PHOTOINDUCED CHANGES OF HYDROGEN-BONDING IN SEMIINSULATING IRON-DOPED INDIUM-PHOSPHIDE

After illumination with 1-1.3 eV photons during cooling-down, metastable PH modes are observed by IR absorption at 5 K in semi-insulating InP:Fe. They correlate with the photo-injection of holes, but not with a change of the charge state of the K-related centres present at equilibrium. They are explained by a change of the bonding of H, induced by hole trapping, from IR-inactive centres to PH-containing centres, stable only below 80 K. One metastable centre has well-defined geometrical parameters and the other one could be located in a region near from the interface with (Fe,P) precipitates.

Resonant magnetopolaron effects in GaAs/AlGaAs multiple quantum well structures

A detailed experimental study of electron cyclotron resonance (CR) has been carried out at 4.2 K in three modulation-doped GaAs/Al0.3Ga0.7As multiple quantum well samples in fields up to 30 T. A strong avoided-level-crossing splitting of the CR energies due to resonant magnetopolaron effects is observed for all samples near the GaAs reststrahlen region. Resonant splittings in the region of AlAs-like interface phonon modes of the barriers are observed in two samples with narrower well width and smaller doping concentration. The interaction between electrons and the AlAs interface optical phonon modes has been calculated for our specific sample structures in the framework of the memory-function formalism. The calculated results are in good agreement with the experimental results, which confirms our assignment of the observed splitting near the AlAs-like phonon region is due to the resonant magnetopolaron interaction of electrons in the wells with AlAs-like interface phonons. (C) 1998 Elsevier Science B.V. All rights reserved.

全永磁ECR离子源研究进展

Electron Cyclotron Resonance (ECR) ion source is regarded as the most efficient machine to produce stable multiple charge state ion beams. Because of the special characteristics, all-permanent magnet ECR ion sources have been widely adopted around the world to produce stable ion beams of multiple charge state with good repetition have been widely adopted around the world to produce stable ion beams of multiple charge state with good repetition and high duty factor for compact research platforms and ion beam implanters. In this paper, all-permanent magnet ECR ion sources developed at IMP are presented, and typical parameters and performances are discussed. The high charge state source, LAPECR2, is mainly used to produce intense high charge state ion beams, and the LAPECR1 source is designed to produce intense ion beams of medium and low charge state. An improved LAPECR1-M is specially designed to produce heavy metal ion beams of low charge state. These ECR ion sources have been adopted by different experimental terminals at IMP and, with their nice performance, many experimental studies could be possible. 中文文摘：ECR(电子回旋共振)离子源是产生稳定的强流多电荷态离子束流最有效装置。全永磁ECR 离子源因其独特的特点为很多中小型多电荷态离子束流实验平台与离子注入机等系统所采用，为后者产生重复性好、稳定性强的多电荷态离子束流。本文着重论述了中国科学院近代物理研究所研制的几台全永磁多电荷态ECR 离子源及其特性与典型性能，如能产生强流高电荷态离子束流的高性能全永磁离子源LAPECR2，能产生强流中 低电荷态离子束流的LAPECR1，能产生多电荷态重金属离子束流的LAPECR1-M 等。这些性能稳定的离子源为提高近代物理研究所相关试验平台的性能提供了关键的束流品质保障。

Effects of magnetic configuration on hot electrons in highly charged ECR plasma

To investigate the hot electrons in highly charged electron cyclotron resonance (ECR) plasma, Bremsstrahlung radiations were measured on two ECR ion sources at the Institute of Modern Physics. Used as a comparative index of the mean energy of the hot electrons, a spectral temperature, Tspe, is derived through a linear fitting of the spectra in a semi-logarithmic representation. The influences of the external source parameters, especially the magnetic configuration, on the hot electrons are studied systematically. This study has experimentally demonstrated the importance of high microwave frequency and high magnetic field in the electron resonance heating to produce a high density of hot electrons, which is consistent with the empirical ECR scaling laws. The experimental results have again shown that a good compromise is needed between the ion extraction and the plasma confinement for an efficient production of highly charged ion beams. In addition, this investigation has shown that the correlation between the mean energy of the hot electrons and the magnetic field gradient at the ECR is well in agreement with the theoretical models.中文摘要：ECR(电子回旋共振)离子源是产生稳定的强流多电荷态离子束流最有效装置。全永磁 ECR 离子源因其独特的特点为很多中小型多电荷态离子束流实验平台与离子注入机等系统所采用，为后者产生重复性好、稳定性强的多电荷态离子束流。本文着重论述了中国科学院近代物理研究所研制的几台全永磁多电荷态ECR离子源及其特性与典型性能，如能产生强流高电荷态离子束流的高性能全永磁离子源LAPECR2，能产生强流中低电荷态离子束流的LAPECR1，能产生多电荷态重金属离子束流的LAPECR1-M等。这些性能稳定的离子源为提高近代物理研究所相关试验平台的性能提供了关键的束流品质保障。

强流高电荷态全永磁ECR离子源LAPECR2的初步调试

研制成功了一台强流高电荷态全永磁ECR(Electron Cyclotron Resonance)离子源LAPECR2(Lanzhou All Permanent Magnet ECR Ion Source No.2)。该离子源在完成磁体装配后已成功在近代物理研究所320 kV高压平台上安装就位,与后束运线完成对接组装。离子源于2005年7月在14.5 GHz实现了第一次成功起弧,并引出较强的混合束流。目前离子源已与后束线以及部分实验终端完成了联调,在实验终端能够获得强流较高电荷态的离子束流。本文将着重论述该全永磁源的结构技术特点和主要参数指标。本文还着重论述了LAPECR2离子源在14.5 GHz微波功率馈入条件下的初步调试结果,在此基础上对束流向实验终端联调的实验结果进行了讨论,着重分析了影响束流引出与传输效率的主要因素。

超导ECR源SECRAL轫致辐射谱的测量

热电子在ECR(Electron Cyclotron Resonance)源中有着非常重要的作用,为了研究ECR源的工作参数(微波功率、磁场等)对热电子的影响,我们对SECRAL(Superconducting ECR ion source with Advanced design in Lanzhou)等离子体在轴向发出的轫致辐射谱进行了系统的测量。从测得的轫致辐射谱中我们得到用来衡量热电子能量的参考量——光谱温度Tspe,并且对ECR源的几个工作参数与Tspe的关系进行了讨论。

高性能全永磁ECR离子源LAPECR2的研制

研制了一台体积和重量都较大、设计性能较高的全永磁电子回旋共振(Electron cyclotron resonance, ECR)离子源LAPECR2(Lanzhou all permanent magnetic ECR ion source No．2)。该离子源将用于中国科学院近代物理研究所320 kV高压平台,为其提供强流高电荷态离子束流。LAPECR2的研制采用全新的全永磁磁体结构设计,通过采用高性能的NdFeB永磁材料、优化的磁结构设计以及精确的计算,实测源体的磁场参数能达到高性能ECR离子源的设计要求。离子源采用较高频率的14．5 GHz微波馈入加热等离子体,波导直接馈入离子源以增强馈入微波的稳定性与效率。此外,还大量采用了一些有利于提高离子源高电荷态离子产额的关键技术,如铝内衬等离子体弧腔、负偏压盘、铝制等离子体电极、三电极引出系统、辅助掺气等。

A latest developed all permanent magnet ECRIS for atomic physics research at IMP

Electron cyclotron resonance (ECR) ion sources have been used for atomic physics research for a long time. With the development of atomic physics research in the Institute of Modern Physics (IMP), additional high performance experimental facilities are required. A 300 kV high voltage (HV) platform has been under construction since 2003, and an all permanent magnet ECR ion source is supposed to be put on the platform. Lanzhou all permanent magnet ECR ion source No. 2 (LAPECR2) is a latest developed all permanent magnet ECRIS. It is a 900 kg weight and circle divide 650 mm X 562 mm outer dimension (magnetic body) ion source. The injection magnetic field of the source is 1.28 T and the extraction magnetic field is 1.07 T. This source is designed to be running at 14.5 GHz. The high magnetic field inside the plasma chamber enables the source to give good performances at 14.5 GHz. LAPECR2 source is now under commissioning in IMP. In this article, the typical parameters of the source LAPECR2 are listed, and the typical results of the preliminary commissioning are presented.

Commissioning test of LAPECR2 source on the 320kV HV platform

The high charge state all permanent Electron Cyclotron Resonance Ion Source (ECRIS) LAPECR2 (Lanzhou All Permanent magnet ECR ion source No.2) has been successfully put on the 320kV HV platform at IMP and also has been connected with the successive LEBT system. This source is the largest and heaviest all permanent magnet ECRIS in the world. The maximum mirror field is 1.28T (without iron plug) and the effective plasma chamber volume is as large as circle divide 67mm x 255mm. It was designed to be operated at 14.5GHz and aimed to produce medium charge state and high charge state gaseous and also metallic ion beams. The source has already successfully delivered some intense gaseous ion beams to successive experimental terminals. This paper will give a brief overview of the basic features of this permanent magnet ECRIS. Then commissioning results of this source on the platform, the design of the extraction system together with the successive LEBT system will be presented.

Production of highly charged ion beams with SECRAL

Superconducting electron cyclotron resonance ion source with advanced design in Lanzhou (SECRAL) is an all-superconducting-magnet electron cyclotron resonance ion source (ECRIS) for the production of intense highly charged ion beams to meet the requirements of the Heavy Ion Research Facility in Lanzhou (HIRFL). To further enhance the performance of SECRAL, an aluminum chamber has been installed inside a 1.5 mm thick Ta liner used for the reduction of x-ray irradiation at the high voltage insulator. With double-frequency (18+14.5 GHz) heating and at maximum total microwave power of 2.0 kW, SECRAL has successfully produced quite a few very highly charged Xe ion beams, such as 10 e mu A of Xe37+, 1 e mu A of Xe43+, and 0.16 e mu A of Ne-like Xe44+. To further explore the capability of the SECRAL in the production of highly charged heavy metal ion beams, a first test run on bismuth has been carried out recently. The main goal is to produce an intense Bi31+ beam for HIRFL accelerator and to have a feel how well the SECRAL can do in the production of very highly charged Bi beams. During the test, though at microwave power less than 3 kW, more than 150 e mu A of Bi31+, 22 e mu A of Bi41+, and 1.5 e mu A of Bi50+ have been produced. All of these results have again demonstrated the great capability of the SECRAL source. This article will present the detailed results and brief discussions to the production of highly charged ion beams with SECRAL.

A mechanism for enhanced photocatalytic activity of silver-loaded titanium dioxide

In this paper, silver-loaded TiO2 photocatalyst was prepared by photochemical impregnation method and characterized by transmission electron microscopy (TEM), diffuse reflectance spectra (DRS), photooxidation of phenol and photoreduction of Cr(VI). Electron paramagnetic resonance (EPR) was used to detect photoproduced paramagnetic radicals. The correlation of photocatalytic activity and photogenerated reactive species was discussed, and the mechanism of silver-loaded TiO2 for enhancement of photocatalytic activity was elucidated. The results show that deposited silver on TiO2 Surface acts as a site where electrons accumulate. The better separation between electrons and holes on the modified TiO2 surface allowed more efficiency for the oxidation and reduction reactions. The enhanced photocatalytic activity was mainly attributed to the increased amounts of O-2(.-) reactive species and surface Ti3+ reactive center on silver-loaded TiO2 photocatalyst. (C) 2004 Published by Elsevier B.V.

The enhancement of TiO2 photocatalytic activity by hydrogen thermal treatment

In this study, conventional TiO2 powder was heated in hydrogen (H-2) gas at a high temperature as pretreatment. The photoactivity of the treated TiO2 samples was evaluated in the photodegradation of sulfosalicylic acid (SSA) in aqueous suspension. The experimental results demonstrated that the photodegradation rates of SSA were significantly enhanced by using the H-2-treated TiO2 catalysts and an optimum temperature for the H-2 treatment was found to be of 500-600 degreesC. The in situ electron paramagnetic resonance (EPR) signal intensity of oxygen vacancies (OV) and trivalent titanium (Ti3+) associated with the photocatalytic activity was studied. The results proved the presence of OV and Ti3+ in the lattice of the H2-treated TiO2 and indicated that both were contributed to the enhancement of photocatalytic activity. Moreover, the experimental results presented that the EPR signal intensity of OV and Ti3+ in the H-2-treated TiO2 samples after 10 months storage was still significant higher than that in the untreated TiO2 catalyst. The experiment also demonstrated that the significant enhancement occurred in the photodegradation of phenol using the H-2-treated TiO2. (C) 2002 Elsevier Science Ltd. All rights reserved.

Bluish-white emission from radical carbonyl impurities in amorphous Al2O3 prepared via the Pechini-type sol-gel process

Many efforts have been devoted to exploring novel luminescent materials that do not contain expensive or toxic elements, or do not need mercury vapor plasma as the excitation source. In this paper, amorphous Al2O3 powder samples were prepared via the Pechini-type sol-gel process. The resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), photoluminescence (PL) excitation and emission spectra, kinetic decay, and electron paramagnetic resonance (EPR).

Tunable Luminescence in Monodisperse Zirconia Spheres

In this article, monodisperse spherical zirconia (ZrO2) particles with a narrow size distribution were prepared by the controlled hydrolysis of zirconium butoxide in ethanol, followed by heat treatment in air at low temperature from 300 to 500 degrees C. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric and differential thermal analysis (TG/DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, kinetic decay, and electron paramagnetic resonance were used to characterize the samples. The experimental results indicate that the annealed ZrO2 samples exhibit broad, intense visible photoluminescence. The annealing temperature is indispensable for the luminescence of the obtained ZrO2 particles. The emission colors of the ZrO2 samples can be tuned from blue to nearly white to dark orange by varying the annealing temperature.