Skip to comments.Michigan Tech Scientists Design Laser Calibration System for Next-Gen Gamma-Ray Telescope
Posted on 06/08/2013 6:19:55 PM PDT by imardmd1
Super-high-energy galactic gamma rays have trillions of times more energy
than visible light, and they disappear in the atmosphere before they hit
the Earths surface. So if you want to detect these mysterious
phenomena, a regular telescope isnt much help.
To learn about the highest-energy gamma rays, scientists build elaborate
observatories, and one of the most advanced is the new High-Altitude
Water Cherenkov (HAWC) Gamma-Ray Observatory, high in the
mountains about six hours from Mexico City. When its completed, it will
be the only facility in the world that can detect the highest-energy gamma
rays, with energies of up to 100 TeV (trillion electron volts), or tens of
trillions of times more energy than the light we see.
Petra Huentemeyer, an assistant professor of physics at Michigan
Technological University, is part of that effort. Her team is designing the
observatorys laser calibration system in cooperation with researchers
from the University of New Mexico.
Scientists are interested in the highest-energy gamma rays because they hold
clues to the nature of space and time. No one knows for sure where these
rays come from. Perhaps they originated in the Big Bang, or they could be
generated by some of the universes showiest pyrotechnics: supernovae,
huge explosions that occur when massive stars collapse to form neutron
stars, quarks or black holes.
When one of these high-energy gamma rays approaches the Earth, it collides
with molecules in the air, disintegrating and creating an air shower of
other high-energy particles. It is these particles that the scientists actually
track, using big tanks of water called Cherenkov detectors. When its
done, the HAWC Observatory will have 300 of these tanks, each 25 feet
across and 16 feet high.
They are named after Pavel Alekseyevich Cherenkov, who discovered that
light slows down while traveling through matter. It slows down so much
that some particles can actually go faster than light. (In a vacuum, nothing
travels faster than the speed of light.) These ultra-fast particles create a
light cone and a shock wave, the photonic equivalent of a sonic boom.
When particles from gamma-ray air showers pour into the Cherenkov tanks at
the HAWC Gamma-Ray Observatory, they will exceed lights speed limit
in water and create light cones. Photomultipliers in the tank will convert
some of that light to electricitylike a solar panel. That electricity triggers a
laser, which travels through fiber optic cables to the HAWC computers and
signals the presence of a gamma-ray-induced air shower.
When it goes on line in August, HAWC will be one of seven ground-based
gamma-ray observatories in the world. It will not only lead the pack in
detecting the highest-energy gamma rays; its extreme precision will also
give better information on the origins of the gamma rays and their energy.
"Its 15 times more sensitive than the Milagro Gamma-Ray Observatory at
Los Alamos National Lab," said Huentemeyer.
Huentemeyer directs the HAWC team charged with calibrating the equipment
and verifying that the data gathered are correct.
Calibration at the HAWC Observatory is critical, because the science depends
on measurements that must be accurate to within of 10ths of billionths of
a second. That precision is essential because the photomultipliers not
only detect the presence of air showers. They also use the orientation of
those air showers to figure out where the gamma rays come from.
"Think of the air showers like a pancake flying through space," said
Huentemeyer. The "pancake" arrives at the Cherenkov detector and its
array of photomultipliers at an angle.
That means that particles at the bottom edge of the pancake will trigger a
photomultiplier first, and the particles at the top will be detected last. The
time difference between the two strikes can be used to calculate the angle
of the air shower, which can determine where in the sky the gamma ray
"We work on the timing of these hits to the photomultipliers, which are
nanoseconds apart," Huentemeyer said. The electrical signals travel
through 600 feet of fiber optic cable, and the team is responsible for
making sure that everything is calibrated identically.
"A lot of work went into writing the software that allows this work to be remotely
controlled," Huentemeyer said. "We also use software packages written
for the Large Hadron Collider," the worlds largest high-energy particle
HAWC is just beginning its mission, so it hasnt detected evidence of the
highest-energy gamma rays yet, since they are extremely rare. It has
found lower-energy rays, and just to make sure its first detectors were
working properly, the team snapped an image in one place it did not
expect to find gamma rays: in the shadow of the moon.
When its up and running, HAWC is set to pick up gamma rays traveling to
Earth via the edge of the Milky Way galaxy.
"Thats when things will really get interesting," Huentemeyer said.
The HAWC collaboration involves approximately 150 scientists from the Los
Alamos National Laboratorys Neutron Science and Technology and
Subatomic Physics groups, 15 universities in the United States and 15 in
Mexico. Construction is funded by the US Department of Energy Office of
Sciences High Energy Physics program, the National Science Foundation
and Consejo Nacional de Ciencia y Tecnología (Mexicos science funding
Note: The colorful thumbnail graphic that appears on the Michigan Tech news
site is the "shadow" of the Moon, which blocks the arrival of cosmic rays.
Michigan Technological University (www.mtu.edu) is a leading public
research university developing new technologies and preparing students
to create the future for a prosperous and sustainable world. Michigan
Tech offers more than 130 undergraduate and graduate degree programs
in engineering; forest resources; computing; technology; business;
economics; natural, physical and environmental sciences; arts;
humanities; and social sciences.
(EE alum here....)
Possibly the most underrated college in the country (used to be a mining school). Houghton gets as much or more snow than Buffalo, which is a reason why.
Things like this will probably have other applications in industry (Hopefully not surveillance)
The energy content of a proton is about a giga electron volt. Those gamma rays have an energy content 15 thousand times that. Hard to imagine anything that pack that much energy into one particle of light.
Wonder if we could eventually harness all that power for deep space flight, or powering space stations?
Thanks imardmd1. Extra to APoD members.
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