The measurement method and results measuring of the stopping power ratio of helium-3 and deuterium atoms for muons slowed down in the D/3He mixture are presented. Measurements were performed at four values of pure 3He gas target densities, φ_He = 0.0337, 0.0355, 0.0359, 0.0363 (normalized to the liquid hydrogen density) and at a density 0.0585 of the D/3He mixture. The experiment was carried out at PSI muon beam μE4 with the momentum Pμ= 34.0 MeV/c. The measured value of the mean stopping ratio S_^3He/D is 1.66 +- 0.04.

Stopping power ratio of helium-3 and deuterium atoms for muons slowed down in the D/3He mixture was measured using 34.0 MeV/c muon beam at PSI meson factory. Four 3He targets with different gas densities and one D/3He target with helium atomic comcentration c = 0.05 were used. We present the measurement method and the analysis of experimental data. The measured value of the mean stopping ratio S_He/D is 1.66 +- 0.04.

The final results of the μCF kinetics experimental study in solid hydrogen-deuterium mixtures at temperature 3K are presented. The experiment E742 has been carried out on the meson facility TRIUMF (Canada). The simultaneous analysis of the measured time distributions of pdμ molecule allowed to extract the values of the μCF chain parameters in H-D mixture: the fusion partial rates for different nuclear spin states of the pdμ molecule and the pdμ molecule formation rate.

Methods and results of the two independent cycles of experiments performed at the meson factory TRIUMF (Canada) and PSI (Switzerland) and aimed at studying the μ-atomic and μ-molecular processes are reviewed. Application of the time-of-flight method and the solid hydrogen isotope mixture targets (H-D and H-T) at temperature 3 K in the TRIUMF experiments allowed obtaining for the first time a number of very important parameters of the muonic processes occuring in these mixtures. In PSI experiment the rate of the nuclear fusion in dμ³He has been measured for the first time.

We present the final results of an experimental study of μd and mu t atom scattering in solid hydrogen cooled to 3 K. Strong effects resulting from the Ramsauer-Townsend effect have been observed in the TRIUMF experiment E742 where muons were stopped in thin frozen layers of hydrogen. The measured Ramsauer-Townsend minimum energy for both mu d and mu t atoms and the minimum cross section are in agreement with theory.

The measurement method and measuring results of the stopping power ratio of helium-3 and deuterium atoms for muons slowed down in the D/³He mixture are presented. Measurements were performed at four values of pure ³He gas target densities, &phi_He = 0.0337, 0.0355, 0.0359, 0.0363 (normalized to the liquid hydrogen density) and at a density 0.0585 of the D/³He mixture. The experiment was carried out at PSI muon beam μ E4 with the momentum P_μ =34.0 MeV/c. The measured value of the mean stopping ratio S_^3He/D is 1.66 (+-0.04). This value can also be interpreted as the value of mean reduced ratio of probabilities for muon capture by helium-3 and deuterium atoms.

An experimental study of the nuclear fusion reaction in the charge-asymmetrical dμ ^3He complex ( dμ³He -> &alpha ( 3.5 MeV) + p ( 14.64 MeV)) is presented. The 14.64 MeV protons were detected by three pairs of Si(dE-E) telescopes placed around the cryogenic target filled with D₂ + ³He gas at 34 K. The 6.85 keV gamma rays emitted during the de-excitation of the dμ ^3He complex were detected by a germanium detector. The measurements were performed at two D_2 + ^3He target densities, &phi = 0.0585 and &phi = 0.168 ( relative to liquid hydrogen density) with an atomic concentration of ^3He equal 0.0496. The values of the effective rate of nuclear fusion in dμ³He were obtained for the first time: λ_f = ( 4.5(- 2.0)(+2.6)) ×10⁵ s^-1 (&phi = 0.0585); &lambda_f = (6.9(- 3.0)(+3-6))×10⁵ s^-1 (&phi = 0.168). The J = 0 nuclear fusion rate in dμ ^3He was derived: &lambda_f(J=0) = (9.7(- 2.6)(+5.7))×10^5 s^-1 (&phi = 0.0585); &lambda_f(J=0) = (12.4(-5.4)(+6.5))×10^5 s^-1 (&phi = 0.168).

A project of an experiment on measurement of the cross sections of radiative thermal neutron capture by He-3 nuclei with production of one and two gamma quanta is presented.

This paper presents an analysis procedure for experimental data using theoretical functions generated by Monte Carlo. Applying the classical chi(2) fitting procedure for multiparameter systems is in some cases extremely difficult due to a lack of an analytical expression for the theoretical functions describing the system, The proposed algorithm is based on the least square method using a grid of Monte Carlo generated functions each corresponding to definite values of the minimization parameters. It is used for the E742 experiment (TRIUMF. Vancouver, Canada) data analysis with the aim to extract muonic atom scattering parameters on solid hydrogen.

We present experimental results of μ -atomic and μ -molecular processes induced by negative muons in pure helium and heliumdeuterium mixtures. The experiment was performed at the Paul Scherrer Institute (Switzerland). We measured relative intensities of muonic x-ray K series transitions in (μ ^3,4He)^* atoms in pure helium as well as in helium - deuterium mixtures. The dμ³He radiative decay probabilities for two different helium densities in D₂+He-3 mixture were also determined. Finally, the q_1s(He) probability for a dμ atom formed in an excited state to reach the ground state was measured and compared with theoretical calculations using a simple cascade model.

The results are presented of the investigation of the designed gating circuits to operate the photomultipliers work of the scintillation detectors in electromagnetic and nuclear radiation powerful pulsed fields. Here are considered two variants of high-voltage dividers (HVD) PMT: a resistive and a transistor ones. The experimental data are actual for the wide range of experiments with the essential suppression of the scintillation detector intensive background load during the time interval of ”useful” events detection. The designated gating PMT circuits could be succesfully used while studying rare processes at a high-intensity background process level.

The paper describes an experiment aimed at studying muon capture by 3He nuclei in pure 3He and D₂+3He mixtures at various densities. Energy distributions of protons and deuterons produced are measured for the energy intervals 10-49 MeV and 13-49 MeV, respectively. Muon capture rates are obtained using two different analysis methods. The experimental differential capture rates are compared with theoretical calculations performed using the plane-wave impulse approximation with the realistic nearest-neighbor interaction Bonn B potential. Extrapolation to the full energy range yields total proton and deuteron capture rates in good agreement with former results

We present the results of experimental and theoretical study of the scattering of low-energy pμ atoms in solid hydrogen cooled to 3 K. Strong effects resulting from the solid state interactions have been observed in the TRIUMF experiment E742 where muons were stopped in thin frozen layers of hydrogen. The resulting emission of low-energy p μ atoms from the hydrogen layer into the adjacent vacuum was much higher than that predicted by calculations which ignored the solid nature of the hydrogen. New differential scattering cross sections have been calculated for the collisions of pμ atoms on solid hydrogen to account for its quantum crystalline nature. Analysis of the experimental data performed using such cross sections shows the important role of the coherent scattering in pμ atom diffusion. For pμ energies lower than the Bragg cutoff limit ( approximately=2 meV) the elastic Bragg scattering vanishes which makes the total scattering cross section fall by several orders of magnitude, and thus the hydrogen target becomes transparent allowing the emission of cold pμ atoms to occur. (53 References).

The TRIUMF E742 experiment has measured the energy dependence of the scattering cross-sections of muonic deuterium and tritium on hydrogen molecules for collisions in the energy range 0.1-45 eV. The experimental setup permits the creation of muonic atom ( dμ or tμ) beams. The multilayered target system gives the possibility to choose the type of interactions to study and to isolate a particular interaction. The scattering of dμ or tμ beams on H₂ is analyzed via the muon transfer reaction to neon. The time-of-flight method is used to measure the scattering cross section as a function of the energy of the muonic atom beam. The results are compared, using Monte Carlo simulations, with theoretical calculations which have been recently performed with high accuracy. (19 References).

The vast majority of muon catalyzed fusion research has been concerned with muonic molecules of hydrogen isotopes only, since the dynamics of higher-Z muonic atoms in general preclude the formation of molecular systems. In the specific case of hydrogen-helium mixtures, bound muonic molecular states can exist, and thus it is possible to search for the reaction dμ ³He -> μ + &alpha (3.66 MeV) + p (14.64 MeV). Until recently, the theoretical predictions for the nuclear fusion rate in the dμ ³He molecule, &lambda_f , ranged over one order of magnitude, from 10⁵ to 10⁶ per second. An experimental upper limit has been measured for &lambda_f in HD + 3He giving a value < 6×10⁴ s^-1. We report on the analysis of an experiment in D₂ + 3He which has shown a signal coming either from the muon catalyzed reaction, or from the fusion in flight of 3He's formed from dμ d fusion. (7 References).

Resonant scattering of muonic hydrogen atoms via back decay of the molecular complex, a key process in the understanding of epithermal muonic molecular formation, is analyzed. The limitations of the effective rate approximation are discussed and the importance of the explicit treatment of the back decay is stressed. An expression of the energy distribution for the back-decayed atoms is given. (13 References).

We present the study of pμ atom scattering in solid hydrogen. Anomalously large emission of E_pμ <=1.9 meV pμ 's from a solid H₂ layer was observed for the first time. This three times greater pμ atom yield is due to non-elastic phonon scattering. As a result, it becomes possible to generate an ultracold flux of pμ atoms. The recent calculations of the total and differential cross sections agree with all experimental results of pμ atom scattering in solid hydrogen. (11 References).

Abstract: missing

Resonant formation of d μ t molecules in collisions of muonic tritium ( tμ) on D₂ was investigated using a beam of tμ atoms, demonstrating a new direct approach in muon catalyzed fusion studies. Strong epithermal resonances in d μ t formation were directly revealed for the first time. From the time-of-flight analysis of 2036+-116 dt fusion events, a formation rate consistent with 0.73+-(0.16) _meas+-(009)_model times the theoretical prediction was obtained. For the largest peak at a resonance energy of 0.423+-0.037 eV, this corresponds to a rate of (7.1+-1.8)*10⁹ s^-1, more than an order of magnitude larger than those at low energies. (26 References).

Abstract: missing

Strong solid state effects in low energy scattering of pμ atoms in solid hydrogen are reported and analyzed. Such effects have been observed in TRIUMF experiment E742 where muons are stopped in thin frozen (3 K) layers of hydrogen. Emission of low energy pμ atoms from the hydrogen layer into adjacent vacuum was much higher than expected, based on calculations which ignored the solid nature of hydrogen. Monte Carlo simulations, performed using the scattering cross-sections with solid state effects taken into account, show the important role of the coherent elastic Bragg scattering in the diffusion of pμ atoms. For pμ energies lower than the Bragg cut-off limit (˜2 meV) the total scattering cross-section falls by several orders of magnitude, the hydrogen target becomes transparent and the emission of cold pμ atoms takes place. (20 References).

Abstract: missing

After the June 1998 approval of our Proposal R-98-02, we imptoved our experimental set up with new detectors, a new data acquisition system and more complex electronics. New Monte Carlo simulations have been performed and the results give a better understanding of different parameters such as detector efficiencies, muon stopping distribution and energy losses in our detectors. Detais about the changes, the status of the ongoing analysis as well as plans for the foreseen 1999 run period are presented and discussed here.

Abstract: missing

The project presents an experimental programme on the study of fusion of light nuclei (H, He, Li, Be) in charge-nonsymmetric muonic molecules HeHμ, LiHμ, BeHμ (H is p, d, t). The project describes techniques, conditions of experiments on the study of nuclear fusion reactions in muonic molecules ^3,4HeHμ, ^6,7LiHμ. There are also limiting estimations of nuclear fusion rates, which can be obtained in the experiments. For this experimental programme the intensive muon beams are required.

The results of multi-level adiabatic calculations for the muon transfer rates in mesic atom ground states are presented for all hydrogen isotopes. The influence of the molecular structure and electron shell of hydrogen molecules on the processes has been taken into consideration. A comparison with previous theoretical data and experiments is reported. (26 References).

The results of previous theoretical investigations of the mesic atomic collision processes pμ + p, dμ + d and tμ + t are presented. The cross sections of these processes are obtained for energies from 0.005 eV up to tens of eV, where elastic scattering and spin-flip may occur. The calculations have been performed in the adiabatic representation of the three-body problem. The adiabatic expansion was so truncated that 52 components of the discrete spectrum and several hundred components of the continuous spectrum of the adiabatic basis were used. The mesic atomic cross sections on `bare` nuclei and corresponding phase shifts have been used as the input data for estimating the role of electron screening and molecular effects in the slowing down process of mesic atoms in the mixture where catalysis takes place. Applications of the obtained results to interpret the experimental data are discussed. (30 References).

The three-body problem is classical in both classical and quantum mechanics. In this latter framework, several approaches have been developped (variational calculations, Fadeev method, adiabatic representation for instance). In this work we focus our attention to the very special case where dominated force is the Coulomb interaction, and the continuous spectrum is investigated.

The authors present results for elastic scattering of pμ and tμ mesic atoms in ortho and para states on hydrogen and tritium corresponding to nuclei in the energy range interesting for muon catalyzed fusion experiments. The calculations are performed in the framework of the adiabatic representation of the three-body problem, with several hundreds of basis wave functions taken into account. (15 References).

The authors investigate the asymptotic behaviour of the wave function of a three-particle Coulomb system (a, b, c; M/sub a/[right angle bracket]or=M/sub b/[right angle bracket]m/sub c/) in the adiabatic representation. They evaluate the effect of the basis truncation on its asymptotic dependence on the slow variable R (the coordinate of relative motion of nuclei a and b) in the region of break-up of the three-body system into subsystems (ac)/sub 1s/+b and a+(bc)/sub 1s/. A procedure for taking into account the truncation of the basis is presented, which is shown to converge in the case of the scattering problem. (9 References).

The authors present results for spin flip processes in muonic atoms. The calculations are performed in the framework of the adiabatic representation of the three-body Coulomb problem. The contribution of back decay is taken into account and comparison with available experimental data is reported. (13 References).

The elastic and inelastic cross sections for the processes p mu +p, d mu +d and t mu +t are calculated in a collision energy range 0.005[left angle bracket]or=E[left angle bracket]or=50 eV. In the calculations the adiabatic representation method for the Coulomb three-body problem was used. The results are given in tables and figures. (17 References).

We determined the parameters of the processes of penetration and diffusion of the hydrogen isotopes through the superalloy EI698 the 600 - 1050 K in the range at pressures up to 100 MPa. It was shown that the penetrating flux is in proportional to the pressure square root in the 0.1 - 100 MPa pressure range. The diffusion coefficient of hydrogen (deuterium) does not depend on the concentration of the dissolved hydrogen (deuterium) that attains a value of 1.3·10⁶ cm³/(cm³Me) at a pressure of 100 MPa and a temperature of 1050 K. The concentration of the dissolved hydrogen is not critical with respect to hydrogen-embrittlement of the EI698 alloy subjected to loading for a period of 600 h under an internal pressure of 100 MPa. Based on the obtained values of the penetration rates of hydrogen and deuterium through the EI698 alloy, the decrease in the quantity of the gas in the vessel can be taken into account properly when carrying out experimental studies on the processes of mu-catalysis.

The authors present the calculation of spin flip rates for a wide range of temperatures in the case of (d mu )-d, (p mu )-p and (t mu )-t collisions. The calculations have been performed in the framework of the adiabatic representation of the three-body problem. (11 References).

Cross sections for mesic atomic processes have been calculated: elastic scattering of dμ and tμ mesic atoms on nuclei, isotope exchange and spin-flip, at different CMS collision energies.[5 

Cross sections have been calculated for elastic scattering of deuterium mesic atoms in ortho and para states on deuterium nuclei in the 0-50 eV energy range; cross sections for spin-flip have also been calculated. The calculations have been performed in the adiabatic representation where the initial problem of slow collisions in a three-body system is reduced to the multichannel scattering problem. The temperature dependence of the ortho-para transition rate lambda /sub hf/(T) for d mu atoms is obtained for a deuterium target. The calculated rate 37.2*10/sup 6/ s/sup -1/ (at 30K) is in good agreement with the recent experimental value, lambda /sub exp/(30K)=(37.0+or-0.74)*10/sup 6/ s/sup -1/ (Vienna-SIN group, 1983). (11 References).

Use of a large-volume NE-213 scintillator for investigations of the mechanism of the nuclear synthesis reaction ttμ -> ⁴He + 2n + μ is discussed. The investigations are supposed to be performed by comparison of the measured amplitude distributions of registered neutrons with the calculated neutron distributions obtained for an assumed form of the matrix element of the reaction.

Construction of the liquid tritium target with temperature variation in the range 20.6 t T t 40K is described. The target is designated for the investigations of μ -atom and μ -molecular processes in liquid tritium. Test measurements show the temperature stability of +-0.2 K during the long (300 - 400 h) experimental runs.

The Monte Carlo method is used to establish the properties and feasibility of a large volume NE213 scintillator as an efficient neutron detector. The recoil proton spectra, calculated efficiencies for different detection thresholds and scintillator sizes are presented for neutron energies up to 15 MeV. The time characteristics, e.g. time resolution, are discussed. It is also shown that no strong influence of light attenuation by the scintillator itself on the calculated efficiencies is observed when the gamma-calibration technique is used. A detector volume of approximately 100 1 is suggested for application in investigations of mu -atom and mu -molecular processes. (20 References).

Summary form only given. Cross sections of the mesic atoms p mu , d mu and t mu in the ground state scattered on the nuclei of hydrogen isotopes p, d and t are calculated in the scattering energy range 10/sup -3/-2 eV. The cross sections of elastic scattering, isotope exchange and spin-flip processes are considered and their energy dependence is evaluated. The adiabatic representation in the three-body problem is used in which the problem is reduced to solving the multichannel scattering problem. The algorithm provides an accuracy [left angle bracket]or approximately=5%, which is sufficient for describing the kinetics of muon catalyzed fusion. (3 References).

Summary form only given. The design of the liquid tritium target for the experimental investigation of the muon-catalysed nuclear fusion t+t to /sup 4/He+2n is described. The temperature of liquid tritium in the target can be varied between 20.6 and 40K. Tritium cooling and temperature stabilization are secured by liquid or gaseous hydrogen at varying pressures which itself is cooled by liquid hydrogen at atmospheric pressure. The system of target filling and tritium removal is also presented. The activity of tritium for which the system is designed is 8.5*10/sup 4/ Ci. (3 References).

The system of target filling and tritium removal is presented. The activity of tritium for which the system is designed is 8.5*10⁴ Ci.

Formulae describing the kinetics of muon-catalysed fusion t+t to /sup 4/He+2n in pure tritium are analysed with the aim of establishing optimum conditions for the experimental investigation of tt mu -fusion. It is shown that to determine the parameters characterizing tt mu -fusion in an experiment with a pure tritium target data have to be taken at different target densities. The range of variation of target density required to cover the region of parameter values predicted theoretically is determined. In particular, it is shown that temperature variation of the density of liquid tritium in a rather small range above the temperature of liquid hydrogen (20.4K) is sufficient in this kind of experiment. (13 References).

Neutron registration efficiency in experiments on muon-catalysed fusion reaction tt mu to /sup 4/He+2n+ mu /sup -/ and dt mu to 4He+n+ mu - is calculated. The dependence of light output response of the detectors on energy threshold of the registration apparatus is obtained. For fusion reaction in the tt mu molecule the values of registration efficiency are determined for several types of final-state interaction between the reaction products. (18 References).

The formulae describing the separate cycles of muon catalysed nuclear synthesis of hydrogen isotopes in a one-component medium (pure deuterium or tritium) are derived and discussed. (9 References).

Summary form only given. Kinetic formulae are derived describing the evolution in time of the processes leading to the muon-catalyzed nuclear synthesis in pure D/sub 2/ or T/sub 2/ targets containing possible admixtures of heavier elements. The formulae enable one to take into account any mu -molecular and mu -atomic processes in the muon-catalysis chain, and describe the time distributions of these processes in separate cycles with inclusion of the experimental detection efficiency. (2 References).