How did black holes shape the cosmos? Fast and quiet X-ray sensors may provide the answer

PROJECT

Ultra-low noise, high frame rate X-ray image sensors for strategic astrophysics missions

INSTANTANEOUS

The new imaging technology will allow future large X-ray telescopes to trace the origin and growth of black holes and how they shaped the cosmos.

Advanced X-ray sensors are fabricated at MIT Lincoln Laboratory’s Microelectronics Lab, which is equipped with the full suite of semiconductor processing equipment needed to build X-ray sensors. Left: A technician loads a reticle (a kind of optical plane) in the 193nm lithography tool used in the sensor production process. Right: 200 mm (8 inch) diameter silicon wafers entering an oven. (Image credit: MIT Lincoln Laboratory)

How did our universe of galaxies and stars come to this? Major NASA observatories, including the Chandra X-ray Observatory and the Hubble Space Telescope, have revealed that the interaction between galaxies and the huge black holes they host is key to answering this question, but the The precise functioning of this interaction remains a mystery. For example, how could black holes a billion times the mass of the Sun grow bigger so soon after the big bang? How do black holes seemingly grow in phase with their host galaxies? How do black holes control star formation over distances billions of times their own size?

Just as today’s large observatories have helped raise these questions, a new generation of facilities – including X-ray telescopes with much larger collection areas and much faster and more sensitive imaging sensors – are needed. to answer. NASA has been developing technologies to enable these advances over the past decade.

Black background with small scattered dots colored in white, light pink, blue and red.
The deepest x-ray image ever produced, obtained by NASA’s Chandra X-ray Observatory. The central region of the image contains the highest concentration of black holes ever seen. Chandra and Hubble images of this region of sky, now known as the Chandra Deep Field-South, have revolutionized our understanding of black hole growth in the early Universe. Next-generation X-ray observatories will probe even deeper into the early Universe. (Image credit: NASA/Chandra X-ray Center/Penn State/B. Luo et al.)

X-rays are emitted by nearly every object in the cosmos, from planets and stars to galaxies and the giant black holes they host. X-ray astronomy is particularly important for understanding the latter since the matter closest to a black hole is a powerful source of X-rays. X-ray photons carry a thousand times more energy than photons of light ordinary as we can see, so specially developed X-ray sensors are needed to record them. These sensors can not only capture X-ray photons but also measure their energies (analogous to the colors of visible light).

Next-generation X-ray telescopes will collect photons 10 to 30 times faster than those currently operating in space. To take full advantage of this capability, sensors at these observatories must at a minimum be able to register and process individual photons at proportionally faster speeds. Even faster sensors are desirable because they would give a clearer picture of time-changing X-ray sources. In addition, new observatories must characterize fainter and more distant cosmic X-ray sources than any we have observed so far. Photons from these sources will appear to have proportionally lower energies (analogous to redder colors), due to the expansion of the universe, so detecting and measuring the energies of these photons requires sensors with a exquisite sensitivity and very low internal noise. Finally, these advanced capabilities must meet the strict constraints of size, mass and power consumption imposed on spaceflight instruments.

To meet these challenges, a team of researchers from the Massachusetts Institute of Technology (MIT) Kavli Institute (MKI) for Astrophysics and Space Research, MIT Lincoln Laboratory and Stanford University Kavli Institute of Particle Astrophysics and Cosmology relies on nearly forty years of NASA investment in the development and operation of X-ray sensitive charge-coupled devices, and application of the latest developments in microfabrication and microelectronics technologies to achieve the required performance gains. Their goals are to increase sensor speed by a factor of 100 and reduce noise by a factor of three while keeping power consumption at about the same level required by current technology.

Two photos side by side.  Left photo: A man and a woman wearing blue lab coats and hairnets work on a sensor in a small metal box.  Right side: a man in a red shirt is sitting at a table and working on a pickup amplifier
Left: Michelle Gabutti and Andrew Malonis verify the installation of a prototype X-ray sensor in a vacuum test apparatus at the MIT Kavli Institute. Right: Tanmoy Chattopadhyay tests an advanced sensor amplifier at Stanford University. (Image credits: Left: G. Furesz, MIT Kavli Institute for Astrophysics and Space Research; Right: LA White, Kavli Institute for Particle Astrophysics & Cosmology, Stanford University)

Three technical innovations put these goals within reach. First, new sensor amplifier structures that operate with low noise at much higher speed than Chandra’s have been demonstrated in the lab, and architectures with even lower noise potential are being developed. test. Second, advances in the processes used to construct X-ray sensors allow for lower operating voltages and thus enable low-power operation. Finally, the team is developing application-specific integrated circuits (ASICs) to provide fast, low-noise analog signal processing tailored to the characteristics of the sensor amplifier using a fraction of the power required by the electronics. discrete treatment.

MKI researchers have tested prototype sensors designed and manufactured at MIT Lincoln Laboratory that demonstrate noise levels better than X-ray sensors on Chandra (less than 3 electrons in each image pixel) – while operating 20 times faster and without an increase in power per unit of detection area. Stanford team members designed an 8-channel ASIC with a projected noise contribution of just over one electron per pixel and data rates per channel of up to 5 million pixels per second. By combining these developments, it becomes possible to design and build X-ray sensors capable of high-speed, low-noise imaging at rates 100 times faster than those of Chandra.

Close-up photo of a green and gold image sensor with numbers and text on it.
An advanced X-ray image sensor (dark brown rectangle, surrounded by a gold frame) mounted on a test circuit board (green). The 2-megapixel sensor has eight output ports. The eight-channel ASIC can be mounted on the board halfway along the right edge of the sensor. (Image credit: MIT Lincoln Laboratory)

According to Dr. Bautz, “We have been privileged to work with NASA’s SMD Astrophysics Division and MIT’s Lincoln Laboratory to develop and deploy imaging technology for a number of successful astrophysical missions, and to have participated in the scientific research that these missions have enabled. This project is perhaps our most ambitious sensor development to date, and we are excited to help achieve even more ambitious X-ray missions.

NASA’s Astrophysics Division has been investing in the rapid development of X-ray imaging sensors since the mid-2000s. The technologies described here are under investigation for a future X-ray probe and flagship X-ray observatory later X, and potentially other future missions.

PROJECT LEADERS

Dr. Marshall Bautz, MIT Kavli Institute (Principal Investigator); Dr. Christopher Leitz, MIT Lincoln Laboratory (co-principal investigator); Teacher. Steven Allen, Stanford University (co-principal investigator).

SPONSORING ORGANIZATIONS

Astrophysics Strategic Technology (SAT) Program of NASA’s Astrophysics Division, with additional support from the MIT Kavli Institute for Astrophysics and Space Research, the Stanford Kavli Institute for Particle Astrophysics and Cosmology, and the Under Secretary for Defense for research and engineering.

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