M. Jeitler

X-RAY EMISSION DURING THE MUONIC CASCADE IN HYDROGEN

We report our investigations of X rays emitted during the muonic cascade in hydrogen employing charge coupled devices as X-ray detectors. The density dependence of the relative X-ray yields for the muonic hydrogen lines (K_alpha, K_beta, K_gamma) has been measured at densities between 0.00115 and 0.97 of liquid hydrogen density. In this density region collisional processes dominate the cascade down to low energy levels. A comparison with recent calculations is given in order to demonstrate the influence of Coulomb deexcitation.

Experimental survey of the sticking problem in muon catalyzed dt fusion

The “sticking” process dtμ → αμ + n, which constitutes the most severe limit to the number of fusions which a muon can catalyze, is reviewed. Many attempts were made to determine by calculations and measurements the probability for initial stickingωs0 (immediately after dtμ fusion) and for final stickingωs (after the αμ came to rest). Previous results based on neutron disappearance rates and on the observation of αμ-X-rays were controversial and also in some disagreement with theory. New data are reported from PSI on direct observation of final sticking, using a setup with the St. Petersburg ionization chamber. These data mark a significant improvement in reliability and may clarify questions concerning previous discrepancies. The new results isωs∼(0.56±0.04)%, lower than the theory predictionωs=(0.65±0.03)%, at medium density.

Experimental investigation of muon-catalyzed dt fusion at cryogenic temperatures

Abstract An experimental investigation of muon-catalyzed fusion ( μCF ) in gaseous, liquid and solid mixtures of deuterium and tritium was performed. The target conditions included the range of densities of 0.03 ≲ φ ≲ 1.5, tritium concentrations of 2% ≲ c t ≲ 90% and temperatures of 13 ≲ T ≲ 40 K . The study was based on the analysis of observed cycling rates extracted from the measured time distributions of the fusion neutrons. For the first time, the density dependence of the rates λ ( dtμ ) d 0 for the dtμ molecule formation in collisions of tμ atoms in the lower (F=0) hyperfine state with D 2 molecules was determined experimentally. Evidence for the proposed effects of below-threshold resonances on molecular formation was found. Measurements at low temperatures in mixtures of different molecular compositions revealed a clear predominance of the λ ( dtμ ) d 0 formation rate. The probability q 1 s for dμ atoms to reach the ground state was determined as a function of density and tritium concentration.

The kinetics of muon-catalyzed dt fusion

A main source of information about the muon-catalyzed fusion cycle in D-T mixtures are the cycling rates λc, which are characteristic for the kinetic equilibrium of states attained rapidly in dense targets. The measurement, analysis and interpretation of these rates will be discussed, concentrating on the extensive set of rates observed at PSI over the last decade in gaseous, liquid and solid targets.

The PSI experiments on muon-catalyzed pt fusion

The experiments on pt fusion performed at Paul Scherrer Institut, Villigen, Switzerland, are described. Liquid triple mixtures of protium, deuterium and tritium with low concentrations on deuterium and tritium were used. Gamma rays, X-rays, neutrons and, for the first time, conversion muons, were measured. Preliminary results are: Rate for spin flip from the triplet to the singlet state of tμ(1s), λ10=(1.0±0.2) × 103μs−1; rate for muon-catalyzed pt fusion from the (I=1) nuclear-spin state, λptf(I=1)=0.07±0.01μs−1; and the molecular formation rate, λptm=(7.5±1.3)μs−1 (all normalized to liquid hydrogen density).

Experimental observation of excited state muon transfer in mixtures of hydrogen isotopes

The first direct measurement ofqls and its dependence on target density and deuterium concentration was performed in H/D (protium/deuterium) mixtures. Charge coupled devices (CCDs) were employed to detect the muonic hydrogen X rays. The presented preliminary results were obtained by determining the relative Kα-yields of both isotopes.

Systematic analysis of the PSI experiment to directly measure the sticking probabilityωs 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 μα 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.

Final dt sticking? s using the ?survived moun method?

A new direct measurement of the final dt sticking probability ωs using a special data analysis called the “survived muon method” is presented. The data were obtained at PSI using a high pressure ionization chamber with H/D/T gas mixtures. The method can provide information on final sticking dμt → μα+n independent of theoretical models of stripping and initial sticking. It was found:ωs=(0.57±0.07±0.02)%. The experiment and the analysis method are discussed in detail.

Hydrogen/deuterium-mixtures as a laboratory for the study of the muonic cascade and muon-catalyzed fusion

We have performed an experiment to investigate various processes induced by muons in hydrogen-deuterium mixtures. Preliminary results are given for cascade X-ray yields, q1s, relative yields of conversion muons and fusion γ-rays, molecular formation and hyperfine transition rates.

Survey of experimental results on μCF including hyperfine effects

Complementary to the investigations of the most efficient dt cycle, also the other muon-induced fusion cycles in mixtures of hydrogen isotopes have been studied. The results of these dedicated experiments provide rich information about muon-induced few-body reactions and contribute significantly to a better overall understanding of μCF. A summary of the recent progress will be presented. Special emphasis will be put on two characteristic examples, namely a new experimental approach to study the muonic cascade in H-D mixtures and the systematic study of hyperfine effects in muon-induced reactions.