Dynamic energy spectrum and energy deposition in solid target by intense pulsed ion beams

A method for analyzing the dynamic energy spectrum of intense pulsed ion beam (IPIB) was proposed.Its influence on beam energy deposition in metal target was studied with IPIB produced by two types of magnetically insulated diodes (MID).The emission of IPIB was described with space charge limitation model,and the dynamic energy spectrum was further analyzed with time-of-flight method.IPIBs generated by pulsed accelerators of BIPPAB-450 (active MID) and TEMP-4M (passive MID) were studied.The dynamic energy spectrum was used to deduce the power density distribution of IPIB in the target with Monte Carlo simulation and infrared imaging diagnostics.The effect on the distribution and evolution of thermal field induced by the characteristics of IPIB dynamic energy spectrum was discussed.     

Development of secondary ion mass spectroscopy using medium energy C60 ion impact

In this paper, we report time-of-flight (TOF) secondary ion mass spectroscopy using primary C₆₀ ions with an energy range from several tens of keV to several hundreds of keV. Application of the spectroscopy to the analysis of a poly(amino acid) film revealed that characteristic peaks, necessary for identification of the amino acid in proteins, show higher intensities for medium energy C₆₀ (120 keV and 540 keV ) impacts than those for low energy C₆₀ (30 keV ) impacts. This finding demonstrates that medium energy C₆₀ ion impacts are useful for highly sensitive characterization of amino acids.     

Detectors for microbeam applications at medium ion energy

Nuclear microprobes with excellent lateral resolution can be realized using a liquid metal ion source and electrostatic einzel lens system in a few hundred keV energy range. In case of ion beam analysis it is better to provide a special detector for Rutherford Backscattering (RBS) analysis or elastic recoil detection. Good mass and depth resolutions should be attained while keeping the damage caused by the beam at tolerable level. Two solutions are considered in the present work: (1) toroidal electrostatic analyzer combined with simultaneous Time-of-Flight (TOF) measurement for mass identification; (2) TOF measurement only, using a large area microchannel plate. Both solutions can be combined with 2D position sensitive anode plates for excellent performance. In case of the first solution, it is possible to distinguish the different mass atoms by the scattering angle where their peak in the angular distribution appears. Similarly to the energy distribution at a fixed scattering angle the angular distribution at a fixed energy represents mass and depth distribution. In case of the second solution the huge acceptance angle will make it possible to analyze submicron spot size without serious beam effects and both heavy and light elements can be investigated.     

High resolution time-of-flight low energy ion scattering

Low energy ion scattering (LEIS) is a well known technique for quantitative composition and structure analysis. Two different detection methods can be used in a LEIS experiment, i.e. an electrostatic analyzer or a time-of-flight (TOF) spectrometer. Both techniques have specific advantages. Nevertheless, the time-of-flight technique surpasses usual electrostatic analyzers used in LEIS in terms of energy resolution. The possibility to measure ions and neutrals, and the better energy resolution permit to study neutralization or charge exchange processes in much more detail.

Here we present a TOF–LEIS setup with an energy resolution of better than 0.4% for 3 keV He ions and report experimental results for 3 keV He ions backscattered from a polycrystalline Cu target. The resulting ion spectrum shows interesting inherent features, which are analyzed. Possible causes for the appearance of these features are discussed.     

低能离子探测器的设计及测试

自行设计制作并测试了用于电子-离子碰撞电离截面测量实验的低能离子探测器。该探测器由Al_2O_3转换板、加速电极、单通道电子倍增器三部分组成。离子沿70°方向轰击转换板,产生数目与离子能量成正比的二次电子,电子由单通道倍增器测量。采用合适的电子学线路和甄别阈,可以有效地把离子计数与本底分开。对10keV Ar~+在入射束流小于10~4s~(-1)时,探测效率接近100％。本探测器可用于低能重离子的计数测量。     

Er+ medium energy ion implantation into lithium niobate

Erbium-doped lithium niobate (Er:LiNbO₃) is a prospective photonics component, operating at 1.5 μm, which could find its use chiefly as an optical amplifier or waveguide laser. In this study, we have focused on the properties of the optically active Er:LiNbO₃ layers, which are fabricated by medium energy ion implantation under various experimental conditions. Erbium ions were implanted at energies of 330 and 500 keV with fluences of 1.0 × 10¹⁵, 2.5 × 10¹⁵ and 1.0 × 10¹⁶ cm^?2 into LiNbO₃ single-crystalline cuts of various orientations. The as-implanted samples were annealed in air at 350 °C for 5 h. The depth distribution and diffusion profiles of the implanted Er were measured by Rutherford Backscattering Spectroscopy (RBS) using 2 MeV He⁺ ions. The projected range R_P and projected range straggling ΔR_P were calculated employing the SRIM code. The damage distribution and structural changes were described using the RBS/channelling method. Changes of the lithium concentration depth distribution were studied by Neutron Depth Profiling (NDP). The photoluminescence spectra of the samples were measured to determine whether the emission was in the desired region of 1.5 μm. The obtained data made it possible to reveal the relations between the structural changes of erbium-implanted lithium niobate and its luminescence properties important for photonics applications.     

Comparison of experimental and simulated low energy alkali ion scattering

Computer simulations performed using the MARLOWE code are compared with experimental results obtained for 1 keV Li⁺ ion scattering from W(001). Trajectory analysis using distributions of impact points, deflections and maximum penetration depths allow characterization of the contributing scattering mechanisms. Computer simulation is found to reproduce many of the observed features in the energy distributions and in the incident angle dependence, but there are also important differences. In agreement with experiment, a sharp, surface sensitive binary collision peak is found at certain angles but at others this peak may broaden, shift to lower energy and grow in intensity due to subsurface scattering mechanisms. Simulations overestimate the relative scattering intensity near critical edges and the importance of focused scattering from second layer atoms.     

Collision of low energy Na^＋ ion with C60

The collison-induced reaction of Na^ ion with neutral C60 vapour was investigated at the energy range of 10 to 150eV.The deposited films were studied via laser desorption time-of-flight mass spectroscopy(TOFMS).The fragment products of C60 with even number of carbon atoms,such as Cn^ (n=58,56,54),and adduct products,such as Cn^ (n=62,64,66,68) were observed in the positively charged TOF mass spectra.The endohedral fullerene ion of Na @C60^ was detected when collision energies are above 20eV.Besides,no negative endohedral fullerene was detected,the products appearing in positively charged mass spectra were also observed in the negatively charged mass spectra.In addidtion,a series of products with odd number of carbon atoms,such as Cn^-(n=53,55,57,59,61,63,65,67),also appeared.but the intensities of their signals were not as high as that of even numbered.Finally,it is interesting to find that the deposited films are insoluable in toluene,benzene or water.Their Fourier transform infrared (FTIR),spectra seem like those photopolymerized ones.Some of the reaction schemes are proposed to explain the experimental results.     

Monte Carlo simulation of X-ray spectra from low energy electrons using optical data

An approach using optical data to simulate both the bremsstrahlung continuum and characteristic K and L X-ray lines generated by low energy electrons (cfr. electron microscopy) in solids is discussed in this paper. The necessary analytical expressions together with the data to calculate the relevant cross sections for elastic and inelastic interactions at these energies along with variance reduction techniques are given. The results of the Monte Carlo simulation are compared to experimental data measured with a JEOL 6300 electron microscope.     

A ctivation measurement of neutron distribution in intermediate energy heavy ion target area

The distribution of neutrons produced by the reaction of 50MeV/u ^12C-ion on a thick Cu target are studied.The neutrons are measured with threshold activation detectors.Al.F,C,Al and In activation samples were used to measure neutrons with energy greater than 7,11,20,50MeV and thermal neutrons,respectively,The fluence rate,energy and angular distributions of neutrons,total neutron yield of 12C-ion and the emission rate in the forward direction of neutrons over 11 and 20MeV were obtained.     

Measuring correlated-electron effects with low energy alkaline earth ion scattering

A system of many electrons can display emergent phenomena beyond what would be predicted from the behavior of individual electrons. A method for triggering correlated electron behavior is to introduce a spin impurity into a metal, which causes the free electrons to respond collectively. In the present work, the unpaired valence electron on singly charged alkaline earth ions is used to provide the spin impurity during low energy ion scattering experiments. Previous calculations have suggested that electron correlations would result in an anomalous temperature dependence of the ion neutralization probability. The neutralization of magnesium (Mg) scattered from polycrystalline gold (Au) shows little dependence on temperature. Scattered strontium (Sr) does, however, show a marked temperature dependence of the neutralization that provides clear evidence of electron correlations. The results are discussed in terms of the velocity of the outgoing projectiles.     

Dynamic response of a multi-span beam to transverse impact

The general case of impact between a continuous beam on many supports and a moving mass striking the beam transversely at any point has been analysed. Expressions for the deflection of the beam at any point along the beam, the impact force and the duration of impact have been theoretically derived employing the operational method developed by Heaviside. The results are presented in convenient, easily computable form and are applicable for a beam of any number of spans, struck at any point. Experiments have been performed on a three-span beam using a photographic method of measurement. The agreement between the theoretical and experimental results is excellent. The formulations presented are expected to provide the basis for the development of a rapid and reliable method for designing multi-span beams to withstand impact loading.     

低能离子溅射引起表面损伤的研究

本文应用背散射沟道技术研究了低能离子轰击不同晶向表面所引起的晶格损伤与离子能量、剂量的关系,讨论了损伤形成的动力学过程。     

Irradiation effect on PET surface using low energy argon ion beam

A study of various physical properties of a PET film irradiated with an Ar beam is reported. SEM images and UV–VIS and FTIR spectra were obtained for a number of ionic fluxes and three irradiation times. Small changes in the energy gap of degradated samples were found, and the SEM images indicate that the optimum homogeneity and roughness are reached after 30 min of irradiation. These results may well be of practical interest. A modified saddle field ion source was used as a preparation tool of the surface of polyethylene terephthalate PET polymer substrate to be ready for coating or thin film deposition. Argon ion beam was used for this purpose, where the scanning electron microscope (SEM) shows that, the best sample is the one which was irradiated to 30 min, where this sample is more homogenous and roughness than other irradiated samples. Also the (UV–VIS) spectrum tells us that, there is small change on energy gap and this is meaning that, the change on electric properties is small also. In this case the sample is more homogenous and of higher roughness than other irradiated samples.     

Diagnosis and dynamics in a simple low energy medium current electron beam channel

We present a simple experimental setup and an associated method enabling both the non-destructive diagnosis and the calculation of the beam evolution in a low energy medium current electron beam channel, where the space-charge and emittance effects are comparable. The diagnosis makes use of an axially symmetric magnetic lens while a second lens is added to increase the flexibility in the beam processing. The paper emphasizes the three steps involved in the method: the evaluation of the lenses' magnetic field by numerical simulation, the beam diagnosis, and the computation of the beam envelope. The calculation of the magnetic field is based on the finite element method. Subsequently, the beam parameters at the electron source exit – emittance and cross-over radius and position – are found with the modified three gradient method. Finally, the beam dynamics are modeled with the K–V equation adapted for the particular case of axial symmetry. The results obtained in this paper can be used to optimize technological processes, such as welding, hardening, cladding, and surface alloying.     

Annular gas ionization detector for low energy heavy ion backscattering spectrometry

A gas ionization chamber for use in backscattering spectrometry has been built. It has the shape of a hollow cylinder and can be placed in-line with the incident ion beam. The entrance window for detected particles is composed of a circular array of silicon nitride membranes. A low noise preamplifier with cooled FET is used for charge amplification. The detector resolution has been measured for a variety of ions in the mass range from He to Si and for energies between 0.5 and 8 MeV. The energy resolution of the ionization chamber surpasses the one of a state-of-the-art silicon charged particle detector for all ions heavier than Li. For Si ions the improvement in resolution is more than a factor of 2. The device does not suffer from any radiation damage. For He particles around 1 MeV the resolution is between 13 and 16 keV (FWHM). Therefore the new detector is not only well suited for heavy ion backscattering spectrometry but can also be applied for standard He RBS, allowing the use of a single detector for all types of projectiles in a wide energy range.     

On the extraction of neutralisation information from low energy ion scattering spectra

There are two different ways of measuring low energy ion scattering (LEIS), i.e. detection of ions and neutrals by means of time of flight (TOF-LEIS), or detection of ions only by means of an electrostatic analyser (ESA-LEIS). We discuss, how information on charge exchange can be extracted from ESA-LEIS and TOF-LEIS spectra, respectively and which is the level of accuracy that can be expected from these procedures.     

低能N+注入诱变选育威兰胶高产菌的研究

利用低能N 束对威兰胶生产菌进行了辐射诱变选育研究.能量为20keV,注入剂量为20×1014/cm-2时,筛选出一株高产菌株Alcaligenes sp.NX-3-1.结果表明,摇瓶发酵中诱变菌威兰胶产量比出发菌高27.5%;在7.5L发酵罐上,Alcaligenes sp.NX-3-1菌生长速度比出发菌快,生物量高,底物葡萄糖消耗量多,威兰胶产量较出发菌有明显提高,最高达26.4g·L-1.     

Investigation of avalanche silicon detectors for low energy single ion implantation applications

Avalanche silicon photodiodes have potential applications to detect low energy single ions for counting single ion impacts in shallow implant depths for the deterministic doping of nanoscale electronic devices. This paper reports the investigation of avalanche photodiode detectors in the linear operation mode for detection of 0.5–2 MeV helium ions. The measured charge gain was found to be up to 100 depending on bias voltage. The charge gain was found to saturate at a level that correlated with the ion stopping depth in silicon. The measured charge gain for energetic ions, which have a well-defined depth in a silicon substrate for the deposition of ionization energy, is compared with that of X-rays and photons, which deposit the ionization energy over a wider range of depth. This allowed the identification of a suitable structure for an avalanche photodiode optimised for the detection of sub-10 keV heavy ions with an internal charge gain above 10 achievable. This offers significant advantages over conventional PIN devices where the signals from such ions would be lost in the noise.