The Yuan-Tseh Lee Array for Microwave Background Anisotropy

The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) is the first interferometer dedicated to studying the cosmic microwave background (CMB) radiation at 3mm wavelength. The choice of 3mm was made to minimize the contributions from foreground synchrotron radiation and Galactic dust emission. The initial configuration of seven 0.6m telescopes mounted on a 6-m hexapod platform was dedicated in October 2006 on Mauna Loa, Hawaii. Scientific operations began with the detection of a number of clusters of galaxies via the thermal Sunyaev-Zel'dovich effect. We compare our data with Subaru weak lensing data in order to study the structure of dark matter. We also compare our data with X-ray data in order to derive the Hubble constant.Comment: accepted for publication in ApJ (13 pages, 7 figures); a version with high resolution figures available at http://www.asiaa.sinica.edu.tw/~keiichi/upfiles/AMiBA7/pho_highreso.pd

The AMiBA Hexapod Telescope Mount

AMiBA is the largest hexapod astronomical telescope in current operation. We present a description of this novel hexapod mount with its main mechanical components -- the support cone, universal joints, jack screws, and platform -- and outline the control system with the pointing model and the operating modes that are supported. The AMiBA hexapod mount performance is verified based on optical pointing tests and platform photogrammetry measurements. The photogrammetry results show that the deformations in the inner part of the platform are less than 120 micron rms. This is negligible for optical pointing corrections, radio alignment and radio phase errors for the currently operational 7-element compact configuration. The optical pointing error in azimuth and elevation is successively reduced by a series of corrections to about 0.4 arcmin rms which meets our goal for the 7-element target specifications.Comment: Accepted for ApJ, 33 pages, 15 figure

Design and Characterization of the ALMA Band 5 Vacuum Window

This paper summarizes the electromagnetic design process of the vacuum window for the Atacama Large Millimeter/sub-millimeter Array (ALMA) Band 5 (163-211 GHz). We have carried out investigations by means of numerical simulations as well as reflection and transmission measurements. Simulations were performed using the finite element method, an efficient quasi-analytical technique, and rigorous coupled-wave analysis. We used an injection-molded vacuum window prototype as a starting point of the design process and investigated deterioration in the electromagnetic performance caused by different types of manufacturing artifacts. Following these analyses, an optimization of the window has been performed based on simulations. We measured the reflectivity and transmittance of the newly designed window and this paper demonstrates that the optimized window exhibits a return loss better than -20 dB, as required by the ALMA specifications