Transverse and longitudinal nuclear magnetic resonance in superfluid 3He in anisotropic aerogel

It is found that the properties of nuclear magnetic resonance of both superfluid phases of ³He in an anisotropic aerogel can be described in terms of the bulk superfluid order parameters with the orbital order parameter vector fixed by anisotropy of the aerogel sample. It is also shown that, by proper squeezing, it is possible to attain a sample with isotropic NMR properties. The text was submitted by the authors in English.     

Nonlinear NMR in a superfluid B phase of <Superscript>3</Superscript>He in aerogel

The properties of liquid ³He in a low-density aerogel preliminarily covered with a few monolayers of ⁴He were studied by pulsed and nonlinear CW NMR techniques. It was found that an NMR frequency shift from the Larmor value exhibits a sharp increase at a magnetization tilting angle exceeding 104°. Nonlinear CW NMR signals related to the formation of a macroscopic region featuring homogeneous precession of the magnetization (homogeneous precession domain) were observed. The experimental results confirm that the low-temperature superfluid ³He phase in the aerogel is analogous to the B-phase in bulk ³He and indicate that the spin supercurrents play an important role in the spin dynamics of superfluid ³He in aerogel.     

Precision magnetic quadrupole lens for a nuclear scanning microprobe based on an ÉGP-10 electrostatic tandem accelerator

Basic ideas underlying the design of a precision magnetic quadrupole lens for a nuclear scanning microprobe with a maximal accelerating voltage of 14 MV are set forth. Four magnetic quadrupoles are combined into doublets. The doublets are placed on adjusting gears, which bring the local coordinate system of each lens into coincidence with the laboratory system related to the axis of the beam. Each lens provides a maximal gradient of the field of 0.68 T/cm, which makes it possible to perform stigmatic focusing of the beam with a working distance of 22 cm. All lenses are nonseparable and made of one piece of high-quality electrical steel. A special lens-feeding unit is designed that provides manual and remote control of pole tip excitation.     

Transverse and longitudinal nuclear magnetic resonance in superfluid <Superscript>3</Superscript>He in anisotropic aerogel

It is found that the properties of nuclear magnetic resonance of both superfluid phases of ³He in an anisotropic aerogel can be described in terms of the bulk superfluid order parameters with the orbital order parameter vector fixed by anisotropy of the aerogel sample. It is also shown that, by proper squeezing, it is possible to attain a sample with isotropic NMR properties.     

Linear NMR in the Polar Phase of <Superscript>3</Superscript>He in Aerogel

³He is an example of the system with non-trivial Cooper paring. A few different superfluid phases are known in this system. Recently the new one, the polar phase, have been observed in ³He confined in nematically ordered aerogel. A number of various topological defects including half-quantum vortices can exist the polar phase. In this work, we present theoretical and numerical studies of linear nuclear magnetic resonance in the polar phase both in the uniform order-parameter texture and in the presence of half-quantum vortices.     

Optimization of the probe-forming system for a scanning nuclear microprobe based on the ÉGP-10 electrostatic tandem accelerator

The probe-forming system of a nuclear scanning microprobe based on the parametric multiplets of quadrupole lenses is optimized. The optimization is aimed at creating an ion probe with energy of several MeV that produces a micrometer spot on the target at a current of ∼100 pA. The influence of different geometric and physical parameters on the ion-optical properties of the probe-forming systems considered is determined. The optimization is carried out by varying the parameters specifying a given parametric multiplet, and its efficiency is found from a quality criterion that takes into account the beam current for given sizes of the spot and target. The beam parameters at the entrance to and at the exit from the éGP-10 electrostatic tandem accelerator (produced by the VNIIéF) are involved in the optimizing calculations. These are the maximal energy, normalized brightness, transport conditions, and chromatic inhomogeneity of the beam (i.e., the energy straggling of beam particles). Allowance is also made for the parasitic components of the magnetic quadrupole lens field, which arise because of quadrupole symmetry breaking by technological and physical reasons.     

Measurement of the Leggett frequency in <Superscript>3</Superscript>He-B in aerogel

The method of measuring the Leggett frequency of ³He-B using spatially homogeneous oscillations of a homogeneously precessing domain was developed. The temperature dependence of Leggett frequency was measured for bulk ³He-B and ³He-B in aerogel at a pressure of 19.5 bar.     

Powerful wideband amplifier based on hybrid plasma-cavity slow-wavestructure

A powerful beam-plasma amplifier operating under continuous conditions is described. The amplifier is designed on new principles using hybrid plasma-cavity electrodynamic structures. The theory and foundation for calculating slow-wave structures having a plasma filled propagation channel, and the interaction of an electron beam with a hybrid plasma-cavity system, are considered. Considerably increased power of microwave radiation and expansion of the operating pass-band is shown to result when the propagation channel is filled with plasma. The use of new principles makes it possible to create an amplifier with an efficiency and 3 dB operating band width higher than those attained in vacuum devices