A new analysis chamber with a rotating target holder for total-sample PIXE analysis of aerosol deposits collected in Berner impactors

We describe an external PIXE analysis chamber provided with means for determining the total amount of aerosol material sampled in Berner impactors. The deposits are concentrated in equally spaced small spots along a circle with a diameter of 50 mm. To pass the whole distribution of material through the probing proton beam, the thin backing film is mounted on a rotatable target holder. Driven by a motor, the holder is rotating at a speed of typically 1/min. Depending on the total duration of the analysis, the sample is rotated 3–10 times through the beam. For high sample throughput the analysis chamber is coupled to a helium-backfilled transfer box in which six holders can be stored, at the same pressure as in the analysis chamber. Loading of the transfer box, with a minimum loss of helium, is accomplished by activating load locks on either side of the box. The first experience gained with aerosol samples as well as with dedicated reference standards is discussed with particular reference to the uniformity of aerosol deposits.     

A simple apparatus for the injection of lithium aerosol into the scrape-off layer of fusion research devices

A simple device has been developed to deposit elemental lithium onto plasma facing components in the National Spherical Torus Experiment. Deposition is accomplished by dropping lithium powder into the plasma column. Once introduced, lithium particles quickly become entrained in scrape-off layer flow as an evaporating aerosol. Particles are delivered through a small central aperture in a computer-controlled resonating piezoelectric disk on which the powder is supported. The device has been used to deposit lithium both during discharges as well as prior to plasma breakdown. Clear improvements to plasma performance have been demonstrated. The use of this apparatus provides flexibility in the amount and timing of lithium deposition and, therefore, may benefit future fusion research devices.     

A simple model for quantifying the degree of layer-by-layer growth in low energy ion deposition of thin films

Layer-by-layer growth of thin films can be promoted by using low energy ion deposition (LEID) techniques. The basic process affecting the growth are often quite diverse, but often the ion impact induced inter layer mass transfer processes due to adatom insertion to lower step edges or pile-ups to step edges above dominate. In this paper we propose a simple phenomenological model which describes the growth of thin films in LEID under these conditions. The model makes possible to distinguish the dominant growth, the detection of the transition from the 3D growth to 2D growth, and it can be used to quantify the degree of layer-by-layer growth. The model contains only two parameters, which can be phenomenologically related to the properties of the bombarding ion beam.     

A new approach for cross section evaluations in the high energy region

A new approach for a cross section evaluation above the resonance region is introduced and described. It employs the KALMAN code and the Monte-Carlo tuning program called the TalysTuner to automatically adjust the model parameters. As a nuclear reaction model code, TALYS is used. The cross sections for ²³⁵U are calculated up to 150 MeV using the new method and compared with the available experimental data and other evaluations.     

一种基于PC/104的便携式建材放射性检测仪

介绍了一种新型的便携式建材放射性检测仪。给出了仪器总提框图,讨论了其工作原理、具体的电路实现和仪器下位机软件框图。仪器以PC／104为核心,结合A／D采集卡和PKD-01等集成芯片．具有电路结构简单．可靠性和稳定性高的特点。     

A new model for predicting the critical heat flux based on nucleation site density in downward-face boiling

ABSTRACT

Due to the important role critical heat flux (CHF) plays in the boiling field, it is of great significance to study CHF, especially the mechanism of CHF in the nucleate boiling. In this study, a new model to predict CHF both in pool boiling and flow boiling of downward-face was proposed and the relationship between CHF and nucleation site density (NSD) was studied. The model was based on the bubble interaction theory, which assumed that CHF happened due to the coalescing of the bubbles generated on the heating surface and prevented liquid to be supplied. The relationship between NSD and CHF was derived from previous observations in the experiments and simulations. To validate the relationship between NSD and CHF, several experiments with CHF and NSD were chosen and they all showed good agreement with our assumptions. Due to the rarity of experimental data on NSD and CHF, the numerical method was also used to validate. The results also showed an inverse relationship between CHF and NSD.     

大亚湾核电站蒸汽除湿再热器管板热电偶的钻取

介绍了从15/6×475的蒸汽除湿再热器(MSR)管板孔腔中钻取断热电偶的方案和过程,重点介绍了专用钻具的研制和改进,为今后从狭长孔腔中取出“顽固”并摆动的内插件这类难题提供了一个有效的解决方案。