Physics Professor, Students Build Instruments to Study Cosmic Dust
April 27, 2017
When Fiona Breyer ’17 and Lunjun (Simon) Liu ’17 were teenagers looking at the night
sky from their homes on two different continents, astrophysics seemed so exotic and
So the students were a bit nonplussed when their in-the-trenches experiences in astrophysics
began not by looking up, but by drilling down — learning to use a milling machine,
lathe, drill press and other important but rather unsexy pieces of equipment in the
machine shops in the basement of the Center for Natural Science (CNS).
The two are among a half-dozen students contributing to a project led by Associate
Professor of Physics Thushara Perera to design instrumentation that will help scientists learn more about
cosmic dust. Once regarded as a nuisance by astronomers because it absorbs the visible
light from objects, cosmic dust is now recognized for the role it plays in the evolution
of galaxies, stars and planetary systems. Though not yet fully understood, cosmic
dust is also thought to have an integral role in the chemical activity giving rise
to complex molecules, some of which may be the precursors of amino acids, the building
blocks of life.
Over his dozen-plus years in the field, Perera realized there is no one facility in
the world dedicated solely to the study of cosmic dust candidates, or man-made items
mimicking the dust’s chemical and physical properties. At large research facilities,
an apparatus is rigged together for testing such candidates and then taken apart for
other uses, said Perera, leading to systematic errors.
Perera reasoned that a dedicated system for studying cosmic dust — one that utilized
the principles of observational cosmology — would greatly reduce such errors. “The
whole goal of observational cosmology is to reduce systematic errors when you are
looking at the sky,” he added. “So our system is built from a different perspective.”
The National Science Foundation recognized the novelty of this approach and awarded
Perera a grant for the project.
At the project’s center is a spectrometer. Its basic function is to take in light,
break it into its spectral components, send those components through cosmic dust samples,
record the amount of light transmitted through each sample as a function of wavelength,
and display the data through a computer program.
One specific instrument Perera and his students are building is a Fourier Transform
Spectrometer (FTS), which makes use of an innovative concept put forth by Dale Fixsen,
a research scientist with NASA’s Goddard Space Flight Center. “I exchanged about three
emails with Fixsen and we did the rest,” Perera said. When they are finished, Perera
and his students will have constructed the world’s smallest FTS.
What’s most unique about the IWU project is the design — the compact FTS is coupled
to a cryostat. Essentially a very cold refrigerator (indeed, Perera and his students
refer to it as “the fridge”), the cryostat can cool samples to a temperature of 4
Kelvin, or –452 degrees Fahrenheit. The fridge can be used to match the temperatures
of actual astronomical dust clouds (10-50 Kelvin). The structure that holds the fridge,
along with the pumping/vacuum station, were mostly built and installed by Illinois
Wesleyan physics students. So were most of the thermometers, associated cables and
electronics, as well as special insulation within the fridge, which also includes
a bolometer, or millimeter-wavelength light detector. This sensitive instrument measures
While Perera led the way in devising the spectrometer — from working out the mathematical
formula to writing the source code to cut the metal for the ellipsoidal mirrors inside
the spectrometer —his students made major contributions. Showing these components
to a visitor, the professor ticks off some of the many advances made by past and current
Kyle O’Shea ’16 took Perera’s CAD designs for the FTS and machined most of the necessary
parts to high precision using IWU’s milling machine. He also implemented a system
to control the FTS’s moving mirror, and used IWU’s 3D printers to make several items,
including an adapter for the vacuum enclosure of the FTS. O’Shea is now a Ph.D. student
in mechanical engineering at Michigan State University, where he’s working on new
technology for 3D printing.
Hansheng (Jason) Chen ’17 designed a robust optical window for the cryostat, so that
a wide spectral range of light can pass into the fridge without compromising the vacuum
within. After completing the design for the window — which was fabricated at the University
of Illinois — Chen made changes and machined additional parts to help install the
optical window. This fall, he will enter a graduate program in theoretical astrophysics
at the University of California, Davis.
Huy Do ’16 — now completing his 3:2 dual degree in electrical engineering at Washington
University in St. Louis— was an early contributor to the project. Do’s work on the
bolometer electronics and filter wheel mechanics built a foundation for the progress
that has been made on the instrument thus far.
As the lead student on the spectrometer project this past year, Lunjun Liu played
a major role in developing and testing a unique filter wheel housed in the fridge.
This wheel holds and switches dust samples, allowing researchers to study up to eight
different samples in one cooldown. Liu machined shafts, pulleys and dozens of other
mechanical parts in the CNS machine shop, but his first challenge was to learn basic
skills and safety protocols needed to work with the tools.
“I had no experience in any kind of building before coming to IWU,” said Liu, a native
of Wuhan, China. “I was not expecting that would be something that would be necessary
for an astrophysicist.” But as Liu was building the part, testing it, refining it,
and testing it again in a seemingly endless process, he began to understand how important
those routine tasks would be to the final outcome.
Liu believes his “in the trenches” experience in the IWU lab has given him an important
advantage. Last summer he was selected for Caltech’s competitive Summer Undergraduate
Research Fellowship. Because he was familiar with cryostats, detectors and electronics
from his work at Illinois Wesleyan, Liu entered the Caltech lab confident of his abilities.
“At Caltech I observed other students not fully understanding the inner workings of
the equipment, because they are not building things step by step, without understanding
every concept of every device,” said Liu, who is returning to Caltech for a year to
assist with deployment of one of his projects there before entering graduate school
in astronomy at the University of Illinois. “I was able to provide my point of view
to fine-tune a device, for example, to provide a better outcome.”
Getting it Right
“At temperatures this cold, so much can go wrong,” said Ronan Dorsey ’18, who joined
Perera’s lab group in May 2016 and worked through the summer, spending much of that
time machining parts for a “light pipe” within the cryostat that carries light from
the outside to the dust samples inside the fridge.
“The machining can seem menial,” Dorsey admitted, “but it’s so important to take your
time and just do it slow so you get it right. Or, at least, as much as you can before
you test it. And then you go back to the machine shop when you figure out you did
Breyer’s introduction to the FTS project was equally unglamorous. When she joined
the project in her sophomore year, she said her tasks involved screwing parts that
had already been machined onto the body, or applying oil to keep the machining functioning
smoothly. “I had no idea what I was doing at first,” she acknowledged with a laugh.
“It takes a while to really understand the project.”
Soon, however, Perera tasked Breyer with logging the fridge’s temperature and detector
data with LabVIEW, a graphical language used for data acquisition and instrument control.
In the summer of 2015, Breyer worked in Perera’s lab to collect data as the spectrometer
was being calibrated.
“My program would take data points every minute for something like 15 hours, store
it and then we’d review it the next morning,” she said. According to Perera, Breyer
also played a large role in structuring and organizing the inside of the cryostat.
Breyer believes this lab research experience helped her secure a spot for a nationally
competitive National Science Foundation Research Experiences for Undergraduates internship
“Going into the summer research experience at the University of Wisconsin at Madison,
I felt so much more confident about my abilities,” Breyer noted.
“Dr. Perera has always believed in me, even when I didn’t believe in myself, and he’s
made me feel confident in my abilities to do lab work, to be a physicist, and to be
successful,” she added.
Sharing with the World
The chance to work alongside a faculty member, building a device from the ground up
in hopes of learning more about the origins of planetary systems, is not lost on the
“Spending four or five hours a day for a whole summer with Dr. Perera, working one-on-one
on this project, is not something I would find at a big university,” Dorsey observed.
“Working directly with a physicist of Dr. Perera’s caliber has been the most rewarding
thing about this entire project.”
Dorsey has become the ‘go-to guy’ in day-to-day operations the past several months
as Perera and his group have conducted three cooldowns in order to improve the bolometer’s
performance. After a successful cooldown of the cryostat in February, the next step
is to test and troubleshoot the entire system. Construction is scheduled for completion
this summer, when the National Science Foundation grant’s funding cycle comes to a
Perera said that to his knowledge, there has been no other successful operation of
a detector of this kind using a ‘dry’ cooling mechanism that employs gas pulses, rather
than liquid helium, to cool. The only other FTS Perera knows of that’s remotely similar
to the one at Illinois Wesleyan is housed in the lab of a colleague at the University
Despite the daily challenges and troubleshooting necessary to get a new instrument
of such complexity up and running, Perera anticipates the satisfaction of soon being
able to share the IWU group’s work with the world. First up is an academic paper on
the project’s instrumentation, projected for later this year. And he looks forward
to the day — soon, he hopes — when the device is fully functioning in its purpose
to aid astronomers and astrophysicists in the quest to better understand the nature
of cosmic dust.
“There is still much we don’t know about dust-obscured environments,” said Perera.
“But knowing about the properties of the dust tells us how that dust was created,
and that’s a piece of information about how a planetary system evolved or how a new
planetary system was made.”
Perera noted the field of astronomy is currently preoccupied with asking the question
of how life came to be, with the role of cosmic dust explored within that question.
“I can understand that, because as a child in Sri Lanka, my interest in science was
born, in part, that way as well,” he recalled. “Looking at the stars, and wondering
if there was someone looking back from another planet.”
Perera and his students continue asking those questions and pursuing answers, but
stand proud of what they believe their work will add to the growing body of knowledge
for all those who still seek.