Thermal spikes from stopped muons and density effects in muon-catalyzed fusion

Local hot regions caused by energy deposition from stopped muons can significantly influence the cycle rate of muon catalyzed fusion. The observed nonlinear density dependence of molecular formation rates is explained as a result of the temperature dependence since muonic deuterium-tritium molecules are formed at a high effective temperature that increases roughly linearly with density.     

Compression and combustion of non-cryogenic targets with a solid thermonuclear fuel for inertial fusion

Variants of a target with a solid thermonuclear fuel in the form of deuterium-tritium hydrides of light metals for an inertial fusion have been proposed. The laser-pulse-induced compression of non-cryogenic targets, as well as ignition and combustion of such targets, has been examined. The numerical calculations show that, despite a decrease in the caloric content of the fuel and an increase in the energy losses on intrinsic radiation in the target containing deuterium-tritium hydrides of light metals as compared to the target containing deuterium-tritium ice, the non-cryogenic target can ensure the fusion gain sufficient for its use in the energy cycle of a thermonuclear power plant based on the inertial plasma confinement method.     

μCF based 14 MeV intense neutron source

Results of a design study for an advanced scheme of a μCF based 14 MeV intense neutron source for test material irradiation including the liquid lithium primary target and a low temperature liquid deuterium-tritium (D–T) mixture as a secondary target are presented. According to this scheme negative pions are produced inside a 150-cm-long 0.75-cm-radius lithium target. Pions and muons resulting from the pion decay in flight are collected in the backward direction and stopped in the D–T mixture. The fusion chamber has the shape of a 10-cm-radius sphere surrounded by two 0.03-cm-thickness titanium shells. Assuming 100 fusions per muon in this scheme one can produce 14-MeV neutrons with a source strength up to 10¹⁷ n/s. A neutron flux of up to 10¹⁴ n/cm²/s can be achieved in a test volume of about 2.5 l and on the surface of about 350 cm². The results of the thermophysical and thermomechanical analysis show that the technological limits are not exceeded. This source has the advantage of producing the original 14 MeV fusion spectrum without tails, isotropically into a 4π solid angle, contrary to the d-Li stripping neutron source. This revised version was published online in August 2006 with corrections to the Cover Date.     

等离子体排灰气处理技术研究进展

等离子体排灰气处理系统是聚变反应装置氘氚燃料循环系统中极为重要的环节。该系统的主要功能是从反应后的排灰气中回收剩余的氘氚燃料,并处理壁材料净化、系统维护等非正常运行模式以及分析与辅助系统中产生的含氚杂质气体。介绍了国际上聚变堆等离子体排灰气的组成和主要处理工艺,简述了钯膜分离、膜反应及催化反应-膜分离、电解反应、分解反应及氧化-分解等各关键单元技术的基本原理和研究进展,并进行了分析和评价,提出了目前国内在该领域需要开展的研究工作。     

The impact Of impurity ion in deuterium-tritium fuel on the energy deposition pattern Of The Proton Ignitor Beam

The ignition stage of deuterium-tritium fuel in inertial confinement fusion is a challenging task affected by many undesirable processes especially material mixing processes in the hot-spot region. In this research, an alternative proposal of the enhanced energy deposition in the proton fast ignition has been suggested. It consists of two primary assumptions of the beam-plasma system. In the first place, we have adopted the proton beam generated by TNSA or RPA mechanisms, each described by a Maxwellian or Gaussian energy distributions. Next, a realistic, non-uniform fuel plasma was adopted. Then, the cumulative stopping power of a proton beam of 10 kJ energy, penetrating the low content metal-contaminated deuterium-tritium fuel has been examined. It has been shown that in the case of the very low impurity fractions, irregular spatial fluctuations in the cumulative stopping power relative to pure fuel plasma emerges. However, at the higher concentrations, a systematic pattern becomes visible such that the contribution of the deep layers in the stopping power reduces. We observe the enhanced energy deposition close to the corona/dense core interface. It has been shown that the corona/dense core energy deposition ratio differs by up to 2.5% between pure and contaminated DT plasma. In the contaminated fuel plasma, energy deposition in the TNSA regime will effectively heat the plasma corona. While in the RPA counterpart, at a similar level of contamination, most of the incident beam energy remains inside the core fuel region.     

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. This revised version was published online in August 2006 with corrections to the Cover Date.     

等离子体排灰气处理技术研究进展

等离子体排灰气处理系统是聚变反应装置氘氚燃料循环系统中极为重要的环节。该系统的主要功能是从反应后的排灰气中回收剩余的氘氚燃料,并处理壁材料净化、系统维护等非正常运行模式以及分析与辅助系统中产生的含氚杂质气体。介绍了国际上聚变堆等离子体排灰气的组成和主要处理工艺,简述了钯膜分离、膜反应及催化反应-膜分离、电解反应、分解反应及氧化-分解等各关键单元技术的基本原理和研究进展,并进行了分析和评价,提出了目前国内在该领域需要开展的研究工作。     

Direct measurement of energetic electrons coupling to an imploding low-adiabat inertial confinement fusion capsule

We have imaged hard x-ray (>100 keV) bremsstrahlung emission from energetic electrons slowing in a plastic ablator shell during indirectly driven implosions at the National Ignition Facility. We measure 570 J in electrons with E>100 keV impinging on the fusion capsule under ignition drive conditions. This translates into an acceptable increase in the adiabat α, defined as the ratio of total deuterium-tritium fuel pressure to Fermi pressure, of 3.5%. The hard x-ray observables are consistent with detailed radiative-hydrodynamics simulations, including the sourcing and transport of these high energy electrons.     

Negative muon capture in very light atoms

The transition rates for unbound muons to be captured into atomic bound states are calculated as functions of (1) incident muon center-of-mass energy, (2) muon principal quantum number n, and (3) muon (final) angular momentum l, for the hydrogen, helium, and lithium atoms. These rates reflect differences in electron binding energies. At muon energies of several hundred electron volts, lithium K-shell electrons are more likely to be ejected than the L-shell electron, while this behavior is reversed for energies ? 10 eV. However, in each case when the capture rate is folded with a muon stopping power function, the result is that more than half of the unbound muons are absorbed above 75 eV. Implications for experiments which look at muon transfer processes are noted.     

Investigation of the effect of large-scale shell asymmetry on Iskra-5 target operation

Experiments designed to investigate the effect of a controlled large-scale asymmetry of a shell containing deuterium-tritium fuel on the shell compression and neutron production under indirect (x-ray) action are performed on the Iskra-5 laser fusion device. The uniformity of the x radiation near the target is not worse than 3%, and the shell asymmetry is varied from 30 to 100%. The observed decrease of the experimental neutron yield as compared with experiments using symmetric targets is in satisfactory agreement with two-dimensional calculations. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 3, 161–165 (10 February 1998)     

Kinetic simulations of fuel ion transport in ICF target implosions

A numerical code solving the ion Vlasov-Fokker-Planck kinetic equation is used to compute the hydrodynamics of the thermonuclear fuel in inertial confinement fusion pellets. Compared with standard hydrodynamics calculations, the kinetic results show enhanced ion transport between the core and the outer part of the target. Consequences are discussed in the case of plastic shells filled with deuterium gas and cryogenic deuterium-tritium targets envisioned for achieving ignition with megajoule-class lasers.Received: 25 April 2003, Published online: 12 August 2003PACS: 52.25.Fi Transport properties - 52.65.Ff Fokker-Planck and Vlasov equation     

Correlation between muonic levels and nuclear structure in muonic atoms

A method that deals with the nucleons and the muon unitedly is employed to investigate the muonic lead, with which the correlation between the muon and nucleus can be studied distinctly. A “kink” appears in the muonic isotope shift at a neutron magic number where the nuclear shell structure plays a key role. This behavior may have very important implications for the experimentally probing the shell structure of the nuclei far away from the β-stable line. We investigate the variations of the nuclear structure due to the interaction with the muon in the muonic atom and find that the nuclear structure remains basically unaltered. Therefore, the muon is a clean and reliable probe for studying the nuclear structure. In addition, a correction that the muon-induced slight change in the proton density distribution in turn shifts the muonic levels is investigated. This correction to muonic level is as important as the Lamb shift and high order vacuum polarization correction, but is larger than anomalous magnetic moment and electron shielding correction.     

Production of high-energy muons in gamma showers

We have calculated the number of high-energy muons in gamma showers generated by photoproduction and by muon pair creation. The prompt muons have flatter energy spectrum than the muons, which come from photoproduction and contribute significant fraction of the total muon rates for E_μ ? 1 TeV. The total rate of high-energy muons in gamma showers is, however, very low.     

Quasiresonant formation of dtμ and ddμ mesic molecules in triple collisions

The quasiresonant mechanism of mesic molecule formation, in triple collisions of the type tμ+D₂+D₂→[(dtμ)d2e]_ν¹+D'₂ is considered. It is shown that at small resonance defects and big D₂ +T₂ mixture densities φ the rate of this process is λ_qr∼φ², and it is comparable with the rate λ_r∼λ of the resonant formation of mesic molecules in reactions of the type tμ+D₂→[(dtμ)d2e]_ν¹. The observable manifestations of the process considered and its role in muon catalyzed fusion in deuterium-tritium mixtures are discussed.     

Muon spin echo

A muon spin echo method is proposed for determining the contributions of the static and dynamic local fields in muon experiments. It is shown that if for each muon which has stopped in the sample a rf pulse of fixed duration is applied to the sample at a time τ after the muon entered the sample, then after a sufficient number of muon-positron decays have been accumulated a muon spin echo can appear at time 2τ. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 7, 500–503 (10 October 1996)     

Measurements of the integrated muon intensity at large zenith angles

Precision measurements of the zenith-angle distributions of muons in the range 61°–89° are performed using the DECOR coordinate detector. The total number of selected events is more than 20 million. The dependence of the integrated muon intensity on the zenith angle is determined for several threshold energies in the range from 1.7 to 7.2. GeV. The experimental results in these ranges of zenith angles and threshold energies are obtained for the first time. It is demonstrated that the dependence of the integrated muon intensity on the zenith angle is adequately described by a simple analytical relationship.     

Effect of zero point motion on the hyperfine field at an interstitial positive muon site in ferromagnetic Ni

Using the inhomogeneous electron charge and spin density distribution around the octahedral site in ferromagnetic nickel from a self-consistent band structure scheme, and the abiabatic approximation, we have calculated the muon hyperfine field as a function of the muon displacement. By folding the electron spin density at the vibrating muon site obtained in a self-consistent Kohn-Sham scheme with the finite width of the muon wave function, we find a striking effect on the average muon hyperfine field. The result agrees better with the experiment than earlier calculations based on the jellium model.     

Experimental consequences of flavor- and muon number-changing neutral currents in an SU(2) × U(1) gauge model with CP nonconservation

We enumerate a large number of experimental consequences, calculated in a model within the usual framework, of the assumption that weak neutral currents exist which do not conserve flavor, and, with a lepton-quark analogy, do not conserve muon number, at the level of strength of the CP-violating parameter. The estimates are relevant to a number of experiments in progress of planned, in particular those searching for the nonconservation of muon number at the level of about 10^?9.     

Effects of Isotopic Concentrations on Thermodynamic Parameters of Deuterium-Tritium Mixtures

Thermodynamic estimation is still too much requested for scientific applications in spite of great advances in simulation methods for efficient determination of phase equilibrium of multi-component systems. In this work, thermodynamic properties of deuterium-tritium mixture in a wide range of temperatures and pressures have been predicted. Buckingham exp-6 potential has been utilized in calculations, based on statistical perturbation theory. The effects of various values of density, temperature and isotopic concentrations on pressure have been studied. Eventually, we have found out symmetrical effects of tritium concentration in deuterium-tritium mixtures.     

Detection of GLE of December 13, 2006, using the muon hodoscope

GLE of December 13, 2006, is analyzed based on the data of the muon hodoscope located at MEPhI (Moscow). The setup supermodules registered that the muon flux intensity started increasing at 0254 UTC. An increase at a maximum (0300 UTC) was 0.61 ± 0.09% (for the 10-min data), which is larger than six standard deviations. The detection of the muon flux in the hodoscope mode for the first time made it possible to obtain the two-dimensional images of an increase in the muon flux. A comparison of the muon hodoscope and neutron monitor data makes it possible to conclude that the muon event was caused by a highly collimated bunch of the solar proton fast component.