21,860 research outputs found
Track Extrapolation and Distribution for the CDF-II Trigger System
The CDF-II experiment is a multipurpose detector designed to study a wide
range of processes observed in the high energy proton-antiproton collisions
produced by the Fermilab Tevatron. With event rates greater than 1MHz, the
CDF-II trigger system is crucial for selecting interesting events for
subsequent analysis. This document provides an overview of the Track
Extrapolation System (XTRP), a component of the CDF-II trigger system. The XTRP
is a fully digital system that is utilized in the track-based selection of high
momentum lepton and heavy flavor signatures. The design of the XTRP system
includes five different custom boards utilizing discrete and FPGA technology
residing in a single VME crate. We describe the design, construction,
commissioning and operation of this system.Comment: 34 pages, 9 figures, submitted to Nucl.Inst.Meth.
Verification and Control of Partially Observable Probabilistic Real-Time Systems
We propose automated techniques for the verification and control of
probabilistic real-time systems that are only partially observable. To formally
model such systems, we define an extension of probabilistic timed automata in
which local states are partially visible to an observer or controller. We give
a probabilistic temporal logic that can express a range of quantitative
properties of these models, relating to the probability of an event's
occurrence or the expected value of a reward measure. We then propose
techniques to either verify that such a property holds or to synthesise a
controller for the model which makes it true. Our approach is based on an
integer discretisation of the model's dense-time behaviour and a grid-based
abstraction of the uncountable belief space induced by partial observability.
The latter is necessarily approximate since the underlying problem is
undecidable, however we show how both lower and upper bounds on numerical
results can be generated. We illustrate the effectiveness of the approach by
implementing it in the PRISM model checker and applying it to several case
studies, from the domains of computer security and task scheduling
Phase locking a clock oscillator to a coherent atomic ensemble
The sensitivity of an atomic interferometer increases when the phase
evolution of its quantum superposition state is measured over a longer
interrogation interval. In practice, a limit is set by the measurement process,
which returns not the phase, but its projection in terms of population
difference on two energetic levels. The phase interval over which the relation
can be inverted is thus limited to the interval ; going beyond
it introduces an ambiguity in the read out, hence a sensitivity loss. Here, we
extend the unambiguous interval to probe the phase evolution of an atomic
ensemble using coherence preserving measurements and phase corrections, and
demonstrate the phase lock of the clock oscillator to an atomic superposition
state. We propose a protocol based on the phase lock to improve atomic clocks
under local oscillator noise, and foresee the application to other atomic
interferometers such as inertial sensors.Comment: 9 pages, 7 figure
Experimental Clock Calibration\\on a Crystal-Free Mote-on-a-Chip
The elimination of the off-chip frequency reference, typically a crystal
oscillator, would bring important benefits in terms of size, price and energy
efficiency to IEEE802.15.4 compliant radios and systems-on-chip. The stability
of on-chip oscillators is orders of magnitude worse than that of a crystal. It
is known that as the temperature changes, they can drift more than 50
ppm/{\deg}C. This paper presents the result of an extensive experimental study.
First, we propose mechanisms for crystal-free radios to be able to track an
IEEE802.15.4 join proxy, calibrate the on-chip oscillators and maintain
calibration against temperature changes. Then, we implement the resulting
algorithms on a crystal-free platform and present the results of an
experimental validation. We show that our approach is able to track a
crystal-based IEEE802.15.4-compliant join proxy and maintain the requested
radio frequency stability of +/-40 ppm, even when subject to temperature
variation of 2{\deg}C/min.Comment: CNERT: Computer and Networking Experimental Research using Testbeds,
in conjunction with IEEE INFOCOM 2019, April 29 - May 2, 2019, Paris, Franc
Range imager performance comparison in homodyne and heterodyne operating modes
Range imaging cameras measure depth simultaneously for every pixel in a given field of view. In most implementations the basic operating principles are the same. A scene is illuminated with an intensity modulated light source and the reflected signal is sampled using a gain-modulated imager. Previously we presented a unique heterodyne range imaging system that employed a bulky and power hungry image intensifier as the high speed gain-modulation mechanism. In this paper we present a new range imager using an internally modulated image sensor that is designed to operate in heterodyne mode, but can also operate in homodyne mode. We discuss homodyne and heterodyne range imaging, and the merits of the various types of hardware used to implement these systems. Following this we describe in detail the hardware and firmware components of our new ranger. We experimentally compare the two operating modes and demonstrate that heterodyne operation is less sensitive to some of the limitations suffered in homodyne mode, resulting in better linearity and ranging precision characteristics. We conclude by showing various qualitative examples that demonstrate the system’s three-dimensional measurement performance
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