49 research outputs found
Tracking algorithms for the active target MAYA
The MAYA detector is a Time-Charge Projection Chamber based on the concept of
active target. These type of devices use a part of the detection system, the
filling gas in this case, in the role of reaction target. The MAYA detector
performs three-dimensional tracking, in order to determine physical observables
of the reactions occurring inside the detector. The reconstruction algorithms
of the tracking use the information from a two-dimensional projection on the
segmented cathode, and, in general, they need to be adapted for the different
experimental settings of the detector. This work presents some of the most
relevant solutions developed for the MAYA detector
MAYA: An active-target detector for binary reactions with exotic beams
International audienceWith recent improvements in the production of radioactive beams in facilities such as SPIRAL at GANIL, a larger area of the nuclear chart is now accessible for experimentation. For these usually low-intensity and low-energy secondary beams, we have developed the new MAYA detector based on the active-target concept. This device allows to use a relatively thick target without loss of resolution by using the detection gas as target material. Dedicated 3D tracking, particle identification, energy loss and range measurements allow complete kinematic reconstruction of reactions taking place inside MAYA
Inverse kinematics proton scattering from the exotic nucleus O
NESTER PTHInternational audienceWe have measured for the first time elastic and inelastic proton scattering from the neutron rich nucleus 22O at 46.6 AMeV using the MUST array
The N=14 shell closure in O viewed through a neutron sensitive probe
NESTER PTHInternational audienceTo investigate the behavior of the N=14 neutron gap far from stability with a neutron-sensitive probe, proton elastic and 2+1 inelastic scattering angular distributions for the neutron-rich nucleus 22O were measured with a secondary beam intensity of only 1200 particles per second using the MUST silicon strip detector array at the GANIL facility. A phenomenological analysis yields a deformation parameter bp;p' = 0.26 +- 0.04 for the 2+1 state, much lower than in 20O, showing a surprisingly weak neutron contribution to this state. A fully microscopic analysis was performed using optical potentials obtained from matter and transition densities generated by continuum Skyrme-HFB and QRPA calculations, respectively. When the present results and those from a 22O + 197Au scattering experiment are combined, the ratio of neutron to proton contributions to the 2+1 state is found close to the N/Z ratio, demonstrating a strong N=14 shell closure in the vicinity of the neutron drip-line
Ion slowing down and charge exchange at small impact parameters selected by channeling: superdensity effects
CASInternational audienceIn two experiments performed with 20-30 MeV/u highly charged heavy ions (Pb56+, U91+) channeled through thin silicon crystals, we observed the original features of superdensity, associated to the glancing collisions with atomic rows undergone by part of the incident projectiles. In particular the very high collision rate yields a quite specific charge exchange regime, that leads to a higher ionization probability than in random conditions. X-ray measurements show that electrons captured in outershells are prevented from being stabilized, which enhances the lifetime of the projectile innershell vacancies. The charge state distributions and the energy loss spectra are compared to Monte-Carlo simulations. These simulations confirm, extend and illustrate the qualitative analysis of the experimental results
Study of Na at SPIRAL
NESTERInternational audienceThe excitation function for the elastic-scattering reaction p18Ne, p18Ne was measured with the first radioactive beam from the SPIRAL facility at the GANIL laboratory and with a solid cryogenic hydrogen target. Several broad resonances have been observed, corresponding to new excited states in the unbound nucleus 19Na. In addition, two-proton emission events have been identified and are discussed
MAYA: an active target detector for the study of extremely exotic nuclei
With the recent improvements on production of radioactive beams in facilities such as SPIRAL at GANIL or ISAC at TRIUMF, a larger area of the nuclear chart is now accessible for experimentation. For these usually low-intensity and low-energy secondary beams, we have developed the new MAYA detector based on the active-target concept. This device allows to use a relatively thick target without loss of resolution by using the detection gas as target material. A dedicated 3-D tracking, particle identification, energy loss and range measurements allow complete kinematic reconstruction of reactions taking place inside MAYA. Recent results from studies of 7H, 7-9He performed at GANIL and of the outer skin structure of the exotic nucleus 11Li performed at TRIUMF will be rewieved. The capabilities of this new techniques in future experimental studies with secondary exotic beams near and beyond the drip lines, where large kinematic ranges are needed, including regions not accessible with the standard techniques, will be discussed
Direct mass measurements of Se and Y
Expérience GANILInternational audienceThe masses of neutron-deficient nuclides near the N=Z line with A=64-80 have been determined using a direct time-of-flight technique which employed a cyclotron as a high-resolution spectrometer. The measured atomic masses for Se and Y were 67.9421(3) u and 79.9344(2) u, respectively. The new values agree with the 2003 Atomic Mass Evaluation. The result for Se confirms that this nucleus is a waiting point of the rp-process, and that for Y resolves the conflict between earlier measurements. Using the present results and the 2003 Atomic Mass Evaluation compilation, the empirical interaction between the last proton and the last neutron in N=Z nuclei has been revisited and extended
Reactions induced beyond the dripline at low energy by secondary beams
International audienceReactions induced on protons at low incident energy (3.5 MeV/n) were measured with a He beam accelerated by Spiral at Ganil. The particles were detected in the active target Maya, filled with gas. The beam was stopped in the detector, so energies from incident beam energy down to detector threshold were covered. Proton elastic scattering, one neutron pick-up (p, d) and (p, t) reactions were observed. In the (p, d) reaction very high cross-sections of the order of 1barn were observed, that could be reproduced using a direct reaction formalism. This is the first time that this strong increase of transfer reaction cross-sections at very low energy predicted for loosely bound systems was observed. Spectroscopic factors are in agreement with a simple shell model configuration. No evidence for a low lying excited state in He was found