31,249 research outputs found
A Corollary for Nonsmooth Systems
In this note, two generalized corollaries to the LaSalle-Yoshizawa Theorem
are presented for nonautonomous systems described by nonlinear differential
equations with discontinuous right-hand sides. Lyapunov-based analysis methods
are developed using differential inclusions to achieve asymptotic convergence
when the candidate Lyapunov derivative is upper bounded by a negative
semi-definite function
Long-range beam-beam experiments in the relativistic heavy ion collider
Long-range beam-beam effects are a potential limit to the LHC performance
with the nominal design parameters, and certain upgrade scenarios under
discussion. To mitigate long-range effects, current carrying wires parallel to
the beam were proposed and space is reserved in the LHC for such wires. Two
current carrying wires were installed in RHIC to study the effect of strong
long-range beam-beam effects in a collider, as well as test the compensation of
a single long-range interaction. The experimental data were used to benchmark
simulations. We summarize this work.Comment: 12 pages, contribution to the ICFA Mini-Workshop on Beam-Beam Effects
in Hadron Colliders, CERN, Geneva, Switzerland, 18-22 Mar 201
A mesocosm experiment investigating the effects of substratum quality and wave exposure on the survival of fish eggs
In a mesocosm experiment, the attachment of bream (Abramis brama) eggs to spawning substrata with and without periphytic biofilm coverage and their subsequent survival with and without low-intensity wave exposure were investigated. Egg attachment was reduced by 73% on spawning substrata with a natural periphytic biofilm, compared to clean substrata. Overall, this initial difference in egg numbers persisted until hatching. The difference in egg numbers was even increased in the wave treatment, while it was reduced in the no-wave control treatment. Exposure to a low-intensity wave regime affected egg development between the two biofilm treatments differently. Waves enhanced egg survival on substrata without a biofilm but reduced the survival of eggs on substrata with biofilm coverage. In the treatment combining biofilm-covered substrata and waves, no attached eggs survived until hatching. In all treatments, more than 75% of the eggs became detached from the spawning substrata during the egg incubation period, an
Readout Concepts for DEPFET Pixel Arrays
Field effect transistors embedded into a depleted silicon bulk (DEPFETs) can
be used as the first amplifying element for the detection of small signal
charges deposited in the bulk by ionizing particles, X-ray photons or visible
light. Very good noise performance at room temperature due to the low
capacitance of the collecting electrode has been demonstrated. Regular two
dimensional arrangements of DEPFETs can be read out by turning on individual
rows and reading currents or voltages in the columns. Such arrangements allow
the fast, low power readout of larger arrays with the possibility of random
access to selected pixels. In this paper, different readout concepts are
discussed as they are required for arrays with incomplete or complete clear and
for readout at the source or the drain. Examples of VLSI chips for the steering
of the gate and clear rows and for reading out the columns are presented.Comment: 8 pages, 9 figures, submitted to Nucl. Instr. and Methods as
proceedings of the 9th European Symposium on Semiconductor Detectors, Elmau,
June 23-27, 200
Existence of Long-Range Order for Trapped Interacting Bosons
We derive an inequality governing ``long range'' order for a localized
Bose-condensed state, relating the condensate fraction at a given temperature
with effective curvature radius of the condensate and total particle number.
For the specific example of a one-dimensional, harmonically trapped dilute Bose
condensate, it is shown that the inequality gives an explicit upper bound for
the Thomas-Fermi condensate size which may be tested in current experiments.Comment: 4 pages, 1 figure, RevTex4. Title changed at the request of editors;
to appear in Phys. Rev. Letter
Compact solid-state laser source for 1S-2S spectroscopy in atomic hydrogen
We demonstrate a novel compact solid-state laser source for high-resolution
two-photon spectroscopy of the transition in atomic hydrogen. The
source emits up to 20 mW at 243 nm and consists of a 972 nm diode laser, a
tapered amplifier, and two doubling stages. The diode laser is actively
stabilized to a high-finesse cavity. We compare the new source to the stable
486 nm dye laser used in previous experiments and record 1S-2S spectra using
both systems. With the solid-state laser system we demonstrate a resolution of
the hydrogen spectrometer of 6 \times 10^{11} which is promising for a number
of high-precision measurements in hydrogen-like systems
Six-dimensional weak-strong simulations of head-on beam-beam compensation in RHIC
To compensate the large beam-beam tune spread and beam-beam resonance driving
terms in the polarized proton operation in the Relativistic Heavy Ion Collider
(RHIC), we will introduce a low-energy DC electron beam into each ring to
collide head-on with the opposing proton beam. The device to provide the
electron beam is called an electron lens. In this article, using a 6-D
weak-strong-beam-beam interaction simulation model, we investigate the effects
of head-on beam-beam compensation with electron lenses on the proton beam
dynamics in the RHIC 250 GeV polarized proton operation. This article is
abridged from the published article [1].Comment: 5 pages, contribution to the ICFA Mini-Workshop on Beam-Beam Effects
in Hadron Colliders, CERN, Geneva, Switzerland, 18-22 Mar 201
Improving broadband displacement detection with quantum correlations
Interferometers enable ultrasensitive measurement in a wide array of
applications from gravitational wave searches to force microscopes. The role of
quantum mechanics in the metrological limits of interferometers has a rich
history, and a large number of techniques to surpass conventional limits have
been proposed. In a typical measurement configuration, the tradeoff between the
probe's shot noise (imprecision) and its quantum backaction results in what is
known as the standard quantum limit (SQL). In this work we investigate how
quantum correlations accessed by modifying the readout of the interferometer
can access physics beyond the SQL and improve displacement sensitivity.
Specifically, we use an optical cavity to probe the motion of a silicon nitride
membrane off mechanical resonance, as one would do in a broadband displacement
or force measurement, and observe sensitivity better than the SQL dictates for
our quantum efficiency. Our measurement illustrates the core idea behind a
technique known as \textit{variational readout}, in which the optical readout
quadrature is changed as a function of frequency to improve broadband
displacement detection. And more generally our result is a salient example of
how correlations can aid sensing in the presence of backaction.Comment: 17 pages, 5 figure
High-Precision Optical Measurement of the 2S Hyperfine Interval in Atomic Hydrogen
We have applied an optical method to the measurement of the 2S hyperfine
interval in atomic hydrogen. The interval has been measured by means of
two-photon spectroscopy of the 1S-2S transition on a hydrogen atomic beam
shielded from external magnetic fields. The measured value of the 2S hyperfine
interval is equal to 177 556 860(15) Hz and represents the most precise
measurement of this interval to date. The theoretical evaluation of the
specific combination of 1S and 2S hyperfine intervals D_21 is in moderately
good agreement with the value for D_21 deduced from our measurement
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