Temperature stabilization of a K110 variable energy cyclotron magnet.

For a large-scale cyclotron using normal conducting magnet coils, 10 h or more are required to obtain a highly stable magnetic field because heat transfer from the coils changes the temperature of the magnets gradually. To suppress the heat transfer and stabilize the magnet temperature in the TIARA K110 cyclotron, water-cooled copper plates were inserted between the main coil and the magnetic yoke. The heat generated by the main coil depends on its circulating current, which depends on the accelerated ion beam.

Artery and vein diameter ratio measurement based on improvement of arteries and veins segmentation on retinal images.

Retinal arteriolar narrowing is decided based on the artery and vein diameter ratio (AVR). Previous methods segmented blood vessels and classified arteries and veins by color pixels in the centerlines of blood vessels. AVR was definitively determined through measurement of artery and vein diameters.

Enhancement of beam pulse controllability for a single-pulse formation system of a cyclotron.

The single-pulse formation technique using a beam chopping system consisting of two types of high-voltage beam kickers was improved to enhance the quality and intensity of the single-pulse beam with a pulse interval over 1 μs at the Japan Atomic Energy Agency cyclotron facility. A contamination rate of neighboring beam bunches in the single-pulse beam was reduced to less than 0.1%.

Improved automated optic cup segmentation based on detection of blood vessel bends in retinal fundus images.

Glaucoma is a leading cause of permanent blindness. Retinal imaging is useful for early detection of glaucoma. In order to evaluate the presence of glaucoma, ophthalmologists may determine the cup and disc areas and diagnose glaucoma using a vertical optic cup-to-disc (C/D) ratio and a rim-to-disc (R/D) ratio.

Influence of injection beam emittance on beam transmission efficiency in a cyclotron.

The JAEA AVF cyclotron accelerates various kinds of high-energy ion beams for research in biotechnology and materials science. Beam intensities of an ion species of the order of 10(-9)-10(-6) ampere are often required for various experiments performed sequentially over a day. To provide ion beams with sufficient intensity and stability, an operator has to retune an ion source in a short time.

Automated microaneurysm detection method based on Eigenvalue analysis using Hessian matrix in retinal fundus images.

Diabetic retinopathy (DR) is the most frequent cause of blindness. Microaneurysm (MA) is an early symptom of DR. Therefore, the detection of MA is important for the early detection of DR.

Useful technique for analysis and control of the acceleration beam phase in the azimuthally varying field cyclotron.

We have developed a new technique for analysis and control of the acceleration beam phase in the cyclotron. In this technique, the beam current pattern at a fixed radius r is measured by slightly scanning the acceleration frequency in the cyclotron. The acceleration beam phase is obtained by analyzing symmetry of the current pattern.

Single-turn extraction from a K110 AVF cyclotron by flat-top acceleration.

Single-turn extraction from the Japan Atomic Energy Agency AVF cyclotron with a K number of 110 using a flat-top (FT) acceleration system has been achieved to reduce the energy spread of an ion beam for microbeam formation with energy up to hundreds of MeV and to increase extraction efficiency from the cyclotron. In order to generate a FT waveform voltage using the fifth-harmonic frequency on a dee electrode, a FT resonator was designed using MAFIA code to achieve downsizing and low power consumption. The FT resonator, coupled to the main resonator through a coupling capacitor, covered the full range of the fifth harmonic frequency from 55 to 110 MHz.

Characteristics of focusing high-energy heavy ion microbeam system at the JAEA AVF cyclotron.

Ion optical analysis was made for a new focusing high-energy heavy ion microbeam system connected to the AVF cyclotron (K=110) at the accelerator facility, TIARA of JAEA Takasaki. The focusing performance of the microbeam system was estimated from both the calculation up to third-order term using TRANSPORT code and the measurement of beam resolution with the secondary electron imaging. As a result, a minimum beam size was evaluated at 0.