Intercomparison measurements of Rn concentration in water samples in Poland

The paper presents the results of intercalibration measurements of ²²²Rn concentration in water samples. The aim of the experiments was to evaluate the different measurement methods of radon determination in water samples performed by eleven laboratories in Poland and to test these methods in field work. In the years 2001-2003 three national intercomparison experiments were organized. The results allowed the participating laboratories to improve their measurement methodologies and to achieve better, i.e. more convergent results of determining radon concentration in water samples. The results show that the use of liquid-scintillation technique seems to be the best measurement method. It should be emphasized that comparative experiments are essential for all laboratories and they should be carried out as often as possible, based both on prepared samples with known concentration values of ²²²Rn and natural water samples, the most commonly used in laboratory practice.     

Analysis of anticipated performance of 650-nm GaInP/AlGaInP quantum-well GaAs-based VCSELs at elevated temperatures

The possibility of application of the 650-nm oxide-confined GaInP/AlGaInP quantum-well vertical-cavity surface-emitting diode lasers (VCSELs) at elevated temperatures as sources of the carrier 650-nm wave in the fibre optical communication using POFs has been investigated with the aid of the comprehensive self-consistent model. An increase in the VCSEL threshold current at higher temperatures has been found to be mostly associated with both the carrier leakage from the valley of the Ga_0.43In_0.57P quantum-well material to the X-valley of the (Al_0.67Ga_0.33)_0.52In_0.48P barriers and the band-to-band absorption within the Ga_0.52In_0.48P layer of the band-gap comparable with the energy of emitted radiation. Nevertheless, the AlGaInP VCSELs exhibit encouraging thermal behaviour with the characteristic temperature T₀ equal to as much as 134 K for the active-region temperatures up to 357 K. For the 5-μm devices, the maximal achievable output has been determined to decrease from a quite high value of 1.0 mW for 293 K to 0.6 mW for 320 K and to still high 0.33 mW for 340 K. However, an efficient operation of the above VCSEL at elevated temperatures requires still some structure modifications leading to a reduction of both the above effects, the electron leakage from the valley and the band-to-band absorption within GaInP layers.     

Energy efficiency of near infrared cobalt luminscence in ZnSe:Co determined by a photoacoustic method

The paper presents results of computations of the energy efficiency of the cobalt luminescence in ZnSe:Co determined by the photoacoustic method. The transmission spectra, photoacoustic experimental and theoretical spectra, and the frequency dependence on the photoacoustic amplitude characteristics are presented. From them, the energy efficiency of Co²⁺ the near infrared luminescence (3200 nm) was computed in the frame of new proposed photoacoustic model of computations of the luminescence energy efficiency.     

Analysis of noise properties of an optocoupler device

In the paper, localization of a source of random telegraph signal noise (RTS noise) in optocoupler devices of CNY 17 type was defined. The equivalent noise circuit in low frequency noise for these types of optocouplers was proposed.     

Investigation of temperature characteristics of modern InAsP/InGaAsP multi-quantum-well TJ-VCSELs for optical fibre communication

Continuous-wave (CW) performance of modern 1.3-μm InAsP/InGaAsP multi-quantum-well (MQW) tunnel-junction vertical-cavity surface-emitting diode lasers (TJ-VCSELs) is investigated using our comprehensive self-consistent simulation model to suggest their optimal design for room and elevated temperatures. For increasing ambient temperatures, an increase in the VCSEL threshold current has happened to be mostly associated with the Auger recombination. Nevertheless, the InAsP/InGaAsP VCSELs have been found to exhibit encouraging thermal behaviour with the quite high value of maximal operating temperature of 350 K. It has been found that 5-μm devices seem to be the most optimal ones because they demonstrate both the room temperature (RT) threshold current equal to only 0.55 mA and maximum operating temperature equal to as much as 345 K. For these devices, the characteristic temperature T0 is equal to 92 K for 290–305 K, 51 K for 310–325 K and 29 K for 330–345 K. Therefore, the InAsP/InGaAsP VCSELs have been found to offer very promising performance both at room and elevated temperatures as sources of the carrier 1.3-μm wave in the fibre optical communication using silica fibres.     

An innovative silicon photomultiplier digitizing camera for gamma-ray astronomy

The single-mirror small-size telescope (SST-1M) is one of the three proposed designs for the small-size telescopes (SSTs) of the Cherenkov Telescope Array (CTA) project. The SST-1M will be equipped with a 4 m-diameter segmented reflector dish and an innovative fully digital camera based on silicon photo-multipliers. Since the SST sub-array will consist of up to 70 telescopes, the challenge is not only to build telescopes with excellent performance, but also to design them so that their components can be commissioned, assembled and tested by industry. In this paper we review the basic steps that led to the design concepts for the SST-1M camera and the ongoing realization of the first prototype, with focus on the innovative solutions adopted for the photodetector plane and the readout and trigger parts of the camera. In addition, we report on results of laboratory measurements on real scale elements that validate the camera design and show that it is capable of matching the CTA requirements of operating up to high moonlight background conditions.     

Coincidence investigation of inelastic electron–atom collisions with magnetic selection of scattering angle – feasibility study

New apparatus for electron–atom collision investigations incorporating the magnetic angle changing method into the coincidence technique has been set-up. Combination of the two enables measurements of Electron Impact Coherence Parameters in the full range of scattering angles. First energy loss and coincidence spectra are presented.