118 research outputs found
Quantum Memory Process with a Four-Level Atomic Ensemble
We examine in detail the quantum memory technique for photons in a double
atomic ensemble in this work. The novel application of the present
technique to create two different quantum probe fields as well as entangled
states of them is proposed. A larger zero-degeneracy class besides dark-state
subspace is investigated and the adiabatic condition is confirmed in the
present model. We extend the single-mode quantum memory technique to the case
with multi-mode probe fields, and reveal the exact pulse matching phenomenon
between two quantized pulses in the present system.Comment: 7 pages, 1 figure, to appear in Euro. Phys. J.
System Response Kernel Calculation for List-mode Reconstruction in Strip PET Detector
Reconstruction of the image in Positron Emission Tomographs (PET) requires
the knowledge of the system response kernel which describes the contribution of
each pixel (voxel) to each tube of response (TOR). This is especially important
in list-mode reconstruction systems, where an efficient analytical
approximation of such function is required. In this contribution, we present a
derivation of the system response kernel for a novel 2D strip PET.Comment: 10 pages, 2 figures; Presented at Symposium on applied nuclear
physics and innovative technologies, Cracow, 03-06 June 201
Analysis framework for the J-PET scanner
J-PET analysis framework is a flexible, lightweight, ROOT-based software
package which provides the tools to develop reconstruction and calibration
procedures for PET tomography. In this article we present the implementation of
the full data-processing chain in the J-PET framework which is used for the
data analysis of the J-PET tomography scanner. The Framework incorporates
automated handling of PET setup parameters' database as well as high level
tools for building data reconstruction procedures. Each of these components is
briefly discussed.Comment: 6 pages, 1 figur
A novel method for calibration and monitoring of time synchronization of TOF-PET scanners by means of cosmic rays
All of the present methods for calibration and monitoring of TOF-PET scanner
detectors utilize radioactive isotopes such as e.g. Na or Ge,
which are placed or rotate inside the scanner. In this article we describe a
novel method based on the cosmic rays application to the PET calibration and
monitoring methods. The concept allows to overcome many of the drawbacks of the
present methods and it is well suited for newly developed TOF-PET scanners with
a large longitudinal field of view. The method enables also monitoring of the
quality of the scintillator materials and in general allows for the continuous
quality assurance of the PET detector performance.Comment: 10 pages, 7 figure
Beam profile investigation of the new collimator system for the J-PET detector
Jagiellonian Positron Emission Tomograph (J-PET) is a multi-purpose detector
which will be used for search for discrete symmetries violations in the decays
of positronium atoms and for investigations with positronium atoms in
life-sciences and medical diagnostics. In this article we present three methods
for determination of the beam profile of collimated annihilation gamma quanta.
Precise monitoring of this profile is essential for time and energy calibration
of the J-PET detector and for the determination of the library of model signals
used in the hit-time and hit-position reconstruction. We have we have shown
that usage of two lead bricks with dimensions of 5x10x20 cm^3 enables to form a
beam of annihilation quanta with Gaussian profile characterized by 1 mm FWHM.
Determination of this characteristic is essential for designing and
construction the collimator system for the 24-module J-PET prototype.
Simulations of the beam profile for different collimator dimensions were
performed. This allowed us to choose optimal collimation system in terms of the
beam profile parameters, dimensions and weight of the collimator taking into
account the design of the 24 module J-PET detector.Comment: 14 pages, 9 figure
Application of Compressive Sensing Theory for the Reconstruction of Signals in Plastic Scintillators
Compressive Sensing theory says that it is possible to reconstruct a measured
signal if an enough sparse representation of this signal exists in comparison
to the number of random measurements. This theory was applied to reconstruct
signals from measurements of plastic scintillators. Sparse representation of
obtained signals was found using SVD transform.Comment: 7 pages, 3 figures; Presented at Symposium on applied nuclear physics
and innovative technologies, Cracow, 03-06 June 201
Hit time and hit position reconstruction in the J-PET detector based on a library of averaged model signals
In this article we present a novel method of hit time and hit position
reconstruction in long scintillator detectors. We take advantage of the fact
that for this kind of detectors amplitude and shape of registered signals
depends strongly on the position where particle hit the detector. The
reconstruction is based on determination of the degree of similarity between
measured and averaged signals stored in a library for a set of well-defined
positions along the scintillator. Preliminary results of validation of the
introduced method with experimental data obtained by means of the double strip
prototype of the J-PET detector are presented
Searches for discrete symmetries violation in ortho-positronium decay using the J-PET detector
In this paper we present prospects for using the J-PET detector to search for
discrete symmetries violations in a purely leptonic system of the positronium
atom. We discuss tests of CP and CPT symmetries by means of ortho-positronium
decays into three photons. No zero expectation values for chosen correlations
between ortho-positronium spin and momentum vectors of photons would imply the
existence of physics phenomena beyond the Standard Model. Previous measurements
resulted in violation amplitude parameters for CP and CPT symmetries consistent
with zero, with an uncertainty of about 10-3. The J-PET detector allows to
determine those values with better precision thanks to a unique time and
angular esolution combined with a high geometrical acceptance. Achieving the
aforementioned is possible due to application of polymer scintillators instead
of crystals as detectors of annihilation quanta.Comment: in Nukleonika 201
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