P. Malmborg

Cross sections for the production of residual nuclides by low- and medium-energy protons from the target elements C, N, O, Mg, Al, Si, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Nb, Ba and Au

Abstract Cross sections for residual nuclide production by p-induced reactions were measured from thresholds up to 2.6 GeV using accelerators at CERN/Geneve, IPN/Orsay, KFA/Julich, LANL/Los Alamos, LNS/Saclay, PSI/Villigen, TSL/Uppsala, LUC/Louvain La Neuve. The target elements C, N, O, Mg, Al, Si, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Nb, Ba and Au were investigated. Residual nuclides were measured by X- and γ-spectrometry and by Accelerator Mass Spectrometry (AMS). The measured cross sections were corrected for interfering secondary particles in experiments with primary proton energies above 200 MeV. Our consistent database covers presently ca 550 nuclear reactions and contains nearly 15000 individual cross sections of which about 10000 are reported here for the first time. They provide a basis for model calculations of the production of cosmogenic nuclides in extraterrestrial matter by solar and galactic cosmic ray protons. They are of importance for many other applications in which medium energy nuclear reactions have to be considered ranging from astrophysics over space and environmental sciences to accelerator technology and accelerator-based nuclear waste transmutation and energy amplification. The experimental data are compared with theoretical ones based on calculations using an INC/E model in form of the HETC/KFA2 code and on the hybrid model of preequilibrium reactions in form of the AREL code.

Production of residual nuclei by proton-induced reactions on C, N, O, Mg, AI and Si

Cross sections for the production of residual nuclides by p-induced reactions are the basic nuclear quantities for an accurate modelling of the interaction of solar cosmic protons with matter. In a series of irradiation experiments at the cyclotron of the Svedberg Laboratory/University of Uppsala sixteen different target elements were investigated for proton energies up to 100 MeV in order to determine such thin-target excitation functions. Residual nuclides were measured by gamma-spectrometry and, in the case of10Be and26Al, by accelerator mass spectrometry. Here, we report results for the light target elements C, N, O, Mg, Al, and Si including also new cross sections for the production of10Be and26Al from aluminum for p-energies between 100 MeV and 200 MeV. The latter were derived from targets irradiated earlier at the IPN Orsay. The new experimental data are compared with earlier work and analyzed in the framework of the hybrid model of preequilibrium reactions investigating several options with respect to the choice of nuclear masses including also corrections for shell effects of nuclear masses and level densities.

Synthesis of racemic (+) and (−) N-[methyl-11C]nomifensine, a ligand for evaluation of monoamine re-uptake sites by use of positron emission tomography

The synthesis of racemic or enantiomeric N-[methyl-11C]nomifensine (1,2,3,4-tetrahydro-2-[11C]methyl-4-phenyl-8-isoquinolinamine), a potential ligand for the evaluation of monoamine re-uptake sites at the presynaptic dopaminergic terminals, using the appropriate N-desmethylcompounds and [11C]methyl iodide is described. The radiochemical conversion of [11C]methyl iodide to [11C]nomifensine was in the order of 85-95%. Radiochemical purity of the LC-purified radiopharmaceutical was in the order of 98-99%. In a typical run, starting with 120 mCi (4.4 GBq) of [11C]carbon dioxide, 380 MBq (8.6% not decay corrected) of a final solution was obtained within 55 min (roughly 20 min of that is related to transport time). The specific radioactivity corresponding to the [11C]methyl iodide was 30-100 mCi/mumol (typical: a total mass of 30 micrograms and 150 MBq was administered in the PET-studies). A procedure for resolving the racemate of N-desmethylnomifensine (1,2,3,4-tetrahydro-4-phenyl-8-isoquinoline) into its enantiomers using triacetylcellulose as the stationary phase and methanol/ethanol as solvents by use of LC is also described.

Studies of proton beam penetration in nitrogen-gas targets with respect to production and specific radioactivity of carbon-11

Abstract This paper presents a study of proton beam penetration in nitrogen-gas targets with special attention to the effect of the target system volume. The proton beam penetration and scattering in the target were studied by photographing the light emitted by nitrogen molecules in the beam volume of the target. Gas targets irradiated both under static and flow-through conditions were investigated. A strongly volume-dependent beam penetration in nitrogen-gas targets was observed. The increase in beam penetration as related to the tabulated particle range was found to be higher in a gas target irradiated under flow-through conditions than in the target under static condition. A model for estimation of beam penetration in gas targets was developed. On the basis of the results obtained in the photographic study, a target system for production of [ 11 C]carbon dioxide with high specific radioactivity was constructed and used. The specific radioactivity of the [ 11 C]carbon dioxide was in the order of 2 Ci/μmol at EOB for 5–10 μA beam currents of 10.4 MeV protons on the target and irradiation times of 10 min.

Rapid separation of 110In from enriched Cd targets by thermal diffusion

110In (T12 = 69 min, 62% β+) is a short-lived positron emitting indium isotope that can be produced in high radioactivity amounts by a low-energy accelerator and from an enriched 110Cd-target. We present a simple, non-destructive and rapid method to separate radioactive indium isotopes from cadmium targets with the special aim to produce 110In. The irradiated target foils were heated up to 306°C, that is close to the melting point of cadmium. At this temperature the indium isotopes were diffusing out to the surface of the foils. After the end of the heating a high concentration of indium radioactivity was found at the surface of the target. By dipping the foils into a weak acid more than 60% of the radioactivity was etched off the target with less than 2% loss of the target material.

Cross Sections for the Production of Radionuclides by Proton-Induced Reactions on W, Ta, Pb and Bi from Thresholds up to 2.6 GeV

Extending our earlier work on cross sections for the production of residual nuclides by proton-induced reactions, the production of radionuclides from the target elements Ta, W, Pb, and Bi was investigated from thresholds up to 2.6 GeV using accelerators at LNS/Saclay, PSI/Villigen, and TSL/Uppsala. Residual nuclides were measured by X- and γ-spectrometry. We obtained more than 5000 new individual cross sections for 402 reactions. Together with the yet not published cross sections for the target elements Rb, Mo, Rh, Ag, In, Te and La and with published results of special investigations of cosmogenic nuclides, our entire consistent data base now covers the target elements C, N, O, Mg, Al, Si, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Rb, Sr, Y, Zr, Nb, Mo, Rh, Ag, In, Te, Ba, La, Ta, W, Au, Pb and Bi. It contains data for about 1300 nuclear reactions and more than 24000 cross sections. Here, some phenomenological aspects of the residual nuclide production from heavy target elements are described and the capabilities of nuclear models to predict the respective cross sections are discussed.

Distribution and stability in the rat of a 76Br/125I-labelled polypeptide, epidermal growth factor

A positron-emitting isotope of bromine, 76Br, with a half-life of 16.2 h, was produced using the reaction natBr(p, xn)76Kr. Labelling of mouse epidermal growth factor (EGF) with 76Br was optimized, using the chloramine-T method, obtaining a maximal radiochemical yield of 53%. In tests with receptor-rich, cultured glioma cells, [76Br]EGF and [125I]EGF bound equally well. A study of the distribution and stability of [76Br]EGF and [125I]EGF in normal rat was carried out. The distribution of both radioisotopes was similar, however, the percentage of 76Br bound to the high molecular weight fraction in the plasma, liver and kidney was greater than that of 125I.

110Sn/110In--a new generator system for positron emission tomography.

A generator system, 110Sn/110In, is suggested for use in the labelling of leukocytes with this short-lived (t1/2 = 1.15 h) positron emitting (62%) isotope of indium. The half-life gives the labelled leukocytes time to be adequately distributed but is short enough to allow repeated studies within a few hours. The mother radionuclide 110Sn (t1/2 = 4.15 h) is produced by the reaction natIn(p, xn)110Sn which has a maximum cross-section of 110 mb at approx. 70 MeV and a practical yield of 400 MBq/microAh.

11C-Methionine Kinetics in Pregnant Rhesus Monkeys Studied by Positron Emission Tomography: A New Approach to Feto-Maternal Metabolism

Abstract. By use of Positron Emission Tomography (PET), dynamic studies of the metabolism within the fetomaternal unit can be performed using various tracers. Many compounds like amino acids, carbohydrates, fatty acids and drugs can be labelled with 11C and used as tracers.

Distribution of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in experimental animals studied by postiron emission tomography and whole body autoradiography

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a selective potent neurotoxin which has induced a syndrome similar to parkinsonism both in man and in monkeys. At autopsy degeneration of pigmented nerve cells in the pars compacta of the substantia nigra has been confirmed. The regional distribution of intravenously administered 1-(11C-methyl)-4-phenyl-1,2,3,6-tetrahydropyridine (11C-MPTP) in the brain of Rhesus monkeys was studied by positron emission tomography and the whole body distribution in mice was documented by autoradiography and by impulse counting of selected tissues. A very rapid and high uptake of 11C-MPTP derived radioactivity was seen in areas corresponding to striatum and midbrain, including the substantia nigra area. No elimination from these regions was seen during the study period of 2 h. The uptake was in the order of 7-8 times the homogenous distribution of the radioactivity in the monkey. The uptake was generally high also in other regions of the brain, but there some elimination could be distinguished. Pretreatment of the monkey with spiperone, a selective dopamine receptor antagonist, did not alter uptake nor the kinetics of the 11C-MPTP derived radioactivity. Thus 11C-MPTP does not have a high affinity for postsynaptic dopamine receptors. A remarkably high uptake of 11C-MPTP derived radioactivity was seen in the eye of the monkey. The selective uptake of radioactivity in the eye was also confirmed in pigmented but not in albino mice. The melanin affinity of MPTP may cause high intracellular concentrations of the compound or its metabolites in the melanin containing nerve cells in substantia nigra, which may explain the serious vulnerability of these neurons to MPTP.