112 research outputs found
Characterization of microbulk detectors in argon- and neon-based mixtures
A recent Micromegas manufacturing technique, so called Microbulk, has been
developed, improving the uniformity and stability of this kind of detectors.
Excellent energy resolutions have been obtained, reaching values as low as 11%
FWHM at 5.9 keV in Ar+5%iC4H10. This detector has other advantages like its
flexible structure, low material budget and high radio-purity. Two microbulk
detectors with gaps of 50 and 25 um have been characterized in argon- and
neon-based mixtures with ethane, isobutane and cyclohexane. The results will be
presented and discussed. The gain curves have been fitted to the Rose-Korff
gain model and dependences of the electron mean free path and the threshold
energy for ionization have been obtained. The possible relation between these
two parameters and the energy resolution will be also discussed.Comment: Submitted to the Journal of Instrumentatio
Neutron imaging with a Micromegas detector
The micropattern gaseous detector Micromegas has been developed for several
years in Saclay and presents good performance for neutron detection. A
prototype for neutron imaging has been designed and new results obtained in
thermal neutron beams are presented. Based on previous results demonstrating a
good 1D spatial resolution, a tomographic image of a multiwire cable has been
performed using a 1D Micromegas prototype. The number of pillars supporting the
micromesh is too large and leads to local losses of efficiency that distort the
tomographic reconstruction. Nevertheless, this first tomographic image achieved
with this kind of detector is very encouraging. The next worthwhile development
for neutron imaging is to achieve a bi-dimensional detector, which is presented
in the second part of this study. The purpose of measurements was to
investigate various operational parameters to optimize the spatial resolution.
Through these measurements the optimum spatial resolution has been found to be
around 160 microns (standard deviation) using Micromegas operating in double
amplification mode. Several 2D imaging tests have been carried out. Some of
these results have revealed fabrication defects that occurred during the
manufacture of Micromegas and that are limiting the full potential of the
present neutron imaging system.Comment: 6 pages, 10 figures, presented at IEEE 2004 conference in Roma, Ital
Aging studies of Micromegas prototypes for the HL-LHC
The micromegas technology is a promising candidate to replace the forward
muon chambers for the luminosity upgrade of ATLAS. The LHC accelerator
luminosity will be five times the nominal one, increasing background and
pile-up event probability. This requires detector performances which are
currently under study in intensive R&D activities. Aging is one of the key
issues for a high-luminosity LHC application. For this reason, we study the
properties of resistive micromegas detectors under intense X-ray radiation and
under thermal neutrons in different CEA-Saclay facilities. This study is
complementary to those already performed using fast neutrons.Comment: Proceedings of the MPGD2011 Conferenc
The COMPASS Experiment at CERN
The COMPASS experiment makes use of the CERN SPS high-intensitymuon and
hadron beams for the investigation of the nucleon spin structure and the
spectroscopy of hadrons. One or more outgoing particles are detected in
coincidence with the incoming muon or hadron. A large polarized target inside a
superconducting solenoid is used for the measurements with the muon beam.
Outgoing particles are detected by a two-stage, large angle and large momentum
range spectrometer. The setup is built using several types of tracking
detectors, according to the expected incident rate, required space resolution
and the solid angle to be covered. Particle identification is achieved using a
RICH counter and both hadron and electromagnetic calorimeters. The setup has
been successfully operated from 2002 onwards using a muon beam. Data with a
hadron beam were also collected in 2004. This article describes the main
features and performances of the spectrometer in 2004; a short summary of the
2006 upgrade is also given.Comment: 84 papes, 74 figure
Ultra low background Micromegas detectors for BabyIAXO solar axion search
The International AXion Observatory (IAXO) is a large scale axion helioscope
that will look for axions and axion-like particles produced in the Sun with
unprecedented sensitivity. BabyIAXO is an intermediate experimental stage that
will be hosted at DESY (Germany) and that will test all IAXO subsystems serving
as a prototype for IAXO but at the same time as a fully-fledged helioscope with
potential for discovery.
One of the crucial components of the project is the ultra-low background
X-ray detectors that will image the X-ray photons produced by axion conversion
in the experiment. The baseline detection technology for this purpose are
Micromegas (Microbulk) detectors. We will show the quest and the strategy to
attain the very challenging levels of background targeted for BabyIAXO that
need a multi-approach strategy coming from ground measurements, screening
campaigns of components of the detector, underground measurements, background
models, in-situ background measurements as well as powerful rejection
algorithms. First results from the commissioning of the BabyIAXO prototype will
be shown.Comment: 4 pages, 2 figures, submitted for the proceedings of the
International Conference on Micro Pattern Gaseous Detectors, December 2022,
Israe
Shell evolution of N = 40 isotones towards 60Ca: First spectroscopy of 62Ti
Excited states in the N=40 isotone 62Ti were populated via the 63V(p,2p)62Ti reaction at ∼200 MeV/nucleon at the Radioactive Isotope Beam Factory and studied using γ-ray spectroscopy. The energies of the 21+→0gs+ and 41+→21+ transitions, observed here for the first time, indicate a deformed 62Ti ground state. These energies are increased compared to the neighboring 64Cr and 66Fe isotones, suggesting a small decrease of quadrupole collectivity. The present measurement is well reproduced by large-scale shell-model calculations based on effective interactions, while ab initio and beyond mean-field calculations do not yet reproduce our findings. The shell-model calculations for 62Ti show a dominant configuration with four neutrons excited across the N=40 gap. Likewise, they indicate that the N=40 island of inversion extends down to Z=20, disfavoring a possible doubly magic character of the elusive 60Ca
The COMPASS Setup for Physics with Hadron Beams
The main characteristics of the COMPASS experimental setup for physics with
hadron beams are described. This setup was designed to perform exclusive
measurements of processes with several charged and/or neutral particles in the
final state. Making use of a large part of the apparatus that was previously
built for spin structure studies with a muon beam, it also features a new
target system as well as new or upgraded detectors. The hadron setup is able to
operate at the high incident hadron flux available at CERN. It is characterised
by large angular and momentum coverages, large and nearly flat acceptances, and
good two and three-particle mass resolutions. In 2008 and 2009 it was
successfully used with positive and negative hadron beams and with liquid
hydrogen and solid nuclear targets. This article describes the new and upgraded
detectors and auxiliary equipment, outlines the reconstruction procedures used,
and summarises the general performance of the setup.Comment: 91 pages, 101 figures and 7 table
Spectroscopy of 16B from quasi-free (p,pn) reaction with 17B
Spectroscopy of 16B plays an essential role in understanding the halo structure in 17B, but very limited knowledge has so far been obtained. We have carried out a kinematically complete measurement on the spectroscopy of 16B by using quasi-free (p,pn) reaction on 17B. The level scheme of 16B up to 5 MeV was made clear for the first time
Mass, Spectroscopy, and Two-Neutron Decay of Be 16
The structure and decay of the most neutron-rich beryllium isotope, Be16, has been investigated following proton knockout from a high-energy B17 beam. Two relatively narrow resonances were observed for the first time, with energies of 0.84(3) and 2.15(5) MeV above the two-neutron decay threshold and widths of 0.32(8) and 0.95(15) MeV, respectively. These were assigned to be the ground (Jπ=0+) and first excited (2+) state, with Ex=1.31(6) MeV. The mass excess of Be16 was thus deduced to be 56.93(13) MeV, some 0.5 MeV more bound than the only previous measurement. Both states were observed to decay by direct two-neutron emission. Calculations incorporating the evolution of the wave function during the decay as a genuine three-body process reproduced the principal characteristics of the neutron-neutron energy spectra for both levels, indicating that the ground state exhibits a strong spatially compact dineutron component, while the 2+ level presents a far more diffuse neutron-neutron distribution
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