Systematic analysis of the PSI experiment to directly measure the sticking probabilityω s in dt fusion

Starting in 1989 an experiment was run at PSI to directly measure the final sticking probability in muon catalyzed dt fusion. This experiment was based on an active-target ionization chamber (IC) built at Gatchina, Russia, and an array of plastic neutron counters. In three runs approximately 5×10⁶ isolated alpha signals were recorded with around one half of these occurring in the inner chamber region where we have more complete understanding of the systematic errors. Particularly from a long run in 1992 we were able to obtain a very clean sticking peak of some 5000 events. However, to reach an accurate value of sticking, all systematic effects and several major backgrounds had to be understood in detail. To this end a Monte Carlo code was written to simulate the full electrostatic environment of the IC and to recreate completely each signal type including the actual tritium decay noise from the live experiment. A slightly model dependent value of approx. 0.56±0.04% is obtained for final sticking.     

Feasibility of an experiment to determine the branching ratio for the emission of a heavy neutrino after muon capture in3He

The triton energy of the muon capture reaction ³He t+v, where ³ He is the ground state of muonic³He, has been measured in order to investigate a possible heavy v admixture into the flavour with high sensitivity. ³ He has been formed via the pd fusion reaction by stopping ^– in an ionization chamber (IC) filled with an H/D gas mixture of 3% D concentration at a pressure of 161 bar. In a first short experiment 650 triton events were observed yielding an upper limit for the -heavy v mixing strength of 2.3×10^–3 atE _0v=60 MeV.     

Measurement of the muon capture rate in hydrogen gas and determination of the proton's pseudoscalar coupling gP

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.     

Ultrasonic wave propagation across a thin nonlinear anisotropic layer between two half-spaces

Boundary conditions and perturbation theory are combined to create a set of equations which, when solved, yield the reflected and transmitted wave forms in the case of a thin layer of material that is perfectly bonded between two isotropic half-spaces. The set of perturbed boundary conditions is created by first using the fully bonded boundary conditions at each of the two interfaces between the thin layer and the half-spaces. Then, by restricting the layer's thickness to be much smaller than an acoustic wavelength, perturbation theory can be used on these two sets of boundary equations, producing a set of equations which effectively treat the thin layer as a single interface via a perturbation term. With this set of equations, the full range of incident and polar angles can be considered, with results general enough to use with a layer that is anisotropic, nonlinear, or both anisotropic and nonlinear. Finally the validity of these equations is discussed, comparing the computer simulation results of this theory to results from standard methods, and looking at cases where the results (or various properties of the results) are known or can be predicted.     

High precision study of muon catalyzed fusion in D2 and HD gas

Muon catalyzed dd fusion in D₂ and HD gases in the temperature range from 28 to 350 K was investigated in a series of experiments based on a time-projection ionization chamber operating with pure hydrogen. All main observables in this reaction chain were measured with high absolute precision including the resonant and non-resonant ddμ formation rates, the rate for hyperfine transitions in dμ atoms, the branching ratio of the two charge symmetric fusion channels ³He + n and t + p and the muon sticking probability. The report presents the final analysis of the data together with a comprehensive comparison with calculations based on recent μCF theories. The energy of the loosely bound ddμ state with quantum numbers J = 1, ν = 1, which is central to the mechanism of resonant molecule formation, is extracted with precision ?₁₁(fit) = ?1.9651(7) eV. in impressive agreement with the latest theoretical results ?₁₁(theory) = ?1.9646 eV.     

Measuring scanning acoustic microscope with a harmonic sounding signal

A concept of a scanning acoustic microscope with a harmonic sounding signal for measuring the parameters of local homogeneous regions of flat samples is proposed. The distinctive feature of the device is the utilization of the Doppler effect that occurs in the sounding wave reflected from the sample surface when the sample is uniformly moved relative to the focusing ultrasonic transducer of the microscope. It is theoretically demonstrated that the spectrum of the received signal is determined by the product of the reflection coefficient and the transfer function of the transducer. The errors of the measurement technique are considered, and the sources of signal distortions are analyzed. High sensitivity of the measurement results to the errors of the scanning system is demonstrated. The developed measuring microscope is described, in which an acoustic interferometer is used to provide the necessary precision of the scanning coordinate measurement. The microscope transfer function is measured for the frequency of the sounding signal 65 MHz, and the values of density and bulk wave velocities are determined for a homogeneous sample by the measured phase of the reflection coefficient using the technique of nonlinear estimation of parameters. With fused quartz used as an example, it is shown that the measurement error is 7.2% for density and 2.3 and 0.7% for the velocities of longitudinal and transverse waves, respectively. In addition, the velocity of a leaky surface wave (SAW) is determined by two methods. One method is based on measuring the position of the inflexion point for the experimental phase of the reflection coefficient, and the other is based on calculating the SAW velocity corresponding to the measured values of density and bulk wave velocities. The errors of these methods are found to be equal to 0.42 and 0.17%, respectively.     

Recovery of LHCb Detector Muon Chambers for Malter Effect Elimination

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% CO2 + 5% CF4 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.     

Precision measurement of nuclear muon capture by3He

In this article we report the results of an experiment performed in 1993 at PSI. The goal was to determine the absolute rate of nuclear muon capture by³He. In the experiment we used a new technique recently developed at Gatchina. As a preliminary result from this experiment we obtained _c=(1496±3(stat)-3(syst)) s^–1.