The idea of ALMA Band-4+5 receivers are proposed for the upgrade after 2030. The new receiver will cover the RF frequency of the original Band-4 and Band-5 with continuous frequency tuning over 125 –211 GHz with dual polarizations, dual sidebands capability. The instantaneous intermediate frequency (IF) bandwidth is up to 16 GHz per sideband and per polarization. Both the SIS-based receiver and HEMT-based receiver schemes are considered. For the SIS receiver scheme, the niobium-based SIS junctions will be fabricated to form mixer chips, and integrated into the mixer blocks with broadband waveguide 3-dB quadrature hybrid couplers with LO couplers, cryogenic IF low-noise amplifiers, and 2-20 GHz coaxial 3-dB quadrature hybrid couplers to form sideband separating down-converters. The inputs of the sideband separating down-converters are fed by the ellipsoidal mirror pairs, corrugated feedhorn and the orthomode transducer. For the HEMT-based receiver scheme, using the same optics configuration as the SIS-based receiver, the cryogenic InP HEMT low-noise amplifiers (LNAs) chains cover 125 – 211 GHz operated in 15-K ambient temperature will be the key components of the cold cartridge assembly (CCA). For the warm cartridge assembly, a pair of sideband-separating diode or resistive transistor mixers will provide four-channel 16-GHz IF instantaneous bandwidth. To avoid the possible interference between LO and IF signals, considering the possible 16 GHz IF bandwidth over 4 – 20 GHz, the LO fundamental frequency will be chosen in 24 - 32 GHz, followed by an active frequency tripler to form the phase-lock loop with 72 – 96 GHz frequency tuning range. The key components with 51.2% relative bandwidth to be developed in-house are Nb SIS mixers, RF InP HEMT LNAs, 3-dB waveguide hybrid couplers, orthomode transducers, corrugated horn antenna, and optics mirror pairs.
The Atacama Large Millimeter/submillimeter Array (ALMA) is the largest (sub)mm-wavelength ground-based telescope and has been producing ground-breaking science since it became operational in 2011. The ALMA Development Roadmap was released in 2018 to prioritize the developments necessary to significantly expand ALMA’s capabilities and enhance its scientific reach in the coming decades. The ALMA2030 Wideband Sensitivity Upgrade (WSU) is the top priority initiative for the Development Roadmap. The WSU will initially double, and eventually quadruple, ALMA’s system instantaneous bandwidth and deliver improved sensitivity by upgrading the receivers, digital electronics, and correlator. The WSU will afford significant improvements for every future ALMA observation, whether it is focused on continuum or spectral line science. The improved sensitivity and spectral tuning grasp will open exciting new avenues of science capability, increase sample sizes, and enable more efficient observations.
The WSU is now well underway with key subsystems under development, including new receivers, digitizers, data transmission system and correlator. In parallel, the observatory is advancing the detailed planning towards implementation through a careful project management and systems engineering approach, based on an integrated Conceptual System Design which outlines the hardware, computing and science operations aspects of the upgrade. The substantial gains in the observing efficiency enabled by the WSU will further enhance ALMA as the world leading facility for millimeter/submillimeter astronomy.
The Atacama Large Millimetre/submillimetre Array (ALMA) is the world’s largest ground-based facility for observations at millimeter/submillimeter wavelengths. Inaugurated in March 2013, ALMA has already accomplished ten years of continued steady-state operations. It comprises 66 antennas located approximately 5000 meters at the Chajnantor Plateau in the Atacama Desert in Northern Chile. The ALMA partnership established the ALMA 2030 development program to improve ALMA’s capability to avoid obsolescence for the next decade. The Wideband Sensitivity Upgrade (WSU) project, the first initiative of the ALMA 2030 development program, will replace the entire digital processing system, which includes the wideband digitizers, data transmission system, and data correlation system. A working group was charged to develop a WSU Deployment Concept based on a parallel deployment approach to minimize scientific downtime during the upgrade period, which could last up to five years. In this paper, the authors present the relevant aspects of this analysis and conclusions, which will pave the road to address the definition of the AIVC concept and the corresponding AIVC plan of the WSU project.
KEYWORDS: Receivers, Optical amplifiers, Radio astronomy, Antennas, Astronomy, Observatories, Cryogenics, Simulation of CCA and DLA aggregates, Roads, Galactic astronomy
The Atacama large millimeter/submillimeter array (ALMA) band-1 receiver covers the frequency band between 35-50 GHz. An extension of up to 52 GHz is on a best-effort basis. Covering the longest wavelengths visible with ALMA, this receiver is enabling studies of dust grain evolution in proto-planetary systems probing dust grain sizes close to 1 cm, and with multiple red-shifted molecular lines it will open up a new window in the high-redshift universe. The band-1 project has recently achieved first light and with this passed a major project milestone. We present the challenges, from initial development to prototype, to establishing the infrastructure, integration, and evaluation of 73 production receiver units, and to the final tasks to complete the project. We conclude with the initial performance and characterization of the first band-1 receivers installed on ALMA.
We present the results of a digital calibration technique applied to an Atacama Large Millimeter/submillimeter Array sideband separating wideband astronomical receiver of 275 to 500 GHz radio frequency (RF) and 3 to 22 GHz intermediate frequency bandwidth. The calibration technique consists of computing the magnitude ratio and the phase difference of the receiver output, and then applying correction constants to the digitized signals. Two analog-digital converters are used to digitize the signals and an field-programmable gate array for the processing. No modification in the analog receiver is required to apply the calibration, as it works directly on upper sideband/lower sideband signals. The technique improved the receiver temperature compared with the double sideband case by increasing the sideband rejection ratio by around 30 dB on average. It is shown that even more rejection can be obtained with more careful control of the RF calibration input power.
The 1.85-m mm-submm telescope has been operated at Nobeyama Radio Observatory to observe molecular clouds in the nearby Galactic Plane based on the molecular lines of 12CO, 13CO, C18O(J = 2–1). We are planning to relocate the telescope to a site (∼2,500 m) at the Atacama Desert in Chile and to newly install a dual-band receiver for simultaneous observations of lines of CO isotopes with the transitions of J = 2–1 and J = 3–2. In order to achieve this goal, we have developed a wideband diplexer to separate radio frequency (RF) 211–275 GHz (ALMA Band 6) and 275–373 GHz (ALMA Band 7). We adopted a waveguide type FrequencySeparation Filters (FSF) as the basic concept of the wideband diplexer in 210–375 GHz. The wideband diplexer (α) has already been fabricated and measured as the prototype, and we thus obtained reasonable performance in the CO lines band. On the other hand, the measurement result indicates the return loss is relatively worse in 280–300 GHz, although it doesn’t affect the simultaneous observations of 230 GHz and 345 GHz band. We carried out 3D shape measurement with an optical microscope, and then, found that there are machining errors in the parts of the resonator in High Pass Filter. The analysis based on electromagnetic simulation reveals that the errors significantly affect return loss around cut-off frequency. In this paper, we describes the design of the waveguide diplexer, S-parameter measurement, and detailed analysis to verify the discrepancy between simulation and measurement.
Currently, we are performing a large-scale survey of molecular clouds toward the Galactic Plane in 12CO, 13CO, and C18O(J = 2–1) with the 1.85-m mm-submm telescope from Nobeyama Radio Observatory. In addition, we are proceeding with the preparation of a new project to observe several additional molecular lines including higher transitions of CO isotopes, such as 12CO, 13CO, and C18O(J = 2–1, 3–2) simultaneously with a wideband receiver (210–375 GHz). The optics has a Cassegrain reflector antenna with Nasmyth beam-waveguide feed and is composed of Main-reflector, Sub-reflector, ellipsoidal mirrors, and plane mirrors. New wideband optics will be required to achieve this goal. In order to accomplish the optics, we have designed a corrugated horn with a fractional bandwidth of ∼56 %, and frequency independent optics to couple the beam from the telescope onto the horn. The corrugated horn has a conical profile and the variable corrugation depth. It has been optimized by using CHAMP, our targeting return loss of better than −20 dB, cross-polarization loss of better than −25 dB, and far-field good radiation pattern. The simulation of the corrugated horn results in low return loss, low crosspolarization, and symmetric beam pattern in that frequency band. The simulated aperture efficiency of the designed receiver optics on the 1.85-m telescope is above 0.76 at all frequencies by using GRASP. Recently, we have succeeded in simultaneous observation of 12CO, 13CO, and C18O(J = 2–1 and 3–2) toward Orion KL with the optics for the first time.
In recent years, NAOJ has contributed designs and production of waveguide and optics components for ALMA bands 1 (35-50 GHz) and 2 (67-116 GHz) receivers. This includes several novel ideas in the design of corrugated horns and OMTs and the application of 3D printing for the fabrication of key components of radio receivers. These frequency bands coincide approximately with bands 5 and 6 of ngVLA, the most promising project in the 2020s to exploit synergies with ALMA with the goal of increasing the scientific output of both facilities. This paper reports on the recent ALMA development results and discusses their future application to ngVLA.
The ALMA telescope has been producing ground-breaking science since 2011, but it is mostly based on technology from the 2000s. In order to keep ALMA competitive in the coming decade, timely updates are necessary in order to further improve the science output of the telescope in the coming decades. In this contribution, we will present the status of the different projects and studies which constitute the contribution of East Asia to the ALMA Development Program, such as the production of band 1 receivers, the development of band 2 receivers optics, and of the ACA spectrometer. We will also update on the different hardware and software studies towards the implementation of the ALMA Development Roadmap and additional opportunities.
NAOJ have studied wideband receiver technologies at submillimeter wavelengths toward implementation as future upgrades into the Atacama Large Millimeter/submillimeter Array telescope. We have developed critical components and devices such as waveguide components and superconductor-insulator-superconductor (SIS) mixers targeting radio frequencies (RF) in the 275-500 GHz range and an intermediate frequency (IF) bandwidth of 3-22 GHz. Based on the developed components, quantum-limited low-noise performance has been demonstrated by using a double-sideband receiver frontend in combination with a high-speed digitizer. In addition, a preliminary demonstration of a wideband RF/IF sideband-separating SIS mixer was performed. This paper describes the status of our efforts to develop technology toward wideband receivers for ALMA.
ALMA has already produced many impressive and scientifically compelling results. However, continuous technical upgrades and development are key for ALMA to continue to lead astronomical research through the 2020-2030 decade and beyond. The East Asia ALMA development program consists of the execution of short term projects, and the planning and initial studies for longer term developments that are essential for future upgrades. We present an overview of all these ongoing East Asia ALMA development projects and upgrade studies, which aim to maintain and even increase the outstanding scientific impact of ALMA in the near future and over the coming decades.
The Atacama Large Millimeter/submillimeter Array (ALMA) Band 1 receiver covers the frequency range of 35-50 GHz. An extension of up to 52 GHz is on a best-effort basis. A total of 73 units have to be built in two phases: 8 preproduction and then 65 production units. This paper reports on the assembly, testing, and performance of the preproduction Band 1 receiver. The infrastructure, integration, and evaluation of the fully-assembled Band 1 receiver system will be covered. Finally, a discussion of the technical and managerial challenges encountered for this large number of receivers will be presented.
The ALMA telescope has been producing ground-breaking science since 2011, but it is mostly based on front-end and back-end technology from the 2000s. In order to keep ALMA competitive in the coming decade, timely updates are necessary in order to further improve the science output of the telescope. In NAOJ, we have been doing research leading to technological developments which aim to increase the field-of-view of the telescope, and the RF and instantaneous bandwidth for more efficient and accurate spectral surveys. In this contribution, we will describe the most important technical achievements by our group in recent years.
ALMA has been demonstrating its exceptional capabilities with unprecedented scientific results achieved over the past six years of operation. To keep ALMA as a leading-edge telescope, it is essential to continue technical upgrades and development of new potential. While our future development programs have already achieved remarkable technological breakthroughs at the level of front-end receivers, we are discussing the upgrades of the analog and digital backend and the correlator. We report the required concept design of the interferometric system focused on these sub-systems to realize new science use cases.
The Atacama Large Millimeter/submillimeter Array(ALMA) Band 1 receiver covers the 35-50 GHz frequency band. Development of prototype receivers, including the key components and subsystems has been completed and two sets of prototype receivers were fully tested. We will provide an overview of the ALMA Band 1 science goals, and its requirements and design for use on the ALMA. The receiver development status will also be discussed and the infrastructure, integration, evaluation of fully-assembled band 1 receiver system will be covered. Finally, a discussion of the technical and management challenges encountered will be presented.
ALMA is the largest radio astronomical facility in the world providing high sensitivity between 35 and 950 GHz,
divided in 10 bands with fractional bandwidths between 19 and 36%. Having a lifespan of at least 30 years, ALMA
carries out a permanent upgrading plan which, for the receivers, is focused on achieving better sensitivity and larger
bandwidths. As result, an international consortium works on demonstrating a prototype receiver covering currents Bands
2 and 3 (67 to 116 GHz) which corresponds to a fractional bandwidth of 54%. Here we present the preliminary design,
implementation and characterization of suitable refractive optics. Results indicate an excellent performance in good
agreement with simulations.
The ALMA Band-1 receiver front-end prototype cold and warm cartridge assemblies, including the system and key
components for ALMA Band-1 receivers have been developed and two sets of prototype cartridge were fully tested. The
measured aperture efficiency for the cold receiver is above the 80% specification except for a few frequency points.
Based on the cryogenically cooled broadband low-noise amplifiers provided by NRAO, the receiver noise temperature
can be as low as 15 – 32K for pol-0 and 17 – 30K for pol-1. Other key testing items are also measured. The receiver
beam pattern is measured, the results is well fit to the simulation and design. The pointing error extracted from the
measured beam pattern indicates the error is 0.1 degree along azimuth and 0.15 degree along elevation, which is well fit
to the specification (smaller than 0.4 degree). The equivalent hot load temperature for 5% gain compression is 492 -
4583K, which well fit to the specification of 5% with 373K input thermal load. The image band suppression is higher
than 30 dB typically and the worst case is higher than 20 dB for 34GHz RF signal and 38GHz LO signal, which is all
higher than 7 dB required specification. The cross talk between orthogonal polarization is smaller than -85 dB based on
present prototype LO. The amplitude stability is below 2.0 x 10-7 , which is fit to the specification of 4.0 x 10-7 for
timescales in the range of 0.05 s ≤ T ≤ 100 s. The signal path phase stability measured is smaller than 5 fs, which is
smaller than 22 fs for Long term (delay drift) 20 s ≤ T < 300 sec. The IF output phase variation is smaller than 3.5° rms
typically, and the specification is less than 4.5° rms. The measured IF output power level is -28 to -30.5 dBm with 300K
input load. The measured IF output power flatness is less than 5.6 dB for 2GHz window, and 1.3dB for 31MHz window.
The first batch of prototype cartridges will be installed on site for further commissioning on July of 2017.
This paper summarizes the performance of all the 73 ALMA band 10 cartridges in terms of noise performance and/or optical efficiencies compared to the required ALMA specifications. In particular, the measured optical performance is compared with the results of novel statistical Monte Carlo analyses carried out before receiver production. Some of the technical difficulties encountered during production are briefly described. Finally, some of the first light results of the first receivers used in Chile are presented.
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