The POL-2 polarimeter for the SCUBA-2 10 000 pixel Terahertz camera on the James Clerk Maxwell Telescope
(JCMT) in it's late state of commissioning. Proposals have been accepted for POL-2 and general observing will
start in August 2016. SCUBA-2 has a field of view of 43 arcmin at both of the 850 and 450 μm focal planes.
POL-2 will map the sky in the the 850 μm band. The POL-2 polarimeter utilizes three optical components: a
half wave plate and two wire-grid polarizers used as calibrator and analyzer covering the full field of SCUBA-2.
We describe the instrument, data acquisition and features/artifacts that have been encountered during the
The new high precision polarimeter for the “Observatoire du Mont Mégantic” (POMM) is an instrument designed to
observe exoplanets and other targets in the visible and near infrared wavebands. The requirements to achieve these
observation goals are posing unusual challenges to structural and mechanical designers.
In this paper, the detailed design, analysis and laboratory results of the key mechanical structure and sub-systems are
First, to study extremely low polarization, the birefringence effect due to stresses in the optical elements must be kept to
the lowest possible values. The double-wedge Wollaston custom prism assembly that splits the incoming optical beam is
made of bonded α-BBO to N-BK-7 glass lenses. Because of the large mismatch of coefficients of thermal expansion and
temperatures as low as -40°C that can be encountered at Mont-Mégantic observatory, a finite element analysis (FEA)
model is developed to find the best adhesive system to minimize stresses.
Another critical aspect discussed in details is the implementation of the cascaded rotating elements and the twin rotating
stages. Special attention is given to the drive mechanism and encoding technology. The objective was to reach high
absolute positional accuracy in rotation without any mechanical backlash.
As for many other instruments, mass, size and dimensional stability are important critera for the supporting structure.
For a cantilevered device, such as POMM, a static hexapod is an attractive solution because of the high stiffness to
weight ratio. However, the mechanical analysis revealed that the specific geometry of the dual channel optical layout
also added an off-axis counterbalancing problem. To reach an X-Y displacement error on the detector smaller than 35μm
for 0-45° zenith angle, further structural optimization was done using FEA. An imaging camera was placed at the
detector plane during assembly to measure the actual optical beam shift under varying gravitational loading.
A polarimeter, to observe exoplanets in the visible and infrared, was built for the “Observatoire du Mont Mégantic”
(OMM) to replace an existing instrument and reach 10-6 precision, a factor 100 improvement. The optical and
mechanical designs are presented, with techniques used to precisely align the optical components and rotation axes to
achieve the targeted precision. A photo-elastic modulator (PEM) and a lock-in amplifier are used to measure the
polarization. The typical signal is a high DC superimposed to a very faint sinusoidal oscillation. Custom electronics
was developed to measure the AC and DC amplitudes, and characterization results are presented.
A new polarimeter has been built for the “Observatoire du Mont-Mégantic” (POMM) and is now in commissioning
phase. It will allow polarization measurements with a precision of 10-6, an improvement by a factor of 100 over the
previous observatory polarimeter. The characteristics of the instrument that allow this goal are briefly discussed and the
planned science observations are presented. They include exoplanets near their host star (hot Jupiters), transiting
exoplanets, stars with debris disks, young stars with proto-planetary disks, brown dwarfs, massive Wolf-Rayet stars and
comets. The details of the optical and mechanical designs are presented in two other papers.
We present the optomechanical design of a polarimeter to be used with the SCUBA-2 camera at the James-Clerk-Maxwell Telescope. The polarimeter, built to study polarized sub-millimeter radiations, has a clear aperture of 269 mm
and is composed of three optical elements: a calibration polarizer, a half wave plate rotating at a speed of up to5 Hz, and
an analyzer polarizer. All three elements can be placed in and out of the beam, depending on the telescope's observation
A polarimeter is built to be used with the SCUBA-2 camera of the James Clerk Maxwell Telescope to study polarized sub-millimeter radiations. We simulated the effect of the polarimeter on image quality and polarization measurements.
SCUBA-2, which replaces SCUBA (the Submillimeter Common User Bolometer
Array) on the James Clerk Maxwell Telescope (JCMT) in 2006, is a
large-format bolometer array for submillimeter astronomy. Unlike previous detectors which have used discrete bolometers, SCUBA-2 has two dc-coupled, monolithic, filled arrays with a total of ~10,000 bolometers. It will offer simultaneous imaging of a 50 sq-arcmin field of view at wavelengths of 850 and 450 microns. SCUBA-2 is expected to have a huge impact on the study of galaxy formation and evolution in the early Universe as well as star and planet formation in our own Galaxy. Mapping the sky to the same S/N up to 1000 times faster than SCUBA, it will also act as a pathfinder for the new submillimeter interferometers such as ALMA. SCUBA-2's absorber-coupled pixels use superconducting transition edge sensors operating at 120 mK for performance limited by the sky background photon noise. The monolithic silicon detector arrays are deep-etched by the Bosch process to isolate the pixels on silicon nitride membranes. Electrical
connections are made through indium bump bonds to a SQUID time-domain multiplexer (MUX). We give an overview of the SCUBA-2 system and an update on its status, and describe some of the technological innovations that make this unique instrument possible.
An imaging polarimeter for the visible has been built for the mont Megantic Observatory. It uses a new design with a Foster prism which allows to obtain the two orthogonal beams of polarized light onto the detector at the same time, thus alleviating calibration problems associated with variations in the sky transparency during the observations. The field of view is 2.4 arc minutes at the f/15 focus of the telescope. A rotating achromatic half-wave plate is used to get all the linear polarization components and eliminate systematic calibration effects. Circularly polarized images can also be obtained by substituting a quarter-wave plate for the rotating half-wave plate. A user-friendly software for carrying out the data reduction has been developed.