Boron Neutron Capture Therapy Taskaev, S. Yu
Physics of atomic nuclei,
03/2021, Letnik:
84, Številka:
2
Journal Article
Recenzirano
Fundamentals of boron neutron capture therapy of malignant tumors are outlined, and the current status of the development of epithermal-neutron sources on the basis of charged-particle accelerators ...is surveyed. Attention is additionally given to a neutron source based on a charged-particle accelerator belonging to a new type—a tandem accelerator with vacuum insulation and a lithium neutron-producing target.
There is a pressing need for improving of the high-frequency magneto-impedance effect of cost-effective soft magnetic materials for use in high-performance sensing devices. The impact of the ...stress-annealing on magnetic properties and high frequency impedance of Fe-rich glass-coated microwires was studied. Hysteresis loops of Fe-rich microwires have been considerably affected by stress- annealing. In stress-annealed Fe- rich microwire we obtained drastic decreasing of coercivity and change of character of hysteresis loop from rectangular to linear. By controlling stress-annealing conditions (temperature and time) we achieved drastic increasing (by order of magnitude) of giant magnetoimpedance ratio. Coercivity, remanent magnetization, diagonal and of-diagonal magnetoimpedance effect of Fe-rich microwires can be tuned by stress-annealing conditions: annealing temperature and time. Observed experimental results are discussed considering relaxation of internal stresses, compressive "back-stresses" arising after stress annealing and topological short range ordering.
Low-entropy (un-substituted Ba-hexaferrite) and High-entropy (polysubstituted Ba-hexaferrite with Ga/In/Ti/Cr/Co ions) samples were synthesized. The crystal structure, microstructure, magnetic and ...electrical properties of BaFe12O19 and Ba(Fe6.00Ga1.26In1.17Ti1.20Cr1.22Co1.15)O19 ceramic samples were investigated. It was established that there is a correlation between entropy state and the features of crystal structure. Magnetic properties are critically depended on entropy state and intensity of super exchange interactions. Magnetic phase separation was observed (coexistence of the classical multi domain states and magnetic “nano regions”) in HE-samples. In hexaferrites, a strong coupling between entropy state, magnetic and electrical properties was demonstrated.
We present an overview of the factors as well as post processing tools allowing optimization of magnetic softness and GMI effect of rapidly quenched materials: microwires and ribbons. Generally, low ...coercivity and high GMI effect have been observed in as-prepared Co-rich compositions. Annealing at adequate conditions can be very effective for manipulation of the magnetic properties and GMI effect of amorphous and nanocrystalline rapidly quenched materials. After annealing of Co-rich compositions, we can observe transformation of inclined hysteresis loops to rectangular. However, at certain annealing conditions GMI effect can be improved. Using stress-annealing, GMI effect of both Fe-rich and Co-rich microwires as well as of amorphous ribbons can be improved. On the other hand, in Fe-rich FeCuNbSiB microwires after appropriate annealing we observed considerable magnetic softening and GMI effect enhancement. The other promising post-processing allowing GMI effect optimization is Joule heating.
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•Trends in optimization of GMI effect in amorphous and nanocrystalline materials.•Magnetic softening of Fe-rich microwires after stress-annealing or nanocrystallization.•Improvement of GMI effect after Joule heating of Co-rich microwires.•Optimization of GMI effect after post-processing of Co-rich amorphous ribbons.•Improvement of GMI effect after annealing and stress-annealing of Co-rich microwires.
A tandem accelerator with vacuum insulation has been proposed and developed in the Budker Institute of Nuclear Physics. Negative hydrogen ions are accelerated by the positive 1MV potential of the ...high voltage electrode, converted into protons in the gas stripping target inside the electrode, and then the protons are accelerated again by the same potential. The potential for high voltage and intermediate electrodes is supplied by the sectioned rectifier through a sectioned bushing insulator with a resistive divider. In this work, we propose a radical improvement of the accelerator concept. It is proposed to abandon the separate placement of the accelerator and the power supply and connect them through the bushing insulator. The source of high voltage is proposed to be located inside the accelerator insulator with high voltage and intermediate electrodes mounted on it. This will reduce the facility height from 7m to 3m and make it really compact and attractive for placing in a clinic. This will significantly increase the stability of the accelerator because the potential for intermediate electrodes can be fed directly from the relevant sections of the rectifier.
•It is proposed to abandon separate placement of accelerator and power supply.•The source of high voltage is proposed to be located inside accelerator insulator.•This will reduce the facility height and make it compact for clinic.
We observed a remarkable improvement of domain wall (DW) mobility, DW velocity, giant magnetoimpedance (GMI) effect and magnetic softening at appropriate stress-annealing conditions. Beneficial ...effect of stress-annealing on GMI effect and DW dynamics is associated with the induced transverse magnetic anisotropy. An improvement of the circumferential permeability in the nearly surface area of metallic nucleus is evidenced from observed magnetic softening and remarkable GMI effect rising. We assumed that the outer domain shell with transverse magnetic anisotropy associated to stress-annealing induced transverse magnetic anisotropy affects the travelling DW in a similar way as application of transversal bias magnetic field allowing enhancement the DW velocity. Observed decreasing of the half-width of the EMF peak in stress-annealed microwires can be associated to the decreasing of the characteristic DW width. Consequently, stress annealing enabled us to design the magnetic anisotropy distribution beneficial for optimization of either GMI effect or DW dynamics.
Hexagonal ferrites with a magnetoplumbite structure (M-type hexaferrites or M-HF) and multiple substitution of Fe3+ ions with Ti4+, Al3+, Mn3+, Co2+, In3+, Ga3+, Cr3+ have a varying nominal chemical ...composition Ba,Sr,Ca,La{Fex(TiAlMnCoInGaCr)12-x}O19 (1.5≤х≤9) or (BSCL{Fex(TAMCIGC)12-x}O19). Ceramics samples were synthesized by solid-state reactions. Three batches of BSCL{Fex(TAMCIGC)12-x}O19 hexaferrites were produced at temperatures of 1300 °C, 1350 °C and 1400 °C. The correlation of chemical composition, phase content, structural and magnetic properties was investigated depending on the Fe content by EDX, XRD, SEM and PPMS. Samples synthesized at 1300 °C were non-single-phase. Samples BSCL{Fex(TAMCIGC)12-x}O19 with 4.5≤х≤9, synthesized at 1300 °C and 1400 °C, were single-phase and can be described by the magnetoplumbite structure. The entropy state (ΔSconf) was calculated as a function of the Fe content. It was confirmed that single-phase multiple substituted M-HF with high ΔSconf can be obtained with Ti4+, Al3+, Mn3+, Co2+, In3+, Ga3+, Cr3+ substituents even if ΔSconf is noticeably less than 1.5R.
This paper describes a method for automating the facility and a method for online data processing that allows an operator and analytical physicists to quickly process information during an experiment ...without the need for the manual postprocessing of data. The architecture of the automation system was proposed and software was developed for (1) an analysis of signals at the installation with the ability to filter according to user-defined conditions and the ability to display on real-time graphs and (2) displaying the values of various diagnostics with general real-time availability.
A neutron source based on a tandem accelerator with vacuum insulation and a lithium target has been created at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. ...This report provides an overview of the diagnostic tools used at the facility, such as determining the position and size of a beam of negative hydrogen ions using a wire scanner and video cameras, automating experiments on measuring the phase portrait of a proton beam with energies up to 2 MeV using a wire scanner, determining the position and the size of the proton beam on the surface of the lithium target using built-in thermocouples in real time, and automating measurements of the spatial distribution of the absorbed dose components in the water phantom.
The paper presents a review of the current state of development of accelerator-based epithermal neutron sources for boron neutron capture therapy (BNCT), a promising method for the treatment of ...malignant tumors. Special attention is paid to an epithermal neutron source based on a new type of accelerator of charged particles: a tandem accelerator with vacuum insulation and a lithium neutron-producing target.
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