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| 2. |
- Miller, T. C., et al.
(författare)
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Particle astrophysics in antarctica
- 1996
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Ingår i: International School of Cosmic Ray Astrophysics: 10th Course: Toward the Millennium in Astrophysics: Problems and Prospects 16-26 Jun 1996. Erice, Italy. ; , s. 157-166
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Konferensbidrag (refereegranskat)
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| 3. |
- Askebjer, P., et al.
(författare)
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AMANDA : status report from the 1993-94 campaign and optical properties of the South Pole ice
- 1995
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Ingår i: Nuclear physics B, Proceedings supplements. - : Elsevier. - 0920-5632 .- 1873-3832. ; 38:1-3, s. 287-292
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Tidskriftsartikel (refereegranskat)abstract
- We report the first results of the AMANDA detector. During the antarctic summer 1993-94 four strings were deployed between 0.8 an 1 km depth, each equipped with 20 photomultiplier tubes (PMTs). A laser source was used to investigate the optical properties of the ice in situ. We find that the ice is intrinsically extremely transparent. The measured absorption length is 59 ± 3 m, i.e. comparable with the quality of the ultra-pure water used in the IMB and Kamiokande proton-decay and neutrino experiments [1,2] and more than two times longer than the best value reported for laboratory ice [3]. Due to a residual density of air bubbles at these depths, the motion of photons in the medium is randomized. For spherical, smooth bubbles we find that, at 1 km depth, the average distance between collisions is about 25 cm. The measured inverse scattering length on bubbles decreases linearly with increasing depth in the volume of ice investigated. © 1995 Elsevier Science B.V. All rights reserved.
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| 4. |
- ASKEBJER, P, et al.
(författare)
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AMANDA - STATUS-REPORT FROM THE 1993-94 CAMPAIGN AND OPTICAL-PROPERTIES OF THE SOUTH-POLE ICE
- 1995
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Ingår i: NUCLEAR PHYSICS B. - : ELSEVIER SCIENCE BV. - 0550-3213. ; , s. 287-292
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We report the first results of the AMANDA detector. During the antarctic summer 1993-94 four strings were deployed between 0.8 an 1 km depth, each equipped with 20 photomultiplier tubes (PMTs). A laser source was used to investigate the optical properties
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| 5. |
- Askebjer, P., et al.
(författare)
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On the age vs depth and optical clarity of deep ice at South Pole
- 1995
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Ingår i: Journal of Glaciology. - 0022-1430 .- 1727-5652. ; 41:139, s. 445-454
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Tidskriftsartikel (refereegranskat)abstract
- The first four strings of phototubes for the AMANDA high-energy neutrino observatory are now frozen in place at a depth of 800 to 1000 m in ice at the South Pole. During the 1995-96 season an additional six strings will be deployed at greater depths. Provided absorption, scattering, and refraction of visible light are sufficiently small, the trajectory of a muon into which a neutrino converts can be determined by using the array of phototubes to measure the arrival times of \v{C}erenkov light emitted by the muon. To help in deciding on the depth for implantation of the six new strings, we discuss models of age vs depth for South Pole ice, we estimate mean free paths for scattering from bubbles and dust as a function of depth, and we assess distortion of light paths due to refraction at crystal boundaries and interfaces between air-hydrate inclusions and normal ice. We conclude that the depth interval 1600 to 1800 m will be suitably transparent for the next six AMANDA strings and, moreover, that the interval 1600 to 2100 m will be suitably transparent for a future 1-km 3 observatory except possibly in a region a few tens of meters thick at a depth corresponding to a peak in the dust concentration at 60 kyr BP.
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| 6. |
- ASKEBJER, P, et al.
(författare)
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ON THE AGE VS DEPTH AND OPTICAL CLARITY OF DEEP ICE AT THE SOUTH-POLE
- 1995
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Ingår i: JOURNAL OF GLACIOLOGY. - : INT GLACIOL SOC. - 0022-1430. ; 41:139, s. 445-454
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The first four strings of phototubes for the AMANDA high-energy neutrino observatory are now frozen in place at a depth of 800-1000 m in ice at the South Pole. During the 1995-96 season, as many as six more strings will be deployed at greater depths. Prov
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| 7. |
- Askebjer, P., et al.
(författare)
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Optical properties of deep ice at the South Pole : Absorption
- 1997
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Ingår i: Applied Optics. - : Optical Society of America. - 0003-6935 .- 1539-4522. ; 36:18, s. 4168-4180
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Tidskriftsartikel (refereegranskat)abstract
- We discuss recent measurements of the wavelength-dependent absorption coefficients in deep South Pole ice. The method uses transit-time distributions of pulses from a variable-frequency laser sent between emitters and receivers embedded in the ice. At depths of 800-1000 m scattering is dominated by residual air bubbles, whereas absorption occurs both in ice itself and in insoluble impurities. The absorption coefficient increases approximately exponentially with wavelength in the measured interval 410-610 nm. At the shortest wavelength our value is approximately a factor 20 below previous values obtained for laboratory ice and lake ice; with increasing wavelength the discrepancy with previous measurements decreases. At ∼415 to ∼500 nm the experimental uncertainties are small enough for us to resolve an extrinsic contribution to absorption in ice: submicrometer dust particles contribute by an amount that increases with depth and corresponds well with the expected increase seen near the Last Glacial Maximum in Vostok and Dome C ice cores. The laser pulse method allows remote mapping of gross structure in dust concentration as a function of depth in glacial ice.
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| 8. |
- Askebjer, P, et al.
(författare)
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Optical properties of deep ice at the South Pole: Absorption
- 1997
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Ingår i: APPLIED OPTICS. - : OPTICAL SOC AMER. - 0003-6935. ; 36:18, s. 4168-4180
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We discuss recent measurements of the wavelength-dependent absorption coefficients in deep South Pole ice. The method uses transit-time distributions of pulses from a variable-frequency laser sent between emitters and receivers embedded in the ice. At dep
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| 9. |
- Askebjer, P., et al.
(författare)
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Optical properties of the South Pole ice at depths between 0.8 and 1 kilometer
- 1995
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Ingår i: Science. - 0036-8075 .- 1095-9203. ; 267:5201, s. 1147-1150
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 10. |
- ASKEBJER, P, et al.
(författare)
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OPTICAL-PROPERTIES OF THE SOUTH-POLE ICE AT DEPTHS BETWEEN 0.8 AND 1 KILOMETER
- 1995
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Ingår i: SCIENCE. - : AMER ASSOC ADVAN SCIENCE. - 0036-8075. ; 267:5201, s. 1147-1150
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- 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 (similar to 515 nanometers) have been measured in situ with the use of th
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