New Amplifiers Boost Atacama Large Millimeter Array

For decades, scientists have observed the cosmos with radio antennas to visualize the dark, distant regions of the universe. This includes the gas and dust of the interstellar medium, planet-forming disks, and objects that cannot be observed in visible light. In this field, the Atacama Large Millimeter/Submillimeter Array (ALMA) in Chile stands out as one of the world’s most powerful radio telescopes. Using its 66 parabolic antennas, ALMA observes the millimeter and sub-millimeter radiation emitted by cold molecular clouds from which new stars are born.

Each antenna is equipped with high-frequency receivers for ten wavelength ranges, 35 to 50 gigahertz and 787 to 950 GHz, collectively known as Band 1. Thanks to the Fraunhofer Institute for Applied Solid State Physics (IAF) and the Max Planck Institute for Radio Astronomy, ALMA has received an upgrade with the addition of 145 new low-noise amplifiers (LNAs). These amplifiers are part of the facilities’ Band 2 coverage, ranging from 67 to 116 GHz on the electromagnetic spectrum. This additional coverage will allow researchers to study and gain a better understanding of the universe.

In particular, they hope to gain new insights into the “cold interstellar medium”: The dust, gas, radiation, and magnetic fields from which stars are born. In addition, scientists will be able to study planet-forming disks in better detail. Last, but certainly not least, they will be able to study complex organic molecules in nearby galaxies, which are considered precursors to the building blocks of life. In short, these studies will allow astronomers and cosmologists to witness how stars and planetary systems form and evolve, and how the presence of organic molecules can lead to the emergence of life.

Advanced Amplifiers Enhance ALMA Sensitivity

Each LNA includes a series of monolithic microwave integrated circuits (MMICs) developed by Fraunhofer IAF using the semiconducting material indium gallium arsenide. MMICs are based on metamorphic high-electron-mobility transistor technology, a method for creating advanced transistors that are flexible and allow for optimized performance in high-frequency receivers. The addition of LNAs equipped with these circuits will amplify low-noise signals and minimize background noise, dramatically increasing the sensitivity of ALMAs’ receivers.

Fabian Thome, head of the subproject at Fraunhofer IAF, explained in an IAF press release:

The performance of receivers depends largely on the performance of the first high-frequency amplifiers installed in them. Our technology is characterized by an average noise temperature of 22 K, which is unmatched worldwide. With the new LNAs, signals can be amplified more than 300-fold in the first step. “This enables the ALMA receivers to measure millimeter and submillimeter radiation from the depths of the universe much more precisely and obtain better data. We are incredibly proud that our LNA technology is helping us to better understand the origins of stars and entire galaxies.

Both Fraunhofer IAF and the Max Planck Institute for Radio Astronomy were commissioned by the European Southern Observatory to provide the amplifiers. While Fraunhofer IAF was responsible for designing, manufacturing, and testing the MMICs at room temperature, Max Planck was tasked with assembling and qualifying the LNA modules, then testing them in cryogenic conditions. “This is a wonderful recognition of our fantastic collaboration with Fraunhofer IAF, which shows that our amplifiers are not only ‘made in Germany’ but also the best in the world,” said Michael Kramer, executive director at the Max Planck Institute for Radio Astronomy.