重离子束的Bragg峰定位于麦粒的自由基探针技术

为了实现定点定位诱变，提出了一种利用ＥＳＲ波谱术对离子束Ｂｒａｇｇ峰在麦粒中的定位方法，即自由基探针技术，采用该技术有效地测定出２１ＭｅＶ／ｕ氮离子束的Ｂｒａｇｇ峰位于小麦胚部，注入深度不超过１．０±０．２ｍｍ，而４８ＭｅＶ／ｕ氮离子束贯穿全麦粒，不能实现定点定位诱变。     

用CR—39固体径迹探测器测定重带电粒子的Bragg峰位

采用ＣＲ－３９固体径迹探测器，根据辐射损伤密度沿粒子的径迹分布规律，测定了经３、４ｃｍ空气降能和φ１ｍｍ孔准直的α粒子（５．１５ＭｅＶ）的Ｂｒａｇｇ峰位。对于通过３ｃｍ空气后能量降至～１．２ＭｅＶ的α粒子，在ＣＲ－３９中的Ｂｒａｇｇ峰位大约在７μｍ深度处，理论计算值在６．１４μｍ，实验值与理论值符合得较好。     

用CR－39固体径迹探测器测定重带电粒子的Bragg峰位

采用ＣＲ－３９固体径迹探测器，根据辐射损伤密度沿粒子的径迹分布规律，测定了经３、４ｃｍ空气降能和φ１ｍｍ孔准直的α粒子（５．１５ＭｅＶ）的Ｂｒａｇｇ峰位。对于通过３ｃｍ空气后能量降至～１２ＭｅＶ的α粒子，在ＣＲ－３９中的Ｂｒａｇｇ峰位大约在７μｍ深度处，理论计算值在６．１４μｍ，实验值与理论值符合得较好。     

75MeV／u ^12C离子Bragg曲线及黑色素瘤细胞失活的测量

用双电离室法测定了ＨＩＲＦＬ提供的７５ＭｅＶ／ｕ ＾１２Ｃ离子经不同厚度降能片后的相对剂量，将降能片厚度等效为组织等效材料－水中的深度，得到了碳离子在水介质中的Ｂｒａｇｇ曲线，与计算的Ｂｒａｇｇ曲线进行了比较。同时测定了离子经不同厚度降能片后对黑色素瘤（Ｂ１６）细胞的失活效应，得到了离子束在不同贯穿深度上的Ｂ１６细胞存活数据。     

50MeV/u12C6+离子辐照B16细胞氧效应研究

实验以体外培养的小鼠Ｂ１６黑色素瘤细胞为材料,在５０ＭｅＶ／ｕ ＾１２Ｃ＾６＋离子的展宽Ｂｒａｇｇ峰区辐照细胞,得到的结果是这种离子的ＯＥＲ值为１．２５。说明这种能量的离子具有低的氧效应。     

75MeV/u￣(12)C离子Bragg曲线及黑色素瘤细胞失活的测量

用双电离室法测定了ＨＩＲＦＬ提供的７５ＭｅＶ／ｕ１２Ｃ离子经不同厚度降能片后的相对剂量，将降能片厚度等效为组织等效材料一水中的深度，得到了碳离子在水介质中的Ｂｒａｇｇ曲线，与计算的Ｂｒａｇｇ曲线进行了比较。同时测定了离子经不同厚度降能片后对黑色素瘤（Ｂ１６）细胞的失活效应，得到了离子束在不同贯穿深度上的Ｂ１６细胞存活数据。     

离子束混合形成氮化钛膜的摩擦和光学性能

用载能氮离子束轰击纯铁镀钛膜样品，成功地形成了金黄色氮化钛薄膜。结果表明：注入剂量为０．５×１０＾１７ Ｎ＾＋／ｃｍ＾２的混合样品表面颜色与纯金类似；氮离子束混合样品表面显微硬度及耐磨性都远优于纯铁基体，且随离子剂量的增加，混合样品的表面硬度和耐磨性也提高。     

重离子束均匀度的测定及治癌束流成形的模拟试验

采用５０μｍ厚聚碳酸酯薄膜，利用核径迹测技术测得φ４０ｍｍ的２５ＭｅＶ／ｕ＾４０Ａｒ＾１４＋离子束的均匀度在散焦情况下为３２．７％，在Ｄ“散焦＋样品旋转”情况下为５２．４％。还采用多层聚碳酸酯薄膜组件作为肿瘤块等效材料，进行了重离子束治癌束流成形模拟试验。     

室内空气中^210Pb浓度的初步研究

本文报道了我国１例室内空气中＾２１０Ｐｂ的浓度测定结果。１９９２年１－９月采集了一礼堂风空气样品，测得＾２１０Ｐｂ浓度为３．７４－６．２４ｍＢｑ．ｍ＾－３，平均值为４．６６ｍＢｑ．ｍ＾－３。作为对照，１９９２年２－１１月彩集了阳台上的室外空气，测得＾２１０Ｐｂ浓度为１．２２－２．６６ｍＢｑ．ｍ＾－３，平均值为１．８４ｍＢｑ．ｍ＾－３。室内，外空气中的＾２１０Ｐｂ浓度之比约为２．５：１。     

吉林省土壤中天然放射性核素含量调查研究

本文报道吉林省土壤中天然放射性核素含量的调查方法和结果。基本与环境陆地γ辐射剂量率调查同位布点，全省共采集土壤样品４７８个。测量采用放化分析方法。调查结果表明，吉林省土壤中天然放射性核素含量按面积和点加权均值分别为：＾２＾３＾８Ｕ，２５．２和２６．５Ｂｑ．ｋｇ＾－＾１；＾２＾２＾６Ｒａ，３５．６和３７．１Ｂｑ．ｋｇ＾－＾１；＾２＾２＾３Ｔｈ，４７．９和４９．５Ｂｑ．ｋｇ＾－＾１，４０Ｋ，６９９．９     

Extending Bragg peak of heavy ion beam and melanoma cell inactivation measurement

A rotating range modulator was designed and manufactured.which is applied to extend Bragg peak of heavy ion beam.Bragg curves of 75MeV/u ^16O and 75MeV/u ^12C ion beams through this range modulator were measured respectively and two evident spread-out Bragg peaks corresponding to the modulated beams above are shown.In addition,inactivation effect of the modulated 75MeV/u ^16O ion beam at nine different penetration depths on melanoma cells(B16) was measured.Results indicate that lethal effects at the spread-out Bragg peak region are larger than at the plateau of the particle beam entrance.     

重离子束水吸收剂量的电离法实验研究

重离子束水吸收剂量是开展重离子束治疗最基本的物理量。在开展重离子束水吸收剂量的量值复现研究前，需用间接测量的方法开展相关工作以熟悉实验条件。本文用传统电离法开展了能量400 MeV/u、具有6 cm展宽Bragg峰的碳离子束的水吸收剂量测量研究，并评价了重离子束条件下的相关电离室的极化、离子复合修正因子。在电离室的极化和离子复合修正项方面，重离子束水吸收剂量测量的相关不确定度分量显著大于60Co γ辐射水吸收剂量的相关值。用不同电离室测量重离子束水吸收剂量的结果在不确定度允许的范围内符合。以电离室测量为基础，开展更深入的包括量热法绝对测量在内的辐射剂量学研究，对进一步优化重离子束水吸收剂量测量的不确定度至关重要。     

Experimental Study for Absorbed dose to Water of Heavy Ion Beam via Ionization Method

The absorbed-dose to water of heavy ion beam is a fundamental quantity for heavy ion therapy. It is necessary to perform the relevant work with in-direct measurement prior to the study of the reproduction for the absorbed-dose to water of heavy ion beam. The absorbed-dose to water of a carbon ion beam, whose incident energy was 400 MeV/u and spread-out Bragg peak was 6 cm, was studied with conventional ionization method. The correction factors of polarity and ion recombination for the ionization chambers were evaluated with the incident heavy ion beam. The uncertainty components for the measurement of the absorbed-dose to water of heavy ion beam are significantly larger than that of the 60Co γ radiation, in terms of the corrections for the polarity and ion recombination of the ionization chambers. The absorbed-dose to water of heavy ion beam deduced from different ionization chambers is consistent within the acceptance of uncertainty. Based on the measurement with ionization chambers, it is crucial to conduct more intensive research activities of radiation dosimetry including the absolute measurement with calorimetric facility, with the purpose of further optimizing the uncertainty in the measurement for the absorbed-dose to water of heavy ion beam.     

中能碳离子束对不同贯穿深度上黑色素瘤B16细胞的辐照存活效应

测量了49．30MeV/u及经脊形过滤器展宽的Bragg峰的74.55MeV/u^12C离子束在不同贯穿深度上辐射后黑色素瘤B16细胞的存活率。结果显示,在以存活为终点的B16细胞生物学效应与碳离子束能量沉积同步增大。即Bragg或展宽的Bragg峰区内细胞存活率远低于离子束入射或出射通道处的细胞存活率。通过实验测量与剂量平均LET结合的线性平方模型理论计算存活曲线的比较,发现在实验测量误差范围内两者符合较好。提示：剂量平均LET结合线性平方模型可能是预测中能重离子束贯穿深度上B16细胞存活效应的一种有效的方法。     

聚焦重离子束溅射制备同位素靶的材料利用率及均匀性研究

研究了聚焦重离子束溅射制备同位素靶的材料利用率和均匀性。通过实验确定了两种溅射距离(7 mm和14 mm)下沉积靶的纵向和横向厚度分布,确定了提高靶均匀性的有效方法——基衬公转和沉积1/2厚度后基衬调头,确定了匹配材料利用率和均匀性的最佳几何参数。制备了5种同位素氧化物靶和9种高熔点金属同位素靶,应用于核物理测量实验。实验表明,源-衬距离为7 mm和14 mm时,在9 mm×10 mm成膜区域内,基衬中心距靶(源)材料水平界面垂直距离为9 mm和11 mm时可获得均匀的靶膜和最高的材料利用率。     

Heavy ion beam induced phenomena in polytetrafluoroethylene

This paper describes the results on thermal and chemical analysis of polytetrafluoroethylene (PTFE) film stack after high-energy heavy ion beam irradiation under atmospheric fields at room temperature. After high-energy C⁶⁺ ion beam irradiation, the PTFE film stack was separated one by one, and then the various measurements such as differential scanning calorimetric (DSC) analysis and solid-state ¹⁹F magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy were performed to get information of the chemical reaction and structural change at the localized positions. By ion beam irradiation for PTFE at room temperature, it is suggested that the abnormal phenomena due to the change of morphology could be observed by DSC analysis. In the solid-state ¹⁹F-MAS-NMR spectroscopy of ion irradiated PTFE film including Bragg peak region, several new signals were observed besides the intense peak of -CF₂- at −124 ppm. The detected new signals in ion irradiated PTFE should be due to the changed chemical structures. The signals, which are assigned, to the tertiary carbon group with branching site (Y-type crosslinking site), perfluoro-propylene site and chain end methyl site were directly detected, though it was under the oxidation condition. Thus, although it was under the oxidation condition, the branching or crosslinking reaction was taken place with the chain scission in the matrix. Moreover, the branched chain length would become short, compared with EB-crosslinked PTFE. Hence, it could be suggested that the irradiation of heavy ion beam induced large amounts of intermediate species, compared with EB or γ-ray irradiation, and then, those would be reacted with each other in the localized area. Especially, in region of the Bragg peak, the ion beam induced more large amounts of intermediate species than in the other region.     

Performance of an acousto-optic Bragg cell under ion microbeam irradiation

An acousto-optic (AO) deflector composed of PbMoO₄ was exposed to 4 MeV protons while operating under Bragg angle conditions. An ion beam in air of 1 mm width was directed normal to the crystal face and laser beam. Between exposures, the approximately 13 mm × 8.5 mm AO deflector was mechanically translated in two dimensions in front of the fixed ion beam. The AO diffraction efficiency was mapped and was observed to change as a function of ion beam location and dose rate. These effects are attributed to the induced change in the temperature distribution of the crystal, which changed the sonic velocity and refractive index. Similar effects were observed when the ion beam was directed at the acoustic transducer.     

TEPC壁对重离子束微剂量学测量及相对生物学效应计算的影响

组织等效正比计数器（TEPC）广泛应用于重离子束微剂量学测量，提供用于计算相对生物学效应（RBE）的基础数据。为研究TEPC壁对重离子束微剂量学测量及RBE计算的影响，在蒙特卡罗（MC）模拟中引入理想组织等效正比计数器（Ideal-TEPC），精确计算得到碳离子束不同水等效深度处的微剂量学量及RBE。Ideal-TEPC和常规TEPC的计算结果表明：TEPC壁会使碳离子束产生较大的辐射场畸变，且会使TEPC测量结果及RBE计算结果产生较大偏差，该偏差随贯穿深度的增加而增大。将TEPC壁视为具有固定水等效厚度的水层可在数值上抵消TEPC壁对RBE计算的影响，但在展宽Bragg峰（SOBP）后端会产生过修正现象。Ideal-TEPC结合MC模拟能有效避免TEPC壁效应及TEPC壁引起的辐射场畸变对重离子束微剂量学量和RBE计算的影响。     

Thermo-mechanical studies for the slit in the emittance measurements

A double-slit type monitor will be used in the emittance measurements at the exit of the first tank of the drift tube linac in the China Spallation Neutron Source where the H^? ion energy is 21.67 MeV. The rapid energy deposition in the first slit may generate a rapid temperature rise and high thermal stress, which may damage the slit plate. This article presents detailed thermo-mechanical studies for the slit by Monte Carlo program and finite element analysis. The existence of Bragg peak of the stopping power introduces a thermal spike and stress peak in the slit plate, and both the peak values reach a quasi-steady-state after several beam pulses, moreover, they show different variation trends with changing the beam repetition rate and pulse width. The equilibrium peak temperature and stress are about 1605 K and 78 MPa, respectively, at beam pulse width of 100 μs and repetition rate of 5 Hz when the beam centered at the edge of slit, which does not exceed the corresponding threshold value of graphite, however, high cycling stress may bring about fatigue damage, so the beam parameters should be selected at suitable values according to the demands of actual measurements.     

Assessment of biological changes in wheat seedlings induced by ^12C^6＋-ion irradiation

The present study was designed to evaluate the effect of 12C6 ion beam (10～80 Gy) on biological changes of wheat seedlings. Reactive oxygen species (ROS)-related biomarkers and the quantification of plant survival and growth were examined at 10 day after carbon ions irradiation (LET 30.8keV/μm). The results showed that heavy ions obviously enhanced ROSs reflected by the production of O2 and H2O2 as well as TBARS, and treatment with 20 Gy achieved the peak value, suggesting that higher mutagenic potential may occur at 20 Gy. Simultaneously, increase of SOD activity was induced by heavy ions to counteract ROS accumulation. On the other hand, higher doses at 40 and 80 Gy inhibited wheat growth and survival in comparison with the control, and reversely lower doses at 10 or 20 Gy stimulated wheat growth and survival. In conclusion, the above observations imply that a dose range of 20～40 Gy is likely promised for wheat mutation breeding.