Saša Ćirković

Hematological parameters' changes in mice subchronically exposed to static magnetic fields of different orientations.

Static magnetic fields (SMFs) are time independent fields whose intensity can be spatially dependent. This study investigates influence of subchronic continuous exposure to upward and downward directed SMF on hematological parameters and spleen cellularity in mice. The experiment is performed on the Northern hemisphere; consequently, the vertical component of geomagnetic field is directed downward. Male, Swiss-Webster, 6 weeks old mice were exposed to the vertically declining SMF. Mice were divided in three groups and continuously exposed or not exposed for 28 days to the SMF characterized by the averaged field of 16 mT and averaged field gradient of 10 mT/cm. Differently oriented SMF did not alter hemoglobin and hematocrit content among the groups. However, the groups exposed to the upward and downward fields had statistically significant higher levels of serum transferrin compared to the control. Moreover, spleen cellularity in animals in the downward group was significantly higher compared to the upward and control group. In addition, spleen lymphocytes in both of the exposed groups were significantly higher than in the control group. In contrast, spleen granulocytes in the exposed groups were significantly lower than in the control group. Significant decrease was also observed in brain and liver iron content with concomitant increase of iron in serum and spleen in exposed animals. Subchronic continuous exposure to 16 mT SMF caused lymphocyte and granulocyte redistribution between spleen and blood. This distribution is typical for stress induced hematological changes. These results suggest that observed changes were not due to an unspecific stress response, but that they were rather caused by specific adaptation to subchronic SMF exposure.

Method for Fine Magnet Shaping in Cyclotrons

The fine shaping of a cyclotron magnet is usually conducted through an iterative procedure by matching the obtained and the required pre-calculated magnetic field. The quality of the obtained magnetic field is then evaluated by the closeness of the resulting ion gyration frequency to its required value. The method we propose is based directly on the gyration frequency adjustment; therefore, the pre-calculated magnetic field criterion and the empirical weight factors often needed for the corresponding shape estimate are avoided. The method is applicable to the angular width as well as the thickness of the magnet elements used in fine shaping.

Comparative Analysis of Methods for Isochronous Magnetic-Field Calculation

Accurate magnetic fields are needed for defining the operation of a multipurpose cyclotron as well as for designing other parts of the machine, as an input parameter. The quality of an isochronous magnetic field is evaluated by the closeness of the obtained ion gyration frequency to its required value. The commonly used method of isochronous field calculation for sector focused cyclotrons was Gordons procedure. The incorporation of the gyration frequency criterion in isochronous field calculation has grown with the increase of the computer speed. We suggest a highly accurate method for the isochronous magnetic field calculation based on the gyration frequency adjustment.

Subchronic exposure to static magnetic field differently affects zinc and copper content in murine organs

Abstract Purpose Static magnetic fields (SMF) have been widely used in research, medicine and industry. Since zinc and copper play an important role in biological systems, we studied the effects of the subchronic continuous SMF exposure on their distribution in murine tissues. Materials and methods For 30 days, mice were exposed to inhomogeneous, vertical, downward or upward oriented SMF of 1 mT averaged intensity with spatial gradient in vertical direction. Results SMF decreased the amount of copper and zinc in liver. In brain, zinc levels were increased and copper levels were decreased. In spleen, zinc content was reduced, while copper amount remained unchanged. Conclusions Subchronic exposure to SMF differently affected copper and zinc content in examined organs, and the changes were more pronounced for the downward oriented field. The outcome could be attributed to the protective, rather than the harmful effect of SMF.

Optimal Acceleration in Isochronous Straight Sector Cyclotrons

During the design of a cyclotron the time and attention dedicated to the injection and extraction of a beam usually overcome those devoted to the acceleration. However, the efficiency of the accelerating process largely contributes to the overall efficiency of the machine because the beam spends the most time in the accelerating region. A thorough and systematic study of the influence of beam parameters on the overall quality of acceleration is performed. The conditions for the optimal acceleration are determined and the method for defining the complete continuous sets of input parameters providing such acceleration is proposed.

Analytical Description of Two-Dimensional Magnetic Arrays Suitable for Biomedical Applications

Two-dimensional magnetic arrays are used to generate a magnetic field that pervades a layer of volume above the arrays surface, often creating regions of high magnetic flux density gradients. We have recently employed an array with equally oriented magnetic moments of individual elements in several biomedical experiments. We have chosen this type of array because of the slowly decreasing magnetic field it produces, which extends far from the arrays surface and permeates the experimental volume. In order to fully define experimental conditions related to the applied magnetic field, we derive exact closed-form expressions for the magnetic flux density. Based on these analytical expressions and exploiting the array periodicity, a method is proposed for the approximate assessment of the main magnetic field parameters of interest-mean magnetic flux density and mean gradient of its component perpendicular to the arrays surface. The obtained approximate assessment can further serve as a tool for the design of arrays with the desired mean field parameters. All the results are verified and validated by comparison with the finite element modeling as well as measurements.

Ion Beam Acceleration With Radio Frequency Powered Rainbow Lens

The electrostatic quadrupole lens, quadrupole accelerator and square rainbow lens as well as radio frequency quadrupole accelerator all have similar structure with four rod-like electrodes. Unlike the last one, which is powered by the alternating voltage, the first three are electrostatic devices. Each two adjacent electrodes of a common electrostatic lens have equal magnitude and opposite signs of their electric potentials, whereas, electric potentials of rainbow lenss electrodes are all equal in magnitude as well as in sign. If powered by the appropriate radio frequency instead of a DC voltage, the rainbow lens transforms into an ion beam accelerator which could cost-effectively broaden the available energy range of low energy ion beam facilities.

Magnet with Uncoupled Combined Functions

Efficient extraction by ion stripping of a number of ion beams from a multipurpose cyclotron through the same transport line could be achieved with a combined function magnet. Characteristics of a combined magnet used for this purpose are significantly different from those of commonly used combined function magnets. For example, bending and focusing functions must be independently adjustable, beam paths are not centered to the devices axis, only one device is needed per cyclotron, and requirements regarding maximal achievable quadrupole and dipole fields as well as field linearity are not as demanding as for combined function magnets used for other applications. Using two analytical models as well as a simple numerical model, it is shown that two independently powered slanted dipoles, off-centered and arranged symmetrically with respect to the beam area, could efficiently serve as a combined function magnet in the stripping extraction system of a multipurpose cyclotron.

Optimization of Equally Charged Quadrupole Parameters

A quadrupole with equally charged electrodes could be used to focus as well as to accelerate ion beams. The equality of electrode charges causes the driving electric field of this device to be qualitatively different from that of other devices with a similar structure composed of four rod-like electrodes. For the same reason, the area of strong field influence on the beam is shifted towards the entrance and exit of the device. Consequently, it is expected that the devices performance depends on the shapes of its entrance and exit regions. The device parameters whose influence is studied are aperture radius, gap size, and rod length. Performance of the device is quantified with accelerating and focusing potentials, which are obtained as integrals of axial and radial electric fields. These variables are further used to choose optimal values of the device parameters for desired operation of the device.

Enhancement of Ion Beam Acceleration Efficiency in Isochronous Cyclotrons

A novel method for efficient analysis of ion beam acceleration in an isochronous cyclotron is proposed. Numerical simulation is used to perform multiple beam dynamics analyses on the conveniently chosen subsets of data; consequently, the total quantity of studied data is significantly reduced. The obtained results provide direct insight into beam behavior and quality of acceleration. Therefore, the analysis is not only efficient, but detailed and systematic as well. It is used to assess the impact of the accelerated orbit optimization to the enhancement of acceleration efficiency when study is extended from a single test ion to the complete ion beam consideration.