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to detect the feeble flux of predicted high energy astrophysical neutrinos , high energy cherenkov neutrino telescopes are build as a grid of photomultiplier tubes ( pmts ) covering a huge geometric volume .
the density of pmts per effective detector area is about 3 orders of magnitude below that for -events triggered in the superkamiokande detector ; this implies a detailed verification of the anticipated performance of these new detectors .
the amanda - ii telescope is located at the geographic south pole and uses the transparent ice of the 3  km thick ice sheet @xcite .
the detector has been installed between november 1995 and february 2000 , and consists of 677 pmts in optical modules ( om ) on 19 vertical strings deployed to depths between 1300m-2400 m .
the main instrumented volume ranges from 1500m-2000 m , it covers a cylinder of 200 m diameter ( fig.[fig : detector_layout ] ) .
strings 1 - 10 form the inner detector of 120 m diameter called amanda - b10 , which was commissioned in 1997 .
they use passive oms with electrical analog signal transmission over 2 km cable .
strings 11 - 19 form the outer cylinder and are based on analog fiber transmission @xcite .
[ fig : detector_layout ]    first physics results obtained with amanda - b10 are presented at this conference by @xcite .
with no astrophysical neutrino sources detected yet , atmospheric neutrinos are the only source to calibrate the sensitivity to the favoured -channel : upgoing @xmath0 s generated in charged current ( cc ) -interactions .     [
fig : cthe_b10 ]    muon track reconstruction is based on a maximum likelidood fit of measured photon arrival times to expected arrival time distributions @xcite@xcite , and uses modeled optical bulk ice properties ( light scattering and absorption ) , and local hole ice effects .
light emitted by muon - induced electromagnetic showers and accompanying muons ( not in the track fit model ) and the low information density per track result in downgoing atmospheric muons being sometimes misreconstructed as upward tracks .
they form the dominant background to s , since they trigger about 10@xmath1 more abundant .
the 1997 data set of the amanda - b10 detector has been analyzed by two independent groups .
they used different modifications of track reconstruction and extended cuts for selecting highest quality upward reconstructed muon tracks to reject the background at acceptable signal efficiencies . from a total sample of 10@xmath2 events triggered during 130 effective livetime days in 1997
, final samples of 223 and 204 events have been extracted , with passing rates of 3 - 4% and residual background contamination of 10% @xcite@xcite .
the observed number of events is consistent with expectation , within a @xmath350% systematic error due to ice property and primary flux uncertainties . in figure
[ fig : cthe_b10 ] the distribution in cosine of the zenith angle after final cuts for the sample of analysis a is shown ( compared to -simulation expectation , normalized to experimental data ) .
angular acceptance of amanda - b10 is seen to be worst for horizontal directions . the angular and energy averaged effective muon area for muon energies of 0.1 - 1tev is 2800m@xmath4 ( weighted over the atmospheric -spectrum ) .
much higher effective areas are observed for other searches ( see below ) .
the amanda - ii telescope is in stable operation since its commissioning in february , 2000 .
reasonable agreement is found between data and simulation @xcite .    for neutrinos from astrophysical sources ( such as active galactic nuclei , agn ) , harder spectra than for atmospheric neutrinos
are expected .
fig.[fig : trig_ener ] shows the expected spectrum of triggered events for atmospheric neutrinos ( full line ) and for a spectrum of agn neutrinos ( dashed line , equal flux set for @xmath5 and @xmath6 ) with an assumed diffuse flux of @xmath7  gev sr@xmath8 s@xmath8@xmath9 .
shown are cc @xmath5 and cc @xmath6 reactions .
events ( thick line ) and charged current @xmath10 events ( thin line ) for atmospheric neutrinos ( full line ) and an agn like spectrum ( dashed line ) . event rate is calculated per livetime year .
, width=245 ]    the total number of triggered upgoing events per livetime year for the different channels are given in table [ tb : s_rate ] , including neutral current ( nc ) interactions .
the -channel was recently shown to yield good sensitivity for diffuse high energy -search @xcite@xcite .
a first detection of the atmospheric neutrino induced cascades is an interesting challenge in view of the low event rate , see @xcite .
.triggered -events per year in amanda - ii . [ cols="^,^,^",options="header " , ]     the analysis of amanda - ii data from 2000 is under way . with -selection cuts tailored to the larger detector , we find the angular acceptance for horizontal directions and the total signal passing rate much improved , compared to amanda - b10 .
fig.[fig : evt_2218020 ] displays a good candidate event for an upward moving muon , reconstructed close to the horizon ( zenith angle = 105@xmath11 ) .    in figure
[ fig : aeff_aii_costh ] , the calculated amanda - ii effective area for 10tev muons is shown as function of the zenith angle at trigger level @xcite .
expected effective areas for two high energy physics analyses are also shown : grb and point source cuts , yielding areas of 30 - 60.000m@xmath4 .
the curve shown for the amanda - b10 reveals the acceptance improvement in horizontal direction .
the amanda - ii telescope reaches effective muon detection areas at 10tev of up to 50000m@xmath4 , depending on the physics objective , and offers better angular coverage than amanda - b10 .
the latter was proven to work as a high energy neutrino detector by the isolation of a combined sample of 325 atmospheric s .
the rate of atmospheric events for the full amanda - ii detector will be about 3 times higher , yielding 800 - 1000 s for year 2000 . flux limits obtainable by amanda - ii for high energy neutrinos from diffuse and point sources will improve by @xmath310 times within 2 years of livetime @xcite .
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the amanda - ii telescope at the south pole is constructed of 677 optical modules at 19 strings . 
 we describe the observation of atmospheric neutrinos with the first stage 10-string detector amanda - b10 , which establishes amanda as a working neutrino telescope . the expected performance for the amanda - ii detector is discussed .