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6 pags., 2 figs., 2 tabs., We present the first identification in interstellar space of the propargyl radical (CH2CCH). This species was observed in the cold dark cloud TMC-1 using the Yebes 40 m telescope. The six strongest hyperfine components of the 20,2-10,1 rotational transition, lying at 37.46 GHz, were detected with signal-to-noise ratios from 4.6σ to 12.3σ. We derived a column density of 8.7 × 1013 cm-2 for CH2CCH, which translates to a fractional abundance relative to H2 of 8.7 × 10-9. This radical has a similar abundance as methyl acetylene, with an abundance ratio CH2CCH/CH3CCH close to one. The propargyl radical is thus one of the most abundant radicals detected in TMC-1, and it is probably the most abundant organic radical with a certain chemical complexity ever found in a cold dark cloud. We constructed a gas-phase chemical model and find calculated abundances that agree with, or fall two orders of magnitude below, the observed value depending on the poorly constrained low-temperature reactivity of CH2CCH with neutral atoms. According to the chemical model, the propargyl radical is essentially formed by the C + C2H4 reaction and by the dissociative recombination of C3$ \rm{H}n $ ions with n = 4-6. The propargyl radical is believed to control the synthesis of the first aromatic ring in combustion processes, and it probably plays a key role in the synthesis of large organic molecules and cyclization processes to benzene in cold dark clouds., We acknowledge funding support from Spanish MICIU through grants AYA2016-75066-C2-1-P, PID2019-106110GB-I00, and PID2019-107115GBC21 and from the European Research Council (ERC Grant 610256: NANOCOSMOS). M.A. also acknowledges funding support from the Ramón y Cajal programme of Spanish MICIU (grant RyC-2014-16277).

51 pags., 43 figs., 3 tabs., Context. The carbon-rich envelope of the asymptotic giant branch star CW Leo, IRC+10216, is one of the richest molecular sources in the sky. Available spectral surveys below 51 GHz are more than 25 years old, and new work is needed. Aims. Characterizing the rich molecular content of this source, specially for heavy species, requires carrying out very sensitive spectral surveys at low frequencies. In particular, we have achieved an rms in the range 0.2-0.6mK per MHz. Methods. Long Q band (31.0-50.3 GHz) single-dish integrations were carried out with the Yebes-40m telescope using specifically built receivers. The most recent line catalogs were used to identify the lines. Results. The data contain 652 spectral features, corresponding to 713 transitions from 81 species (we count the isomers, isotopologs, and ortho/para species separately). Only 57 unidentified lines remain with signal-to-noise ratios ≤3. Some new species and/or vibrational modes have been discovered for the first time with this survey. Conclusions. This IRC+10216 spectral survey is by far the most sensitive survey carried out to date in the Q band. It therefore provides the most complete view of IRC+10216 from 31.0 to 50.3 GHz, giving unique information about its molecular content, especially for heavy species. Rotational diagrams built from the data provide valuable information about the physical conditions and chemical content of this circumstellar envelope., We thank Ministerio de Ciencia e Innovación of Spain for funding support through projects PID2019-106110GB-I00, PID2019- 107115GB-C21/AEI/10.13039/501100011033, PID2019-106235GB-I00, and grant FJCI-2016-27983 for CB. We also thank ERC for funding through grant ERC-2013-Syg-610256-NANOCOSMOS. M.A. thanks MICIU for grant RyC2014-16277.

ALMA has been operating since 2011, but has not yet been populated with the full suite of intended frequency bands. In particular, ALMA Band 2 (67-90 GHz) is the final band in the original ALMA band definition to be approved for production. We aim to produce a wideband, tuneable, sideband-separating receiver with 28 GHz of instantaneous bandwidth per polarisation operating in the sky frequency range 67-116 GHz. Our design anticipates new ALMA requirements following the recommendations in the 2030 ALMA Development Roadmap. The cryogenic cartridge is designed to be compatible with the ALMA Band 2 cartridge slot, where the coldest components -- the feedhorns, orthomode transducers, and cryogenic low noise amplifiers -- operate at a temperature of 15 K. We use multiple simulation methods and tools to optimise our designs for both the passive optics and the active components. The cryogenic cartridge interfaces with a room temperature cartridge hosting the local oscillator (LO) and the downconverter module. This warm cartridge is largely based on GaAs semiconductor technology and is optimised to match the cryogenic receiver bandwidth with the required instantaneous LO tuning range. Our collaboration has designed, fabricated, and tested multiple technical solutions for each of the components, producing a state-of-the-art receiver covering the full ALMA Band 2 & 3 atmospheric window. The receiver is suitable for deployment on ALMA in the coming years, and is capable of dual-polarisation, sideband-separating observations in intermediate frequency bands spanning 4-18 GHz, for a total of 28 GHz on-sky bandwidth per polarisation channel. We conclude that the 67-116 GHz wideband implementation for ALMA Band 2 is now feasible, and this receiver is a compelling instrumental upgrade that will enhance observational capabilities and scientific reach., 23 pages, accepted for publication in A&A on 20 Dec 2019. This version corrects the affiliations of 2 co-authors

The Relic Axion Detector Experimental Setup (RADES) is an axion search project that uses a microwave filter as resonator for Dark Matter conversion. The main focus of this publication is the description of the 3 different cavity prototypes of RADES. The result of the first tests of one of the prototypes is also presented. The filters consist of 5 or 6 stainless steel sub-cavities joined by rectangular irises. The size of the sub-cavities determines the working frequency, the amount of sub-cavities determine the working volume. The first cavity prototype was built in 2017 to work at a frequency of $\sim$ 8.4 GHz and it was placed at the 9 T CAST dipole magnet at CERN. Two more prototypes were designed and built in 2018. The aim of the new designs is to find and test the best cavity geometry in order to scale up in volume and to introduce an effective tuning mechanism. Our results demonstrate the promising potential of this type of filter to reach QCD axion sensitivity at X-Band frequencies., Comment: Proceedings for the 3rd Axion Cavity and Detector Workshop, Livermore Valley Open Campus August 21-25th, 2018

This paper shows the development of a simultaneous tri-band (S: 2.2 - 2.7 GHz, X: 7.5 - 9 GHz and Ka: 28 - 33 GHz) low-noise cryogenic receiver for geodetic Very Long Baseline Interferometry (geo-VLBI) which has been developed by the technical staff of Yebes Observatory (IGN) laboratories in Spain. The receiver was installed in the first radio telescope of the Red Atlántica de Estaciones Geodinámicas y Espaciales (RAEGE) project, which is located in Yebes Observatory, in the frame of the VLBI Global Observing System (VGOS). After this, the receiver was borrowed by the Norwegian Mapping Autorithy (NMA) for the commissioning of two VGOS radiotelescopes in Svalbard (Norway). A second identical receiver was built for the Ishioka VGOS station of the Geospatial Information Authority (GSI) of Japan, and a third one for the second RAEGE VGOS station, located in Santa María (Açores Archipelago, Portugal). The average receiver noise temperatures are 21, 23 and 25 Kelvin and the measured antenna efficiencies are 70%, 75% and 60% in S-band, X-band and Ka-band, respectively.

74th ISMS 2019, University of Illinois, at Urbana-Champaign, June 17 - 21, 2019

25th International Conference on High Resolution Molecular Spectroscopy. 3 al 7 de septiembre en el Bizkaia Aretoa (Bilbao, Spain)(2018). --.http://www.hrms-bilbao2018.com/

We report the detection of the sulfur-bearing species NCS, HCCS, H2CCS, H2CCCS, and C4S for the first time in space. These molecules were found towards TMC-1 through the observation of several lines for each species. We also report the detection of C5S for the first time in a cold cloud through the observation of five lines in the 31-50 GHz range. The derived column densities are N(NCS) = (7.8 +/- 0.6)e11 cm-2, N(HCCS) = (6.8 +/- 0.6)e11 cm-2, N(H2CCS) = (7.8 +/- 0.8)e11 cm-2, N(H2CCCS) = (3.7 +/- 0.4)e11 cm-2, N(C4S) = (3.8 +/- 0.4)e10 cm-2, and N(C5S) = (5.0 +/- 1.0)e10 cm-2. The observed abundance ratio between C3S and C4S is 340, that is to say a factor of approximately one hundred larger than the corresponding value for CCS and C3S. The observational results are compared with a state-of-the-art chemical model, which is only partially successful in reproducing the observed abundances. These detections underline the need to improve chemical networks dealing with S-bearing species., Comment: Accepted for publication in A&A Letters

We report the detection in TMC-1 of the protonated form of C3S. The discovery of the cation HC3S+ was carried through the observation of four harmonically related lines in the Q band using the Yebes 40m radiotelescope, and is supported by accurate ab initio calculations and laboratory measurements of its rotational spectrum. We derive a column density N(HC3S+) = (2.0 +/- 0.5)e11 cm-2, which translates to an abundance ratio C3S/HC3S+ of 65 +/- 20. This ratio is comparable to the CS/HCS+ ratio (35 +/- 8) and is a factor of about ten larger than the C3O/HC3O+ ratio previously found in the same source. However, the abundance ratio HC3O+/HC3S+ is 1.0 +/- 0.5, while C3O/C3S is just 0.11. We also searched for protonated C2S in TMC-1, based on ab initio calculations of its spectroscopic parameters, and derive a 3sigma upper limit of N(HC2S+) < 9e11 cm-2 and a C2S/HC2S+ > 60. The observational results are compared with a state-of-the-art gas-phase chemical model and conclude that HC3S+ is mostly formed through several pathways: proton transfer to C3S, reaction of S+ with c-C3H2, and reaction between neutral atomic sulfur and the ion C3H3+., Accepted for publication in A&A Letters

Champaign-Urbana, Illinois, United States, 17 - 21 June 2019

10 pags., 5 figs., 7 tabs., 5 apps., We report on the detection of two series of harmonically related doublets in IRC+10216. From the observed frequencies, the rotational constant of the first series is B = 1380.888 MHz and that of the second series is B = 1381.512 MHz. The two series correspond to two species with a 2Σ electronic ground state. After considering all possible candidates, and based on quantum chemical calculations, the first series is assigned to MgC3N and the second to MgC4H. For the latter species, optical spectroscopy measurements support its identification. Unlike diatomic metal-containing molecules, the line profiles of the two new molecules indicate that they are formed in the outer layers of the envelope, as occurs for MgNC and other polyatomic metal-cyanides. We also confirm the detection of MgCCH that was previously reported from the observation of two doublets. The relative abundance of MgC3N with respect to MgNC is close to one while that of MgC4H relative to MgCCH is about ten. The synthesis of these magnesium cyanides and acetylides in IRC+10216 can be explained in terms of a two-step process initiated by the radiative association of Mg+ with large cyanopolyynes and polyynes followed by the dissociative recombination of the ionic complexes., The Spanish authors thank the Ministerio de Ciencia Innovación y Universidades for funding support from the CONSOLIDER-Ingenio program “ASTROMOL” CSD 2009-00038, AYA2012-32032, AYA2016-75066-C2-1-P. We also thank ERC for funding through grant ERC-2013-Syg610256-NANOCOSMOS. MA thanks the Ministerio de Ciencia Innovación y Universidades for the Ramón y Cajal grant RyC-2014-16277. CB thanks the Ministerio de Ciencia Innovación y Universidades for the Juan de la Cierva grant FJCI-2016-27983. LVP acknowledges support from the Swedish Research Council and from ERC consolidator grant 614

In this paper, the room-temperature and cryogenic performance of two low-noise amplifier (LNA) modules in the frequency range from 70 to 116 GHz is presented and analyzed. The investigation is based on LNA millimeter-wave integrated circuits using 35-nm and 50-nm gate-length metamorphic high-electron-mobility transistor technologies. At room temperature, the WM-2540 waveguide modules demonstrate an average noise temperature of 214 and 247 K over the 70–116-GHz frequency range. The lowest achieved noise temperatures are 171 and 196 K. When cooling the LNA modules to an ambient temperature of 6 K, the average noise temperatures improve to 30.1 and 31 K. The lowest achieved noise temperatures are 20.7 and 19.2 K. To the best of the authors' knowledge, the demonstrated LNAs yield the lowest published average noise temperatures at room temperature over the 70–116-GHz frequency range. Furthermore, the achieved cryogenic noise performance is among the best results published so far.

Two broadband very low-noise amplifiers operating in the frequency range from 4 to 12 GHz at cryogenic temperature are presented. The amplifier circuits have been developed using a 100 nm gate length InAlAs/InGaAs metamorphic high electron mobility transistor (mHEMT) technology. The three-stage amplifiers are monolithic microwave integrated circuit (MMIC) chips manufactured in coplanar technology. At cryogenic temperature the first MMIC amplifier achieved a linear gain of 22 dB and an average noise temperature of 11.6 K with a power dissipation of 41 mW. The second MMIC amplifier, with external input matching network, exhibited a gain of 26 dB, and an excellent average noise temperature of 8.1 K with a power dissipation of 12 mW. Both LNA units demonstrate broad bandwidth, high gain, low noise temperature, and compact chip size. The results obtained prove that mHEMT technology is suitable for applications in large instantaneous bandwidth cryogenic receivers for radio astronomy applications.

EMCOR is a heterodyne receiver for the frequency range of 201 to 210 GHz. It has been designed for ground-based measurements of various minor constituents of the stratosphere involved in ozone chemistry. Since the aim was the detection of faint spectral lines, a superconducting tunnel junction has been chosen as mixer element and special care has been taken in developing the calibration unit of the system. The front-end is completed by a quasi-optical system, a solid state local oscillator with electronic tuning and a HEMT pre-amplifier. In the back-end an acousto-optical spectrometer is employed to analyse the signal. A PC controls the whole system. The instrument has been installed at a high mountain site in the Swiss Alps.

We present the results from a monitoring of the $v=1$ and $v=2$, $J=1{-}0$ 28 SiO maser emission in 21 objects, covering all types of known SiO maser emitters: 13 Mira variables, 2 long period semi regu lars (SRGs), 3 variable super giants (SGs), 2 OH/IR stars, and one young stellar object. This study has been carried out with the 13.7 meter radiotelescope of the Centro Astronomico de Yebes (Guadalajara, Spain), from July 1984 to May 1990, and represents the longest and most tightly sampled monitoring of SiO masers ever published. Our data show that for Mira-type (i.e. regular) variables, the SiO and optical light curves agree in period, and that the maxima of the SiO emission lag the optical ones by about 0.1-0.2 periods. Since a similar lag characterizes the near infrared (NIR) emission variability from these stars, we conclude that for regular variables SiO and NIR vary in phase. This result was confirmed in three objects for which NIR variability curves are available. For SRGs and SGs, we found a less systematic behavior, but when the SiO emission is periodic, its variability curve agrees with the optical one, also showing a lag between maximum epochs similar to that of Mira-type stars. The data clearly reveal other interesting details on the SiO maser variability, such as the strong intensity differences between different maxima and changes in the velocity distribution of the emission. Finally, the SiO masers associated to the young stellar object Orion IRc2 showed a double peaked spectrum with low amplitude, aperiodic variations.

The advancement of Radio Astronomy instruments pushes innovation in several fronts. Sensitivity aside, one way in which cryogenic receivers can be upgraded is by increasing the number of beams in single dish antennas, building what is commonly known as a Focal Plane Array (FPA). In this paper we present a novel reduced input reflection 4–12 GHz cryogenic Low Noise Amplifier (LNA) for the Intermediate Frequency (IF) of millimeter wave superheterodyne multipixel receivers with Superconductor-Insulator-Superconductor (SIS) mixers. The aim of this development is to reduce the input reflection of the amplifier to a level at which the bulky cryogenic isolators traditionally used in this type of receivers are no longer necessary and can be avoided. Ultimately this simplification would allow complying with the tight mass and volume restrictions imposed over FPAs. However, the improvement of the input reflection has a cost in terms of noise and gain performance. This effect is critically evaluated by comparing it with other alternative options built with devices of the same technology. The results show that this approach may have advantages in terms of sensitivity of the complete receiver.

MMIC Broadband Low Noise Amplifiers (LNA) for radio astronomy applications with 100 nm GaAs metamorphic High Electron Mobility Transistor (mHEMT) process have been developed. Cryogenic performance of a 4–12 GHz and a 25–34 GHz LNAs is presented. The 4–12 GHz LNA cooled at 15 K exhibits an associated gain of 31.5 dB ± 1.8 dB and average noise temperature of 5.3 K with a low power dissipation of 8 mW. Cooled to 15 K the 25–34 GHz amplifier has demonstrated a flat gain of 24.2 dB ± 0.4 dB with 15.2 K average noise temperature, and a very low power dissipation of 2.8 mW on chip. The mHEMT based LNA MMICs have demonstrated excellent noise characteristics at cryogenic temperatures for their use in radio astronomy applications.

We performed Herschel/HIFI observations of several CO lines in the far-infrared/sub-mm in the protoplanetary nebula CRL618. The high spectral resolution provided by HIFI allows measurement of the line profiles. Since the dynamics and structure of the nebula is well known from mm-wave interferometric maps, it is possible to identify the contributions of the different nebular components (fast bipolar outflows, double shells, compact slow shell) to the line profiles. The observation of these relatively high-energy transitions allows an accurate study of the excitation conditions in these components, particularly in the warm ones, which cannot be properly studied from the low-energy lines. The 12CO J=16-15, 10-9, and 6-5 lines are easily detected in this source. 13CO J=10-9 and 6-5 are also detected. Wide profiles showing spectacular line wings have been found, particularly in 12CO 16-15. Other lines observed simultaneously with CO are also shown. Our analysis of the CO high-J transitions, when compared with the existing models, confirms the very low expansion velocity of the central, dense component, which probably indicates that the shells ejected during the last AGB phases were driven by radiation pressure under a regime of maximum transfer of momentum. No contribution of the diffuse halo found from mm-wave data is identified in our spectra, because of its low temperature. We find that the fast bipolar outflow is quite hot, much hotter than previously estimated; for instance, gas flowing at 100 km/s must have a temperature higher than ~ 200 K. Probably, this very fast outflow, with a kinematic age < 100 yr, has been accelerated by a shock and has not yet cooled down. The double empty shell found from mm-wave mapping must also be relatively hot, in agreement with the previous estimate., 5 pages, 4 figures

Modern ultra low noise receivers used for Radio astronomy have evolved to provide very wide instantaneous bandwidth. Some of the configurations used in present cryogenic Front Ends, like sideband separating mixers and balanced amplifiers need 90° hybrids at the IF, typically in the 4–12GHz band. There are devices commercially available covering this band with good ambient temperature characteristics, but their cryogenic performance drops to unacceptable levels. This paper describes the design, construction and measurement of a multioctave stripline hybrid for the 4–12GHz band specially conceived to survive and perform well when cooled to 19K (−254°C). The materials and mechanical construction have been carefully selected and the result is a very compact, reliable and low thermal mass device, able to survive extreme thermal cycling. The coupling and reflection show very low temperature dependence. The comparison of the results of a typical commercial unit with the new design presented clearly shows its advantages at cryogenic temperature.

Applications like radio astronomy and space communications require ultimate sensitivity and make use of very particular receivers with state-of-the-art devices. Usually the receivers are cooled at cryogenic temperatures to reduce the noise even further. Noise temperatures of only a few times the quantum limit can be obtained in these conditions. During the past decade, Indium Phosphide HEMTs have demonstrated the best noise performance at cryogenic temperatures in the microwave frequency range of all active semiconductor devices, together with extremely low power consumption. For certain applications noise is not the only factor affecting the sensitivity. For example, gain fluctuations may play a dominant role in wide band radiometers. Unfortunately some of the factors that have contributed to improve the noise temperature have degraded the gain fluctuations. The operation at cryogenic temperatures also increases the fluctuations. This paper describes the experimental results obtained at the Centro Astronomico de Yebes (CAY) in the development of wide band cryogenic amplifiers. Special attention is paid to the influence of the bias point in noise and gain fluctuations. InP HEMTs from different foundries were tested. The amplifiers developed will be used in the Herschel ESA mission radiometers and the Atacama Large Millimeter Array (ALMA) receivers.

The sub-millimeter radiometers of the Herschel mission have very stringent requirements. The scientific goals require an instantaneous bandwidth of four GHz with very low noise, flat gain and low power dissipation. Short-term gain stability of the amplifier is important, because gain fluctuations could limit the sensitivity of the instrument. Besides, a highly reliable, low weight unit is required to be compatible with the space instrumentation standards. The amplifiers will be used in conjunction with HEB and SIS mixers in all 7 channels of the instrument. This paper describes the design, the special construction techniques and the results of the amplifiers built by Centro Astronomico de Yebes for the development model of the Herschel Heterodyne Instrument. The average noise temperature obtained in the 4-8 GHz band is 3.5 K, with a gain of 27 ±1.1 dB at an ambient temperature of 15 K and keeping the total power dissipation below the allowed 4 mW. Normalized gain fluctuations were carefully measured, being lower than 1.5·10 -4 Hz -1/2 @ 1 Hz. Space qualification of the design is in progress.

The Heterodyne Instrument for FIRST (HIFI) is a heterodyne receiver system which has an intermediate frequency (IF) amplifier that will likely exhibit 1/f-type gain fluctuations.

The objective of the European project EMCOR was the development of a heterodyne receiver for the frequency range of 201 to 210 GHz for the measurement of the amounts of various minor constituents of the stratosphere involved in ozone chemistry. In order to be able to measure even very faint spectral lines a superconducting tunnel junction has been chosen as mixer element. Additionally, special care has been taken in developing the calibration unit of the system. Besides the classical hot-cold calibration three different balancing methods can be employed: a beam-switch technique with an atmospheric reference signal, a beam switch technique with a reference signal from a variable reference load or a frequency switch technique. The system has been integrated and is currently under testing. It will be installed at the International Scientific Station Jungfraujoch in he Swiss Alps and operated within the framework of the European Alpine stations of the Network for the Detection of Stratospheric Change.

The design, fabrication and measurement of a HEMT's, ultra-low noise, microwave, cryogenically-coolable amplifier is described. The design band covers from 2.1 to 2.5 Ghz and average noise temperature under 2.5k and gain over 25 dB have been measured for a two stage amplifier when cooled under 12.5k. Microwave Design System from HP and Pospieszalski HEMT's noise model have been used to do the design and excellent agreement has been verified between theoretical model and measured parameters. The amplifier has been done to work as an RF fist stage of a radio-astronomy receiver.

A design technique for very broadband, low-noise amplifiers is described. It is based on a wideband noise model of a MODFET. The computer-aided design and realization of L-, K-, and K alpha -band and wideband 8-18-GHz cryogenically coolable amplifiers with optimal noise performance are described. The uniqueness of the results presented rests in the demonstration that a single frequency measurement of noise parameters provides sufficient information for the design of a number of wideband amplifiers in the 1-40-GHz range. >

Cyanogen (NCCN) is the simplest member of the series of dicyanopolyynes. It has been hypothesized that this family of molecules can be important constituents of interstellar and circumstellar media, although the lack of a permanent electric dipole moment prevents its detection through radioastronomical techniques. Here we present the first solid evidence of the presence of cyanogen in interstellar clouds by detection of its protonated form toward the cold dark clouds TMC-1 and L483. Protonated cyanogen (NCCNH+) has been identified through the J = 5−4 and J = 10−9 rotational transitions using the 40 m radiotelescope of Yebes and the IRAM 30 m telescope. We derive beam-averaged column densities for NCCNH+ of (8.6 ± 4.4) × 1010 cm-2 in TMC-1 and (3.9 ± 1.8) × 1010 cm-2 in L483, which translate into fairly low fractional abundances relative to H2, in the range (1–10) × 10-12. The chemistry of protonated molecules in dark clouds is discussed, and it is found that, in general terms, the abundance ratio between the protonated and non-protonated forms of a molecule increases with increasing proton affinity. Our chemical model predicts an abundance ratio NCCNH+/NCCN of ~10-4, which implies that the abundance of cyanogen in dark clouds could be as high as (1–10) × 10-8 relative to H2, i.e., comparable to that of other abundant nitriles such as HCN, HNC, and HC3N., M.A. and J.C. acknowledge funding support from the European Research Council (ERC Grant 610256: NANOCOSMOS) and from Spanish MINECO through grants CSD2009-00038, AYA2009-07304, and AYA2012-32032. Authors from Yebes Observatory acknowledge funding by MINECO through grant FIS2012-32096. E.R. and M.G. acknowledge funding support from the CNRS program “Physique et Chimie du Milieu Interstellaire” (PCMI).