Sortais P, Lamy T, Médard J, Angot J, Latrasse L, Thuillier T
Laboratoire de Physique Subatomique et de Cosmologie de Grenoble, UJF-CNRS/IN2P3-INPG, 53, rue des Martyrs, 38026 Grenoble Cedex, France.
Rev Sci Instrum. 2010 Feb;81(2):02B314. doi: 10.1063/1.3272878.
In order to drastically reduce the power consumption of a microwave ion source, we have studied some specific discharge cavity geometries in order to reduce the operating point below 1 W of microwave power (at 2.45 GHz). We show that it is possible to drive an electron cyclotron resonance ion source with a transmitter technology similar to those used for cellular phones. By the reduction in the size and of the required microwave power, we have developed a new type of ultralow cost ion sources. This microwave discharge system (called COMIC, for COmpact MIcrowave and Coaxial) can be used as a source of light, plasma or ions. We will show geometries of conductive cavities where it is possible, in a 20 mm diameter chamber, to reduce the ignition of the plasma below 100 mW and define typical operating points around 5 W. Inside a simple vacuum chamber it is easy to place the source and its extraction system anywhere and fully under vacuum. In that case, current densities from 0.1 to 10 mA/cm(2) (Ar, extraction 4 mm, 1 mAe, 20 kV) have been observed. Preliminary measurements and calculations show the possibility, with a two electrodes system, to extract beams within a low emittance. The first application for these ion sources is the ion injection for charge breeding, surface analyzing system and surface treatment. For this purpose, a very small extraction hole is used (typically 3/10 mm for a 3 microA extracted current with 2 W of HF power). Mass spectrum and emittance measurements will be presented. In these conditions, values down to 1 pi mm mrad at 15 kV (1sigma) are observed, thus very close to the ones currently observed for a surface ionization source. A major interest of this approach is the possibility to connect together several COMIC devices. We will introduce some new on-going developments such as sources for high voltage implantation platforms, fully quartz radioactive ion source at ISOLDE or large plasma generators for plasma immersion, broad or ribbon beams generation.
为了大幅降低微波离子源的功耗，我们研究了一些特定的放电腔几何结构，以便将工作点降低到微波功率1瓦以下（在2.45吉赫兹）。我们表明，使用类似于手机所用的发射机技术来驱动电子回旋共振离子源是可行的。通过减小尺寸和所需的微波功率，我们开发了一种新型的超低成本离子源。这种微波放电系统（称为COMIC，即紧凑型微波和同轴型）可用作光、等离子体或离子源。我们将展示导电腔的几何结构，在直径20毫米的腔室内，有可能将等离子体的点火功率降低到100毫瓦以下，并确定约5瓦的典型工作点。在一个简单的真空室内，很容易将源及其引出系统放置在任何位置并完全处于真空状态。在这种情况下，观察到电流密度为0.1至10毫安/平方厘米（氩气，引出4毫米，1毫安等效电流，20千伏）。初步测量和计算表明，采用双电极系统有可能以低发射度引出束流。这些离子源的首个应用是用于电荷增殖的离子注入、表面分析系统和表面处理。为此，使用了一个非常小的引出孔（对于2瓦高频功率下引出3微安的电流，通常为3/10毫米）。将展示质谱和发射度测量结果。在这些条件下，在15千伏（1σ）时观察到的值低至1π毫米毫弧度，因此非常接近目前表面电离源所观察到的值。这种方法的一个主要优点是可以将多个COMIC装置连接在一起。我们将介绍一些正在进行的新进展，例如用于高压注入平台的源、ISOLDE的全石英放射性离子源或用于等离子体浸没的大型等离子体发生器、宽束或带状束的产生。
