Phoswich Detection System Research Articles

Development of a phoswich detector utilizing bismuth germanate crystal scintillator and polyethylene naphthalate scintillation film

In this study, we present the development of a phoswich detector system employing a Bismuth Germanate (BGO) crystal scintillator in combination with a Polyethylene naphthalate (PEN) film plastic scintillator. Phoswich detectors can contribute to various applications, including radiation monitoring, medical imaging, and nuclear physics experiments, due to their ability to discriminate between different types of radiation. The thin PEN film is sensitive to α and β radiation, while the BGO scintillator exhibits good γ radiation detection efficiency. The incident radiation type and its energy can be determined by analyzing the difference in decay times between these two scintillators. This paper presents an analysis of the detector’s response to α, β, and γ radiation, and the particle tagging efficiencies are to be over 99.9%, 92%, and 99.8%, respectively.

On the nature of the absorber in IRAS 09104+4109: the X-ray and mid-infrared view

We present a long (≈76 ks) Chandra observation of IRAS 09104+4109, a hyperluminous galaxy, optically classified as a type 2 active galactic nuclei (AGN) hosted in a cD galaxy in a cluster at z= 0.442. We also report on the results obtained by fitting its broad-band spectral energy distribution. The Compton-thick nature of this source (which has been often referred to as an ‘archetype’ of Compton-thick type 2 quasars) was formerly claimed on the basis of its marginal detection in the Phoswich Detection System (PDS) instrument onboard BeppoSAX, being then disputed using XMM–Newton data. Both Chandra analysis and optical/mid-infrared (IR) spectral fitting are consistent with the presence of heavy (≈1–5 × 1023 cm−2), but not extreme (Compton-thick) obscuration. However, using the mid-IR and the [O iii] emission as proxies of the nuclear hard X-ray luminosity suggests the presence of heavier obscuration. The 54-month Swift BAT map shows excess hard X-ray emission likely related to a nearby (z= 0.009) type 2 AGN, close enough to IRAS 09104+4109 to significantly enhance and contaminate its emission in the early BeppoSAX PDS data.

Development of a phoswich detector system for radioxenon monitoring

Measurement of radioactive xenon in the atmosphere is one of several techniques to detect nuclear weapons testing. For high sensitivity, some existing systems use beta/gamma coincidence detection to suppress background, which is very effective, but increases complexity due to separate beta and gamma detectors that require careful calibration and gain matching. In this paper, we will describe the development and evaluation of a simpler detector system, named PhosWatch, consisting of a CsI(Tl)/BC-404 phoswich well detector, digital readout electronics, and pulse shape analysis algorithms implemented in a digital signal processor on the electronics, and compare its performance to existing multi-detector systems.

The Cosmic X‐Ray Background and the Population of the Most Heavily Obscured AGNs

We report on an accurate measurement of the CXB in the 15-50 keV range performed with the Phoswich Detection System (PDS) instrument aboard the BeppoSAX satellite. We establish that the most likely CXB intensity level at its emission peak (26-28 keV) is ~40 keV/cm2/s/sr, a value consistent with that derived from the best available CXB measurement obtained over 25 years ago with the first High Energy Astronomical Observatory satellite mission (HEAO-1; Gruber et al. 1999), whose intensity, lying well below the extrapolation of some lower energy measurements performed with focusing telescopes, was questioned in the recent years. We find that 90% of the acceptable solutions of our best fit model to the PDS data give a 20-50 keV CXB flux lower than 6.5E-08 erg/cm2/s/sr, which is 12% higher than that quoted by Gruber et al. (1999) when we use our best calibration scale. This scale gives a 20-50 keV flux of the Crab Nebula of 9.22E-09 erg/cm2/s, which is in excellent agreement with the most recent Crab Nebula measurements and 6% smaller than that assumed by Gruber et al. (1999). In combination with the CXB synthesis models we infer that about 25% of the intensity at ~30 keV arises from extremely obscured, Compton thick AGNs (absorbing column density N_H > 1.0E+24 H/cm2), while a much larger population would be implied by the highest intensity estimates. We also infer a mass density of supermassive BHs of ~3.0E+05 Msol/Mpc3. The summed contribution of resolved sources (Moretti et al. 2003) in the 2-10 keV band exceeds our best fit CXB intensity extrapolated to lower energies, but it is within our upper limit, so that any significant contribution to the CXB from sources other than AGNs, such as star forming galaxies and diffuse Warm-Hot Intergalactic Medium (WHIM), is expected to be mainly confined below a few keV.

The puzzling case of GRB 990123: prompt emission and broad-band afterglow modeling

We report on BeppoSAX simultaneous X- andγ-ray observations of the bright γ-ray burst (GRB) 990123. We present the broad-band spectrum of the prompt emission, including optical, X- andγ-rays, confirming the suggestion that the emission mechanisms at low and high frequencies must have different physical origins. In the framework of the standard fire ball model, we discuss the X-ray afterglow observed by the Narrow Field Instruments (NFIs) on board BeppoSAX and its hard X- ray emission up to 60 keV several hours after the burst, detected for about 20 ks by the Phoswich Detection System (PDS). Considering the 2− 10 keV and optical light curves, the 0.1− 60 keV spectrum during the 20 ks in which the PDS signal was present and the 8.46 GHz upper limits, we find that the multi-wavelength observ ations cannot be readily accommodated by basic afterglow models. While the temporal and spectral behavior of the optical afterglow is possibly explained by a synchrotron cooling frequency between the optical and the X-ray energy band during the NFIs observations, in X-rays this assumption only accounts for the slope of the 2− 10 keV light curve, but not for the flatness of the 0.1− 60 keV spectrum. Including the contribution of Inverse Compton (IC) scattering, we solve the problem of the flat X-ray spectrum and justify the hard X-ra y emission; we also suggest that the lack of a significant detec tion of 15− 60 keV emission in the following 75 ks and last 70 ks spectra, should be related to poorer statistics rather than to an important suppression of IC contribution. However, considering also the radio band data, we find the 8.46 GHz upper limits violated. On the other hand, leaving unchanged the emission mechanism requires modifying the hydrodynamics by invoking an ambient medium whose density rises rapidly with radius and by having the shock losing energy. Thus we are left with an open puzzle which requires further inspection.

Confirmation of the Presence of Nonthermal Hard X-Ray Excess in the Cluster A2256 from Two Epoch Observations

After confirmation of the presence of a nonthermal hard X-ray excess with respect to the thermal emission in the Coma Cluster from two independent observations, obtained using the Phoswich Detection System on board BeppoSAX, we also present in this Letter the results of two observations of A2256 performed with a time interval of about 2.5 yr. In both spectra a nonthermal excess is present at a confidence level of ~3.3 σ and ~3.7 σ, respectively. The combined spectrum obtained by adding up the two spectra allows us to measure an excess at the level of ~4.8 σ in the 20-80 keV energy range. The nonthermal X-ray flux is in agreement with the published value of the first observation (Fusco-Femiano et al.) and with that measured by a Rossi X-Ray Timing Explorer observation (Rephaeli & Gruber).

The X-Ray Facility of the Physics Department of the Ferrara University

We will report on the equipment and performance of the X-ray facility of the University of Ferrara. Initially developed to test the PDS (Phoswich Detection System) instrument aboard the BeppoSAX satellite and to perform reflectivity measurements of mosaic crystal samples of HOPG (Highly Oriented Pyrolytic Graphite), with time the facility has been improved and its applications extended. Now these applications include test and calibration of hard X-ray (> 10 keV) detectors, reflectivity measurements of hard X-ray mirrors, reflectivity tests of crystals and X-ray transparency measurements. The facility is being further improved in order to determine the optical axis mosaic crystals in Laue configuration within a project devoted to develop a hard X-ray (> 60 keV) focusing optics (Pisa, A. et al.: in press, Feasibility study of a Laue lens for hard X-rays for space astronomy, SPIE Proc., 5536).

Confirmation of Nonthermal Hard X-Ray Excess in the Coma Cluster from Two Epoch Observations

We report the hard X-ray spectrum of the Coma Cluster obtained using the Phoswich Detection System data of two independent BeppoSAX observations performed with a time interval of about 3 yr. In both the spectra a nonthermal excess with respect to the thermal emission is present at a confidence level of ~3.4 σ. The combined spectrum obtained by adding up the two spectra allows a measurement of the excess at the level of ~4.8 σ at energies above 20 keV. The analysis of the full BeppoSAX data set provides a revised nonthermal X-ray flux that is slightly lower than that previously estimated (Fusco-Femiano et al.) and in agreement with that measured by two Rossi X-Ray Timing Explorer observations. The analysis of the offset fields in our Coma observations provides a possible flux determination of the BL Lac object 1ES 1255+244.

P.2.121 Aripiprazole vs. haloperidol for maintained treatment effect in acute mania

SAX (X-Ray Astronomy Satellite) is a programme jointly developed by the Italian Space Agency (A.S.I.) and the Netherland Agency for Aerospace Programmes (NIVR) devoted to systematic, integrated and comprehensive studies of galactic and extragalactic sources in the energy band 0.1 – 200 KeV. Scientific objectives are: •-|Imaging (with moderate angular resolution of 1 arcmin) and broad band spectroscopy over the energy range from 0.1 to 10 KeV.•-|Spectral measurements, spectroscopy and timing on sources from 3 to 200 KeV.•-|All sky monitoring (2–30 KeV) for the investigation of long time variability and localisation and study of transients.The payload complement includes: a low energy (0.1 – 10 KeV) concentrator/spectrometer (LECS), a medium energy (1–10 KeV) concentrator/spectrometer (MECS) consisting of three units, a high pressure gas scintillation proportional counter (3–120 KeV) (HPGSPC) and a phoswich detector system (15–200 KeV) (PDS), all of which have narrow fields of view and have the optical axis coaligned to the same pointing direction. Two wide field cameras (2–30 KeV), field of view 20°×20° (WFC) which point in diametrically opposed directions perpendicular to the narrow field instrument axis, complete the payload.The SAX mission is, for the Payload and Science, under the responsability of a Consortium of Italian Institutes with the partecipation of the Space Research Institute of Utrecht/SRON-Holland and the Space Science Department of the European Space Agency (E.S.A.).The spacecraft has a total mass of 1200 Kg, is three axis stabilised and it will be placed into a circular orbit at 600 Km with an inclination of two degrees, by an Atlas G-Centaur.SAX, to be launched at the end of 1993, will have a minimum mission life time of two years, extendable up to four years.

Probing the Complex and Variable X-Ray Absorption of Markarian 6 withXMM-Newton

We report on an X-ray observation of the Seyfert 1.5 galaxy Mrk 6 obtained with the EPIC instruments on board XMM-Newton. Archival BeppoSAX Phoswich Detection System data from 18–120 keV were also used to constrain the underlying hard power-law continuum. The results from our spectral analyses generally favor a double partial-covering model, although other spectral models, such as absorption by a mixture of partially ionized and neutral gas, cannot be firmly ruled out. Our best-fitting model consists of a power law with a photon index of Γ = 1.81 and partial covering with large column densities up to NH ~ 1023 cm-2. We also detect a narrow emission line consistent with Fe Kα fluorescence at 6.45 keV with an equivalent width of 93 eV. Joint analyses of XMM-Newton, ASCA, and BeppoSAX data further provide evidence for both spectral variability (a factor of ~2 change in absorbing column) and absorption-corrected flux variations (by ~60%) during the ~4 yr period probed by the observations.

肺中｀２４１´Ａｍに対する肺モニタの計数効率

The counting efficiencies of two lung monitor systems—phoswich detector system and germanium detector system—were measured for lungs and liver loaded with 241Am in the JAERI phantom. It was found that the germanium detector system for 241Am loaded lungs counting gives the full-energy peak predominated by the absorption of the gamma-ray photon in a single photoelectric interaction and is less sensitive to 241Am loaded liver. The 241Am loaded lung activities could be reasonably estimated using germanium detector system rather than phoswich detector system.

BeppoSAXObservations of Synchrotron X‐Ray Emission from Radio Quasars

We present new BeppoSAX Low Energy Concentrator Spectrometer (LECS), Medium Energy Concentrator Spectrometer (MECS), and Phoswich Detector System (PDS) observations of four flat-spectrum radio quasars (FSRQs) having effective spectral indices αro and αox typical of high-energy peaked BL Lac objects. Our sources have X-ray-to-radio flux ratios on average ~70 times larger than "classical" FSRQs and lie at the extreme end of the FSRQ X-ray-to-radio flux ratio distribution. The collected data cover the energy range 0.1-10 keV (observer's frame), reaching ~100 keV for one object. The BeppoSAX band in one of our sources, RGB J1629+4008, is dominated by synchrotron emission peaking at ~2 × 1016 Hz, as also shown by its steep (energy index αX ~ 1.5) spectrum. This makes this object the first known FSRQ whose X-ray emission is not due to inverse Compton radiation. Two other sources display a flat BeppoSAX spectrum (αX ~ 0.7), with weak indications of steepening at low X-ray energies. The combination of BeppoSAX and ROSAT observations, (nonsimultaneous) multifrequency data, and a synchrotron inverse Compton model suggests synchrotron peak frequencies ≈1015 Hz, although a better coverage of their spectral energy distributions is needed to provide firmer values. If confirmed, these values would be typical of "intermediate" BL Lac objects for which the synchrotron and inverse Compton components overlap in the BeppoSAX band. Our sources, although firmly in the radio-loud regime, have powers more typical of high-energy peaked BL Lac objects than of FSRQs, and indeed their radio powers put them near the low-luminosity end of the FSRQ luminosity function. We discuss this in terms of an anticorrelation between synchrotron peak frequency and total power, based on physical arguments, and also as possibly due to a selection effect.

CLC][ITAL]BeppoSAX[/ITAL][/CLC] Observation of NGC 3079

Using the BeppoSAX observatory, we have observed a nearby LINER/Seyfert 2 galaxy, NGC 3079, which is known as an outflow galaxy and a bright H2O maser source. Using the Phoswich Detection System, we have revealed that the NGC 3079 nucleus suffers from a Compton-thick absorption, with a hydrogen column density ~1025 cm-2. After corrected the absorption, the 2-10 keV luminosity becomes 1042-1043 ergs s-1 at a distance of 16 Mpc. It is 2-3 orders of magnitude higher than that observed in the Medium Energy Concentrator Spectrometer band (below 10 keV). We also detected a strong Fe K line at 6.4 keV with an equivalent width of 2.4 keV, which is consistent with the heavy absorption.

Hard X-Ray Emission from the Galaxy Cluster A3667

We report the results of a long BeppoSAX observation of Abell 3667, one of the most spectacular galaxy clusters in the southern sky. A clear detection of hard X-ray radiation up to ~35 keV is reported, while a hard excess above the thermal gas emission is present at a marginal level that should be considered as an upper limit to the presence of nonthermal X-ray radiation. The strong, hard excesses reported by BeppoSAX in Coma and A2256 and the only marginal detection of nonthermal emission in A3667 can be explained in the framework of the inverse Compton model. We argue that the nonthermal X-ray detections in the Phoswich Detection System energy range are related to the radio index structure of halos and relics present in the observed clusters of galaxies.

BeppoSAX observations of three distant, highly luminous clusters of galaxies: RXJ1347-1145, Zwicky 3146 and Abell 2390

We present an analysis of BeppoSAX observations of three clusters of galaxies which are amongst the most luminous in the Universe: RXJ1347-1145, Zwicky 3146 and Abell 2390. Using data from both the Low Energy (LECS) and Medium Energy (MECS) Concentrator Spectrometers, and a joint analysis with the Phoswich Detection System (PDS) data above 10 keV, we constrain, with a relative uncertainty of between 7 and 42 per cent (90 per cent confidence level), the mean gas temperature in the three clus ters. These measurements are checked against any possible non-thermal contribution to the plasma emission and are shown to be robust. We confirm that RXJ1347-1145 has a gas temperature that lies i n the range between 13.2 and 22.3 keV at the 90 per cent confidence level, and is larger t han 12.1 keV at 3� level. The existence of such a hot galaxy cluster at redshift of about 0. 45 implies an upper limit on the mean mass density in the Universe, m, of 0.5. Combining the BeppoSAXestimates for gas temperature and luminosity of the three clusters presented in this work with ASCA measurements available in the literature, we obtain a slope of 2.7 in the L T relation once the physical properties are corrected from th e contamination from the central cooling flows.

BeppoSAXObservations of the Maser Seyfert 2 Galaxy ESO 103‐G35

We have made BeppoSAX observations of the Seyfert 2/1.9 galaxy ESO 103-G35, which contains a nuclear maser source and is known to be heavily absorbed in the X-rays. Analysis of the X-ray spectra observed by BeppoSAX in 1996 October and 1997 October yields a spectral index αE = 0.74 ± 0.07 (Fν ∝ ν), which is typical of Seyfert galaxies and consistent with earlier observations of this source. The strong, soft X-ray absorption has a column density NH of 1.79 ± 0.09 × 1023 cm-2, again consistent with earlier results. The best-fitting spectrum is that of a power law with a high-energy cutoff at 29 ± 10 keV, a cold (E = 6.3 ± 0.1 keV, rest frame), marginally resolved (σ = 0.35 ± 0.14 keV, FWHM ~ 31 ± 12 × 103 km s-1) Fe Kα line with EW 290 eV (1996), and a mildly ionized Fe K edge at 7.37 keV, τ = 0.24. The Kα line and cold absorption are consistent with origin in an accretion disk/torus through which our line of sight passes at a radial distance of ~50 pc. The Fe K edge is mildly ionized, suggesting the presence of ionized gas, probably in the inner accretion disk close to the central source or in a separate warm absorber. The data quality is too low to distinguish between these possibilities, but the edge-on geometry implied by the water maser emission favors the former. Comparison with earlier observations of ESO 103-G35 shows little or no change in spectral parameters while the flux changes by factors of a few on timescales of a few months. The 2-10 keV flux decreased by a factor of ~2.7 between 1996 October and 1997 October with no detectable change in the count rate greater than 20 keV (i.e., the Phoswich Detector System data). Spectral fits to the combined data sets indicate either a significant hardening of the spectrum (αE ~ 0.5) or an approximately constant or delayed response reflection component. The high-energy cutoff (29 ± 10 keV) is lower than the typical ~300 keV values seen in Seyfert galaxies. A significant subset of similar sources would affect current models of the active galactic nucleus contribution to the cosmic X-ray background which generally assume a high-energy cutoff of ~300 keV.

Hard X-Ray Emission from the Galaxy Cluster A2256.

After the positive detection by BeppoSAX of hard X-ray radiation up to approximately 80 keV in the Coma Cluster spectrum, we present evidence for nonthermal emission from A2256 in excess of thermal emission at a 4.6 sigma confidence level. In addition to this power-law component, a second nonthermal component already detected by ASCA could be present in the X-ray spectrum of the cluster, which is not surprising given the complex radio morphology of the cluster central region. The spectral index of the hard tail detected by the Phoswich Detection System on board BeppoSAX is marginally consistent with that expected for the inverse Compton model. A value of approximately 0.05 µG is derived for the intracluster magnetic field of the extended radio emission in the northern regions of the cluster, while a higher value of approximately 0.5 µG could be present in the central radio halo, which is likely related to the hard tail detected by ASCA.

A BeppoSAX Observation of the Merging Cluster Abell 3266.

We present results from a BeppoSAX observation of the rich cluster Abell 3266. The broadband spectrum (2-50 keV) of the cluster, when fitted with an optically thin thermal emission model, yields a temperature of 8.1+/-0.2 keV and a metal abundance of 0.17+/-0.02 in solar units, with no evidence of a hard X-ray excess in the Phoswich Detector System spectrum. By performing a spatially resolved spectral analysis, we find that the projected temperature drops with increasing radius, going from approximately 10 keV at the cluster core to approximately 5 keV at about 1.5 Mpc. Our BeppoSAX temperature profile is in good agreement with the ASCA temperature profile of Markevitch et al. From our two-dimensional temperature map, we find that the gradient is observed in all azimuthal directions. The temperature gradient may have been caused by a recent merger event that was also responsible for a velocity-dispersion gradient measured in the optical band. The projected metal abundance profile and the two-dimensional map are both consistent with being constant.

Hard X-Ray Radiation in the Coma Cluster Spectrum

Hard X-ray radiation has been detected for the first time in the Coma Cluster by BeppoSAX. Thanks to the unprecedented sensitivity of the Phoswich Detection System (PDS) instrument, the source has been detected up to ~80 keV. There is clear evidence (4.5 σ) for nonthermal emission in excess of thermal emission above ~25 keV. The hard excess is very unlikely to be the result of X Comae, the Seyfert 1 galaxy that is present in the field of view of the PDS. A hard spectral tail that is due to inverse Compton scattering on cosmic microwave background photons is predicted in clusters, like Coma, with radio halos. Combining the present results with radio observations, a volume-averaged intracluster magnetic field of ~0.15 μG is derived, while the electron energy density of the emitting electrons is ~7×10−14 ergs cm-3.

Early Results from the Low-Energy Concentrator Spectrometer on-board BeppoSAX

SAX, an acronym for “Satellite Italiano per Astronomia a raggi X”, now renamed “BeppoSAX” in honor of Giuseppe Occhialini, is the first X-ray mission sensitive in the very broad energy range between 0.1 and 300 keV (Boella et al. 1997a). The Narrow Field Instruments (NFI) have approximately 1° fields of view and consist of the imaging low- and medium-energy concentrator spectrometers (LECS, 0.1-10 keV, Parmar et al. 1997; and MECS, 1-10 keV, Boella et al. 1997b), and the non-imaging high pressure gas scintillation proportional counter (HPGSPC, 3-120 keV, Manzo et al. 1997) and Phoswich detector system (PDS, 15-300 keV, Frontera et al. 1997). All the NFI are coaligned and are normally operated simultaneously. In addition, the payload includes two wide field cameras (WFC, 2-30 keV; Jager et al. 1997) which observe in directions perpendicular to the NFI. These allow the detection of X-ray transient phenomena, as well as long-term variability studies.