MICE: The muon ionization cooling experiment. Step I: First measurement of emittance with particle physics detectors

Copyright @ 2011 APSThe Muon Ionization Cooling Experiment (MICE) is a strategic R&D project intended to demonstrate the only practical solution to providing high brilliance beams necessary for a neutrino factory or muon collider. MICE is under development at the Rutherford Appleton Laboratory (RAL) in the United Kingdom. It comprises a dedicated beamline to generate a range of input muon emittances and momenta, with time-of-flight and Cherenkov detectors to ensure a pure muon beam. The emittance of the incoming beam will be measured in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in Liquid Hydrogen (LH2) absorbers to RF cavity acceleration. A second spectrometer, identical to the first, and a second muon identification system will measure the outgoing emittance. In the 2010 run at RAL the muon beamline and most detectors were fully commissioned and a first measurement of the emittance of the muon beam with particle physics (time-of-flight) detectors was performed. The analysis of these data was recently completed and is discussed in this paper. Future steps for MICE, where beam emittance and emittance reduction (cooling) are to be measured with greater accuracy, are also presented.This work was supported by NSF grant PHY-0842798

Inclusive V0V^0 Production Cross Sections from 920 GeV Fixed Target Proton-Nucleus Collisions

Inclusive differential cross sections $d\sigma_{pA}/dx_F$ and $d\sigma_{pA}/dp_t^2$ for the production of \kzeros, \lambdazero, and \antilambda particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to $\sqrt {s} = 41.6$ GeV in the proton-nucleon system. The ratios of differential cross sections \rklpa and \rllpa are measured to be $6.2\pm 0.5$ and $0.66\pm 0.07$, respectively, for \xf $\approx-0.06$. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions $d\sigma_{pA}/dp_t^2$ also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections $\sigma_{pA}$ on the atomic mass $A$ of the target material is discussed, and the deduced cross sections per nucleon $\sigma_{pN}$ are compared with results obtained at other energies.Comment: 17 pages, 7 figures, 5 table

Electron-muon ranger: performance in the MICE muon beam

The Muon Ionization Cooling Experiment (MICE) will perform a detailed study of ionization cooling to evaluate the feasibility of the technique. To carry out this program, MICE requires an efficient particle-identification (PID) system to identify muons. The Electron-Muon Ranger (EMR) is a fully-active tracking-calorimeter that forms part of the PID system and tags muons that traverse the cooling channel without decaying. The detector is capable of identifying electrons with an efficiency of 98.6%, providing a purity for the MICE beam that exceeds 99.8%. The EMR also proved to be a powerful tool for the reconstruction of muon momenta in the range 100–280 MeV/c

Electron-muon ranger: performance in the MICE muon beam

The Muon Ionization Cooling Experiment (MICE) will perform a detailed study of ionization cooling to evaluate the feasibility of the technique. To carry out this program, MICE requires an efficient particle-identification (PID) system to identify muons. The Electron-Muon Ranger (EMR) is a fully-active tracking-calorimeter that forms part of the PID system and tags muons that traverse the cooling channel without decaying. The detector is capable of identifying electrons with an efficiency of 98.6%, providing a purity for the MICE beam that exceeds 99.8%. The EMR also proved to be a powerful tool for the reconstruction of muon momenta in the range 100–280 MeV/c

Fluorination of mercury-based high-temperature superconductors

There are numerous reports of cationic substitutions on the mercurocuprate very high-temperature superconductors of general formula HgBa2Can-1CunO2n+2+δ. Such investigations have been carried out in an attempt to mimic, within chemical substitution at room pressure, the spectacular effect of external pressure, which has raised the superconducting transition temperature, Tc, to record-high values above 160 K. In the present work, we report the post-synthetic incorporation of elemental fluorine as an interstitial anion into the first five congeners of the mercurocuprate family of superconductors. The effect of fluorine incorporation by this route appears to mimic the more usual oxygenation process in giving maximum Tc values of 96, 128 and 135 K for the single, double and triple CuO2-layer materials, respectively, while the Tc of the five CuO2-layer compound are increased to an extent only previously observed by high-pressure oxygenation. We comment upon a derived linear correlation of Tc with the crystal a-lattice parameter and compare this behaviour against that of high-pressure studies. Interestingly, it appears that intrinsic 'chemical factors' dictating the average copper oxidation state have the more marked effect upon Tc than the application of external hydrostatic pressure. © 1997 Elsevier Science B.V

Fluorination of underdoped mercurocuprate superconductors

We present the results of a study into the incorporation of fluorine into the mercurocuprate superconductors. In all cases, the effect of fluorination has been to increase the Tc of underdoped superconductors to the maxima reported. This has important ramifications for the role of the interstitial oxygen in the mercurocuprate superconductors. To assist us in our study, we have, additionally, developed a novel synthetic procedure for preparing HgBa2CuO4+δ in a highly underdoped state. Remarkably, this material shows an increase in Tc, upon fluorination, of 60K! © 1998 Plenum Publishing Corporation

The replacement of [HgO2](2-) by the tetrahedral sulfate anion [SO4](2-) in the Hg-1201 superconductor

The possibility of existence of a Hg1-xSxBa2CuO4+2x+δ solid solution [(Hg, S)-1201] was studied at 18 kbar and 920°C. Monophasic samples were obtained in the range 0.00 ≤ x ≤ 0.15, where the unit cell parameters were found to vary from a = 3.8685(1) Å, c = 9.4667(2) Å for x = 0.00 to a = 3.9010(1) Å and c = 9.3048(6) Å for x = 0.15. Samples with x ≥ 0.20 were polyphasic and the unit cell parameters of the [(Hg, S)-1201] phases were found to vary up to a = 3.9072(1) Å, c = 9.2654(5) Å for a nominal composition x = 0.30. The as-prepared phases with 0.00 ≤ x ≤ 0.05 were found to be nonsuperconducting due to overdoping, while superconductivity appeared at x = 0.10 (Tc,onset = 40 K). Tc increases with the amount of sulfate substitution due to the decrease of the average copper valence. For the annealed samples, the variation is opposite to that found for the as-prepared samples, Tc,onset being higher for the sulfur-free phase. Rietveld refinements of neutron powder diffraction data has determined ≈18% of the HgO2- 2 dumbbells to be substituted by SO2- 4 groups. In this structure the SO2- 4 anion adopts an average S-O bond length that is slightly higher than those in BaSO4. © 1996 Academic Press, Inc

Gold substitution in mercury cuprate superconductors

By using the high-pressure high-temperature technique, we succeeded in substituting in the mercury cuprate superconductors up to about 40% of mercury by gold. The samples were studied by X-ray and neutron powder diffraction, electron microscopy, energy dispersive spectroscopy. AC suceptibility measurements were also performed. The experimental data obtained for the Au substituted Hg-1223 compound indicate that the substitution leads to overdoping of the CuO2 layers, with a progressive decrease of cell parameters and Tc with increasing gold content. Taking into account these results, we used gold substitution to increase Tc of a Hg-1245 sample up to 110 K. The corresponding unsubstituted samples are normally obtained by the high-pressure high-temperature technique in an underdoped state with a Tc around 100 K

Synthesis, neutron diffraction study and cation substitutions in Srn-1Cun+1O2n (n=3,5)

The n = 3 and n = 5 members of the homologous series Srn-1,Cun+1O2n have been synthesised by a high-pressure, high-temperature technique and characterized by X-ray powder diffraction and electron microscopy as well as EDS microanalysis. The solubility range of Sr4-xNdxCu6O10 solid solution was found to be <0.1. The crystal structure of Sr4Cu6O10 was refined from neutron powder diffraction data