87 research outputs found
Experimental study on grooved Si and Ge crystals for Laue lens application
An experimental study on the method of indentations for bent crystals to realize a hard X-ray Laue lens has been done. We tested the diffraction properties of indented Si and Ge crystalline plates at European Synchrotron Radiation
Facility (Grenoble, France). The samples were analyzed by diffraction of their (111) planes with hard X-rays from 150 to 600 keV. Crystals have shown significantly high diffraction efficiency, i.e. a Si crystal has exhibited up to 80% at 300 keV. A Ge crystal has confirmed the observation for a Si one, though the diffraction efficiency
was about 60%. In both cases rocking curves showed flat-toped rectangular shapes, which demonstrates that the method of indentations evenly bends the crystals. Moreover, measured angular spread was always very close to the morphological curvature of the sample under investigation, showing that this method offers high reproducibility and, thus, easy control of diffraction properties of the crystals
Experimental evidence of planar channeling in a periodically bent crystal
The usage of a Crystalline Undulator (CU) has been identified as a promising
solution for generating powerful and monochromatic -rays. A CU was
fabricated at SSL through the grooving method, i.e., by the manufacturing of a
series of periodical grooves on the major surfaces of a crystal. The CU was
extensively characterized both morphologically via optical interferometry at
SSL and structurally via X-ray diffraction at ESRF. Then, it was finally tested
for channeling with a 400 GeV/c proton beam at CERN. The experimental results
were compared to Monte Carlo simulations. Evidence of planar channeling in the
CU was firmly observed. Finally, the emission spectrum of the positron beam
interacting with the CU was simulated for possible usage in currently existing
facilities
Development status of the LAUE project
We present the status of LAUE, a project supported by the Italian Space
Agency (ASI), and devoted to develop Laue lenses with long focal length (up to
100 meters), for hard X--/soft gamma--ray astronomy (80-600 keV). Thanks to
their focusing capability, the design goal is to improve the sensitivity of the
current instrumention in the above energy band by 2 orders of magnitude, down
to a few times photons/(cm s keV).Comment: 9 pages, 9 figures, presented at the Space Telescopes and
Instrumentation Symposium in Amsterdam, 2012: Ultraviolet to Gamma Ray
Conference. Published in the Proceedings of the SPIE, Volume 8443, id.
84430B-84430B-9 (2012
Strong Reduction of the Effective Radiation Length in an Axially Oriented Scintillator Crystal
We measured a considerable increase of the emitted radiation by 120 GeV/c electrons in an axially oriented lead tungstate scintillator crystal, if compared to the case in which the sample was not aligned with the beam direction. This enhancement resulted from the interaction of particles with the strong crystalline electromagnetic field. The data collected at the external lines of the CERN Super Proton Synchrotron were critically compared to Monte Carlo simulations based on the Baier-Katkov quasiclassical method, highlighting a reduction of the scintillator radiation length by a factor of 5 in the case of beam alignment with the [001] crystal axes. The observed effect opens the way to the realization of compact electromagnetic calorimeters or detectors based on oriented scintillator crystals in which the amount of material can be strongly reduced with respect to the state of the art. These devices could have relevant applications in fixed-target experiments, as well as in satellite-borne γ telescopes
A high-performance custom photodetection system to probe the light yield enhancement in oriented crystals
Scintillating homogeneous detectors represent the state of the art in
electromagnetic calorimetry. Moreover, the currently neglected crystalline
nature of the most common inorganic scintillators can be exploited to achieve
an outstanding performance boost in terms of compactness and energy resolution.
In fact, it was recently demonstrated by the AXIAL/ELIOT experiments that a
strong reduction in the radiation length inside PWO, and a subsequent
enhancement in the scintillation light emitted per unit thickness, are attained
when the incident particle trajectory is aligned with a crystal axis within
. A SiPM-based system has been developed to directly probe this
remarkable effect by measuring the scintillation light emitted by a PWO sample.
The same concept could be applied to full-scale detectors that would feature a
design significantly more compact than currently achievable and unparalleled
resolution in the range of interest for present and future experiments
Focusing effect of bent GaAs crystals for γ-ray Laue lenses: Monte Carlo and experimental results
We report on results of observation of the focusing effect from the planes (220) of Gallium Arsenide (GaAs) crystals. We have compared the experimental results with the Monte Carlo simulations of the focusing capability of GaAs tiles performed with a dedicated ray-tracer. The GaAs tiles were bent using a lapping process developed at the cnr/imem - Parma (Italy) in the framework of the laue project, funded by ASI, dedicated to build a broad band Laue lens prototype for astrophysical applications in the hard X-/soft γ-ray energy range (80-600 keV). We present and discuss the results obtained from their characterization, mainly in terms of focusing capability. Bent crystals will significantly increase the signal to noise ratio of a telescope based on a Laue lens, consequently leading to an unprecedented enhancement of sensitivity with respect to the present non focusing instrumentation
KLEVER: An experiment to measure BR() at the CERN SPS
Precise measurements of the branching ratios for the flavor-changing neutral
current decays can provide unique constraints on CKM
unitarity and, potentially, evidence for new physics. It is important to
measure both decay modes, and
, since different new physics models affect the rates
for each channel differently. The goal of the NA62 experiment at the CERN SPS
is to measure the BR for the charged channel to within 10%. For the neutral
channel, the BR has never been measured. We are designing the KLEVER experiment
to measure BR() to 20% using a high-energy
neutral beam at the CERN SPS starting in LHC Run 4. The boost from the
high-energy beam facilitates the rejection of background channels such as
by detection of the additional photons in the final state.
On the other hand, the layout poses particular challenges for the design of the
small-angle vetoes, which must reject photons from decays escaping
through the beam exit amidst an intense background from soft photons and
neutrons in the beam. Background from decays in the beam
must also be kept under control. We present findings from our design studies
for the beamline and experiment, with an emphasis on the challenges faced and
the potential sensitivity for the measurement of BR().Comment: 13 pages, 4 figures. Submitted as input to the 2020 update of the
European Strategy for Particle Physics. v2: Included authors unintentionally
omitted in v
How to Detect X-Rays and Gamma-Rays from Space: Optics and Detectors
The measurable quantities of the sky’s light, for any wavelength, are energy, position, arrival time, and polarization. Each of them reveal different information about the science target (e.g. gas dynamics, state and distribution of the matter, temperature, luminosity) and require specific detecting solutions. In the study of X-rays and gamma-rays up to the TeV regime, their absorption by the atmosphere (by 50% at 30 km altitude for 1 MeV photon) requires the development of space applications. The science goals of the mission define which technological benchmark should be maximised (e.g. energy or spatial resolution), but the final design of high energy instruments is the result of a trade-off analysis among the detection specifications, the need for space-borne electronic systems and materials, and the limited resources in mass budget, electrical power, and telemetry rates
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