Cellular effects of energetic heavy ions: from DNA breaks to chromosomal rearrangements

Risk from exposure to energetic heavy ions is considered one of the main problems for human space exploration. Late stochastic risk estimates, particularly cancer, are affected by large uncertainties. Basic cell biology studies to elucidate the mechanisms involved in genetic damage are necessary to reduce the uncertainty and eventually design effective countermeasures. To study the influence of nuclear architecture on the formation of chromosomal rearrangements, normal diploid human fibroblasts have been exposed to heavy ions in horizontal and vertical positions. Analysis of chromosomal aberrations by arm-specific mFISH shows that, at the same radiation dose, the yield of chromosomal damage is modified by the irradiation geometry. A clear difference is seen in the fraction of aberrant cells, owing to the different nuclear cross sections.     

Performance of a phoswich detector array for light particles and heavy ions

A phoswich array consisting of 48 ΔE - E elements with sufficient granularity (ΔΘ = ± 2.5°) to handle high multiplicity events has been built and used in several experiments. The full angular coverage is a 35° × 35° square cross section of the 4π sphere. Unit charge resolution for Z ≤ 10 and mass resolution for Z = 1 particles has been achieved with a ±5% energy resolution. Experimental details and the performance of the array are presented and discussed.     

A large solid-angle array for heavy ions from APEX

A large solid-angle array of Low Pressure Multi-Wire Proportional Counters (LPMWPCs) has been constructed as part of the ATLAS Positron Experiment (APEX). Eight three-element trapezoidal counters span 360° in φ and 20–68° in laboratory θ. Angle sensitivity in θ is provided by a transmission-line delay cathode, while the 24-fold segmentation provides angle sensitivity in φ. Details are given on the design of the counters and associated hardware. Performance of the counters is described, based on tests with scattered heavy ions ranging from ⁵⁸Ni to ²³⁸U.     

Energy sensitive detection of heavy ions with transition edge calorimeters

Status and results of a research project are reported, which aims at developing calorimetric low temperature detectors for heavy ions. The special conditions for the detection of energetic heavy ions are discussed. The response of an aluminium transition edge calorimeter, operated at about1.5K, to the impact of heavy ions was investigated. The observed energy resolutions E/E=3.9×10^–3for5.9MeV/u ²⁰⁸ Pb-ions, E/E=1.6×10^–3for4.8MeV/u ⁵⁸ Ni-ions and E/E=4.3×10^–3for100MeV/u ²⁰ Ne-ions are most probably not yet limited by the intrinsic detector resolution. The present results already represent an improvement over conventional solid state detectors and ionization chambers.     

Surface erosion and modification by energetic ions

Surface erosion and modification by energetic highly charged and cluster ions are important in the development of semiconductor devices, TeV accelerators, fission and fusion reactors, and in the development of extreme ultra-violet lithography devices. Gas cluster ion beam (GCIB) surface treatment can significantly mitigate the high-gradient electric vacuum breakdown of rf-cavities. GCIB can also mitigate Q-slope drop in superconducting Nb-cavities. Various mechanisms of the highly charged ion (HCI) energy transfer into the solid target, such as hollow atom formation, charge screening and neutralization, shock wave generation, and sputtering were analyzed. Surface erosions caused by GCIB, HCI bombardments, and by low energy He⁺ and H⁺ ions typical for fission and fusion devices were studied by using molecular dynamics simulation. A He bubble splashing mechanism of liquid Li containing was developed, and surface erosion was simulated. The mechanism of bubble explosion could significantly contribute to the surface erosion at high ion fluxes and explain the existing experimental results.     

Delay-line PPAC for high-energy light ions

We have developed a delay-line parallel-plate avalanche counter (PPAC) with high detection efficiency for high-energy light ions. A large signal-to-noise ratio was achieved by a newly designed pre-amplifier and the usage of C₃F₈ gas at a pressure of 30 Torr. The counter has been tested with beams of 90 AMeV ⁷Li at RIKEN, 340 AMeV ¹²C at GSI, and 254 AMeV ⁸B at GSI. We achieved high detection efficiencies (>95%) for all of these ions. Furthermore, we achieved reasonable position and timing resolutions.     

Range-to-cone-length relations for light ions in Cr

Curves of “range × cone length” and “diameter × cone length” are calculated for tracks left by low-energy light ions in ³⁹Cr. The calculations cover ions from helium to iron and are performed for 6.25N NaOH at 70°C and a standard etching time but can be easily extended to other etching conditions.     

Noise analysis for calorimetric low-temperature detectors for heavy ions

The energy resolution of calorimetric low-temperature detectors for heavy ions has been analyzed. It is shown that the contribution of base line noise is small. The energy resolution is determined by intrinsic fluctuations of the detector signal. An incomplete energy thermalization during the stopping process of the heavy ion, the dependence of signal shape on impact position and fluctuations of the Al-TES thermometer response are considered as main sources of detector line broadening. Test measurements with 5 MeV -particles are presented.     

Analysis of coatings and thin films using energetic ions

Energetic ion analysis techniques provide non-destructive information on the depth distribution of atomic composition in the near-surface (1–10 μm) region of a solid sample. The techniques are quantitative and are not complicated by the presence of chemical or matrix effects. Generalized nuclear reaction analysis is described and its application to the measurement of the stoichiometry of Ta₂O₅ films and BeO coatings on Cu-Be is briefly discussed.     

DNA-repair protein distribution along the tracks of energetic ions

A simple model of homogenous chromatin distribution in HeLa-cell nuclei suggests that the track of an energetic ion hits 30 nm chromatin fibers with a mean distance of 0.55 mum. To test this assumption, living HeLa-cells were irradiated at the irradiation setup of the ion microprobe SNAKE using the ion beams provided by the Munich 14 MV tandem accelerator. After irradiation, the distribution of 53BP1 protein foci was studied by immunofluorescence. The observed 53BP1 distribution along the tracks of 29 MeV (7)Li ions and 24 MeV (12)C ions differed significantly from the expectations resulting from the simple chromatin model, suggesting that the biological track structure is determined by cell nuclear architecture with higher order organisation of chromatin.     

Development of superconducting niobium accelerating structures for heavy ions

Results of tests of two new designs for superconducting niobium resonant cavities are presented. Both types resonate at 145.5 MHz and accelerate most efficiently for particle velocities β= v/c = 0.16. One resonator is of the split-ring type, but of a simpler design than a previously reported β=.16 unit. Although the surface fields are higher, the performance is somewhat better than for the earlier design: an accelerating field Ea= 4.3 MV/m has been obtained at 4.2K with 4w of rf input, where Eais defined as the energy gain per unit charge for a synchronous particle averaged over the interior resonator length. The other resonator is an 8-inch OD tapered coaxial quarter-wave line terminated with a drift tube of 1.50 inch aperture. At 4.2K, this resonator exhibits a low-level Q of 2×10⁹, and has achieved Ea= 4.7 MV/m with 2.8w of rf input.     

微纳结构化智能凝胶材料用于重金属离子快速检测的研究进展

智能凝胶材料由于具有特异响应环境信息的能力,被广泛应用于生物或化学传感器,包括重金属离子传感器.由于智能凝胶材料的特征尺寸越小,响应速度越快,因此研究重金属离子响应型智能凝胶材料的微纳尺度结构化对于实现其快速检测具有指导意义.综述了近年来利用微纳结构化智能凝胶材料实现重金属离子快速检测的研究进展,探寻可以制备出简单、可...     

Integrated light collimating system for extended optical-path-length absorbance detection in microchip-based capillary electrophoresis

We have developed an integrated light collimating system with a microlens and a pair of slits for extended optical path length absorbance detection in a capillary electrophoresis (CE) microchip. The collimating system is made of the same material as the chip, poly(dimethylsiloxane) (PDMS), and it is integrated into the chip during the molding of the CE microchannels. In this microchip, the centers of an extended 500-microm detection cell and two optical fibers are self-aligned, and a planoconvex microlens (r = 50 microm) for light collimation is placed in front of a light-delivering fiber. To block stray light, two rectangular apertures, realized by a specially designed three-dimensional microchannel, are made on each end of the detection cell. In comparison to conventional extended detection cell having no collimator, the percentage of stray radiation readout fraction in the collimator integrated detection cell is significantly reduced from 31.6 to 3.8%. The effective optical path length is increased from 324 to 460 microm in the collimator integrated detection cell. The detection sensitivity is increased by 10 times in the newly developed absorbance detection cell as compared to an unextended, 50-microm-long detection cell. The concentration detection limit (S/N = 3) for fluorescein in the collimator integrated detection cell is 1.2 microM at the absorbance detection limit of 0.001 AU.     

基于强化学习的空间引力波探测望远镜系统外杂光抑制研究

引力波望远镜其收集的空间目标光信号能量远小于杂散光能量,为了保证引力波望远镜的正常工作,需要保证较好的杂光抑制效果。又由于散射光线的不确定性,光机系统本身的复杂性,杂光抑制方案的确定往往需要复杂的数学公式计算以及丰富的经验与充足时间进行仿真迭代。本文提出了一种基于强化学习的杂光抑制策略,针对空间引力波探测望远镜系统中的环境杂光问题,采用蒙特卡洛光线追迹方法进行分析和处理。通过制定有效的杂光抑制措施,实现了对该系统中杂光的有效控制。仿真结果验证了该方法在空间引力波探测望远镜系统中杂光抑制方面的优异性能,展示了其具有良好杂光抑制效果的潜力。这一研究为解决空间引力波探测和其他高精度光学系统中的杂光问题提供了一种高效、灵活的新方法,具有广泛的应用潜力。

     

Nickel sputtering by high-energy heavy ions

Recent experimental data on the sputtering of coarse-grained metals by high-energy heavy ions are reviewed. It is pointed out that inelastic energy losses of ions have rather insignificant effect on the sputtering yield of metals. Experimental data on the sputtering of nickel by ⁸⁶Kr⁺ ions are presented. The accumulation of radiation defects in the crystal lattice of nickel in the course of irradiation leads to an increase in the metal sputtering yield from the surface of grains, making it comparable with the sputtering yield from the intergranular region. The results of such experiments are important for development of the heavy ion acceleration facilities and for the high-energy heavy-ion doping of deep layers in semiconductors.     

Modifications induced by swift heavy ions

On their way through matter, energetic heavy ions induce a continuous trail of ionization and excitation. A narrow path of irreversible physical, chemical and structural changes, the latent track, is formed. In this report, some of the most important techniques (transmission electron and atomic force microscopy, small-angle X-ray scattering, chemical etching) to study and to characterize ion induced modifications will be presented. Furthermore, selected examples for application oriented projects will be given.     

A digital-signal-processor-based measurement system for on-linefault detection

This paper deals with the design, construction, and setting up of a measurement apparatus, based on an architecture using two parallel digital signal processors (DSP's), for on-line fault detection in electric and electronic devices. In the proposed architecture, the first DSP monitors a device output on-line in order to detect faults, whereas the second DSP estimates and updates the system-model parameters in real-time in order to track their eventual drifts. The problems which arose when the proposed apparatus was applied to a single-phase inverter are discussed, and some of the experimental results obtained in fault and nonfault conditions are reported     

一种应用于水下目标探测的激光声系统

用激光在海洋中产生声波的方式机动性非常好,在海洋监测方面具有非常强的潜在应用前景.介绍了已经成功研制出的一套可以用于水下目标探测的激光声技术实验系统,详尽地介绍了用于水下目标探测的激光声系统原理、硬件设计以及软件设计.该系统不仅通过了实验室的试验,并且参加了海上试验,实验结果表明本系统的原理正确,性能良好,工作稳定可靠,能够检测到水中目标的回波,探测到水下目标.说明激光声技术用于水下目标探测是切实可行的,这套激光声探测系统的研制成功填补了国内的空白.     

Response of acoustic signals generated in water by energetic xenon ions

The acoustic signals generated by bombarding 400 MeV/n xenon ions in water were studied using an array of piezoelectric lead–zirconate–titanate elements. The observed signal was reduced to a bipolar form through Fourier analysis. The output voltage corresponded to the amount of energy deposit in water, and it tailed off beyond the range of 400 MeV/n xenon in water. This magnitude was explained qualitatively as cumulative processes. Its behavior was consistent with the calculations based on the Bethe–Bloch formula. Possible applications of this detector to radiology and heavily doped radiation detectors are described.