High Resolution Fly's Eye Cosmic Ray Detector
Encyclopedia
The High Resolution Fly's Eye or HiRes detector was an ultra-high-energy cosmic ray
observatory that operated in the western Utah
desert from May 1997 until April 2006. HiRes utilized the atmospheric fluorescence
technique that was pioneered by the Utah group first in tests at the Volcano Ranch experiment
and then with the original Fly's Eye experiment. Dr. Pierre Sokolsky and Dr. George Cassidy, both of the University of Utah
, received the 2007 Panofsky Prize
for their work on this.
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 1993–1996 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, 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 an FADC (Flash Analog to Digital Converter
) 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%.
The HiRes experiment made the first observation of the GZK cutoff which is an indication of the highest energy cosmic rays interacting with the Cosmic Microwave Background 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 (AGASA) experiments is the Telescope Array Project
which began data collection in central Utah in 2007.
Ultra-high-energy cosmic ray
In astroparticle physics, an ultra-high-energy cosmic ray or extreme-energy cosmic ray is a cosmic ray with an extreme kinetic energy, far beyond both its rest mass and energies typical of other cosmic rays....
observatory that operated in the western Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
desert from May 1997 until April 2006. HiRes utilized the atmospheric fluorescence
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
technique that was pioneered by the Utah group first in tests at the Volcano Ranch experiment
Volcano Ranch experiment
The Volcano Ranch experiment was an array of particle detectors in Volcano Ranch, New Mexico, used to measure ultra-high-energy cosmic rays from 1959 to 1963....
and then with the original Fly's Eye experiment. Dr. Pierre Sokolsky and Dr. George Cassidy, both of the University of Utah
University of Utah
The University of Utah, also known as the U or the U of U, is a public, coeducational research university in Salt Lake City, Utah, United States. The university was established in 1850 as the University of Deseret by the General Assembly of the provisional State of Deseret, making it Utah's oldest...
, received the 2007 Panofsky Prize
Panofsky Prize
The Panofsky Prize is an annual $10,000 prize given to recognize and encourage outstanding achievements in experimental particle physics, and is open to scientists of any nation. It was established in 1985 by friends of Wolfgang K. H...
for their work on this.
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 1993–1996 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
Chicago Air Shower Array
The Chicago Air Shower Array was a very large array of scintillation counters located in Utah, fifty miles southwest of Salt Lake City in Dugway Proving Grounds. CASA began operating in 1992, in coincidence with a second array, the Michigan Anti , under the name CASA-MIA. The array was made of...
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
Air shower (physics)
An air shower is an extensive cascade of ionized particles and electromagnetic radiation produced in the atmosphere when a primary cosmic ray enters the atmosphere...
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, 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 an FADC (Flash Analog to Digital Converter
Flash ADC
A Flash ADC is a type of analog-to-digital converter that uses a linear voltage ladder with a comparator at each "rung" of the ladder to compare the input voltage to successive reference voltages...
) 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%.
The HiRes experiment made the first observation of the GZK cutoff which is an indication of the highest energy cosmic rays interacting with the Cosmic Microwave Background 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 (AGASA) experiments is the Telescope Array Project
Telescope Array Project
The Telescope Array project is an international collaboration involving research and educational institutions in Japan, Taiwan, China, Russia, South Korea, and the United States. The experiment is designed to observe ultra-high-energy cosmic ray air showers using a combination of ground array and...
which began data collection in central Utah in 2007.
External links
- HiRes Fly's Eye — University of Utah
- HiRes Fly's Eye — University of Adelaide
- "The Mystery of Ultra High Energy Cosmic Rays" — a short documentary (WMVWindows Media Video'Windows Media Video is a video compression format for several proprietary codecs developed by Microsoft. The original video format, known as WMV, was originally designed for Internet streaming applications, as a competitor to RealVideo. The other formats, such as WMV Screen and WMV Image, cater...
)