31 research outputs found
Atom Interferometry in Space: Thermal Management and Magnetic Shielding
Atom interferometry is an exciting tool to probe fundamental physics. It is
considered especially apt to test the universality of free fall by using two
different sorts of atoms. The increasing sensitivity required for this kind of
experiment sets severe requirements on its environments, instrument control,
and systematic effects. This can partially be mitigated by going to space as
was proposed, for example, in the Spacetime Explorer and Quantum Equivalence
Principle Space Test (STE-QUEST) mission. However, the requirements on the
instrument are still very challenging. For example, the specifications of the
STE-QUEST mission imply that the Feshbach coils of the atom interferometer are
allowed to change their radius only by about 260 nm or 2.6E-4% due to thermal
expansion although they consume an average power of 22 W. Also Earth's magnetic
field has to be suppressed by a factor of 10E5. We show in this article that
with the right design such thermal and magnetic requirements can indeed be met
and that these are not an impediment for the exciting physics possible with
atom interferometers in space.Comment: v2: minor changes to agree with published version; 8 pages, 6 figure
A Vulnerability Assessment of Fish and Invertebrates to Climate Change on the Northeast U.S. Continental Shelf
Climate change and decadal variability are impacting marine fish and invertebrate species worldwide and these impacts will continue for the foreseeable future. Quantitative approaches have been developed to examine climate impacts on productivity, abundance, and distribution of various marine fish and invertebrate species. However, it is difficult to apply these approaches to large numbers of species owing to the lack of mechanistic understanding sufficient for quantitative analyses, as well as the lack of scientific infrastructure to support these more detailed studies. Vulnerability assessments provide a framework for evaluating climate impacts over a broad range of species with existing information. These methods combine the exposure of a species to a stressor (climate change and decadal variability) and the sensitivity of species to the stressor. These two components are then combined to estimate an overall vulnerability. Quantitative data are used when available, but qualitative information and expert opinion are used when quantitative data is lacking. Here we conduct a climate vulnerability assessment on 82 fish and invertebrate species in the Northeast U.S. Shelf including exploited, forage, and protected species. We define climate vulnerability as the extent to which abundance or productivity of a species in the region could be impacted by climate change and decadal variability. We find that the overall climate vulnerability is high to very high for approximately half the species assessed; diadromous and benthic invertebrate species exhibit the greatest vulnerability. In addition, the majority of species included in the assessment have a high potential for a change in distribution in response to projected changes in climate. Negative effects of climate change are expected for approximately half of the species assessed, but some species are expected to be positively affected (e.g., increase in productivity or move into the region). These results will inform research and management activities related to understanding and adapting marine fisheries management and conservation to climate change and decadal variability
Design of a dual species atom interferometer for space
Atom interferometers have a multitude of proposed applications in space
including precise measurements of the Earth's gravitational field, in
navigation & ranging, and in fundamental physics such as tests of the weak
equivalence principle (WEP) and gravitational wave detection. While atom
interferometers are realized routinely in ground-based laboratories, current
efforts aim at the development of a space compatible design optimized with
respect to dimensions, weight, power consumption, mechanical robustness and
radiation hardness. In this paper, we present a design of a high-sensitivity
differential dual species Rb/Rb atom interferometer for space,
including physics package, laser system, electronics and software. The physics
package comprises the atom source consisting of dispensers and a 2D
magneto-optical trap (MOT), the science chamber with a 3D-MOT, a magnetic trap
based on an atom chip and an optical dipole trap (ODT) used for Bose-Einstein
condensate (BEC) creation and interferometry, the detection unit, the vacuum
system for mbar ultra-high vacuum generation, and the
high-suppression factor magnetic shielding as well as the thermal control
system. The laser system is based on a hybrid approach using fiber-based
telecom components and high-power laser diode technology and includes all laser
sources for 2D-MOT, 3D-MOT, ODT, interferometry and detection. Manipulation and
switching of the laser beams is carried out on an optical bench using Zerodur
bonding technology. The instrument consists of 9 units with an overall mass of
221 kg, an average power consumption of 608 W (819 W peak), and a volume of 470
liters which would well fit on a satellite to be launched with a Soyuz rocket,
as system studies have shown.Comment: 30 pages, 23 figures, accepted for publication in Experimental
Astronom
STE-QUEST - Test of the Universality of Free Fall Using Cold Atom Interferometry
In this paper, we report about the results of the phase A mission study of the atom
interferometer instrument covering the description of the main payload elements, the
atomic source concept, and the systematic error sources
High-Performance Optical Frequency References for Space
A variety of future space missions rely on the availability of high-Performance optical clocks with applications in fundamental physics, geoscience, Earth observation and
navigation and ranging. Examples are the gravitational wave detector eLISA (evolved Laser Interferometer Space Antenna), the Earth gravity mission NGGM (Next Generation Gravity Mission) and missions, dedicated to tests of Special Relativity, e.g. by performing a Kennedy-
Thorndike experiment testing the boost dependence of the speed of light. In this context we developed optical frequency references based on Doppler-free spectroscopy of molecular iodine; compactness and mechanical and thermal stability are main design criteria. With a setup
on engineering model (EM) level we demonstrated a frequency stability of about 2ïżœ1
BOOST - Testing Fundamental Physics in Space
We are presenting the small satellite mission BOOST (BOOst Symmetry Test). It aims for testing the foundations of special relativity by performing a modern Kennedy-Thorndike (KT) experiment. A potential violation of the Lorentz invariance is measured by comparing two types of clocks, a highly stable optical resonator (length reference) with a molecular iodine clock (frequency reference). For realizing a small satellite compatible payload, the use
of diode-laser technology is favorable and currently already under investigation with respect to other space experiments. A laser wavelength of 1016 nm is foreseen as its second harmonics accesses narrow linewidth transitions in molecular iodine. Both lasers are directly compared in a beat measurement and analyzed with respect to a possible violation of boost invariance. By employing clocks with 10Eâ16 frequency stabilities at orbit time and by integration over 5000 orbits, a 1000-fold improvement in measuring the Kennedy-Thorndike coefficient is targeted compared to the current best terrestrial test