4,137 research outputs found
Physics of Proximity Josephson Sensor
We study the proximity Josephson sensor (PJS) in both bolometric and
calorimetric operation and optimize it for different temperature ranges between
25 mK and a few Kelvin. We investigate how the radiation power is absorbed in
the sensor and find that the irradiated sensor is typically in a weak
nonequilibrium state. We show in detail how the proximity of the
superconductors affects the device response: for example via changes in
electron-phonon coupling and out-of-equilibrium noise. In addition, we estimate
the applicability of graphene as the absorber material.Comment: 13 pages, 11 figures, submitted to Journal of Applied Physics, v2:
Addition of a new section discussing the radiation coupling to the device,
several minor change
Theory of temperature fluctuation statistics in superconductor-normal metal tunnel structures
We describe the statistics of temperature fluctuations in a SINIS structure,
where a normal metal island (N) is coupled by tunnel junctions (I) to two
superconducting leads (S). We specify conditions under which this structure
exhibits manifestly non-Gaussian fluctuations of temperature. We consider both
the Gaussian and non-Gaussian regimes of these fluctuations, and the current
fluctuations that are caused by the fluctuating temperature. We also describe a
measurement setup that could be used to observe the temperature fluctuations.Comment: 10 pages, 9 figures, final versio
Fully Overheated Single-Electron Transistor
We consider the fully overheated single-electron transistor, where the heat
balance is determined entirely by electron transfers. We find three distinct
transport regimes corresponding to cotunneling, single-electron tunneling, and
a competition between the two. We find an anomalous sensitivity to temperature
fluctuations at the crossover between the two latter regimes that manifests in
an exceptionally large Fano factor of current noise.Comment: 6 pages, 3 figures, includes Appendi
Delivered With Care. A National Survey of Women's Experience of Maternity Care 2010
As maternity services change and the population of women and families served also
changes, there is a need to document the views of women with recent experience of care.
Maternity services are evolving and the information from this study provides a picture of
current practice and point of comparison for the future. This survey was carried out in 2010
and used similar methods to those employed in 1995 and 2006. A random sample of 10,000
women giving birth in England over a two week period were selected by the Office for
National Statistics from birth registration records. Women whose babies had died and new
mothers less than 16 years of age were excluded. The usable response rate was 54%, with
5,333 women participating. A total of 14% of respondents came from Black and Minority
Ethnic (BME) groups and 21% had been born outside the UK. An online version of the
questionnaire was made available to all survey participants; only 8% of those responding
used this method of return.
Data were analysed and are presented by parity, with some specific univariate analyses in
relation to clinical factors such as mode of delivery and demographic factors, such as
maternal age or geographical region. Some comparisons are made with previous surveys.
Multivariate analyses, with adjustment for potential confounders, were carried out in relation
to 20 selected outcomes contributing to quality of care
Cyclostationary shot noise in mesoscopic measurements
We discuss theoretically a setup where a time-dependent current consisting of
a DC bias and two sinusoidal harmonics is driven through a sample. If the
sample exhibits current-dependent shot noise, the down-converted noise power
spectrum varies depending on the local-oscillator phase of the mixer. The
theory of this phase-dependent noise is applied to discuss the measurement of
the radio-frequency single-electron transistor. We also show that this effect
can be used to measure the shot noise accurately even in nonlinear
high-impedance samples.Comment: 3 pages, 2 figure
Microwave response of an NS ring coupled to a superconducting resonator
A long phase coherent normal (N) wire between superconductors (S) is
characterized by a dense phase dependent Andreev spectrum . We probe this
spectrum in a high frequency phase biased configuration, by coupling an NS ring
to a multimode superconducting resonator. We detect a dc flux and frequency
dependent response whose dissipative and non dissipative components are related
by a simple Debye relaxation law with a characteristic time of the order of the
diffusion time through the N part of the ring. The flux dependence exhibits
periodic oscillations with a large harmonics content at temperatures
where the Josephson current is purely sinusoidal. This is explained considering
that the populations of the Andreev levels are frozen on the time-scale of the
experiments.Comment: 5 pages,4 figure
- …