Electromagnetic field effects on nucleon transverse momentum for heavy ion collisions around 100 A MeV

Effective atomic numbers for photon energy absorption(ZPEA_(eff)) and their corresponding electron numbers (NPEA_(eff)), and effective macroscopic removal cross sections of fast neutrons(RR) were calculated for 27 different types of three-dimensional dosimeters, four types of phantom materials, and water. The values of ZPEA_(eff) and NPEA_(eff) were obtained using the direct method for energies ranging from 10 keV to 20 MeV. Results are presented relative to water, for direct comparison over the range of examined energies. The effect of monomers that are used in polymer gel dosimeters on the water equivalence is discussed. The relation between Σ_R and hydrogen content was studied. Micelle gel dosimeters are highly promising because our results demonstrate perfect matching between the effective atomic number, electron density number, and fast neutron attenuation coefficient of water.     

Effects of the momentum dependence of nuclear symmetry potential on pion observables in Sn + Sn collisions at 270 MeV/nucleon

Within a transport model, we investigated the effects of the momentum dependence of the nuclear symmetry potential on the pion observables in central Sn + Sn collisions at 270 MeV/nucleon. To this end, the quantity U_sym^∞(ρ₀)(i.e., the value of the nuclear symmetry potential at the saturation density ρ₀ and infinitely large nucleon momentum) was used to characterize the momentum dependence of the nuclear symmetry potential. With a certain L(i.e., the sl...     

100MeV强流质子回旋加速器主磁铁电磁力的数值模拟

本工作研究计算中国原子能科学研究院目前正在设计、建造中的100MeV强流质子回旋加速器CYCIAE-100主磁铁电磁力。计算中选用虚位移法和麦克斯韦应力张量法两种方法。在利用电磁场三维有限元分析程序计算得到紧凑型等时性回旋加速器主磁铁电磁场的基础上,先采用虚位移法估算电磁吸力,然后基于麦克斯韦应力张量法在MATLAB环境下编写数值计算程序,详细研究磁极和磁轭受到的电磁吸力。两种方法的计算结果接近。计算得到的主磁铁磁极间吸力大于磁极与盖板间吸力,二者之差由磁极和盖板间的螺栓承担。电磁力的计算结果为主磁铁结构变形计算和结构方案选取提供了依据。     

A study on swift (∼100 MeV) heavy ion irradiated Ni films on Si substrates

Ni thin films (∼50 nm) on silicon substrates have been irradiated from 100 MeV swift heavy ions of Fe⁷⁺ with a fluence of 10¹² ions cm⁻². SEM studies show a nice feature of interwoven grains which looks like a knitted network which has been resolved as a spherical grainy structure from AFM studies. Chemical phase identification of the grains has been done from XRD studies and it is found that there is a formation of the Ni₂Si silicide phase having average grain size of ∼70 nm. The devices have also been characterized from I-V characteristics before and after the irradiation at varying temperature from LN₂ to room temperature. The current across the irradiated interface has increased by two orders of magnitude as compared to the unirradiated ones and show a nearly temperature independent behaviour. MR (magnetoresistance) has been studied from the current flow data in magnetic fields up to 10 kG. Unirradiated devices do not show any effect on current transport in external magnetic field. M-H characteristics of the irradiated devices show the typical magnetic behaviour of nano particles like superparamagnetic behaviour. The MR features has been related to the M-H variations. The observed results show the formation of magnetic nano grains due to interfacial intermixing in these devices of Ni/n-Si. The role of swift heavy ions for nano grain fabrication has been discussed and the observed properties have been understood by considering the formation of a nano magnetic granular phase.     

Search for the chiral magnetic effect in heavy ion collisions

Quark interactions with topological gluon fields in quantum chromodynamics can yield local P and CP violations that could explain the matter–antimatter asymmetry in our universe. Effects of P and CP violations can lead to charge separation under a strong magnetic field, a phenomenon called the chiral magnetic effect(CME).Early measurements of the CME-induced charge separation in heavy ion collisions are dominated by physics backgrounds. This report discusses the recent innovative efforts in eliminating those backgrounds, namely by eventshape engineering, invariant mass dependence, and reaction and participant plane comparison. The backgroundfree CME measurements using these novel methods are presented.     

A new stopping power parameterization for 0.1-15 MeV/nucleon heavy and superheavy ions in solids and gases

Electronic stopping powers of heavy ions in several media are deduced from the corresponding proton data by using new effective charge parameterizations. Separate sets of parameters were deduced for solid and gaseous materials using the available data for heavy ions in the energy range from 0.1 to 15 MeV/nucleon. Using these results, predictions are made for stopping powers of heavy and superheavy elements with Z = 100-130 in the energy range of 0.5-15 MeV/nucleon.     

Optical absorption and thermoluminescence studies in 100 MeV swift heavy ion irradiated CaF2 crystals

Pure and Ytterbium (Yb) doped Calcium fluoride (CaF₂) single crystals were irradiated with 100 MeV Ni⁷⁺ ions for fluences in the range 5 × 10¹¹-2.5 × 10¹³ ions cm⁻². The irradiated crystals were characterized by Optical absorption (OA) and Thermoluminescence (TL) techniques. The OA spectra of ion irradiated pure CaF₂ crystals showed a broad absorption with peak at ∼556 nm and a weak one at ∼220 nm, whereas the Yb doped crystals showed two strong absorption bands at ∼300 and 550 nm. From the study of OA spectra, the defect centers responsible for the absorption were identified. TL measurements of Ni⁷⁺ ion irradiated pure CaF₂ samples indicated a strong TL glow with peak at ∼510 K. However, the Yb doped crystals showed two TL glows at ∼406 and 496 K. The OA and TL intensity were found to increase with increase of ion fluence upto 1 × 10¹³ ions cm⁻² and thereafter it decreased with further increase of fluence. The results obtained are discussed in detail.     

Isospin effects on intermediate mass fragments at intermediate energy-heavy ion collisions

In this study, we investigated the isospin properties of intermediate mass fragments（IMFs） for the central collisions of^112,124Sn+^112,124Sn at a beam energy of50 MeV per nucleon using an improved quantum molecular dynamics model（ImQMD） coupled with a sequential decay model（GEMINI）. Three observables were analyzed:（1） the average center-of-mass kinetic energy per nucleon of fragments as a function of their charge number Z;（2） the average neutron number to prot...     

Study of 160 MeV Ni ion irradiation effects on electrodeposited polypyrrole films

Conducting polymer polypyrrole thin films doped with LiCF₃SO₃, [CH₃(CH₂)₃]₄NBF₄ and [CH₃(CH₂)₃]₄NPF₆ have been electrodeposited potentiodynamically on ITO coated glass substrate. The polymer films are irradiated with 160 MeV Ni¹²⁺ ions at three different fluences of 5 × 10¹⁰, 5 × 10¹¹ and 3 × 10¹² ions cm⁻². An increase in dc conductivity of polypyrrole films from 100 S/cm to 170 S/cm after irradiation with highest fluence is observed in four-probe measurement. X-ray diffractogram shows increase in the crystallinity of the polypyrrole films upon SHI irradiation, which goes on increasing with the increase in fluence. Absorption intensity increase in the higher wavelength region is observed in the UV–Vis spectra. The SEM studies show that the cauliflower like flaky microstructure of the surface of polypyrrole films turns globular upon SHI irradiation at fluence 5 × 10¹¹ ions cm⁻² and becomes smooth and dense at the highest fluence used. The cyclic voltammetry studies exhibit that the redox properties of the polypyrrole films do not change much on SHI irradiation.     

Experimental study on heavy ion single-event effects in flash-based FPGAs

With extensive use of flash-based field-programmable gate arrays(FPGAs) in military and aerospace applications, single-event effects(SEEs) of FPGAs induced by radiations have been a major concern. In this paper, we present SEE experimental study of a flash-based FPGA from Microsemi Pro ASIC3 product family. The relation between the cross section and different linear energy transfer(LET) values for the logic tiles and embedded RAM blocks is obtained. The results show that the sequential logic cross section depends not too much on operating frequency of the device. And the relationship between 0 →1 upsets(zeros) and 1 →0 upsets(ones) is different for different kinds of D-flip-flops. The devices are not sensitive to SEL up to a LET of 99.0 Me V cm2/mg.Post-beam tests show that the programming module is damaged due to the high-LET ions.     

一台用于重离子鉴别的Bragg曲线谱仪

本文介绍制作的一台用于重离子鉴别的Bragg曲线谱仪。它是一种电场平行于入射粒子方向的全阻止型电离室。其性能用ThC-C’α源和~(252)Cf源进行了测试。对8.785MeV α粒子(ThC’源)能量分辨好于1％,电荷分辨Z/ΔZ=50。     

Research on Damage Effects of 100 MeV Protons on A375 Cells

<正>Proton therapy,due to its advantages in killing tumor cells and damaging normal tissues,has become one of the most important physical therapies for treating tumors in the world.It can greatly improve the cure rate of tumors that are ineffective by conventional methods.In this     

Experimental study on heavy ion single event effects in SOI SRAMs

Silicon-on-insulator (SOI) technologies have been developed for radiation-hardened military and space applications. The use of SOI has been motivated by the full dielectric isolation of individual transistors, which prevents latch-up. The sensitive region for charge collection in SOI technologies is much smaller than for bulk-silicon devices potentially making SOI devices much harder to single event upset (SEU). In this study, 64 kB SOI SRAMs were exposed to different heavy ions, such as Cu, Br, I, Kr. Experimental results show that the heavy ion SEU threshold linear energy transfer (LET) in the 64 kB SOI SRAMs is about 71.8 MeV cm²/mg. Accorded to the experimental results, the single event upset rate (SEUR) in space orbits were calculated and they are at the order of 10⁻¹³ upset/(day bit).     

A note on obtaining symmetrical angular yield curves in MeV ion channeling

Planar channeling effects can distort the angular yield (dip) curve measured about an axial channeling direction. Two methods for minimizing distortion due to planar channeling are discussed: 1) varying the angles θ and φ of a two-axis goniometer together during the angular scan, and 2) remounting the sample so that a scan of only θ produces an undistorted symmetric dip curve. In practice, remounting the sample is preferred in order to minimize effects due to the mechanical limitations of the goniometer.     

一个用于重离子飞行时间测量的平行板雪崩探测器

平行板雪崩探测器很早就用于核物理实验工作。但由于性能的限制,没有被广泛采用;直至七十年代中期,经过较大改进,作为一种精确的时间信号探测器,才又被用于重离子物理实验。由于平行板雪崩探测器输出信号上升时间快、工作介质厚度薄、无辐照损伤、有效面积可以做得相当大、不易受杂散电子干扰等,特别适宜作为用于重离子物理实验的透射型时间信号探测器。通常,平行板雪崩探测器由两片平行电极组成,中间为稀薄的工作气体,两电极间保持恒定的电压。被探测的带电粒子垂直于电极而穿过工作气体,产生原电离,     

Irradiation effects with 100 MeV Xe ions on optical properties of Al-doped ZnO films

Al-doped ZnO (AZO) films are known as n-type transparent semiconductors. We have investigated the effects of 100 MeV Xe ion irradiation on the optical and structural properties of AZO films, which were prepared on SiO₂ glass at 400 °C by using a RF-magnetron sputtering deposition method. We discuss relationships between these property modifications and the recent observations of the conductivity increase by ion irradiation. It is suggested that the band-gap modification has more close relation with the conductivity increase than the structural modification.     

重离子注入生物材料质量沉积效应评述

前人曾用重离子束注入生物小分子，借助先进的仪器分析手段，对重离子注入质量沉积进行了初步研究，但质量沉积对处于生命状态下的活生物体组织细胞和生物大分子所带来的生物学效应，即质量沉积效应的研究还未见报道。将来可用放射性重离子束注入活细胞和生物分子，借助放射自显影示踪、放射性测量和分子生物学等研究技术对重离子注入质量沉积效应开展进一步研究。     

100keV金属表面改性离子注入与混合两用机

叙述了１００ｋｅＶ金属表面改性离子注入与混合两用机的总体结构及各主要部件的技术参数。该机经过调试各项主要指标已达到设计要求，工作稳定可靠，已开始金属材料表面改性实验。     

重离子辐照对红酵母的诱变作用

应用重离子加速器的50MeV／u^12C^6 重离子对胡萝卜素生产菌-红酵母(Rhodotorula RY Strain)进行辐照处理,经酵母发酵实验,发现50MeV／u^12C^6 重离子对胡萝卜素生产菌-红酵母具有诱变作用。初步筛选到了胡萝卜素产量有变化的辐照变异菌株,并对这些辐照变异菌株进行了RFLP(限制性片段长度多态性)和RAPD(随机扩增DNA多态性)分析,这些工作为工业上利用重离子对胡萝卜素生产菌进行诱变育种展现了新的前景。     

MeV Si ion beam modification effects on the thermoelectric generator from Er0.1Fe1.9SbGe0.4 thin film

Effective thermoelectric materials and devices have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT. The purpose of this study is to improve the figure of merit of the single layer of Er_0.1Fe_1.9SbGe_0.4 thin film used as thermoelectric generators. We have deposited the monolayer of Er_0.1Fe_1.9SbGe_0.4 thin film on silicon and silica substrates with thickness of 302 nm using ion beam assisted deposition (IBAD). Rutherford backscattering spectrometry (RBS) was used to determine the total film thickness and stoichiometry. The MeV Si ion bombardments were performed on single layer of Er_0.1Fe_1.9SbGe_0.4 thin films at five different fluences between 5 × 10¹³?5 × 10¹⁵ ions/cm².The defect and disorder in the lattice caused by ion beam modification and the grain boundaries of these nanoscale clusters increase phonon scattering and increase the chance of annihilation of the phonon. The increase of the electron density of states in the miniband of the quantum dot structure formed by bombardment also increases the Seebeck coefficient and the electrical conductivity. We measured the thermoelectric efficiency of the fabricated device by measuring the cross plane thermal conductivity by the 3rd harmonic (3ω) method, the cross plane Seebeck coefficient, and the electrical conductivity using the Van Der Pauw method before and after the MeV ion bombardments.