Download Miriam Israelowitz1 and Dr. David L. Wilson2 1Department

A Cherenkov Radiation Detector for
the Auger Project
Katarzyna Oldak
Research Adviser: Corbin Covault
Department of Physics
Abstract
Detector Design
Panel Spacing
The purpose of this project was to put together a durable and low-cost
Cherenkov radiation detector from a non-imaging optical
concentrator and a coincidence system. The goal was to detect
Cherenkov radiation from the atmosphere under clear and dark skies.
The design of the detector consists of a central photomultiplier tube
(PMT) with a Winston-cone optical concentrator used to increase
light collection and to block out ambient light from above the
horizon. Four scintillator panels and a coincidence unit are used to
identify muon showers, which come down simultaneously with
Cherenkov radiation. This project attempts to find an alternate
method of detecting Cherenkov radiation and further the study of the
origin and composition of ultra-high-energy cosmic rays.
N
u
m
b
e
r
Energy
Figure 6. A log-log plot of
the predicted distribution
of air showers detected
by the apparatus.
Figure 3. A schematic of the apparatus.
 A Winston-cone concentrator, designed to only collect light
from within 40º of the zenith, increases the light collecting area
of the PMT as well as keeps out light pollution from city lights.
Figure 1. A projection of the celestial sphere. Active
galactic nuclei are marked by asterisks. Arrival
directions of 27 most energetic cosmic rays detected
by the Pierre Auger Observatory are marked by
circles.
 The material in the scintillator panels reacts with muons and
releases photons, which are in turn detected by a PMT mounted
on each panel. The scintillators are housed in red crab boxes (see
Figure 3) and their signals are put together in a coincidence unit.
Sky Brightness
Background
bright to use this detector?
Tube
High
Voltage
Power
Supply
PMT
Ammeter
As an air shower hits the ground, the spread of the falling
particles depends on the initial energy of the cosmic ray. More
energetic cosmic rays create larger circles on the ground and are
therefore easier to detect. However, more energetic cosmic rays
enter the atmosphere less frequently than slower rays, so their
observed number is smaller.
The spacing of the scintillator panels determines the minimum
energy that can be detected with the apparatus. A 15 m spacing
between panels allows the apparatus to detect showers generated
by cosmic rays with energies of 50-200 TeV.
Future Work
If it is possible to construct a low-cost, durable apparatus that
can detect Cherenkov radiation occuring in the atmosphere, the
Pierre Auger Collaboration may be able to employ such
detectors to collect more data about ultra-high-energy cosmic
rays. In order to reach this goal, more component testing and
design work may need to be done.
Figure 4. A schematic of the apparatus used to measure
sky brightness.
Current/Steradian Drawn by the PMT vs. Angle off Zenith
 Only a small solid
angle of the sky was
exposed to the PMT held
at various angles.
Figure 2. An extensive air shower caused by an ultrahigh-energy cosmic ray entering the atmosphere.
 The goal is to detect single
Cherenkov radiation photons
against the background light from
stars.
 Calculating the total
brightness showed that
the Cleveland sky would
cause a 1.6 mA current.
Since the PMT saturates
at 1.3 mA, Cherenkov
radiation would not be
detected.
1300
MicroAmps/SR
Detecting Cherenkov radiation is a way of obtaining information
about the cosmic rays that enter the Earth’s atmosphere. The
radiation is a bluish glow emitted by particles traveling faster than
the speed of light in a given medium. Ultra-high energy cosmic rays
19
20
(UHECRs) have energies of 10  10 eV and they interact to form
extensive particle showers. The goal of this project is to come up
with a third data collecting method for the Pierre Auger
Collaboration, which is currently employing two different methods
of studying UHECRs. The Collaboration is attempting to identify the
sources and composition of these cosmic rays.
 Is the Cleveland sky too
Figure 7. Scintillator
panels with predicted
shower sizes.
Acknowledgements
I would like to thank my adviser Corbin Covault for all this help and guidance. I also
extend special thanks to Ross Burton for his assistance with this project as well as Joe
Liang for his work on the scintillator panels. I would also like to thank all other
members of the High Energy Astrophysics group at CWRU as well as the Pierre Auger
Collaboration.
1200
1100
References
1000
0.0
0.2
0.4
0.6
0.8
Angle off Zenith (Radians)
Figure 5. Cleveland sky measurements.
 The Pierre Auger Collaboration et al. “Correlation of the Highest-Energy Cosmic Rays with Nearby
Extragalactic Object.” Science. 318, 5852 (9 November 2007) (url:
http://www.sciencemag.org/cgi/content/full/318/5852/938)
 Pierre Auger Observatory. Retrieved April 5, 2009, Web site: http://www.auger.org
 Cendes, Yvette. “The Test and Feasibility of a Cherenkov Detector for the Auger Project.” May 2008.