PIXIE III: a very large area photon-counting CMOS pixel ASIC for sharp X-ray spectral imaging

PIXIE III is the third generation of very large area (32 x 25 mm(2)) pixel ASICs developed by Pixirad Imaging Counters s. r. l. to be used in combination with suitable X-ray sensor materials (Silicon, CdTe, GaAs) in hybrid assemblies using flip-chip bonding. A Pixirad unit module based on PIXIE III shows several advances compared to what has been available up to now. It has a very broad energy range (from 2 to 100 keV before full pulse saturation), high speed (100 ns peaking time), high frame rate (larger than 500 fps), dead-time-free operation, good energy resolution (around 2 keV at 20 keV), high photo-peak fraction and sharp spectral separation between the color images. In this paper the results obtained with PIXIE III both in a test bench set-up as well in X-ray imaging applications are discussed

The X-ray polarimetry window reopens

PolarLight is the first dedicated soft X-ray polarimeter in space since the 1970s and is attempting to reopen this long-awaited window in astronomy, explain Principal Investigator Hua Feng and Ronaldo Bellazzini

Measurement of the position resolution of the Gas Pixel Detector

The Gas Pixel Detector was designed and built as a focal plane instrument for X-ray polarimetry of celestial sources, the last unexplored subtopics of X-ray astronomy. It promises to perform detailed and sensitive measurements resolving extended sources and detecting polarization in faint sources in crowded fields at the focus of telescopes of good angular resolution. Its polarimetric and spectral capability were already studied in earlier works. Here we investigate for the first time, with both laboratory measurements and Monte Carlo simulations, its imaging properties to confirm its unique capability to carry out imaging spectral-polarimetry in future X-ray missions.Comment: Submitted to Nuclear Instruments and Methods in Physics Research Section A; 15 figures, 3 table

A MWPC with a cathode coupled delay line read-out as radioactivity detector for DNA repair studies

A non selective method for the isolation of DNA repair-deficient mutants in mammalian cells is discussed. The method requires radioactive labelling of the short DNA sequences synthesized during repair of damaged regions. Mutants should be recognized by the absence of radioactive incorporation into thier DNA. A multiwire proportional chamber (MWPC) is proposed as a suitable radioactivity detector. The performance of a MWPC prototype with a cathode coupled delay line read-out is described and is shown to be adequate for this application. The main avaantages of a MWPC are reviewed with respect to other methods used for β− radioactivity counting of biological samples, such as liquid scintillators or autoradiography: the proposed detection method is non destructive for the cells, which are being kept alive for further biological studies; furthermore many cell clones can be screened within a reasonable time

ELECTRONIC AUTORADIOGRAPHY OF LIVING HUMAN-CELLS WITH A MWPC

Abstract The use of multiwire proportional chamber (MWPC) for mapping the incorporation of a radioactive precursor of DNA biosynthesis by aggregates of cells is discussed. The resolving power, sensitivity and linearity of the developed system are shown, together with preliminary "electronic autoradiograms" of 14C-labelled cells

DNA-repair deficient cells identification with a multiwire proportional chamber

Abstract Tritium labelled mammalian cells with defective repair of UV-induced damage have been identified by using a MWPC as a position sensitive radioactivity detector. The resolving power (≅1.5mm FWHM), sensitivity (≅101Bq/cm2), efficiency (≅10%) and uniformity (≅4%) of the detection system are shown and "electronic autoradiograms" of normal and mutant cultures are presented; cells, rescued after the radioactivity measurement, retain their cloning ability

An X-ray Polarimeter for HXMT Mission

The development of micropixel gas detectors, capable to image tracks produced in a gas by photoelectrons, makes possible to perform polarimetry of X-ray celestial sources in the focus of grazing incidence X-ray telescopes. HXMT is a mission by the Chinese Space Agency aimed to survey the Hard X-ray Sky with Phoswich detectors, by exploitation of the direct demodulation technique. Since a fraction of the HXMT time will be spent on dedicated pointing of particular sources, it could host, with moderate additional resources a pair of X-ray telescopes, each with a photoelectric X-ray polarimeter in the focal plane. We present the design of the telescopes and the focal plane instrumentation and discuss the performance of this instrument to detect the degree and angle of linear polarization of some representative sources. Notwithstanding the limited resources the proposed instrument can represent a breakthrough in X-ray Polarimetry.Comment: 10 pages, 9 figure