Development of an irradiation system of monochromatic photons (50-1000 eV) for wet biological samples

所有电离辐射的能量主要消耗在低能二次电子的动能上。由于这些电子产生的电离和激发被认为是诱发大多数生物效应，使用低能电子的研究是必不可少的，从根本上阐明辐射生物效应的机制。然而，由于极端的技术困难，低能电子对活体生物样品的照射实际上是不可能的。代替被所有材料非常强烈地吸收的低能电子的直接照射，由单色低能光子通过光电效应在样品中产生的低能电子可以用作低能电子的来源。因此，我们制作了一个特殊的系统，用于照射250至1000 eV的低能光子，并通过差分泵浦系统将其安装在BL-12 A（光子工厂）。该系统由氦光路、辐照室、XZ扫描平台和气体处理系统组成。我们在1995年和1996年都有一周的机器时间。对系统的基本性能进行了测试，并进行了两次哺乳动物细胞的辐照试验。因此，我们已经获得了有关该系统的基本信息，并知道如何充分处理，以便在下一步进行实验。

All ionizing radiations dissipate energy mainly to the kinetic energy of low-energy secondary electrons. Since the ionizations and excitations produced by these electrons are believed to induce most biological effects, studies using low-energy electrons are indispensable for a fundamental elucidation of the mechanism of radiation biological effects. However, the irradiation of low-energy electrons on living biological samples is practically impossible because of extreme technical difficulties. Instead of the direct irradiation of low-energy electrons, which are very strongly absorbed by all materials, low-energy electrons produced in samples by monochromatic low-energy photons through the photoelectric effect can be used as a source of low-energy electrons. We thus made a special system for the irradiation of low-energy photons from 250 to 1000 eV,and installed it at BL-12A (Photon Factory) through a differential pumping system. The system consists of a He path, an irradiation chamber, an XZ stage for scanning irradiation and a gas-handling system. We had one-week of machine time in both 1995 and 1996. We measured the basic performances of the system, and carried out two trial experiments for the irradiation of mammalian cells. We have thus obtained basic information concerning the system and know how to handle sufficiently to perform experiments in the next step.