4,564 research outputs found
On the Response of an OST to a Point-like Heat Source
A new technique of superconducting cavity diagnostics has been introduced by
D. Hartrill at Cornell University, Ithaca, USA. Oscillating Superleak
Transducers (OST) detect the heat transferred from a cavity's quench point via
"Second Sound" through the superfluid He bath, needed to cool the
superconducting cavity. The observed response of an OST is a complex, but
reproducible pattern of oscillations. A small helium evaporation cryostat was
built which allows the investigation of the response of an OST in greater
detail. The distance between a point-like electrical heater and the OST can be
varied. The OST can be mounted either parallel or perpendicular to the plate,
housing the heat source. If the artificial quench-point releases an amount of
energy compatible to a real quench spot on a cavity's surface, the OST signal
starts with a negative pulse, which is usually strong enough to allow automatic
detection. Furthermore, the reflection of the Second Sound on the wall is
observed. A reflection coefficient R = 0.39 +- 0.05 of the glass wall is
measured. This excludes a strong influence of multiple reflections in the
complex OST response. Fourier analyses show three main frequencies, found in
all OST spectra. They can be interpreted as modes of an oscillating circular
membrane.Comment: 10 pages, 16 figure
High-K ankaramitic melt inclusions and lavas in the Upper Cretaceous Eastern Srednogorie continental arc, Bulgaria: Implications for the genesis of arc shoshonites
Split-grain 40Ar/39Ar dating : integrating temporal and geochemical data from crystal cargoes
NERC is acknowledged for continued funding of AIF at SUERC, East Kilbride. This work was supported by an ETH research grant (ETH-05 13-2) and funds from Swiss National Science Foundation research grants (SNSF 200021-146268 and SNSF 200021-155923/1) and US National Science Grant 1425491.Large sanidine crystals from the Mesa Falls Tuff (MFT), Yellowstone volcanic field, have been split and individually dated via high-precision 40Ar/39Ar geochronology with the undated portions further analysed for major elements, trace elements, Pb and Sr isotopes in the sanidine and trace elements in the melt inclusions. This allows the geochemical and geochronological identity of an individual sanidine to be combined. Our MFT sanidines return a preferred eruption age of 1.3011 ± 0.0015/0.0016 Ma (2-sigma, n = 56, MSWD 0.8, analytical/full external) with a significant component of subtly older (up to ~ 2 Ma) crystals. Combined with recent results (Rivera et al., 2016, Journal of Petrology 57, 9, 1677–1704) our data define a global mean sanidine 40Ar/39Ar age for the MFT of 1.3022 ± 0.0006/0.0008 Ma (2 sigma, analytical/full external) relative to Alder Creek sanidine at 1.1891 Ma and total λ40Ar 5.5305e-10, which gives RACsMFT: 1.09542 ± 0.00050. The ability to couple geochemistry and geochronology from a single grain allows us, for the first time, to evaluate the origin of the subtly older sanidines present in the same pumices as juvenile sanidines. Melt inclusions from all Mesa Falls sanidines represent extremely fractionated melts with low Sr contents (max. 12 ppm, n = 39), and rare earth element patterns which require that they be formed from an A-type magma rather than the preceding subduction-related Eocene volcanism as previously suggested. 87Sr/86Sr from juvenile and subtly older sanidines shows the same range of 0.7073 to 0.7096, illustrating the susceptibility of such low-Sr melts to slight degrees of assimilation. Pb isotopic compositions are more restricted and identical between the juvenile and subtly older sanidines in the Mesa Falls Tuff (207Pb/206Pb 0.900–0.903, 208Pb/206Pb 2.217–2.226, n = 83) and these compositions rule out the underlying Huckleberry Ridge Tuff member B as a potential source for the subtly older sanidine. LA-ICPMS 206Pb/238U dating of Mesa Falls zircons supports no role for the Huckleberry Ridge Tuff. Rather, these subtly older sanidines are interpreted as containing excess mantle-derived Ar. The ability to couple the geochemical and geochronological records within individual sanidine crystals that we demonstrate here has potential to provide new insights for a variety of petrological studies such as diffusional modelling.PostprintPeer reviewe
Sensitivity to measurement perturbation of single atom dynamics in cavity QED
We consider continuous observation of the nonlinear dynamics of single atom
trapped in an optical cavity by a standing wave with intensity modulation. The
motion of the atom changes the phase of the field which is then monitored by
homodyne detection of the output field. We show that the conditional Hilbert
space dynamics of this system, subject to measurement induced perturbations,
depends strongly on whether the corresponding classical dynamics is regular or
chaotic. If the classical dynamics is chaotic the distribution of conditional
Hilbert space vectors corresponding to different observation records tends to
be orthogonal. This is a characteristic feature of hypersensitivity to
perturbation for quantum chaotic systems.Comment: 11 pages, 6 figure
Dynamical quantum noise in Bose-Einstein condensates
We introduce the study of dynamical quantum noise in Bose-Einstein
condensates through numerical simulation of stochastic partial differential
equations obtained using phase space representations. We derive evolution
equations for a single trapped condensate in both the positive- and Wigner
representations, and perform simulations to compare the predictions of the two
methods. The positive- approach is found to be highly susceptible to the
stability problems that have been observed in other strongly nonlinear, weakly
damped systems. Using the Wigner representation, we examine the evolution of
several quantities of interest using from a variety of choices of initial state
for the condensate, and compare results to those for single-mode models.Comment: 8 figures, submitted to Phys. Rev.
HV/HR-CMOS sensors for the ATLAS upgrade—concepts and test chip results
In order to extend its discovery potential, the Large Hadron Collider (LHC) will have a major upgrade (Phase II Upgrade) scheduled for 2022. The LHC after the upgrade, called High-Luminosity LHC (HL-LHC), will operate at a nominal leveled instantaneous luminosity of 5× 1034 cm−2 s−1, more than twice the expected Phase I . The new Inner Tracker needs to cope with this extremely high luminosity. Therefore it requires higher granularity, reduced material budget and increased radiation hardness of all components. A new pixel detector based on High Voltage CMOS (HVCMOS) technology targeting the upgraded ATLAS pixel detector is under study. The main advantages of the HVCMOS technology are its potential for low material budget, use of possible cheaper interconnection technologies, reduced pixel size and lower cost with respect to traditional hybrid pixel detector. Several first prototypes were produced and characterized within ATLAS upgrade R&D effort, to explore the performance and radiation hardness of this technology.
In this paper, an overview of the HVCMOS sensor concepts is given. Laboratory tests and irradiation tests of two technologies, HVCMOS AMS and HVCMOS GF, are also given
Radiation-hard active pixel sensors for HL-LHC detector upgrades based on HV-CMOS technology
Luminosity upgrades are discussed for the LHC (HL-LHC) which would make updates to the detectors necessary, requiring in particular new, even more radiation-hard and granular, sensors for the inner detector region.
A proposal for the next generation of inner detectors is based on HV-CMOS: a new family of silicon sensors based on commercial high-voltage CMOS technology, which enables the fabrication of part of the pixel electronics inside the silicon substrate itself.
The main advantages of this technology with respect to the standard silicon sensor technology are: low material budget, fast charge collection time, high radiation tolerance, low cost and operation at room temperature.
A traditional readout chip is still needed to receive and organize the data from the active sensor and to handle high-level functionality such as trigger management. HV-CMOS has been designed to be compatible with both pixel and strip readout.
In this paper an overview of HV2FEI4, a HV-CMOS prototype in 180 nm AMS technology, will be given. Preliminary results after neutron and X-ray irradiation are shown
State determination in continuous measurement
The possibility of determining the state of a quantum system after a
continuous measurement of position is discussed in the framework of quantum
trajectory theory. Initial lack of knowledge of the system and external noises
are accounted for by considering the evolution of conditioned density matrices
under a stochastic master equation. It is shown that after a finite time the
state of the system is a pure state and can be inferred from the measurement
record alone. The relation to emerging possibilities for the continuous
experimental observation of single quanta, as for example in cavity quantum
electrodynamics, is discussed.Comment: 12 pages, 4 figures, Revte
Determination of alpha_s using Jet Rates at LEP with the OPAL detector
Hadronic events produced in e+e- collisions by the LEP collider and recorded
by the OPAL detector were used to form distributions based on the number of
reconstructed jets. The data were collected between 1995 and 2000 and
correspond to energies of 91 GeV, 130-136 GeV and 161-209 GeV. The jet rates
were determined using four different jet-finding algorithms (Cone, JADE, Durham
and Cambridge). The differential two-jet rate and the average jet rate with the
Durham and Cambridge algorithms were used to measure alpha(s) in the LEP energy
range by fitting an expression in which order alpah_2s calculations were
matched to a NLLA prediction and fitted to the data. Combining the measurements
at different centre-of-mass energies, the value of alpha_s (Mz) was determined
to be
alpha(s)(Mz)=0.1177+-0.0006(stat.)+-0.0012$(expt.)+-0.0010(had.)+-0.0032(theo.)
\.Comment: 40 pages, 17 figures, Submitted to Euro. Phys. J.
Colour reconnection in e+e- -> W+W- at sqrt(s) = 189 - 209 GeV
The effects of the final state interaction phenomenon known as colour
reconnection are investigated at centre-of-mass energies in the range sqrt(s) ~
189-209 GeV using the OPAL detector at LEP. Colour reconnection is expected to
affect observables based on charged particles in hadronic decays of W+W-.
Measurements of inclusive charged particle multiplicities, and of their angular
distribution with respect to the four jet axes of the events, are used to test
models of colour reconnection. The data are found to exclude extreme scenarios
of the Sjostrand-Khoze Type I (SK-I) model and are compatible with other
models, both with and without colour reconnection effects. In the context of
the SK-I model, the best agreement with data is obtained for a reconnection
probability of 37%. Assuming no colour reconnection, the charged particle
multiplicity in hadronically decaying W bosons is measured to be (nqqch) =
19.38+-0.05(stat.)+-0.08 (syst.).Comment: 30 pages, 9 figures, Submitted to Euro. Phys. J.
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