TY - JOUR
T1 - ALMA Band 1 Optics (35–50 GHz)
T2 - Tolerance analysis, effect of cryostat infrared filters and cold beam measurements
AU - Gonzalez, A.
AU - Tapia, V.
AU - Finger, R.
AU - Huang, C. D.
AU - Asayama, S.
AU - Huang, Y. D.
PY - 2017/10/1
Y1 - 2017/10/1
N2 - The Atacama Large Millimeter/Sub-millimeter Array (ALMA) is currently the largest (sub-)mm wave telescope in the world and will be used for astronomical observations in all atmospheric windows from 35 to 950 GHz when completed. The ALMA band 1 (35–50 GHz) receiver will be used for the longest wavelength observations with ALMA. Because of the longer wavelength, the size of optics and waveguide components will be larger than for other ALMA bands. In addition, all components will be placed inside the ALMA cryostat in each antenna, which will impose severe mechanical constraints on the size and position of receiver optics components. Due to these constraints, the designs of the corrugated feed horn and lens optics are highly optimized to comply with the stringent ALMA optical requirements. In this paper, we perform several tolerance analyses to check the impact of fabrication errors in such an optimized design. Secondly, we analyze the effects of operating this optics inside the ALMA cryostat, in particular the effects of having the cryostat IR filters placed next to the band 1 feed horn aperture, with the consequent near-field effects. Finally, we report on beam measurements performed on the first three ALMA band 1 receivers inside test cryostats, which satisfy ALMA specifications. In these measurements, we can clearly observe the effects of fabrication tolerances and IR filter effects on prototype receiver performance.
AB - The Atacama Large Millimeter/Sub-millimeter Array (ALMA) is currently the largest (sub-)mm wave telescope in the world and will be used for astronomical observations in all atmospheric windows from 35 to 950 GHz when completed. The ALMA band 1 (35–50 GHz) receiver will be used for the longest wavelength observations with ALMA. Because of the longer wavelength, the size of optics and waveguide components will be larger than for other ALMA bands. In addition, all components will be placed inside the ALMA cryostat in each antenna, which will impose severe mechanical constraints on the size and position of receiver optics components. Due to these constraints, the designs of the corrugated feed horn and lens optics are highly optimized to comply with the stringent ALMA optical requirements. In this paper, we perform several tolerance analyses to check the impact of fabrication errors in such an optimized design. Secondly, we analyze the effects of operating this optics inside the ALMA cryostat, in particular the effects of having the cryostat IR filters placed next to the band 1 feed horn aperture, with the consequent near-field effects. Finally, we report on beam measurements performed on the first three ALMA band 1 receivers inside test cryostats, which satisfy ALMA specifications. In these measurements, we can clearly observe the effects of fabrication tolerances and IR filter effects on prototype receiver performance.
KW - ALMA
KW - Corrugated horn
KW - Cryogenic receiver
KW - Dielectric lens
KW - mm-wave
KW - mm-wave measurements
KW - Quasi-optics
KW - Radio astronomy
KW - Tolerance analysis
UR - http://www.scopus.com/inward/record.url?scp=85021715554&partnerID=8YFLogxK
U2 - 10.1007/s10762-017-0414-x
DO - 10.1007/s10762-017-0414-x
M3 - Article
VL - 38
SP - 1215
EP - 1231
JO - Journal of Infrared, Millimeter, and Terahertz Waves
JF - Journal of Infrared, Millimeter, and Terahertz Waves
SN - 1866-6892
IS - 10
ER -