Evaluation of carbon stripper foils produced by a nitrogen ion beam sputtering method

Carbon stripper foils having thicknesses in the range of 5–40 μg/cm² have been prepared by a nitrogen ion beam sputtering method and their lifetimes have been tested in the Van de Graaff accelerator facility with 3.2 MeV, Ne⁺ ions. The foils of 21 μg/cm² thickness had the longest mean lifetime of 1350.0 mC/cm² (irradiation dose of 8.4×10¹⁸ atoms/cm²) which was 50 times longer than that of commercial foils. However, foils with other thicknesses had extremely short lifetimes similar to commercial foils. The nitrogen content of the foils of both long and short lifetimes has been determined using elastic scattering of 3 MeV α-particles.     

The temperature dependence of internal friction in SicPCS/Al composites

In this study the relationship between Q^-1 and the microstructural characteristics of SiC_PCS/Al composites was investigated. Seven specimens made by various processes were divided into three groups and their Q^-1-T spectra were compared. The temperature dependence of internal friction up to 500°C was measured by vacuum inverse torsional pendulum apparatus. For the SiC_PCS/Al composite fabricated by the liquid infiltration method, Q^-1 increased more and more rapidly with rising temperature when the extent of fiber-matrix interfacial reaction intensified. For hot-pressed plates fabricated from preform wires and Al(1050) foils, poor diffusion bonding between the preform wires and A1 foils was introduced; this new interface is primarily responsible for the temperature dependence of Q^-1.     

Collection and behaviour of radon progenies on thin Mylar foils

Thin Mylar foils are often used to protect detectors from contamination. However, these foils can be electrostatically charged, possibly leading to their contamination with airborne radon progenies. In the present work, the collection and behaviour of radon progenies on Mylar foils was investigated in detail using alpha spectrometry. The radon progenies collection rate of a small Mylar foil (3 cm²) is equivalent to an air sampler with a flow rate of approximately 0.1 m³/h. It was demonstrated that such contamination may jeopardise the validity of the entire analysis if not interpreted correctly.     

Anomalous burn-through of thin foils by high-intensity laser radiation

The paper presents results of experiments performed on the Pico facility in which foils were heated by laser radiation, and anomalously fast burn-through of foils by a structured laser beam was detected. Comparison with two-dimensional calculations has allowed us to suggest a tentative mechanism for the effect under investigation. The targets in the experiments were thin aluminum foils of thickness 3 to 40 μm. The flux density of laser radiation on the target surface varied between 10¹³ and 10¹⁴ W/cm². We detected a strong dependence of the transmitted energy on the foil thickness and the shortening of the transmitted laser pulse. Penetration of laser radiation through foils with thicknesses considerably larger than 3 μm has been observed, although it was stated in earlier publications [V. V. Ivanov, A. K. Knyazev, A. V. Kutsenko, et al., Kratk. Soobshch. Fiz. FIAN No. 7–8, 37 (1997)]; A. é. Bugrov, I. N. Burdonskii, V. V. Gol’tsov et al., Zh. éksp. Teor. Fiz. 111, 903 (1997) [JETP 84, 903 (1997)] that, at the laser radiation parameters used in our experiment, the evaporated layer of the foil could not be thicker than 2 μm. Two-dimensional calculations have allowed us to interpret this effect in terms of local “piercing” of the target at spots on the target surface where the radiation intensity has its peaks. The possibility of reducing these peaks by using a symmetrizing prepulse is discussed in the paper. Zh. éksp. Teor. Fiz. 116, 1287–1299 (October 1999)     

Comparison of Surface-Enhanced Raman Scattering Spectra of Azo Dye Sudan III on Several Substrates

On several substrates, including dried silver-coated filter paper, electro-polishing aluminum foils, and anodic aluminum oxide (AAO) nanometer array templates, surface-enhanced Raman scattering (SERS) spectra of Azo Dye Sudan III molecules were studied, and high-quality SERS spectra were obtained, which indicated that electro-polishing aluminum foils and AAO nanometer array templates were also active SERS substrates. A number of additional modes were presented, as well as some split peaks, which were especially obvious on electro-polishing aluminum foil and AAO nanometer array template. The enhancement mechanisms were discussed and the enhancement factors G were calculated as 10⁴, 10⁶, and 10⁵, respectively.     

Influence of radiation damage on the hyperfine field of triton irradiated nickel foils

The recently observed Mössbauer effect in⁶³Ni enables the study of the hyperfine field in nickel with high resolution. In the present paper, the line broadening of the Mössbauer resonance is analyzed in order to study the influence of radiation damage on the magnetic hyperfine field in⁶⁴Ni foils. Each of these foils was irradiated by tritons at 15 K with a total current integral of 2.4 A h in order to produce the short-lived⁶³Co sources (T _1/2=27 s). An upper limit of 4.6 kG was estimated for the standard deviation of the magnetic hyperfine field distribution which resulted from the accumulated radiation damage. For the annealed absorber material the standard deviation of the magnetic field is less than 53 G.     

HD+2，H+3和D+3与固体相互作用和三体尾流效应

从分子离子H⁺₃及其氘化同位素分子离子D⁺₃和HD⁺₂与超薄固体膜相互作用发生库仑爆炸为基础,分析讨论了H⁺₃,D⁺₃和HD⁺₂三种分子离子的形成机理,根据产物能谱分布,利用库仑爆炸技术确定了同位素分子离子HD⁺₂的结构形式,给出具体核间距数值.并确定在实验中不存在线状结构的HD⁺₂.提出一种三原子分子离子和固体相互作用中尾流效应的处理方式,通过和实验结果做比较发现这是一种非常理想的处理三体尾流效应的模式,并用之进一步确认了HD⁺₂的结构形状.文章对H⁺₃,D⁺₃和HD⁺₂三种分子离子的实验结果做了对比和讨论. 关键词： +₂')" href="#">微团簇HD⁺₂ +₃和D⁺₃')" href="#">H⁺₃和D⁺₃ 库仑爆炸 三体尾流势 团簇结构     

The transient hyperfine field at Si,Pd and Pt ions traversing iron and nickel foils

A measurement of the hyperfine interactions on swift²⁸Si,¹¹⁰Pd, and¹⁹⁴Pt ions recoiling through magnetized iron and nickel foils indicates that for these ions the strength of the transient magnetic field scales with the net magnetization of the ferromagnet.Supported in part by the National Science Foundation.     

Fabrication and characterization of freestanding ultrathin diamond-like carbon targets for high-intensity laser applications

Here, we report the fabrication of diamond-like carbon (DLC) thin films using pulsed laser deposition (PLD). PLD is a well-established technique for deposition of high-quality DLC thin films. Carbon tape target was ablated using a KrF (248 nm, 25 ns, 20 Hz) excimer laser to deposit DLC films on soap-coated substrates. A laser fluence between 8.5 and 14 J/cm² and a target to substrate distance of 10 cm was used. These films were then released from substrates to obtain freestanding DLC thin foils. Foil thicknesses from 20 to 200 nm were deposited using this technique to obtain freestanding targets of up to 1-inch square area. Typically, 100-nm-thick freestanding DLC films were characterized using different techniques such as AFM, XPS, and nano-indentation. AFM was used to obtain the film surface roughness of 9 nm rms of the released film. XPS was utilized to obtain 74 % sp², 23 % sp³, and 3 % C–O bond components. Nano-indentation was used to characterize the film hardness of 10 GPa and Young’s modulus of 110 GPa. Damage threshold properties of the DLC foils were studied (1,064 nm, 6 ns) and found to be 7 × 10¹⁰ W/cm² peak intensity for our best ultrathin DLC foils.     

Cross sections for monitor reactions 27Al((p, x)24Na, 27Al(p, x)22Na, and 27Al(p, x)7Be at proton energies in the range 0.04–2.6 GeV

The cross sections for the monitor reactions ²⁷Al(p, x)²⁴Na, ²⁷Al(p, x)²²Na, and ²⁷Al(p, x)⁷Be at 12 proton energies, 2605, 1598, 1199, 799, 600, 400, 249, 147.6, 97.2, 66.0, 44.6, and 40.8 MeV, have been determined with 72 × 72-mm square and 10.5-mm-diameter round aluminum foils. The rates of the reactions of the production of ²⁴Na, ²²Na, and ⁷Be in the foils in each irradiation run have been determined by γ spectrometry, whereas the number of protons transmitted through these foils has been determined using calibrated fast current transformers. The cross sections have been determined as the ratios of the corresponding reaction to the average proton fluence.     

Laser-triggered quasi-monoenergetic ion beams at a moderate intensity and pulse duration

Plasma produced by short laser pulses from thin homogeneous foils with light and heavy ions is capable of generating quasi-monoenergetic light ions. This happens for the tail of light ions near the front of heavy ions. It was found that this effect is well pronounced for a moderate laser intensity (～10¹⁸ W/cm²) and pulse duration (～1 ps) by using a 2D particle-in-cell simulation of the laser interaction with thin CD₂ foils. Quasi-monoenergetic deuterons form a jet from the rear side of the foil with the energy ～1 MeV. The conversion efficiency to these quasi-monoenergetic ions is 10^?3.     

Perturbations of alpha-gamma angular correlations in the decay of230U and226Th

Perturbations of α-γ angular correlations in the decay of²³⁰U and²²⁶Th, involving the 2⁺ states in²²⁶Th and²²²Ra, have been studied using²³⁰U sources prepared by evaporation of the activity on Al foils, and²²⁶Th sources, prepared by collecting recoil nuclei from a²³⁰U source on Al foils. In vacuum, perturbation coefficients are found to be in agreement with the “hard-core-value” for static magnetic interaction. The perturbations in aluminum are found to be strongly dependent on the method of source preparation.     

Determination of the Products of Irradiation of Natural Molybenum By Deuterons with Energy up to 13 MeV by Means of Semiconductor Gamma- and X-Ray Spectrometry

Introduction

Among the products of irradiation of natural molýbdenum by deuterons with energies up to 13 MeV, by means γ and X-ray speclrometry were identified these radlonudldes: ⁹⁹Nb, ^92mNb, ^95m+gNb ⁹⁶Nb, ⁹⁹Mo, ¹⁰¹Mo, ⁹²Tc, ^93m+gTc, ^94m+g^>Tc, ^95m+gTc, ⁹⁶Tc, ^97mTc, ^99mTc,¹⁰¹Tc, and ⁸⁹Zr. With the more intensive lines of γ transitions of ⁹⁰Nb, ⁹⁶Nb, ^93m+gTc, ^94m+gTc, ^95m+gTc, ⁹⁹Tc and ^97mTc accurate photon energies have been established and for the lines 1475.7 and 1520.5 keV of ⁹³Tc, 820.2 keV of ^95mTc, and 96.4 keV of ^97mTc also the absolute intensities of the emitted γ were determined. By means of aluminium foils, by which the set of Mo foils had been interlaid, the atomic recoil in forward and backward direction ivas established for the 17.82 mg/cm² Mo foils and deuteron energy up to 12.7 MeV and the ion current of 3.4 μA.     

Evidence for long-range fission fragments induced by irradiation with electrons

In search of natural superheavy elements, long-range fission fragments penetrating up to 73 μm of mylar were observed, when thick metallic foils of U, Pb and W, covered with six mylar foils were irradiated with 550 MeV or 1300 MeV electron beams. The cross section is of the order of 10⁻³⁰ cm². The effect is produced in natural U, Pb, W and similarly in mass separated ²⁰⁸Pb and ¹⁸⁶W isotopes — not by fission of a superheavy element.     

Preparation of metal foils from deformed specimens of small dimensions for transmission electron microscopy

A method of preparing thin metal foils from Fe-Si single crystals suitable for transmission electron microscopy is described in this paper. In contrast to methods used hitherto foils can be prepared from platelets having a very small area (0·07 cm²), the place in the specimen under observation can be located with an accuracy of ±0·1 mm and its orientation with respect to the edges of the platelet can be ascertained.     

Magnetic moment measurements of picosecond states: New results and open problems

The temperature dependence of the precession of the angular correlation of decay gamma rays from swift¹⁵⁰Sm (2 ₁ ⁺ ) ions traversing a gadolinium foil has been found to be proportional to the foil magnetization, supporting the assertion that the transient hyperfine magnetic field acting on these ions is proportional to the magnetization of the hosts (iron or gadolinium). Similar experiments on¹⁹⁴Pt (2 ₁ ⁺ ) ions traversing iron and gadolinium foils are consistent with both the magnetic moment obtained from Rutgers experiments on iron and with a hyperfine field at Pt ions larger for gadolinium than for iron foils, in agreement with the Chalk River parametrization for heavy nuclei traversing gadolinium foils. Finally, the magnetic moments of the 2 ₁ ⁺ states in^144–150Nd,^145,150Sm and¹⁵²Gd have been measured. These data support the evidence of shell closure atZ=64 forN≤88 andZ=50 forN>90.     

Nonequilibrium effects in the energy loss of He+ beams in very thin carbon foils

We have investigated the energy loss of the single-charged fraction of beam transmitted through extremely thin carbon foils bombarded with He⁺ projectiles having energies from 1.5 to 2.4 MeV. A reduced energy loss, leading to an effective charge of 1.1 ± 0.3, was observed for the He⁺ component that is transmitted without charge exchange in the target, strongly supporting the idea that this component keeps its bound electron when passing through the target.     

Activation detection using indium foils for simultaneous monitoring neutron and photon intensities in a reactor core

In this work, the time-sequential changes in neutron and photon intensities in the core of a research reactor were monitored for 330 days following the time of shutdown. Indium foils, used as activation detectors, were irradiated during different time periods in the core. The activated nuclides ^116m1In and ^115mIn were measured and their activities were used as indices of the changes in neutron and photon intensities during the period of interest. Photon and neutron sources that may have been responsible for the activation reactions with indium foils were identified. The activities of both ^116m1In and ^115mIn rapidly decreased in the first 20 h (Phase I), and subsequently their activity levels were proportionally varied with ¹⁴⁰La activity between 20 and 3000 h (Phases II and III). After 3000 h (Phase IV), neutron fluence rate slowly decreased to levels of less than 10 cm^?2 s^?1. Then, the main neutron sources were identified as the neutron-emitting transuranic nuclides and the most important photon source that activated indium to form ^115mIn was identified as ⁶⁰Co. The activation detectors based on indium foils were found to be effective for simultaneously monitoring the variations of neutron and photon levels in reactor cores under sub-critical conditions.     

Polymer foil applicable to the tilted foil technique

A polymer foil of polyethylene-terephthalate was successfully used for the tilted foil to create nuclear polarization of beta-emitters. The foil was carefully prepared to produce atomic flatness on the surfaces. The resultant smoothness was confirmed with beta-NMR measurements on¹²B and found to be as good as those of carbon foils used previously in the measurements.     

Study of defect evolution by TEM with in situ ion irradiation and coordinated modeling

The paper describes a novel transmission electron microscopy (TEM) experiment with in situ ion irradiation designed to improve and validate a computer model. TEM thin foils of molybdenum were irradiated in situ by 1?MeV Kr ions up to ～0.045 displacements per atom (dpa) at 80°C at three dose rates ?5?×?10^?6, 5?×?10^?5, and 5?×?10^?4?dpa/s – at the Argonne IVEM-Tandem Facility. The low-dose experiments produced visible defect structure in dislocation loops, allowing accurate, quantitative measurements of defect number density and size distribution. Weak beam dark-field plane-view images were used to obtain defect density and size distribution as functions of foil thickness, dose, and dose rate. Diffraction contrast electron tomography was performed to image defect clusters through the foil thickness and measure their depth distribution. A spatially dependent cluster dynamic model was developed explicitly to model the damage by 1?MeV Kr ion irradiation in an Mo thin foil with temporal and spatial dependence of defect distribution. The set of quantitative data of visible defects was used to improve and validate the computer model. It was shown that the thin foil thickness is an important variable in determining the defect distribution. This additional spatial dimension allowed direct comparison between the model and experiments of defect structures. The defect loss to the surfaces in an irradiated thin foil was modeled successfully. TEM with in situ ion irradiation of Mo thin foils was also explicitly designed to compare with neutron irradiation data of the identical material that will be used to validate the model developed for thin foils.