标题： 由紫外光而非电子撞击产生的等离子体 显示英文标题

标题： Plasmas generated by ultra-violet light rather than electron impact

摘要： 我们分析了平面和圆柱两种几何结构下的无碰撞等离子体，该等离子体由一个内层区域组成，在该区域内通过紫外光照射产生粒子，以及一个没有粒子产生的外层未照射区域。内层生成的离子向外流过外层区域并进入壁面。我们首先求解该系统的稳态，先是在德拜长度 ${\lambda}_D$ 为零且存在解析解的准中性状态下，然后在一般情况下，后者我们通过数值方法求解。在一般情况下，双层在被照射区域和未照射区域的交界处形成，一个近似准中性的等离子体将双层与壁鞘连接起来；在平面几何中，离子以略高于玻姆速度 $c_s$ 的速度穿过准中性部分。尽管系统简单，但具有两个新特性：不需要反向流动离子和电子的双层，以及其中离子以至少玻姆速度沿直线运动的准中性等离子体。最后，我们总结了对该系统的渐近解，并建议如何在实验室中扩展和验证我们的理论结论。 显示英文摘要

摘要： We analyze, in both plane and cylindrical geometries, a collisionless plasma consisting of an inner region where generation occurs by UV illumination, and an un-illuminated outer region with no generation. Ions generated in the inner region flow outwards through the outer region and into a wall. We solve for this system's steady state, first in the quasi-neutral regime (where the Debye length ${\lambda}_D$ vanishes and analytic solutions exist) and then in the general case, which we solve numerically. In the general case a double layer forms where the illuminated and un-illuminated regions meet, and an approximately quasi-neutral plasma connects the double layer to the wall sheath; in plane geometry the ions coast through the quasi-neutral section at slightly more than the Bohm speed $c_s$. The system, although simple, therefore has two novel features: a double layer that does not require counter-streaming ions and electrons, and a quasi-neutral plasma where ions travel in straight lines with at least the Bohm speed. We close with a pr\'{e}cis of our asymptotic solutions of this system, and suggest how our theoretical conclusions might be extended and tested in the laboratory.