31 research outputs found
Fringe field simulations of a non-scaling FFAG accelerator
Fixed-field Alternating Gradient (FFAG) accelerators offer the potential of
high-quality, moderate energy ion beams at low cost. Modeling of these
structures is challenging with conventional beam tracking codes because of the
large radial excursions of the beam and the significance of fringe field
effects. Numerous tune resonances are crossed during the acceleration, which
would lead to beam instability and loss in a storage ring. In a non-scaling
FFAG, the hope is that these resonances can be crossed sufficiently rapidly to
prevent beam loss. Simulations are required to see if this is indeed the case.
Here we simulate a non-scaling FFAG which accelerates protons from 31 to 250
MeV. We assume only that the bending magnets have mid-plane symmetry, with
specified vertical bending field in the mid-plane (y=0). The magnetic field can
be obtained everywhere using a power series expansion, and we develop
mathematical tools for calculating this expansion to arbitrary order when the
longitudinal field profile is given by an Enge function. We compare the use of
a conventional hard-edge fringe with a more accurate, soft-edge fringe field
model. The tune 1/3 resonance is the strongest, and crossing it in the
hard-edge fringe model results in a 21% loss of the beam. Using the soft-edge
fringe model the beam loss is less than 6%.Comment: 12 pages; 12 figure
Study of the Anatomy of the Alimentary Canal of Brochymena quadripustulata (Hemiptera:Pentatomidae)
An anatomical study of the alimentary canal and associated salivary apparatus was conducted for the pentatomid, Brochymena quadripustulata. The esophagus, ventriculus, pylorus, rectum, principal salivary glands and ducts are described and illustrated. Described structures of Brochymena quadripustulata are compared with various species of pentatomids and other hemipterans
Accurate and efficient spin integration for particle accelerators
Accurate spin tracking is a valuable tool for understanding spin dynamics in
particle accelerators and can help improve the performance of an accelerator.
In this paper, we present a detailed discussion of the integrators in the spin
tracking code gpuSpinTrack. We have implemented orbital integrators based on
drift-kick, bend-kick, and matrix-kick splits. On top of the orbital
integrators, we have implemented various integrators for the spin motion. These
integrators use quaternions and Romberg quadratures to accelerate both the
computation and the convergence of spin rotations. We evaluate their
performance and accuracy in quantitative detail for individual elements as well
as for the entire RHIC lattice. We exploit the inherently data-parallel nature
of spin tracking to accelerate our algorithms on graphics processing units.Comment: 43 pages, 17 figure
Propagation of a Gaussian Wigner Function Through a Matrix-Aperture Beamline
A Gaussian Wigner function may be defined in terms of its covariance matrix
and centroid. In the framework of statistical optics, a Wigner function
represents partially coherent radiation. A Gaussian Wigner function is an
equivalent representation to the more commonly used Gaussian Schell model cross
spectral density. Starting from the relationship between Gaussian Wigner
functions and the Gaussian Schell model, we derive coherence properties of the
Gaussian Wigner function including coherence length and degree of coherence. We
define a simplified beamline called a matrix-aperture beamline composed of
linear transport sections separated by physical apertures. This is an idealized
form for a transport beamline in a synchrotron light source or X-ray free
electron laser. An envelope model provides a basic foundation to understand the
optics of a given beamline in an analogous manner with which linear optics are
treated in particle beam dynamics, with corresponding definitions of emittance
and Twiss parameters. One major challenge to such an envelope model lies in the
hard edge apertures which break the Gaussian condition raising the question as
to the adequacy of a Gaussian model. We present a consistent way to construct a
Gaussian approximation of the far-field Wigner function following the hard edge
aperture. To this end, we introduce the concept of a Gaussian aperture and
analyze its effects on the radiation Wigner function. A software implementation
of this model is described
Optimization of Magnetized Electron Cooling with JSPEC
The Electron-Ion-Collider (EIC) will be a next-generation facility located at
Brookhaven National Laboratory (BNL), built with the goal of accelerating heavy
ions up to 275 GeV. To prevent ion beam size growth during the acceleration
phase, cooling techniques will be required to keep the beam size from growing
due to intra-beam scattering. The JSPEC (JLab Simulation Package for Electron
Cooling) package is a tool designed to numerically model
magnetized and unmagnetized cooling through friction forces between
co-propagating electron and ion bunches.
Here we describe a feature that has been added to the JSPEC package, which
implements a Nelder-Mead Simplex optimization algorithm to allow a user to
optimize certain beam parameters in order to achieve a target cooling time
Genetic effects on gene expression across human tissues
Characterization of the molecular function of the human genome and its variation across individuals is essential for identifying the cellular mechanisms that underlie human genetic traits and diseases. The Genotype-Tissue Expression (GTEx) project aims to characterize variation in gene expression levels across individuals and diverse tissues of the human body, many of which are not easily accessible. Here we describe genetic effects on gene expression levels across 44 human tissues. We find that local genetic variation affects gene expression levels for the majority of genes, and we further identify inter-chromosomal genetic effects for 93 genes and 112 loci. On the basis of the identified genetic effects, we characterize patterns of tissue specificity, compare local and distal effects, and evaluate the functional properties of the genetic effects. We also demonstrate that multi-tissue, multi-individual data can be used to identify genes and pathways affected by human disease-associated variation, enabling a mechanistic interpretation of gene regulation and the genetic basis of diseas
Proof-of-Principle Experiment for FEL-Based Coherent Electron Cooling,”
Abstract Coherent electron cooling (CEC) has a potential to significantly boost luminosity of high-energy, highintensity hadron-hadron and electron-hadron colliders. In a CEC system, a hadron beam interacts with a cooling electron beam. A perturbation of the electron density caused by ions is amplified and fed back to the ions to reduce the energy spread and the emittance of the ion beam. To demonstrate the feasibility of CEC we propose a proof-of-principle experiment at RHIC using SRF linac. In this paper, we describe the setup for CeC installed into one of RHIC's interaction regions. We present results of analytical estimates and results of initial simulations of cooling a gold-ion beam at 40 GeV/u energy via CeC
Loss of Mitogen-Activated Protein Kinase Kinase Kinase 4 (MAP3K4) Reveals a Requirement for MAPK Signalling in Mouse Sex Determination
The boygirl (byg) mouse mutant reveals that MAP3K4-mediated signaling is necessary for normal SRY expression and testis specification in the developing mouse gonad
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure