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Divertor Plasma Simulation Experiment Using Hydrogen Ionizing Plasma and Helium Ion Beam in an RF Plasma Source DT-ALPHA

Divertor Plasma Simulation Experiment Using Hydrogen Ionizing Plasma and Helium Ion Beam in an RF Plasma Source DT-ALPHA

Experiments were conducted using the RF plasma de- vice DT-ALPHA [8]. The schematic of the device is shown in Fig. 1. The device consists of a quartz pipe and a stain- less steel (SUS) vacuum chamber. The inner diameters of the quartz pipe and vacuum chamber are 36 mm and 63 mm, respectively. An RF antenna is wound around the quartz pipe, and it is connected with an RF ( f = 13.56 MHz) power supply through a matching circuit. The y and z axes are defined as illustrated in Fig. 1. At both ends of the device, end-plates are installed to terminate the plasma. The upstream end-plate has an aperture of 10 mm diameter. The working gas is supplied near the upstream end-plate. To enhance volumetric recombination, a sec- ondary gas puffing system is introduced at the downstream region (z = 1.58 m). In this experiment, hydrogen gas was utilized as the working gas. A secondary hydrogen gas was also supplied. To prevent back flow of the sec- ondary gas, two orifice units made by SUS were installed between the plasma production region and gas pu ffi ng re- gion. In the present experiment, the hydrogen neutral pres- sure measured at z = 0.98 m was approximately 1.4 Pa. At the upstream end of the device, a compact-type ion beam generator is combined with the DT-ALPHA. The details of the beam generator are described in Ref. 9. The plasma production method is a direct-current arc discharge. The extraction system consists of three electrodes, namely, the acceleration, deceleration, and grounded electrodes. An Einzel lens is equipped between the grounded electrode and the upstream end-plate to optimize ion beam transport. In this experiment, a helium ion beam of E = 10 keV was produced and injected into the DT-ALPHA device.

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Comparative study of beam induced carbonaceous deposits in helium ion and scanning electron microscopes

Comparative study of beam induced carbonaceous deposits in helium ion and scanning electron microscopes

The Electron Microscope (EM), including the Transmission Electron Microscope (TEM) and the Scanning Electron Microscope (SEM), have been powerful char- acterisation and analytical tools to investigate materials. Advances in EM in- strumentation are driven by the demands for higher resolution, which in turn enable breakthroughs in relevant fields and initiate novel research topics that seek higher resolution. For example, the spherical-aberration corrected TEM has been indispensable for recent achievements in the study of two-dimensional materials [1]. Nevertheless, there are still many characterisation challenges yet to be met by present EM technology, for example that of automated, sub-nanometer sur- face characterisation of insulating samples, which is of extreme importance to the continued development of semiconductor devices [2]. As a recent addition to the family of charged-particle microscopes [3], the Helium Ion Microscope (HIM) is a complementary tool to EM and has the potential to address these characterisation challenges. Compared with SEM, the HIM imaging has several advantages, such as a better lateral resolution, a larger depth of field, better surface sensitivity and material contrast, and a unique charging compensation mechanism [4–6]. A wide range of samples have been imaged using HIM, such as cancer cells [7], graphene [8–10], polymers [11, 12], etc. In terms of semiconductor applications, Secondary Electron (SE) dopant contrast imaging has been demonstrated in a SEM [13, 14], particularly by using a low-voltage scanning electron microscope [15, 16]. HIM imaging has also been used in efforts to quantify dopant concentration and a di- rect correlation between dopant concentration and SE intensity has been reported [17–19].

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Influence of helium ion bombardment on the optical properties of ZnO nanorods/p GaN light emitting diodes

Influence of helium ion bombardment on the optical properties of ZnO nanorods/p GaN light emitting diodes

ANSI_ANSLG C78, 377-2008 for the solid-state light sources which determines that the distance of 3 Mac- Adam ellipses form Planckian locus can be allowed for white light. The He+ ion-radiated LEDs are slightly decreased from the Planckian Locus and are very close to white light. They are about 4 Mac-Adam ellipses away from the Planckian Locus. The color-rendering indices are 92, 90, and 89 for the non-radiated and He + ion radiated with fluencies of approximately 2 × 10 13 ions/cm 2 and approximately 4 × 10 13 ions/cm 2 LEDs, respectively. It shows that there is only a small effect (3%) on the optical properties. So this might be a good observation for space and nuclear applications. The 2- MeV ions only have a minor effect on optical properties of the LED devise after irradiation with moderate fluences.

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Comparison of Ion Internal Transport Barrier Formation between Hydrogen and Helium Dominated Plasmas

Comparison of Ion Internal Transport Barrier Formation between Hydrogen and Helium Dominated Plasmas

drogen ion dominated and helium ion dominated plasmas. Figure 3 shows radial profiles of (upper) the amplitude of the density fluctuation, (middle) intensity of the wave number of the density fluctuation, and (bottom) intensity of phase velocity of the density fluctuation in the labora- tory frame. The density fluctuation with a frequency of 20 - 500 kHz are analyzed and plotted in Fig. 3. The den- sity fluctuation rotating in the direction of ion-diamagnetic drift with the wave number of 0.1 - 0.4 mm −1 was observed in the both plasmas with hydrogen ratio of 0.34 and 0.78. Although the mode identification is difficult from only the PCI observation, ion temperature gradient (ITG) mode was identified to be dominant mode in the high ion temper- ature discharges in LHD from the comparison between the experimental observation and gyrokinetic calculation [17–19]. The dominant mode observed in this experiment is very similar to that obtained in the previous experiment, thus the mode seems to be the ITG mode. The global char- acteristics of the density fluctuation observed with PCI, such as, the amplitude profile, peak level, wave number profile, rotation, etc. are almost identical between the two plasmas, while the ion heat transport is different between them. The observed wave number spectra seem to be rea- sonable, because the characteristics scale of ITG is deter- mined by the ion Larmor radius (ρ i ∼ (A 1 / 2 / Z), where A

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A comparison of He and Ne FIB imaging of cracks in microindented silicon nitride

A comparison of He and Ne FIB imaging of cracks in microindented silicon nitride

Sputtered carbon is an effective alternative to conductive gold coatings and its efficacy for improving the imaging of cracks in ceramic samples during gas-ion microscopy is investigated here. Fig. 7 shows a comparison of helium ion beam and neon ion beam ISE images taken sequentially of the same region of a radial crack extending from a 0.5 kg indentation on the carbon coated SN-2 silicon nitride (Fig. 7(a, b). The carbon coating is sufficiently thin that differential contrast from the different phases is preserved. In both helium (Fig. 7(a)) and neon (Fig. 7(b)) ISE images, there is a clear distinction between the alpha/ beta grains (dark contrast) and the intergranular glassy phase (light grey contrast). This is contrary to both the gold coated SN-1 sample where no contrast is visible, and the uncoated SN-1 sample where phase contrast is poor.

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Helium Volumetric Recombining Plasma Formation for Energetic Ion Injection in Radio-Frequency Plasma Device DT-ALPHA

Helium Volumetric Recombining Plasma Formation for Energetic Ion Injection in Radio-Frequency Plasma Device DT-ALPHA

As described above, another type of divertor plasma simulating device is required to reveal the divertor plasma dynamics induced by energetic ions. A linear plasma ma- chine with a radio-frequency (RF) plasma source is avail- able because a cylindrically wound RF antenna makes it possible to superimpose an energetic ion beam onto a tar- get plasma. The ionization and excitation reaction rates due to energetic ions would be comparable to those for thermal electrons of several eV. Therefore, ionization of ground-state neutral atoms due to energetic ions is ex- pected to be negligible. On the other hand, electrons of even several eV could re-ionize the Rydberg atoms pro- duced by volumetric recombination because the ionization potential of the Rydberg atoms is much smaller than that of the ground-state neutral atoms. Therefore, energetic ions, as well as several eV electrons, have a non-negligible a ff ect on the Rydberg atoms; thus, they could modu- late the ionization-recombination balance. Moreover, ions of around several keV have a large cross-section for the charge-exchange interaction, which transfers momentum from the fast ions to bulk neutrals. Therefore, redistri- bution of the ground-state/excited neutral atoms through the ion intrinsic reaction is concerned. For example, ener- getic helium ion injection into helium ionizing plasma in-

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A comparison of He and Ne FIB imaging of cracks in microindented silicon nitride

A comparison of He and Ne FIB imaging of cracks in microindented silicon nitride

Sputtered carbon is an e ff ective alternative to conductive gold coatings and its efficacy for improving the imaging of cracks in ceramic samples during gas-ion microscopy is investigated here. Fig. 7 shows a comparison of helium ion beam and neon ion beam ISE images taken sequentially of the same region of a radial crack extending from a 0.5 kg indentation on the carbon coated SN-2 silicon nitride (Fig. 7(a, b). The carbon coating is su ffi ciently thin that di ff erential contrast from the di ff erent phases is preserved. In both helium (Fig. 7(a)) and neon (Fig. 7(b)) ISE images, there is a clear distinction between the alpha/ beta grains (dark contrast) and the intergranular glassy phase (light grey contrast). This is contrary to both the gold coated SN-1 sample where no contrast is visible, and the uncoated SN-1 sample where phase contrast is poor.

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Dynamic Simulation of Multiplier Effects of Helium Plasma and Neutron Irradiation on Microstructural Evolution in Tungsten

Dynamic Simulation of Multiplier Effects of Helium Plasma and Neutron Irradiation on Microstructural Evolution in Tungsten

The damage due to neutron irradiation and the effect of helium produced by the plasma were considered simulta- neously in the present simulations. Although a large number of bubbles and interstitial-type dislocation loops were formed at the near surface by low-energy helium ion irradiation, we omitted defects produced by helium ions. Our main purpose in this study was to investigate the interaction between helium and point defects and their clusters in the matrix. The defect clusters formed at the near surface act as effective sinks for point defects and helium instead of the surface. Thus, these defect clusters do not affect the defect structural evolution in the matrix. Under the initial simulation con- ditions, in contrast to the uniform damage produced by neutron irradiation, the helium distribution had a rectangular shape with its center at 15 nm from the plasma facing surface and a width of 10 nm. Helium, interstitials, and vacancies could migrate freely in the matrix, and their concentrations at the surfaces facing towards and away from the irradiation were zero during the simulation. The changes of point defects, defect clusters and helium concentrations were calculated using the dynamic rate theory with the following assumptions:

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Effects of Dual Ion Irradiation on the Swelling of SiC/SiC Composites

Effects of Dual Ion Irradiation on the Swelling of SiC/SiC Composites

Monolithic (3C) -SiC specimens produced by the chemi- cal vapor deposition (CVD) process (Rohm and Hass Co., Woburn, USA) were used for the investigation of swelling. The disk-shaped specimens, size 3 mm in diameter and 0.25 mm in thickness, were cut and their surfaces were polished with diamond particles. The polished surface was covered with #200 molybdenum mesh. The irradiation experiments of single-ion (only Si ion) beam and dual-ion (Si ion and helium ion) irradiation were performed at up to 3 dpa. The irradiation temperature ranged from room temper- ature to 1400 C. The values of nominal flux and the helium over dpa were 1 10 3 dpa/s and 60 appm/dpa, respective- ly. The investigation of the swelling was performed by the step height method. The molybdenum mesh produced an unirradiated area on the surface. Steps were formed between the unirradiated and irradiated surfaces due to the swelling of irradiated SiC. Step heights were measured using an interferometric profilometry device (Micromap 128, Micro- map Co., Tucson, Arizona, USA), and the amount of swelling of SiC was calculated following the method reported in the previous work. 5)

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Electrospun collagen nanofibers for tissue engineering

Electrospun collagen nanofibers for tissue engineering

As shown in Table 9 for helium ion implantation, the ratio of amide to amine decreased as the ion dose increased, an indication that either the amide (peptide) groups were removed or converted into amine groups, most likely tertiary amines, as ion dose was increased. For the lowest dose of helium ion implanted (4x10 15 ions/cm 2 ) this ratio decreased from 92:8 ratio (untreated) to 70:30. This trend decreased further to 65:35 as He + dose was increased to 8x10 15 ions/cm 2 and eventually to 48:52 at the highest experimental dose of helium ion of 12x10 15 ions/cm 2 . This trend is reasonable as an increase in ions would lead to and increase in amide bond breaking leading to the observed decrease in the ratio of the two peaks. Nevertheless, the He+ ions served to transfer energy the break the chemical bonds to allow for crosslinks to be formed. This leads to the observed aqueous stability of the He + implanted collagen nanofibers.

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Tungsten 'fuzz' growth re-examined: the dependence on ion fluence in non-erosive and erosive helium plasma

Tungsten 'fuzz' growth re-examined: the dependence on ion fluence in non-erosive and erosive helium plasma

the exposure time, this can be equated to a deposition layer and subtracted from the overall thickness, as shown in brackets in table A1. Since SEM observation of the fuzz morphology is similar to fuzz in other non UoL work, it is assumed that the deposited tungsten incorporates into the growing fuzz layer in a manner similar to that described by tungsten atom movement along tendrils, as proposed in [19]. The revision, which removes the influence of the deposition, places the data points closer to other nearby data that pertain to plasma exposure without an incident tungsten atom flux. The significance of this correction, however, should not be minimized. The uncorrected results are evidence that tungsten atom deposition leads to a potential enhancement of fuzz growth relative to non deposition regimes, and as such, warrants further investigation. Implications, for an all tungsten metal reactor scenario, are that tungsten codeposits might therefore manifest with fuzz like structure provided the requisite deposition temperature and He ion flux are also present.

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Sensitized fluorescence in potassium vapour.

Sensitized fluorescence in potassium vapour.

Sensitized fluorescence of potassium vapour was investiga­ ted to determine the cross-sections for collisions of a second kind occurring between potassium and potassium, potassium and helium, and potassium and argon atoms. The experiments involved the use of an idealized fluorescence tube and the application of a red- sensitive photomultiplier tube. Corrections for effects due to the imprisonment of radiation were made by extrapolating the results to zero pressure. The following values were obtained: (4 Pj/p ^2P y 2 ) = 95 x 10^ cm2 and Q2 ( & y 2 ^ p y 2 ) = 83 * 10_ll+ cm2 for potassium-potassium collisions; Q1 = 1.5b x 10 cm2 and

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Applications of the Variational Quantum Monte Carlo Method to the Two-Electron Atoms

Applications of the Variational Quantum Monte Carlo Method to the Two-Electron Atoms

A series of papers have been presented to study the correlated wave functions and their effect on the calculated energies. U. Kleinekathöfer et.al [3] proposed a simple non- variational wave function of the two-electron atoms. The electron-electron correlation described by an ansatz that has the correct behavior for and = ∞ . An additional parameter calculated from a perturbation calculation to the ground-state energies for the helium like atoms with ( = 1 – 10 ) and illustrates the importance of asymptotic behavior and the correlation factor to the values of calculated energies. It is the first successful derivation of a non- variational wave function for simple two-electron atoms and ions. Because of its simplicity and accuracy, this wave function should prove very useful for calculating the effect of the collective properties of two-electron systems. It should also be possible to extend this treatment to excited states, diatomic molecules and atom surface interactions.

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Mechanism of collision induced decomposition of gaseous multiatomic ions

Mechanism of collision induced decomposition of gaseous multiatomic ions

The results for valinomycin have shown how by increasing the incident ion energies accessible on a hybrid mass spectrometer, tandem mass spectra may be obtained w hich more closely resem ble those obtained by 4-sector mass spectrometry. Similar work has also been carried out for the [M+H]+ ion of the peptide dynorphin A fragment 1-9 (m/z 1137.5) and the [M+HJ+ ion o f the cyclic peptide gramicidin S (m/z 1141.7).177 These peptides were used previously in comparisons between hybrid and 4-sector tandem m ass spectra, where CID on the hybrid resulted in low efficiencies for fragm enting these ions.86*87 By increasing the collision energy to 400 eV in this m ore recent study, 177 additional fragmentation could be induced although a number o f w-, v- and d-type fragment ions observed in the 4-sector spectrum were still absent in the low-energy case. For the [M+H]+ ion o f insulin A-chain (m/z 2531), only the CID spectra recorded with incident ion energies above 300 eV resulted in a significant amount of fragmentation. 177 The spectrum did not provide complete structural information, but again illustrated the potential o f using higher collision energies in a hybrid mass spectrometer to promote fragmentations o f ions with much higher masses. Overall, the results suggest that if incident ion energies of the order o f keV could be achieved on hybrid instruments, then tandem m ass spectra might be obtained which are similar to those obtained by 4-sector instruments. This would be the case provided that the efficiency o f transm ission through the quadrupole assembly could also be maintained with the use o f increasingly higher RF- voltages. The possible use of keV collision energies in hybrid instruments should provide a means of fragmenting even larger system s, at least to the extent which can be achieved in a 4-sector mass spectrometer. However, the limitations of resolution and sensitivity which can be achieved with a quadrupole assembly will

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Precision X-ray spectroscopy of kaonic atoms as a probe of low-energy kaon-nucleus interaction

Precision X-ray spectroscopy of kaonic atoms as a probe of low-energy kaon-nucleus interaction

The strong interaction induced 2 p level shift and width are measured for both kaonic helium-3 and helium-4 atoms, and it is the first time that kaonic helium-3 X-rays are measured. The results of the shift as listed in 1 are consistent with the results of E570 [3], thus a zero-compatible shift of the 2 p level from experiment is established, which is in agreement with the theoretical estimations in [6, 15]. We have not found abnormally large widths which can directly support the estimations made in conjunction with the prediction of a deeply-bound kaon states[7, 8].

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Performance Analysis of a Helium Turboexpander for Cryogenic Applications with a Process Modeling Tool: Aspen HYSYS

Performance Analysis of a Helium Turboexpander for Cryogenic Applications with a Process Modeling Tool: Aspen HYSYS

Turboexpander is a machine, which continuously converts kinetic energy into mechanical energy. This is done by expanding the high pressure gas from upstream to a lower pressure downstream through the expander. The high pressure gas causes the radial expander to rotate. Rotation is transmitted to the shaft, which is supported by a set of bearings.The energy transmitted to the shaft can be used to drive a compressor (i.e. wastage of energy can be prevented). Figure 1. shows a helium turboexpander, that is , helium gas is used as a process sample gas[5][6][7][8][9].

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Energy Consumption Analysis and Comparison of HPC and HPS of  HTR-10

Energy Consumption Analysis and Comparison of HPC and HPS of HTR-10

reactors, CEA has started to build up some helium loops. To test the components, representative conditions have to be reached: temperature, pressure and chemical gaseous composition. To control the chemical composition at impurities low level contents, HPC is designed to purify and to adjust the composition of the helium contained in the loop. It represents 72kg/h of helium and only the gaseous contaminants are controlled. From the point of energy consumption, the purification system of HPC is schematically shown below in fig. 1. At the end of 2006, they had the first reception of components. And the facility will be available for its experimental program at mid 2007 [5] .

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Energy levels in muonic helium

Energy levels in muonic helium

Abstract. The energy spectrum of bound states and hyperfine structure of muonic helium is calculated on the basis of stochastic variational method. The basis wave functions of muonic helium are taken in the Gaussian form. The matrix elements of the Hamiltonian are calculated analytically. For numerical calculation a computer code is written in the MATLAB system. As a result, numerical values of bound state energies and hyperfine structure are obtained. We calculate also correction to the structure of the nucleus, vacuum polarization and relativistic correction.

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A comprehensive global oceanic dataset of helium isotope and tritium measurements

A comprehensive global oceanic dataset of helium isotope and tritium measurements

The third method, 3 He ingrowth, is a three-step method. First, it involves degassing of a quantity (∼ 1 to 1000 mL) of water to remove all dissolved helium. Second, the degassed water is stored in a helium leak-tight container (usually low- He-permeability aluminosilicate glass or metal) for a period of several weeks to a year or more. Experience indicates that it is necessary to shelter the stored samples from cos- mic rays since there is a latitude-dependent cosmogenic 3 He production rate that masquerades as “tritium signal” (Lott and Jenkins, 1998). Finally, the ingrown 3 He is extracted from the water sample and mass spectrometrically analyzed (Clarke et al., 1976; Ludin et al., 1997). The last method, al- though it involves a potentially lengthy incubation period, is chemically simpler and does not involve isotopic enrichment steps. As such, it offers intrinsically greater accuracy (limited by standardization of the mass spectrometer, typically better than 1 %) and a lower ultimate detection limit (Jenkins et al., 1983; Lott and Jenkins, 1998).

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Superconductivity and Superfluidity   Part III: Superfluidity as a Consequence of Ordering of Zero point Oscillations

Superconductivity and Superfluidity Part III: Superfluidity as a Consequence of Ordering of Zero point Oscillations

This approach permit to explain the mechanism of su- perfluidity in liquid helium. For electron shells of atoms in s-states, the energy of interaction of zero-point os- cillations can be considered as a manifestation of Van- der-Waals forces. In this way the opposite quantitative estimations of temperatures of the helium liquefaction and its transition to the superfluid state was obtained.

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