Diffusion of muonic deuterium inD2gas

Abstract

Diffusion of muonic deuterium (yd) atoms in D2 at 300 K was studied at pressures of 0.1-10 bars by measuring the distributions of time intervals between entry of negative muons into the gas and detection of photons emitted upon the arrival of pd atoms at foils spaced along the muon beam axis. The results indicate an approximately Maxwellian velocity distribution with a mean energy of 1.8 ±0.1 eV for the pd atoms, and pd scattering cross sections in agreement with theory.PACS numbers: 36.10.DrKnowledge of the behavior of muonic hydrogen atoms (pp, pd, and pt) in matter is important to studies of the weak interactions of muons and the muon-catalyzed fusion of light nuclei. Experimental efforts to establish this behavior were carried out for many years at CERN, 1 along with some related work by others. 2 We have modified the CERN technique and extended it to D2 pressures lower by 2 orders of magnitude and with reduced statistical uncertainties. Our results differ substantially from earlier work. lf2 The experimental method involved stopping muons in purified D2 gas filling the regular interstices between multiple parallel planar foils arrayed normal to the incident muon beam (Fig. 1). Scintillation counters detected incident muons, some of which stopped in the gas and formed fid muonic atoms in highly excited states, which then rapidly («ns) (Ref. 3) deexcited to the IS* state. The subsequent motion was determined by the initial velocity distribution of the pd atoms and by the elastic and inelastic scattering of the jid atoms by D2 molecules. In the case of those pd*s which survived to reach a foil surface, the muons transferred to excited atomic states, bound to nuclei of the foil surface material. During the following processes of atomic deexcitation and nuclear absorption a characteristic "transfer photon spectrum" was emitted. This spectrum included muonic x rays, electronic x rays, and nuclear deexcitation 7 rays. The time distributions of such delayed signals relative to the incident muon signals were then accumulated and analyzed.Our modifications of the CERN experiments l included use of (i) a low-(34 MeV/c) momentum beam in the pE4 area at the Paul Scherrer Institute meson factory to optimize stopping of the p. ~ in the D2 gas, (ii) an array of four intrinsic Ge photon detectors providing highenergy resolution to improve photon-line identification and signal-to-noise ratio, and (iii) foils of thin (9 pm) low-vapor-pressure plastic (Kynar, C2H2F2) film 4 coated on both sides with 100 ± 10 A of Au to minimize background from muon stops in the surface layer material. The fifty foils used were each 10 cm in diameter, and were mounted with ±5% uniformity in spacing. Deuterium pressures of 188, 375, 750, or 1520 mbar were used with 0.23-cm foil spacing, and 188, 375, and 750 mbar with 0.46-cm spacing. The D2 was at 300 K and was continuously circulated through a Pd purifier during the data runs. The electronic logic system was a variant of one previ- FIG. 1. Experimental setup for the diffusion experiment. Plas...

Muonic hydrogen and deuterium in H-D mixture and muon transfer in excited states

“…A Maxwellian kinetic energy distribution was assumed at n"6, with the energy ¹ M being treated as parameter. This assumption is in fair agreement with results from the muonic hydrogen diffusion experiment [23,24], as it was discussed in [17]. Contrary to radiative and Auger processes, the transition energy in Coulomb collisions transforms to the recoil of heavy particles, and a p can gain about 28 eV as a result of transition (n"5) P (n"4) and 61 eV for (n"4) P (n"3).…”

“…By treating the kinetic energy as a fitting parameter and comparing the results for Q Q with the data of [7], they concluded that the average kinetic energy of the p in H/D mixtures is about 6 eV. The experiments on the p and d diffusion in gas [23,24,25], however, demonstrate that the kinetic energy distribution depends on the density and has a multicomponent structure. The mean kinetic energy of muonic hydrogen in the ground state in gas increases from about 2 eV at 47 mbar to more than 9 eV at 750 mbar [25].…”

Muon catalysed fusion Chemical confinement of nuclei within the muonic molecule dtμ

“…[70], and at CERN [71]. Recent experiments at PSI on diffusion of muonic atoms in gaseous targets at very low pressures [72] established that the (d~t)ls atoms approximately follow a Maxwell distribution with a mean energy E= 1.8 0.1eV. This value unexpectedly exceeds previous theoretical estimations [73,49,74,66], all below 1 eV.…”

Muon catalysis and nuclear breeding

“…В дальнейшем мезоатомы замедляются в упругих столкновениях типа и, кроме того, в них происходят неупругие процессы девозбуждения, пу тем внешнего оже эффекта при столкновениях мезоатомов с молекула Вследствие всех этих процессов энергетическое распределение мезо атомов в основном состоянии может отличаться от максвелловского, и это отличие может оказаться существенным при детальном описании кинетики процессов катализа. В последние годы получены экспери ментальные свидетельства в пользу этого заключения [127][128][129].…”