Surface plasmon modulated nano-aperture vertical-cavity surface-emitting laser

We have fabricated surface plasmon modulated nano-aperture vertical-cavity surface-emitting lasers (VCSELs) from common 850 nm VCSELs using focus ion beam etching with Ga+ ion source. The far-field output power is about 0.3 mW at a driving current of 15 mA with a sub-wavelength aperture surrounded by concentric periodic grooves. The enhancement of transmission intensity can be explained by diffraction and enhanced fields associated with surface plasmon. This structure also exhibits beaming properties.

Experimental results of helicon sources

Helicon plasma source is known as an efficient generator of uniform and high density plasma. A helicon plasma source was developed for the investigation of plasma striping and plasma lens at the Institute of Modern Physics, CAS. In this paper, the characteristics of helicon plasma have been studied by using Langmuir four-probe and a high plasma density up to 3.9×1013 /cm3 has been achieved with the Nagoya type III antenna. In the experiment, several important phenomena have been found: (1) for a given magnetic induction intensity, the plasma density became greater with the increase of RF power; (2) the helicon mode appeared at the RF power between 300 W and 400 W; (3) the plasma density gradually tended to saturation as the RF power increased to the higher power; (4) a higher plasma density can be obtained by a good matching between the RF power and the magnetic field distribution. The key issue is how to optimize the matching between the RF power and the magnetic field. Moreover, some tests on the extraction of ion beam were performed, and the preliminary results were given. The problems which existed in the helicon ion source will be discussed and the increase in beam density will be expected by extraction system optimum.

Beam dynamics design of an RFQ for a planned accelerator, which uses a direct plasma injection scheme

To meet the requirements of providing high-intensity heavy ion beams the direct plasma injection scheme (DPIS) was proposed by a RIKEN-CNS-TIT collaboration. In this scheme a radio frequency quadrupole (RFQ) was joined directly with the laser ion source (LIS) without a low-energy beam transport (LEBT) line. To find the best design of the RFQ that will have short length, high transmission efficiency and small emittance growth, beam dynamics designs with equipartitioning design strategy and with matched-only design strategy have been performed, and a comparison of their results has also been done. Impacts of the input beam parameters on transmission efficiency are presented, too. (C) 2008 Elsevier B.V. All rights reserved.

Preparation and Optical Properties of Gold Nanowire Arrays

Gold nanowires with diameters (d) between,15 run and 200 urn and with length/diameter ratio of 700 were prepared in ion-track templates with electrode position method. The morphology and crystal structure of the gold nanowires were Studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The 200 nm (d) gold nanowires preferred orientation along the [100] direction were formed at the deposition voltage of 1.5 V (Without reference electrode). The optical properties of gold nanowire arrays embedded in ion-track templates were studied by UV-Vis spectrophotometer. There was a strong absorption peak at 539 nm for 45 nm (d) gold nanowire arrays. With the diameter of gold nanowires increasing, the absorption peak shifted to the longer wavelength. At last, the result was discussed combined with surface plasmon resonance of gold nanoparticles.

First results of SECRAL at 18GHz for intense beam production of highly charged ions

A Superconducting ECR ion source with Advanced design in Lanzhou (SECRAL) was successfully built to produce intense beams of highly charged ions for Heavy Ion Research Facility in Lanzhou (HIRFL). The ion source has been optimized to be operated at 28GHz for its maximum performance. The superconducting magnet confinement configuration of the ion source consists of three axial solenoid coils and six sextupole coils with a cold iron structure as field booster and clamping. For 28GHz operation, the magnet assembly can produce peak mirror fields on axis 3.6T at injection, 2.2T at extraction and a radial sextupole field of 2.0T at plasma chamber wall. A unique feature of SECRAL is that the three axial solenoid coils are located inside of the sextupole bore in order to reduce the interaction forces between the sextupole coils and the solenoid coils. During the ongoing commissioning phase at 18GHz with a stainless steel chamber, tests with various gases and some metals have been conducted with microwave power less than 3.2kW and it turned out the performance is very promising. Some record ion beam intensities have been produced, for instance, 810e mu A of O7+, 505e mu A of Xe20+, 306e mu A of Xe27+, 21e mu A of Xe34+, 2.4e mu A of Xe38+ and so on. To reach better results for highly charged ion beams, further modifications such as an aluminium chamber with better cooling, higher microwave power and a movable extraction system will be done, and also emittance measurements are being prepared.

Structure analysis of the SECRAL superconducting magnet system

An advanced superconducting ECR ion source named SECRAL has been constructed at Institute of Modern Physics of Chinese Academy of Sciences, whose superconducting magnet assembly consists of three axial solenoid coils and six sextupole coils with a cold iron structure as field booster and clamp. In order to investigate the structure of sextupole coils and to increase the structural reliabilities of the magnet system, global and local structural analysis have been performed in various operation scenarios. Winding pack and support structure design of magnet system, mechanical calculation and stress analysis are given in this paper. From the analysis results, it has been found that the magnet system is safe in the referential operation scenarios and the configuration of the magnet complies with design requirements of the SECRAL.

Measurements of bremsstrahlung spectra on SECRAL

The axial emitted bremsstrahlung spectra were measured on SECRAL (Superconducting ECR ion source with Advanced design in Lanzhou) using an HPGe detector. The spectral temperature T-spe was obtained from the linear fit of the spectra in the semi-log present. The evolution of T-spe with microwave power and magnetic field configuration is investigated in this paper.

A new axial injection beam line of the SFC

A new axial beam injection system is designed and being constructed at the HIRFL. It consists of 2 GLASSER lenses, 1 dipole, 5 quadrupoles and 3 solenoids. There are two beam line branches for 14.5GHz ECR ion source and 18.5GHz super conducting ECR ion source. Both transverse and longitudinal beam optics are improved in contrast with the old one. The layout, beam optics calculation results and further improved design are given.

Drift distance survey in direct plasma injection scheme for high current beam production

In a laser ion source, plasma drift distance is one of the most important design parameters. Ion current density and beam pulse width are defined by plasma drift distance between a laser target and beam extraction position. In direct plasma injection scheme, which uses a laser ion source and a radio frequency quadrupole linac, we can apply relatively higher electric field at beam extraction due to the unique shape of a positively biased electrode. However, when we aim at very high current acceleration such as several tens of milliamperes, we observed mismatched beam extraction conditions. We tested three different ion current at ion extraction region by changing plasma drift distance to study better extraction condition. In this experiment, C6+ beam was accelerated. We confirmed that matching condition can be improved by controlling plasma drift distance.

激光离子源用于A>170重丰中子新核素的研究

本文概述了 A > 170 质量区重丰中子同位素研究的主要工作和意义；介绍了 A > 170 重丰中子同位素合成、分离和鉴别方法；详细论述了激光离子源的原理、设计及其同传统离子源相比所具有的优越性；在文章结尾，设计了一个物理实验，实验目的在于：1）寻找 ~(181)Yb新核素；2）揭示天体物理学中~(180m)Ta 的产生问题。我们对反应截面进行了分析，并对产额进行了估计，证明了此实验设计的合理性，进而说明了带激光离子源的同位素分离器适用于产生截面很低的新核素和衰变研究。本文重点讨论了激光离子源的各方面问题：介绍了激光多步共振电离原理和激光离子源原理；具体分析了热毛细管式激光离子源元素选择性的产生及其影响的因素；讨论了在设计、加工过程中的具体问题；描述了所使用的激光技术；通过在线实验验证了热毛细管式激光离子源的元素选择性和分离效率。

新一代多电荷态离子源的研究

离子源发展存在两大热点问题：其一强流高电荷态离子的产生；其二强流金 属离子的产生。为了获得强流高电荷态离子，我们设计制造了全超导 ECR 离子 源 SECRAL（Superconducting ECR ion source with Advanced design in Lanzhou） ， 该离子源采用了全新的超导磁体结构形式，工作于 18～28GHz 的微波频率。根据 scaling laws 和实验经验，我们确定了 SECRAL 离子源所需要的约束磁场场形， 并针对新的磁体结构设想，通过 TOSCA 程序进行了详细的计算，成功地设计出 满足我们场形要求的超导磁体物理模型。据此，我们进一步进行了超导磁体的力 学结构分析，为磁体机械工艺设计提供了参考依据，保证了超导磁体结构设计的 可靠性。源体建成后，经过一系列的测试和调束实验，不但验证了我们的设计和 分析是合理的、可靠的，而且创造了许多项束流调试的新世界纪录，我们分别获 得了 810 A eμ O7+ 、730 A eμ Ar 11+ 、220 A eμ Ar 14+ 、73 A eμ Ar 16+ 、483 A eμ Xe 20+ 等束 流。为了获得强流中低电荷态金属离子束，我们尝试探索一种原理、结构、工作 模式全新的离子源－外部电子注入PIG离子源（E-PIG） 。目前，我们基本按照我 们的初期设想设计建造了 E-PIG离子源，设计中采用了外部电子枪注入电子、空 心阴极、特殊的场形等手段来提高金属离子的电荷态和流强。经过初步的起弧调 试，我们发现在初期的设计中还存在一些问题亟待进一步整改。

2.45GHzECR离子源及ECR离子源的磁场设计和计算

本文第一章介绍了高电荷态电子加旋共振（ECR）离子源发展情况，对其发展的几个方向作了一定的讨论，着重介绍了IMP高电荷态ECR离子源。第二章讨论了ECR离子源的加热原理，并讨论了低电荷态ECR离子源的加热情况。在ECR离子源中，磁场有着重要的作用，磁场场面设计和计算也ECR离子源物理设计中关键的一环。第三章讨论了ECR离子源的磁场设计和计算。在设计、加工几例磁场系统的基础上，利用计算与实测结果对离子源的磁场设计和计算作了一定程度的讨论。并使用二维POSSION、三维TOSCA程序对超导离子源进行了初步设计和计算。第四章着重讨论了两个2.45GHzECR离子源实验台。描述了一台2.45GHz单电荷态ECR离子源的结构与应用。介绍了其微波系统与磁场结构，并对该离子源的一些问题进行了讨论。在微波输入功率约600瓦，引出高压22KV，引出孔径为φ6mm，引出间隙6mm时，该离子源的总束流I(H_1~+ + H_2~+ + H_3~+)为 90mA。同时，介绍了一台2.45GHz多电荷态ECR实验台的设计。

ECR离子源高真空微调针阀控制系统

本论文首先介绍ECR（电子回旋共振）离子源的基本原理及其发展，在此基础上讲述了近物所的14.5GHzECR离子源的结构和特点。本论文主要内容是介绍所研制的适用于30KV高压端的ECR离子源高真空微调针阀控制系统。此系统被控对象是位于ECR源上的高真空微调针阀，它与地面之间有20～30KV的电位差。论文中首先阐述此控制系统研究的背景，并对ECR离子源电气参数控制的特点进行了说明。根据被控对象的情况以及对系统提出的指标，详细讲述了此控制系统的软、硬件实现。硬件包括步进电机、步进电机驱动器、轴编码器等。软件包括译码编程。然后从总体介绍此控制系统的功能结构，再分步讲述发射器、接受器、译码等各功能模块的实现过程。此控制系统的最大特点是使用光路实现高压绝缘，这为解决位于ECR离子源高压端器件的控制问题提出新思路。本系统的光路采用红外线发射接收系统，以空气为传输介质，依据光信号的有无接收控制信息，此方式效果好、易于实现。在系统中，使用光路传输装置定位，聚集透镜聚集，增加信号强度，提高抗干拢能力。而且此光路传输系统价格便宜，易于实现，可靠性好。在整个控制系统方案调研期间，对各种控制方式进行了比较和实验，在此基础上，确定了一个比较经济实用和具有高可靠性的方案。经过设计电路原理图、绘制印制线路板、加工印制线路板、购买元器件、组装电路后，首先成功地进行了离线调试，最后，将整个系统模拟实际环境进行调试实验。整个系统实现了稳定可靠的工作，达到了预期的设计指标，精度好于要求的千分之一。由于时间紧张和条件的限制，该系统还未在现场设备上进行实验。因此，在今后的工作中，此控制系统还需要在条件具备时，在现场设备上进行实验和考验。此外，为满足国家大科学工程兰洲重离子冷却储存环的要求，我参与了在14.5GHz ECR离子源上进行afterglow工作模式的实验，首次产生了高电荷态脉冲束流Ar~(11+)和Ar~(12+)。论文最后一部分给出了初步实验结果，并对结果进行了分析和解释。

ECR离子源发射度探测器的研制

成功研制一套适合于ECR离子源引出束流发射度测量的探测器ESS（Electric-SweeP Scanner）。该探测器主要由测量探头、机械驱动装置、计算机控制及数据获取系统组成。ESS探测器所采用的测量方法是双狭缝加电扫描法，具有速度快、精度高，能够比较直观的反映束流的发射度相图、相空间密度分布等特点，是目前ECR离子源引出束流发射度测量的有效手段。本论文对发射度探测器ESS的原理、结构及物理和技术设计作了较详细的描述，并给出了相应的设计图纸及数值模拟结果。最后，利用Ess探测器对LECR3（Lanzhou No.3）离子源引出的04＋离子束的发射度作了初步测量。当04＋引出束流为343μA日寸，初步测量所得水平方向的发射度为227mm·mrad（约90％束流），并给出了相应的束流发射度相图和束流相空间密度分布。