High resolution beam line for the Grand Raiden spectrometer

Abstract

We have designed and constructed a new beam line which can accomplish both lateral and angular dispersion matching with the Grand Raiden spectrometer. In dispersive mode, lateral and angular dispersions of the beam line are b16=37.1m and b26=−20.0rad, respectively, to satisfy matching conditions for Grand Raiden. In achromatic mode, the beam line satisfies the double achromatic condition of b16=b26=0. The magnifications of the beam line are (Mx,My)=(−0.98,0.89) and (−1.00,−0.99) for dispersive and achromatic modes, respectively. In the commissioning experiments, we have succeeded to separate the first excited 2+ state of 168Er with Ex=79.8keV clearly from the ground state in the (p,p′) reaction. We achieved energy resolutions of ΔE=13.0±0.3 and 16.7±0.3keV in full width at half-maximum for 295 and 392MeV protons, respectively. These energy resolutions agree with the resolving power of Grand Raiden for an object size of about 1mm.