scholarly journals Validating modeling assumptions of alpha particles in electrostatic turbulence

2015 ◽  
Vol 81 (3) ◽  
Author(s):  
G. J. Wilkie ◽  
I. G. Abel ◽  
E. G. Highcock ◽  
W. Dorland
Keyword(s):  
Particle Flux ◽  
Magnitude Estimate ◽  
High Energy ◽  
Alpha Particles ◽  
Fusion Plasmas ◽  
Usual Practice ◽  
Slowing Down ◽  
Fast Ions ◽  
Low Concentrations ◽  
Order Of Magnitude

To rigorously model fast ions in fusion plasmas, a non-Maxwellian equilibrium distribution must be used. In this work, the response of high-energy alpha particles to electrostatic turbulence has been analyzed for several different tokamak parameters. Our results are consistent with known scalings and experimental evidence that alpha particles are generally well confined: on the order of several seconds. It is also confirmed that the effect of alphas on the turbulence is negligible at realistically low concentrations, consistent with linear theory. It is demonstrated that the usual practice of using a high-temperature Maxwellian, while previously shown to give an adequate order-of-magnitude estimate of the diffusion coefficient, gives incorrect estimates for the radial alpha particle flux, and a method of correcting it in general is provided. Furthermore, we see that the timescales associated with collisions and transport compete at moderate energies, calling into question the assumption that alpha particles remain confined to a flux surface that is used in the derivation of the slowing-down distribution.

scholarly journals Simulating the impact of charge exchange on beam ions in MAST-U

2022 ◽  
Author(s):  
Patrik Ollus ◽  
Robert James Akers ◽  
Bethany Colling ◽  
Hana El-Haroun ◽  
David Keeling ◽  
...  
Keyword(s):  
Charge Exchange ◽  
Plasma Heating ◽  
Current Drive ◽  
Beam Power ◽  
Fusion Plasmas ◽  
Vacuum Vessel ◽  
Noticeable Increase ◽  
Slowing Down ◽  
Fast Ions ◽  
The Impact

Abstract A model for simulating charge exchange (CX) of fast ions with background atoms in magnetically confined fusion plasmas has been implemented in the ASCOT orbit-following code. The model was verified by comparing simulated reaction mean free paths to analytical values across a range of fusion-relevant parameters. ASCOT was used to simulate beam ions slowing down in the presence of CX reactions in a MAST-U target scenario. ASCOT predicts the CX-induced loss of beam power to be 22%, which agrees to within 15% with the TRANSP prediction. Because of CX, plasma heating and current drive by beam ions are strongly reduced towards the edge. However, an overall lower but noticeable increase of up to 20% in current drive is predicted closer to the core. The simulated deposition of fast CX atoms on the wall is concentrated around the outer midplane, with estimated peak power loads of 70–80 kWm-2 on the central poloidal field coils (P5) and the vacuum vessel wall between them. This analysis demonstrates that ASCOT can be used to simulate fast ions in fusion plasmas where CX reactions play a significant role, e.g., in spherical tokamaks and stellarators.

In situ irradiation effects studies in medium- and high-voltage TEM

1995 ◽  
Vol 53 ◽  
pp. 234-235
Author(s):  
Charles W. Allen
Keyword(s):  
Cross Section ◽  
Particle Flux ◽  
Threshold Value ◽  
High Energy ◽  
Irradiation Damage ◽  
Defect Complexes ◽  
Lattice Position ◽  
Electrons And Ions ◽  
The Masses

With respect to structural consequences within a material, energetic electrons, above a threshold value of energy characteristic of a particular material, produce vacancy-interstial pairs (Frenkel pairs) by displacement of individual atoms, as illustrated for several materials in Table 1. Ion projectiles produce cascades of Frenkel pairs. Such displacement cascades result from high energy primary knock-on atoms which produce many secondary defects. These defects rearrange to form a variety of defect complexes on the time scale of tens of picoseconds following the primary displacement. A convenient measure of the extent of irradiation damage, both for electrons and ions, is the number of displacements per atom (dpa). 1 dpa means, on average, each atom in the irradiated region of material has been displaced once from its original lattice position. Displacement rate (dpa/s) is proportional to particle flux (cm-2s-1), the proportionality factor being the “displacement cross-section” σD (cm2). The cross-section σD depends mainly on the masses of target and projectile and on the kinetic energy of the projectile particle.

scholarly journals PROMPT BETA SPECTROSCOPY AS A DIAGNOSTIC FOR MIX IN IGNITED NIF CAPSULES

2006 ◽  
Vol 21 (13) ◽  
pp. 1029-1040 ◽  
Author(s):  
A. C. HAYES ◽  
GERARD JUNGMAN ◽  
J. C. SOLEM ◽  
P. A. BRADLEY ◽  
R. S. RUNDBERG
Keyword(s):  
Laser Beam ◽  
Beam Energy ◽  
High Energy ◽  
Shell Material ◽  
National Ignition Facility ◽  
Confinement Fusion ◽  
Order Of Magnitude ◽  
Beta Spectroscopy ◽  
Fundamental Physical ◽  
Beta Emission

The National Ignition Facility (NIF) technology is designed to drive deuterium–tritium (DT) internal confinement fusion (ICF) targets to ignition using indirect radiation from laser beam energy captured in a hohlraum. Hydrodynamical instabilities at interfaces in the ICF capsule leading to mix between the DT fuel and the ablator shell material are of fundamental physical interest and can affect the performance characteristics of the capsule. Here we describe new radiochemical diagnostics for mix processes in ICF capsules with plastic or Be (0.9% Cu ) ablator shells. Reactions of high-energy tritons with shell material produce high-energy β-emitters. We show that mix between the DT fuel and the shell material enhances high-energy prompt beta emission from these reactions by more than an order of magnitude over that expected in the absence of mix. We further show how a mix signal could be detectable in an ignition failure regime corresponding to yields greater than about 2 kJ.

Processing and Excellent Oxidation Resistance of Nanocrystalline Fe-Cr Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 1122-1125
Author(s):  
Rajeev K. Gupta ◽  
B.V. Mahesh ◽  
R.K. Singh Raman ◽  
Carl C. Koch
Keyword(s):  
Oxidation Resistance ◽  
Secondary Ion Mass Spectrometry ◽  
Nanocrystalline Alloy ◽  
High Energy ◽  
Processing Route ◽  
Protective Oxide ◽  
Time Intervals ◽  
Regular Time ◽  
Order Of Magnitude ◽  
Energy Ball

Nanocrystalline and microcrystalline Fe-10Cr alloys were prepared by high energy ball milling followed by compaction and sintering, and then oxidized in air for 52 hours at 400°C. The oxidation resistance of nanocrystalline Fe-10Cr alloy as determined by measuring the weight gain after regular time intervals was compared with that of the microcrystalline alloy of same chemical composition (also prepared by the same processing route and oxidized under identical conditions). Oxidation resistance of nanocrystalline Fe10Cr alloy was found to be in excess of an order of magnitude superior than that of microcrystalline Fe10Cr alloy. The paper also presents results of secondary ion mass spectrometry of oxidized samples of nanocrystalline and microcrystalline Fe-Cr alloys, evidencing the formation of a more protective oxide scale in the nanocrystalline alloy.

Pseudo Dry Gas Technology: Pathway to Decarbonisation of Energy Consumption for Remote Offshore Gas Fields

2021 ◽  
Author(s):  
Tran Nguyet Ngo ◽  
Lee Thomas ◽  
Kavitha Raghavendra ◽  
Terry Wood
Keyword(s):  
Energy Consumption ◽  
Energy Transition ◽  
High Energy ◽  
Innovative Technology ◽  
Flow Loop ◽  
Gas Field ◽  
Power Requirement ◽  
Order Of Magnitude ◽  
Gas Fields ◽  
Technology Pathway

Abstract Transporting large volumes of gas over long distances from further and deeper waters remains a significant challenge in making remote offshore gas field developments technologically and economically viable. The conventional development options include subsea compression, floating topside with topside compression and pipeline tie-back to shore, or floating liquefied natural gas vessels. However, these options are CAPEX and OPEX intensive and require high energy consumption. Demand for a lower emission solution is increasingly seen as the growing trend of global energy transition. Pseudo Dry Gas (PDG) technology is being developed by Intecsea, Worley Group and The Oil & Gas Technology Centre (Aberdeen) and tested in collaboration with Cranfield University. This is applied to develop stranded or remote gas reserves by removing fluids at the earliest point of accumulation at multiple locations, resulting in near dry gas performance. This technology aims to solve liquid management issues and subsequently allows for energy efficient transportation of the subsea gas enabling dramatic reductions in emissions. The PDG prototype tested using the Flow Loop facilities at Cranfield University has demonstrated the concept’s feasibility. Due to a greater amount of gas recovered with a much lower power requirement, the CO2 emissions per ton of gas produced via the PDG concept is by an order of magnitude lower than conventional methods. This study showed a reduction of 65% to 80% against standard and alternative near future development options. The paper considers innovative technology and a value proposition for the Pseudo Dry Gas concept based on a benchmarked study of a remote offshore gas field. The basin was located in 2000m of water depth, with a 200km long subsea tie-back. To date the longest tieback studied was 350km. It focused on energy consumption and carbon emission aspects. The conclusion is that decarbonisation of energy consumption is technically possible and can be deployed subsea to help meet this future challenge and push the envelope of subsea gas tie-backs.

Damage in High Energy Light Ions Irradiated Silicon Carbide

1998 ◽  
Vol 510 ◽  
Author(s):  
P. Leveque ◽  
S. Godey ◽  
P.O. Renault ◽  
E. Ntsoenzok ◽  
J.F. Barbot
Keyword(s):  
Silicon Carbide ◽  
Surface Layer ◽  
Energy Transfer ◽  
High Energy ◽  
Alpha Particles ◽  
Defect Production ◽  
Majority Carrier ◽  
Reflectivity Spectra ◽  
Light Ions ◽  
Compensation Layer

AbstractCommercial n-type 4H-SiC wafers were implanted with doses of MeV alpha particles, high enough to cause majority carrier modification. Analysis of infrared reflectivity spectra shows that the implanted crystals can be divided into three layers: a surface layer of about 30 nm followed by a compensation layer where the energy transfer of the incident particles is low and an overdoping layer in the region of maximum defect production, i.e. near the theoretical mean range of ions Rp

High-energy X-ray diffuse scattering

2009 ◽  
Vol 42 (3) ◽  
pp. 392-400 ◽  
Author(s):  
I. B. Ramsteiner ◽  
A. Schöps ◽  
H. Reichert ◽  
H. Dosch ◽  
V. Honkimäki ◽  
...  
Keyword(s):  
Multiple Scattering ◽  
Diffuse Scattering ◽  
Binary Systems ◽  
High Energy ◽  
Absorption Length ◽  
Time Resolved ◽  
X Ray ◽  
Order Of Magnitude ◽  
Extinction Length ◽  
Scattering Volume

Diffuse X-ray scattering has been an important tool for understanding the atomic structure of binary systems for more than 50 years. The majority of studies have used laboratory-based sources providing 8 keV photons or synchrotron radiation with similar energies. Diffuse scattering is weak, with the scattering volume determined by the X-ray absorption length. In the case of 8 keV photons, this is not significantly different from the typical extinction length for Bragg scattering. If, however, one goes to energies of the order of 100 keV the scattering volume for the diffuse scattering increases up to three orders of magnitude while the extinction length increases by only one order of magnitude. This leads to a gain of two orders of magnitude in the relative intensity of the diffuse scattering compared with the Bragg peaks. This gain, combined with the possibility of recording the intensity from an entire plane in reciprocal space using a two-dimensional X-ray detector, permits time-resolved diffuse scattering studies in many systems. On the other hand, diffraction features that are usually neglected, such as multiple scattering, come into play. Four types of multiple scattering phenomena are discussed, and the manner in which they appear in high-energy diffraction experiments is considered.

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