Plasma parameters in the upgraded Trimyx-M Galathea

Results are presented from measurements of the plasma parameters in the upgraded Trimyx-M Galathea. After the barrier magnetic field and the energy of the injected hydrogen plasma bunch were increased to B _bar ∼ 0.1 T and W ₀ ≈ 200 J, respectively, the following plasma parameters were achieved: the density n ∼ 5 × 10¹³ cm⁻³, the plasma confinement time τ* = 800–900 μs, the elergy of the confined plasma W ₁ ∼ 100 J, the ratio of the plasma pressure to the barrier magnetic pressure β ₀ ∼ 0.2, the electron temperature T _e ∼ 20 eV, and the ion temperature T _i ∼ 2T _e . The maximum time during which the plasma density decreased e-fold, τ _p , was found to be 300 μs at B _bar = 0.1 T, which agrees with the classical transport model.     

Influence of the absorbed optical quanta energy on GHz ultrasound generation in GaAs

Experimental results of the investigation of the optoacoustic processes taetang place in GaAs semiconductor at ultrashort time scales are reported. Femtosecond laser has been used both for the generation (through the deformation potential mechanism by the interband absorption of laser radiation) and detection of GHz ultrasound waves. First experimental observation of an abrupt change in the phase of the photoexcited GHz ultrasound, when with increase of the energy of optical quanta direct generation of the electron-hole pairs in the side-valleys of GaAs becomes allowed by the energy and momentum conservation laws, is reported. We relate this observation, at least partially, to abrupt change in the ultrafast dynamics of photogenerated electron-hole plasma, in particular to deceleration of plasma diffusion when heavy carriers in the high energy side valley are photogenerated instead of light carriers in the lowest energy valley.     

First spin flipping of a stored spin-1 polarized beam

We recently studied spin flipping of a 270 MeV vertically polarized deuteron beam stored in the Indiana University Cyclotron Facility Cooler Ring. We adiabatically swept an rf solenoid's frequency through an rf-induced spin resonance and observed its effect on the deuterons' vector and tensor polarizations. After optimizing the resonance crossing rate and maximizing the solenoid's voltage, we measured a vector spin-flip efficiency of 94.2%+/-0.3%. We also found striking behavior of the spin-1 tensor polarization.     

Study of the effect of intracenter and cross-relaxation transitions on the efficiency of 1.54-μm luminescence of Er<Superscript>3+</Superscript> ions in ZBLAN glass

Mechanisms underlying the effect of Tb³⁺ and Eu³⁺ ions on the efficiency of 1.54-μm luminescence of Er³⁺ ions in ZBLAN glass were studied. The cross-relaxation coefficients were measured. The ion-ion interaction channels considered were used to construct coupled balance equations describing the variation in ion level population. The optimum concentrations of the dopants were found. The experimental data obtained and theoretical estimates evidence the possibility of increasing the population of the ⁴ I _13/2 state of the Er³⁺ ion, which would enable development of more efficient erbium-based amplifiers in the case of excitation at the wavelength of 0.975 μm.     

Partition functions of matrix models as the first special functions of string theory: Finite Hermitian one-matrix model

Although matrix model partition functions do not exhaust the entire set of -functions relevant for string theory, they are elementary blocks for constructing many other -functions and seem to capture the fundamental nature of quantum gravity an string theory properly. We propose taking matrix model partition functions as new special functions. This means that they should be investigated and represented in some standard form without reference to particular applications. At the same time, the tables and lists of properties should be sufficiently full to exclude unexpected peculiarities appearing in new applications. Accomplishing this task requires considerable effort, and this paper is only a first step in this direction. We restrict our consideration to the finite Hermitian one-matrix model an concentrate mostly on its phase and branch structure that arises when the partition function is considered as a D-module. We discuss the role of the CIV-DV prepotential (which generates a certain basis in the linear space of solutions of the Virasoro constraints, although an understanding of why and how this basis is distinguished is lacking) an evaluate several first multiloop correlators, which generalize the semicircular distribution to the case of multitrace and nonplanar correlators.Translated from Teoreticheskaya i Matematicheskaya Fizika,Vol. 142, No. 3, pp. 419–488, March, 2005.     

Photoluminescence of nanocrystalline silicon formed by rare-gas ion implantation

A new method is suggested for fabricating nanocrystalline silicon by using high-dose

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irradiation with rare-gas ions. In this case, a nanostructure is formed due to silicon self-assembling on the interface between amorphous layer and crystalline substrate. Two bands, at 720 and 930 nm, are found in the photoluminescence spectrum. These bands possibly originate from the quantum confinement effects in nanocrystals and may also be related to the regions of disordered silicon outside the amorphous layer containing nanocrystals. The intensity of the photoluminescence signal is studied as a function of duration of HF etching of samples and their subsequent exposure to atmosphere. The influence of thermal annealing on the photoluminescence spectrum is also studied.

     

Effect of coalescence and of the character of the initial oxide on the photoluminescence of ion-synthesized Si nanocrystals in SiO<Subscript>2</Subscript>

The photoluminescence intensity (PLI) related to Si nanocrystals in a SiO₂: nc-Si system synthesized by ion implantation is studied experimentally and theoretically as a function of the Si+ ion dose at various annealing temperatures T_ann (1000–1200°C). The dose corresponding to the maximum PLI is found to decrease with increasing T_ann. These data are explained in terms of a model taking into account the coalescence of neighboring nanocrystals and the dependence of the probability of radiative recombination of quantum dots on their size. It is found that, when silicon oxide is grown in a wet atmosphere, the photoluminescence spectrum contains an additional band (near 850 nm), which is related to shells around the nanocrystals. This band weakens abrupily after high-temperature annealing in an oxidizing atmosphere (air).     

强流回旋加速器综合试验装置的磁场测量与垫补

强流回旋加速器综合试验装置的主体是一台紧凑型回旋加速器,加速器主磁铁材料的不均匀性,磁铁加工和安装的非理想因素将引起中心平面的磁场的非理想分布,因此有必要对其中心平面的磁场进行测量和垫补.本文主要讲述该综合试验装置的霍尔感应磁场测量系统的设计和使用;通过磁场测量数据分析进行镶条的再加工,最终实现对等时性磁场和束流的纵向聚焦的垫补;研究与实践了一种对磁场一次谐波进行垫补的方法,垫补的结果满足了设计的要求.