139 research outputs found
Exploring universality in nuclear clusters with Halo EFT
I present results and highlight aspects of halo EFT to loosely bound systems
composed of nucleons and alpha particles, with emphasis on Coulomb
interactions.Comment: 3 pages, 2 figures, talk given at the 21th European Conference on
Few-Body Problems in Physics, Salamanca, Aug. 29th - Sep. 3rd, 201
Hot electron-induced electrogenerated chemiluminescence of Ru(bpy)(3)(2+) chelate at a pointed active metal cathode in fully aqueous solutions
Tris(2,2'-bipyricline)ruthenium(II) chelate exhibits strong electrogenerated chemiluminescence during cathodic high-voltage pulse-polarization of pointed Pt electrode in aqueous solutions. The present method is based on a field emission or other type of tunnel emission of hot electrons into an aqueous electrolyte solution. The method allows the detection of tris(2,2'-bipyridine)ruthenium(II) and its derivatives below nanomolar concentration levels and yields linear log-log calibration plots spanning several orders of magnitude of concentration. (C) 2016 Elsevier B.V. All rights reserved
Centrifugal separation and equilibration dynamics in an electron-antiproton plasma
Charges in cold, multiple-species, non-neutral plasmas separate radially by
mass, forming centrifugally-separated states. Here, we report the first
detailed measurements of such states in an electron-antiproton plasma, and the
first observations of the separation dynamics in any centrifugally-separated
system. While the observed equilibrium states are expected and in agreement
with theory, the equilibration time is approximately constant over a wide range
of parameters, a surprising and as yet unexplained result. Electron-antiproton
plasmas play a crucial role in antihydrogen trapping experiments
Antihydrogen and mirror-trapped antiproton discrimination: Discriminating between antihydrogen and mirror-trapped antiprotons in a minimum-B trap
Recently, antihydrogen atoms were trapped at CERN in a magnetic minimum
(minimum-B) trap formed by superconducting octupole and mirror magnet coils.
The trapped antiatoms were detected by rapidly turning off these magnets,
thereby eliminating the magnetic minimum and releasing any antiatoms contained
in the trap. Once released, these antiatoms quickly hit the trap wall,
whereupon the positrons and antiprotons in the antiatoms annihilated. The
antiproton annihilations produce easily detected signals; we used these signals
to prove that we trapped antihydrogen. However, our technique could be
confounded by mirror-trapped antiprotons, which would produce
seemingly-identical annihilation signals upon hitting the trap wall. In this
paper, we discuss possible sources of mirror-trapped antiprotons and show that
antihydrogen and antiprotons can be readily distinguished, often with the aid
of applied electric fields, by analyzing the annihilation locations and times.
We further discuss the general properties of antiproton and antihydrogen
trajectories in this magnetic geometry, and reconstruct the antihydrogen energy
distribution from the measured annihilation time history.Comment: 17 figure
Alpha Antihydrogen Experiment
ALPHA is an experiment at CERN, whose ultimate goal is to perform a precise
test of CPT symmetry with trapped antihydrogen atoms. After reviewing the
motivations, we discuss our recent progress toward the initial goal of stable
trapping of antihydrogen, with some emphasis on particle detection techniques.Comment: Invited talk presented at the Fifth Meeting on CPT and Lorentz
Symmetry, Bloomington, Indiana, June 28-July 2, 201
A novel antiproton radial diagnostic based on octupole induced ballistic loss
We report results from a novel diagnostic that probes the outer radial
profile of trapped antiproton clouds. The diagnostic allows us to determine the
profile by monitoring the time-history of antiproton losses that occur as an
octupole field in the antiproton confinement region is increased. We show
several examples of how this diagnostic helps us to understand the radial
dynamics of antiprotons in normal and nested Penning-Malmberg traps. Better
understanding of these dynamics may aid current attempts to trap antihydrogen
atoms
Compression of Antiproton Clouds for Antihydrogen Trapping
Control of the radial profile of trapped antiproton clouds is critical to
trapping antihydrogen. We report the first detailed measurements of the radial
manipulation of antiproton clouds, including areal density compressions by
factors as large as ten, by manipulating spatially overlapped electron plasmas.
We show detailed measurements of the near-axis antiproton radial profile and
its relation to that of the electron plasma
Antihydrogen formation dynamics in a multipolar neutral anti-atom trap
Antihydrogen production in a neutral atom trap formed by an octupole-based
magnetic field minimum is demonstrated using field-ionization of weakly bound
anti-atoms. Using our unique annihilation imaging detector, we correlate
antihydrogen detection by imaging and by field-ionization for the first time.
We further establish how field-ionization causes radial redistribution of the
antiprotons during antihydrogen formation and use this effect for the first
simultaneous measurements of strongly and weakly bound antihydrogen atoms.
Distinguishing between these provides critical information needed in the
process of optimizing for trappable antihydrogen. These observations are of
crucial importance to the ultimate goal of performing CPT tests involving
antihydrogen, which likely depends upon trapping the anti-atom
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