Two-dimensional patterns for optical alignment.
Two-dimensional patterns that have properties suited for optical alignment have been constructed from one-dimensional binary Barker codes. Applications include automated alignment of masks with patterns in photolithography.
Characterization and design of bar code systems for accurate alignment.
The main peak in the autocorrelation function of bar codes is here utilized as the signal of accurate alignment. Attention is therefore directed to the problem of how to increase the contrast of the main autocorrelation peak above the remaining part of the correlation signal and to the problem concerned with the upper limit that the contrast may attain. To meet different requirements of accurate alignment, a series of bar codes is designed. They are classified into several categories according to their performance characteristics. The internal relations between these categories are discussed in greater detail.
DESIGN CONSIDERATION TO PPM KLYSTRONS FOR INDUSTRIAL LINAC
Toshiba has been developing the C-band and X-band Periodic Permanent Magnet (PPM) focused klystron in collaboration with KEK and manufactured prototypes for the JLC project. [1] The PPM klystron has an advantage to enhance the total efficiency as a result of eliminating the electric power for the focusing magnet. From experience on the development the PPM focused klystrons for the JLC project, we plan to apply the PPM focused klystron to the medical and industrial linac. The periodic magnet focusing scheme has some technical difficulties such as stop band voltage. To design the PPM klystron for the medical and industrial linac, it is necessary to give heed to electron beam instability; so that the tube parameters of the PPM focused klystrons have some constraints. The size of the accelerator system is substantially reduced if a PPM focused klystron is used. The majority of medical and industrial linacs use frequencies of S-band range. We discuss the availability of the S-band PPM focused klystron in this paper.