7 research outputs found
Common but unappreciated sources of error in one, two, and multiple-color pyrometry
The most common sources of error in optical pyrometry are examined. They can be classified as either noise and uncertainty errors, stray radiation errors, or speed-of-response errors. Through judicious choice of detectors and optical wavelengths the effect of noise errors can be minimized, but one should strive to determine as many of the system properties as possible. Careful consideration of the optical-collection system can minimize stray radiation errors. Careful consideration must also be given to the slowest elements in a pyrometer when measuring rapid phenomena
An electrostatic levitator for high-temperature containerless materials processing in 1-g
This article discusses recent developments in high-temperature electrostatic levitation technology for containerless processing of metals and alloys. Presented is the first demonstration of an electrostatic levitation technology which can levitate metals and alloys (2–4 mm diam spheres) in vacuum and of superheating-undercooling-recalescence cycles which can be repeated while maintaining good positioning stability. The electrostatic levitator (ESL) has several important advantages over the electromagnetic levitator. Most important is the wide range of sample temperature which can be achieved without affecting levitation. This article also describes the general architecture of the levitator, electrode design, position control hardware and software, sample heating, charging, and preparation methods, and operational procedures. Particular emphasis is given to sample charging by photoelectric and thermionic emission. While this ESL is more oriented toward ground-based operation, an extension to microgravity applications is also addressed briefly. The system performance was demonstrated by showing multiple superheating-undercooling-recalescence cycles in a zirconium sample (Tm=2128 K). This levitator, when fully matured, will be a valuable tool both in Earth-based and space-based laboratories for the study of thermophysical properties of undercooled liquids, nucleation kinetics, the creation of metastable phases, and access to a wide range of materials with novel properties
KAPAO: a MEMS-based natural guide star adaptive optics system
We describe KAPAO, our project to develop and deploy a low-cost,
remote-access, natural guide star adaptive optics (AO) system for the Pomona
College Table Mountain Observatory (TMO) 1-meter telescope. We use a
commercially available 140-actuator BMC MEMS deformable mirror and a version of
the Robo-AO control software developed by Caltech and IUCAA. We have structured
our development around the rapid building and testing of a prototype system,
KAPAO-Alpha, while simultaneously designing our more capable final system,
KAPAO-Prime. The main differences between these systems are the prototype's
reliance on off-the-shelf optics and a single visible-light science camera
versus the final design's improved throughput and capabilities due to the use
of custom optics and dual-band, visible and near-infrared imaging. In this
paper, we present the instrument design and on-sky closed-loop testing of
KAPAO-Alpha as well as our plans for KAPAO-Prime. The primarily
undergraduate-education nature of our partner institutions, both public (Sonoma
State University) and private (Pomona and Harvey Mudd Colleges), has enabled us
to engage physics, astronomy, and engineering undergraduates in all phases of
this project. This material is based upon work supported by the National
Science Foundation under Grant No. 0960343.Comment: 10 pages and 11 figure
KAPAO First Light: the design, construction and operation of a low-cost natural guide star adaptive optics system
We present the instrument design and first light observations of KAPAO, a natural guide star adaptive optics (AO) system for the Pomona College Table Mountain Observatory (TMO) 1-meter telescope. The KAPAO system has dual science channels with visible and near-infrared cameras, a Shack-Hartmann wavefront sensor, and a commercially available 140-actuator MEMS deformable mirror. The pupil relays are two pairs of custom off-axis parabolas and the control system is based on a version of the Robo-AO control software. The AO system and telescope are remotely operable, and KAPAO is designed to share the Cassegrain focus with the existing TMO polarimeter. We discuss the extensive integration of undergraduate students in the program including the multiple senior theses/capstones and summer assistantships amongst our partner institutions. This material is based upon work supported by the National Science Foundation under Grant No. 0960343