•Different solidification methods for PCMs’ supercooling suppression were analyzed.•Seeding induced reproducible and controlled heat release from supercooled PCM.•Use of 1 wt% additives is sufficient ...to induce reproducible heat release for PCMs.•Electrical discharge led to controlled heat release with specific electrodes.•Use of ultrasound induced controlled heat release, favored for low frequencies.
Supercooling is an undesired property of phase change materials due to the poorly predictable occurrence of crystallization during cooling. For such situations, the stored latent heat cannot be recovered which can be an issue for temperature-controlled applications. This review illustrates the techniques used for triggering crystallization in phase change materials having a supercooling property. The development of triggering devices should constitute a breakthrough for heat on demand applications, as heat can be released even when the temperature drops far below the liquidus temperature. Several techniques appear to be promising for nucleation triggering. They have been classified into two categories: passive (reduction of supercooling) or active (triggering of crystallization on demand) devices. They were accurately investigated for water freezing for: meteorological comprehension, food preservation or the pharmaceutical industry. In this paper, several nucleating agents (passive) have been explored, and most of them, added by 1 wt%, can decrease the supercooling degree by more than 90%. In addition, the heat would be immediately released on demand from a supercooled material by the use of seeding or electrofreezing (active methods). Solidification can also be externally triggered by the application of high pressure or ultrasonic waves (active). In addition to the analysis of the efficiency of the different techniques in terms of supercooling reduction, this review also discusses the solidification process at a microscopic scale.
In this article, we propose a novel image reconstruction technique for three-gamma (3-<inline-formula> <tex-math notation="LaTeX"> {\gamma } </tex-math></inline-formula>) imaging systems that aims at ...reaching high image quality with a low statistics. The proposed approach is based on the utilization of a (<inline-formula> <tex-math notation="LaTeX"> {\beta +} </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">{\gamma } </tex-math></inline-formula>) emitter and a liquid xenon (LXe) camera, the Xenon Medical Imaging System 2 (XEMIS2), that is currently being manufactured. The third gamma emitted is more energetic than the two 511-keV photons and interacts mostly through Compton scattering in LXE; therefore, we utilize the interactions' position and the deposited energy to define a Compton cone that gives the direction from where the third gamma was emitted. The intersection point between the cone and the two coincidence photons' lines of response (LOR) is the center of the probability distribution function (PDF), a resolution model similar to that of time-of-flight (TOF)-positron emission tomography (PET). The third gamma's information is used to narrow the LOR portion employed during reconstruction. In this article, we show reconstruction results from simulation using highly realistic Geant4 Application for Emission Tomography (GATE) Monte Carlo simulation of the imaging device and a NEMA-like phantom.
Phase change materials, such as sodium acetate trihydrate, are efficient materials for Latent Heat Thermal Energy Storage (LHTES) according to their interesting thermal properties (high latent heat ...and specific heat). Their main drawback is a large degree of supercooling, up to 90 K for sodium acetate trihydrate, where the material may remain liquid below its melting point. However, heat could be released if the solidification could be triggered. For a better understanding of how heat is discharged after an initial cooling by external water flow and a solidification induction by seeding, the temperature was experimentally recorded to measure the residual solidification plateau duration. This experiment was repeated for different nucleation temperatures and fit well with the theoretical predictions. An increase of 90% in the solidification duration was observed when the supercooling degree dropped from 35 to 8 K. Thanks to an original experimental bench, this temperature record has been compared with a fully new method allowing the measurements of the material's opacification throughout the solidification process. Finally, two different opacification behaviors were observed for supercooling degrees below and above 20 K.
•Solidification behaviors from different supercooling degrees were explored.•The heat release duration was deeply influenced by the supercooling degree.•The T-history method by thermocouple was consistent with theoretical predictions.•Laser opacification method is reliable when considering a low supercooling degree.
We report the studies and optimization of scintillation light measurements in an updated version of the XEMIS1 prototype for the development of the XEMIS2 camera. A novel monolithic liquid xenon ...Compton camera, named XEMIS2 (XEnon Medical Imaging System), attempts to achieve low-activity small-animal imaging using the 3-gamma imaging technique. This emerging detector relies on the time projection chamber technique: it will be able to perform a simultaneous detection of the three γ-rays emitted by a specific radionuclide, such as scandium-44, and to produce a good quality image with a remarkable diminution of radiopharmaceutical activity at the same time. Vacuum Ultraviolet (VUV) scintillation light and ionization charge carriers generated from the recoiling particles within the detector are detected and used to reconstruct the interaction position and deposited energy. A cost-effective self-triggering scintillation signal read-out and data acquisition (DAQ) system has been developed to achieve a continuous data read-out with negligible electronics dead time. The DAQ prototype has been installed and qualified in an updated version of the XEMIS1 detector. It reaches the performance specifications in scintillation light measurements. Moreover, scintillation signals can also be used for the virtual segmentation of the monolithic detection volume through the matching algorithm of the scintillation and ionization signals based on the Light Collection Map (LCM). This spatial pre-localization of the physical events, called the virtual fiducialization of the active volume, is used to lower the detector occupancy rate when the administered activity is increased to lessen the examination time. The XEMIS1 experimental LCMs indicate that each PMT owns an individual field of view so as to segment the active volume virtually. The preparation work for the XEMIS2 camera operation has been completed in the updated XEMIS1 detector while the XEMIS2 scintillation light measurement system is under commissioning in Nantes Centre Hospitalier Universitaire.
•The XEMIS2 camera oriented to the whole-body small animal 3-gamma medical imaging is presented.•The XEMIS2 system is a monolithic liquid xenon Compton camera with a 24 cm axial field of view.•A cost-effective 16-channel self-triggering scintillation signal front-end read-out electronics named XSRETOT is reported.•The XEMIS1 experimental light collection maps can be used for the virtual segmentation of the monolithic detection volume.
XEMIS2: A liquid xenon detector for small animal medical imaging Gallego Manzano, L.; Abaline, J.M.; Acounis, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2018, Letnik:
912
Journal Article
Recenzirano
Odprti dostop
We report a new liquid xenon Compton camera, called XEMIS2 (XEnon Medical Imaging System), developed to image for the first time small animals using 3γ imaging. This technique proposes an alternative ...to reduce the administered radiopharmaceutical activity while preserving diagnostic image quality using liquid xenon as detection medium. Given the success of its predecessor, a small dimension liquid xenon time projection chamber called XEMIS1, we are currently building a larger scale detector for preclinical applications. This second prototype, XEMIS2, is a single phase liquid xenon cylindrical camera with a large axial field of view for full-body small animal imaging. XEMIS2 holds around 200 kg of xenon and it has been designed to enable high-efficiency and simultaneous detection of the three γ-rays emitted by a 44Sc radionuclide. The innovative geometry of XEMIS2 will allow to discriminate and measure the position and deposited energy of most Compton interactions inside the detector. In order to manage such a large quantity of xenon, an innovative high-pressure subsystem known as ReStoX has been developed and successfully qualified. ReStoX allows to maintain the xenon in liquid state at the desired temperature and pressure, transfer the xenon into XEMIS2 and store it during long term periods. XEMIS2 will be installed at a non controlled radioactive area of Nantes Hospital. The goal is to evaluate image quality of a 20 min whole-body preclinical exam with an injected activity of 20 kBq.
•The first 3 gamma whole-body small animal scanner is presented.•The XEMIS2 camera is a single-phase liquid xenon detector with a 24 cm axial field of view.•A dedicated 32-channels low power circuit called XTRACT is described.•ReStoX is an advanced cryogenic system developed to liquefy, recover and store the xenon.•A reconstructed image using the innovative 3 gamma reconstruction algorithm is reported.
Gravity assisted recovery of liquid xenon at large mass flow rates Virone, L.; Acounis, S.; Beaupère, N. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2018, Letnik:
893
Journal Article
Recenzirano
Odprti dostop
We report on a liquid xenon gravity assisted recovery method for nuclear medical imaging applications. The experimental setup consists of an elevated detector enclosed in a cryostat connected to a ...storage tank called ReStoX. Both elements are part of XEMIS2 (XEnon Medical Imaging System): an innovative medical imaging facility for pre-clinical research that uses pure liquid xenon as detection medium. Tests based on liquid xenon transfer from the detector to ReStoX have been successfully performed showing that an unprecedented mass flow rate close to 1 ton per hour can be reached. This promising achievement as well as future areas of improvement will be discussed in this paper.
XEMIS: A liquid xenon detector for medical imaging Gallego Manzano, L.; Bassetto, S.; Beaupere, N. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2015, Letnik:
787
Journal Article
Recenzirano
A new medical imaging technique based on the precise 3D location of a radioactive source by the simultaneous detection of 3 gamma rays has been proposed by Subatech laboratory. To take advantage of ...this novel technique a detection device based on a liquid xenon Compton telescope and a specific (beta(+), gamma) emitter radionuclide, Sc-44, are required. A first prototype of a liquid xenon time projection chamber called XEMIS1 has been successfully developed showing very promising results for the energy and spatial resolutions for the ionization signal in liquid xenon, thanks to an advanced cryogenics system, which has contributed to a high liquid xenon purity with a very good stability and an ultra-low noise front-end electronics (below 100 electrons) operating at liquid xenon temperature. The very positive results obtained with XEMIS1 have led to the development of a second prototype for small animal imaging. XEMIS2, which is now under development. To study the feasibility of the 3 gamma imaging technique and optimize the characteristics of the device, a complete Monte Carlo simulation has been also carried out. A preliminary study shows very positive results for the sensitivity, energy and spatial resolutions of XEMIS2. (C) 2014 Elsevier B.V. All rights reserved.
The ratio R(f0/phi) of the branching fractions of the B0,s meson to the CP-odd eigenstate J/psi f0(980) and to J/psi phi(1020) is measured, where J/psi to mu+ mu-, f0 to pi+ pi-, and phi to K+ K-. ...The analysis is based on a data sample of pp collisions at a centre-of-mass energy of 7 TeV, collected by the CMS experiment, corresponding to an integrated luminosity of 5.3 inverse femtobarns. The result is R(f0/phi) = 0.140 +/- 0.013 +/- 0.018, where the first uncertainty is statistical and the second is systematic. This result is consistent with theoretical predictions and previous measurements of R(f0/phi). It is the most precise measurement of the ratio to date.
A joint measurement is presented of the branching fractions B0s→μ+μ− and B0→μ+μ− in proton-proton collisions at the LHC by the CMS and LHCb experiments. The data samples were collected in 2011 at a ...centre-of-mass energy of 7 TeV, and in 2012 at 8 TeV. The combined analysis produces the first observation of the B0s→μ+μ− decay, with a statistical significance exceeding six standard deviations, and the best measurement of its branching fraction so far, and three standard deviation evidence for the B0→μ+μ− decay. The measurements are statistically compatible with SM predictions and impose stringent constraints on several theories beyond the SM.
PDF
