EXPERIMENTAL NANODOSIMETRY

最近的生物学研究支持这样一种观点，即近距离 纳米量级的相互作用可能是导致 电离辐射产生的生物损伤。到目前为止， 在这个水平上的能量分布可以计算和推断，但是 不能通过实验测量。一种新的仪器，设计并实现了 在该中心开发的项目显示了实现这一目标的能力。 这个新设计的无壁正比计数器正在进行 建筑。这一设计是基于之前生产的一种常规 有墙的计数器称为UMC(超小型计数器)，它已经 在单粒子能量测量中被证明是成功的 模拟组织当量尺寸下的沉积分布约为 10纳米，远远低于之前实现的任何一种。新的无墙设计 将为这些高LET辐射提供更准确的光谱 他们的光谱被所谓的墙效应扭曲得最严重，例如 中子。与联华电子不同的是，该计数器可以精确校准。 然后它将被用来提供第一个实验测定 中子在纳米级位置的电离分布。有了这个 计数器将有可能对全范围的 RARAF设施中可用的单能中子，包括新的 低能中子设施，站点大小为10纳米或更大。量测 脉冲高能放射治疗束光中子污染的研究 也是有可能的。这些测量结果可以反过来提供固体 风险评估在医疗卫生领域应用的实验基础 健康物理学的应用。

Much recent biological research supports the view that close range interactions, of the order of nanometers, can be a dominant factor in the production of biological damage from ionizing radiation. Until now, energy distributions at this level could be calculated and inferred, but could not be measured experimentally. A new instrument, designed and developed in this Center displays the capability of achieving this goal. This newly designed wall-less proportional counter is in process of construction. The design is based on a previously produced conventional walled counter called the UMC (ultra-miniature counter) which has been shown to be successful in the measurement of single-event energy deposition distributions at simulated tissue equivalent sizes of about 10 nm, far lower than any previously achieved. The new wall-less design will provide much more accurate spectra for those high LET radiations whose spectra are most distorted by the so-called wall effect, such as neutrons. This counter, unlike the UMC, can be calibrated accurately. It will then be used to provide the first experimental determination of neutron ionization distributions in nanometer-size sites. With this counter it will be possible to do measurements on the full range of monoenergetic neutrons available at the RARAF facility, including the new low energy neutron facility, at site sizes 10 nm and larger. Measurement of photoneutron contamination from pulsed high energy radiotherapy beams is also possible. These measurements can in turn supply a solid experimental base for application of risk assessment in medical and health physics applications.