The High Resolution Fly's Eye or HiRes detector was an
ultra-high-energy cosmic ray
In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray with an energy greater than 1 EeV (1018 electronvolts, approximately 0.16 joules), far beyond both the rest mass and energies typical of other cosmic ray partic ...
observatory that operated in the western
Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
desert from May 1997 until April 2006. HiRes used the atmospheric
fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
technique that was pioneered by the Utah group first in tests at the
Volcano Ranch experiment
The Volcano Ranch experiment was an array of particle detectors in Volcano Ranch, New Mexico
)
, population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano)
, seat = Santa Fe
, LargestCity = Albuquerque
, LargestMetro ...
and then with the original Fly's Eye experiment.
Hardware and development
The High Resolution Fly's Eye used larger mirrors and smaller pixels as compared with the original Fly's Eye, hence the name. A prototype of the HiRes experiment operated between 1993 and 1996 at the original Fly's Eye-I site (Five Mile Hill). It was configured in a tower viewing a narrow wedge of sky from 3–73 degrees in elevation. First the Utah ground array and later the
CASA and MIA (ground array and muon array) experiments were placed on the surface in the view of the HiRes prototype. This then became the first "hybrid experiment" collecting information both on the development of the
air shower induced by the incident cosmic ray, but also measuring the shower's footprint at the Earth's surface and 3 m below surface (with the buried muon array). The HiRes prototype was disassembled early in 1997 to become part of the final HiRes configuration.
In its final configuration, HiRes was composed of two sites separated by 12.6 km. The sites were located on hilltops in
Dugway Proving Grounds
Dugway Proving Ground (DPG) is a U.S. Army facility established in 1942 to test biological and chemical weapons, located about southwest of Salt Lake City, Utah, United States, and south of the Utah Test and Training Range.
Location
Dugway Pr ...
, a U.S. Army test facility in the west Utah desert. HiRes-I (located on Five Mile Hill or Little Granite Mountain
())
had one ring of 22 telescopes viewing from 3–17 degrees in elevation. HiRes-I was instrumented with sample and hold electronics which took a "snapshot" of the extensive air shower generated when the incident cosmic ray interacted with the atmosphere. Meanwhile, HiRes-II (located on Camel's Back Ridge
())
had two rings of telescopes to provide viewing higher into the atmosphere. It observed from 3 to 31 degrees in elevation.
HiRes-II was instrumented with a
flash analog to digital converter (FADC) so that it essentially made movies of the cosmic ray events. Both observatory sites provided full azimuthal coverage (360 degrees in azimuth). They were operated independently on moonless clear nights. The duty cycle of HiRes was close to 10%.
Accomplishments
The HiRes discovered the
Oh-My-God particle
The Oh-My-God particle was an ultra-high-energy cosmic ray detected on 15 October 1991 by the Fly's Eye camera in Dugway Proving Ground, Utah, U.S. It is the highest-energy cosmic ray ever observed.
This particle's energy was unexpected an ...
, an
ultra-high-energy cosmic ray
In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray with an energy greater than 1 EeV (1018 electronvolts, approximately 0.16 joules), far beyond both the rest mass and energies typical of other cosmic ray partic ...
, on 15 October 1991.
,
The HiRes experiment made the first observation of the
Greisen–Zatsepin–Kuzmin limit
The Greisen–Zatsepin–Kuzmin limit (GZK limit or GZK cutoff) is a theoretical upper limit on the energy of cosmic ray protons traveling from other galaxies through the intergalactic medium to our galaxy. The limit is (50 EeV), or about 8 j ...
(GZK cutoff) which is an indication of the highest energy cosmic rays interacting with the
cosmic microwave background
In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all spac ...
and the universe becoming opaque to their propagation.
In 2010 final results of the HiRes experiment confirmed the GZK cutoff.
A follow-on experiment to the High Resolution Fly's Eye and
Akeno Giant Air Shower Array The Akeno Giant Air Shower Array (AGASA) is a very
large surface array designed to study the origin of ultra-high-energy cosmic rays. Located in the town of Akeno in Yamanashi prefecture, Japan, it covers an area of 100 km2 and consists of 111 ...
(AGASA) experiments is the
Telescope Array Project
The Telescope Array project is an international collaboration involving research and educational institutions in Japan, The United States, Russia, South Korea, and Belgium. The experiment is designed to observe air showers induced by ultra-high- ...
which began data collection in central Utah in 2007. A similar approach, but with the
water-Cherenkov detectors, has been employed for the
Pierre Auger Observatory
The Pierre Auger Observatory is an international cosmic ray observatory in Argentina designed to detect ultra-high-energy cosmic rays: sub-atomic particles traveling nearly at the speed of light and each with energies beyond 1018 eV. In Ear ...
which began collecting data in 2004.
Awards
Dr.
Pierre Sokolsky
Pierre Vsevolod Sokolsky is an American physicist, currently a Distinguished Professor of Physics and Astronomy and Dean Emeritus of the University of Utah College of Science and also a Fellow of the American Physical Society.
Biography
Pierre ...
and Dr. George Cassidy, both of the
University of Utah
The University of Utah (U of U, UofU, or simply The U) is a public research university in Salt Lake City, Utah. It is the flagship institution of the Utah System of Higher Education. The university was established in 1850 as the University of De ...
, received the 2007
Panofsky Prize
The Panofsky Prize in Experimental Particle Physics is an annual prize of the American Physical Society. It is given to recognize and encourage outstanding achievements in experimental particle physics, and is open to scientists of any nation. It w ...
for their work on the HiRes experiment.
See also
*
List of astronomical observatories
This is a list of astronomical observatories ordered by name, along with initial dates of operation (where an accurate date is available) and location. The list also includes a final year of operation for many observatories that are no longer in ...
References
External links
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{{Portal bar, Utah, Astronomy, Stars, Spaceflight, Outer space, Solar System, Education, Science
High energy particle telescopes
Cosmic-ray experiments
University of Utah
Buildings and structures in Tooele County, Utah
Astronomical observatories in Utah