Electron Energy Dependence of Amorphization in Zr3Fe

1993 ◽  
Vol 316 ◽  
Author(s):  
A.T. Motta ◽  
L.M. Howe ◽  
P.R. Okamoto
Keyword(s):  
Electron Energy ◽  
Cross Section ◽  
Sharp Increase ◽  
Low Dose ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
High Energies ◽  
Intermediate Energies ◽  
Low Energies ◽  
Order Of Magnitude

ABSTRACTThis paper reports the results from a study conducted to determine the effect of electron energy on the dose-to-amorphization of Zr3Fe at 23-30 K. Zr3Fe samples were irradiated in the HVEM at Argonne National Laboratory, at energies ranging from 200 to 900 keV. Amorphization occurred at electron energies from 900 keV down to 250 keV. Three distinct regions were observed: between 900 and 700 keV amorphization occurred at a constant low dose of ~ 4 × 1021 e cm-2; a higher plateau at 1022 was observed between 600 and 400 keV, and finally there was a sharp increase in the dose-to-amorphization below 400 keV, so that at 250 keV the necessary dose was an order of magnitude higher than that at 900 keV. In the region below 400 keV there was evidence of a dependence of the dose-to-amorphization on the orientation of the sample with respect to the electron beam. The results can be analyzed in terms of a composite displacement cross section dominated at high energies by displacements of Zr and Fe atoms, by displacements of Fe atoms at intermediate energies and of secondary displacements of lattice atoms by recoil impurities at low energies.

Temperature Dependence of Amorphization for Zirconolite and Perovskite Irradiated with 1 Mev Krypton Ions

1994 ◽  
Vol 353 ◽  
Author(s):  
T. J. White ◽  
R. C. Ewing ◽  
L. M. Wang ◽  
J. S. Forrester ◽  
C. Montross
Keyword(s):  
Cross Section ◽  
Heavy Ions ◽  
Arrhenius Plot ◽  
Ion Irradiation ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Large Cross Section ◽  
Magnéli Phases ◽  
Transmission Electron ◽  
Argon Ions

AbstractA transmission electron microscope investigation was made of zirconolites and perovskites irradiated to amorphization with 1 MeV krypton ions using the HVEM-Tandem Facility at Argonne National Laboratory. Three specimens were examined - a prototype zirconolite CaZrTi2O7, a gadolinium doped zirconolite Ca0.75Gd0.50Zr0.75Ti2O7and a uranium doped zirconolite Ca0.75U0.50Zr0.75Ti2O7. The critical amorphization dose Dc was determined at several temperatures between 20K to 675K. Dc was inversely proportional with temperature. For example, pure zirconolite requiring 10x the dose for amorphization at 475K compared with gadolinium zirconolite. Using an Arrhenius plot, the activation energy Ea for annealing in these compounds was found to be 0.129 eV and 0.067 eV respectively. The greater ease of amorphization for the gadolinium sample is probably a reflection of this element’s large cross section for interaction with heavy ions. Uranium zirconolite was very susceptible to damage and amorphised under 4 keV argon ions during the preparation of microscope specimens. In each sample, zirconolite coexisted with minor perovskite, reduced rutile (Magneli phases) and zirconia. These phases were more resistant to ion irradiation than zirconolite. Even for high gadolinium loadings, perovskite (Ca0.8Gd0.2TiO3) was 3-4 times more stable to ion irradiation than the surrounding zirconolite crystals.

Ion-Beam and Electron-Beam Induced Amorphization of Berlinite (AIPO4)

1994 ◽  
Vol 373 ◽  
Author(s):  
N. Bordes ◽  
R.C. Ewing
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Low Dose ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Crystalline Material ◽  
Small Areas ◽  
Transmission Electron

AbstractBerlinite (AIPO4) is isostructural with α-quartz. Like α-quartz, berlinite undergoes a pressure-induced amorphization at 15 ±3 GPa; however, upon release of the pressure, unlike α-quartz which remains amorphous, berlinite returns to the original crystalline structure of the single crystal. Berlinite was irradiated with 1.5 MeV Kr+ at temperatures ranging from 20 to 600K. The onset of amorphization was examined by monitoring the electron diffraction pattern by in situ transmission electron microscopy (TEM) at the HVEM-Tandem Facility at Argonne National Laboratory. The berlinite was easily amorphized at 20K at a relatively low dose of 4x1013 ions/cm2 or 0.05 dpa (displacements per atom). The critical amorphization dose increases with the sample temperature. These experiments also showed that the focused electron beam can locally amorphize the berlinite. After these irradiations, berlinite remained amorphous. At 500 °C, berlinite began to recrystallize: small areas of crystalline material appear in the aperiodic matrix. These results suggest that pressure-induced amorphization and ion-beam induced amorphization, in the case of berlinite, are different processes that result in two different aperiodic structural states.

Response of Zircon to Electron and Ne+ Irradiation

1997 ◽  
Vol 481 ◽  
Author(s):  
R. Devanathan ◽  
W. J. Weber ◽  
L. A. Boatner
Keyword(s):  
Nuclear Waste ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Voltage Electron ◽  
Waste Forms ◽  
High Voltage Electron Microscope ◽  
Ion Accelerator ◽  
Order Of Magnitude ◽  
Nuclear Waste Forms

ABSTRACTZircon (ZrSiO4) is an actinide host phase in vitreous ceramic nuclear waste forms and a potential host phase for the disposition of excess weapons plutonium. In the present work, the effects of 800 and 900 keV electron, and 1 MeV Ne+ irradiations on the structure of single crystals of ZrSiO4 have been investigated. The microstructural evolution during the irradiations was studied in situ using a high-voltage electron microscope interfaced to an ion accelerator at Argonne National Laboratory. The results indicate that electron irradiation at 15 K cannot amorphize ZrSiO4 even at fluences an order of magnitude higher than that required for amorphization by 1.5 MeV Kr + ions. However, the material is readily amorphized by I MeV Ne+ irradiation at 15 K. The temperature dependence of this amorphization is discussed in light of previous studies of radiation Zdamage in ZrSiO4.

Cation transport in gaseous nitrogen: density and temperature effects

1986 ◽  
Vol 64 (4) ◽  
pp. 777-779 ◽  
Author(s):  
Toshinori Wada ◽  
Norman Gee ◽  
Gordon R. Freeman
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Temperature Effects ◽  
Cation Transport ◽  
Polarization Potential ◽  
Gaseous Nitrogen ◽  
Nitrogen Gas ◽  
High Energies ◽  
Low Energies ◽  
Body Potential

The density-normalized mobility of nμ of cations in nitrogen gas at densities up to nc = 6.7 × 1027 molecules/m3 increases with temperature. At n ≤ 5.7 × 1025 molecules/m3 and T > 250 K, the dominating ion is N4+. At lower temperatures and higher densities, relatively loosely bound clusters N4+(N2), N4+(N2)2, … form. Momentum transfer cross sections for N4+–N2 are governed at low energies by the polarization potential, and at high energies by the hard body potential. The cross section for N2+–N2 at high energies is larger than that for N4+–N2.

Hadronic Electrons?

1975 ◽  
Vol 28 (5) ◽  
pp. 479 ◽  
Author(s):  
Stephen Wolfram
Keyword(s):  
High Energy ◽  
Strong Interactions ◽  
High Energy Electron ◽  
High Energies ◽  
Meson Cloud ◽  
Low Energies ◽  
Order Of Magnitude ◽  
Neutral Vector ◽  
Evaporation Region ◽  
The One

A new form of high energy electron-hadron coupling is examined with reference to the experimental data. The electron is taken to have a neutral vector gluon cloud with a radius ~ 10-18 m. This is shown to be consistent with measurements on e+e- -+ e+e- and 9.-2. At low energies, only photons couple to the gluons, but at higher energies 'evaporation' then 'boiling' of OJ and �J occurs, allowing strong interactions. The model yields accurate predictions for the form of the rise in R = u(e+e--+h)/u(e+e--+p.+p.-). Arguments are given for the order of magnitude of m. and for the lack of a permanent meson cloud in leptons. Strong interaction selection rules forbid a contribution to nO -+ e+e-, and interference with the one-photon channel produces minimal scaling violation in eN processes at present energies. The constant value of u(e+e-)/u(pp) is correctly predicted and evidence from high energy pp interactions is also cited. The'll particles are interpreted as e+eresonances in the evaporation region, and their properties are generated correctly. Predictions are given for the behaviour of u(e�e-) at high energies.

CHAOTIC AND HYPERCHAOTIC MOTION OF A CHARGED PARTICLE IN A MAGNETIC DIPOLE FIELD

2000 ◽  
Vol 10 (01) ◽  
pp. 265-271 ◽  
Author(s):  
O. F. DE ALCANTARA BONFIM ◽  
DAVID J. GRIFFITHS ◽  
SASHA HINKLEY
Keyword(s):  
Charged Particle ◽  
Magnetic Dipole ◽  
Equatorial Plane ◽  
Magnetic Dipole Moment ◽  
Equations Of Motion ◽  
Variable Speed ◽  
High Energies ◽  
Intermediate Energies ◽  
Low Energies ◽  
Magnetic Dipole Field

The motion of a charged particle in the field of a magnetic dipole is studied by numerically integrating the equations of motion. The widely believed picture in which a bound particle corkscrews about a line of magnetic flux, bouncing back along the same line as it nears the poles, is shown to be a substantial over-simplification. The nature of the trajectory depends on the energy of the particle, but whatever the energy this picture is not observed. For low energies the particle will corkscrew towards the poles, while at the same time drifting laterally with a variable speed in a quasiperiodic fashion. For intermediate energies the motion is found to be chaotic, and for higher energies it becomes hyperchaotic. In the equatorial plane only quasiperiodic orbits can occur. If the magnetic dipole moment is slowly varying, the particle undergoes chaotic motion even in the equatorial plane, but only for high energies.

scholarly journals On the stopping of fast particles and on the creation of positive electrons

1934 ◽  
Vol 146 (856) ◽  
pp. 83-112 ◽  
Keyword(s):  
Quantum Mechanics ◽  
Cross Section ◽  
Nuclear Charge ◽  
Primary Energy ◽  
Stopping Power ◽  
Nuclear Scattering ◽  
The Third ◽  
High Energies ◽  
Order Of Magnitude ◽  
Very High

The stopping power of matter for fast particles is at present believed to be due to three different processes: (1) the ionization; (2) the nuclear scattering; (3) the emission of radiation under the influence of the electric field of a nucleus. The first two processes have been treated in quantum mechanics by Bethe, Møller, and Bloch in a very satisfactory way. A provisional estimation of the order of magnitude to be expected in the third process has been given by Heitler. The result obtained was that the cross-section ϕ for the energy loss by radiation for very fast particles (if the primary energy E 0 ≫ mc 2 ) is of the order ϕ ∽ Z 2 /137 ( e 2 / mc 2 ) 2 , (1) Where Z is the nuclear charge. It is the aim of the present paper to discuss in greater detain the rate of loss of energy by this third process and its dependence on the primary energy; in particular we shall consider the effect of screening . The results obtained for very high energies (> 137 mc 2 ) seem to be in disagreement with experiments made by Anderson ( cf . 7).

scholarly journals Odderon and pomeron as fractal dimension in pp and p̄p total cross-sections

2016 ◽  
Vol 31 (10) ◽  
pp. 1650066 ◽  
Author(s):  
F. S. Borcsik ◽  
S. D. Campos
Keyword(s):  
Fractal Dimension ◽  
Total Cross Section ◽  
Cross Section ◽  
Cross Sections ◽  
Fractal Dimensions ◽  
Total Cross Sections ◽  
High Energies ◽  
Fitting Procedure ◽  
Low Energies ◽  
Section Structure

In this paper, one presents a naive parametrization to [Formula: see text] and [Formula: see text] total cross-sections. The main goal of this parametrization is to study the possible fractal structure present in the total cross-section. The result of the fitting procedure shows two different fractal dimensions: a negative (low-energies) and a positive (high-energies). The negative fractal dimension represents the emptiness of the total cross-section structure and the positive represents the filling up process with the energy increase. Hence, the total cross-section presents a multifractal behavior. At low-energies, the odderon exchange may be associated with the negative fractal dimension and at high-energies, the pomeron may be associated with the positive fractal dimension. Therefore, the exchange of odderons and pomerons may be viewed as a transition from a less well-defined to a more well-defined internal structure, depending on the energy.

Cross-Section TEM Study On Kr+ Irradiation-Induced Amorphization in Quartz

1997 ◽  
Vol 3 (S2) ◽  
pp. 771-772
Author(s):  
W.L. Gong ◽  
L.M. Wang ◽  
R.C. Ewing
Keyword(s):  
Cross Section ◽  
Room Temperature ◽  
Chemical Nature ◽  
Semiconductor Industry ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Nuclear Industry ◽  
Transmission Electron ◽  
Polished Side ◽  
Diamond Paste

Radiation damage in quartz has been of interest to the semiconductor industry, optical fiber industry, and nuclear industry. Cross-section transmission electron microscopy (TEM) is a powerful tool for investigating the irradiation effects since it provides a direct measurement of the ion and the damage distributions, and can also provide detailed microstructural information such as the presence of amorphous regions and the size, density and chemical nature of defect aggregates. The results reported below are from a systematic cross-section TEM study on 1.5 MeV Kr+ ion irradiated quartz.3-mm discs of quartz (along 010 face) were prepared with 100 μm in thickness. One side for each discs was well polished using a 0.05 μm diamond paste. The well-polished side was irradiated at room temperature with 1.5 MeV Kr ions in the HVEM-Tandem Facility at Argonne National Laboratory. Following irradiation, cross-section TEM specimens were prepared using the so-called T-tool technique, a modified tripot technique

Development of the Positron Facility at the Argonne National Laboratory’s 20 MeV Linac

2008 ◽  
Vol 607 ◽  
pp. 243-247 ◽  
Author(s):  
S. Chemerisov ◽  
Charles D. Jonah
Keyword(s):  
Penning Trap ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Positron Energy ◽  
Slow Positron ◽  
Order Of Magnitude ◽  
Low Energy Electron ◽  
Further Development ◽  
Positron Production ◽  
Incident Positron

We present an update on positron-facility development at Argonne National Laboratory. We will discuss advantages of using low energy electron accelerator, present our latest results on slow positron production simulations, and plans for further development of the facility. We have installed a new converter/moderator assembly that is appropriate for our electron energy and that allows increasing the yield about an order of magnitude. We have obtained a Penning trap and buncher from LLNL that we plan to install. We have simulated the relative yields of thermalized positrons as a function of incident positron energy on the moderator. We use these data to calculate positron yields that we compare with our experimental data as well as with available literature data. We will discuss the new design of the next generation positron front end utilizing reflection moderation geometry.

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