V. Debur

Position-sensitive detector for the 6-m optical telescope

A position-sensitive detector (PSD) for photometrical and spectral observation on the 6-m optical telescope of the Special Astrophysical Observatory (Russia) is described. The PSD consists of: a position-sensitive tube; amplifiers of output signals; analog-to-digital converters (ADC) and a digital logic plate, which produces a signal for ADC start and an external strobe pulse for reading the information by registration system. If necessary, a thermoelectric cooler can be used. The position-sensitive tube has the following main elements: a photocathode, electrodes of inverting optics, a block of microchannel plates and a quadrant position-sensitive collector.The main parameters of the PSD are: the diameter of the sensitive surface is 25 mm; the spatial resolution is better than 100 μm in the centre and a little worse on the periphery; the dead time is near 0.5 μs; the detection quantum efficiency is defined by the photocathode and it is not less than 0.1, as a rule; dark current is about hundreds of cps, or less, when cooling. PSD spectral sensitivity depends on the type of photocathode and input window material. We use a multialkali photocathode and a fiber or UV-glass, which gives the short-wave cut of 360 or 250 nm, respectively.

The multicolor panoramic photometer-polarimeter with high time resolution based on the PSD

Multicolor Panoramic Photometer-Polarimeter (MPPP) with a time resolution of 1 microsecond has been built based on a PSD and used at the 6-meter telescope in SAO (Russia). The device allows registration of the photon fluxes in four photometric bands simultaneously and finding values of 3 Stokes parameters. MPPP consists of Position-Sensitive Detector (PSD), acquisition MANIA-system, polarization unit and a set of dichroic filters. MPPP gives a possibility of detecting photons in 2 pupils with a size of 10 - 15 arc sec centered on the object and comparison star positions simultaneously. The first half of the object photon flux passes through the phase rotating plate and polarizer, and the second one through the polarizer alone. MPPP registers in each of the 4 filters four images of the object with different orientations of polarization plane and one image of a comparison star. It allows measuring instantaneous Stokes parameters. The main astrophysical problems to be solved with MPPP are as follows: investigation of optical pulsars; study of GRB phenomenon in the optical range; searching for single black holes; study of fast variability of X-ray binaries. As an illustration of MPPP use, the results of observations at the 6-meter telescope of Crab pulsar and soft gamma repeater are presented.

Panoramic detector with high time resolution on base of GaAs photocathode

The Position-Sensitive Detector (PSD) on base of GaAs photocathode and microchannel plate set has been developed. PSD consists of thick semiconductor photocathode with quantum efficiency about 48% in the range of 4000-8000AA, two microchannel plates, and 16-electrode collector. The detector has spatial resolution of 20-30 microns for about 5 • 105 pixels, time resolution of 1 us and effective sensitivity up to 40%.

Devices and software for optical panoramic observations with microsecond time resolution

The set of equipment and software of MANIA experiment for search for and study of astrophysical objects variability with time resolution of 1 us is described. Observations are carried out at the Russian 6‐meter telescope by means of universal photospectropolarimeter. This device is equipped with different optical units which implement four observational modes—spectroscopic, spectropolarimetric, photometric, and photopolarimetric. The use of position‐sensitive detector with set of microchannel plates gives possibility to register object photon fluxes in different colour bands and for different orientations of polarizer simultaneously. Acquisition system “Quantochron 4‐48” on line with computer accumulates observational data with time resolution of 1 microsecond. The features of software intended for processing of panoramic data of high time resolution are discussed.

Search for fast optical activity of SGR 1806-20 at the SAO RAS 6-m telescope

The region of SGR 1806-20 localization was observed during its gamma-ray activity in 2001. The observations have been performed on the 6-meter telescope of the Special Astrophysical Observatory, using the Panoramic Photometer-Polarimeter (PPP). The search for variability was performed on the

Ground-based complex for detection and investigation of fast optical transients in wide field

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Position‐Sensitive Detector with GaAs photocathode and high time resolution

- 10 s time scale, and its results were compared to the properties of corresponding x-ray flares.

Short time scale pulse stability of the Crab pulsar in the optical band

To study short stochastic optical flares of different objects (GRBs, SNs, etc) of unknown localizations as well as NEOs it is necessary to monitor large regions of sky with high time resolution. We developed a system which consists of wide-field camera (FOW is 400-600 sq.deg.) using TV-CCD with time resolution of 0.13 s to record and classify optical transients, and a fast robotic telescope aimed to perform their spectroscopic and photometric investigation just after detection. Such two telescope complex TORTOREM combining wide-field camera TORTORA and robotic telescope REM operated from May 2006 at La Silla ESO observatory. Some results of its operation, including first fast time resolution study of optical transient accompanying GRB and discovery of its fine time structure, are presented. Prospects for improving the complex efficiency are given.

FAVOR (FAst Variability Optical Registration) - two-telescope complex for detection and investigation of short optical transients

The Position‐Sensitive Detector (PSD) on base of GaAs photocathode and microchannel plate set has been developed. PSD consists of thick semi‐conductor photocathode with quantum efficiency about 48% in the range of 4000–7500 A, two micro‐channel plates, and 16‐electrode collector. The detector has spatial resolution of 20–40 microns for about 5⋅102 pixels, time resolution of 1 μs and effective sensitivity up to 35%.