We show that critical opalescence, a clear signature of second-order phase transition in conventional matter, manifests itself as critical intermittency in QCD matter produced in experiments with ...nuclei. This behavior is revealed in transverse momentum spectra as a pattern of power laws in factorial moments, to all orders, associated with baryon production. This phenomenon together with a similar effect in the isoscalar sector of pions (sigma mode) provide us with a set of observables associated with the search for the QCD critical point in experiments with nuclei at high energies.
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.
Performance of the micromegas detector in the CAST experiment Aune, S.; Dafni, T.; Fanourakis, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2007, Volume:
573, Issue:
1
Journal Article
Peer reviewed
Open access
The gaseous micromegas detector designed for the CERN Axion search experiment CAST, operated smoothly during Phase-I, which included the 2003 and 2004 running periods. It exhibited linear response in ...the energy range of interest (1–10
keV), good spatial sensitivity and energy resolution (15–19% FWHM at 5.9
keV) as well as remarkable stability. The detector's upgrade for the 2004 run, supported by the development of advanced offline analysis tools, improved the background rejection capability, leading to an average rate 5×10
−5
counts/s/cm
2/keV with 94% cut efficiency. Also, the origin of the detected background was studied with a Monte-Carlo simulation, using the GEANT4 package.
The use of the Micromegas technology for a new imaging system Fanourakis, G.K; Geralis, T; Kousouris, K ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2004, Volume:
527, Issue:
1-2
Journal Article
Peer reviewed
The Micromegas (Micromesh Gaseous) detector technology was developed by I. Giomataris and G. Charpak, in the mid 90s, for applications in the field of experimental Particle Physics. The most recent ...development is a novel Micromegas detector designed to detect photons of energies 1–10keV (X-ray range), for a discovery experiment of the hypothetical particles called axions, installed and currently taking data at CERN (the European Laboratory for Particle Research in Geneva). This detector has an X–Y readout capability of resolution less than 100μm, an energy resolution down to 14%, for this energy range, and an overall efficiency of 70%. With planned modifications, similar performances can be achieved for operation in the energy regime of the technetium gammas. This could lead to a novel γ-ray imaging device with spatial resolution in the submillimeter range. Initial results are presented obtained using the current detector with a parallel hole collimator to image thin capillary phantoms filled with a 99mTc water solution.
The new concept of the spherical TPC aims at relatively large target masses with low threshold and background, keeping an extremely simple and robust operation. Such a device would open the way to ...detect the neutrino-nucleus interaction, which, although a standard process, remains undetected due to the low energy of the neutrino-induced nuclear recoils. The progress in the development of the first 1 m3 prototype at Saclay is presented. Other physics goals of such a device could include supernova detection, low energy neutrino oscillations and study of non-standard properties of the neutrino, among others.
Micromegas for Axion Search and Prospects Abbon, P; Andriamonje, S; Aune, S ...
Journal of physics. Conference series,
04/2007, Volume:
65, Issue:
1
Journal Article
Peer reviewed
Open access
The Micromegas technology can be used to construct very powerful detectors for low background, low energy measurements. A Micromegas X-ray detector has been used to search for solar axions in the ...CAST experiment at CERN. The detector has an active area of 7 cm × 7 cm, a very good x-y position, and a good energy resolution. It is built using low radioactivity materials and it is capable of low energy X-ray measurements of a few hundred eV. Despite the lack of external shielding the obtained background level is below 5 × 105 counts/keV/cm2/s. The detector is being upgraded with a reduced active area Micromegas module, a focusing X-Ray telescope and shielding, which are expected to further reduce the background by about two orders of magnitude.
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