Report on the B23 bread-board Prototype Integration @ESO for optical warm tests

The scope of the breadboard B23 prototype is to setup the optical chain (OMT+FH+Filters+Lens) to perform beam measurements to provide a full assessment of the extended frequency range technical capabilities to demonstrate the feasibility of the development of B23 cartridge for ALMA. On November 2015 the breadboard was integrated and setup to perform warm beam tests with the beam scanner at ESO. The pre-integration @ INAF and the integration @ESO was under the responsibility of INAF/IASF-bologna. The iALMA-TEC-ICD-IAB-001-H [AD1] interface control document reports all the information about the entire prototype system, including design solutions and configurations

B23 Cartridge Prototype Manufacturing and Integration Report

This document reports on the manufacturing and assembly of the B23 Prototype cartridge to perform cryogenic noise tests @ INAF/IASF-Bologna

ALMA band 2+3 (67-116 GHz) optics: Design and first measurements

The ALMA telescope is one of the largest on-ground astronomical projects in the world. It has been producing great scientific results since the beginning of operations in 2011. Of all the originally planned bands, band 2 (67-90 GHz) is the last band to be implemented into the array. Recent technological progress has open the possibility to combine bands 2 and 3 (84-116 GHz) into a single wideband receiver. This paper describes the first efforts to design wideband optics which cover both bands, from 67 to 116 GHz, using a profiled corrugated horn and a modified Fresnel lens. First measurements were performed at ESO in Dec15-Jan16 and showed good agreement with simulations

Solar Science with the Atacama Large Millimeter/Submillimeter Array — A New View of Our Sun

The Atacama Large Millimeter/submillimeter Array (ALMA) is a new powerful tool for observing the Sun at high spatial, temporal, and spectral resolution. These capabilities can address a broad range of fundamental scientific questions in solar physics. The radiation observed by ALMA originates mostly from the chromosphere—a complex and dynamic region between the photosphere and corona, which plays a crucial role in the transport of energy and matter and, ultimately, the heating of the outer layers of the solar atmosphere. Based on first solar test observations, strategies for regular solar campaigns are currently being developed. State-of-the-art numerical simulations of the solar atmosphere and modeling of instrumental effects can help constrain and optimize future observing modes for ALMA. Here we present a short technical description of ALMA and an overview of past efforts and future possibilities for solar observations at submillimeter and millimeter wavelengths. In addition, selected numerical simulations and observations at other wavelengths demonstrate ALMA’s scientific potential for studying the Sun for a large range of science cases

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

Design and Measurement of Possible Wide-band 67-116 GHz ALMA Vacuum Window Anti-reflection Layers

A new broad-band vacuum lens/window design is required for the new Atacama Large Millimeter/submillimeter Array (ALMA) band 2 receiver, intended to cover 67-116 GHz. A suitable anti-reflection coating (ARC) for this will be necessary. This paper presents the optimization of a candidate ARC designin ultra-high molecular weight polyethylene (UHMWPE), aswell as simulations and measurements of candidate designs insilicon. Machined triangular grooves are used as the ARC for the UHMWPE candidates, and stacked cuboids for the silicon candidate design

Systematic study of the cross polarization introduced by broadband antireflection layers at microwave frequencies

\u3cp\u3eImplementation of antireflection layers using structured materials is of common use in millimeter-and submillimeter-wave refractive optic systems. In this work we have systematically studied the effect of such structures in the optical propagation with special emphasis on the cross polarization they introduce. We have performed extensive simulations and experimental verification of several commonly used structures: concentric grooves, parallel grooves, an array of boxes, an array of cylinders, and rectangular-versus triangular-shaped grooves. As a result, we propose optimal structures for demanding applications in terms of polarization and return losses over large fractional bandwidths.\u3c/p\u3