13 research outputs found
A millimeter-wave kinetic inductance detector camera for long-range imaging through optical obscurants
Millimeter-wave imaging provides a promising option for long-range target detection through optical obscurants such as fog, which often occur in marine environments. Given this motivation, we are currently developing a 150 GHz polarization-sensitive imager using a relatively new type of superconducting pair-breaking detector, the kinetic inductance detector (KID). This imager will be paired with a 1.5 m telescope to obtain an angular resolution of 0.09° over a 3.5° field of view using 3,840 KIDs. We have fully characterized a prototype KID array, which shows excellent performance with noise strongly limited by the irreducible fluctuations from the ambient temperature background. Full-scale KID arrays are now being fabricated and characterized for a planned demonstration in a maritime environment later this year
A millimeter-wave kinetic inductance detector camera for long-range imaging through optical obscurants
Millimeter-wave imaging provides a promising option for long-range target detection through optical obscurants such as fog, which often occur in marine environments. Given this motivation, we are currently developing a 150 GHz polarization-sensitive imager using a relatively new type of superconducting pair-breaking detector, the kinetic inductance detector (KID). This imager will be paired with a 1.5 m telescope to obtain an angular resolution of 0.09° over a 3.5° field of view using 3,840 KIDs. We have fully characterized a prototype KID array, which shows excellent performance with noise strongly limited by the irreducible fluctuations from the ambient temperature background. Full-scale KID arrays are now being fabricated and characterized for a planned demonstration in a maritime environment later this year
A cryogenic rotation stage with a large clear aperture for the half-wave plates in the Spider instrument
We describe the cryogenic half-wave plate rotation mechanisms built for and
used in Spider, a polarization-sensitive balloon-borne telescope array that
observed the Cosmic Microwave Background at 95 GHz and 150 GHz during a
stratospheric balloon flight from Antarctica in January 2015. The mechanisms
operate at liquid helium temperature in flight. A three-point contact design
keeps the mechanical bearings relatively small but allows for a large (305 mm)
diameter clear aperture. A worm gear driven by a cryogenic stepper motor allows
for precise positioning and prevents undesired rotation when the motors are
depowered. A custom-built optical encoder system monitors the bearing angle to
an absolute accuracy of +/- 0.1 degrees. The system performed well in Spider
during its successful 16 day flight.Comment: 11 pages, 7 figures, Published in Review of Scientific Instruments.
v2 includes reviewer changes and longer literature revie
Modeling and characterization of the SPIDER half-wave plate
Spider is a balloon-borne array of six telescopes that will observe the
Cosmic Microwave Background. The 2624 antenna-coupled bolometers in the
instrument will make a polarization map of the CMB with approximately one-half
degree resolution at 145 GHz. Polarization modulation is achieved via a
cryogenic sapphire half-wave plate (HWP) skyward of the primary optic. We have
measured millimeter-wave transmission spectra of the sapphire at room and
cryogenic temperatures. The spectra are consistent with our physical optics
model, and the data gives excellent measurements of the indices of A-cut
sapphire. We have also taken preliminary spectra of the integrated HWP, optical
system, and detectors in the prototype Spider receiver. We calculate the
variation in response of the HWP between observing the CMB and foreground
spectra, and estimate that it should not limit the Spider constraints on
inflation
Pointing control for the SPIDER balloon-borne telescope
We present the technology and control methods developed for the pointing
system of the SPIDER experiment. SPIDER is a balloon-borne polarimeter designed
to detect the imprint of primordial gravitational waves in the polarization of
the Cosmic Microwave Background radiation. We describe the two main components
of the telescope's azimuth drive: the reaction wheel and the motorized pivot. A
13 kHz PI control loop runs on a digital signal processor, with feedback from
fibre optic rate gyroscopes. This system can control azimuthal speed with <
0.02 deg/s RMS error. To control elevation, SPIDER uses stepper-motor-driven
linear actuators to rotate the cryostat, which houses the optical instruments,
relative to the outer frame. With the velocity in each axis controlled in this
way, higher-level control loops on the onboard flight computers can implement
the pointing and scanning observation modes required for the experiment. We
have accomplished the non-trivial task of scanning a 5000 lb payload
sinusoidally in azimuth at a peak acceleration of 0.8 deg/s, and a peak
speed of 6 deg/s. We can do so while reliably achieving sub-arcminute pointing
control accuracy.Comment: 20 pages, 12 figures, Presented at SPIE Ground-based and Airborne
Telescopes V, June 23, 2014. To be published in Proceedings of SPIE Volume
914
Modeling and characterization of the SPIDER half-wave plate
Spider is a balloon-borne array of six telescopes that will observe the Cosmic Microwave Background. The 2624 antenna-coupled bolometers in the instrument will make a polarization map of the CMB with approximately one-half degree resolution at 145 GHz. Polarization modulation is achieved via a cryogenic sapphire half-wave plate (HWP) skyward of the primary optic. We have measured millimeter-wave transmission spectra of the sapphire at room and cryogenic temperatures. The spectra are consistent with our physical optics model, and the data gives excellent measurements of the indices of A-cut sapphire. We have also taken preliminary spectra of the integrated HWP, optical system, and detectors in the prototype Spider receiver. We calculate the variation in response of the HWP between observing the CMB and foreground spectra, and estimate that it should not limit the Spider constraints on inflation
A cryogenic rotation stage with a large clear aperture for the half-wave plates in the Spider instrument
Storage of household firearms: an examination of the attitudes and beliefs of married women with children
Although safe firearm storage is a promising injury prevention strategy, many parents do not keep their firearms unloaded and locked up. Using the theory of planned behavior as a guiding conceptual framework, this study examines factors associated with safe storage among married women with children and who have firearms in their homes. Data come from a national telephone survey (n = 185). We examined beliefs about defensive firearm use, subjective norms, perceived behavioral control and firearm storage practices. A Wilcoxon–Mann–Whitney test was conducted to assess associations between psychosocial factors and firearm storage practices. Women were highly motivated to keep firearms stored safely. Those reporting safe storage practices had more favorable attitudes, more supportive subjective norms and higher perceptions of behavioral control than those without safe storage. One-fourth believed a firearm would prevent a family member from being hurt in case of a break-in, 58% believed a firearm could scare off a burglar. Some 63% said they leave decisions about firearm storage to their husbands. Women were highly motivated to store firearms safely as evidenced by favorable attitudes, supportive subjective norms and high perceptions of behavioral control. This was especially true for those reporting safer storage practices