Gert Goeminne

Experimental determination of the 14 N ( n , p ) 14 C reaction cross section for thermal neutrons

The 17O(n_th,alpha)14C reaction cross section was determined at the high flux reactor of the ILL in Grenoble relative to the known 14N(n_th,p)14C cross section. The 17O(n_th,alpha)14C measurements were performed with several highly enriched oxygen gas samples and the flux calibration was done with 14N_2 from the air. This resulted in a precise value of (244+/-7)mb for the 17O(n_th,alpha)14C cross section.

Preparation and characterisation of an 39Ar sample and study of the 39Ar(nth, α)36S reaction

Abstract The 39 Ar ( n th , α ) 36 S reaction has been studied for the first time. A sample containing 2.85×10 14 39 Ar atoms was produced at the ISOLDE facility at CERN. The number of 39 Ar atoms in the layer was determined by measuring the 39 Ar β -activity using a primary standardisation method. Subsequently, the sample was irradiated with thermal neutrons at the High Flux Reactor of the Institut Laue–Langevin. An upper limit of 0.29 b was obtained for the 39 Ar ( n th , α ) 36 S reaction cross-section.

High resolution measurement of the 36Cl(n,p)36S and 36Cl(n,α)33P reactions

Abstract New high resolution measurements of the 36 Cl(n,p) 36 S and 36 Cl(n,α) 33 P reaction cross sections are reported. Some 20 resonances have been identified in the neutron energy region from 0.1 keV to 350 keV.

Thermal neutron induced (n, p) and (n, alpha) reactions on Ar-37

The 37Ar(n_th,alpha)34S and 37Ar(n_th,p)37Cl reactions were studied at the high flux reactor of the ILL in Grenoble. For the 37Ar(n_th,alpha_0) and 37Ar(n_th,p) reaction cross sections, values of (1070+/-80)b and (37+/-4)b, respectively, were obtained. Both values are about a factor 2 smaller than results of older measurements. The observed suppression of the 37(n_th,alpha_1) transition could be verified from theoretical considerations. Finally, evidence was found for the two-step 37Ar(n_th,gamma-alpha) process. Comment: 11 pages, 5 figures, accepted for publication in Nuclear Physics A

Investigation of the Ar-37(n,p)Cl-37, Ar-37(n,alpha)S-34 and Ar-39(n,alpha)S-36 reactions at various stellar temperatures

A first experimental study of the neutron induced charged particle reactions on (37)A and Ar-39 as a function of the neutron energy has been made. Therefore, complementary measurements were performed with thermal neutrons at the High Flux Reactor of the ILL (Grenoble, France) and with resonance neutrons at the GELINA neutron spectrometer of the IRMM (Geel, Belgium). The stellar cross sections, which were calculated from the obtained data, show important discrepancies with the theoretical values used in recent network calculations.

Experimental determination of the {sup 36}Cl(n,p){sup 36}S and {sup 36}Cl(n,{alpha}){sup 33}P reaction cross sections and the consequences on the origin of {sup 36}S

The {sup 36}Cl(n,p){sup 36}S and {sup 36}Cl(n,{alpha}){sup 33}P reaction cross sections have been studied with resonance neutrons at the linear accelerator GELINA of the IRMM in Geel (Belgium) and have been determined up to approximately 250 keV using the time-of-flight technique. In this energy region, 17 resonances were observed, whereas eight were identified before. For some resonances the resonance strength, the spin, and the total width could be determined. From the obtained cross section data, the MACS has been calculated by numerical integration. These updated MACS values were used in stellar models to trace the origin of the rare isotope {sup 36}S.

Preparation of highly enriched O-17 samples for neutron-induced reaction studies

Suitable O-17 samples are required for the study of the O-17(n,alpha)C-14 reaction with various detectors, The electrospraying of metal oxides enriched in O-17 onto an Al substrate yielded negative results: no O-17(n(th),alpha) reactions were observed when irradiating these samples with thermal neutrons, These tests demonstrated the need to minimize the B-10 content in sample and backing, since the B-10(n(th),alpha(1)) reaction causes a strongly disturbing background. Good results were obtained in the reactor experiments using gaseous samples (O-17 enrichments of 58.2%, 72.1% and 85.5%) with a dedicated experimental setup. The experimental conditions being quite different at accelerators, an alternative method was developed to prepare samples suited for use in ionization chambers, For this purpose, O-17 ions were implanted in ultra-pure Al foils. The thickest sample prepared in this way contains 8 x 10(18) atoms of O-17, with a B-10/O-17 ratio of 10(-4)

Preparation and characterisation of an Ar-39 sample and study of the Ar-39(n(th), alpha)S-36 reaction

Abstract The 39 Ar ( n th , α ) 36 S reaction has been studied for the first time. A sample containing 2.85×10 14 39 Ar atoms was produced at the ISOLDE facility at CERN. The number of 39 Ar atoms in the layer was determined by measuring the 39 Ar β -activity using a primary standardisation method. Subsequently, the sample was irradiated with thermal neutrons at the High Flux Reactor of the Institut Laue–Langevin. An upper limit of 0.29 b was obtained for the 39 Ar ( n th , α ) 36 S reaction cross-section.

Preparation and characterisation of an sample and study of the reaction

Abstract The 39 Ar ( n th , α ) 36 S reaction has been studied for the first time. A sample containing 2.85×10 14 39 Ar atoms was produced at the ISOLDE facility at CERN. The number of 39 Ar atoms in the layer was determined by measuring the 39 Ar β -activity using a primary standardisation method. Subsequently, the sample was irradiated with thermal neutrons at the High Flux Reactor of the Institut Laue–Langevin. An upper limit of 0.29 b was obtained for the 39 Ar ( n th , α ) 36 S reaction cross-section.

Experimental determination of the14N(n,p)14Creaction cross section for thermal neutrons

The 17O(n_th,alpha)14C reaction cross section was determined at the high flux reactor of the ILL in Grenoble relative to the known 14N(n_th,p)14C cross section. The 17O(n_th,alpha)14C measurements were performed with several highly enriched oxygen gas samples and the flux calibration was done with 14N_2 from the air. This resulted in a precise value of (244+/-7)mb for the 17O(n_th,alpha)14C cross section.