Time-of-flight measurement of resonant molecular formation in muon-catalyzed dt fusion

Preliminary results are reported for an experiment at TRIUMF where a time-of-flight technique was tested for measuring the energy dependence of the rate for muon-catalyzed dt fusion. Muonic tritium atoms were created following transfer of negative muons from muonic protium in a layer of solid hydrogen (protium) containing a small fraction of tritium. The atoms escaped from the solid layer via the Ramsauer-Townsend mechanism, traversed a drift region of 18 mm, and then struck an adjacent layer of deuterium, where the muonic atom could form a molecular system. The time of detection of a fusion product (neutron or alpha) following muon arrival is dependent upon the energy of the muonic tritium atom as it traverses the drift region. By comparison of the time distribution of fusion events with a prediction based on the theoretical energy dependence of the rate, the strength of resonant formation can in principle be determined. The results extracted so far are discussed and the limitations of the method are examined.     

Density effect in d - d catalyzed fusion with ortho-and para-enriched deuterium

The ortho-para dependence of d-d fusion neutrons time spectra has been investigated using different target densities at similar temperatures. Even at the similar temperatures, the ortho-para effect on the fusion neutron yields in the liquid phase showed the opposite tendency from that in the gas phase. The result evidenced significant density dependence on resonant ddμ formation.     

The equation of state of solid molecular hydrogen and deuterium

Isochores of solid H₂ and D₂ have been measured to 2 kbar. Our results lead to reevaluation of the 4.2 K isotherm of Anderson and Swenson to 25 kbar. The equation of state has been determined, including ortho-para dependence. The pre-melting phase transition cited in recent russian literature has not been detected.     

Measurement of the resonant d(mu)t molecular formation rate in solid HD

Measurements of muon-catalyzed dt fusion ( d(mu)t-->4He + n + mu(-)) in solid HD have been performed. The theory describing the energy dependent resonant molecular formation rate for the reaction (mu)t + HD-->[(d(mu)t)pee](*) is compared to experimental results in a pure solid HD target. Constraints on the rates are inferred through the use of a Monte Carlo model developed specifically for the experiment. From the time-of-flight analysis of fusion events in 16 and 37 microg x cm(-2) targets, an average formation rate consistent with 0.897+/-(0.046)(stat)+/-(0.166)(syst) times the theoretical prediction was obtained.     

Muon-catalyzed fusion and fundamental physics

The essence and main features of muon-catalyzed fusion are exposed. Some important and interesting applications of muon-catalyzed fusion in fundamental physics are presented: nuclear physics, quantum electrodynamics, weak interaction physics, the Coulomb three-body problem and the physics of exotic atoms.     

Discovery of temperature-dependent phenomena of muon-catalyzed fusion in solid deuterium and tritium mixtures

A systematic experimental study on muon-catalyzed fusion was conducted using a series of solid deuterium and tritium mixtures. A variety of conditions were investigated, i.e., tritium concentrations from 20% to 70%, and temperatures from 5 to 16 K. With decreasing temperature, we observed an unexpected decrease in the muon cycling rate (lambda(c)) and an increase in the muon loss probability (W). The origins of these observed changes were interpreted by the temperature-dependence in the dt mu formation process for lambda(c) and that in the muon reactivation process after muon-to-alpha sticking for W.     

Experimental studies of very cold neutrons passing through solid deuterium

The studies of spectral dependences for neutrons passing through solid deuterium were carried out using a vertical beam of very cold neutrons with the wavelength λ～40–150 Å. The results show the dependence of the observed neutron scattering cross sections on the method of preparation of a solid deuterium sample and on the ortho-para composition of deuterium.     

Experimental investigation of muon-catalyzed dt fusion at cryogenic temperatures

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 ≲ 40K. 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)d⁰ for the dtμ molecule formation in collisions of tμ atoms in the lower (F=0) hyperfine state with D₂ 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)d⁰ formation rate. The probability q_1s for dμ atoms to reach the ground state was determined as a function of density and tritium concentration.     

Three-body integral equations and their application to the reactions of muon transfer

Hyperfine Interactions - It is suggested to use the integral Faddeev equations in the Alt-Grassberger-Sandhas form to calculate the muon transfer reactions relevant to muon-catalyzed fusion....     

Calculation of muon fraction stopped in the dt-cell of a 14 MeV neutron generator

The muon utilization efficiency is calculated for a model of a neutron source based on muon-catalyzed fusion, and the intensity and neutron flux are estimated in this system.     

Tritium handling

Hyperfine Interactions - In recent years there has been much research into muon-catalyzed fusion in gas mixtures including tritium. To perform such research it is necessary to construct a...     

Experimental results on muon-catalyzed dt fusion

A comprehensive experimental study of the kinetics of muon-catalyzed dt fusion has been conducted at PSI, based on the measurement of the 14 MeV neutrons from the fusion process. The target conditions included densities from 1–150% of the atomic density of liquid hydrogen, relative tritium concentrations of 2–95%, and temperatures of 13–300 K. Information about the dt cycle has been obtained from the measured neutron time distributions by different methods: Monte Carlo simulations primarily aimed at investigating epithermal effects in molecular formation and the determination and interpretation of cycling rates describing the steady state regime.     

Photostimulated desorption and ortho-para conversion of H2 on Ag surfaces

Photostimulated desorption and change of the ortho-para ratio of H2 physisorbed on Ag at 7 K are reported. After pump laser excitation at 193 nm neutral H2 desorbing in a nonthermal process is state selectively detected by resonance-enhanced multiphoton ionization. At weak pump laser fluence the natural ortho-para conversion of H2 on Ag was monitored to proceed with a conversion time of approximately 780 s, which is in good agreement with predictions based on an electron-exchange-hyperfine-contact model. With increasing pump laser fluence, the ortho-para ratio decreases faster, suggesting photoassisted ortho-para H2 conversion.     

Measuring sticking and stripping in muon-catalyzed dt fusion with multilayer thin films

We propose a direct measurement of muon sticking to alpha particles in muon-catalyzed dt fusion at a high density. Exploiting the features of a multilayer thin-film target developed at TRIUMF, the sticking is determined directly by detection of charged fusion products. Experimental separation of initial sticking and stripping may become possible for the first time. Monte Carlo simulations, as well as preliminary results of test measurements are described.     

New approach to the old problem of muon sticking in µCF

A new approach is presented for evaluation of the muon sticking probability to helium in muon-catalyzed fusion reactions. Use of the sudden approximation is avoided. The probability _s of muon sticking to helium in the reaction dtµ µ⁴He+n, calculated with the new method, agrees with previous results. Moreover, the energy and angular distributions for the emitted muon, as well as the dependence of w_s on the energy radiated during the muon-catalyzed fusion event, have been evaluated.     

Ortho-para transition rate in mu-molecular hydrogen and the proton's induced pseudoscalar coupling gp

We report a measurement of the ortho-para transition rate in the p mu p molecule. The experiment was conducted at TRIUMF via the measurement of the time dependence of the 5.2 MeV neutrons from muon capture in liquid hydrogen. The measurement yielded an ortho-para rate Lambda op = (11.1 +/- 1.7 +/-(0.9)(0.6)) x 10(4) s(-1), which is substantially larger than the earlier result of Bardin et al. The result has striking implications for the proton's induced pseudoscalar coupling g(p), changing the value of g(p) obtained from the most precise ordinary muon capture measurement from 10.6 +/- 2.7 to 0.8 +/- 2.8, and from the sole radiative muon capture measurement from 12.2 +/- 1.1 to 10.6 +/- 1.2, bringing the latter result closer to theoretical predictions.     

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 _c, 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.Invited talk presented by Peter Kammel.     

Ortho-para conversion in CH3F: Self-consistent theoretical model

A complete theoretical model of the nuclear spin conversion in¹³CH₃F induced by intramolecular ortho-para state mixing is proposed. The model contains parameters determined from the levelcrossing spectra of the¹³CH₃F spin conversion. This set of parameters includes the ortho-para decoherence rate, the magnitude of the spin-spin interaction between the molecular nuclei and the energy gap between the mixed ortho and para states. These parameters are found to be in good agreement with their theoretical estimates.     

Coulomb final state interaction in identical Boson interferometry

Recently, the muonic three-body systemdtμ, has aroused considerable attention in relation to the realization of a useful muon-catalyzed fusion [1, 2]. This bound system must be solved up to 6 digits in energy to establish the muon catalyzed fusion process. We applied the ATMS method [3] and the coupled-channel method [4] to the Coulomb three-body system and obtained the detailed information on the energy levels and the wave functions of the bound states. Further we investigated the effect of the nuclear interaction on the fusion rate in the bound states [5] and developed a formalism to calculate the muon sticking to⁴He [6]. In this paper we report the results obtained in our collaborations: Figure 2 shows up our main results.