Beam stripping extraction from the VINCY cyclotron

The extraction system of a cyclotron guides an ion beam from a spiral acceleration orbit, through an extraction trajectory, into a high energy transport line. The two methods commonly used to direct an ion into the extraction path are deflection, by the electric field of an electrostatic deflector, and ion stripping, by a thin carbon foil. Compared to the electrostatic deflector system, the stripping extraction provides a fast and easy change of the extracted ion energy and is easier to manufacture operate, and maintain. However, the extraction trajectory and dynamics of an ion beam after stripping are highly dependant on the ion energy and specific charge. Thus, when a multipurpose machine such as the VINCY Cyclotron is concerned, it is far from easy to deliver a variety of ion beams into the same high energy transport line and at the same time preserve a reasonable compactness of the extraction system. The front side stripping extraction system of the VINCY Cyclotron provides high (~70 MeV) and mid (~30 MeV) energy protons, as well as a number of heavy ions in broad energy ranges. The back side stripping extraction system extracts low energy protons (~18 MeV) and enables their simultaneous use with high energy protons at the front side of the machine

The effect of structural changes during sintering on the electric and magnetic traits of the Ni96.7Mo3.3 alloy nanostructured powder

Ni96.7Mo3.3 powder was electrochemically obtained. An X-ray diffraction analysis determined that the powder consisted of a 20% amorphous and 80% crystalline phase. The crystalline phase consisted of a nanocrystalline solid nickel and molybdenum solution with a face-centred cubic (FCC) lattice with a high density of chaotically distributed dislocations and high microstrain value. The scanning electronic microscopy (SEM) showed that two particle structures were formed: larger cauliflower-like particles and smaller dendriteshaped ones. The thermal stability of the alloy was examined by differential scanning calorimetry (DSC) and by measuring the temperature dependence of the electrical resistivity and magnetic permeability. Structural powder relaxation was carried out in the temperature range of 450 K to 560 K causing considerable changes in the electrical resistivity and magnetic permeability. Upon structural relaxation, the magnetic permeability of the cooled alloy was about 80% higher than the magnetic permeability of the fresh powder. The crystallisation of the amorphous portion of the powder and crystalline grain increase occurred in the 630 K to 900 K temperature interval. Upon crystallisation of the amorphous phase and crystalline grain increase, the powder had about 50% lower magnetic permeability than the fresh powder and 3.6 times lower permeability than the powder where only structural relaxation took place

Preliminary results of ion trajectory tracking in the acceleration region of the VINCY cyclotron

In an accelerating region of a cyclotron, an ion makes a large number of turns; thus, its n the Runge-Kutta method of the fourth order with the adaptive time step has been developed. The accuracy requirement is simultaneously set on position and momentum calculation. Magnetic fields used as inputs, have been evaluated in terms of the radial fluctuations of the orbital frequency, i.e. their isochronisms. Ion trajectory tracking has been performed for the following four test beams: H-, H+3, 4He+, He+, and 40Ar6+

Thermal relaxation of magnetic clusters in amorphous Hf_{57}Fe_{43} alloy

The magnetization processes in binary magnetic/nonmagnetic amorphous alloy Hf_{57}Fe_{43} are investigated by the detailed measurements of magnetic hysteresis loops, temperature dependence of magnetization, relaxation of magnetization and magnetic ac susceptibility, including a nonlinear term. Blocking of magnetic moments at lower temperatures is accompanied with the slow relaxation of magnetization and magnetic hysteresis loops. All of the observed properties are explained with the superparamagnetic behaviour of the single domain magnetic clusters inside the nonmagnetic host, their blocking by the anisotropy barriers and thermal fluctuation over the barriers accompanied by relaxation of magnetization. From magnetic viscosity analysis based on thermal relaxation over the anisotropy barriers it is found out that magnetic clusters occupy the characteristic volume from 25 up to 200 nm3 . The validity of the superparamagnetic model of Hf_{57}Fe_{43} is based on the concentration of iron in the Hf_{100-x}Fe_{43} system that is just below the threshold for the long range magnetic ordering. This work throws more light on magnetic behaviour of other amorphous alloys, too

Stripping extraction of positive ions from a cyclotron

In a multipurpose cyclotron, it is convenient to use stripping extraction to extract selected positive ions in addition to the usual extraction by stripping of negative ions. The ions are specified as positive or negative according to the sign of their charge during acceleration. After stripping, positive ions travel not only through the pole edge magnetic field gradient, as is the case with negative ions, but can also pass more than once through regions of large sector edge magnetic field gradients. Influence of the magnetic field gradients on the trajectory of a stripped positive ion and on the extracted beam emittance is studied. It is shown that extraction efficiency depends on the position of the point of beam extraction from a cyclotron and on the ratio between ion charge after and before stripping. The position of the point of extraction also strongly affects the design parameters of the stripping extraction system. Extraction quality and design parameters cannot all be simultaneously optimized. The method of extraction system optimization is suggested and applied to the special case of the VINCY cyclotron

Unidirectional stripping extraction from a cyclotron which accelerates light as well as heavy ions

The VINCY Cyclotron (VINca CYclotron) is a multipurpose machine intended to accelerate light as well as heavy ions. To extract heavy ions with low energy and light ions an extraction system with stripping foil is used. Heavy ions with high energy will be extracted by means of an electrostatic deflector. The former extraction system will be manufactured and used first. The proposed unidirectional stripping extraction system is the optimal balance between the placement of the extraction line and the required diversity and quality of the extracted beam. The available range of extraction directions is set by geometry limitations

Precipitation of radiation belt electrons by magnetospherically reflected whistlers

We use a test particle simulation model based on gyro-averaged equations of motion to study the influence of oblique magnetospherically reflected (MR) whistlers on the near-loss-cone distribution function of radiation belt electrons. We find that MR whistlers originating in lightning can resonantly interact with radiation belt electrons over a broad range of L shells and precipitate higher energy electrons from lower L Shells. Electrons in the energy-range of 1 to 2.6 MeV are precipitated from L = 2, whereas from L = 4 the precipitated electron energy range is 150-220 keV. The precipitated differential electron flux, due to this interaction, is higher for higher L shells, and the maximum value ranges from Phi E-prec(1.11 MeV) 5.2 x 10(-4) electrons cm(-2) s(-1) keV(-1) at L = 2 to Phi E-prec(173 keV) = 4.6 x 10(-1) electrons cm(-2) s(-1) keV(-1) at L = 4. The lifetimes of radiation belt electrons in a given magnetic flux tube around the L shell on which the interaction takes place are found to be of the order of several days, comparable to lifetimes corresponding to electron loss induced by hiss, which was heretofore assumed to be the dominant loss mechanism [Lyons et al., 1972]. The minimum electron lifetimes vary from 2.4 days for 1.11 MeV electrons at L = 2 to 4.6 days for 173 keV electrons at L = 4

Air Quality Indication in Blace (Southeastern Serbia) Using Lichens as Bioindicators

Air quality investigations have not been undertaken in Blace until now. Identifying the presence of different types of epiphytic lichens was performed in the summer 2012 in Blace (southeastern Serbia), and selected rural settlements around Blace, in order to establish the air quality of the area. The analysis of samples from described localities indicated the presence of 25 lichen taxa from 19 genera. Using the Index of Atmospheric Purity (IAP), it was found that there are 2 different air pollution zones in Blace: "lichen desert" and "transitional" or "struggle zone", which includes the periphery of the city. In these zones the air is moderately polluted. In the urban area of Blace there is no "normal" zone, but one was detected in the surrounding rural areas

Strawberry Polyphenols Attenuate Ethanol-Induced Gastric Lesions in Rats by Activation of Antioxidant Enzymes and Attenuation of MDA Increase

BACKGROUND AND AIM: Free radicals are implicated in the aetiology of gastrointestinal disorders such as gastric ulcer, colorectal cancer and inflammatory bowel disease. Strawberries are common and important fruit due to their high content of essential nutrient and beneficial phytochemicals which seem to have relevant biological activity on human health. In the present study we investigated the antioxidant and protective effects of three strawberry extracts against ethanol-induced gastric mucosa damage in an experimental in vivo model and to test whether strawberry extracts affect antioxidant enzyme activities in gastric mucosa. METHODS/PRINCIPAL FINDINGS: Strawberry extracts were obtained from Adria, Sveva and Alba cultivars. Total antioxidant capacity and radical scavenging capacity were performed by TEAC, ORAC and electron paramagnetic resonance assays. Identification and quantification of anthocyanins was carried out by HPLC-DAD-MS analyses. Different groups of animals received 40 mg/day/kg body weight of strawberry crude extracts for 10 days. Gastric damage was induced by ethanol. The ulcer index was calculated together with the determination of catalase and SOD activities and MDA contents. Strawberry extracts are rich in anthocyanins and present important antioxidant capacity. Ethanol caused severe gastric damage and strawberry consumption protected against its deleterious role. Antioxidant enzyme activities increased significantly after strawberry extract intake and a concomitantly decrease in gastric lipid peroxidation was found. A significant correlation between total anthocyanin content and percent of inhibition of ulcer index was also found. CONCLUSIONS: Strawberry extracts prevented exogenous ethanol-induced damage to rats' gastric mucosa. These effects seem to be associated with the antioxidant activity and phenolic content in the extract as well as with the capacity of promoting the action of antioxidant enzymes. A diet rich in strawberries might exert a beneficial effect in the prevention of gastric diseases related to generation of reactive oxygen species

Phase Formation at the Sintering of Sa, Zn, Ti Oxides

Complex compounds with oxide phases of Ba, 2n, and 11 are widely used in instrument engineering. It is also important to find such production routes for ceramics, which provide their stable structure and properties. Phase formation was investigated for titan, zirconium and barium oxides mixtures during their sintering, after pretreatment by milling of oxides mixtures with high power planetary-type mill. It was shown that active interaction of transferred oxides is observed after milling in the planetary mill. In addition to the presence of initial oxides, formation of complex compounds (barium and zinc titanates – Ba4Ti12O27 BaTiO3, ZnTiO3) was visible after 10 and 20 minutes of milling. The phase composition did not practically change after milling for 40 and 80 minutes. Furthermore, all reflection lines were strongly broadened and overlapped. Sintering of these mixtures after milling was conducted at temperatures 900, 1000 and 1100 °C for 2 hours on air with heating rate of 10 C/min. The complex oxide phase, close to BaZn2Ti4O11 composition, was found as a result of sintering of powders mixture at 900 °C, powder mixture was pretreated for 5 minutes at planetary mill. In addition, phases of ZnTiO3 and BaTiO3 were present. These phases were preserved for long-continued milling, but main components' ratio changed. The formation of BaZn2Ti4O11 phase with changes of interplanar spacings was investigated with variation of time of milling and sintering at temperatures of 1000 and 1100 °C. The Zn2TiO4 cubic phase was also present, its amount decreases only after 80 minutes of high power milling and sintering at 1100 °C. Results of our work showed, that for the system of three oxides active interaction was observed already on the high power milling stage. Sintering at the temperatures of 1000 and 1100 °C resulted in formation ofBaZn1Ti40 l1 oxide phase with composition variation in its homogeneity region