Development of a new ion-guide with use of magnetic field

离子导流技术是结合同位素在线分离器应用于核谱分析的一种新技术。该技术的原理是，在保持单电荷状态的情况下，停止反应产物反冲出目标，并在氦气池中热化，离子被气流带入真空，然后被分离器加速和质量分离。离子导引的优点是化学性质无关，分离速度快。然而，主要的缺点是，1)产量有限，2)光束质量差，3)“等离子体效应”（电池中主光束的存在会捕获离子）。对于第2点，我们已经开发了一种冷却装置，SPIG（射频六极离子束波导），这已经成为一种标准技术。目前工作的目的是在第1点和第3点。点1)的根源在于气槽的尺寸，其厚度约为1cm，相应的停止能力为10 keV/u。由于输送仅由g…作为流动进行，因此很难增加尺寸。我们建议在电池（RF -guide）中施加直流和射频叠加的电场，其中离子完全受电场控制。它允许使用一个大的电池，例如，2米长，对应于5 MeV/u的停止能力，因为直流电场保持快速提取和射频电场防止扩散损失到墙壁。这种大的停止能力也有效到点3)。射频波导可以与射弹碎片分离器耦合，其中主光束不照射气室。本文研究了利用射频引导技术在大型氦气电池中离子的有效输运。我们还制造了一种具有非常细间距的RF电极漏斗结构，细至0.3 mm，允许使用相对较高的150 Torr压力。虽然在本工作中没有对磁场的使用进行测试，但我们确信它对进一步提高电池的有效停止能力是有效的。少

The ion-guide is a novel technique which has been used for nuclear spectroscopy combined with an on-line isotope separator. The principle of the technique is that reaction products recoiling out of the target are stopped and thermalized in a He gas cell while keeping a singly charged state, the ions are carried by gas flow to vacuum, and then accelerated and mass separated by a separator. The advantages of the ion-guide are chemical-property independence and fast separation. There are, however, major drawbacks, i.e., 1) limited yield, 2) poor beam quality, 3) "plasma effect" (presence of primary beam in the cell traps ions). For the point 2), we have developed a cooling device, SPIG (RF sextupole ion beam guide), which has become a standard technique.The aim of the present work is at the points 1) and 3). The origin of the point 1) is in the size of gas cell, which is about 1cm in thickness, and corresponding stopping capability of 10 keV/u. Since the transport is carried only by the g … More as flow, it is hard to increase the size. We have proposed to apply an electric field of a superposition of DC and RF into the cell (RF ion-guide) where ions are totally under control of the field. It allows to use a large cell, e.g., 2 m in length which corresponds to a stopping capability of 5 MeV/u, since the DC electric field keeps fast extraction and the RF electric field protects from diffusion loss to the wall. This large stopping capability also effective to the point 3). The RF ion-guide can be coupled with a projectile fragment separator where the primary beams do not irradiate the gas cell.The present work showed effective transport of ions in a large He gas cell by the RF ion-guide technique. We have also fabricated a funnel structure of RF electrodes with very fine pitch, as fine as 0.3 mm, which allows to use a relatively high pressure of 150 Torr. Though the use of a magnetic field was not tested in the present work, we are certain that it will effective for further increase of effective stopping capability of the cell. Less