R. Morse

The AMANDA neutrino telescope: principle of operation and first results

AMANDA is a high-energy neutrino telescope presently under construction at the geographical South Pole. In the Antarctic summer 1995/96, an array of 80 optical modules (OMs) arranged on 4 strings (AMANDA-B4) was deployed at depths between 1.5 and 2 km. In this paper we describe the design and performance of the AMANDA-B4 prototype, based on data collected between February and November 1996. Monte Carlo simulations of the detector response to down-going atmospheric muon tracks show that the global behavior of the detector is understood. We describe the data analysis method and present first results on atmospheric muon reconstruction and separation of neutrino candidates. The AMANDA array was upgraded with 216 OMs on 6 new strings in 1996/97 (AMANDA-B10), and 122 additional OMs on 3 strings in 1997/98.

Optical properties of the South pole ice at depths between 0.8 and 1 kilometer.

The optical properties of the ice at the geographical South Pole have been investigated at depths between 0.8 and 1 kilometer. The absorption and scattering lengths of visible light (∼515 nanometers) have been measured in situ with the use of the laser calibration setup of the Antarctic Muon and Neutrino Detector Array (AMANDA) neutrino detector. The ice is intrinsically extremely transparent. The measured absorption length is 59 � 3 meters, comparable with the quality of the ultrapure water used in the Irvine-Michigan-Brookhaven and Kamiokande proton-decay and neutrino experiments and more than twice as long as the best value reported for laboratory ice. Because of a residual density of air bubbles at these depths, the trajectories of photons in the medium are randomized. If the bubbles are assumed to be smooth and spherical, the average distance between collisions at a depth of 1 kilometer is about 25 centimeters. The measured inverse scattering length on bubbles decreases linearly with increasing depth in the volume of ice investigated.

Performance of two Askaryan Radio Array stations and first results in the search for ultrahigh energy neutrinos

Ultrahigh energy neutrinos are interesting messenger particles since, if detected, they can transmit exclusive information about ultrahigh energy processes in the Universe. These particles, with energies above 1016 eV, interact very rarely. Therefore, detectors that instrument several gigatons of matter are needed to discover them. The ARA detector is currently being constructed at the South Pole. It is designed to use the Askaryan effect, the emission of radio waves from neutrino-induced cascades in the South Pole ice, to detect neutrino interactions at very high energies. With antennas distributed among 37 widely separated stations in the ice, such interactions can be observed in a volume of several hundred cubic kilometers. Currently three deep ARA stations are deployed in the ice, of which two have been taking data since the beginning of 2013. In this article, the ARA detector “as built” and calibrations are described. Data reduction methods used to distinguish the rare radio signals from overwhelming backgrounds of thermal and anthropogenic origin are presented. Using data from only two stations over a short exposure time of 10 months, a neutrino flux limit of 1.5 × 10−6 GeV=cm2=s=sr is calculated for a particle energy of 1018 eV, which offers promise for the full ARA detector.

The AMANDA neutrino telescope

We present new results from the Antarctic Muon And Neutrino Detector Array (AMANDA), located at the South Pole in Antarctica. AMANDA-II, commissioned in 2000, is a multipurpose high energy neutrino telescope with a broad physics and astrophysics scope. We summarize the results from searches for a variety of sources of ultra-high energy neutrinos: TeV-PeV diffuse sources by measuring either muon tracks or cascades, neutrinos in excess of PeV by searching for muons traveling in the down-going direction, point sources, neutrinos originating from GRBs, and dark matter in the center of the Earth or Sun.

The Haleakala gamma ray observatory

A 10 m2 multi-mirror telescope for observing Cherenkov light signals from atmospheric cascades is now operating at Mount Haleakala, Maui, Hawaii. It differs from other atmospheric Cherenkov detectors in accepting pulses that originate from single photoelectrons, employing two sets of 18 optically independent phototubes in a logic system with nanosecond time resolution to reject ambient light from the night sky. With an angular aperture of 1.3 × 10−4 sr, cosmic ray showers are observed at a rate of ∼ 0.5 hz at the zenith, with nearly complete rejection of ambient light. This rate for hadronic showers implies an effective threshold near 100 GeV for electromagnetic showers. Two regions of the sky, one centered on the source and the other separated by from it by 3.6° are simultaneously monitored. Examples of observations of episodic and periodic (pulsar) sources are given.

The Haleakala Gamma Observatory

The Haleakala Gamma Observatory is a 10m2 multi-mirror telescope for observing Cherenkov light from electromagnetic cascades in the atmosphere. It is situated at an altitude of 2950 meters at 20.7°N, 156°W on Mount Haleakala, Maui, Hawaii. It differs from most Cherenkov devices in accepting single photoelectron pulses. It employs two sets of 18 phototubes observing seperate regions of the sky to continuously monitor hadronic background. Hardware coincidence resolution is 10ns, and digital filtering can reduce this substantially, effectively eliminating random signals from ambient light. Events are timed to within ±2μs of UTC by a Cesium beam atomic clock. Hadronic showers are observed at rates of 0.5 to 0.7 Hz, implying a threshold for gamma-induced showers of about 200 GeV.

Status of the AMANDA experiment

Abstract The AMANDA high energy neutrino telescope has successfully been increased in size from four detector strings to ten detector springs during the 1996/1997 season. The first upward going muon-neutrino candidates have been reconstructed from the 1996 years four-string data. Three new detector strings will be deployed during 1997/1998 to 2350 metres depth.

Amanda South Pole neutrino detector

High energy neutrino radiation provides us with a tomographic tool to scan the Universe. Sites shielded by a few hundred grams of matter are not revealed by light, whatever its wavelength. High energy neutrinos are decay products of pions and therefore are a signature of the most energetic cosmic processes. It is proposed to instrument the polar ice cap as a low‐noise particle detector sensing the Cherenkov light from neutrino‐induced muons. This paper describes the successful operation of a prototype string of optical modules that were deployed on January 17, 1992 at the South Pole. The advantages of the method are intriguing. The ice has good optical transmission and provides a mechanical structure to support the instrument. Ice is a quiet, sterile medium where photomultiplier tubes experience low background counting rates. The low background allows us to develop electronics and triggering schemes that are simple and can be installed at the surface and thus remain accessible after deployment of the PMTs...

Status of the Neutrino Telescope AMANDA: Monopoles and WIMPS

The neutrino telescope AMANDA has been set up at the geographical South Pole as first step to a neutrino telescope of the scale of one cubic kilometer, which is the canonical size for a detector sensitive to neutrinos from Active Galactic Nuclei (AGN), Gamma Ray Bursts (GRB) and Topological Defects (TD). The location and depth in which the detector is installed is given by the requirement to detect neutrinos by the Cherenkov light produced by their reaction products and to keep the background due to atmospheric muons as small as possible. However, a detector optimized for this purpose is also capable to detect the bright Cherenkov light from relativistic Monopoles and neutrino signals from regions with high gravitational potential, where WIMPS are accumulated and possibly annihilate. Both hypothetical particles might contribute to the amount of dark matter. Therefore here a report about the status of the experiment (autumn 2000) and about the status of the search for these particles with the AMANDA B10 sub-detector is given.

VHE GAMMA RAYS FROM CYGNUS X-3

The Haleakala 10 m2 Cherenkov light telescope observed Cyg X-3 for 113 hours during the summer and fall of 1985. A 60-sec. burst of gamma rays was observed during the radio flare of early Oct. at a phase of o BB = 0.74. No evidence for pulsar periodicity was found during the burst. Searches for periodicity outside the burst have not yet produced positive results.