Jasna L. Ristic-Djurovic

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.

Influence of Cyclotron Magnet Gap Size on Stripping Extraction

The stripping extraction system of a cyclotron is prized by the range and quality of beams it delivers. The gap size of a cyclotron magnet is one of the parameters which significantly influence the design as well as the output characteristics of the stripping extraction system. The vertical dimension of the beam as well as of the extraction system elements placed inside a vacuum chamber is limited by the magnet gap size. Beside this direct influence, the indirect effect of the magnet gap size on stripping extraction occurs through the magnetic field and its impact on the beam dynamics in the extraction region. The performance of the extraction system is optimized by the proper placement of the point of beam exit from the cyclotron. It is shown that the optimal position of the exit point strongly depends on the magnet gap size. The performance of the optimized stripping extraction system for a smaller gap size is found to be somewhat better.

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.

Role and Significance of Uniform Distribution in a Study of Ensemble of Particles

Dynamics of an ensemble of particles is often studied by tracking a large number of test particles from a chosen initial state to an adequately defined final state. Random distributions of particles over considered parameters are frequently used to describe an initial state of studied ensemble. Randomness of input data insures that there is no overlapping in test particles visualization; however, it hides the dependencies between various input and output parameters. If non-random, uniformly distributed input data is used, relationships between the input and output variables are revealed. Further, mapping of such an input into its output together with an appropriate interpolation scheme contains description of an output corresponding to any desired distribution of input data. A mapping of non-random uniformly distributed input into its output is combined with n -dimensional linear interpolation into a method for studying dynamics of an ensemble of particles. Advantages and efficiency of the method are illustrated using an ion beam interaction with two devices: the four parallel, equally spaced finite wires and the spiral inflector. The method is applicable if interactions between particles within an ensemble are negligible compared to other forces involved.

Analytical Prediction of Ion Stripping Extraction From Isochronous Cyclotrons

Accelerated ion beams are often extracted from a cyclotron by stripping some of ions electrons at the end of the acceleration process. Stripping extraction system is commonly designed and optimized using computer simulations of beam dynamics at a later stage of a cyclotron project. However, minor changes in the distance between the magnet poles are proven to cause large displacements of the optimal position of high-energy transport line. It is shown that simple analytical formulas give good prediction of the position and direction of beam exit after stripping extraction and are useful tool for preliminary facility layout planning.