Ladda ner årsbok 2008 (6,5 MB) - Polarforskningssekretariatet

Principal investigator
Per Olof hulth
Department of Physics
Stockholm University
and
AlbaNova University Center
Stockholm
Participants
Olle Endegård
Allan hallgren
Division of Nuclear and Particle
Physics, Uppsala University
henrik Johansson
Anders nilsson
Johan söderberg
Fredrik sörqvist
Jimmy Vinbladh
Department of Physics
Stockholm University
and
AlbaNova University Center
Stockholm
Figure 1
one of the optical modules just started
its journey downwards.
Photo: Fredrik Sörqvist
Figure 2, right
The current IceCube detector comprises
2 400 digital optical modules
installed on 40 strings at a depth of
1.5 to 2.5 km in the Antarctic ice.
IceCube – searching for
extraterrestrial neutrinos
casting light in the
antarctic ice
Passing over the Transantarctic Mountains
in a Hercules cargo compartment, a balmy
feeling of experiencing something unique,
almost surreal, stole up on us.
The purpose of IceCube is to detect neutrinos.
Similarly to ordinary telescopes, which detect
photons, cosmological phenomena are studied
to increase our understanding of the Universe.
Extraterrestrial neutrinos are produced in
connection with energetic events such as
supernovae. The neutrino is an elementary
particle that rarely interacts with the surrounding
medium. As a consequence it can travel
vast distances unimpeded, as well as from the
interior of extremely energetic cosmological
objects. The capability of observing neutrinos
opens a new window on the Universe and
one hopes to find answers to fundamental
questions within astrophysics and cosmology.
Among these are the origin of cosmic rays, the
nature of dark matter, and the physics behind
the most luminous objects in the Universe,
gamma-ray bursts and active galactic nuclei.
The fact that neutrinos rarely interact
with the surrounding medium makes them
difficult to detect. When a neutrino does
interact, a very energetic charged particle
is often produced. Traversing the medium,
this particle will emit so-called Cherenkov
radiation. If the medium is transparent this
radiation can be detected, which is the principle
behind indirect detection of neutrinos
in IceCube.
22 FoRSKARRAPPoRTER CRUISE REPoRTS SWEDARP 2007/08
Building a gigantic detector
The construction of IceCube was commenced
in 2004, and construction of its predecessor,
AMANDA, which is now a part of IceCube, in
1993. The current IceCube detector comprises
2 400 digital optical modules installed on
40 strings at a depth of 1.5 to 2.5 km in the
Antarctic ice. Each module contains a 25 cm
photomultiplier tube and is extremely sensitive
to photons. The Antarctic ice is the cleanest
ice on Earth and the dark surroundings make
it possible to detect very faint light. Because
neutrinos interact so rarely a huge detector
volume is required. At the completion of
IceCube, which is planned for the austral
summer of 2010–2011, the detector volume
will have reached 1 km3 .