arXiv subjects

M. M. Massai

Publications and source records attributed to M. M. Massai.

7 recordsLinked to original sources

arXiv2014

Plasduino: an inexpensive, general purpose data acquisition framework for educational experiments

Based on the Arduino development platform, Plasduino is an open-source data acquisition framework specifically designed for educational physics experiments. The source code, schematics and documentation are in the public domain under a GPL license and the system, streamlined for low cost and ease of use, can be replicated on the scale of a typical didactic lab with minimal effort. We describe the basic architecture of the system and illustrate its potential with some real-life examples.

physics.ed-ph↗

arXiv2007

Imaging with the invisible light

We describe a UV photo-detector with single photon(electron) counting and imaging capability. It is based on a CsI photocathode, a GEM charge multiplier and a self triggering CMOS analog pixel chip with 105k pixels at 50 micron pitch. The single photoelectron produced by the absorption of a UV photon is drifted to and multiplied inside a single GEM hole. The coordinates of the GEM avalanche are reconstructed with high accuracy (4 micron rms) by the pixel chip. As a result the map of the GEM holes, arranged on a triangular pattern at 50micron pitch, is finely imaged.

physics.ins-det↗

arXiv2006

A Sealed Gas Pixel Detector for X-ray Astronomy

We report on the results of a new, sealed, Gas Pixel Detector. The very compact design and the absence of the gas flow system, make this detector substantially ready for use as focal plane detector for future X-ray space telescopes. The instrument brings high sensitivity to X-ray polarimetry, which is the last unexplored field of X-ray astronomy. It derives the polarization information from the track of the photoelectrons that are imaged by a high gain (>1000), fine pitch GEM that matches the pitch of a pixel ASIC which is the collecting anode of the GPD (105k, 50 micron wide, hexagonal cells). The device is able to simultaneously perform good imaging (50-60 micron), moderate spectroscopy (~15% at 6 keV) as well as fast, high rate timing in the 1-10keV range. Moreover, being truly 2D, it is non dispersive and does not require any rotation. The great improvement of sensitivity, at least two orders of magnitude with respect to traditional polarimeters (based on Bragg crystals or Thomson scattering), will allow the direct exploration of the most dramatic objects of the X-ray sky. At the focus of the large mirror area of the XEUS telescope it will be decisive in reaching many of the scientific goals of the mission. With integration times of the order of one day, polarimetry of Active Galactic Nuclei at the per cent level will be possible, making for a real breakthrough in high energy astrophysics.

astro-ph↗

arXiv2006

Direct reading of charge multipliers with a self-triggering CMOS analog chip with 105k pixels at 50 micron pitch

We report on a large active area (15x15mm2), high channel density (470 pixels/mm2), self-triggering CMOS analog chip that we have developed as pixelized charge collecting electrode of a Micropattern Gas Detector. This device, which represents a big step forward both in terms of size and performance, is the last version of three generations of custom ASICs of increasing complexity. The CMOS pixel array has the top metal layer patterned in a matrix of 105600 hexagonal pixels at 50 micron pitch. Each pixel is directly connected to the underneath full electronics chain which has been realized in the remaining five metal and two poly-silicon layers of a 0.18 micron VLSI technology. The chip has customizable self-triggering capability and includes a signal pre-processing function for the automatic localization of the event coordinates. In this way it is possible to reduce significantly the readout time and the data volume by limiting the signal output only to those pixels belonging to the region of interest. The very small pixel area and the use of a deep sub-micron CMOS technology has brought the noise down to 50 electrons ENC. Results from in depth tests of this device when coupled to a fine pitch (50 micron on a triangular pattern) Gas Electron Multiplier are presented. The matching of readout and gas amplification pitch allows to get optimal results. The application of this detector for Astronomical X-Ray Polarimetry is discussed. The experimental detector response to polarized and unpolarized X-ray radiation when working with two gas mixtures and two different photon energies is shown. Results from a full MonteCarlo simulation for several galactic and extragalactic atronomical sources are also reported.

physics.ins-det↗

arXiv2006

Opening a New Window to Fundamental Physics and Astrophysics: X-ray Polarimetry

An extensive theoretical literature predicts that X-ray Polarimetry can directly determine relevant physical and geometrical parameters of astrophysical sources, and discriminate between models further than allowed by spectral and timing data only. X-ray Polarimetry can also provide tests of Fundamental Physics. A high sensitivity polarimeter in the focal plane of a New Generation X-ray telescope could open this new window in the High Energy Sky.

astro-ph↗

arXiv2006

Gas Pixel Detectors for X-ray Polarimetry applications

We discuss a new class of Micro Pattern Gas Detectors, the Gas Pixel Detector (GPD), in which a complete integration between the gas amplification structure and the read-out electronics has been reached. An Application-Specific Integrated Circuit (ASIC) built in deep sub-micron technology has been developed to realize a monolithic device that is, at the same time, the pixelized charge collecting electrode and the amplifying, shaping and charge measuring front-end electronics. The CMOS chip has the top metal layer patterned in a matrix of 80 micron pitch hexagonal pixels, each of them directly connected to the underneath electronics chain which has been realized in the remaining five layers of the 0.35 micron VLSI technology. Results from tests of a first prototype of such detector with 2k pixels and a full scale version with 22k pixels are presented. The application of this device for Astronomical X-Ray Polarimetry is discussed. The experimental detector response to polarized and unpolarized X-ray radiation is shown. Results from a full MonteCarlo simulation for two astronomical sources, the Crab Nebula and the Hercules X1, are also reported.

astro-ph↗

arXiv2004

Reading a GEM with a VLSI pixel ASIC used as a direct charge collecting anode

In MicroPattern Gas Detectors (MPGD) when the pixel size is below 100 micron and the number of pixels is large (above 1000) it is virtually impossible to use the conventional PCB read-out approach to bring the signal charge from the individual pixel to the external electronics chain. For this reason a custom CMOS array of 2101 active pixels with 80 micron pitch, directly used as the charge collecting anode of a GEM amplifying structure, has been developed and built. Each charge collecting pad, hexagonally shaped, realized using the top metal layer of a deep submicron VLSI technology is individually connected to a full electronics chain (pre-amplifier, shaping-amplifier, sample and hold, multiplexer) which is built immediately below it by using the remaining five active layers. The GEM and the drift electrode window are assembled directly over the chip so the ASIC itself becomes the pixelized anode of a MicroPattern Gas Detector. With this approach, for the first time, gas detectors have reached the level of integration and resolution typical of solid state pixel detectors. Results from the first tests of this new read-out concept are presented. An Astronomical X-Ray Polarimetry application is also discussed.

physics.ins-det↗