We report the observation of multi-exponential scintillation light emission from a CaMoO4 crystal with slow and fast components after both α-particles or γ-quanta irradiation. The slow components with decay times of ∼5 and ∼15μs produce the main contribution to the light yield. Whereas the fast components with ∼10–50ns decay times observed for the first time with such a crystal at room temperature contribute <1% to the crystal total light yield.

Powerful nanosecond light sources based on LEDs have been developed for use in calibration systems of deep underwater neutrino telescopes. The light sources use either matrixes of ultra bright blue InGaN LEDs or new generation high power blue LEDs. It is shown that such light sources have light yield of up to 1010–1012 photons per pulse with very fast light emission kinetics. The developed light sources are currently used in a number of astroparticle physics experiments, namely: the lake Baikal neutrino experiment, the TUNKA EAS experiment, etc.

Powerful nanosecond light sources based on LEDs have been developed for use in astroparticle physics experiments. The light sources use either matrixes of ultra bright blue LEDs or a new generation high power blue LEDs. It's shown that such light sources have light yield of up to 10**10 - 10**12 photons per pulse with very fast light emission kinetics. The described light sources are important for use in calibration systems of Cherenkov and scintillator detectors. The developed light sources are currently used successfully in a number of astroparticle experiments, namely: the TUNKA EAS experiment, the Baikal neutrino experiment etc.

A LED flasher has been developed for TUNKA-133 EAS Cherenkov detector. A blue ultra bright InGaN LED is used as a light source in the flasher. The flasher's driver is based on a fast discharge of a small capacitor via a complementary pair of fast RF transistors. The light yield of the flasher is adjusted in the wide range of from 0 to up to 10**9 photons per pulse. The results of studies of the flasher's amplitude and timing parameters and their stability are presented.

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.

We present the results of studies of a nanosecond light pulser built following J.S.Kapustinsky et al original design and using bright InGaN/GaN ultraviolet and blue LEDs produced by NICHIA CHEMICAL. It is shown how timing characteristics of the pulser depend on the type of LED and the value of power supply voltage.

We present the results of stability studies of nanosecond light sources based on single quantum well (SQW) InGaN/GaN ultra bright blue LEDs. It is shown that the light yield of such light sources and their timing characteristics don't deteriorate even after 10^10 total pulses. The longterm stability of the sources light yield is better than 1%.

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.