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86
result(s) for
"Fanourakis, G."
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Measuring the polarization of a rapidly precessing deuteron beam
2014
This paper describes a time-marking system that enables a measurement of the in-plane (horizontal) polarization of a 0.97−GeV/c deuteron beam circulating in the Cooler Synchrotron (COSY) at the Forschungszentrum Jülich. The clock time of each polarimeter event is used to unfold the 120-kHz spin precession and assign events to bins according to the direction of the horizontal polarization. After accumulation for one or more seconds, the down-up scattering asymmetry can be calculated for each direction and matched to a sinusoidal function whose magnitude is proportional to the horizontal polarization. This requires prior knowledge of the spin tune or polarization precession rate. An initial estimate is refined by resorting the events as the spin tune is adjusted across a narrow range and searching for the maximum polarization magnitude. The result is biased toward polarization values that are too large, in part because of statistical fluctuations but also because sinusoidal fits to even random data will produce sizable magnitudes when the phase is left free to vary. An analysis procedure is described that matches the time dependence of the horizontal polarization to templates based on emittance-driven polarization loss while correcting for the positive bias. This information will be used to study ways to extend the horizontal polarization lifetime by correcting spin tune spread using ring sextupole fields and thereby to support the feasibility of searching for an intrinsic electric dipole moment using polarized beams in a storage ring. This paper is a combined effort of the Storage Ring EDM collaboration and the JEDI collaboration.
Journal Article
The Hellenic Open University Cosmic Ray Telescope: Research and Educational Activities
2018
The Hellenic Open University Cosmic Ray Telescope consists of three autonomous stations installed at the University Campus in the city of Patras. Each station comprises three large (≈ 1 m 2 ) plastic scintillators and one or more Codalema type RF antennas detecting Extensive Air Showers (EAS), originating from primary particles with energy greater than 10 TeV. The operation and the performance of the Telescope is presented briefly, emphasising the educational activities foreseen in the framework of the HEllenic LYceum Cosmic Observatories Network (HELYCON).
Journal Article
PICOSEC-Micromegas: Robustness measurements and study of different photocathode materials
2019
Detectors with a time resolution of 20-30 ps and a reliable performance in high particles flux environments are necessary for an accurate vertex separation in future HEP experiments. The PICOSEC-Micromegas detector concept is a Micro-Pattern Gaseous Detector (MPGD) based solution addressing this particular challenge. The PICOSEC-Micromegas concept is based on a Micromegas detector coupled to a Cherenkov radiator and a photocathode. In this detector concept, all primary electrons are initiated in the photocathode and the time jitter fluctuations are reduced. Different resistive anode layers have been tested with the goal of preserving a stable detector operation in a high intensity pion beam. One important characteristic of a gaseous detector in a high flux environment is the ion backflow (IBF). That can cause damage to more fragile photocathode materials like CsI. Various types of photocathode materials have been tested in order to find a robust solution against IBF bombardment.
Journal Article
Development of Resistive Micromegas for Sampling Calorimetry
2018
Resistive micromegas is proposed as an active element for sampling calorimetry. Future linear collider experiments or the HL-LHC experiments can profit from those developments for Particle Flow Calorimetry. Micromegas possesses remarkable properties concerning gain stability, reduced ion feedback, response linearity, adaptable sensitive element granularity, fast response and high rate capability. Recent developments on Micromegas with a protective resistive layer present excellent results, resolving the problem of discharges caused by local high charge deposition, thanks to its RC-slowed charge evacuation. Higher resistivity though, may cause loss of the response linearity at high rates. We have scanned a wide range of resistivities and performed laboratory tests with X-rays that demonstrate excellent response linearity up to rates of (a few) times 10 MHz / cm 2 , with simultaneous mitigation of discharges. Beam test studies at SPS/CERN with hadrons have also shown a remarkable stability of the resistive Micromegas and low currents for rates up to 15 MHz / cm 2 . We present results from the aforementioned studies confronted with MC simulation
Journal Article
Molecular Sequelae of Proteasome Inhibition in Human Multiple Myeloma Cells
by
Mitsiades, Constantine S.
,
Anderson, Kenneth C.
,
Joseph, Marie
in
Antineoplastic Agents - pharmacology
,
Apoptosis
,
Biological Sciences
2002
The proteasome inhibitor PS-341 inhibits IκB degradation, prevents NF-κB activation, and induces apoptosis in several types of cancer cells, including chemoresistant multiple myeloma (MM) cells. PS-341 has marked clinical activity even in the setting of relapsed refractory MM. However, PS-341-induced apoptotic cascade(s) are not yet fully defined. By using gene expression profiling, we characterized the molecular sequelae of PS-341 treatment in MM cells and further focused on molecular pathways responsible for the anticancer actions of this promising agent. The transcriptional profile of PS-341-treated cells involved down-regulation of growth/survival signaling pathways, and up-regulation of molecules implicated in proapoptotic cascades (which are both consistent with the proapoptotic effect of proteasome inhibition), as well as up-regulation of heat-shock proteins and ubiquitin/proteasome pathway members (which can correspond to stress responses against proteasome inhibition). Further studies on these pathways showed that PS-341 decreases the levels of several antiapoptotic proteins and triggers a dual apoptotic pathway of mitochondrial cytochrome c release and caspase-9 activation, as well as activation of Jun kinase and a Fas/caspase-8-dependent apoptotic pathway [which is inhibited by a dominant negative (decoy) Fas construct]. Stimulation with IGF-1, as well as overexpression of Bcl-2 or constitutively active Akt in MM cells also modestly attenuates PS-341-induced cell death, whereas inhibitors of the BH3 domain of Bcl-2 family members or the heat-shock protein 90 enhance tumor cell sensitivity to proteasome inhibition. These data provide both insight into the molecular mechanisms of antitumor activity of PS-341 and the rationale for future clinical trials of PS-341, in combination with conventional and novel therapies, to improve patient outcome in MM.
Journal Article
Updated physics performance of the ESSnuSB experiment
by
Cristaldo Morales E
,
Danared, H
,
Efthymiopoulos, I
in
CP violation
,
Error analysis
,
Matter & antimatter
2021
In this paper, we present the physics performance of the ESSnuSB experiment in the standard three flavor scenario using the updated neutrino flux calculated specifically for the ESSnuSB configuration and updated migration matrices for the far detector. Taking conservative systematic uncertainties corresponding to a normalization error of 5% for signal and 10% for background, we find that there is 10σ(13σ) CP violation discovery sensitivity for the baseline option of 540 km (360 km) at δCP=±90∘. The corresponding fraction of δCP for which CP violation can be discovered at more than 5σ is 70%. Regarding CP precision measurements, the 1σ error associated with δCP=0∘ is around 5∘ and with δCP=-90∘ is around 14∘(7∘) for the baseline option of 540 km (360 km). For hierarchy sensitivity, one can have 3σ sensitivity for 540 km baseline except δCP=±90∘ and 5σ sensitivity for 360 km baseline for all values of δCP. The octant of θ23 can be determined at 3σ for the values of: θ23>51∘ (θ23<42∘ and θ23>49∘) for baseline of 540 km (360 km). Regarding measurement precision of the atmospheric mixing parameters, the allowed values at 3σ are: 40∘<θ23<52∘ (42∘<θ23<51.5∘) and 2.485×10-3 eV2<Δm312<2.545×10-3 eV2 (2.49×10-3 eV2<Δm312<2.54×10-3 eV2) for the baseline of 540 km (360 km).
Journal Article
Rare event searches based on Micromegas detectors: the T-REX project
2012
Micromegas readouts are an attractive option for many of the rare event searches, due to their performance regarding energy resolution, gain stability, homogeneity and material budget. The T-REX project aims at developing further these novel readout techniques for Time Projection Chambers and their potential use in experiments searching for rare events. Here we will refer to the latest results regarding the use and prospects of Micromegas read-outs in axion physics (CAST and the future helioscope), as well as the R&D carried out within NEXT, to search for the neutrinoless double-beta decay.
Journal Article
The T-REX project: Micromegas for Rare Event Searches
2012
The T-REX project aims at developing novel readout techniques for Time Projection Chambers for experiments searching for Rare Events. The Micromegas detectors are a good option, because of their good performance regarding low background levels, energy and time resolution, gain and stability of operation. In the present we will shortly refer to two particular cases, on one hand their performance in the CAST experiment and on the other the studies carried out within NEXT, a neutrinoless double-beta decay experiment.
Journal Article
An ultra-low-background detector for axion searches
2009
A low background Micromegas detector has been operating in the CAST experiment at CERN for the search of solar axions since the start of data taking in 2002. The detector, made out of low radioactivity materials, operated efficiently and achieved a very low level of background (5×10-5 keV-1-cm-2-s-1) without any shielding. New manufacturing techniques (Bulk/Microbulk) have led to further improvement of the characteristics of the detector such as uniformity, stability and energy resolution. These characteristics, the implementation of passive shielding and the improvement of the analysis algorithms have dramatically reduced the background level (2×10-7 keV-1-cm-2∣s-1), improving thus the overall sensitivity of the experiment and opening new possibilities for future searches.
Journal Article
Performance of micromegas detectors in the CAST Experiment
by
Papaevangelou, T
,
Davenport, M
,
Dafni, T
in
Background noise
,
Charge coupled devices
,
Detectors
2012
CERN Axion Solar Telescope (CAST) experiment is searching for axions coming from the Sun. Inside transverse magnetic fields, axions can be converted into X-rays, which can be detected by X-ray detectors. The expected energy of the signal in CAST is in the 1-10 keV range. Low noise and low background detectors are necessary to increase the sensitivity of the experiment. Micro Mesh Gaseous Structure (micromegas) detectors have been used in CAST since the beginning, providing good energy and spatial resolution for CAST's needs. CAST has been intensely studying micromegas detectors to develop new technologies. Initially, CAST detectors consisted of a micromegas, a Time Projection Chamber (TPC) and a Charged Couple Device (CCD), however the improvements in micromegas technologies encouraged CAST to replace the TPC with 2 new micromegas detectors. In some periods during CAST run, ultra low background has been observed in one of the micromegas detectors and it is being investigated through simulations and laboratory tests carried out at Canfranc Underground Laboratory. If this low background is indeed not a systematic effect, it can open new possibilities on rare event searches.
Journal Article