1,900 research outputs found
The end-to-end testbed of the Optical Metrology System on-board LISA Pathfinder
LISA Pathfinder is a technology demonstration mission for the Laser
Interferometer Space Antenna (LISA). The main experiment on-board LISA
Pathfinder is the so-called LISA Technology Package (LTP) which has the aim to
measure the differential acceleration between two free-falling test masses with
an accuracy of 3x10^(-14) ms^(-2)/sqrt[Hz] between 1 mHz and 30 mHz. This
measurement is performed interferometrically by the Optical Metrology System
(OMS) on-board LISA Pathfinder. In this paper we present the development of an
experimental end-to-end testbed of the entire OMS. It includes the
interferometer and its sub-units, the interferometer back-end which is a
phasemeter and the processing of the phasemeter output data. Furthermore,
3-axes piezo actuated mirrors are used instead of the free-falling test masses
for the characterisation of the dynamic behaviour of the system and some parts
of the Drag-free and Attitude Control System (DFACS) which controls the test
masses and the satellite. The end-to-end testbed includes all parts of the LTP
that can reasonably be tested on earth without free-falling test masses. At its
present status it consists mainly of breadboard components. Some of those have
already been replaced by Engineering Models of the LTP experiment. In the next
steps, further Engineering Models and Flight Models will also be inserted in
this testbed and tested against well characterised breadboard components. The
presented testbed is an important reference for the unit tests and can also be
used for validation of the on-board experiment during the mission
The Impact of Gender-Biased Language in State Regulations Upon Judgments About Foster Children
This study investigated the impact of gender-biased language in the wording of state regulations governing the treatment of foster children in Illinois. Participants were given excerpts of legal language written with either gender-biased or gender-inclusive language and then asked to judge a hypothetical situation involving a male or a female child. It was hypothesized that gender-biased language would have differential effects on interpretation of the language for boys versus girls; we also proposed a moderated mediation model that hypothesized activation of gendered constructs would mediate the interpretation of gendered language. According to the hypothesized model, participant sexism and attitudes towards gender-biased language would moderate these relationships. Analyses were conducted using data collected from 274 participants using an online survey on Amazon’s Mechanical Turk. Analyses did not support our main hypotheses; language type and gender of child did not significantly affect participant evaluations of the hypothetical scenario, and the hypothesized moderated mediation model was not supported. Possible explanations for these findings and future directions are discussed
Three-port beam splitters-combiners for interferometer applications
We derive generic phase and amplitude coupling relations for beam
splitters-combiners that couple a single port with three output ports or input
ports, respectively. We apply the coupling relations to a reflection grating
that serves as a coupler to a single-ended Fabry-Perot ring cavity. In the
impedance-matched case such an interferometer can act as an all-reflective ring
mode cleaner. It is further shown that in the highly undercoupled case almost
complete separation of carrier power and phase signal from a cavity strain can
be achieved
In-plane gate single-electron transistor in Ga[Al]As fabricated by scanning probe lithography
A single-electron transistor has been realized in a Ga[Al]As heterostructure
by oxidizing lines in the GaAs cap layer with an atomic force microscope. The
oxide lines define the boundaries of the quantum dot, the in-plane gate
electrodes, and the contacts of the dot to source and drain. Both the number of
electrons in the dot as well as its coupling to the leads can be tuned with an
additional, homogeneous top gate electrode. Pronounced Coulomb blockade
oscillations are observed as a function of voltages applied to different gates.
We find that, for positive top-gate voltages, the lithographic pattern is
transferred with high accuracy to the electron gas. Furthermore, the dot shape
does not change significantly when in-plane voltages are tuned.Comment: 4 pages, 3 figure
Frequency domain interferometer simulation with higher-order spatial modes
FINESSE is a software simulation that allows to compute the optical
properties of laser interferometers as they are used by the interferometric
gravitational-wave detectors today. It provides a fast and versatile tool which
has proven to be very useful during the design and the commissioning of
gravitational-wave detectors. The basic algorithm of FINESSE numerically
computes the light amplitudes inside an interferometer using Hermite-Gauss
modes in the frequency domain. In addition, FINESSE provides a number of
commands to easily generate and plot the most common signals like, for example,
power enhancement, error or control signals, transfer functions and
shot-noise-limited sensitivities.
Among the various simulation tools available to the gravitational wave
community today, FINESSE is the most advanced general optical simulation that
uses the frequency domain. It has been designed to allow general analysis of
user defined optical setups while being easy to install and easy to use.Comment: Added an example for the application of the simulation during the
commisioning of the GEO 600 gravitational-wave detecto
Eigenmode in a misaligned triangular optical cavity
We derive relationships between various types of small misalignments on a
triangular Fabry-Perot cavity and associated geometrical eigenmode changes. We
focus on the changes of beam spot positions on cavity mirrors, the beam waist
position, and its angle. A comparison of analytical and numerical results shows
excellent agreement. The results are applicable to any triangular cavity close
to an isosceles triangle, with the lengths of two sides much bigger than the
other, consisting of a curved mirror and two flat mirrors yielding a waist
equally separated from the two flat mirrors. This cavity shape is most commonly
used in laser interferometry. The analysis presented here can easily be
extended to more generic cavity shapes. The geometrical analysis not only
serves as a method of checking a simulation result, but also gives an intuitive
and handy tool to visualize the eigenmode of a misaligned triangular cavity.Comment: 17 pages, 21 figure
Thermal broadening of the Coulomb blockade peaks in quantum Hall interferometers
We demonstrate that the differential magnetic susceptibility of a fractional
quantum Hall disk, representing a Coulomb island in a Fabry--Perot
interferometer, is exactly proportional to the island's conductance and its
paramagnetic peaks are the equilibrium counterparts of the Coulomb blockade
conductance peaks. Using as a thermodynamic potential the partition functions
of the edge states' effective conformal field theory we find the positions of
the Coulomb blockade peaks, when the area of the island is varied, the
modulations of the distance between them as well as the thermal decay and
broadening of the peaks when temperature is increased. The finite-temperature
estimates of the peak's heights and widths could give important information
about the experimental observability of the Coulomb blockade. In addition, the
predicted peak asymmetry and displacement at finite temperature due to neutral
multiplicities could serve to distinguish different fractional quantum Hall
states with similar zero-temperature Coulomb blockade patterns.Comment: 6 pages, 6 figures; published versio
Impurity and edge roughness scattering in armchair graphene nanoribbons: Boltzmann approach
The conductivity of armchair graphene nanoribbons in the presence of
short-range impurities and edge roughness is studied theoretically using the
Boltzmann transport equation for quasi-one-dimensional systems. As the number
of occupied subbands increases, the conductivity due to short-range impurities
converges towards the two-dimensional case. Calculations of the
magnetoconductivity confirm the edge-roughness-induced dips at cyclotron radii
close to the ribbon width suggested by the recent quantum simulations
- …