共查询到20条相似文献,搜索用时 31 毫秒
1.
I. P. Chernov S. V. Ivanova M. Kh. Krening N. Koval’ V. V. Larionov A. M. Lider N. S. Pushilina E. N. Stepanova O. M. Stepanova Yu. P. Cherdantsev 《Technical Physics》2012,57(3):392-398
A pulsed action of an electron beam on a Zr-1% Nb zirconium alloy is studied. Alloy samples are irradiated by three 50-μs
pulses at an energy density of 15–25 J/cm2, a power of (3–6) × 104 W/cm2, a current density of 10–50 A/cm2, and an electron energy of 18 keV. This method of processing is found to modify the surface layer of the alloy without changing
the structure-phase state of its volume. This surface modification increases the hydrogen saturation resistance of the alloy. 相似文献
2.
I. P. Chernov E. V. Berezneeva P. A. Beloglazova S. V. Ivanova I. V. Kireeva A. M. Lider G. E. Remnev N. S. Pushilina Yu. P. Cherdantsev 《Technical Physics》2014,59(4):535-539
The physicomechanical properties of the surface of the Zr-1% Nb zirconium alloy modified by a pulsed carbon ion beam with a pulse duration of 80 ns, an energy of 200 keV, and a current density of 120 A/cm2 are studied at four regimes having different numbers of pulses. Irradiation by a carbon ion beam results in hardening of the surface layer to a depth of 2 μm, grain refinement to 0.15–0.8 μm, zirconium carbide formation, and a decrease in the hydrogen permeability of the zirconium alloy. 相似文献
3.
I. P. Chernov Yu. P. Cherdantsev A. M. Lider G. V. Garanin N. N. Nikitenkov A. V. Skirnevskii 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(6):691-697
The accumulation of hydrogen and defects in the E-125 zirconium alloy (Zr-2.5% Nb) is investigated. The hydrogen concentration is maximum on the surface of zirconium alloy samples after electrolytic hydrogenation. The hydrogen concentration decreases at a depth of about 0.5 μm and then gradually grows with increasing depth. The surface of the zirconium alloy is strengthened and becomes more fragile after hydrogenation. A plastic deformation of the zirconium alloy gives rise to traps with different binding energies of hydrogen. The primary type of traps, the binding energy, and the amount of hydrogen captured by traps depend on the deformation magnitude and the sequence of deformation and hydrogenation processes. High mobility of hydrogen in plastically deformed samples is observed under bombardment of the surface of the zirconium alloy by a helium ion beam with an energy of 2.34 MeV. The variation of the hydrogen concentration in the near-surface region of zirconium under ion bombardment depends on the extent of deformation: upon bombardment by helium ions, the hydrogen concentration in the near-surface region of the metal increases for deformations from 1 to 3% and decreases for deformations of 4 and 5%. 相似文献
4.
R. Pohl H. Daniel F. J. Hartmann P. Hauser Y. W. Liu F. Kottmann C. Maierl V. E. Markushin M. Mühlbauer C. Petitjean W. Schott D. Taqqu 《Hyperfine Interactions》2001,138(1-4):35-40
Kinetic energy distributions of muonic hydrogen atoms μp(1S) have been obtained by means of a time-of-flight technique for
hydrogen gas pressures between 4 and 64 hPa. A high energy component of ∼900 eV observed in the data is interpreted as the
signature of long-lived μp(2S) atoms, which are quenched in a non-radiative process leading to the observed high energy: the
collision of a thermalized μp(2S) atom with a hydrogen molecule H2 results in the resonant formation of a {[(ppμ)+]*pee}* molecule. Then the (ppμ)+ complex undergoes Coulomb de-excitation and the ∼1.9 keV excitation energy is shared between a μp(1S) atom and one proton.
The preliminary analysis of the time spectra gives a long-lived μp(2S) population of ∼1% of all stopped muons, and a quenching
rate of ∼4⋅1011 s−1.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
T.M. Huber A. Adamczak J.M. Bailey G.A. Beer J.L. Beveridge B.P. Ellerbusch M.C. Fujiwara R. Jacot-Guillarmod P. Kammel S.K. Kim P.E. Knowles A.R. Kunselman G.J. Lindquist M. Maier V.E. Markushin G.M. Marshall C.J. Martoff G.R. Mason F. Mulhauser A. Olin C. Petitjean T.A. Porcelli J. Woźniak J. Zmeskal 《Hyperfine Interactions》1999,118(1-4):159-161
In recent TRIUMF experiments, a μ- beam is stopped in a solid hydrogen film with a small fraction of T2. The Ramsauer-Townsend (RT) mechanism allows μt to escape into vacuum with a few eV of energy. To study the emission process, an imaging system was used to determine the
position of muon decays. Experimental histograms are in good agreement with a Monte Carlo simulation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
T. A. Alekhova V. Ya. Shklover N. A. Zagustina N. V. Shvyndina A. D. Plotnikov A. L. Vasil’ev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(5):747-753
The surfaces of AMg6 (aluminum-magnesium) alloy samples that have passed accelerated biocorrosion tests have been investigated
in a Quanta-3D scanning electron microscope. The alloy samples have been treated with the Ulocladium botrytis Preuss fungus, which is an active destructive fungus and was previously extracted on surfaces of the International Space Station.
Biocorrosion pits 2–10 μm in diameter, cavities the depths of which can reach 70–250 μm depth, and spots of modified color
are found to be the most typical defects. The surfaces of large cavities consist of faceted cubic particles that are formed
when the acid products of fungus metabolism interact with the alloy surface. The particles have an average size of 30 μm,
which is close to the size of alloy grains. The microstructure of a biocorrosion layer has been investigated in a Quanta-3D
microscope with the use of a focused Ga+ ion beam. The samples of 12-μm-wide transverse slices are obtained near large cavities and investigated in a Tecnai G230ST transmission electron microscope. The X-ray microanalysis of the defective layer has revealed the high concentration of
oxygen in this layer. Obtained images indicate that the corrosion cavity surface has a complex porous structure. 相似文献
7.
B. M. Forster J. M. Bailey G. A. Beer J. L. Beveridge J. H. Brewer W. N. Hardy T. M. Huber K. R. Kendall A. R. Kunselman J. A. Macdonald G. M. Marshall G. R. Mason A. Olin M. Senba J. B. Warren 《Hyperfine Interactions》1991,65(1-4):1007-1013
Muonic hydrogen isotopes (μ− p, μ− d, and μ−t) are simple quantum mechanical systems ideally suited for studies of numerous fundamental phenomena in electroweak and strong
interactions as well as in applied areas such as muon chemistry or muon catalyzed fusion.
Emission of muonic hydrogen isotopes into vacuum helps to overcome the limitations which are normally imposed on conventional
investigations with gaseous and liquid targets. A proof of principle experiment for this new technique was performed at TRIUMF
last year. Negative muons with 30 MeV/c momentum were stopped in a thin film of solid hydrogen and produced very low energy μ−d in vacuum. The distribution center of the normal velocity components of emitted μ−d atoms was measured to be ∼1 cm/μs. The yield of μ−d in vacuum is an increasing function of H2 film thickness δ up to a value of δ≥1 mm. 相似文献
8.
R. H. Scheicher A. N. U. Roy T. P. Das K. Ishida T. Matsuzaki S. N. Nakamura N. Kawamura K. Nagamine 《Hyperfine Interactions》2001,138(1-4):387-395
The study of trapping of He+ ion in solid hydrogen is important both as a problem in solid state physics and also as an applied physics problem in the
field of muon catalyzed fusion (μCF). In μCF, He+ ion acts as a trap for μ−, interrupting the chain reaction aspect of the catalytic role of μ− in producing fusion of deuteron and triton and of triton and triton in solid hydrogen composed of 2H–3H and 3H–3H molecules, respectively. Using the Hartree–Fock procedure, combined with procedures for including many-body effects, as
well as relaxation effects associated with the He+–H2 distances and the adjustment of the H–H separation, we have investigated the trapping of He+ in gaseous and solid state environments. For the former, the environment of He+ is simulated by a single hydrogen molecule and for the solid by clusters appropriately chosen to represent the hexagonal
close-packed structure. Our results for the gaseous state indicate that the trapping is rather strong with a binding energy
of 8.5 eV, with almost equal binding energy in the linear and triangular configurations with respect to the H–H direction.
For the solid, both the likely sites for He+ trapping, namely the tetrahedral and octahedral interstitial sites, are also found to provide deep traps (8.6 eV) of almost
equal strength, independent of the orientations of the neighboring molecules, showing that the trapping is not influenced
by the orientational disorder in the surrounding hydrogen molecules. Further, the influence of next nearest neighbor hydrogen
molecules is found to enhance the trapping energy for He+ substantially, by 0.6 eV, with the incorporation of the third nearest neighbors having a much smaller added effect, demonstrating
the convergence of our results with respect to the size of the cluster chosen to simulate the solid. The substantial influence
on the He+ trapping energy found for the neighbors beyond the nearest ones provides an explanation of the greater accumulation of helium
in the solid state of hydrogen in μCF experiments as compared to the liquid. Suggestions are made regarding the possible reasons
for the almost negligible accumulation of helium in the liquid state.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Prokscha T. Birke M. Forgan E. Glückler H. Hofer A. Jackson T. Küpfer K. Litterst J. Morenzoni E. Niedermayer Ch. Pleines M. Riseman T. Schatz A. Schatz G. Weber H.P. Binns C. 《Hyperfine Interactions》1999,120(1-8):569-573
At the Paul Scherrer Institute slow positive muons (μ+) with nearly 100% polarization and an energy of about 10 eV are generated by moderation of an intense secondary beam of surface
muons in an appropriate condensed gas layer. These epithermal muons are used as a source of a tertiary beam of tunable energy
between 10 eV and 20 keV. The range of these muons in solids is up to 100 nm which allows the extension of the μ+SR techniques (muon spin rotation, relaxation, resonance) to the study of thin films. A basic requirement for the proper interpretation
of μ+SR results on thin films and multi-layers is the knowledge of the depth distribution of muons in matter. To date, no data
are available concerning this topic. Therefore, we investigated the penetration depth of μ+ with energies between 8 keV and 16 keV in Cu/SiO2 samples. The experimental data are in agreement with simulated predictions. Additionally, we present two examples of first
applications of low energy μ+ in μ+SR investigations. We measured the magnetic field distribution inside a 500-nm thin High-TC superconductor (YBa2Cu3O7-δ), as well as the depth dependence of the field distribution near the surface. In another experiment a 500-nm thin sample
of Fe-nanoclusters (diameter 2.4(4) nm), embedded in an Ag matrix with a volume concentration of 0.1%, was investigated with
transverse field μ+SR.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
V. S. Kulhar 《Pramana》2004,63(3):543-551
The muonium/muonic hydrogen atom formation in μ±−H collisions is investigated, using a two-state approximation in a time dependent formalism. It is found that muonium cross-section
results are similar to the cross-section results obtained for positronium formation in e+-H collision. Muonic hydrogen atom formation cross-sections in μ--H collision are found to be significant in a narrow range of energy (5 eV–25 eV). 相似文献
11.
R. Pohl F. Biraben C.A.N. Conde C. Donche Gay T.W. Hänsch F.J. Hartmann P. Hauser V.W. Hughes O. Huot P. Indelicato P. Knowles F. Kottmann Y. W. Liu F. Mulhauser F. Nez C. Petitjean P. Rabinowitz J.M.F. dos Santos L.A. Schaller H. Schneuwly W. Schott L.M. Simons D. Taqqu F. Trehin J.F.C.A. Veloso 《Hyperfine Interactions》2000,127(1-4):161-166
The contribution of the root mean square (RMS) proton charge radius to the Lamb shift (2S–2P energy difference) in muonic
hydrogen (μp) amounts to 2%. Apart from the uncertainty on this charge radius, theory predicts the Lamb shift with a precision
on the ppm level. We are going to measure ΔE (2 S1/2(F=1)–2 P3/2(F=2)) in a laser resonance experiment to a precision of 30 ppm (i.e., 10% of the natural linewidth) and to deduce the RMS
proton charge radius with 10−3 relative accuracy, 20 times more precise than presently known.
The most important requirement for the feasibility of such an experiment, namely the availability of a sufficient amount of
long lived metastable μp atoms in the 2S state, has been investigated in a recent experiment at PSI. Our analysis shows that
in the order of one percent of all muons stopped in low pressure hydrogen gas form a long lived μp(2S) with a lifetime of
the order of 1 μs.
The technical realization of our experiment involves a new high intensity low energy muon beam, an efficient low energy muon
entrance detector, a randomly triggered 3 stage laser system providing the 0.5 mJ, 7 ns laser pulses at 6.02 μm wavelength,
and a combination of a xenon gas proportional scintillation chamber (GPSC) and a microstrip gas chamber (MSGC) with a CsI
coated surface to detect the 2 keV X rays from theμp(2P → 1S) transition.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
The method of nitriding of metals in an electron beam plasma is used to change the current density and energy of nitrogen
ions by varying the electron beam parameters (5–20 A, 60–500 eV). An electron beam is generated by an electron source based
on a self-heated hollow cathode discharge. Stainless steel 12Kh18N10T is saturated by nitrogen at 500°C for 1 h. The microhardness
is measured on transverse polished sections to obtain the dependences of the nitrided layer thickness on the ion current density
(1.6–6.2 mA/cm2), the ion energy (100–300 eV), and the nitrogen-argon mixture pressure (1–10 Pa). The layer thickness decreases by 4–5 μm
when the ion energy increases by 100 V and increases from 19 to 33 μm when the ion current density increases. The pressure
dependence of the layer thickness has a maximum. These results are in conflict with the conclusions of the theory of the limitation
of the layer thickness by ion sputtering, and the effective diffusion coefficient significantly exceeds the well-known reported
data. 相似文献
13.
T. Prokscha E. Morenzoni K. Deiters F. Foroughi D. George R. Kobler V. Vrankovic 《Hyperfine Interactions》2004,159(1-4):385-388
At the Paul Scherrer Institute (PSI, Villigen, Switzerland) a new high-intensity muon beam line with momentum p < 40 MeV/c is currently being commissioned. The beam line is especially designed to serve the needs of the low-energy, polarized
positive muon source (LE-μ+) and LE-μ SR spectrometer at PSI. The beam line replaces the existing μ E4 muon decay channel. A large acceptance is accomplished
by installing two solenoidal magnetic lenses close to the muon production target E that is hit by the 590-MeV PSI proton beam.
The muons are then transported by standard large aperture quadrupoles and bending magnets to the experiment. Several slit
systems and an electrostatic separator allow the control of beam shape, momentum spread, and to reduce the background due
to beam positrons or electrons. Particle intensities of up to 3.5 × 108 μ+/s and 107 μ−/s are expected at 28 MeV/c beam momentum and 1.8 mA proton beam current. This will translate into a LE-μ+ rate of 7,000/s being available at the LE-μ SR spectrometer, thus achieving μ+ fluxes, that are comparable to standard μ SR facilities. 相似文献
14.
M.C. Fujiwara J.M. Bailey G.A. Beer J.L. Beveridge J.L. Douglas T.M. Huber R. Jacot‐Guillarmod P. Kammel S.K. Kim P.E. Knowles A.R. Kunselman M. Maier V.E. Markushin G.M. Marshall C.J. Martoff G.R. Mason F. Mulhauser A. Olin C. Petitjean T.A. Porcelli J. Zmeskal 《Hyperfine Interactions》1997,106(1-4):257-264
The emission of muonic tritium atoms from a thin film of hydrogen isotopes into vacuum was observed. The time and position
of the muon decays were measured by tracking the decay electron trajectory. The observations are useful both for testing the
theoretical cross sections for muonic atomic interactions, and producing an atomic beam of slow μ-t with a controllable energy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
16.
F. Kottmann W. Amir F. Biraben C. A. N. Conde S. Dhawan T. W. Hänsch F. J. Hartmann V. W. Hughes O. Huot P. Indelicato L. Julien P. Knowles S. Kazamias Y.-W. Liu F. Mulhauser F. Nez R. Pohl P. Rabinowitz J. M. F. dos Santos L. A. Schaller H. Schneuwly W. Schott D. Taqqu J. F. C. A. Veloso 《Hyperfine Interactions》2001,138(1-4):55-60
A measurement of the 2S Lamb shift in muonic hydrogen (μ−p) is being prepared at the Paul Scherrer Institute (PSI). The goal of the experiment is to measure the energy difference
ΔE(25
P
3/2−23
S
1/2) by laser spectroscopy (λ≈6μm) to a precision of 30 ppm and to deduce the root mean square (rms) proton charge radius with
10−3 relative accuracy, 20 times more precise than presently known.
An important prerequisite to this experiment is the availability of long-lived μp2S
-atoms. A 2S-lifetime of ∼1 μs – sufficiently long to perform the laser experiment – at H2 gas pressures of 1–2 hPa was deduced from recent measurements of the collisional 2S-quenching rate. A new low-energy negative muon beam yields an order of magnitude more muon stops in a small low-density gas
volume than a conventional cloud muon beam. A stack of ultra-thin carbon foils is the key element of a fast detector for keV-muons.
The development of a 2 keV X-ray detector and a 3-stage laser system providing 0.5 mJ laser pulses at 6 μm is on the way.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
Pogorelsky I. V. Polyanskiy M. N. Babzien M. Yakimenko V. Dover N. P. Palmer C. A. J. Najmudin Z. Schreiber J. Shkolnikov P. Dudnikova G. 《Laser Physics》2011,21(7):1288-1294
A picosecond CO2 laser was used successfully in a number of experiments exploring advanced methods of particle acceleration [1]. Proton acceleration
from gas-jet plasma exemplifies another advantage of employing the increase in laser wavelength from the optical to the mid-IR
region. Recent theoretical- and experimental-studies of ion acceleration from laser-generated plasma point to better ways
to control the ion beam’s energy when plasma approaches the critical density. Studying this regime with solid-state lasers
is problematic due to the dearth of plasma sources at the critical electron density ∼1021 cm−3, corresponding to laser wavelength λ = 1 μm. CO2 laser offers a solution. The CO2 laser’s 10 μm wavelength shifts the critical plasma density to 1019 cm−3, a value attainable with gas jets. Capitalizing on this approach, we focused a circular polarized 1-TW CO2 laser beam onto a hydrogen gas jet and observed a monoenergetic proton beam in the 1–2 MeV range. Simultaneously, we optically
probed the laser/plasma interaction region with visible light, revealing holes bored by radiation pressure, as well as quasi-stationary
soliton-like plasma formations. Our findings from 2D PIC simulations agree with experimental results and aid in their interpretation. 相似文献
18.
V. T. Astrelin A. V. Burdakov V. S. Koidan K. I. Mekler P. I. Mel’nikov V. V. Postupaev M. A. Shcheglov 《Journal of Experimental and Theoretical Physics》1998,86(3):489-500
This paper presents the results of experiments on two-stage heating of a dense plasma by a relativistic electron beam in the
GOL-3 facility. A dense plasma with a length of about a meter and a hydrogen density up to 1017 cm−3 was created in the main plasma, whose density was 1015 cm−3. In the process of interacting with the plasma, the electron beam (1 MeV, 40 kA, 4 μs) imparts its energy to the electrons of the main plasma through collective effects. The heated electrons, as they disperse
along the magnetic field lines, in turn reach the region of dense plasma and impart their energy to it by pairwise collisions.
Estimates based on experimental data are given for the parameters of the flux of hot plasma electrons, the energy released
in the dense plasma, and the energy balance of the beam-plasma system. The paper discusses the dynamics of the plasma, which
is inhomogeneous in density and temperature, including the appearance of pressure waves.
Zh. éksp. Teor. Fiz. 113, 897–917 (March 1998) 相似文献
19.
B. A. Kalin N. V. Volkov E. A. Anan’eva 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(3):538-542
The results of investigating the wear resistance of E110 alloy samples irradiated by a He+ + Ar+ beam with a wide energy spectrum are presented. Surface modification under irradiation by an Ar+ beam at doses higher than 2 × 1018 ion/cm2 is shown to cause substantial enhancement of the wear resistance of samples because the structural homogeneity of near surface
layers increases, the surface roughness decreases, and its microhardness increases. The application of a mechanical-geometrical
wear model based on the experimental wear characteristics determined during accelerated tests indicates that the thinning
of an alloy cladding can reach rates of 10−6–10−3 mm/s, which agree satisfactorily with data obtained in other simulation experiments. The presence of an oxide film changes
a wear process characterized by an abrasive component. 相似文献
20.
P. Bricault 《The European physical journal. Special topics》2007,150(1):227-232
The ISAC facility at TRIUMF utilizes up to 100 μA from the 500 MeV H- cyclotron to produce the RIB using the Isotopic Separation On Line (ISOL) method. The ISAC-I facility comprised the RNB production
target stations, the mass separator and the beam delivery to low energy area and to a room temperature linear accelerator
composed of a 4-rod RFQ and an inter-digital H type structure Drift Tube LINAC. ISAC-I linear accelerator can provide beam
from A = 3 to 30 amu with an energy range from 0.15 to 1.5 A MeV.
Since the beginning of operations target development program has been to increase proton beam currents on targets. Now we
routinely operate our target at 50 to 85 μA and recently we have operated our target at 100 μA. Other developments are in
place to add other ion sources, laser, FEBIAD and ECRIS to the actual surface ion source. The last two five year plans were
mainly devoted to the construction of a heavy ion superconducting LINAC (ISAC-II), that will upgrade the mass and the energy
range from 30 to 150 and 1.5 to 6.5 A MeV, respectively.
We are now commissioning the medium β section and first experiment is scheduled for the fall 2006. 相似文献