Gynecological brachytherapy with Elekta microSelectron V3 afterloading system

Objective: For commissioning of source path mo-dels for ring tubes of Nucletron (now Elekta) CT/MR ring applicators, a method was established using a source position simulator (SPS) and a CT scanner. Methods: An acrylic glass support for ring tubes was constructed serving as defined coordinate system. With SPS, 40 positions were set in the ring in steps of 2.5mm from proximal to distal direction. In each position a CT-series was taken with ring plane inside scan plane using a GE Optima 580 scanner (slice width 0.625mm). Evaluation was done in multiplanar recon-struction mode under display settings revealing dummy source shape. With a 3D-cursor dwell position coordinate (center of Ir-192 core) was determined. Measurements were validated by film autoradiography in selected positions. Four rings were investigated: 60° Φ26, 45° Φ26, 60° Φ30, and 45° Φ30 with figures denoting angle between ring plane and stem and ring diameter in mm. Results: The method is feasible to reconstruct source dwell positions with an overall accuracy of ±0.3mm. Detected coordinates are consistent and in excel-lent agreement with those obtained by autoradiography. Comparison with Elekta’s source path models, however, re-vealed mean deviations of up to 3.5mm. Discussion: It is advisable to measure individual source paths and have them added to the data base of the treatment planning system.

Comparative investigation of beam quality index Q on flattening filter and flattening filter free 6 and 15 MV photon beams of an medical linear accelerator

An Elekta Synergy LINAC was used to investigate the beam quality index Q and the beam quality correction factor kQ, which is used for absolute dosimetry, in off-axis photon fields. It was found that the beam quality index Q of the photon energies with flattening filter decreases with increasing distance to the central axis, at 6 MV by 4.27% and at 15 MV by 3.98% inside a range of 15 cm off-axis. The beam quality index for flattening filter free photon fields also decreases with increasing distance to the central axis. In this case Q changed only by 1.01% inside the above range.

Seed layer technique for high quality epitaxial manganite films

We introduce an innovative approach to the simultaneous control of growth mode and magnetotransport properties of manganite thin films, based on an easy-to-implement film/substrate interface engineering. The deposition of a manganite seed layer and the optimization of the substrate temperature allows a persistent bi-dimensional epitaxy and robust ferromagnetic properties at the same time. Structural measurements confirm that in such interface-engineered films, the optimal properties are related to improved epitaxy. A new growth scenario is envisaged, compatible with a shift from heteroepitaxy towards pseudo-homoepitaxy. Relevant growth parameters such as formation energy, roughening temperature, strain profile and chemical states are derived.

Inverse spin Hall effect in a complex ferromagnetic oxide heterostructure

We present spin pumping and inverse spin Hall effect (ISHE) in an epitaxial complex oxide heterostructure. Ferromagnetic La0.7Sr0.3MnO3 (LSMO) is used as a source of spin pumping while the spin sink exhibiting the ISHE consists of SrRuO3 (SRO). SRO is a ferromagnetic oxide with metallic conductivity, however, with a Curie temperature (TC) of 155 K, thus well below room temperature. This choice allows to perform the experiment above and below TC of the SRO and to demonstrate that SRO not only shows an ISHE of a magnitude comparable to Pt (though with opposite sign) in its non magnetic state but also exhibits a finite ISHE even 50 K below TC.

Yttrium Iron Garnet Thin Films with Very Low Damping Obtained by Recrystallization of Amorphous Material

We have investigated recrystallization of amorphous Yttrium Iron Garnet (YIG) by annealing in oxygen atmosphere. Our findings show that well below the melting temperature the material transforms into a fully epitaxial layer with exceptional quality, both structural and magnetic. In ferromagnetic resonance (FMR) ultra low damping and extremely narrow linewidth can be observed. For a 56 nm thick layer a damping constant of α = (6.15 ± 1.50) · 10(-5) is found and the linewidth at 9.6 GHz is as small as 1.30 ± 0.05 Oe which are the lowest values for PLD grown thin films reported so far. Even for a 20 nm thick layer a damping constant of α = (7.35 ± 1.40) · 10(-5) is found which is the lowest value for ultrathin films published so far. The FMR linewidth in this case is 3.49 ± 0.10 Oe at 9.6 GHz. Our results not only present a method of depositing thin film YIG of unprecedented quality but also open up new options for the fabrication of thin film complex oxides or even other crystalline materials.

Interface Reactions in LSMO-Metal Hybrid Structures

Perovskites form a class of promising materials for the development of multifunctional devices but require reliable strategies for forming electrical contacts without compromising functionality. We explore the interactions of a range of metal contacts with ferromagnetic oxide La0.7Sr0.3MnO3 (LSMO) and discuss their impact on the magnetic, structural, and chemical properties of the oxide. Although the noble metals gold and silver have negligible impact, metals typically used as adhesion layers, such as titanium and chromium, drive substantial reduction of the oxide, impairing its performance. These effects can be suppressed by inserting a thin barrier layer, such as the conductive oxide SrRuO3.