Mesic molecules formation in solid deuterium

An explanation is suggested for the fast ddμ formation rate observed in solid deuterium. This revised version was published online in August 2006 with corrections to the Cover Date.     

Tritium gas handling system for muon catalyzed fusion research at RIKEN-RAL muon facility

For muon catalyzed fusion (μCF) experiments at RIKEN-RAL muon facility, a tritium gas handling system for a high purity D–T target, free from ³ component, has been constructed to perform precise measurements of α-sticking probability in the μCF cycle. The system has been constructed to enable us to purify the target D–T gas by removing ³He component, to adjust the D/T mixing ratio, and to measure the hydrogen isotope components at the experiment site. The whole performance has been confirmed and a tritium gas with the inventory of 56 TBq (1500 Ci) has been operated in the system. This revised version was published online in August 2006 with corrections to the Cover Date.     

X-ray measurement on muon to alpha sticking in muon catalyzed d-t fusion; present and future

Among a series of X-ray experiments on the muon catalyzed fusion (CF) carried out by using pulsed muons at UTMSL/KEK, a direct knowledge of -sticking probability ( _s) in CF of high density D-T mixture with high T concentration has been obtained by measuring a characteristic muonic X-ray from the () atoms (central energy of 8.2 keV with a correct Doppler broadening). Combining with the recent X-ray measurements in (d) to³He and⁴He impurities, new insight is now obtained for the detailed background structure in the X-ray spectrum, suggesting the future direction for the X-ray measurements.     

Fuel breeding in a hybrid muon catalyzed fusion reactor

We discuss the processes of nuclear fuel burnup and plutonium breeding in the uranium blanket of a hybrid mesocatalytic reactor. The time dependence of the nuclear fuel isotopic concentrations was calculated by the BURNFL code. Using a three-dimensional Monte Carlo MORSE-H code the plutonium and tritium breeding coefficients, the fission rates of uranium and plutonium and a specific power distribution in the blanket were computed. The total fusion energy multiplication factor was obtained as a function of the fuel residence time using results of a detailed calculation of the mesocatalytic channel and estimations of the electronuclear channel.     

Statistical study of the muon catalyzed d-t fusion cycle

In this paper we discuss the statistics of the main branch species of the muon catalyzed d-t fusion. From a master equation we derive and numerically solve kinetic equations for the average density and the covariances of a system composed of muons, muonic deuterium and muonic tritium atoms, muon molecular d-t ions, muonic helium, helium and neutrons. The system consists of an initial fixed amount of muons in a 50–50% D₂ + T₂ mixture without any external muon source. It is known that the probability distribution function of the population species with the exception of the neutron and helium follow a multinomial distribution function.     

Resonant formation of d&mgr;t molecules in deuterium: An atomic beam measurement of muon catalyzed dt fusion

Resonant formation of d&mgr;t molecules in collisions of muonic tritium ( &mgr;t) on D2 was investigated using a beam of &mgr;t atoms, demonstrating a new direct approach in muon catalyzed fusion studies. Strong epithermal resonances in d&mgr;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)+/-(0.09)(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)x10(9) s(-1), more than an order of magnitude larger than those at low energies.     

Experimental detection and investigation of muon catalyzed fusion of deuterium and tritium

Measurement of the neutron yield of the reaction $\text{dt}\text{μ →}{}^4\text{He}\text{+ μ}{}^{\mathrm{?}}\text{+ 17.6}\text{MeV}$, induced by negative muons in a mixture of gaseous D₂ and T₂, has shown that the rate of muon transfer from deuterium to tritium is λ_dt = (2.7 ± 0.9) × 10⁸s^?1 and that the lower limit of the formation rate of dt_μ molecules is λ_dtμ > 10⁸s^?1.     

Facility for preparation of gas mixture in muon catalyzed fusion experiments

A facility is described that allows safe handling of high tritium gas activity as dozens kilocuries in a regular laboratory environment. It is used to make and deliver into the target a mixture of specific isotopic composition with the contamination requirement of 10^-7 v.f. for Z>1 elements, and recover it upon completion of operation. With this facility, efforts have been accomplished to investigate into the muon catalyzed fusion on two targets – liquid tritium and high-pressure tritium types. Also, the operation range was 0.1–120 MPa for pressure and 20–800 K for temperature and the amount of tritium used was about 100 kCi. The facility showed reliability in operation without indications of radiation beyond the safety level. This revised version was published online in August 2006 with corrections to the Cover Date.     

Experimental survey of the sticking problem in muon catalyzed dt fusion

The sticking process dt + 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 sticking _s ⁰ (immediately after dt fusion) and for final sticking _s (after the came to rest). Previous results based on neutron disappearance rates and on the observation of -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 is _s(0.56±0.04)%, lower than the theory prediction _s=(0.65±0.03)%, at medium density.     

Method of determination of muon catalyzed fusion parameters in H-T mixture

A method for measurement of the muon catalyzed fusion parameters CF in the H-T mixture is proposed. The kinetics of the mu-atomic and mu-molecular processes preceding the pt reaction in the molecule is described. Analytical expressions are obtained for the yields and time distributions of quanta and conversion muons formed in nuclear fusion reactions in molecules. It is shown that information on the desired parameters can be found from the joint analysis of the time distributions of quanta and conversion muons to be obtained in experiments with the H-T mixture at three (and more) appreciable different atomic concentrations of tritium. The experiments with the H-T mixture at the meson facility PSI (Switzerland) are planned to be optimized to gain the precise information about the desired CF parameters.Received: 5 June 2002, Published online: 15 July 2003PACS: 25.10.+s Nuclear reactions involving few-nucleon systems - 25.60.Pj Fusion reactions - 36.10.-k Exotic atoms and molecules (containing mesons, muons, and other unusual particles)     

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.     

Kinetics of muon catalyzed fusion processes in solid H/D mixture

This paper presents the final results of an experimental study of the kinetics of the muon catalysed fusion (MCF) in solid hydrogen-deuterium mixtures (H/D) at a temperature of 3 K. The experiment E742 was carried out on a TRIUMF meson facility in Canada. Four exposures were performed at different deuterium concentrations in the H/D mixture: c_d = 0.0005, 0.02, 0.15 and 0.75. A simultaneous analysis of the measured time distributions of the 5.5 MeV γ-quanta and the 5.3 MeV conversion muons obtained from nuclear fusion in the pdμ molecule allowed to extract the values of MCF chain parameters in the H/D mixture: the fusion partial rates for different nuclear spin states of the pdμ molecule, and the pdμ molecule formation rate. The experimental data fitting procedure was conducted in two ways: using solely the analytical formulae describing the kinetics of the MCF processes in the H/D mixture, and the detailed Monte Carlo simulation of the entire experiment. The results obtained by these two methods are consistent with each other and confirm the existence of the Wolfenstein-Gerstein effect.     

Nuclear fusion in charge-asymmetric muonic molecules

Nuclear fusion reactions in hydrogen-lithium muonic molecules, (where h=p,d,t) are considered and fusion rates from rotational states J=0 of the molecules are presented. Results obtained depend on the isotopic composition of the molecules and range between and . The upper limit for fusion rates from rotational states J=0 of hydrogen-helium muonic molecules, and , equal , is also found. Received: 4 December 1997 / Revised: 30 April 1998 / Accepted: 7 May 1998     

Nuclear fusion in excited hydrogen molecules

We evaluate the nuclear fusion rates in the excited vibrational states of molecules of hydrogen isotopes. The ground state fusion rate is increased by about eight orders of magnitude but even in the most favorable situation it is out of any possible experimental test. We discuss the effects due to the nuclear potential in different hyperfine states, and the improvements attainable using coherent states and a solid phase.     

Efficiency of the muon catalyzed fusion in triple H/D/T mixtures

In this paper, we solve numerically kinetic equations for the chain reactions of μCF in triple H/D/T mixture. Regarding the computational results, we show that μCF efficiency decreases by adding hydrogen H to D/T mixture. This is in contradiction to the usual belief which expects the increase of μCF efficiency in H/D/T mixture. Our results are confirmed by the first and recent experiment on μdt cycling rate in the triple mixture. This revised version was published online in July 2006 with corrections to the Cover Date.     

Unparticles and muon decay

Recently Georgi has discussed the possible existence of ‘Unparticles’ describable by operators having non-integral scaling dimensions. With the interaction of these with the Standard Model particles being constrained only by gauge and Lorentz symmetries, it affords a new source for lepton flavour violation. Current and future muon decay experiments are shown to be very sensitive to such scenarios.     

Spin-Flip and Elastic Processes in Slow Collisions of Mesic Atoms

The reduced adiabatic hyperspherical (RAHS) basis suggested previously is used for the calculation of elastic and spin-flip cross sections in the processes (aμ) _F + a → (aμ) _F′ + a, a = (p, d, t), for collision energies 10⁻³ ≤ ε ≤ 10² eV. The rapid convergence of the method is demonstrated. A comparison of the obtained results with previous ones is presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

Contribution of prompt muon production to total muon fluxes

Summary The flux of prompt cosmic-ray muons coming from charmed particles which are produced in both nondiffractive and diffractive processes of primary-air collisions is computed. Its maximum contribution is estimated by stressing the diffractive character of produced charmed particles. We compare the observed results on angular distributions of muon intensities at a given depth with the calculated results. There is no clear evidence for prompt muons. In a more quantitative analysis, χ² tests with regard to the expected form of the muon spectrum are performed. The expectation is based on a formula of Thompson and Walley for muons coming from pion and kaon decay which shows a sec θ enhancement plus a part of prompt muons. From these quantitative analysis, it is concluded that prompt muons may contribute to the total flux in the energy range between several TeV and several hundreds of TeV but are not beyond the maximum prediction.

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Riassunto Si calcola il flusso di muoni pronti dei raggi cosmici che derivano da particelle cariche che sono prodotte in processi sia diffrattivi che non diffrattivi di collisioni primariearia. Si stima il suo contributo massimo sottolineando il carattere diffrattivo delle particelle con charm prodotte. Si confrontano i risultati osservati sulle distribuzioni angolari delle intensità muoni a una data profondità con i risultati calcolati. Non c'è una chiara evidenza per i muoni pronti. In un'analisi piú qualititativa si calcolano test χ² con riferimento alla forma prevista dello spettro muonico. La previsione è basata su una formula di Thompson e Walley per muoni che derivano dal decadimento di pioni e kaoni che mostra un incremento di sec θ piú una parte di muoni pronti. Da questa analisi quantitativa si conclude che i muoni pronti possono contribuire al flusso totale nell'intervallo di energia da alcuni TeV a parecchie centinaia di TeV ma non sono al di sotto della previsione massima.

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Резюме Вычисляется поток быстрых мюонов космических лучей, происходящих от очарованных частиц, которые были образованы в недифракционных и дифракционных процессах первичных соударений. Оценивается максимальная величина вклада быстрых мюонов, отмечая дифракционный характер образованных очарованных частиц. Мы сравниваем наблюденные результаты для угловых распределений мюонных интенсивностей на данной глубине с результатами вычислений. Не обнаружено явного подтверждения для быстрых мюонов. Проводится количественный анализ, χ² проверка ожидаемой формы мюонного спектра. Ожидаемая величина определяется из формулы Томпсона и Валлея для мюонов, возникающих из распадов пионов и каонов, которая обнаруживает sec θ возрастание плюс вклад от быстрых мюонов. На основании этого количественного анализа делается вывод, что быстрые мюоны могут давать вклад в полый поток в области энергий от нескольких ТэВ до нескольких сотен ТэВ.