L. Quaglia

Analyse par reaction nucleaire de l'oxygene et du carbone en couche mince a la surface des metaux Précautions à prendre lors des mesures sur des cibles solides de carbone

Zusammenfassung A preliminary study has been made to define valid experimental conditions in order to determine the quantity of oxygen and carbon, retained by adsorption or chemical reaction, at the surface of high purity metals. A method of analysis by charged-particle nuclear reactions was applied. The first experimental results are given for aluminium metal. These results are compared to those, obtained by one of us, for the same samples, using the activation analysis technique with 2 MeV tritons. In a later paper, we shall report on our results with other metals.

Fonction d'excitation de la réaction 12C(d,p0)13C entre 400 et 1350 keV — distributions angulaires

Abstract The excitation function of the 12 C(d,p 0 ) 13 C has been measured at θ = 150° for 400 to 1350 keV deuteron energy. The angular distribution has been measured from 80° up to 160°. These measurements have been performed in order to make possible the use of this reaction for superficial carbon determination by direct observation of the emitted protons.

Utalisation des deutons et des tritons de faibles energies pour le dosage du carbone et de l’oxygene presents a la surface d’echantillons metalliques

The oxygen and carbon concentrations on metal surfaces were determined by two methods. The first method was based on the detection of the emitted particles in the12C(d,p)13C and16O(d, p)17O reactions, the second one on the measurement of the induced radioactivities in the12C(d,n)13N and16O(t,n)18F reactions, respectively. The results, obtained by the two different methods for high purity metals, were in agreement. A type of error which exists in the determination of trace amounts of carbon and oxygen in pure metals by combustion and reductive fusion was quantitatively demonstrated. This error exists also in the determination of oxygen by 14 MeV neutron bombardment.

Production of oxygen-15, nitrogen-13 and carbon-11 and of their low molecular weight derivatives for biomedical applications

Abstract The production and the medical use of the short-lived radioisotopes of the 3 major elements of the biosphere, 13N, 11C and 15O, require the vicinity of a cyclotron, of radiochemistry laboratories and of a suitably equipped medical unit. The authors describe and discuss the methodological and practical aspects of the routine, high efficiency, production of these gases, with the specifications that result from their medical use.

Oxygen, carbon and nitrogen determination by means of nuclear reactions

After a brief account of the general principles of the method, a description is given of some aspects of the problems which have been investigated in detail: behaviour of targets under ion-bombardment, determination of oxygen, carbon and nitrogen at the surface of metallic targets, and determination of carbon and nitrogen in tantalum layers metallized on glass.

Application of alpha particle induced x-ray emission to the determination of yttrium, lanthanum, cerium and neodymium in apatite minerals

Abstract The concentrations of Y, La, Ce and Nd are determined in apatite mineral by the technique of PIXE using an 18 MeV alpha particle beam (cyclotron). The method involves the dissolution of an apatite sample in concentrated perchloric acid, Y and rare-earth separation from the phosphate matrix by extraction with di-(2-ethylhexyl) phosphoric acid. Under the described operating conditions, the PIXE method yields a precision of about 4.7% for Y, 2.7% for La, 2.5% for Ce and 17.8% for Nd. The calculated detection limits are 2 ωg for Y, 2.5 ωg for La, 3 ωg for Ce and 16 ωg for Nd. Comparison with available data for fluoroapatite from Cerro de Mercado (Mexico) indicates relatively good agreement with previously reported optical spectrographic results for Y and with neutron-activation analysis for La, Ce and Nd values.

Automated preparation of carbon-11 ethanol and carbon-11 butanol for human studies using positron emission tomography

An automated continuous flow process has been developed for the synthesis of11C-ethanol and11C-butanol. These alcohols were synthesized via the same route. The reaction of11CO2 with methylmagnesium bromide or with n-propylmagnesium chloride, followed by a lithium aluminum hydride reduction and hydrolysis produced respectively11C-ethanol and11C-butanol. Preparation can be completed in 25 min. In each case the radiochemical purity, as determined by high pressure liquid chromatography /HPLC/ was greater than 98%. Biological quality control shows that the products are suitable for human use. The process has been completely automated to limit radiation exposure to personnel, reduce preparation time, and increase reproducibility.

Automated production of carbon-11 labelled acetate to allow detection of transient myocardial ischemia in man, using positron emission tomography

The synthesis of11C-acetate has been achieved via carbonation of methyl magnesium bromide with11C-labelled carbon dioxide. Using this procedure, 7.4 GBq /200 mCi/ of11CO2 produced by the14N/P,α/11C nuclear reaction, was converted, within 20 min into11C-acetate with an activity higher than 2.22 GBq /60 mCi/. Chemical and biologic quality control shows that the product is pure, sterile, and pyrogen-free and therefore suitable for human use. Handling considerable amounts of activity has led us to automate the11C-acetate synthesis. The different parts of the system-programmable controller, sensors, automatic neutralization system-are described in detail.

Evolution de la teneur en oxygene lors de son dosage en surface par reaction nucleaire

Abstract The behaviour of the oxygen content at the surface of several metals, during the bombardment by charged particles has been investigated. This study has been achieved in order to determine the best experimental conditions and to put the users of this method on their guards against some unexpected behaviour of oxygen content.

Determination du debit optimum pour la production par cyclotron de gaz radioactifs a partir de cibles gazeuses

Abstract When short-lived radioactive gases are produced by cyclotron-irradiated gaseous targets, the yield of activity at the site of delivery depends on the flow rate in the gas-carrying line. The authors present a single model which allows to compute the flow rate D giving a maximum yield of production. The following formula is used: D = 1 2 [λV r +√(λ 2 V r 2 +4λ 2 V r V c )] , where λ is the decay constant of the produced radionuclide, Vc the volume of gas in the target, and Vr the inner volume of the gas-carrying line. The only unknown parameter, Vr, can be derived from a single curve of growing of the activity at a trial flow rate. The method is concretely applied to the production of 15O, 13N and 11C.