First observations with CONDOR, a 1.5 THz heterodyne receiver

Abstract

Context. The THz atmospheric "windows", centered at roughly 1.3 and 1.5 THz, contain numerous spectral lines of astronomical importance, including three high-J CO lines, the [N II] line at 205 µm, and the ground transition of para-H 2 D + . The CO lines are tracers of hot (several 100 K), dense gas; [N II] is a cooling line of diffuse, ionized gas; the H 2 D + line is a non-depleting tracer of cold (∼20 K), dense gas. Aims. As the THz lines benefit the study of diverse phenomena (from high-mass star-forming regions to the WIM to cold prestellar cores), we have built the CO N + Deuterium Observations Receiver (CONDOR) to further explore the THz windows by ground-based observations. Methods. CONDOR was designed to be used at the Atacama Pathfinder EXperiment (APEX) and Stratospheric Observatory For Infrared Astronomy (SOFIA). CONDOR was installed at the APEX telescope and test observations were made to characterize the instrument.Results. The combination of CONDOR on APEX successfully detected THz radiation from astronomical sources. CONDOR operated with typical T rec = 1600 K and spectral Allan variance times of ∼30 s. CONDOR's "first light" observations of CO 13−12 emission from the hot core Orion FIR 4 (= OMC1 South) revealed a narrow line with T MB ≈ 210 K and ∆V ≈ 5.4 km s −1 . A search for [N II] emission from the ionization front of the Orion Bar resulted in a non-detection. Conclusions. The successful deployment of CONDOR at APEX demonstrates the potential for making observations at THz frequencies from ground-based facilities.

Application of Superconducting Hot-Electron Bolometer Mixers for Terahertz-Band Astronomy

“…CONDOR employs a closedcycle PT cryocooler and solid-state LO sources manufactured by Radiometer Physics GmbH and Virginia Diode, Inc. With CONDOR, observations of high-J CO lines, the transition line of [N II], and the ground transition of para-H 2 D + , which are good tracers of hot dense gas, ionized diffuse gas, and cold dense gas, respectively, were demonstrated toward Orion FIR4 in 2006 [52]. The University of Tokyo group started astronomical observation by installing their own 0.9-and 1.3-THz-band waveguide-type NbTiN HEB mixers onto the 10-m Atacama Submillimeter Telescope Experiment (ASTE) located at Pampa La Bola in northern Chile (at an altitude of 4860 m) in 2011 [19].…”

Active local oscillator power stabilization for a hot electron bolometer heterodyne receiver

“…Previous studies have also demonstrated improved stability by stabilizing the incident LO power in an HEB [5][6][7][8][9][10]. However until now, they have been either frequency or LO-source specific.…”

Stabilized hot electron bolometer heterodyne receiver at 2.5 THz

“…[6][7][8][9][10] Balanced waveguide HEB mixers have demonstrated improved stability 11 but at the expense of complex device design and fabrication. Furthermore, it has been shown that it is possible to stabilize an HEB mixer by stabilizing the amplitude of a far infrared (FIR) gas laser LO by adding electrical feedback to its CO 2 pumping laser.…”