Tune measurements of a 1.2 GeV booster electron synchrotron at LNS

A 1.2 GeV booster electron synchrotron (STB ring) with combined use of pulse-beam stretcher at Laboratory of Nuclear Science (LNS), Tohoku University was constructed for study of nuclear physics, which is also supposed to be an injector for a planned future 3rd generation light source. Currently the STB ring is routinely operated with a booster-storage mode to supply high energy γ-rays for nuclear study produced via bremsstrahlung using an internal target wire. Since finite range of a tagging counter array mounted in a bending section, the booster has to be also operated at another flat-top energy lower than 1.2 GeV to extend the γ-ray energy toward lower side. Because characteristics of the STB ring have not been well understood, various beam properties such as betatron tunes and instabilities are not completely controlled at the moment. In order to improve performance of the machine and to study the beam dynamics in a circular accelerator, fundamental properties of the STB ring is now being measured. (author)