中能重离子在生物组织中产生的核碎片

In heavy ion therapy and radiation biological effects the nuclear.fragments from the heavy ion collisions may cause a significant alteration of.the radiation field. Nuclear collision between beam particles and tissue nuclei.occurring along the penetration path of high-energy ions in tissue or.biological-equivalent material causes a loss of primary beam particles and.produces lower Z projectile fragments. As a consequence, the dose distribution along the beam path is different as compared to the dose profile, which would result from the passage of primary ions in absence of nuclear reactions. In particular, the lower-Z fragments, which have longer ranges than the primary particles, cause an additional dose distribution beyond the Bragg peak. Furthermore, the biological effect of the reaction products is different from the primary ions and has to be included in the calculation of the total biological effects, especially for the target volume. The importance of these.effects generally increases as a function of the beam energy (or penetration depth). The physical models used in therapy planning and biological material.codes have to take into account these effects and therefore require detailed.knowledge of the fragmentation processes in tissue-equivalent. Fragmentation reactions have been extensively studied for many years. Recently, to study the effect of heavy ions on life and fragments produced by heavy ions on life is getting concern of nuclear scientists of many countries for radiotherapy using accelerator and protection exploring space. So far, only a few sets of experimental data on fragmentation of middle-energy light ions in tissue-equivalent material are available. For the reason, we investigated angular distribution of the fragments produced by 55MeV/u 40Ar17+ ions through 1.5mm lucite. The results show that these fragments concentrate to a very small angle region at forward direction. The fragments lower Z than primary beams reduce sharply with the angle increase. The angular.distribution of proton is wider and its intensity is more intensive than that of.other fragments at the same angle. The spread of primary beam is quite small..The dose of primary beam is much larger than the total dose of all fragments.at different angles. It shows that the extending effect of fragments has only.small contribution to dose, but influence of the extending effect on biology.should be have more investigation..The fragments at different depths of absorber were produced by 62.8.MeV/u secondary 12C ions from 80MeV/u 20Ne ions through target of 2mm Be and degrader of 1mm Al at RIBLL. The results show that the fragment yield increases and then saturated with the depth increases, while the primary beams exponentially decayed. However, these fragments are.disadvantageous to tumor therapy with heavy ions. So, the dose contribution.from the fragments must be investigated for heavy ion therapy. In the paper,.fragment effect on dose-depth in calculation was developed, the calculated.results of dose-depth coincides well with experimental data. But the method.must be proved by more experiments for extensive application.The experimental results of fragments produced by heavy ions passing tissue-equivalent suggest that light ions can be used for therapy to reduce fragmentation effect, but heavier ions can be used for breeding to boost.mutation efficiency. The method monitoring dose was explored for biological effects and heavy ion therapy. A formula was given for correcting ion recombination in.dose measurement. A research on erformance of control system shows the.responsive velocity to switch beams is very important to treatment result;.otherwise therapy dose is not equal to measurement dose. The angular distribution of emitted neutron in experimental area was measured. The neutron dose can be negligible in heavy ion therapy as.compared with beam dose. In a word, some valuable data were built up through the experimental and theoretical research on fragmentation effect, which is useful to

本项目以研究中能重离子在生物材料中核碎片的成份、能量、强度、角分布为实验内容，结合理论计算更完善地解决重离子在生命科学应用中的剂量及其来源。此项目的研究结果可用于重离子浅层治疗中，从而使治疗剂量在考虑核碎片剂量后更为精确，这是由于核碎片剂量占总剂量的20%以上。另外实验的结果是其它相关研究在更深层次研究的基础。