R. Dabrowski

Readout electronics for the GEM detector.

A novel approach to the Gas Electron Multiplier (GEM) detector readout is presented. Unlike commonly used methods, based on discriminators[2],[3] and analogue FIFOs[1], the method developed uses simultaneously sampling high speed ADCs and advanced FPGA-based processing logic to estimate the energy of every single photon. Such method is applied to every GEM strip signal. It is especially useful in case of crystal-based spectrometers for soft X-rays, where higher order reflections need to be identified and rejected[5].

Proton spectroscopy of Ni 48, Fe 46, and Cr 44

Results of decay spectroscopy on nuclei in vicinity of the doubly magic 48Ni are presented. The measurements were performed with a Time Projection Chamber with optical readout which records tracks of ions and protons in the gaseous volume. Six decays of 48Ni including four events of two-proton ground-state radioactivity were recorded. An advanced reconstruction procedure yielded the 2p decay energy for 48Ni of Q2p = 1.29(4) MeV. In addition, the energy spectra of \b{eta}-delayed protons emitted in the decays of 44Cr and 46Fe, as well as half-lives and branching ratios were determined. The results were found to be consistent with the previous measurements made with Si detectors. A new proton line in the decay of 44Cr corresponding to the decay energy of 760 keV is reported. The first evidence for the \b{eta}2p decay of 46 Fe, based on one clear event, is shown.

Automatic test-bench for GEM detectors

The paper describes construction of a scalable, automatic measurement system to research GEM detectors. The testbench enables concurrent and precise measurements of many discharge current signals originating from the charges generated by the avalanche process in gas in the GEM micro-holes where the electric field gradient is high. We used Tektronix scopes MSO/DPO4104 and MSO/DPO5104 and Matlab to collect and process the data. Construction of the test-bench is presented in terms of hardware and software. The examples of lab condition measurements were presented. Analysis of these data enable the estimation of the quality of the GEM detector.

Hunting for Gamma Ray Bursts with Pi of the Sky telescopes in Chile and Spain

The Pi of the Sky is a system of wide field of view robotic telescopes, which search for short timescale astrophysical phenomena, especially for prompt optical GRB emission. The system was designed for autonomous operation, monitoring a large fraction of the sky with 12 − 13 range and time resolution of the order of 1− 10 seconds. System design and observation strategy were successfully tested with a prototype detector operational in 2004-2009 at Las Campanas Observatory, Chile, and moved to San Pedro de Atacama Observatory in March 2011. In October 2010 the first unit of the final Pi of the Sky detector system, with 4 CCD cameras, was successfully installed in the INTA El Arenosillo Test Centre in Spain. Three more units (12 CCD cameras) are being prepared for installation on a new platform in INTA, aiming at a total coverage of about 6 400 square degrees. Status and performance of the detectors is presented.

delayed proton emission branches in 43Cr

The beta+ decay of very neutron deficient 43Cr has been studied by means of an imaging time projection chamber which allowed recording tracks of charged particles. Events of beta-delayed emission of one-, two-, and three protons were clearly identified. The absolute branching ratios for these channels were determined to be 81(4)%, 7.1(4)%, and 0.08(3)%, respectively. The 43Cr is thus established as the second case in which the beta-3p decay occurs. Although the feeding to the proton-bound states in 43V is expected to be negligible, the large branching ratio of 12(4)% for decays without proton emission is found.

Apparatus to search for optical flashes of extragalactic origin

An apparatus is described to search for optical, point-like flashes in the sky at the time scale of seconds. Such flashes are expected to accompany gamma ray bursts (GRB) observed routinely by satellites and proven to be of extragalactic origin. So far only one such flash has been recorded shortly after the GRB, because standard methods of observational astronomy are not suitable for the time scale of seconds. In this paper, a novel approach is proposed based on experience from particle physics experiments. An apparatus is described which monitors the sky continuously. The large data stream is analysed on-line and potentially interesting events are selected by a multilevel trigger system. In the first phase of the project the apparatus consists of two CCD cameras, especially designed for this project and a robotic mount used to scan interesting regions of the sky. In the second phase the experiment will consist of two sets of 16 cameras on fixed mounts, covering almost all visible sky.