- Email: [email protected]
Status of the AMANDA experiment
ELSEVIER
PROCEEDINGS SUPPLEMENTS
Nuclear Physics B (Proc. Suppl.) 70 (1999) 448452
Status of the AMANDA experiment AMANDA Collaboration: E. And&’ , P. Askebjera, S. W. Barwickb , R. BayC , L. Bergstroma, A. Bouchtaa, A. Birond , S. Cariuse , C. Costaf , D. Cowenz , E. Dalberga, P. Ekstrijma, A. Goobara, L. Gray’, A. Hallgren h , F. Halzene, S. Hart’ , Y. HeC, G. Hill’, P. 0. Hultha, S. Hundertmarkd, J. Jacobsenf , A. Jonesi, V. Kandahaif, A. Karle’, P. Lindahle, I. Liubarsky’, D. M. LowderC, P. Marciniewskih, T. Mikolajskid, T. Milled , P. Mockb, R. Morsef, P. Niessend, D. Nygrenk , C. Perez de 10s Herosh, R. Porratab, D. Potteri, P. B. Pricec, A. RichardsC, H. Rubinsteinh, E. Schneiderb, R. Schwarz’, C. Spiering d, 0. Streicherd, T. Thond, S. Tilav’, C. Walcka, C. Wiebuschd, R. Wischnewskid, K. WoschnaggC, and G. Yodhb Presented
by Per Olof Hultha
aFysikum,
Stockholm
University,
Box 6703, SE-113
Department,
University
of California,
Irvine,
CPhysics Department,
University
of California,
Berkeley,
bPhysics
dDESY-Zeuthen, eDepartment fPhysics
D-15735 of Technology,
Department, of Physics
hDepartment
of Radiation
‘Amundsen-Scott
South
jBarto1
Institute,
kPhysics
Division,
Kalmar
University
sDepartment
Research
Zeuthen,
University,
and Astronomy,
Pole Station,
Lawrence
University Berkeley
Sweden
CA 92717, USA CA 94720, USA
Germany
of Wisconsin,
Sciences,
85 Stockholm,
Box 905, SE-391 29 Kalmar, Madison,
University
Uppsala
WI 53706, USA
of Pennsylvania,
University,
Sweden
Philadelphia,
Box 535, SE751
PA 19104, USA
21 Uppsala,
Sweden
Antarctica of Delaware, National
Newark,
Laboratory,
DE 19716, USA Berkeley,
CA 94720, USA
The AMANDA high energy neutrino telescope has successfully been increased in size from four detector strings to ten detector strings during the 1996/1997 season. The first upward going muon-neutrino candidates have been reconstructed from the 1996 year’s four-string data. Three new detector strings will be deployed during 1997/1998 to 2350 metres depth.
1. Introduction The AMANDA detector is using the very clear ice in the glacier at the Amundsen - Scott base at the geographic South Pole as the detector medium for cosmic neutrinos. The air bubbles in ice are at large depth transformed into airhydrate clathrate crystals giving a very transparent medium. Muons and other charged particles produced in neutrino interactions in the ice emit Cherenkov light along the trajectory. The emitted light is detected by photomultipliers (optical 0920-5632/98/$19.00 0 1998 Elsevier Science B.V. PI1 SO920-5632(98)00468-X
All rights reserved
modules, OM) placed in long strings in holes 2000 metres deep. Hot water drilling is used to produce a 60 cm diameter hole in which a detector string is deployed before the water refreezes. The optical modules consist of 20 cm diameter photomultipliers mounted inside glass spheres. The photomultiplier signals are transmitted via coaxial or twisted pair cables up to the surface where a data acquisition system (DA&) stores the relevant data. From the arrival time and intensity of the emitted Cherenkov light the direction of the muon trajectory is reconstructed within a few de-
449
E. Andrks et al. /Nuclear Physics B (Pnx. Suppl.) 70 (1999) 448-452
grees accuracy depending on the neutrino energy. The ice parameters (scattering length and absorp tion length), the relative positions of the modules as well as corrections for different cable length are determined with help of pulsed laser light transmitted via optical fibers to the different OMs. The first four detector strings, with 80 OMs, were deployed 1993/1994 at 800 metres to 1000 metres depth (AMANDA-A). The ice at these depths turned out to have remaining air bubbles giving a too short scattering length (beThe absorption length was on low one metre). the other hand extraordinary long [l, 21. Due to the short scattering length at shallow depth, four new strings with 86 OMs were deployed during 1995/1996 to 1500 - 2000 metres depth (AMANDA-B4). The spacing between the OMs on these strings is 20 metres. The investigations of the ice properties showed that the scattering length increased by two orders of magnitude indicating that the air bubbles had disappeared. The effective scattering length at 1500 - 2000 metres was found to be 24 metres and the absorption length of the order of 100 metres [4]. Figure 1 shows the arrival time of the Cherenkov light as a function of the depth of the optical modules for a down-going muon triggering both AMANDA-A and AMANDA-B4. It can clearly be seen that the amount of scattering is reduced at the larger depth. The points far away are random noise hits. The observed rate for atmosphereic muons to trigger both detectors is 0.1 Hz giving a very useful tagged muon beam for calibration purposes. 2. Deployment
96/97
The AMANDA detector was increased in size in the 1996/1997 season by adding six detector strings with 36 optical modules each. The new strings were placed at a radius of 60 metres around the AMANDA-B4 detector. The distance between the modules on a string is 10 metres and they were placed between 1500 metres and 1860 metres depth. Out of the 216 deployed optical modules, 210 survived the refreezing of the water in the holes. The ten string configuration is named AMANDA-BlO. The time to drill one hole and to deploy a complete string
1 -0.8
’
. .
.
,c’’. 0;*. ??
-1.0
-
.
.
??
I
-1.2
Depth (km)
t
i
I t. :. . ...
L-.............-.................... -2.!20 -15 -10 -5 0 5
Time
10
15
20
(gs)
Figure 1. Arrival time vs depth for Cherenkov photons from an atmospheric muon triggering both AMANDA-A and AMANDA-B4.
was six days. The AMANDA-BlO detector together with the AMANDA-A detector is shown in figure 2 and a top view of the AMANDA-B string locations in figure 3. Twenty OMs were in addition to the electrical read-out also equipped with optical read-out through the optical fibre. The PMT signal is in this way transmitted without any pulse smearing up to the DA& system [5]. The AMANDA-BlO detector is running continuously since February 1997 with a trigger rate of 75 Hz demanding at least 16 hits. In addition to the muon trigger the detector is run in coincidence with the AMANDA-A, SPASEl and SPASE-2 air shower detectors. Triggers for supernova events and gamma ray bursts (GRB) are also implemented.
3. Track
reconstruction
The AMANDA collaboration has developed three independent simulation programs and two independent muon track reconstruction pro-
450
E. And&s et al. /Nuclear Physics B (Pnx. Suppl.) 70 (1999) 448-452
AMANDA-B Surface Hole Pcdions
‘:
;Q
1
40 20
A M
-20
A
-40
M II)
-60
I .
A
9-B w
AMANOA-8
..o
Figure 2. The AMANDA detector 1997. The up per four strings is the AMANDA-B4 detector and the lower 10 string is the AMANDA-BlO detector.
grams. This has been done in order to get enough redundant software for checking the results. The measured ice properties at 1500 - 2000 metres depth are used in the simulation programs. The arrival time for the Cherenkov photons as a function of distance to the muon track is simulated and the distributions are parametrized [6]. These time distributions are then used in the fitting procedure of the reconstruction programs. Thanks to the extraordinary long absorption length in the ice, many photons are reaching the photomultipliers and several of these are not scattered. By using the number of hits with small time residuals (within 15 ns of the expectation) in the reconstruction, denoted N-direct, the quality of the track reconstruction can be controlled.
SPASE2
8-7
0
4
o-2
m
B-10
B-9 1995
Figure 3. Topview the AMANDA-BlO
4.
??
B-l
B-6
-
showing detector.
AMANDA-B4
string
positions
for
coincidences
The South Pole has a large advantage as a site for neutrino telescopes due to the existence of “test beams” of muons from the air shower detectors SPASEl and SPASEP. The primary purpose of running AMANDA-SPASE in coincidence is to study the composition of the cosmic rays. Muons from air showers triggered in coincidence by AMANDA-SPASE can be used for absolute coordinate calibration and test of reconstruction accuracy and efficiency in the AMANDA detector. The air shower detector SPASEZ is situated at a horizontal distance of 370 metres at the snow surface and at an average zenith angle of 12 degrees from AMANDA-B4. We have been using the SPASE2 - AMANDA-B4 coincidence events for analysing the quality of our reconstruction procedure. The acceptance for these events is 32 m2sr and the coincidence rate is 14 events per hour. By selecting coincidence events with at least 8 hits in 2 strings and that the number of N-direct in the AMANDA reconstruction should be at least five we get the results shown in Figure 4. The upper figure shows the reconstructed
451
E. And& et al. /Nuclear Physics B (Ptm. Suppl.) 70 (1999) 448-452
zenith angle of the air showers from the SPASE 2 reconstruction program. No quality cut has been used in the SPASES reconstruction. The lower plot shows the AMANDA-B4 reconstructed zenith angle for these events. The standard deviation of less than four degrees for the angular distribution is in excellent agreement with expectation from simulations including both track reconstruction accuracy and smearing due to SPASE2 - AMANDA-B4 angular acceptance. Despite the simple selection criteria the angular distribution looks very clean with no upward-going reconstructed events. A systematic shift of about three degrees between the two distributions is in qualitative agreement with simulations. The number of events in the plots corresponds to 80 days of data taking.
a)
20
130
140
SPASE-2
150
160
170
1
0
reconstructed 0
5. The first neutrino candidates In 1996 the AMANDA-B4 detector was running effectively for six months and the data was analysed during 1997. In total 4.108 triggers with at least eight hits within two microseconds were recorded. The data were filtered to reduce the background of down-going atmospheric muons. The filter reduced the background by a factor of 25 and the signal (atmospheric neutrinos) by 60% as estimated by simulations. The remaining events were passed through the reconstruction program. The program made first a prereconstruction of the track direction by using a simple linear fit of the depth versus time which reduced the background by another factor of five. The events which passed were fully reconstructed and by demanding the number of N-direct to be at least six only two events passed. In fig 5 the AMANDA-B4 detector is shown with one of the neutrino candidates. The modules marked “up” are upward looking modules. It is an event with eight optical modules hit. The hit modules are indicated by circles with sizes proportional to the light intensity. The reconstructed track length inside the detector is 182 metres and the angle towards zenith is four degrees. The track is passing close to one string (closest approach about 1 metre) giving large amplitudes in the OMs. No hits can be found in the neighboring strings at
120
130
140
AMANDA-B4
150
160
170
d
180
De rees reconstructe8 0
Figure 4. a) Zenith angle of reconstructed air shower events in Spase-2. b) Zenith angle reconstructed in AMANDA-B4 for the same events as in a. The solid line is a gaussian fit to the data distribution.
the same depths. The data from seven month of 1997 taken by the AMANDA-BlO detector will be available for analysis in the beginning of 1998. The effective area of this detector is of the order of lo4 m2 for a TeV-neutrino.
6. AMANDA-II The collaboration will deploy three new detector strings during the season 97/98. The strings will have 42 optical modules each and be distributed from 1200 metres depth to 2350 metres
452
E. And&s et al. /Nuclear
Physics B (Pmt.
Suppl.) 70 (1999) 448-452
optical parameters of the ice indicates that the AMANDA-II detector will have an effective area about five times that of the AMANDA-BlO and have an angular resolution of the order of one degree for muons above 1 TeV. AMANDA-II will be a step towards a detector of the size of 1 km3. 7. ICECUBE The promising results coming out of the AMANDA-B detector shows that it is possible to build a neutrino detector in the ice at the South Pole. For the future, a detector of the size of a km3 is desirable [7] and the collaboration has started to investigate this option for the South Pole (ICECUBE). The number of strings for a detector of this size could be about 80 with e.g. 60 OMs spaced by 15 m. The strings could be spaced with a distance of 100 m. With two drilling teams it would be possible to deploy 16 strings per season. A tentative time schedule for ICECUBE is to build it over 5 years starting 2000/2001 and finishing 2004/2005. The cost for a detector of this size is preliminary estimated to be about $ 30 million and the logistics including fuel, transports to the South Pole etc about % 10 million. REFERENCES 1 A reconstructed up-going neutrino Figure 5. candidate in the AMANDA-B4 detector with Ndirect equal 6.
2
3 depth. The aim of the deployment is to investigate the optical parameters of the ice above and below the existing AMANDA-BlO detector in order to be able to extend the sensitive length for future strings. In addition, the new technique using optical transmission of the PMt signal over the optical fibers will be tested and hopefully fully established. The strings will be placed at a radius of 100 metres around the AMANDA-BlO detector and will be the first in the planned AMANDAII detector with in total 21 strings [3] (including using the obtained AMANDA-BlO). Simulation
4
5 6
7
AMANDA Collaboration: P. Askebjer et al., Science 267 (1995) 1147-1150. AMANDA Collaboration: P. Askebjer et al., Geophysical Research Letters 24 (1997) 1355-1358. A. Biron et al., PRC 97/05, DESY, Germany, June 1997. AMANDA Collaboration presented by P. 0. Hulth, Proc. of the 17th Int. Conf. on Neutrino Physics and Astrophysics (v’96), Helsinki, Finland, 1996, 518-523. A.Karle et al. NIM A387 (1997) 274 C. H. Wiebusch for the AMANDA collaboration, Proc. of 25th ICRC, Durban, South Africa, 1997, Volume 7, 13-16; Adam Bouchta, PhD Thesis, in preparation. “Large Natural Cherenkov Detectors: Water and Ice”, Francis Halzen, these proc.
PROCEEDINGS SUPPLEMENTS
Nuclear Physics B (Proc. Suppl.) 70 (1999) 448452
Status of the AMANDA experiment AMANDA Collaboration: E. And&’ , P. Askebjera, S. W. Barwickb , R. BayC , L. Bergstroma, A. Bouchtaa, A. Birond , S. Cariuse , C. Costaf , D. Cowenz , E. Dalberga, P. Ekstrijma, A. Goobara, L. Gray’, A. Hallgren h , F. Halzene, S. Hart’ , Y. HeC, G. Hill’, P. 0. Hultha, S. Hundertmarkd, J. Jacobsenf , A. Jonesi, V. Kandahaif, A. Karle’, P. Lindahle, I. Liubarsky’, D. M. LowderC, P. Marciniewskih, T. Mikolajskid, T. Milled , P. Mockb, R. Morsef, P. Niessend, D. Nygrenk , C. Perez de 10s Herosh, R. Porratab, D. Potteri, P. B. Pricec, A. RichardsC, H. Rubinsteinh, E. Schneiderb, R. Schwarz’, C. Spiering d, 0. Streicherd, T. Thond, S. Tilav’, C. Walcka, C. Wiebuschd, R. Wischnewskid, K. WoschnaggC, and G. Yodhb Presented
by Per Olof Hultha
aFysikum,
Stockholm
University,
Box 6703, SE-113
Department,
University
of California,
Irvine,
CPhysics Department,
University
of California,
Berkeley,
bPhysics
dDESY-Zeuthen, eDepartment fPhysics
D-15735 of Technology,
Department, of Physics
hDepartment
of Radiation
‘Amundsen-Scott
South
jBarto1
Institute,
kPhysics
Division,
Kalmar
University
sDepartment
Research
Zeuthen,
University,
and Astronomy,
Pole Station,
Lawrence
University Berkeley
Sweden
CA 92717, USA CA 94720, USA
Germany
of Wisconsin,
Sciences,
85 Stockholm,
Box 905, SE-391 29 Kalmar, Madison,
University
Uppsala
WI 53706, USA
of Pennsylvania,
University,
Sweden
Philadelphia,
Box 535, SE751
PA 19104, USA
21 Uppsala,
Sweden
Antarctica of Delaware, National
Newark,
Laboratory,
DE 19716, USA Berkeley,
CA 94720, USA
The AMANDA high energy neutrino telescope has successfully been increased in size from four detector strings to ten detector strings during the 1996/1997 season. The first upward going muon-neutrino candidates have been reconstructed from the 1996 year’s four-string data. Three new detector strings will be deployed during 1997/1998 to 2350 metres depth.
1. Introduction The AMANDA detector is using the very clear ice in the glacier at the Amundsen - Scott base at the geographic South Pole as the detector medium for cosmic neutrinos. The air bubbles in ice are at large depth transformed into airhydrate clathrate crystals giving a very transparent medium. Muons and other charged particles produced in neutrino interactions in the ice emit Cherenkov light along the trajectory. The emitted light is detected by photomultipliers (optical 0920-5632/98/$19.00 0 1998 Elsevier Science B.V. PI1 SO920-5632(98)00468-X
All rights reserved
modules, OM) placed in long strings in holes 2000 metres deep. Hot water drilling is used to produce a 60 cm diameter hole in which a detector string is deployed before the water refreezes. The optical modules consist of 20 cm diameter photomultipliers mounted inside glass spheres. The photomultiplier signals are transmitted via coaxial or twisted pair cables up to the surface where a data acquisition system (DA&) stores the relevant data. From the arrival time and intensity of the emitted Cherenkov light the direction of the muon trajectory is reconstructed within a few de-
449
E. Andrks et al. /Nuclear Physics B (Pnx. Suppl.) 70 (1999) 448-452
grees accuracy depending on the neutrino energy. The ice parameters (scattering length and absorp tion length), the relative positions of the modules as well as corrections for different cable length are determined with help of pulsed laser light transmitted via optical fibers to the different OMs. The first four detector strings, with 80 OMs, were deployed 1993/1994 at 800 metres to 1000 metres depth (AMANDA-A). The ice at these depths turned out to have remaining air bubbles giving a too short scattering length (beThe absorption length was on low one metre). the other hand extraordinary long [l, 21. Due to the short scattering length at shallow depth, four new strings with 86 OMs were deployed during 1995/1996 to 1500 - 2000 metres depth (AMANDA-B4). The spacing between the OMs on these strings is 20 metres. The investigations of the ice properties showed that the scattering length increased by two orders of magnitude indicating that the air bubbles had disappeared. The effective scattering length at 1500 - 2000 metres was found to be 24 metres and the absorption length of the order of 100 metres [4]. Figure 1 shows the arrival time of the Cherenkov light as a function of the depth of the optical modules for a down-going muon triggering both AMANDA-A and AMANDA-B4. It can clearly be seen that the amount of scattering is reduced at the larger depth. The points far away are random noise hits. The observed rate for atmosphereic muons to trigger both detectors is 0.1 Hz giving a very useful tagged muon beam for calibration purposes. 2. Deployment
96/97
The AMANDA detector was increased in size in the 1996/1997 season by adding six detector strings with 36 optical modules each. The new strings were placed at a radius of 60 metres around the AMANDA-B4 detector. The distance between the modules on a string is 10 metres and they were placed between 1500 metres and 1860 metres depth. Out of the 216 deployed optical modules, 210 survived the refreezing of the water in the holes. The ten string configuration is named AMANDA-BlO. The time to drill one hole and to deploy a complete string
1 -0.8
’
. .
.
,c’’. 0;*. ??
-1.0
-
.
.
??
I
-1.2
Depth (km)
t
i
I t. :. . ...
L-.............-.................... -2.!20 -15 -10 -5 0 5
Time
10
15
20
(gs)
Figure 1. Arrival time vs depth for Cherenkov photons from an atmospheric muon triggering both AMANDA-A and AMANDA-B4.
was six days. The AMANDA-BlO detector together with the AMANDA-A detector is shown in figure 2 and a top view of the AMANDA-B string locations in figure 3. Twenty OMs were in addition to the electrical read-out also equipped with optical read-out through the optical fibre. The PMT signal is in this way transmitted without any pulse smearing up to the DA& system [5]. The AMANDA-BlO detector is running continuously since February 1997 with a trigger rate of 75 Hz demanding at least 16 hits. In addition to the muon trigger the detector is run in coincidence with the AMANDA-A, SPASEl and SPASE-2 air shower detectors. Triggers for supernova events and gamma ray bursts (GRB) are also implemented.
3. Track
reconstruction
The AMANDA collaboration has developed three independent simulation programs and two independent muon track reconstruction pro-
450
E. And&s et al. /Nuclear Physics B (Pnx. Suppl.) 70 (1999) 448-452
AMANDA-B Surface Hole Pcdions
‘:
;Q
1
40 20
A M
-20
A
-40
M II)
-60
I .
A
9-B w
AMANOA-8
..o
Figure 2. The AMANDA detector 1997. The up per four strings is the AMANDA-B4 detector and the lower 10 string is the AMANDA-BlO detector.
grams. This has been done in order to get enough redundant software for checking the results. The measured ice properties at 1500 - 2000 metres depth are used in the simulation programs. The arrival time for the Cherenkov photons as a function of distance to the muon track is simulated and the distributions are parametrized [6]. These time distributions are then used in the fitting procedure of the reconstruction programs. Thanks to the extraordinary long absorption length in the ice, many photons are reaching the photomultipliers and several of these are not scattered. By using the number of hits with small time residuals (within 15 ns of the expectation) in the reconstruction, denoted N-direct, the quality of the track reconstruction can be controlled.
SPASE2
8-7
0
4
o-2
m
B-10
B-9 1995
Figure 3. Topview the AMANDA-BlO
4.
??
B-l
B-6
-
showing detector.
AMANDA-B4
string
positions
for
coincidences
The South Pole has a large advantage as a site for neutrino telescopes due to the existence of “test beams” of muons from the air shower detectors SPASEl and SPASEP. The primary purpose of running AMANDA-SPASE in coincidence is to study the composition of the cosmic rays. Muons from air showers triggered in coincidence by AMANDA-SPASE can be used for absolute coordinate calibration and test of reconstruction accuracy and efficiency in the AMANDA detector. The air shower detector SPASEZ is situated at a horizontal distance of 370 metres at the snow surface and at an average zenith angle of 12 degrees from AMANDA-B4. We have been using the SPASE2 - AMANDA-B4 coincidence events for analysing the quality of our reconstruction procedure. The acceptance for these events is 32 m2sr and the coincidence rate is 14 events per hour. By selecting coincidence events with at least 8 hits in 2 strings and that the number of N-direct in the AMANDA reconstruction should be at least five we get the results shown in Figure 4. The upper figure shows the reconstructed
451
E. And& et al. /Nuclear Physics B (Ptm. Suppl.) 70 (1999) 448-452
zenith angle of the air showers from the SPASE 2 reconstruction program. No quality cut has been used in the SPASES reconstruction. The lower plot shows the AMANDA-B4 reconstructed zenith angle for these events. The standard deviation of less than four degrees for the angular distribution is in excellent agreement with expectation from simulations including both track reconstruction accuracy and smearing due to SPASE2 - AMANDA-B4 angular acceptance. Despite the simple selection criteria the angular distribution looks very clean with no upward-going reconstructed events. A systematic shift of about three degrees between the two distributions is in qualitative agreement with simulations. The number of events in the plots corresponds to 80 days of data taking.
a)
20
130
140
SPASE-2
150
160
170
1
0
reconstructed 0
5. The first neutrino candidates In 1996 the AMANDA-B4 detector was running effectively for six months and the data was analysed during 1997. In total 4.108 triggers with at least eight hits within two microseconds were recorded. The data were filtered to reduce the background of down-going atmospheric muons. The filter reduced the background by a factor of 25 and the signal (atmospheric neutrinos) by 60% as estimated by simulations. The remaining events were passed through the reconstruction program. The program made first a prereconstruction of the track direction by using a simple linear fit of the depth versus time which reduced the background by another factor of five. The events which passed were fully reconstructed and by demanding the number of N-direct to be at least six only two events passed. In fig 5 the AMANDA-B4 detector is shown with one of the neutrino candidates. The modules marked “up” are upward looking modules. It is an event with eight optical modules hit. The hit modules are indicated by circles with sizes proportional to the light intensity. The reconstructed track length inside the detector is 182 metres and the angle towards zenith is four degrees. The track is passing close to one string (closest approach about 1 metre) giving large amplitudes in the OMs. No hits can be found in the neighboring strings at
120
130
140
AMANDA-B4
150
160
170
d
180
De rees reconstructe8 0
Figure 4. a) Zenith angle of reconstructed air shower events in Spase-2. b) Zenith angle reconstructed in AMANDA-B4 for the same events as in a. The solid line is a gaussian fit to the data distribution.
the same depths. The data from seven month of 1997 taken by the AMANDA-BlO detector will be available for analysis in the beginning of 1998. The effective area of this detector is of the order of lo4 m2 for a TeV-neutrino.
6. AMANDA-II The collaboration will deploy three new detector strings during the season 97/98. The strings will have 42 optical modules each and be distributed from 1200 metres depth to 2350 metres
452
E. And&s et al. /Nuclear
Physics B (Pmt.
Suppl.) 70 (1999) 448-452
optical parameters of the ice indicates that the AMANDA-II detector will have an effective area about five times that of the AMANDA-BlO and have an angular resolution of the order of one degree for muons above 1 TeV. AMANDA-II will be a step towards a detector of the size of 1 km3. 7. ICECUBE The promising results coming out of the AMANDA-B detector shows that it is possible to build a neutrino detector in the ice at the South Pole. For the future, a detector of the size of a km3 is desirable [7] and the collaboration has started to investigate this option for the South Pole (ICECUBE). The number of strings for a detector of this size could be about 80 with e.g. 60 OMs spaced by 15 m. The strings could be spaced with a distance of 100 m. With two drilling teams it would be possible to deploy 16 strings per season. A tentative time schedule for ICECUBE is to build it over 5 years starting 2000/2001 and finishing 2004/2005. The cost for a detector of this size is preliminary estimated to be about $ 30 million and the logistics including fuel, transports to the South Pole etc about % 10 million. REFERENCES 1 A reconstructed up-going neutrino Figure 5. candidate in the AMANDA-B4 detector with Ndirect equal 6.
2
3 depth. The aim of the deployment is to investigate the optical parameters of the ice above and below the existing AMANDA-BlO detector in order to be able to extend the sensitive length for future strings. In addition, the new technique using optical transmission of the PMt signal over the optical fibers will be tested and hopefully fully established. The strings will be placed at a radius of 100 metres around the AMANDA-BlO detector and will be the first in the planned AMANDAII detector with in total 21 strings [3] (including using the obtained AMANDA-BlO). Simulation
4
5 6
7
AMANDA Collaboration: P. Askebjer et al., Science 267 (1995) 1147-1150. AMANDA Collaboration: P. Askebjer et al., Geophysical Research Letters 24 (1997) 1355-1358. A. Biron et al., PRC 97/05, DESY, Germany, June 1997. AMANDA Collaboration presented by P. 0. Hulth, Proc. of the 17th Int. Conf. on Neutrino Physics and Astrophysics (v’96), Helsinki, Finland, 1996, 518-523. A.Karle et al. NIM A387 (1997) 274 C. H. Wiebusch for the AMANDA collaboration, Proc. of 25th ICRC, Durban, South Africa, 1997, Volume 7, 13-16; Adam Bouchta, PhD Thesis, in preparation. “Large Natural Cherenkov Detectors: Water and Ice”, Francis Halzen, these proc.