Atomic-force microscopy methods were used to study specimens of cathodes of multiwire proportional chambers subjected to a long-term exposure to a β-source
90
Sr in the course of laboratory longevity ...tests. The changes in the surface morphology of the copper foil at the detector cathode that have occurred as a result of action of an electron beam have been described. The quantitative estimate and analysis of the evolution of radiation defects depending on the irradiation dose are presented. The similarity of the radiation-induced defects in the laboratory prototypes and in the full-scale proportional chambers after their use for 10 years at the Large Hadron Collider is demonstrated.
The MuCap experiment at the Paul Scherrer Institute has measured the rate Λ(S) of muon capture from the singlet state of the muonic hydrogen atom to a precision of 1%. A muon beam was stopped in a ...time projection chamber filled with 10-bar, ultrapure hydrogen gas. Cylindrical wire chambers and a segmented scintillator barrel detected electrons from muon decay. Λ(S) is determined from the difference between the μ(-) disappearance rate in hydrogen and the free muon decay rate. The result is based on the analysis of 1.2 × 10(10) μ(-) decays, from which we extract the capture rate Λ(S) = (714.9 ± 5.4(stat) ± 5.1(syst)) s(-1) and derive the proton's pseudoscalar coupling g(P)(q(0)(2) = -0.88 m(μ)(2)) = 8.06 ± 0.55.
A method is presented for restoring the performance of gas discharge detectors wherein a spontaneous self-sustaining current, i.e., Malter effect, occurs. A successful practical implementation of the ...method is demonstrated by the example of recovery of operability for multiwire proportional chambers used in the muon detector of the LHCb experiment carried out at the Large Hadron Collider. Four proportional chambers wherein Malter currents regularly occur during the experiment were subjected to high-voltage discharge training in the working gas mixture of 40% Ar + 55% CO
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+ 5% CF
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with 2% of oxygen added. It is shown that, with addition of oxygen, the recovery of the proportional chambers occurs tens of times faster in compare to the training in the working gas mixture. The reconstructed chambers were installed in the LHCb muon detector and have been working in a collider beam experiment for more than two years already.
The mechanism of occurrence of spontaneous self-sustained currents in a multiwire proportional chamber from the experiment at the Large Hadron Collider has been considered. Atomic force microscopy, ...Rutherford backscattering, and Raman spectroscopy on the copper foil of the chamber cathode revealed the formation of nanocarbon structures and their fluorinated compounds, which are well known as low-threshold sources of field emission of electrons.
A comprehensive study is performed of the cathode of a multiwire proportional chamber subjected to prolonged irradiation in an experiment at the LHC. The structural-phase state of the copper foil on ...the cathode is analyzed via nuclear scanning microscopy, atomic scanning microscopy, Raman spectroscopy, and X-ray phase analysis. Nanostructural formations of carbon are found in the zone of spontaneous electron emission on the electrode.
The rate of nuclear muon capture by the proton has been measured using a new technique based on a time projection chamber operating in ultraclean, deuterium-depleted hydrogen gas, which is key to ...avoiding uncertainties from muonic molecule formation. The capture rate from the hyperfine singlet ground state of the microp atom was obtained from the difference between the micro(-) disappearance rate in hydrogen and the world average for the micro(+) decay rate, yielding Lambda(S)=725.0+/-17.4 s(-1), from which the induced pseudoscalar coupling of the nucleon, g(P)(q(2)=-0.88m(2)(micro))=7.3+/-1.1, is extracted.
The situation of Norfolk Island, as a territory of the Commonwealth of Australia, is one of the historical anomalies in governance, which has persisted since 1914. It reflects the direct historical ...linkages between the British Crown and those Norfolk Islanders who were descendants of Pitcairn Islanders of Mutiny on the Bounty fame. Yet, once Federation was in the wind, the British Government, against the expressed wishes of the Norfolk Island community, sought to divest itself of all responsibility for Norfolk Island. There is a curiously ‘Yes Minister’ quality about the negotiations which lead to the final take-over by Australia, and the appointment of the first Commonwealth Administrator of Norfolk Island. The direct involvement of Atlee Hunt, then Secretary of the Department of External Affairs, eventually ensured the appointment of Michael Vincent Murphy. In order to achieve this end, Hunt had to fend off other applicants who were busy ingratiating themselves with the Minister for External Affairs Patrick McMahon Glynn and the then Prime Minister Joseph Cook. This is essentially a study of the relationships between governors, politicians, public servants and community leaders during the years which followed the take-over of Norfolk Island, and of the struggle of one Norfolk Islander, Charles Chase Ray Nobbs, against Australian administrative authority
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