34 research outputs found
An advection-diffusion model for cross-field runaway electron transport in perturbed magnetic fields
Disruption-generated runaway electrons (RE) present an outstanding issue for
ITER. The predictive computational studies of RE generation rely on
orbit-averaged computations and, as such, they lack the effects from the
magnetic field stochasticity. Since stochasiticity is naturally present in
post-disruption plasma, and externally induced stochastization offers a
prominent mechanism to mitigate RE avalanche, we present an advection-diffusion
model that can be used to couple an orbit-following code to an orbit-averaged
tool in order to capture the cross-field transport and to overcome the latter's
limitation. The transport coefficients are evaluated via a Monte Carlo method.
We show that the diffusion coefficient differs significantly from the
well-known Rechester-Rosenbluth result. We also demonstrate the importance of
including the advection: it has a two-fold role both in modelling transport
barriers created by magnetic islands and in amplifying losses in regions where
the islands are not present
ASCOT: solving the kinetic equation of minority particle species in tokamak plasmas
A comprehensive description of methods, suitable for solving the kinetic
equation for fast ions and impurity species in tokamak plasmas using Monte
Carlo approach, is presented. The described methods include Hamiltonian
orbit-following in particle and guiding center phase space, test particle or
guiding center solution of the kinetic equation applying stochastic
differential equations in the presence of Coulomb collisions, neoclassical
tearing modes and Alfv\'en eigenmodes as electromagnetic perturbations relevant
to fast ions, together with plasma flow and atomic reactions relevant to
impurity studies. Applying the methods, a complete reimplementation of the
well-established minority species code ASCOT is carried out as a response both
to the increase in computing power during the last twenty years and to the
weakly structured growth of the code, which has made implementation of
additional models impractical. Also, a benchmark between the previous code and
the reimplementation is accomplished, showing good agreement between the codes.Comment: 13 pages, 9 figures, submitted to Computer Physics Communication
Calculating the 3D magnetic field of ITER for European TBM studies
The magnetic perturbation due to the ferromagnetic test blanket modules
(TBMs) may deteriorate fast ion confinement in ITER. This effect must be
quantified by numerical studies in 3D. We have implemented a combined finite
element method (FEM) -- Biot-Savart law integrator method (BSLIM) to calculate
the ITER 3D magnetic field and vector potential in detail. Unavoidable geometry
simplifications changed the mass of the TBMs and ferritic inserts (FIs) up to
26%. This has been compensated for by modifying the nonlinear ferromagnetic
material properties accordingly. Despite the simplifications, the computation
geometry and the calculated fields are highly detailed. The combination of
careful FEM mesh design and using BSLIM enables the use of the fields
unsmoothed for particle orbit-following simulations. The magnetic field was
found to agree with earlier calculations and revealed finer details. The vector
potential is intended to serve as input for plasma shielding calculations.Comment: In proceedings of the 28th Symposium on Fusion Technolog
Carcinogenicity of cobalt, antimony compounds, and weapons-grade tungsten alloy
The complete evaluation of the carcinogenicity of cobalt, antimony compounds, and weapons-grade tungsten alloy will be published in Volume 131 of the IARC Monographs.[Excerpt] In March, 2022, a Working Group of 31 scientists from 13 countries met remotely at the invitation of the International Agency for Research on Cancer (IARC) to finalise their evaluation of the carcinogenicity of nine agents: cobalt metal (without tungsten carbide or other metal alloys), soluble cobalt(II) salts, cobalt(II) oxide, cobalt(II,III) oxide, cobalt(II) sulfide, other cobalt(II) compounds, trivalent antimony, pentavalent antimony, and weapons-grade tungsten (with nickel and cobalt) alloy. For cobalt metal and the cobalt compounds, particles of all sizes were included in the evaluation. These assessments will be published in Volume 131 of the IARC Monographs.1
Cobalt metal and soluble cobalt(II) salts were classified as âprobably carcinogenic to humansâ (Group 2A) based on âsufficientâ evidence for cancer in experimental animals and âstrongâ mechanistic evidence in human primary cells. Cobalt(II) oxide and weapons-grade tungsten alloy were classified as âpossibly carcinogenic to humansâ (Group 2B) based on âsufficientâ evidence in experimental animals. Trivalent antimony was classified as âprobably carcinogenic to humansâ (Group 2A), based on âlimitedâ evidence for cancer in humans, âsufficientâ evidence for cancer in experimental animals, and âstrongâ mechanistic evidence in human primary cells and in experimental systems. Cobalt(II,III) oxide, cobalt(II) sulfide, other cobalt(II) compounds, and pentavalent antimony were each evaluated as ânot classifiable as to its carcinogenicity to humansâ (Group 3).[...
European code against cancer 4th edition: 12 ways to reduce your cancer risk
This overview describes the principles of the 4th edition of the European Code against Cancer and provides an introduction to the 12 recommendations to reduce cancer risk. Among the 504.6 million inhabitants of the member states of the European Union (EU28), there are annually 2.64 million new cancer cases and 1.28 million deaths from cancer. It is estimated that this cancer burden could be reduced by up to one half if scientific knowledge on causes of cancer could be translated into successful prevention. The Code is a preventive tool aimed to reduce the cancer burden by informing people how to avoid or reduce carcinogenic exposures, adopt behaviours to reduce the cancer risk, or to participate in organised intervention programmes. The Code should also form a base to guide national health policies in cancer prevention. The 12 recommendations are: not smoking or using other tobacco products; avoiding second-hand smoke; being a healthy body weight; encouraging physical activity; having a healthy diet; limiting alcohol consumption, with not drinking alcohol being better for cancer prevention; avoiding too much exposure to ultraviolet radiation; avoiding cancer-causing agents at the workplace; reducing exposure to high levels of radon; encouraging breastfeeding; limiting the use of hormone replacement therapy; participating in organised vaccination programmes against hepatitis B for newborns and human papillomavirus for girls; and participating in organised screening programmes for bowel cancer, breast cancer, and cervical cancer
European Code against Cancer, 4th Edition: Cancer screening
In order to update the previous version of the European Code against Cancer and formulate evidence-based recommendations, a systematic search of the literature was performed according to the methodology agreed by the Code Working Groups. Based on the review, the 4th edition of the European Code against Cancer recommends: âTake part in organized cancer screening programmes for: âą Bowel cancer (men and women)âą Breast cancer (women)âą Cervical cancer (women).âOrganized screening programs are preferable because they provide better conditions to ensure that the Guidelines for Quality Assurance in Screening are followed in order to achieve the greatest benefit with the least harm. Screening is recommended only for those cancers where a demonstrated life-saving effect substantially outweighs the potential harm of examining very large numbers of people who may otherwise never have, or suffer from, these cancers, and when an adequate quality of the screening is achieved. EU citizens are recommended to participate in cancer screening each time an invitation from the national or regional screening program is received and after having read the information materials provided and carefully considered the potential benefits and harms of screening. Screening programs in the European Union vary with respect to the age groups invited and to the interval between invitations, depending on each country's cancer burden, local resources, and the type of screening test used For colorectal cancer, most programs in the EU invite men and women starting at the age of 50â60 years, and from then on every 2 years if the screening test is the guaiac-based fecal occult blood test or fecal immunochemical test, or every 10 years or more if the screening test is flexible sigmoidoscopy or total colonoscopy. Most programs continue sending invitations to screening up to the age of 70â75 years. For breast cancer, most programs in the EU invite women starting at the age of 50 years, and not before the age of 40 years, and from then on every 2 years until the age of 70â75 years. For cervical cancer, if cytology (Pap) testing is used for screening, most programs in the EU invite women starting at the age of 25â30 years and from then on every 3 or 5 years. If human papillomavirus testing is used for screening, most women are invited starting at the age of 35 years (usually not before age 30 years) and from then on every 5 years or more. Irrespective of the test used, women continue participating in screening until the age of 60 or 65 years, and continue beyond this age unless the most recent test results are normal
Monte Carlo method and High Performance Computing for solving FokkerâPlanck equation of minority plasma particles
This paper explains how to obtain the distribution function of minority ions in tokamak plasmas using the Monte Carlo method. Since the emphasis is on energetic ions, the guiding-center transformation is outlined, including also the transformation of the collision operator. Even within the guiding-center formalism, the fast particle simulations can still be very CPU intensive and, therefore, we introduce the reader also to the world of high-performance computing. The paper is concluded with a few examples where the presented method has been applied