44 research outputs found
Photoelectron backscattering in vacuum phototubes
In this article we describe results of a photoelectron backscattering effect
in vacuum phototubes: classical photomultipliers (PMT) and hybrid phototubes
(PH). Late pulses occurring in PMTs are attributed to the photoelectron
backscattering and distinguished from pulses due to an anode glow effect. The
late pulses are measured in a number of PMTs and HPs with various photocathode
sizes covering 1-50 cm range and different types of the first dynode materials
and construction designs. It is shown that the late pulses are a generic
feature of all vacuum photodetectors - PMTs and PHs and they don't deteriorate
dramatically amplitude and timing responses of vacuum phototubes
Measurements of group velocity of light in the lake Baikal water
The results of direct measurements of group velocity of light in the lake
Baikal water at the depth of 1100 m are presented. The lake Baikal water
dispersion has been measured at three wavelengths: 370 nm, 470 nm and 525 nm.
The results are in a rather good agreement with theoretical predictions.Comment: 4 pages, 5 figures, talk presented at RICH2002, to be published in
NIMA; misprints corrected in formula at page
The quest for the ideal photodetector for the next generation deep-underwater neutrino telescopes
We review photodetectors used in present running neutrino telescopes. After a
brief historical discourse, the photodetector requirements for the next
generation deep underwater neutrino telescopes are discussed. It is shown that
large area vacuum hybrid phototubes are the closest to the ideal photodetector
for such kind of applications when compared with other vacuum phototubes.Comment: 5 pages, 5 figure
Simulation of large photomultipliers for experiments in astroparticle physics
We have developed an accurate simulation model of the large 9 inch
photomultiplier tubes (PMT) used in water-Cherenkov detectors of cosmic-ray
induced extensive air-showers. This work was carried out as part of the
development of the Offline simulation software for the Pierre Auger Observatory
surface array, but our findings may be relevant also for other astrophysics
experiments that employ similar large PMTs.
The implementation is realistic in terms of geometrical dimensions, optical
processes at various surfaces, thin-film treatment of the photocathode, and
photon reflections on the inner structure of the PMT. With the quantum
efficiency obtained for this advanced model we have calibrated a much simpler
and a more rudimentary model of the PMT which is more practical for massive
simulation productions. We show that the quantum efficiency declared by
manufactures of the PMTs is usually determined under conditions substantially
different from those relevant for the particular experiment and thus requires
careful (re)interpretation when applied to the experimental data or when used
in simulations. In principle, the effective quantum efficiency could vary
depending on the optical characteristics of individual events.Comment: 8 pages, 11 figure
High Energy Neutrino Telescopes in the Northern Hemisphere
We review the status and results of the high energy neutrino telescopes in
the Northern Hemisphere, namely ANTARES and Baikal (NT200+).Comment: Contribution to VLvNT 2011, to be published in NIM A, 6 pages, 8
figure
The optical module of the Baikal deep underwater neutrino telescope
A deep underwater Cherenkov telescope has been operating since 1993 in stages
of growing size at 1.1 km depth in Lake Baikal. The key component of the
telescope is the Optical Module (OM) which houses the highly sensitive
phototube QUASAR-370. We describe design and parameters of the QUASAR-370, the
layout of the optical module, the front-end electronics and the calibration
procedures, and present selected results from the five-year operation
underwater. Also, future developments with respect to a telescope consisting
from several thousand OMs are discussed.Comment: 30 pages, 24 figure
Registration of atmospheric neutrinos with the Baikal neutrino telescope
We present first neutrino induced events observed with a deep underwater
neutrino telescope. Data from 70 days effective life time of the BAIKAL
prototype telescope NT-96 have been analyzed with two different methods. With
the standard track reconstruction method, 9 clear upward muon candidates have
been identified, in good agreement with 8.7 events expected from Monte Carlo
calculations for atmospheric neutrinos. The second analysis is tailored to
muons coming from close to the opposite zenith. It yields 4 events, compared to
3.5 from Monte Carlo expectations. From this we derive a 90 % upper flux limit
of 1.1 * 10^-13 cm^-2 sec^-1 for muons in excess of those expected from
atmospheric neutrinos with zenith angle > 150 degrees and energy > 10GeV.Comment: 20 pages, 11 figure
The Lake Baikal neutrino experiment
We rewiew the present status of the Baikal Neutrino Project and present the
results of a search for high energy neutrinos with the detector intermediate
stage NT-96.Comment: 3 pages, 2 figures, to appear in the Proceedings of Sixth
International Workshop on Topics in Astroparticle and Underground Physics
(TAUP99), September 6-10, 1999, Pais, Franc
BAIKAL experiment: status report
We review the present status of the Baikal Neutrino Project and present the
results obtained with the deep underwater neutrino telescope NT-200.Comment: 4 pages, 3 figures. Presented at TAUP 2001 (7th international
workshop on Topics in Astroparticle and Underground Physics), Sep. 2001,
Laboratori Nazionali del Gran Sasso, Assergi, Ital
The Lake Baikal neutrino experiment: selected results
We review the present status of the lake Baikal Neutrino Experiment and
present selected physical results gained with the consequetive stages of the
stepwise increasing detector: from NT-36 to NT-96. Results cover atmospheric
muons, neutrino events, very high energy neutrinos, search for neutrino events
from WIMP annihilation, search for magnetic monopoles and environmental
studies. We also describe an air Cherenkov array developed for the study of
angular resolution of NT-200.Comment: 25 pages, 12 figures. To appear in the Procrrdings of International
Conference on Non-Accelerator New Physics, June 28 - July 3, 1999, Dubna,
Russi