7 research outputs found
Investigation of gamma-ray sensitivity of neutron detectors based on thin converter films
Currently, many detector technologies for thermal neutron detection are in
development in order to lower the demand for the rare 3He gas. Gas detectors
with solid thin film neutron converters readout by gas proportional counter
method have been proposed as an appropriate choice for applications where large
area coverage is necessary. In this paper, we investigate the probability for
gamma-rays to generate a false count in a neutron measurement. Simulated
results are compared to measurement with a 10B thin film prototype and a 3He
detector. It is demonstrated that equal gamma-ray rejection to that of 3He
tubes is achieved with the new technology. The arguments and results presented
here are also applicable to gas detectors with converters other than solid 10B
layers, such as 6Li layers and 10BF3 gas.Comment: Submitted to Journal of Instrumentatio
Rapid onset of collectivity in the vicinity of 78Ni
gamma-rays following the B and B-n decay of the very neutron rich 84Ga
produced by photo-fission of 238U have been studied at the newly built ISOL
facility of IPN Orsay: ALTO. Two activities were observed and assigned to two
B-decaying states: 84gGa, I = (0\^-) and 84mGa, I = (3\^-, 4\^-). Excitation
energies of the 2+1 and 4+1 excited states of 84Ge were measured at E(2+1) =
624.3 keV and E(4+1) = 1670.1 keV. Comparison with HFB+GCM calculations allows
to establish the collective character of this nucleus indicating a substantial
N=50 core polarization. The excitation energy of the 1/2+1 state in 83Ga known
to carry a large part of the neutron 3s1/2 strength was measured at 247.8keV.
Altogether these data allow to confirm the new single particle state ordering
which appears immediately after the double Z=28 and N=50 shell closure and to
designate 78Ni as a fragile and easily polarized doubly-magic core.Comment: 4 pages, ReVTe
Collisions profondĂ©ment inĂ©lastiques entre ions lourds auprĂšs du Tandem dâOrsay & Spectroscopie gamma des noyaux exotiques riches en neutrons de la couche fp avec le multi-dĂ©tecteur germanium ORGAM
This PhD thesis was prepared within the nuclear structure group of IPN Orsay. The work presented aimed to produce neutron rich fp shell nuclei through heavy ion collisions at the tandem accelerator of IPN, and to study them using gamma spectroscopy. For this purpose, a germanium gamma array called ORGAM, and dedicated to high resolution gamma spectroscopy, was set up at the tandem accelerator. During the year 2008/2009, the individual germanium detectors were tested and repaired, as well as their ancillary anti-Compton shielding. At the same time, the liquid nitrogen auto-fill system was improved for better reliability. The array was finally set up on a beam line of the accelerator.The first experiment using the ORGAM array was performed in July 2009. This experiment aimed to study fully damped deep-inelastic collisions between a 36S beam accelerated to 154 MeV, and a 70Zn target. An additional charged particle detection system was used to detect interesting fragments emitted at backward angles. It was not possible to separate these fragments from the background induced by backscattered ions from the beam. Nevertheless, the study of gamma-gamma coincidences detected with the ORGAM array allowed to identify gamma cascades de-exciting nuclei potentially produced through the mechanism of interest. Data accumulated during another experiment performed at the tandem accelerator in 2005 were analyzed. Fusion-evaporation reaction between a 25 MeV, 14C beam focused on a 48Ca target produced the 57Cr and 59Mn nuclei, whose energy spectra were established up to 3 MeV.We attempted to study theoretically odd Chromium isotopes with a simple model based on the intermediate coupling scheme. This model, which doesnât take into account correlation between valence nucleons, described in satisfactory way the semi-magic + 1 neutron, 53Cr, but failed to do so for mid-shell nuclei 55Cr and 57Cr.Les travaux effectuĂ©s au cours de cette thĂšse au sein du groupe de structure nuclĂ©aire de lâIPN dâOrsay sâarticulent autour de la production, en vue dâune Ă©tude par spectroscopie gamma, de noyaux exotiques riches en neutron de la couche fp. Dans ce cadre, nous avons mis en place, auprĂšs de lâaccĂ©lĂ©rateur Tandem dâOrsay, un multi-dĂ©tecteur au germanium baptisĂ© ORGAM, destinĂ© Ă la spectroscopie gamma Ă haute rĂ©solution. Au cours de lâannĂ©e 2008-2009, les dĂ©tecteurs amenĂ©s Ă composer ORGAM ont Ă©tĂ© testĂ©s individuellement, ainsi que le dispositif annexe de rĂ©jection Compton, en coopĂ©ration avec la division instrumentation du laboratoire. ParallĂšlement, le systĂšme dâalimentation automatique en azote liquide, destinĂ© au maintien des dĂ©tecteurs Ă basse tempĂ©rature, a Ă©tĂ© amĂ©liorĂ© et fiabilisĂ©. Lâensemble du dispositif a Ă©tĂ© mis en place sur une ligne de faisceau de lâaccĂ©lĂ©rateur tandem avec le concours du personnel technique de lâaccĂ©lĂ©rateur.La premiĂšre expĂ©rience utilisant le dispositif ORGAM a Ă©tĂ© rĂ©alisĂ©e en juillet 2009. Cette expĂ©rience, dont les donnĂ©es ont Ă©tĂ© analysĂ©es dans le cadre de ce travail, visait Ă Ă©tudier les collisions profondĂ©ment inĂ©lastiques entre un faisceau de 36S accĂ©lĂ©rĂ© Ă 154 MeV, et une cible de 70Zn. Un dispositif permettant la dĂ©tection des particules chargĂ©es Ă©mises Ă grand angle a Ă©tĂ© utilisĂ© afin dâidentifier les fragments de ces collisions. Il nâa pas Ă©tĂ© possible, du fait du fond important induit par la diffusion Ă©lastique du faisceau dans la cible, dâidentifier directement ces fragments. LâĂ©tude des coĂŻncidences gamma-gamma avec le dĂ©tecteur ORGAM a cependant permis de mettre en Ă©vidence de nombreuses cascades de photons dĂ©sexcitant des noyaux potentiellement produits par les rĂ©actions dâintĂ©rĂȘt.Les donnĂ©es recueillies au cours dâune autre expĂ©rience, rĂ©alisĂ©e auprĂšs du tandem dâOrsay en 2005, ont Ă©tĂ© analysĂ©es dans le cadre de ce travail. Cette expĂ©rience, visant Ă produire par fusion Ă©vaporation entre un faisceau de 14C Ă 25 MeV et une cible de 48Ca, les noyaux de 59Mn et de 57Cr, a permis dâĂ©tablir une partie du spectre en Ă©nergie dâexcitation de ces noyaux, jusqu'Ă une Ă©nergie dâexcitation supĂ©rieure Ă 3 MeV.Une Ă©tude thĂ©orique des noyaux de chrome impairs de la couche fp a Ă©tĂ© tentĂ©e Ă lâaide dâun modĂšle phĂ©nomĂ©nologique de couplage intermĂ©diaire. Ce modĂšle a permis une description satisfaisante du 53Cr. Les prĂ©dictions du modĂšle, qui ne prend pas en compte lâinteraction entre nuclĂ©ons de valence, se sont avĂ©rĂ©es beaucoup moins satisfaisante pour les noyaux de 55Cr et 57Cr
Deep-inelastic heavy-ion collisions at the tandem accelerator in Orsay & Gamma spectroscopy of fp-shell neutron-rich nuclei with the ORGAM germanium array
Les travaux effectuĂ©s au cours de cette thĂšse au sein du groupe de structure nuclĂ©aire de lâIPN dâOrsay sâarticulent autour de la production, en vue dâune Ă©tude par spectroscopie gamma, de noyaux exotiques riches en neutron de la couche fp. Dans ce cadre, nous avons mis en place, auprĂšs de lâaccĂ©lĂ©rateur Tandem dâOrsay, un multi-dĂ©tecteur au germanium baptisĂ© ORGAM, destinĂ© Ă la spectroscopie gamma Ă haute rĂ©solution. Au cours de lâannĂ©e 2008-2009, les dĂ©tecteurs amenĂ©s Ă composer ORGAM ont Ă©tĂ© testĂ©s individuellement, ainsi que le dispositif annexe de rĂ©jection Compton, en coopĂ©ration avec la division instrumentation du laboratoire. ParallĂšlement, le systĂšme dâalimentation automatique en azote liquide, destinĂ© au maintien des dĂ©tecteurs Ă basse tempĂ©rature, a Ă©tĂ© amĂ©liorĂ© et fiabilisĂ©. Lâensemble du dispositif a Ă©tĂ© mis en place sur une ligne de faisceau de lâaccĂ©lĂ©rateur tandem avec le concours du personnel technique de lâaccĂ©lĂ©rateur.La premiĂšre expĂ©rience utilisant le dispositif ORGAM a Ă©tĂ© rĂ©alisĂ©e en juillet 2009. Cette expĂ©rience, dont les donnĂ©es ont Ă©tĂ© analysĂ©es dans le cadre de ce travail, visait Ă Ă©tudier les collisions profondĂ©ment inĂ©lastiques entre un faisceau de 36S accĂ©lĂ©rĂ© Ă 154 MeV, et une cible de 70Zn. Un dispositif permettant la dĂ©tection des particules chargĂ©es Ă©mises Ă grand angle a Ă©tĂ© utilisĂ© afin dâidentifier les fragments de ces collisions. Il nâa pas Ă©tĂ© possible, du fait du fond important induit par la diffusion Ă©lastique du faisceau dans la cible, dâidentifier directement ces fragments. LâĂ©tude des coĂŻncidences gamma-gamma avec le dĂ©tecteur ORGAM a cependant permis de mettre en Ă©vidence de nombreuses cascades de photons dĂ©sexcitant des noyaux potentiellement produits par les rĂ©actions dâintĂ©rĂȘt.Les donnĂ©es recueillies au cours dâune autre expĂ©rience, rĂ©alisĂ©e auprĂšs du tandem dâOrsay en 2005, ont Ă©tĂ© analysĂ©es dans le cadre de ce travail. Cette expĂ©rience, visant Ă produire par fusion Ă©vaporation entre un faisceau de 14C Ă 25 MeV et une cible de 48Ca, les noyaux de 59Mn et de 57Cr, a permis dâĂ©tablir une partie du spectre en Ă©nergie dâexcitation de ces noyaux, jusqu'Ă une Ă©nergie dâexcitation supĂ©rieure Ă 3 MeV.Une Ă©tude thĂ©orique des noyaux de chrome impairs de la couche fp a Ă©tĂ© tentĂ©e Ă lâaide dâun modĂšle phĂ©nomĂ©nologique de couplage intermĂ©diaire. Ce modĂšle a permis une description satisfaisante du 53Cr. Les prĂ©dictions du modĂšle, qui ne prend pas en compte lâinteraction entre nuclĂ©ons de valence, se sont avĂ©rĂ©es beaucoup moins satisfaisante pour les noyaux de 55Cr et 57Cr.This PhD thesis was prepared within the nuclear structure group of IPN Orsay. The work presented aimed to produce neutron rich fp shell nuclei through heavy ion collisions at the tandem accelerator of IPN, and to study them using gamma spectroscopy. For this purpose, a germanium gamma array called ORGAM, and dedicated to high resolution gamma spectroscopy, was set up at the tandem accelerator. During the year 2008/2009, the individual germanium detectors were tested and repaired, as well as their ancillary anti-Compton shielding. At the same time, the liquid nitrogen auto-fill system was improved for better reliability. The array was finally set up on a beam line of the accelerator.The first experiment using the ORGAM array was performed in July 2009. This experiment aimed to study fully damped deep-inelastic collisions between a 36S beam accelerated to 154 MeV, and a 70Zn target. An additional charged particle detection system was used to detect interesting fragments emitted at backward angles. It was not possible to separate these fragments from the background induced by backscattered ions from the beam. Nevertheless, the study of gamma-gamma coincidences detected with the ORGAM array allowed to identify gamma cascades de-exciting nuclei potentially produced through the mechanism of interest. Data accumulated during another experiment performed at the tandem accelerator in 2005 were analyzed. Fusion-evaporation reaction between a 25 MeV, 14C beam focused on a 48Ca target produced the 57Cr and 59Mn nuclei, whose energy spectra were established up to 3 MeV.We attempted to study theoretically odd Chromium isotopes with a simple model based on the intermediate coupling scheme. This model, which doesnât take into account correlation between valence nucleons, described in satisfactory way the semi-magic + 1 neutron, 53Cr, but failed to do so for mid-shell nuclei 55Cr and 57Cr
Collisions profondĂ©ment inĂ©lastiques entre ions lourds auprĂšs du Tandem dâOrsay & Spectroscopie gamma des noyaux exotiques riches en neutrons de la couche fp avec le multi-dĂ©tecteur germanium ORGAM
This PhD thesis was prepared within the nuclear structure group of IPN Orsay. The work presented aimed to produce neutron rich fp shell nuclei through heavy ion collisions at the tandem accelerator of IPN, and to study them using gamma spectroscopy. For this purpose, a germanium gamma array called ORGAM, and dedicated to high resolution gamma spectroscopy, was set up at the tandem accelerator. During the year 2008/2009, the individual germanium detectors were tested and repaired, as well as their ancillary anti-Compton shielding. At the same time, the liquid nitrogen auto-fill system was improved for better reliability. The array was finally set up on a beam line of the accelerator.The first experiment using the ORGAM array was performed in July 2009. This experiment aimed to study fully damped deep-inelastic collisions between a 36S beam accelerated to 154 MeV, and a 70Zn target. An additional charged particle detection system was used to detect interesting fragments emitted at backward angles. It was not possible to separate these fragments from the background induced by backscattered ions from the beam. Nevertheless, the study of gamma-gamma coincidences detected with the ORGAM array allowed to identify gamma cascades de-exciting nuclei potentially produced through the mechanism of interest. Data accumulated during another experiment performed at the tandem accelerator in 2005 were analyzed. Fusion-evaporation reaction between a 25 MeV, 14C beam focused on a 48Ca target produced the 57Cr and 59Mn nuclei, whose energy spectra were established up to 3 MeV.We attempted to study theoretically odd Chromium isotopes with a simple model based on the intermediate coupling scheme. This model, which doesnât take into account correlation between valence nucleons, described in satisfactory way the semi-magic + 1 neutron, 53Cr, but failed to do so for mid-shell nuclei 55Cr and 57Cr.Les travaux effectuĂ©s au cours de cette thĂšse au sein du groupe de structure nuclĂ©aire de lâIPN dâOrsay sâarticulent autour de la production, en vue dâune Ă©tude par spectroscopie gamma, de noyaux exotiques riches en neutron de la couche fp. Dans ce cadre, nous avons mis en place, auprĂšs de lâaccĂ©lĂ©rateur Tandem dâOrsay, un multi-dĂ©tecteur au germanium baptisĂ© ORGAM, destinĂ© Ă la spectroscopie gamma Ă haute rĂ©solution. Au cours de lâannĂ©e 2008-2009, les dĂ©tecteurs amenĂ©s Ă composer ORGAM ont Ă©tĂ© testĂ©s individuellement, ainsi que le dispositif annexe de rĂ©jection Compton, en coopĂ©ration avec la division instrumentation du laboratoire. ParallĂšlement, le systĂšme dâalimentation automatique en azote liquide, destinĂ© au maintien des dĂ©tecteurs Ă basse tempĂ©rature, a Ă©tĂ© amĂ©liorĂ© et fiabilisĂ©. Lâensemble du dispositif a Ă©tĂ© mis en place sur une ligne de faisceau de lâaccĂ©lĂ©rateur tandem avec le concours du personnel technique de lâaccĂ©lĂ©rateur.La premiĂšre expĂ©rience utilisant le dispositif ORGAM a Ă©tĂ© rĂ©alisĂ©e en juillet 2009. Cette expĂ©rience, dont les donnĂ©es ont Ă©tĂ© analysĂ©es dans le cadre de ce travail, visait Ă Ă©tudier les collisions profondĂ©ment inĂ©lastiques entre un faisceau de 36S accĂ©lĂ©rĂ© Ă 154 MeV, et une cible de 70Zn. Un dispositif permettant la dĂ©tection des particules chargĂ©es Ă©mises Ă grand angle a Ă©tĂ© utilisĂ© afin dâidentifier les fragments de ces collisions. Il nâa pas Ă©tĂ© possible, du fait du fond important induit par la diffusion Ă©lastique du faisceau dans la cible, dâidentifier directement ces fragments. LâĂ©tude des coĂŻncidences gamma-gamma avec le dĂ©tecteur ORGAM a cependant permis de mettre en Ă©vidence de nombreuses cascades de photons dĂ©sexcitant des noyaux potentiellement produits par les rĂ©actions dâintĂ©rĂȘt.Les donnĂ©es recueillies au cours dâune autre expĂ©rience, rĂ©alisĂ©e auprĂšs du tandem dâOrsay en 2005, ont Ă©tĂ© analysĂ©es dans le cadre de ce travail. Cette expĂ©rience, visant Ă produire par fusion Ă©vaporation entre un faisceau de 14C Ă 25 MeV et une cible de 48Ca, les noyaux de 59Mn et de 57Cr, a permis dâĂ©tablir une partie du spectre en Ă©nergie dâexcitation de ces noyaux, jusqu'Ă une Ă©nergie dâexcitation supĂ©rieure Ă 3 MeV.Une Ă©tude thĂ©orique des noyaux de chrome impairs de la couche fp a Ă©tĂ© tentĂ©e Ă lâaide dâun modĂšle phĂ©nomĂ©nologique de couplage intermĂ©diaire. Ce modĂšle a permis une description satisfaisante du 53Cr. Les prĂ©dictions du modĂšle, qui ne prend pas en compte lâinteraction entre nuclĂ©ons de valence, se sont avĂ©rĂ©es beaucoup moins satisfaisante pour les noyaux de 55Cr et 57Cr
Collisions profondément inélastiques entre ions lourds auprÚs du Tandem d'Orsay & Spectroscopie gamma des noyaux exotiques riches en neutrons de la couche fp avec le multi-détecteur germanium ORGAM
Les travaux effectuĂ©s au cours de cette thĂšse au sein du groupe de structure nuclĂ©aire de l IPN d Orsay s articulent autour de la production, en vue d une Ă©tude par spectroscopie gamma, de noyaux exotiques riches en neutron de la couche fp. Dans ce cadre, nous avons mis en place, auprĂšs de l accĂ©lĂ©rateur Tandem d Orsay, un multi-dĂ©tecteur au germanium baptisĂ© ORGAM, destinĂ© Ă la spectroscopie gamma Ă haute rĂ©solution. Au cours de l annĂ©e 2008-2009, les dĂ©tecteurs amenĂ©s Ă composer ORGAM ont Ă©tĂ© testĂ©s individuellement, ainsi que le dispositif annexe de rĂ©jection Compton, en coopĂ©ration avec la division instrumentation du laboratoire. ParallĂšlement, le systĂšme d alimentation automatique en azote liquide, destinĂ© au maintien des dĂ©tecteurs Ă basse tempĂ©rature, a Ă©tĂ© amĂ©liorĂ© et fiabilisĂ©. L ensemble du dispositif a Ă©tĂ© mis en place sur une ligne de faisceau de l accĂ©lĂ©rateur tandem avec le concours du personnel technique de l accĂ©lĂ©rateur.La premiĂšre expĂ©rience utilisant le dispositif ORGAM a Ă©tĂ© rĂ©alisĂ©e en juillet 2009. Cette expĂ©rience, dont les donnĂ©es ont Ă©tĂ© analysĂ©es dans le cadre de ce travail, visait Ă Ă©tudier les collisions profondĂ©ment inĂ©lastiques entre un faisceau de 36S accĂ©lĂ©rĂ© Ă 154 MeV, et une cible de 70Zn. Un dispositif permettant la dĂ©tection des particules chargĂ©es Ă©mises Ă grand angle a Ă©tĂ© utilisĂ© afin d identifier les fragments de ces collisions. Il n a pas Ă©tĂ© possible, du fait du fond important induit par la diffusion Ă©lastique du faisceau dans la cible, d identifier directement ces fragments. L Ă©tude des coĂŻncidences gamma-gamma avec le dĂ©tecteur ORGAM a cependant permis de mettre en Ă©vidence de nombreuses cascades de photons dĂ©sexcitant des noyaux potentiellement produits par les rĂ©actions d intĂ©rĂȘt.Les donnĂ©es recueillies au cours d une autre expĂ©rience, rĂ©alisĂ©e auprĂšs du tandem d Orsay en 2005, ont Ă©tĂ© analysĂ©es dans le cadre de ce travail. Cette expĂ©rience, visant Ă produire par fusion Ă©vaporation entre un faisceau de 14C Ă 25 MeV et une cible de 48Ca, les noyaux de 59Mn et de 57Cr, a permis d Ă©tablir une partie du spectre en Ă©nergie d excitation de ces noyaux, jusqu'Ă une Ă©nergie d excitation supĂ©rieure Ă 3 MeV.Une Ă©tude thĂ©orique des noyaux de chrome impairs de la couche fp a Ă©tĂ© tentĂ©e Ă l aide d un modĂšle phĂ©nomĂ©nologique de couplage intermĂ©diaire. Ce modĂšle a permis une description satisfaisante du 53Cr. Les prĂ©dictions du modĂšle, qui ne prend pas en compte l interaction entre nuclĂ©ons de valence, se sont avĂ©rĂ©es beaucoup moins satisfaisante pour les noyaux de 55Cr et 57Cr.This PhD thesis was prepared within the nuclear structure group of IPN Orsay. The work presented aimed to produce neutron rich fp shell nuclei through heavy ion collisions at the tandem accelerator of IPN, and to study them using gamma spectroscopy. For this purpose, a germanium gamma array called ORGAM, and dedicated to high resolution gamma spectroscopy, was set up at the tandem accelerator. During the year 2008/2009, the individual germanium detectors were tested and repaired, as well as their ancillary anti-Compton shielding. At the same time, the liquid nitrogen auto-fill system was improved for better reliability. The array was finally set up on a beam line of the accelerator.The first experiment using the ORGAM array was performed in July 2009. This experiment aimed to study fully damped deep-inelastic collisions between a 36S beam accelerated to 154 MeV, and a 70Zn target. An additional charged particle detection system was used to detect interesting fragments emitted at backward angles. It was not possible to separate these fragments from the background induced by backscattered ions from the beam. Nevertheless, the study of gamma-gamma coincidences detected with the ORGAM array allowed to identify gamma cascades de-exciting nuclei potentially produced through the mechanism of interest. Data accumulated during another experiment performed at the tandem accelerator in 2005 were analyzed. Fusion-evaporation reaction between a 25 MeV, 14C beam focused on a 48Ca target produced the 57Cr and 59Mn nuclei, whose energy spectra were established up to 3 MeV.We attempted to study theoretically odd Chromium isotopes with a simple model based on the intermediate coupling scheme. This model, which doesn t take into account correlation between valence nucleons, described in satisfactory way the semi-magic + 1 neutron, 53Cr, but failed to do so for mid-shell nuclei 55Cr and 57Cr.PARIS11-SCD-Bib. Ă©lectronique (914719901) / SudocSudocFranceF
rapid onset of collectivity in the vicinity of 78Ni
4 pages, ReVTeXgamma-rays following the ÎČ and ÎČ-n decay of the very neutron rich 84Ga produced by photo-ïŹssion of 238U have been studied at the newly built ISOL facility of IPN Orsay: ALTO. Two activities were observed and assigned to two ÎČ-decaying states: 84gGa, I = (0â) and 84mGa, I= (3â,4â). Excitation energies of the 2+1 and 4+1 excited states of 84Ge were measured at E(2+1 ) = 624.3 keV and E(4+1 ) = 1670.1 keV. Comparison with HFB+GCM calculations allows to establish the collective character of this nucleus indicating a substantial N=50 core polarization. The excitation energy of the 1/2+1 state in 83Ga known to carry a large part of the neutron 3s1/2 strength was measured at 247.8keV. Altogether these data allow to conïŹrm the new single particle state ordering which appears immediately after the double Z=28 and N=50 shell closure and to designate 78Ni as a fragile and easily polarized doubly-magic core