Filippo Celi

The atmospheric nightglow in the 300–400 nm wavelength: Results by the balloon-borne experiment “BABY”

Abstract The balloon-borne experiment, named BAckground BYpass (BABY) belongs to a wider program that has as its final goal the detection and study of high-energy cosmic rays from space (satellite, Space Station). An information of fundamental importance for this class of projects concerns the nighttime background light. The instrument designed to detect fluorescence photons is basically composed of two collimated photomultipliers: a single photon-counting PMT and a charge integration PMT. We briefly report the details of the design, operation and performance of the detector, which was designed and completely built at the IFCAI–CNR Institute in Palermo. Preliminary analysis and results of the nocturnal background in the range of 300– 400 nm are presented for the whole duration of the flight during the 1998 Mediterranean balloon flight campaign. A substantial part of the flight was at night over the sea.

Measurements of spectral and position resolution on a 16x16 pixel CZT imaging hard x-ray detector

Cadmium zinc telluride (CZT) pixel detectors show very good spectral and spatial resolution and are suitable for use in compact hard X-ray sensors operated without cryogenics. One of the more interesting astrophysical application is their use as focal plane detectors for multilayer hard X-ray telescopes operating in the 15 - 70 keV energy band. Here we report on results obtained using a 16 x 16 CZT pixel detector (10 x 10 x 1 mm3 single crystal) with 500 μm pixels operated at room temperature using standard commercial electronics. The results clearly show that the use of small pixels is effective in reducing one of the major drawbacks of CZT planar detectors i.e. the considerable amount of charge loss, due to hole trapping, which gives rise to a reduced energy resolution and a low energy tail in the pulse-height spectra.

AIR WATCH: air-induced fluorescence by radiation laboratory experiments

We report preliminary measurements of the air UV fluorescence light yield as a function of pressure using as a stimulus hard x-rays. For comparison measurements in pure nitrogen are also reported. Knowledge of the air UV fluorescence light yield induced by hard x-rays is needed in order to evaluate the capability to detect, in an AIRWATCH FROM SPACE experiment, Gamma Ray Burst (GRB) events. The experiment was carried out a the LAX x-ray facility in Palermo, by using an high flux collimated x-ray photon beam. The experimental result indicate that the fluorescence yield is inversely proportional to the filling pressure. At pressures below 30 mbar, corresponding to the value for the upper atmospheric layers in which the X and gamma ray photons of the GRBs are absorbed, about 0.1 percent of the total energy of a GRB is transformed in UV photons. This makes possible the observation of the GRBs with the technique proposed in the AIRWATCH FROM SPACE experiment.

Spectroscopic performances and electron transport properties in a 16x16-pixel CZT imaging hard-X-ray detector

Cadmium zinc telluride (CZT) pixel detectors show very good spectral and spatial resolution and are suitable for use in compact hard X-ray sensors operated without cryogenics. One of the more appealing astrophysical applications is their use as focal plane detectors for multilayer hard X-ray telescopes operating in the (10 - 80) keV energy band. This paper reports experimental results obtained from two 16x16 pixellated CZT detectors (10x10x1 mm3 and 10x10x2 mm3 single crystals) with 450x450 μm2 pixel operated at room temperature using standard commercial read-out electronics. We have investigated about energy resolution and material properties of both detectors. Both arrays gave similar results showing an energy resolution less then 5%@59.5 keV and a good material uniformity. The good energy resolution of both detectors demonstrates as the pixellated anode structure reduces (small pixel effect) the incomplete charge collection due to severe hole trapping typically presents in CZT crystals. A calibration curve, obtained using three different energies, shows a linear response of the detectors.

Air fluorescence efficiency measurements for AIRWATCH based mission: Experimental set-up

In the framework of the AIRWATCH project we present an experimental set-up to measure the efficiency of the UV fluorescence production of the air using hard X-ray stimulus. The measures will be carried out at different pressure and temperature to emulate the same condition of the upper layers of the atmosphere where X-ray and gamma ray photons of Gamma Ray Bursts are absorbed.

Performance characteristics of the scientific model of the medium energy concentrator spectrometer on board the x-ray astronomy satellite SAX

The scientific model of the SAX Medium Energy Gas Scintillation Proportional Counter has been tested at the PANTER X-ray facility in Munich. For part of the test the detector has been coupled to a representative reduced model of the SAX concentrators model. The results from the tests on both the detector and the detector/mirror assembly are within the expected performances. We have measured an energy resolution of about 8% (FWHM) and an angular resolution (on axis) of 1.3 arcminutes (HPR) at 6.4 keV.

Characteristics and Performance of the GAW Experiment for a Large Field of View Cerenkov Gamma-ray Telescope

One of the intents of the ground-based gamma-ray astronomy is to obtain a sky survey in the TeV energy region, and nowadays this target can be reached with giant arrays of telescopes, which however need many pointings due to their small field of view. A different approach is on the basis of GAW, acronym for Gamma Air Watch, an array of three relatively small Cerenkov telescopes which differentiate from the existing and presently planned telescopes for two main features: the adoption of a refractive optics system as light collector with a large field of view capability, and the use of single photoelectron counting as detector working mode. During a first phase, the focal plane detector of the GAW telescopes will be implemented in a reduced configuration to test the sensitivity and to prove the feasibility of the method; then the focal plane will be enlarged to cover a field of view of 24°×24°; pointing along different North-South directions, GAW would reach a survey of 360°×60° region of the sky. In this paper, the GAW expected performance are reported as evaluated in the case of the Calar Alto site, Spain, 2150 m a.s.l., where GAW is planned to be located within 2007. GAW is a collaboration effort of Research Institutes in Italy, Portugal and Spain.

Atmospheric Background Measurement in the 300–400 nm Band with a Balloon Borne Experiment during a Nocturnal Flight

The balloon borne experiment, named BABY (BAckground BYpass)belongs to a wider program, AIRWATCH-OWL, intended for theobservation of high energy Cosmic Rays from space, detecting thefaint UV fluorescence light emitted by the atmospheric Nitrogen asfinal result of a complex hadronic cascade. In this framework, oneof the fundamental information concern the knowledge of thebackground level. This is one of the main parameters thatcontribute to the sensitivity of any kind of instrument. Theapparatus used for the BABY experiment was designed and completelybuilt at the IFCAI-CNR in Palermo. The instrument is composed bytwo filtered and collimated photomultipliers (PMT) that detect theUV light in the 300–400 nm wavelength. We report a briefdescription of the design of the detector and the results comingfrom a preliminary analysis of the data taken during a nocturnalover-sea observation.

High-pressure gas-scintillation proportional counter: performance characteristics of the scientific model

We present the performance characteristics of a High Tech scientific model of the High Pressure Gas Scintillation Proportional Counter (HPGSPC) that has been developed as a prototype detector for the Italian X-ray Astronomy satellite SAX. We give some insight on the technology employed and we give an outline of one of the main areas of interest for the HPGSPC in the framework of the SAX mission.

The high-pressure gas scintillation propertional counter on board the Italian X-ray astronomy satellite SAX

SummaryA description of one of the experiments on board the Italian X-ray Astronomy Satellite SAX is presented. The principle of operation and the technological problems are discussed in some detail.RiassuntoUno degli esperimenti a bordo del satellite italiano per Astronomia in raggi X è descritto. Vengono dati alcuni dettagli sul principio di funzionamento e sui problemi tecnologici affrontati.РезюмеВ статье описывается один из экспериментов на борту итальянского спутника SAX, предназначенного для рентгеновской астрономии. Подробно обсуждаются принципы действия и технологические проблемы.