Toshiya Muto

Conceptual design of an isochronous ring to generate coherent terahertz synchrotron radiation

A novel coherent light source project in the terahertz wavelength region has been developed at Tohoku University. The project may involve development of high brightness electron guns employing cathode of single crystal LaB6 for production of a very short bunch length less than 100 fs. The light source has been designed based on isochronous ring optics to preserve the short bunch length. Although the ring is not a storage ring, the lattice of isochronous optics has resulted from consideration of path length differences due to the betatron motion. The coherent terahertz photons are emitted from circulating electron bunches injected from the linac. Even though the beam is bent by dipole magnets, the bunch shape does not collapse because of the nearly complete isochronous optics of the ring. Since production of the coherent terahertz radiation requires a bunch length less than 100 fs (stdv, if Gaussian), the maximum path length difference created by passing through the dipoles is controlled to not exceed a couple of tens of femtoseconds. The predicted spectrum of the coherent terahertz radiation and its characteristics are also presented.

Upgrade of the 1.2 GeV STB ring for the SR utilization in Tohoku University

An electron accelerator complex, 300 MeV linac and 1.2 GeV booster synchrotron, had been routinely operated as a user facility at Tohoku University until the Great East Japan Earthquake damaged the accelerator seriously. In the last year some budgets were approved to partially reconstruct the accelerator. For the booster ring, some old power supplies of magnets are replaced. Furthermore some quadrupole magnets are also replaced to the combined function magnets of which sextupole component is included. Modifying the ring optics so as to introduce the horizontal dispersion into the position of combined magnet, this replacement will make it possible to correct the chromaticity. There has been no sextupole in the ring, so that the ring current is significantly limited due to head-tail instability. Hence this upgrade will bring the new capability into the ring as a synchrotron light source. Presently it is planned to utilize SR from the 1.3 T bending magnet for educational purpose in the field of SR application such as XAFS. The photon flux of 5.6E12 photons/s/mrad2/0.1%BW will be obtained around the peak energy region of 1 keV for this beam line in the case of 200 mA operation with the emittance of 160 nmrad. In addition to the beam line from bending magnet, a 2 m long straight section is also reserved for an insertion device for future application.