567 research outputs found
Neutron capture cross section measurements of 238U, 241Am and 243Am at n_TOF
Proposal: Neutron capture cross section measurements of 238U, 241Am and 243Am at n_TOFThe increase of the world energy demand and the need of low carbon energy sources have triggered the renaissance and/or enhancement of nuclear energy in many countries. Fundamental nuclear physics can contribute in a practical way to the sustainability and safety of the nuclear energy production and the management of the nuclear waste. There exists a series of recent studies which address the most relevant isotopes, decay data, nuclear reaction channels and energy ranges which have to be investigated in more detail for improving the design of different advanced nuclear systems [1] and nuclear fuel cycles [2]. In this proposal, we aim at the measurement of the neutron capture cross sections of 238U, 241Am and 243Am. All three isotopes are listed in the NEA High Priority Request List [37], are recommended for measurements [1] and play an important role in the nuclear energy production and fuel cycle scenarios. The measurements will provide as well valuable nuclear structure data necessary for the improvement of nuclear models and the statistical interpretation of the nuclear propertiesPostprint (author's final draft
Micromegas in a Bulk
In this paper we present a novel way to manufacture the bulk Micromegas
detector. A simple process based on the PCB (Printed Circuit Board) technology
is employed to produce the entire sensitive detector. Such fabrication process
could be extended to very large area detectors made by the industry. The low
cost fabrication together with the robustness of the electrode materials will
make it extremely attractive for several applications ranging from particle
physics and astrophysics to medicineComment: 6 pages, 4 figure
An improved cosmological bound on the thermal axion mass
Relic thermal axions could play the role of an extra hot dark matter
component in cosmological structure formation theories. By combining the most
recent observational data we improve previous cosmological bounds on the axion
mass m_a in the so-called hadronic axion window. We obtain a limit on the axion
mass m_a < 0.42eV at the 95% c.l. (m_a < 0.72eV at the 99% c.l.). A novel
aspect of the analysis presented here is the inclusion of massive neutrinos and
how they may affect the bound on the axion mass. If neutrino masses belong to
an inverted hierarchy scheme, for example, the above constraint is improved to
m_a < 0.38eV at the 95% c.l. (m_a < 0.67eV at the 99% c.l.). Future data from
experiments as CAST will provide a direct test of the cosmological bound.Comment: 5 Pages, 3 Figure
The Micromegas detector of the CAST experiment
A low background Micromegas detector has been operating in the CAST
experiment at CERN for the search of solar axions during the first phase of the
experiment (2002-2004). The detector, made out of low radioactivity materials,
operated efficiently and achieved a very low level of background rejection (5 x
10^-5 counts/keV/cm^2/s) without shielding.Comment: 13 pages, 12 figures and images, submitted to New Journal o
No light shining through a wall : new results from a photoregeneration experiment
Recently, axion-like particle search has received renewed interest. In
particular, several groups have started ``light shining through a wall''
experiments based on magnetic field and laser both continuous, which is very
demanding in terms of detector background. We present here the 2 limits
obtained so far with our novel set-up consisting of a pulsed magnetic field and
a pulsed laser. In particular, we have found that the axion-like particle two
photons inverse coupling constant is GeV provided that the
particle mass 1 meV. Our results definitively invalidate
the axion interpretation of the original PVLAS optical measurements with a
confidence level greater than 99.9%.Comment: Version that will appear in Physical Review Letters, Vol. 99, n. 18,
(2 Nov 2007
Constraints on the axion-electron coupling for solar axions produced by Compton process and bremsstrahlung
The search for solar axions produced by Compton () and bremsstrahlung-like () processes has
been performed. The axion flux in the both cases depends on the axion-electron
coupling constant. The resonant excitation of low-lying nuclear level of
was looked for: Tm Tm
Tm (8.41 keV). The Si(Li) detector and
Tm target installed inside the low-background setup were used to detect
8.41 keV -rays. As a result, a new model independent restriction on the
axion-electron and the axion-nucleon couplings was obtained:
. In model of hadronic
axion this restriction corresponds to the upper limit on the axion-electron
coupling and on the axion mass eV (90%
c.l.). The limits on axion mass are 105 eV and 1.3 keV for
DFSZ- and KSVZ-axion models, correspondingly (90% c.l.).Comment: 7 pages, 4 figure
The neutron time-of-flight facility n-TOF at CERN: Phase II
Neutron-induced reactions are studied at the neutron time-of-flight facility n-TOF at CERN. The facility uses 6∼ns wide pulses of 20 GeV/c protons impinging on a lead spallation target. The large neutron energy range and the high instantaneous neutron flux combined with high resolution are among the key characteristics of the facility. After a first phase of data taking during the period 2001-2004, the facility has been refurbished with an upgraded spallation target and cooling system for a second phase of data taking which started in 2009. Since 2010, the experimental area at 185 m where the neutron beam arrives, has been modified into a worksector of type A, allowing the extension of the physics program to include neutron-induced reactions on radioactive isotopes
New Experimental limit on Optical Photon Coupling to Neutral, Scalar Bosons
We report on the first results of a sensitive search for scalar coupling of
photons to a light neutral boson in the mass range of approximately 1.0
milli-electron volts and coupling strength greater than 10 GeV using
optical photons. This was a photon regeneration experiment using the "light
shining through a wall" technique in which laser light was passed through a
strong magnetic field upstream of an optical beam dump; regenerated laser light
was then searched for downstream of a second magnetic field region optically
shielded from the former. Our results show no evidence for scalar coupling in
this region of parameter space.Comment: pdf-file, 10 pages, 4 figures, submitted to Physical Review Letter
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
First results of the new n_TOF spallation target commissioning
The Neutron Time of Flight facility n_TOF located at CERN started to take data in 2001 . Due to an increase of radioactivity released in the cooling water the experiment was stopped by end of 2004 . In 2008 a new spallation target has been installed . In 2009 the collaboration has performed the full commissioning of the facility, consisting in the determination of the fluence, the beam profile, and the energy resolution of the neutron beam. After a brief description of the new target assembly, very preliminary results concerning the shape of the neutron fluence and its absolute value will be given. Measurements of the neutron beam profile will also be shown.Postprint (published version
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