Muon Losses Research Articles

Reduction of coherent betatron oscillations in a muon g − 2 storage ring experiment using RF fields

This work demonstrates that two systematic errors, coherent betatron oscillations (CBO) and muon losses, can be reduced through application of radio frequency (RF) electric fields, which ultimately increases the sensitivity of the muon g − 2 experiments. As the ensemble of polarized muons goes around a weak focusing storage ring, their spin precesses, and when they decay through the weak interaction, , the decay positrons are detected by electromagnetic calorimeters. In addition to the expected exponential decay in the positron time spectrum, the weak decay asymmetry causes a modulation in the number of positrons in a selected energy range at the difference frequency between the spin and cyclotron frequencies, ω a. This frequency is directly proportional to the magnetic anomaly a μ = (g − 2)/2, where g is the g-factor of the muon, which is slightly greater than 2. The detector acceptance depends on the radial position of the muon decay, so the CBO of the muon bunch following injection into the storage ring modulate the measured muon signal with the frequency ω CBO. In addition, the muon populations at the edge of the beam hit the walls of the vacuum chamber before decaying, which also affects the signal. Thus, reduction of CBO and unwanted muon loss increases the a μ measurement sensitivity. Numerical and experimental studies with RF electric fields yield more than a magnitude reduction of the CBO, with muon losses comparable to the conventional method.

Muon loss rates from betatron resonances at the Muon g − 2 Storage Ring at Fermilab

The Muon [Formula: see text] Experiment at Fermilab (E989) is directed toward measuring the muon magnetic anomaly, [Formula: see text], with total statistical and systematic errors of 0.14 ppm. This new measurement will serve as strong probe of effects of as yet undiscovered particles beyond the Standard Model (SM), and perhaps validate or disprove other theoretical models beyond the SM. Of special interest is the reduction of muon losses from the storage ring to achieve the precision needed at the Muon [Formula: see text] Experiment. For this purpose, we have developed a detailed and precise symplectic model of the Muon [Formula: see text] Storage Ring using COSY INFINITY that considers measured inhomogeneities of the magnetic field; high-order representation of the Electrostatic Quadrupole System (EQS) electrostatic field at different stages of the experiment including fringe fields; injection to the ring based on measurements; and beam collimation. Specifically, we have performed numerical analyses of the rate of muons that are lost before they have a chance to decay for several possible configurations of the EQS in order to find the best possible scenarios that minimize muon losses and understand the resonance mechanisms that contribute to betatron and possibly spin resonances. Additionally, comparisons with measurements have permitted the determination of whether observed resonances come from anticipated features of the [Formula: see text] storage ring or from unexpected sources of error whose effect could be detrimental to the precision of E989.

Unified atmospheric neutrino passing fractions for large-scale neutrino telescopes

The atmospheric neutrino passing fraction, or self-veto, is defined as the probability for an atmospheric neutrino not to be accompanied by a detectable muon from the same cosmic-ray air shower. Building upon previous work, we propose a redefinition of the passing fractions by unifying the treatment for muon and electron neutrinos. Several approximations have also been removed. This enables performing detailed estimations of the uncertainties in the passing fractions from several inputs: muon losses, cosmic-ray spectrum, hadronic-interaction models and atmosphere-density profiles. We also study the passing fractions under variations of the detector configuration: depth, surrounding medium and muon veto trigger probability. The calculation exhibits excellent agreement with passing fractions obtained from Monte Carlo simulations. Finally, we provide a general software framework to implement this veto technique for all large-scale neutrino observatories.

High-pressure solid hydrogen target for muon catalyzed fusion

We have developed a high-pressure solid hydrogen target for muon-catalyzed fusion to study temperature dependence of fusion cycling rates and muon loss probabilities in solid hydrogen at higher temperature than the melting point. The constructed target is a simple standalone-system consisting of a solid hydrogen target, a high-pressure generator, an isolation valve and a buffer tank. The solid hydrogen target and high-pressure generator are independently cooled down and temperature-controlled by closed-cycle helium-refrigerators. In the performance test, the solid D2 target was formed successfully at 33.6 K with applying D2 gas pressure at 79 MPa.

Anomalous Temperature-Dependent Phenomena of Muon Catalyzed Fusion in Solid Deuterium and Tritium Mixtures

A systematic experimental study was conducted on muon-catalyzed fusion in solid deuterium and tritium mixtures. Various conditions were investigated, i.e. tritium concentrations from 20% to 70%, and temperatures from 5 K to 16 K. With decreasing temperature, unexpected increase in the muon cycling rate and decrease in the muon loss probability were observed. The former change is interpreted to be caused by the temperature dependence in the dtp formation process. The most probable origin of the latter change is the temperature dependence in the muon reactivation process after muon-to-a sticking.

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.

Investigation of the Parameters of Muon-Catalyzed Fusion in Double D/T Mixture at High Temperature and Density

Experiments on the study of the muon catalyzed fusion (μCF) process in a double D/T mixture of hydrogen isotopes in the temperature range 300–800 K at densities 0.3–0.5 LHD are performed at the JINR phasotron. The values of the effective μCF parameters (cycling rate λ c , neutron yield Y n , muon losses w) are obtained. Tentative dtμ-molecule formation rates on D2 and DT molecules (λ dtμ−d and λ dtμ−t ) are obtained for different mixture temperatures and densities. The results obtained show that λ dtμ−t increases with temperature, but its value is smaller than theoretical predictions.

Effective Muon Losses in the Muon Catalyzed Fusion Cycle in a Double D/T Mixture at High Temperature and Density

The effective muon losses w measured in the last experiment of the JINR group with D/T mixture are analyzed. They are considered as a function of the tritium concentration C t taken for different temperatures. The obtained results indicate different muon transfer rates from deuterium and tritium to impurities with Z>1 (λ dZ and λ tZ ) and show that the ratio λ tZ /λ dZ increases with temperature.

Experimental Results on Muon Catalyzed dt Fusion in H/D/T Mixture

Experimental study on muon catalyzed dt fusion in a triple mixture of hydrogen isotopes (H/D/T) was carried out at the JINR phasotron. The measurements have been performed at various temperatures and densities with liquid and gaseous H/D/T mixtures. Results are presented for the main characteristics of the dtμ cycle. A reduction of the number of dt fusions is observed when hydrogen is added to the D/T mixture, This is mainly due to muon loss to the pt and pd cycles, which have a high sticking probability. We also observe an increase of the cycle rate when the temperature of the H/D/T mixture rises. This confirms the theoretical prediction.

Cold fusion: muon-catalysed fusion

The authors put into perspective and further develop their recent work in muon catalysed fusion, with the objective of identifying the key physical processes in the t(d,n) alpha fusion cycle relevant to energy related applications. They begin by discussing the fusion cycle and point out the importance of direct nuclear reactions in the catalysed fusion processes. This is followed by an in-depth discussion of the muon loss reaction by attachment to the fusion alpha -particle. Finally, the authors examine some special topics that have attracted the attention of workers in the muon-catalysed fusion (MuCF) community, such as energy efficient production of muons and proposals for MuCF reactors, the potential of Z>1 fusion, and other recently discussed forms of cold fusion.

Muon catalyzed fusion

This paper presents an overview of the program and results of our experiment performed by a European-American collatoration at the Swiss Institute of Nuclear Research. Systematic investigations of the low temperature region (23K to 300K) reveal a surprisingly rich physics of mesoatomic and mesomolecular processes, unparalleled in other systems of isotopic hydrogen mixtures. A dramatic density dependence of the reaction rates is found. The rich structure in the time spectra of the fusion neutrons observed at low gas density yields first evidence for new effects, most likely strong contributions from reactions of hot muonic atoms. The important question of muon losses due to He sticking is investigated by different methods and over a wide range of tritium concentrations.

Design principles for efficient muon production in muon-catalyzed fusion reactors

The two major schemes for a fixed-target muon production system in muon-catalyzed fusion reactors are analyzed and compared using Monte Carlo simulation techniques. Starting with a careful optimization of the pion production target we next consider the complete system where pion conversion losses and muon losses in the target and the pressure vessel are taken into account. A simple but realistic design for the pion-muon converter is introduced. Problems and inefficiencies are identified to provide a basis for future inventions.

Muon transfer induced by collisional excitation of helium muonide Heμ+ after muon catalyzed fusionafter muon catalyzed fusion

Possibility of negative muon transfer from helium muonide Heμ+ to T /or D/ through collisional excitation after muon catalyzed fusion has been pointed out. The transfer process depends on the efficiency of collisional excitation of Heμ+ in the medium of tritium or deuterium. It is argued that tritium has larger nuclear stopping power and better excitation efficiency than deuterium. This effect is in the same direction as the tritium concentration dependence of muon loss probability in recent experimental work.

Muon catalysed fusion-fission reactor driven by a recirculating beam

The recent experimentally inferred values of multiplicity of deuterium-tritium fusion catalysed by muons have increased the interest in muon catalysed fusion reactors. Since the main energy expended is in pion (and consequent muon) production, it is tried to minimize the pion loss by magnetically confining pions where they are created. At the present time, it does not appear possible to achieve an energy gain by pure fusion, but it is possible to gain energy by combining catalysed fusion with fission blankets. Two new ideas for improvement of the muon fusion reactor concept are presented. The first idea is to combine the target which creates pions, the converter of pions to muons, and the synthesizer in one vessel (synergetic concept). This is accomplished by injecting a tritium or deuterium beam of 1 GeV per nucleon into DT fuel contained in a magnetic mirror. The confined pions slow down and decay to muons which are confined in the fuel whereby muon loss is kept small. The quantity of tritium necessary to keep the reactor viable has been derived. The second idea is to collect the beam passing through the target for reuse and to recirculate it, while directing the strongly interacting portion of the beam to electronuclear blankets. The present concepts are at the margin of known technologies and are based on known physical processes and data.

Apparent Muon Loss in Muon Catalyzed Fusion

Apparent Muon Loss in Muon Catalyzed Fusion