38,364 research outputs found
An improved rocket-borne electric field meter for the middle atmosphere
Improvements in a rocketborne electric field meter designed to measure the atmosphere's electric field and conductivity in the middle atmosphere are described. The general background of the experiment is given as well as changes in the instrument and data processing schemes. Calibration and testing procedures are documented together with suggestions for future work
NIKA: A millimeter-wave kinetic inductance camera
Current generation millimeter wavelength detectors suffer from scaling limits
imposed by complex cryogenic readout electronics. To circumvent this it is
imperative to investigate technologies that intrinsically incorporate strong
multiplexing. One possible solution is the kinetic inductance detector (KID).
In order to assess the potential of this nascent technology, a prototype
instrument optimized for the 2 mm atmospheric window was constructed. Known as
the N\'eel IRAM KIDs Array (NIKA), it was recently tested at the Institute for
Millimetric Radio Astronomy (IRAM) 30-meter telescope at Pico Veleta, Spain.
The measurement resulted in the imaging of a number of sources, including
planets, quasars, and galaxies. The images for Mars, radio star MWC349, quasar
3C345, and galaxy M87 are presented. From these results, the optical NEP was
calculated to be around WHz. A factor of 10
improvement is expected to be readily feasible by improvements in the detector
materials and reduction of performance-degrading spurious radiation.Comment: Accepted for publication in Astronomy & Astrophysic
Magnetic and electric field meters developed for the US Department of Energy
This report describes work done at the Jet Propulsion Laboratory for the Office of Energy Storage and Distribution of DOE on the measurement of power line fields. A magnetic field meter is discussed that uses fiber optics to couple a small measuring probe to a remote readout device. The use of fiber optics minimizes electric field perturbation due to the presence of the probe and provides electric isolation for the probe, so that it could be used in a high field or high voltage environment. Power to operate the sensor electronics is transferred via an optical fiber, and converted to electrical form by a small photodiode array. The fundamental, the second and third harmonics of the field are filtered and separately measured, as well as the broadband rms level of the field. The design of the meter is described in detail and data from laboratory tests are presented. The report also describes work done to improve the performance of a DC bushing in a Swedish factory, using the improved meter. The DC electric fields are measured with synchronous detection to provide field magnitude data in two component directions
Microwave Measurements Part I: Linear Measurements
An Overview of the most relevant issues concerning RF and microwave linear measurements is presented. Vector Network Analyzer foremost used instrumentation for this kind of measures is describe
An integrated development facility for the calibration of low-energy charged particle flight instrumentation
A system was developed for the calibration and development of thermal ion instrumentation. The system provides an extended beam with usable current rates, approx. 1 pA/sq cm, at beam energies as low as 1 eV, with much higher values available with increasing energy. A tandem electrostatic and variable geometry magnetic mirror configuration within the ion source optimizes the use of the ionizing electrons. The system is integrated under microcomputer control to allow automatic control and monitoring of the beam energy and composition and the mass and angle-dependent response of the instrument under test. The system is pumped by a combination of carbon vane and cryogenic sorption roughing pumps and ion and liquid helium operating pumps
Reionization and Cosmology with 21 cm Fluctuations
Measurement of the spatial distribution of neutral hydrogen via the
redshifted 21 cm line promises to revolutionize our knowledge of the epoch of
reionization and the first galaxies, and may provide a powerful new tool for
observational cosmology from redshifts 1<z<4 . In this review we discuss recent
advances in our theoretical understanding of the epoch of reionization (EoR),
the application of 21 cm tomography to cosmology and measurements of the dark
energy equation of state after reionization, and the instrumentation and
observational techniques shared by 21 cm EoR and post reionization cosmology
machines. We place particular emphasis on the expected signal and observational
capabilities of first generation 21 cm fluctuation instruments.Comment: Invited review for Annual Review of Astronomy and Astrophysics (2010
volume
Development of limb volume measuring system
The mechanisms underlying the reductions in orthostatic tolerance associated with weightlessness are not well established. Contradictory results from measurements of leg volume changes suggest that altered venomotor tone and reduced blood flow may not be the only contributors to orthostatic intolerance. It is felt that a more accurate limb volume system which is insensitive to environmental factors will aid in better quantification of the hemodynamics of the leg. Of the varous limb volume techniques presently available, the ultrasonic limb volume system has proven to be the best choice. The system as described herein is free from environmental effects, safe, simple to operate and causes negligible radio frequency interference problems. The segmental ultrasonic ultrasonic plethysmograph is expected to provide a better measurement of limb volume change since it is based on cross-sectional area measurements
Breadboard linear array scan imager using LSI solid-state technology
The performance of large scale integration photodiode arrays in a linear array scan (pushbroom) breadboard was evaluated for application to multispectral remote sensing of the earth's resources. The technical approach, implementation, and test results of the program are described. Several self scanned linear array visible photodetector focal plane arrays were fabricated and evaluated in an optical bench configuration. A 1728-detector array operating in four bands (0.5 - 1.1 micrometer) was evaluated for noise, spectral response, dynamic range, crosstalk, MTF, noise equivalent irradiance, linearity, and image quality. Other results include image artifact data, temporal characteristics, radiometric accuracy, calibration experience, chip alignment, and array fabrication experience. Special studies and experimentation were included in long array fabrication and real-time image processing for low-cost ground stations, including the use of computer image processing. High quality images were produced and all objectives of the program were attained
Air Shower Measurements with the LOPES Radio Antenna Array
LOPES is set up at the location of the KASCADE-Grande extensive air shower
experiment in Karlsruhe, Germany and aims to measure and investigate radio
pulses from Extensive Air Showers. Since radio waves suffer very little
attenuation, radio measurements allow the detection of very distant or highly
inclined showers. These waves can be recorded day and night, and provide a
bolometric measure of the leptonic shower component. LOPES is designed as a
digital radio interferometer using high bandwidths and fast data processing and
profits from the reconstructed air shower observables of KASCADE-Grande. The
LOPES antennas are absolutely amplitude calibrated allowing to reconstruct the
electric field strength which can be compared with predictions from detailed
Monte Carlo simulations. We report about the analysis of correlations present
in the radio signals measured by the LOPES 30 antenna array. Additionally,
LOPES operates antennas of a different type (LOPES-STAR) which are optimized
for an application at the Pierre Auger Observatory. Status, recent results of
the data analysis and further perspectives of LOPES and the possible large
scale application of this new detection technique are discussed.Comment: 8 pages, 10 figures, Contribution to the Arena 2008 conference, Rome,
June 200
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