The paper describes the SIDERALE experiment that was hosted as a piggy back payload on SoRa LDB (Sounding Radar
Long Distance Balloon) mission by the Italian Space Agency (ASI). SIDERALE was aimed at testing a detector for high
energy astrophysics applications based on a 4x4 pixel CZT solid state sensor. An onboard data handling computer, a
mass memory and a power supply units were integrated in SIDERALE. Furthermore an innovative telemetry system BIT
(Bi-directional Iridium Telemetry) was used in order for SIDERALE to be autonomous and independent from the
hosting payload. In the paper a preliminary analysis of flight and scientific data is discussed.
We report on the development of a 3D position sensitive prototype suitable as focal plane detector for Laue lens
telescope. The basic sensitive unit is a drift strip detector based on a CZT crystal, (~19×8 mm<sup>2</sup> area, 2.4 mm thick),
irradiated transversally to the electric field direction. The anode side is segmented in 64 strips, that divide the crystal in 8
independent sensor (pixel), each composed by one collecting strip and 7 (one in common) adjacent drift strips. The drift
strips are biased by a voltage divider, whereas the anode strips are held at ground. Furthermore, the cathode is divided in
4 horizontal strips for the reconstruction of the third interaction position coordinate. The 3D prototype will be made by
packing 8 linear modules, each composed by one basic sensitive unit, bonded on a ceramic layer. The linear modules
readout is provided by a custom front end electronics implementing a set of three RENA-3 for a total of 128 channels.
The front-end electronics and the operating logics (in particular coincidence logics for polarisation measurements) are
handled by a versatile and modular multi-parametric back end electronics developed using FPGA technology.
The importance of hard X-ray astronomy (>10 keV) is now widely recognized. Recently both ESA and NASA have
indicated in their guidelines for the progress of X- and γ-ray astronomy in the next decade the development of new
instrumentation working in the energy range from the keV to the MeV region, where important scientific issues are still
open, exploiting high sensitivity for spectroscopic imaging and polarimetry observations. The development of new
concentrating (e.g. multilayer mirror) telescopes for hard X-rays (10 -100 keV) and focusing instruments based on Laue
lenses operating from ~60 keV up to a few MeV is particularly challenging. We describe the design of a threedimensional
(3D) depth-sensing position sensitive device suitable for use as the basic unit of a high efficiency focal
plane detector for a Laue lens telescope. The sensitive unit is a drift strip detector based on a CZT crystal, (10×10 mm<sup>2</sup>
area, 2.5 mm thick), irradiated transversally to the electric field direction. The anode is segmented into 4 detection cells,
each comprising one collecting strip and 8 drift strips. The drift strips are biased by a voltage divider, whereas the anode
strips are held at 0 V. The cathode is divided in 4 horizontal strips for the reconstruction of the Z interaction position.
The 3D prototype will be made by packing 8 linear modules, each composed of 2 basic sensitive units, bonded onto a
ceramic layer together with the readout electronics.
The science drivers for a new generation soft gamma-ray mission are naturally focused on the detailed study of
the acceleration mechanisms in a variety of cosmic sources. Through the development of high energy optics in the
energy energy range 0.05-1 MeV it will be possible to achieve a sensitivity about two orders of magnitude better
than the currently operating gamma-ray telescopes. This will open a window for deep studies of many classes of
sources: from Galactic X-ray binaries to magnetars, from supernova remnants to Galaxy clusters, from AGNs
(Seyfert, blazars, QSO) to the determination of the origin of the hard X-/gamma-ray cosmic background, from
the study of antimatter to that of the dark matter. In order to achieve the needed performance, a detector with
mm spatial resolution and very high peak efficiency is needed. The instrumental characteristics of this device
could eventually allow to detect polarization in a number of objects including pulsars, GRBs and bright AGNs. In
this work we focus on the characteristics of the focal plane detector, based on CZT or CdTe semiconductor sensors
arranged in multiple planes and viewed by a side detector to enhance gamma-ray absorption in the Compton
regime. We report the preliminary results of an optimization study based on simulations and laboratory tests,
as prosecution of the former design studies of the GRI mission which constitute the heritage of this activity.
How structures of various scales formed and evolved from the early Universe up to present time is a fundamental
question of astrophysics. EDGE will trace the cosmic history of the baryons from the early generations of massive
stars by Gamma-Ray Burst (GRB) explosions, through the period of galaxy cluster formation, down to the very low
redshift Universe, when between a third and one half of the baryons are expected to reside in cosmic filaments undergoing
gravitational collapse by dark matter (the so-called warm hot intragalactic medium). In addition EDGE, with its
unprecedented capabilities, will provide key results in many important fields. These scientific goals are feasible with a
medium class mission using existing technology combined with innovative instrumental and observational capabilities
by: (a) observing with fast reaction Gamma-Ray Bursts with a high spectral resolution (R ~ 500). This enables the study
of their (star-forming) environment and the use of GRBs as back lights of large scale cosmological structures; (b)
observing and surveying extended sources (galaxy clusters, WHIM) with high sensitivity using two wide field of view
X-ray telescopes (one with a high angular resolution and the other with a high spectral resolution). The mission concept
includes four main instruments: a Wide-field Spectrometer with excellent energy resolution (3 eV at 0.6 keV), a Wide-
Field Imager with high angular resolution (HPD 15") constant over the full 1.4 degree field of view, and a Wide Field
Monitor with a FOV of <sup>1</sup>/<sub>4</sub> of the sky, which will trigger the fast repointing to the GRB. Extension of its energy response
up to 1 MeV will be achieved with a GRB detector with no imaging capability. This mission is proposed to ESA as part
of the Cosmic Vision call. We will briefly review the science drivers and describe in more detail the payload of this
The success of the SWIFT/BAT and INTEGRAL missions has definitely opened a new window for follow-up
and deep study of the transient gamma-ray sky. This now appears as the access key to important progresses in
the area of cosmological research and deep understanding of the physics of compact objects. To detect in near
real-time explosive events like Gamma-Ray bursts, thermonuclear flashes from Neutron Stars and other types of
X-ray outbursts we have developed a concept for a wide-field gamma-ray coded mask instrument working in the
range 8-200 keV, having a sensitivity of 0.4 ph cm<sup>−2</sup> s<sup>−1</sup> in 1 s (15-150 keV) and arcmin location accuracy over
a sky region as wide as 3 sr. This scientific requirement can be achieved by means of two large area, high spatial
resolution CZT detection planes made of arrays of relatively large (~ 1 cm<sup>2</sup>) crystals, which are in turn read
out as matrices of smaller pixels. To achieve such a wide Field-Of-View the two units can be placed at the sides
of a S/C platform serving a payload with a complex of powerful X-ray instruments, as designed for the EDGE
mission. The two units will be equipped with powerful signal read out system and data handling electronics,
providing accurate on-board reconstruction of the source positions for fast, autonomous target acquisition by
the X-ray telescopes.
In the context of R&D studies financed by the Italian Space Agency (ASI), a feasibility study to evaluate the Italian
Industry interest in medium-large scale production of enhanced CZT detectors has been performed by an Italian
Consortium. The R&D investment aims at providing in-house source of high quality solid state spectrometers for Space
Astrophysics applications. As a possible spin-off industrial applications to Gamma-ray devices for non-destructive
inspections in medical, commercial and security fields have been considered by ASI. The short term programme mainly
consists of developing proprietary procedures for 2-3" CZT crystals growth, including bonding and contact philosophy,
and a newly designed low-power electronics readout chain. The prototype design and breadboarding is based on a fast
signal AD conversion with the target in order to perform a new run for an already existing low-power (<0.7 mW/pixel)
ASIC. The prototype also provides digital photon energy reconstruction with particular care for multiple events and
polarimetry evaluations. Scientific requirement evaluations for Space Astrophysics Satellite applications have been
carried out in parallel, targeted to contribute to the ESA Cosmic Vision 2015-2025 Announcement of Opportunity.
Detailed accommodation studies are undergoing, as part of this programme, to size a "Large area arcsecond angular
resolution Imager" for the Gamma Ray Imager satellite (Knödlseder et al., this conference).and a new Gamma-ray Wide
Field Camera for the "EDGE" proposal (Piro et al., this conference). Finally, an extended market study for cost analysis
evaluation in view of the foreseen massive detector production has been performed.
The development of formation flying technology in space has opened a new window for astronomy at hard X-γ-ray
wavelenghts, allowing observations with unprecedented angular resolution (location accuracy of the order of few
arcsec). This has stimulated the development of new concepts for imaging instruments: on one side, the focusing
telescopes like γ-ray lens, using small,well shielded detector volumes, on the other side very large area γ-ray
imagers, both allowing a big step in sensitivity. We report on a study for the concept of a large area (1 square
meter), narrow field coded mask telescope with arcsec imaging capability, based on CZT detector technology
and active collimation system, made of Si microstrip detector modules and operating in the energy band 15-500
keV. Feasibility and performance characteristics are discussed as well as possible geometric configurations and
background suppression schemes, in the light of data obtained from INTEGRAL/IBIS and other CdTe/CZT
instruments currently in space.
We present a mission designed to address two main themes of the ESA Cosmic Vision Programme: the Evolution of the Universe and its Violent phenomena. ESTREMO/WFXRT is based on innovative instrumental and observational approaches, out of the mainstream of observatories of progressively increasing area, i.e.: Observing with fast reaction transient sources, like GRB, at their brightest levels, thus allowing high resolution spectroscopy. Observing and surveying through a X-ray telescope with a wide field of view and with high sensitivity extended sources, like cluster and Warm Hot Intragalactic Medium (WHIM). ESTREMO/WFXRT will rely on two cosmological probes: GRB and large scale X-ray structures. This will allow measurements of the dark energy, of the missing baryon mass in the local universe, thought to be mostly residing in outskirts of clusters and in hot filaments (WHIM) accreting onto dark matter structures, the detection of first objects in the dark Universe, the history of metal formation. The key asset of ESTREMO/WFXRT with regard to the study of Violent Universe is the capability to observe the most extreme objects of the Universe during their bursting phases. The large flux achieved in this phase allows unprecedented measurements with high resolution spectroscopy. The mission is based on a wide field X-ray/hard X-ray monitor, covering >1/4 of the sky, to localize transients; fast (min) autonomous follow-up with X-ray telescope (2000 cm<sup>2</sup>) equipped with high resolution spectroscopy transition edge (TES) microcalorimeters (2eV resolution below 2 keV) and with a wide field (1°) for imaging with 10" resolution (CCD) extended faint structures and for cluster surveys. A low background is achieved by a 600 km equatorial orbit. The performances of the mission on GRB and their use as cosmological beacons are presented and discussed.
The outstanding scientific performances of IBIS, Imager on Board INTEGRAL, has encouraged preliminary feasibility studies on new Gamma Ray instruments. We considered both a Wide Field Camera for transient event detection and fast automatic sky localisation and a high resolution imager. According to the basic scientific requirements, i.e. to operate with good sensitivity (1mCrab/day) and spatial resolution (from arcmin to arcsec) on a wide energy range (5 to 500 keV), these studies consider large detector area (from 1 to several m<sup>2</sup>) and a high number (~50000) of thick (≥ 5mm) pixels. Recent achievements already obtained by INTEGRAL, and initially showed by SWIFT, have validated the CdTe/CZT detector performances in terms of good spatial resolution, detection efficiency, energy resolution and low noise at room temperature. We have started a study to solve peculiar problems affecting this kind of detectors (e.g. response dependent on the interaction depth and multiple hit events) using a digital approach to photon reconstruction. This also facilitates operations like pixel to pixel equalisation and background rejection. The detector electronic chain thus includes a minimal analog stage for charge pre-amplification, coupled to a flash ADC for waveform digitalisation at a high time resolution sampling, and a powerful, FPGA based digital processing unit, devoted to waveform elaboration. Such a design should also help in optimising the telemetry flux and allow polarimetry evaluation on multiple events.
A Bismuth Germanate (BGO) 'veto' shield surrounds on five faces the detector planes of the IBIS instrument on-board the satellite INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory). The Veto System provides anti-coincidence signals to the two imager layers covering the energy range from 20 keV to 10 MeV. The area to be shielded is about 8000 cm<SUP>2</SUP>, and with a shield thickness of 20 mm, this leads to a total BGO crystal weight of about 115 kg. This paper describes the shield design, and how some scientific and engineering requirements are implemented. Also results from tests with the Engineering Model are presented. Particular emphasis is given to the electronic signal chain, and its response to overload particles, mainly high energy protons, expected in the INTEGRAL orbit (Elliptic Earth Orbit with 72 h period). The overload response has been studied in detail both with a built-in Light Emitting Diode (LED) in the laboratory, and at a proton beam facility. Based on the lab measurements the expected blinding of the shield in-orbit is around 1%. This is obtained with a simple, but optimized chain, consisting of a front-end amplifier and a bi-polar shaper, that provides input to the trigger generator. Results from beam tests with proton energies from 60 to 300 MeV are reported, and it is demonstrated that the proton pulses in terms of amplitude, shape and duration are very similar to the simulated ones, and thus confirm the expected system response.
A novel low energy astronomical gamma-ray detector is being developed for future satellite missions. Recent advances in the technology of photodiodes and small, low noise amplifier circuits have meant that more compact detectors can be assembled in a complex array in order to give a 3-D position reconstruction capability. In a mask-detector telescope this capability is potentially very useful since it allows the reconstruction of the path of the incident gamma rays making it valuable both for imaging and background rejection. A small prototype of a 3-D detector has been realized for test in a balloon mission. The detector is based on a 12 X 8 array of position sensitive CsI(T1) bars, typically 15 cm long with 1.3 X 1.3 cm cross section, viewed at each end by photodiodes. The detector includes four 1.3 X 1.3 X 2.5 cm CsI(T1) scintillators located above the main array in order to evaluate the low energy response of the imager. The detector constitutes an active block of 2400 cm3 of scintillator that can operate in the 0.2 - 10 MeV energy range. The energy resolution is 13% at 662 keV and the positional resolution is of the order of 1.5 cm in each dimension. An active shield of CSI(T1) and plastic scintillators surrounds the bar detector. The overall experiment is briefly described in general and preliminary results of laboratory tests are presented.
Analytical considerations and test results bearing on the performance of a CsI(Tl) scintillating crystal coupled with a photodiode when used as a gamma-ray spectrometer are addressed. Laboratory test results on a number of CsI(Tl) bars with different sizes, diffusive coatings, and preamplifier designs are presented. A suitable event selection electronic logic design is shown which reduces the effect of noise on the count rate while retaining the desired energy threshold.
The capabilities of the European Photon Imaging Camera (EPIC), the main instrument of ESA's 'Cornerstone' mission in X-ray astronomy with multiple mirrors (XMM), are discussed. The CCD characteristics, spatial resolution, energy bandpass and faint source sensitivity, spectral resolution and sensitivity, and timing capability are addressed, and the scientific rationale of the EPIC is summarized. The EPIC instrument system concept is briefly described.