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Thin- and thick-target excitation functions of 188,189,191Ptradionuclides were experimentally determined by cyclotron irradiation, usingnuclear reactions nat Os(α ,xn) in the energy range up to38 MeV with the Scanditronix-MC40 cyclotron of the Joint Research Centre-Ispra(Italy) of the European Union. Radionuclidic, radiochemical and chemical puritieshave been also measured by use of analytical and radioanalytical techniques.In this paper the result of the experimental thin target excitation functionsof 188,189,191Pt radiotracers produced via nat Os(α,xn) reactions are presented. Two stacks of thin osmium targets were irradiatedat 38 and 28 MeV, respectively. Analytical fittings of the excitation functionsare also presented.

Abstract:: The spectra of 8Begs fragments emitted in the interaction of 100, 200, 300 and 400 MeV 12C with 59Co, 93Nb and 197Au have been measured and analysed. Our analysis suggests that, before breaking up, 12C may suffer a considerable energy loss which increases with increasing incident energy. The amount of excitation energy provided to the target nucleus in this process increases with decreasing charge of the target nucleus.

Abstract: It is suggested that the spectra of the 8Be ground-state (gs) nuclei produced in the interaction of 12C with 59Co at incident energies varying from 8.3 to 33.3MeV/amu can be explained by introducing a dissipative friction interaction mechanism preceding projectile break-up.

The concentrations (ng/m3) of more than 30 trace elements have been determined in the total air particulate matter and in the sizesegregated fractions collected in urban, industrialized, and rural residential areas in northern Italy by means of a multistage inertial impactor with the PM10 inlet. All measurements have been carried out by instrumental neutron activation analysis, except for Pb and Cd, which have been determined by electrothermal atomic absorption spectroscopy. Analytical quality assurance procedures have been developed with special regard to blanks, reagents, and sampling. Total concentrations and the granulometric distribution found in the different locations are reported and compared.

Abstract: High specific activity radiotracers are very suitable for studies related to the toxicological impact of trace elements onto human health. In order to investigate the metabolic behaviour of Low Level Exposure (LLE) to trace elements, it is necessary to carry out in-vitro and in-vivo experiments with tracers whose concentration is of the same order of magnitude as the present environmental exposure values (ng-mgrg/kg day). Preparations, separations and purifications of some No Carrier Added (NCA) radiotracers (48V,95m,96Tc,195m,g,197m,gHg,199Au,202Tl) produced by either cyclotron or nuclear reactor irradiation, are presented and discussed. This work reviews the more recent advances in this field carried out by our groups.

Abstract: Three different cereal cultivated fields (rice, maize/wheat, wheat/barley) were selected and soil samples were collected in order to study the behaviour of the radiocesium deposited over the crops after the Chernobyl accident fall-out (April 1986) together with its distribution at different ground depths. For each field, soil samples were removed during the sowing (Oct–Nov '86), in Spring (Apr '87) and during the harvest time (Jun–Sept '87). The40K concentration and stable potassium content in soil was also evaluated by nuclear spectrometry and by atomic absorption spectrometry. Beside soil sample measurements, the cultivated cereals produced in the 1986 harvest (rice, maize, wheat) were analyzed to evaluate the deposited contamination, and in order to evaluate the contamination during the growth and naturation we also analyzed whole plants (roots, stalks, grains) of the cultivated cereals (rice, wheat, barley) in 1987. Results are presented and discussed.

Abstract: Proton activation analysis is applied to the determination of As in high-purity silicon, ion implanted with nominal doses ranging from 1014 to 1016 atoms/cm2. Both instrumental and radiochemical versions have been developed. The75 As(p, n)75Se,75 As(p, 3n)73Se and75 As(p, pn)74 As nuclear reactions have been considered in order to get the best activation conditions for delayed measurements by gamma spectrometry.

Abstract: A review is given on the use of the Milan Cyclotron in trace element analysis via nuclear activation and X-ray fluorescence and in radioisotope production for medical and biological uses.

Abstract: The production of123I from enriched124Te is described. Preliminary experiments on a distillation separation of iodine from the Te target have been performed and the method seems promising in comparison to the time-consuming chemical separation technique.

Summary The frequency distributions of energy deposition in microscopic volumes for proton beams of various energies and energy spreads were determined by means of a “Rossi type” proportional counter. Tissue equivalent spherical volumes of 0.6, 0.72, 0.80, 1.00, 1.25, 1.50, 1.75, 2.00 µm diameter were simulated. Frequency distributions of energy deposition per unit pathlength are reported and their behaviour as a function of the simulated pathlength, beam energy and energy spread is discussed. The results indicate that energy deposition distributions in microscopic volumes for protons in the range 8–31 MeV are skewsymmetric distributions with a tail on the high energy side, and that degraded beams behave differently from monoenergetic ones. Dose mean lineal energy values have been quoted for beams used in radiobiological experiments.

The preliminary design of a 19-T superconducting high-magnetic-field facility for the Laboratory for Accelerators and Applied Superconductivity is presented. The device uses NbTi, Nb/sub 3/Sn, and V/sub 3/Ga coils giving high field homogeneity in the center regions, and two cryostats that allow separate opening of the NbTi coil and the Nb/sub 3/Sn-V/sub 3/Ga coils. The main design parameters of the facility are reported. Coil stability and stresses are considered, and superconducting cable parameters and magnetic-field characteristics are discussed.<>

The effect of channeling on the Rutherford scattering and the energy distribution of protons with initial energy between 20 and 39 MeV is shown for protons passing through single crystals of Si and W. Dechanneling effect as a function of depth in Si was studied by means of Rutherford scattering along the <111>-axis and an exponential law was found. The energy spectrum of the transmitted protons showed that a distinct group of particles came through, with energy loss less than one half the normal energy loss for W and about 0.6 for Si. Stopping powers for channelled and random particles were calculated using the Bethe-Bloch formula and Bohr's suggestion of close and distant encounters. The agreement of calculated with measured values is discussed. Si riportano i risultati ottenuti nello studio degli effetti dell'incanalamento sullo scattering alla Rutherford e sulla distribuzione energetica di protoni aventi energia iniziale compresa tra 20 e 39 MeV che attraversano monocristalli di Si e W. Lo studio del fenomeno di disincanalamento in Si è stato affrontato utilizzando lo scattering di protoni incidenti lungo l'asse <111>. Si è trovato che il fenomeno segue una legge esponenziale. L'analisi in energia ha dimostrato che esiste un gruppo di protoni che attraversano il cristallo perdendo meno energia dei protoni non incanalati e precisamente di un fottore 0.3÷0.4 nel caso del tungsteno e circa 0.6 per il silicio. Utilizzando la formula di Bethe-Bloch e l'ipotesi di Bohr sugli urti singoli e collettivi si è calcolato il potere di arresto per le particelle incanalate e per quelle casuali. Si discute l'accordo tra i valori calcolati e quelli misurati. Для протонов, пролетающих через монокристаллы кремния и вольфрама, исследуется влияние эффекта каналирования на резерфордовское рассеяние и энергетическое распределение протонов с начальными энергиями от 20 до 39 МэВ. Рассматривался эффект деканалирования, как функция глубины в кремнии изучая резерфордовское рассеяние вдоль оси <111>. Получен экспоненциальный закон для функции, описывающей эффект деканалирования. Спектр прошедших протонов показывает, что резко выраженная группа частиц имеет потери знергии, которые составляют половину от нормальных потерь энергии для вольфрама и около 0.6 для кремния. Вычисляютося тормозные способности для каналированных и неканалированных частиц, используя формулу Блоха и предположение Бора о близких и далеких соударениях. Проводится сравнение расчетных и э]qkспериментальных величин.

Abstract: The increasing concentration of Pt, Pd and Rh in the environment is mainly due to the release of these elements from the catalytic converters of the motorvehicles. This situation makes it necessary to carry out metallotoxicological experiments on both cell cultures and laboratory animals, in order to assess their impact on living organisms after a Long Term and Low Level Exposure (LLE). Both nuclear reactionsnatIr(p,xn) andnatOs(α,xn) were investigated in the energy range up to 45 MeV for protons and 38 MeV for alpha-particles, in order to optimize the irradiation parameters for the production of188,189,191Pt. Several sets of thin- and thick-target excitation functions were determined experimentally by cyclotron irradiation at both Milano and Ispra cyclotrons. This paper reports the irradiation parameters studied and adopted and two radiochemical procedures for the separation of radio-Pt from an Os target, as well as from ruthenium, iridium and gold impurities. These procedures were used to obtain very high specific activity Pt radionuclides in No Carrier Added (NCA) form. Radionuclidic, radiochemical and chemical purity measurements were carred out by the use of several techniques like ψ-spectrometry, ion-exchange radio-chromatography, atomic absorption spectrometry and neutron activation analysis.

Abstract: High Specific Activity Radio-Nuclides (HSARN) are a powerful tool to label a large range of chemical species at very low concentration levels. In order to obtain these radiotracers in a very high specific activity form, it is necessary to optimize the production methods, to separate and purify them from the irradiated target without the addition of inactive carrier, to carry out a series of analytical and radioanalytical tests to determine their ldquotruerdquo specific activity and to verify a series of purity parameters. A review of irradiation methods and nuclear parameters adopted in our laboratories for the preparation of some tens of radiotracers are presented.

Abstract: High specific activity radiotracers, used in studies related to trace elements and human health, must be characterized by the following specific requirements: (i) high specific activity (activity/mass of isotopic carrier), (ii) high activity concentration (activity/volume or mass of substrate), (iii) radionuclidic, radiochemical and chemical purities, (iv) biological compatibility (physiological pH, sterility and physiological values). For this purpose, selective radiochemical separations and quality control procedures have been developed and tested at our laboratories for the production of several NCA radiotracers.

Abstract: Carrier-free201+202Tl have been produced in the cyclotron by (p, xn) reactions on mercury targets and used as a trcer for thallium in metallobiochemistry of heavy metal pollution. The separation of201+202Tl radioisotopes from Hg involved a solvent extraction method leading to labelled univalent Tl(I) ions. This radioactive solution was used to prepare different201+202Tl labelled compounds such as inorganic Tl(III) ions and organic dimethylthallium. Quality controls have been applied directly on the different radioactive solutions immediately before their administrations to rats in order to ensure that thallium had the chemical form expected. A summary of the main results concerning different aspects of the metabolic investigations on rats such as absorption, retention, excretion, transplacental transport and influence of the different chemical forms of thallium on its metabolism is also reported.

Abstract: Proton activation analysis (PAA) can be considered as complementary to NAA for the determination of elements of great environmental importance such as Pb, T1, Ti, Ge, V. The method was calibrated for the determination of lead in biological standard reference materials by instrumental analysis (IPAA), obtaining a detection limit of 0.1 ppm, for this type of matrices. Selective radiochemical separations in order to improve the sensitivity of the contemporary determination of Pb, T1, Ge ... are described in some details. A lead determination in pooled serum and red blood cells of 15 unexposed subjects by instrumental and radio-chemical analysis is carried out.

A method has been developed, based on thermoluminescent dosemeters (TLD), aimed at measuring the absorbed dose in tissue-equivalent phantoms exposed to thermal or epithermal neutrons, separating the contributions of various secondary radiation generated by neutrons. The proposed method takes advantage of the very low sensitivity of CaF2:Tm (TLD-300) to low energy neutrons and to the different responses to thermal neutrons of LiF:Mg,Ti dosemeters with different 6Li percentage (TLD-100, TLD-700, TLD-600). The comparison of the results with those obtained by means of gel dosemeters and activation foils has confirmed the reliability of the method. The experimental modalities allowing reliable results have been studied. The glow curves of TLD-300 after gamma or neutron irradiation have been compared; moreover, both internal irradiation effect and energy dependence have been investigated. For TLD-600, TLD-100 and TLD-700, the suitable fluence limits have been determined in order to avoid radiation damage and loss of linearity.

The interest in the biokinetics of ruthenium and zirconium in humans is justified by the potential radiological risk represented by their radionuclides. Only a few data related to the biokinetics of ruthenium and zirconium in humans are available and, accordingly, the biokinetic models currently recommended by the ICRP for these elements are mainly based on data from animal experiments. The use of stable isotopes as tracers, coupled with a proper analytical technique (nuclear activation analysis with protons) for their determination in biological samples, represents an ethically acceptable methodology for biokinetic investigations, being free from any radiation risk for the volunteer subjects. In this work, the results obtained in eight biokinetic investigations for ruthenium, conducted on a total of three healthy volunteers, and six for zirconium, performed on a total of three subjects, are presented and compared to the predictions of the ICRP models.

Gel dosimetry allows three-dimensional (3D) measurement of absorbed dose in tissue-equivalent dosemeter phantoms. Gel phantoms are imaged using optical techniques. In neutron capture therapy, properly designed gel dosemeters can give 3D dose distributions, due to the various components of the secondary radiation, in phantoms exposed in the thermal or epithermal column of a nuclear reactor. In addition to the therapeutic dose arising from the reaction 10B(n,a)7Li, the other dose components are also obtainable, i.e. the gamma dose (due to reactor background and to the reaction 1H(n,gamma)2H of thermal neutrons with hydrogen), the dose due to protons emitted in the reaction 14N(n,p)14C of thermal neutrons with nitrogen and the dose due to recoil protons resulting from elastic scattering of epithermal neutrons.

The 'history' of the extended range neutron rem counter LINUS, since its first conception in 1990, is reviewed, along with the latest developments. These include the calibration of the initially cylindrical version with nearly monoenergetic neutrons in the energy range 34-66 MeV, a detailed evaluation of the anisotropy of its response function, the construction and calibration of an improved spherical version, and recent measurements in reference high energy stray radiation fields. The instrument can now be considered as being fully characterised. Similar monitors built by other laboratories following the present design have confirmed its performance. The instrument is now in semi-routine use at a number of particle accelerator facilities and is one of several devices used on-board aircraft for assessing the exposure to cosmic rays at commercial flight altitudes.

The well-known Andersson-Braun rem counter is widely employed for radiation protection purposes, but its efficiency shows a marked decrease for neutron energies about 10 MeV. Since the availability of a survey meter with a good sensitivity to higher energies can be very useful, for instance, at many particle accelerator facilities, a neutron monitor with a response function extended up to 400 MeV has been achieved by modifying the structure of the moderator-attenuator of a commercial instrument. The first experimental tests carried out to verify the response of the new monitor both to low and high energy neutrons are reported. A comparison with the response function of three conventional commercial rem counters is presented.

An evaluation is presented of the production of 13N, 15O, 16N, 37S, 40Cl and 41Ar by activation of air using neutrons generated by a 40 MeV cyclotron, now being installed in a hospital in Milan. The amount of radioactivity released into the external environment depends on the duration of each run and on the number of air changes per hour in the room. Calculations are performed for three different ventilation rates, for the cyclotron vault and one typical target room. The delivery of the activity into the external atmosphere will occur through a chimney. An assessment of the annual dose to individuals living in the vicinity, based on a simple atmospheric dispersion model, shows that no significant radiological risk to the population will be produced and, because several cautious assumptions were made, the values should be regarded as upper limits.

The response of the dosemeters in three different high energy stray radiation fields at CERN has been investigated. Compared to similar experiments performed in the past, new types of instruments were employed, and spectral information on the neutron field was acquired. The results are discussed in the light of previous experience and present knowledge with respect to the composition of the stray fields.

An assessment has been made of the production of radioactive gases by neutron activation of air in the cyclotron vault and target rooms at the MRC Cyclotron Unit at Hammersmith Hospital, London. The environmental dose to the individuals due to the release of the radioactive gases at several distances from the source was estimated and shown to be negligible in comparison with recommended limits.

In recent radiotherapy techniques, such as boron neutron capture therapy (BNCT) and proton therapy, the high non-uniformity of the spatial distribution of absorbed dose makes mandatory 3-D dose determinations in order to carry out good treatment planning. The investigated dosimetric technique is based on a chemical dosemeter (ferrous sulphate solution) incorporated in a gel (agarose). Ionising radiation causes a variation in certain parameters of the system such as the relaxation rates of hydrogen nuclei, measurable by nuclear magnetic resonance imaging (NMR) or the gel optical absorption in the visible spectum, measurable by spectrophotometry. Gel containing 10B in the amount typically accumulated in tumours for BNCT was analysed. The isodose curves were obtained from NMR analysis of a phantom of borated gel after irradiation in the thermal column of a nuclear reactor. The results show that the gel is a promising dosimetric system. A method for depth-dose profiling in tissue irradiated by a proton beam is also suggested. In the profile the Bragg peak position has been determined within 0.1 mm and the widening in the peak ramp proves to be about 1 mm.