Filippini lab is reaching for the stars—by cutting through the roof of Loomis Lab

10/14/2021 12:25:40 PM

Garrett Williams for Illinois Physics

There is a new addition on the roof of Loomis, and it has everything to do with the formation of stars in our universe! The Physics department has installed an elevated hoist system in the Filippini group’s fourth floor lab. This upgrade will support construction of the camera for the Terahertz Intensity Mapper (TIM), a new mission to observe the history of star formation from a balloon high above Antarctica. 

TIM is a multi-institution project led by Illinois Physics and Astronomy Professor Joaquin Vieira. Physics Professor Jeff Filippini leads development of the instrument’s cryogenic system.

The history of star formation is a rich area of research in the fields of cosmology and astrophysics, motivated by quests to understand the growth and evolution of galaxies. A wealth of data has been assembled in the last decade showing a dramatic decrease in the rate of star formation ever since its peak at “cosmic noon,” approximately 8–10 billion years ago. 

TIM will use the emerging technique of intensity mapping to map star formation over the course of 4.5 billion years of cosmic history, spanning this period of peak star formation. To do this, TIM employs a spectroscopic telescope populated with arrays of thousands of superconducting detectors to measure the intensity of various far-infrared spectral lines throughout space and time, at wavelengths inaccessible through Earth’s atmosphere.

The finished high bay in Filippini's lab (Credit: Luke Prunkard)
The finished high bay in Filippini's lab (Credit: Luke Prunkard)

“TIM is a pathfinder for a new way of observing cosmic history,” says Filippini. “Due to the universe’s expansion, a single spectral emission line is observed at a range of different wavelengths, depending on when it was emitted. By mapping a region of the sky in both space and frequency, TIM will provide a unique window onto the assembly of galaxies and will contribute to the development of critical technology for future space observatories.”

Construction of the hoist system in the Filippini lab is an invaluable step towards realizing this monumental effort.

“The hoist gives us a higher lifting point (hook height) to let us manipulate somewhat larger hardware,” explains Filippini. “This will enable us to assemble and commission the TIM flight cryostat, the liquid helium–cooled camera with which TIM will observe the universe.” 

Illinois Physics graduate student Rong Nie is leading the effort to design the ultra-sensitive superconducting detectors.

“The detector is the ‘eye’ or ‘heart’ of the telescope,” explains Nie. “The geometry and other physical properties of the detector array correlate highly with the cryostat, and the performance of the detector will affect things like the signal to noise ratio.” 

Illinois Astronomy graduate student Jianyang “Frank” Fu is leading the development of the system cryostat. 
“The TIM cryostat is the container of the cold optics,” explains Fu. 

The cryostat cools these to the frigid temperature of liquid helium. The detectors themselves are kept yet colder—a mere quarter-degree above absolute zero. 

“The temperature of the cryostat affects the data quality—the signal to noise ratio—while the duration of the cryostat—how long it can remain cold before its liquid helium is exhausted—determines the length of the flight and how much data we can acquire,” Fu continues.

According to Fu, the TIM cryostat is based on a previous instrument that was modified to accommodate the TIM optics. The team has designed the sub-Kelvin refrigerator system to achieve a good operating temperature for the TIM detectors. 

Once TIM takes its data-collecting flight over Antarctica, the work of Fu, Nie, and the rest of the Filippini and Viera research groups in Loomis Lab will contribute to our understanding of the history of the observable universe. And it’s all made possible by the new Filippini Lab crane bay—a vertical extension of the room to create space to lift experimental equipment in and out of the cryostat.

Click here for further reading on the research  happening in the Filippini group.