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The Beijing intense slow positron beam facility is based on the 1.3GeV linac of Beijing Electron-Positron Collider (BEPC) aiming to produce mono-energetic intense slow positron beam for material science investigation. The plugged-in 22Na based slow positron beam section has been newly constructed to supply continuous beam time for the debugging of positron annihilation measurement stations and improve the Beijing intense slow positron beam time using efficiency. Performance testing result of the plugged-in 22Na based slow positron beam facility are reviewed in this paper, with the measurement of the beam transport efficiency, the view of beam spot, the adjustment of beam position, the measurement of beam intensity and energy spread etc. included. 相似文献
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In order to calculate the effect on the beam caused by an irregular accelerator element, we have expanded and improved the Linear and Electrostatic Accelerator Dynamics Simulation (LEADS) code. To achieve better calculation precision, the element was divided into lots of equal intervals. In order to simplify the calculation process, a one-dimensional field is simulated and the Lorenz equation is used directly. A one-dimensional field can be imported into the LEADS code. The heteromorphic quadrupole is invented and its field is simulated and optimized using the POISSON code. As examples, the effect on the beam caused by the heteromorphic quadrupole and octupole is simulated. 相似文献
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Positron annihilation lifetime and Doppler broadening of annihilation line techniques have been used to obtain information about the small pore structure and size of porous SiO2 thin film produced by sputtered Al-Si thin film and etched Al-Si thin film. The film is prepared by an Al/Si 75:25 at.-% (A175Si25) target with the radiofrequency (RF) power of 66 W at room temperature. A 5 wt.-% phosphoric acid solution is used to etch the Al cylinders. All the A1 cylinders dissolved in the solution after 15 h at room temperature, and the sample is subsequently rinsed in pure water. In this way, the porous SiO2 on the Si substrate is produced. From our results, the values of all lifetime components in the spectra of Al-Si thin film are less than 1 ns, but the value of one of the lifetime components in the spectra of porous SiO2 thin film is τ = 7.80 ns. With these values of lifetime, RTE (Rectangular Pore Extension) model has been used to analyze the pore size. 相似文献
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This paper describes the development and application of an intense slow positron beam at IHEP with regard to its two main components.
The Variable-Energy Positron Lifetime Spectroscopy (VEPLS) based on the pulsing system consisting of a chopper, a prebuncher and a buncher has been constructed in order to meet the needs of materials science development. At present, the time resolution of the VEPLS can easily reach about 386ps with a peak-to-background ratio of about 600:1. A plugged-in 22Na positron source section for adjusting the newly built experimental station and for increasing the beam operation efficiency has been constructed. A slow positron beam with an intensity of 2.5×105e+/s and the beam profile whose diameter is 10mm has been obtained; the moderation efficiency of the tungsten mesh moderator reaches 5.1×10-4 as calculated with an original positron source activity of 52mCi. 相似文献
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