy systems like a future fusion reactor. Tungsten fibre-reinforced tungsten composites (Wf/W) utilize extrinsic toughening mechanisms and therefore overcome the intrinsic brittleness of tungsten at low temperature and its sensitivity to operational embrittlement. This material has been successfully produced and tested during the last years and the focus is now put on the technological realisation for the use in plasma facing components of fusion devices. In this contribution, we present a way to utilize Wf/W composites for divertor applications by a fabrication route based on the chemical vapour deposition (CVD) of tungsten. Mock-ups based on the ITER typical design can be realized by the implementation of Wf/W tiles. A concept based on a layered deposition approach allows the production of such tiles in the required geometry. One fibre layer after the other is positioned and ingrown into the W-matrix until the final sample size is reached. Charpy impact tests on these samples showed an increased fracture energy mainly due to the ductile deformation of the tungsten fibres. The use of Wf/W could broaden the operation temperature window of tungsten significantly and mitigate problems of deep cracking occurring typically in cyclic high heat flux loading. Textile techniques are utilized to optimise the tungsten wire positioning and process speed of preform production. A new device dedicated to the chemical deposition of W enhances significantly, the available machine time for processing and optimisation. Modelling shows that good deposition results are achievable by the use of a convectional flow and a directed temperature profile in an infiltration process.
The Large Hadron Collider (LHC) at CERN in Geneva (Switzerland) will go into operation in the coming months and will soon enable us to analyse the highest energy collisions ever produced at an ...accelerator. With a design integrated luminosity of up to 100 fb-1 per year and a centre-of-mass energy of 14 TeV it will not only allow us to probe the Standard Model beyond the TeV scale but also search for new phenomena such as the Higgs boson, supersymmetric particles, extra spatial dimensions etc. This article summarises a few selected analyses which are foreseen to be performed with the first 0.01 to 1 fb-1.
•Development of W-fibre enhanced W-composites incorporating extrinsic toughening mechanisms.•Production of a large sample (more than 2000 long fibres) for mechanical and thermal testing.•Even in a ...fully embrittled state, toughening mechanisms are still effective.•Emissions of volatile W-oxides can be suppressed by alloying W with elements forming stable oxides.•WCr10Ti2 has been successfully tested under accidental conditions and high heat fluxes.
Tungsten is the major candidate material for the armour of plasma facing components in future fusion devices. To overcome the intrinsic brittleness of tungsten, which strongly limits its operational window, a W-fibre enhanced W-composite material (Wf/W) has been developed incorporating extrinsic toughening mechanisms. Small Wf/W samples show a large increase in toughness. Recently, a large sample (50mm×50mm×3mm) with more than 2000 long fibres has been successfully produced allowing further mechanical and thermal testing. It could be shown that even in a fully embrittled state, toughening mechanisms as crack bridging by intact fibres, as well as the energy dissipation by fibre-matrix interface debonding and crack deflection are still effective. A potential problem with the use of pure W in a fusion reactor is the formation of radioactive and highly volatile WO3 compounds and their potential release under accidental conditions. It has been shown that the oxidation of W can be strongly suppressed by alloying with elements forming stable oxides. WCr10Ti2 alloy has been produced on a technical scale and has been successfully tested in the high heat flux test facility GLADIS. Recently, W-Cr-Y alloys have been produced on a lab-scale. They seem to have even improved properties compared to the previously investigated W alloys.
One of the missions of the LEP program was the search for the Standard Model Higgs Boson. The skillful operation of the machine in the year 2000, the final year of operation, has allowed the four ...collaborations ALEPH, DELPHI, L3 and OPAL to collect 536 pb
−1 of data at center-of-mass energies of 206 GeV or higher. This data is used to probe for the existence of the Higgs boson up to a mass of around 115 GeV. Tantalizing candidates have been observed in excess over the Standard Model predictions, but without enough statistical power to claim a discovery. A Higgs boson lighter than 114.4 GeV is hence excluded at 95% confidence level.
In the Standard Model (SM), the weak gauge bosons and fermions acquire mass
through the Higgs mechanism. A lower limit on the SM Higgs mass of 114.4 GeV
was obtained from the direct search at LEP. ...Although a single Higgs doublet is
sufficient to explain the non-zero particle masses while keeping the theory
SU(2) gauge invariant, several extensions to this minimal model were proposed,
to which this limit does not apply. Most of the models discussed here introduce
one additional Higgs doublet and are therefore called Two Higgs doublet models
(2HDM). Several signatures predicted by such models have been searched for at
LEP using data collected at center-of-mass energies up to 209 GeV. All limits
quoted in this report are at 95% confidence level.
Nucl.Phys.Proc.Suppl. 115 (2003) 369-373 One of the missions of the LEP program was the search for the Standard Model
Higgs Boson. The skillful operation of the machine in the year 2000, the final
...year of operation, has allowed the four collaborations ALEPH, DELPHI, L3 and
OPAL to collect 536/pb of data at center-of-mass energies of 206 GeV or higher.
This data is used to probe the existence of the Higgs boson up to a mass of
around 115 GeV. Tantalizing candidates have been observed in excess over the
Standard Model predictions, but without enough statistical power to claim a
discovery. A Higgs boson lighter than 114.4 GeV is hence excluded at 95%
confidence level.
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