68 research outputs found
MPGD's spatial and energy resolution studies with an adjustable point-like electron source
11th Vienna Conference on Instrumentation (February 2007) , to appear in the Proceedings (NIM A)International audienceMicropattern Gaseous Detectors (MPGD), like Micromegas or GEM, are used or foreseen in particle physics experiments for which a very good spatial resolution is required. We have developed an experimental method to separate the contribution of the transverse diffusion and the multiplication process by varying the number of primary electrons generated by a point-like source. A pulsed nitrogen laser is focused by an optical set-up on the drift electrode which is made of a thin metal layer deposited on a quartz lamina. The number of primary electrons can be adjusted from a few to several thousands on a spot which transverse size is less than RMS. The detector can be positioned with an accuracy of by a motorized three dimensional system. This method was applied to a small Micromegas detector with a gain set between and and an injection of 60 to 2000 photoelectrons. Spatial resolutions as small as were measured with 2000 primary electrons. An estimation of the upper limit of the relative gain variance can be obtained from the measurements
Probing pre-formed alpha particles in the ground state of nuclei
In this Letter, we report on alpha particle emission through the nuclear
break-up in the reaction 40Ca on a 40Ca target at 50A MeV. It is observed that,
similarly to nucleons, alpha particles can be emitted to the continuum with
very specific angular distribution during the reaction. The alpha particle
properties can be understood as resulting from an alpha cluster in the daughter
nucleus that is perturbed by the short range nuclear attraction of the
collision partner and emitted. A time-dependent theory that describe the alpha
particle wave-function evolution is able to reproduce qualitatively the
observed angular distribution. This mechanism offers new possibilities to study
alpha particle properties in the nuclear medium.Comment: 4 pages, 3 figure
Single electron response and energy resolution of a Micromegas detector
Micro-Pattern Gaseous Detectors (MPGDs) such as Micromegas or GEM are used in
particle physics experiments for their capabilities in particle tracking at
high rates. Their excellent position resolutions are well known but their
energy characteristics have been less studied. The energy resolution is mainly
affected by the ionisation processes and detector gain fluctuations. This paper
presents a method to separetely measure those two contributions to the energy
resolution of a Micromegas detector. The method relies on the injection of a
controlled number of electrons. The Micromegas has a 1.6-mm drift zone and a
160-m amplification gap. It is operated in Ne
95%-iCH 5% at atmospheric pressure. The electrons
are generated by non-linear photoelectric emission issued from the photons of a
pulsed 337-nm wavelength laser coupled to a focusing system. The single
electron response has been measured at different gains (3.7 10,
5.0 10 and 7.0 10) and is fitted with a good
agreement by a Polya distribution. From those fits, a relative gain variance of
0.310.02 is deduced. The setup has also been characterised at several
voltages by fitting the energy resolution measured as a function of the number
of primary electrons, ranging from 5 up to 210. A maximum value of the Fano
factor (0.37) has been estimated for a 5.9 keV X-rays interacting in the Ne
95%-iCH 5% gas mixture.Comment: Preprint submitted to Nuclear Instrumentation and Methods in Physics
Research Section A: Accelerators, Spectrometers, Detectors and Associated
Equipment; Nuclear Instruments and Methods in Physics Research Section A:
Accelerators, Spectrometers, Detectors and Associated Equipment in press
(2009
Structure of low-lying states of C from proton elastic and inelastic scattering
NESTER PTH, expérience GANIL, équipement SISSITo probe the ground state and transition densities, elastic and inelastic scattering on a proton target were measured in inverse kinematics for the unstable C and C nuclei at 45.3 and 40.6 MeV/nucleon, respectively. The detection of the recoil proton was performed by the MUST telescope array, in coincidence with a wall of scintillators for the quasiprojectile. The differential cross sections for elastic and inelastic scattering to the first excited states are compared to the optical model calculations performed within the framework of the microscopic nucleon-nucleus Jeukenne-Lejeune-Mahaux potential. Elastic scattering is sensitive to the matter-root-mean square radius found to be 2.420.1 and 2.330.1 fm, for C, respectively. The transition densities from cluster and mean-field models are tested, and the cluster model predicts the correct order of magnitude of cross sections for the transitions of both isotopes. Using the Bohr-Mottelson prescription, a profile for the C transition density from the ground to the state is deduced from the data. The corresponding neutron transition matrix element is extracted: Mn=5.511.09 fm
Spectroscopy of Na: Bridging the two-proton radioactivity of Mg
The unbound nucleus Na, the intermediate nucleus in the two-proton
radioactivity of Mg, was studied by the measurement of the resonant
elastic scattering reaction Ne(p,Ne)p performed at 4 A.MeV.
Spectroscopic properties of the low-lying states were obtained in a R-matrix
analysis of the excitation function. Using these new results, we show that the
lifetime of the Mg radioactivity can be understood assuming a sequential
emission of two protons via low energy tails of Na resonances
Technical Design Report for the PANDA Solenoid and Dipole Spectrometer Magnets
This document is the Technical Design Report covering the two large
spectrometer magnets of the PANDA detector set-up. It shows the conceptual
design of the magnets and their anticipated performance. It precedes the tender
and procurement of the magnets and, hence, is subject to possible modifications
arising during this process.Comment: 10 pages, 14MB, accepted by FAIR STI in May 2009, editors: Inti
Lehmann (chair), Andrea Bersani, Yuri Lobanov, Jost Luehning, Jerzy Smyrski,
Technical Coordiantor: Lars Schmitt, Bernd Lewandowski (deputy),
Spokespersons: Ulrich Wiedner, Paola Gianotti (deputy
Nuclear astrophysics with radioactive ions at FAIR
The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process, β-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes
Structure of light exotic nuclei He and C from (p,p') reactions
NESTERThe structure of the light unstable nuclei 10,11C and 6,8He is investigated by means of (p,p′) reactions. The experiments were performed at GANIL using the MUST detector, an array of Si and SiLi telescopes. The (p,p′) are analyzed within the framework of the microscopic JLM potential, allowing to test the densities predicted by structure models. Preliminary data from the 8He(p,o′) reaction performed at the SPIRAL facility at 15.6 MeV/nucleon are discussed
Technical Design Report for the: PANDA Micro Vertex Detector
This document illustrates the technical layout and the expected performance
of the Micro Vertex Detector (MVD) of the PANDA experiment. The MVD will detect
charged particles as close as possible to the interaction zone. Design criteria
and the optimisation process as well as the technical solutions chosen are
discussed and the results of this process are subjected to extensive Monte
Carlo physics studies. The route towards realisation of the detector is
outlined.Comment: 189 pages, 225 figures, 41 table
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