Ultrahigh-intensity laser-produced plasmas as a compact heavy ioninjection source

The possibility of using high-intensity laser-produced plasmas as a source of energetic ions for heavy ion accelerators is addressed. Experiments have shown that neon ions greater than 6 MeV can be produced from gas jet plasmas, and well-collimated proton beams greater than 20 MeV have been produced from high intensity laser solid interactions. The proton beams from the back of thin targets appear to be more collimated and reproducible than are high-energy ions generated in the ablated plasma at the front of the target and may be more suitable for ion injection applications. Lead ions have been produced at energies up to 430 MeV     

Electrical Properties of Isotactic Polypropylene/Multiwalled Carbon Nanotubes Composites Prepared by Vibration Injection Molding

To study the effect of vibration field on the electrical conductivity properties of nanocomposites, isotactic polypropylene (iPP)/multiwalled carbon nanotubes (MWCNT) composites were prepared by conventional injection molding and vibration injection molding. Results showed that the electrical conductivity of iPP/MWCNT composites was significantly promoted by vibration injection molding. Vibration injection molded samples had a percolation threshold of about 2.7 wt% compared with the threshold of about 4.5 wt% for conventional injection molded samples. The effects of test locations and vibration frequency on the electrical conductivity of composites were investigated. The samples exhibited an inhomogeneity along the injection direction. The electrical conductivity of the samples was different at different test locations and increased with increasing vibration frequency. Polarized light microscopy (PLM) results indicated that vibration injection molding can induce MWCNT aggregates to be stretched and oriented along the flow direction, which could form conductive networks and greatly enhance the electrical conductivity of iPP/MWCNT composites.     

Development of a double-sided micro lens array for micro laser projector application

This paper introduces the development of a double-sided micro lens array (DSMLA) for application in micro laser projectors. For commercial mass production, it is necessary to investigate the concurrent engineering of optical design, mold fabrication, and plastic injection molding at once. This experiment based the design of the micro lens array on the scalar diffraction theory. The proposed DSMLA can simultaneously shape red, green, and blue laser beams into a uniform projection pattern. An ultra precision diamond turning machine using a slow tool servo method fabricated the mold. The study considered optical design constraints from the feedback of mold fabrication and plastic injection molding, measuring and comparing fabricated samples with calculated results. Experimental results show that the fabricated DSMLAs achieve the desired function and application feasibility for micro laser projectors.     

Laser Accelerated, High Quality Ion Beams

Intense beams of protons and heavy ions have been observed in ultra-intense laser-solid interaction experiments. Thereby, a considerable fraction of the laser energy is transferred to collimated beams of energetic ions (e.g. up to 50 MeV protons; 100 MeV fluorine), which makes these beams highly interesting for various applications. Experimental results indicate very short pulse duration and an excellent beam quality, leading to beam intensities in the TW range. To characterize the beam quality and its dependence on laser parameters and target conditions, we performed experiments at several high-power laser systems. We found a strong dependence on the target rear surface conditions allowing to tailor the ion beam by an appropriate target design. We also succeeded in the generation of heavy ion beams by suppressing the proton amount at the target surface. We will present recent experimental results demonstrating a transverse beam emittance far superior to accelerator-based ion beams. Finally, we will discuss the prospect of laser-accelerated ion beams as new diagnostics in laser-solid interaction experiements. Special fields of interest are proton radiography, electric field imaging, and relativistic electron transport inside the target.     

Gafchromic® EBT films for ion dosimetry

For dose delivery to patients, scanning ion beams are going to be increasingly used in the upcoming ion beam therapy facilities. Especially carbon ion beams are able to produce steep dose gradients. However, the currently used method for patient dose verification, employing ionization chamber arrays, provides a spatial resolution of 1 cm only. As continuous media, EBT films, widely used in photon therapy, are interesting candidates to be used for this purpose. The EBT film is the ancestor of the currently available EBT2 film. In our contribution two dimensional dosimetry and film response quenching in ion beams were investigated. For a real ¹²C patient plan a good qualitative agreement with the planned dose distribution including a high signal-to-noise ratio and a good resolution in the measured photon-equivalent dose was found. The depth-dose response of EBT films for a ¹²C ion beam shows response quenching, which rises towards the Bragg peak. It was quantified by the relative efficiency determined at different depths. Furthermore, the relative efficiency was measured in monoenergetic proton and carbon ion beams. All the measured efficiencies show no significant dependency on the dose up to the highest measured doses of 6 Gy. However, differences between proton and carbon ions as well as between carbon ion beams of different energies were observed. The measurements reveal, that the use of EBT films for absolute dose verification measurements requires to take the relative efficiency into account, dependent on the ion type and energy.     

Transverse characteristics of short-pulse laser-produced ion beams: a study of the acceleration dynamics

We report on first measurements of the transverse characteristics of laser-produced energetic ion beams in direct comparison to results for laser accelerated proton beams. The experiments show the same low emittance for ion beams as already found for protons. Additionally, we demonstrate that the divergence is influenced by the charge over mass ratio of the accelerated species. From these observations we deduced scaling laws for the divergence of ions as well as the temporal evolution of the ion source size.     

原子能院的核天体物理研究和串列升级工程进展(英文)

在北京串列实验室建立了次级束流实验装置 ,用于放射性核束物理和核天体物理研究 .先后开展了7Be(d ,n) 8B ,11C(d ,n) 12 N ,8Li(d ,p) 9Li和6 He(p ,n) 6 Li核天体物理重要反应的研究 .介绍了串列加速器升级工程的进展情况 .该工程在现有串列加速器的基础上 ,将建立 10 0MeV/ 2 0 0 μA的质子回旋加速器、在线同位素分离器和超导加速段 .在此装置上 ,将可以产生质量数最高为 12 0 ,强度最高为 10 9particles/s的放射性束流 . A secondary beam line (GIRAFFE) at the Beijing Tandem accelerator lab was constructed for yielding low energy secondary beams. The current progress on the study of nuclear astrophysics and nuclear structure is presented. Up to now, We have carried out measurement of~(7)Be(d, n)~( 8)B,~(11)C(d, n)~(12)N,~(8)Li(d, p)~(9)Li, and~(6)He(p, n)~(6)Li reactions. The proposed Beijing radioactive nuclear beam facility (BRIF ) and its current R&D progress are briefly introduced. This facility is based on...     

利用CR39上的径迹鉴别激光加速离子产物

分别利用单能的质子束及碳离子束辐照CR39,并制定了规范的刻蚀条件及流程。通过对处理完成后的数据进行详细处理,得到了质子及碳离子的径迹直径-能量的响应曲线,可用于确定CR39上质子或碳离子的能量。以此为依据,得到了鉴别CR39上质子及碳离子的有效方法。在激光加速离子的实验中,通过测量CR39上的径迹大小及相对灰度,利用本文给出的标定数据,确认了质子径迹,得到了实验的质子能谱。     

Development of a laser-driven proton accelerator for cancer therapy

Recent advances in laser technology have made proton (light ion) acceleration possible using laser-induced plasmas. In this work, we report our work for the last few years on the investigation of a new proton therapy system for radiation oncology, which employs laser-accelerated protons. If successfully developed, the new system will be compact, cost-effective, and capable of delivering energy-and intensity-modulated proton therapy (EIMPT). We have focused our research on three major aspects: (1) target design for laser-proton acceleration, (2) system design for particle/energy selection and beam collimation, and (3) dosimetric studies on the use of laser-accelerated protons for cancer therapy. We have performed particle-in-cell (PIC) simulations to investigate optimal target configurations for proton/ion acceleration. We also performed Monte Carlo simulations to study the beam characteristics and the feasibility of using such beams for cancer treatment. Since laser-accelerated protons have broad energy and angular distributions, which are not suitable for radiotherapy applications directly, we have designed a compact particle selection and beam collimating system for EIMPT beam delivery. We also proposed a new gantry design to make the whole system compact to retrofit existing linac vaults. We have compared Monte Carlo calculated dose distributions using X-ray IMRT and laser-proton EIMPT. Our results show that EIMPT using laser protons produces superior target coverage and much reduced critical structure dose and integral dose compared to X-ray IMRT.     

Hypernuclear Spectroscopy with Stable Heavy Ion Beams and Rare-isotope Beams:HypHI Project at GSI and FAIR

The international HypHI collaboration proposes to perform hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and FAIR in order to study neutron and proton rich hypernuclei and to measure directly hypernuclear magnetic moments for the first time.The project is divided into four phases.In the first Phase 0 experiment,the feasibility of precise hypernuclear spectroscopy with heavy ion beams will be demonstrated by observing π~- decay channels of ~e_ΛH,~4_ΛH and ~5_ΛHe with ~6Li projectiles at 2 AGeV impinging on a ~(12)C target.In the later Phases 1 through 3,studies of proton and neutron rich hypernuclei,direct measurements of hypernuclear magnetic moments and the spectroscopy of hypernuclei toward the nucleon drip-lines are planned.     

Yerevan synchrotron injector electron beam transversal scan with vibrating wire scanner

We have developed extended-aperture (20 mm) vibrating wire scanner (VWS) for transversal scanning of electron beams with large transversal size. Test experiments were performed in open atmosphere on the 40 MeV electron beam of the Yerevan synchrotron injector with the 4–10 μA at outlet. A construction of VWS is elaborated for scanning beams with larger transversal size. This elaboration is a new precision tool for diagnostics of beams in accelerators, which may be successfully employed, because of universality of the used operation principle, for profiling of as well large-aperture proton and ion beams.     

Contact welding study of carbon nanotube with ZnO nanowire

Study of proton beam induced welding of multiwall carbon nanotubes (MWCNTs) with ZnO nanowires (NWs) has been carried out by proton (H⁺) beam irradiation. The samples were irradiated by 70-keV proton (H⁺) ion beams at different substrate temperatures. The irradiation-induced defects in CNTs and ZnO NWs were greatly reduced at elevated temperature. The crystalline structure of ZnO NWs and MWCNTs were found to remain stable after the irradiation at 700 K. As a preparation step, a coupling of two parallel ZnO NWs with irradiation has also been demonstrated. The welding mechanisms of MWCNTs and ZnO NWs were also been suggested. These two welding processes between same and distinct nanostructures to form homo- and hetero-junctions have provided an opportunity to mass produce interconnecting one-dimensional structures used for the manufacturing of future nanowire-based electronic circuits and devices.     

Self-Reinforced High-Density Polyethylene Prepared by Low Frequency Vibration-Assisted Injection Molding. II: Microstructure Investigation

Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD) were employed to study the microstructure of self-reinforced high-density polyethylene (HDPE) prepared by conventional injection molding (CIM) and a low frequency vibration-assisted injection molding (VAIM). SEM micrographs following permanganic etching showed the self-reinforcement of HDPE is mainly due to the existence of shish-kebab morphology within the core region for VAIM-processed HDPE samples. Pronounced molecular alignment was identified by the WAXD data. An approximate 9% increase in the crystallinity was confirmed by DSC. Both preferred molecular orientation and increased crystallinity serve to yield stronger VAIM-processed injection moldings.     

Optimization of accelerated charged particle beam for ADS energy production

A comparative analysis and optimization of energy efficiency for proton and ion beams in ADS systems is performed via simulation using a GEANT4 code with account for energy consumption for different accelerator types. It is demonstrated that for light nuclei, beginning from ⁷Li, with energies above 1 GeV/nucleon, ion beams are considerably (several times) more efficient than the 1–3 GeV proton beam. The possibility of achieving energy deposition equivalent to 1 GeV protons in a quasi-infinite uranium target with higher efficiency (and twice as small accelerator size) in the case of acceleration of light ions is substantiated.     

The effect of working pressure on the chemical bond structure and hydrophobic properties of PET surface treated by N ion beams bombardment

Polyethylene terephthalate (PET) surface was bombarded by N ion beams at room temperature. Varying the working pressure of the ion beams, PET surfaces with different composition and properties were obtained. Characterization by X-ray photoelectron spectrometry showed that only on film surface, ester bonds, especially C-O bonds, were broken and N element chemical bonded with C. The influence depth was less than 5 nm because of the lower ion energy (about 10³ eV). Contact angle results revealed that with increasing the working pressure of ion beams, the contact angle of PET surface to pure water increased from 51° to 130°. With these results, one conclusion could be deduced that the hydrophilic and hydrophobic properties of PET surface could be influenced by N atom chemical bond with C, which in turn is controlled by the working pressure of N ion beams.     

Preservation and control of the proton and deuteron polarizations in the proposed electron-ion collider at Jefferson Lab

We propose a scheme of preserving the proton and deuteron beam polarizations during acceleration and storage in the proposed electron-ion collider at Jefferson Lab. This scheme allows one to provide both the longitudinal and transverse polarization orientations of the proton and deuteron beams at the interaction points of the figure-8 ion collider ring. We discuss questions of matching the polarization direction at all stages of the beam transport including the pre-booster, large booster and ion collider ring.     

Study of the evolution of the atomic composition of thin NbN films under irradiation with mixed ion beams by methods of electron energy loss spectroscopy

The variation in the atomic composition of ultrathin NbN films under irradiation by mixed ion beams to a doze of 4 dpa (for nitrogen) is experimentally studied by methods of electron energy loss spectroscopy with a transmission electron microscope in the transmission scan mode on cross-cut samples. The behavior of the substitution of nitrogen atoms by oxygen atoms has been established; it is characterized by changing the composition of the conducting part of the film from NbN to NbNO.     

氮离子注入对聚四氟乙烯表面电荷积聚和消散特性的影响北大核心CSCD

为了抑制聚四氟乙烯材料表面电荷积聚,采用射频产生氮等离子体对其表面进行等离子体浸没离子注入以改善其表面性能。对注入前后的聚四氟乙烯材料样品进行了X射线光电子能谱分析(XPS)、傅里叶红外光谱测试(FTIR)、水接触角测量、表面电阻率测量以及表面电位衰减测量,并基于等温表面电位衰减理论对其表面陷阱能级和密度分布进行了计算,以分析聚四氟乙烯样品经离子注入处理后其表面成分和物理性能的变化,并研究了这些变化对聚四氟乙烯样品表面电荷积聚和消散特性的影响。结果表明:氮离子注入后,聚四氟乙烯材料表面化学成分的主要变化是自身分子结构的破坏和转化,部分CF2结构转变为CF和CF3结构,导致样品表面陷阱能级变浅;水接触角升至140°左右,比未处理样品上升了约27°,表面电阻率降至3×10^15Ω,比未处理样品下降了两个数量级;表面电晕放电1 min后,经氮离子注入处理的聚四氟乙烯材料表面积聚电荷量减少,消散速度加快,这是因为表面陷阱能级变浅有利于表面电荷脱陷,同时表面电阻率降低也促进了表面电荷沿面传导的消散过程,聚四氟乙烯样品表面陷阱能级分布曲线也证实了这一论点。     

Effective sputtering yields of titanium,titanium nitride,and molybdenum induced by nitrogen ions and ions of nitrogen-oxygen mixtures

This work is dedicated to studying the effects of nitrogen ions and ions of nitrogen and oxygen mixtures on the surface of titanium, titanium nitride, and molybdenum. The usage of magnetron sputtering systems as a model device to study the effect of reactive gases on elements of electric jet engines is proposed and justified. The processes of sputtering of a surface exposed to non-monoenergetic ion beams are studied. The effective sputtering yields of titanium, titanium nitride, and molybdenum induced by argon and nitrogen ions and ions of nitrogen-oxygen mixtures at various intermediate-energy ion beams are determined. It is shown that the sputtering yields of reactive-gas ions are significantly lower than the sputtering yields of inert gases.     

Molecular Spectral Analysis and Ab Initio Calculations of bis(3-aminopyridinium) Tetrachlorocuprate (II), 3-Ammoniumpyridinium Tetrachlorocuprate (II), and bis(3-aminopyridinium) Hexachlorodicuprate (II)

The aromatic character, distortion, and stabilization as a result of single and double protonation of 3-aminopyridine like three different complex salts were studied by infrared-, ultraviolet spectral analysis, proton nuclear magnetic resonance, and quantum chemical ab initio calculations. Linear-dichroic infrared spectroscopy was applied for identification of the infrared bands. The correlation structure-spectroscopic properties of the model systems are determined: bis(3-aminopyridinium) tetrachlorocuprate (II) salt, where the ring nitrogen atom participates in protonation; 3-ammoniumpyridinium tetrachlorocuprate (II) salt, where both nitrogen atoms are protonated; and a complex with copper (II) bis(3-aminopyridinium) hexachlorodicuprate (II), where the metal ion is coordinated through amino group.