High-concentration Er:YAG single-crystal fibers grown by laser-heated pedestal growth technique

High-concentration Er:YAG single-crystal fibers have been grown using the laser-heated pedestal growth technique. Instability in the melt and concomitant opacity of fibers were observed at source concentrations higher than 15 mol.%. Spectroscopic examination shows that broadening of the linewidth of the I<sub>13/2</sub>4→I<sub>15/2</sub>4 transition is strongly dependent on Er<sup>3+</sup> concentration

Measurement of the 7Be(p, γ)8B reaction cross section at low energies

The absolute total cross section for the reaction 7Be(p, γ)8B has been measured for Ec.m.=117-1230 keV by detecting the delayed α particles following the 8B β decay. Two independent methods have been used to determine the areal density of the 7Be target. The inferred zero-energy S factor from the present experiment is S17(0)=0.0216±0.0025 keV b. This value reduces the predicted 37Cl solar-neutrino capture rate by ∼25%

Absolute cross section for 7Li(d,p)8Li and solar neutrino capture rates

The absolute total cross section for the 7Li(d,p)8Li reaction has been measured between 0.60 and 1.2 MeV by counting the beta-delayed alpha particles from 8Be*. The cross section at the peak of the 0.77-MeV resonance was measured to be 148±12 mb in good agreement with the new measurement of Elwyn et al. but disagreeing with several previous experiments. The effects of changes in this cross section on the calculation of solar neutrino captures rates is discussed

Proton capture cross section of 7Be and the flux of high energy solar neutrinos

The low energy cross section for the 7Be(p, γ)8B reaction has been measured by detecting the delayed α particles from the 8B beta decay. Detailed discussion is presented of the analysis of the radioactive 7Be target including the use of two independent methods to determine the 7Be areal density. The direct capture part of the cross section is subtracted from the total cross section to deduce resonance parameters for the 1+ first excited state in 8B. The zero-energy astrophysical S factor inferred from the present experiment is compared with previous values. The effect on the 37Cl solar neutrino capture rate, predicted by the standard solar model, is also discussed

Green Up-Conversion Laser-Emission In Er-Doped Crystals At Room-Temperature

We report room-temperature pulsed up-conversion laser oscillation in Er-doped LiYF4 and KYF4 at 551 and 562 nm, respectively. In both crystals laser oscillation is observed on the S-4(3/2)-I-4(15/2) ground state transition. Excitation was provided by a tunable flashlamp-pumped Ti:sapphire laser in the spectral region around 810 nm. Additional pumping with a continuous wave krypton ion laser at 647 nm was beneficial to both lasers. Laser action has also been observed in Er-doped Y3Al5O12 on the same transition

Precision planar drift chambers and cradle for the TWIST muon decay spectrometer

To measure the muon decay parameters with high accuracy, we require an array of precision drift detector layers whose relative position is known with very high accuracy. This article describes the design, construction and performance of these detectors in the TWIST (TRIUMF Weak Interaction Symmetry Test) spectrometer.Comment: 44 pages, 16 Postscript figures, LaTeX2e, uses Elsevier class elsart.cls, package graphicx, submitted to Nuclear Instruments & Methods in Physics Researc

Spectroscopy And Green Up-Conversion Laser-Emission Of Er(3+)-Doped Crystals At Room-Temperature

The spectroscopic parameters of Er3+-doped crystals were determined with regard to the upconversion laser parameters of the green transition S-4(3/2) -- \u3e I-4(15/2), The influence of excited-state absorption on this laser channel was determined. Furthermore, upconversion pump mechanisms using ground-state and excited-state absorption around 810 and 970 nm were investigated by direct measurements of excited-state absorption. The spectroscopic results confirm the pulsed room-temperature laser experiments on the S-4(3/2) -- \u3e I-5(5/2) transition. The lasers based on Er:LiYF4, Er:Y3Al5O12, and Er:Lu3Al5O12 were directly excited into the upper laser level by an excimer laser pumped dye laser in the blue spectral range. In Er:LiYF4, Er:KYF4, and Er:Y3Al5O12, laser action was achieved with two-step upconversion pumping by a Ti:sapphire laser and a krypton ion laser. In the case of the fluorides, the additional pumping with the krypton ion laser was not necessary. The laser emission wavelengths were 551 nm for Er:LiYF4, 561 nm for Er:Y3Al5012 and Er:Lu3Al5O12, and 562 nm for Er:KYF4. In addition, green quasi-cw laser emission of Er:LiYF4 pumped with an argon-ion laser was realized at room temperature

Parton energy loss limits and shadowing in Drell-Yan dimuon production

A precise measurement of the ratios of the Drell-Yan cross section per nucleon for an 800 GeV/c proton beam incident on Be, Fe and W targets is reported. The behavior of the Drell-Yan ratios at small target parton momentum fraction is well described by an existing fit to the shadowing observed in deep-inelastic scattering. The cross section ratios as a function of the incident parton momentum fraction set tight limits on the energy loss of quarks passing through a cold nucleus

Neutrino induced transitions between the ground states of the A=12 triad

Neutrino induced reactions on $^{12}$C, an ingredient of liquid scintillators, have been studied in several experiments. We show that for currently available neutrino energies, $E_{\nu} \le$ 300 MeV, calculated exclusive cross sections $^{12}$C$_{gs}(\nu,l)$$^{12}$N$_{gs}$ for both muon and electron neutrinos are essentially model independent, provided the calculations simultaneously describe the rates of several other reactions involving the same states or their isobar analogs. The calculations agree well with the measured cross sections, which can be therefore used to check the normalization of the incident neutrino spectrum and the efficiency of the detector.Comment: 9 pages REVTEX, 2 postscript figures, text and figures available at http://www.krl.caltech.edu/preprints/MAP.htm