THE FIRST BEAM RECIRCULATION AND BEAM TUNING IN THE COMPACT ERL AT KEK

To demonstrate overall technologies for the energyrecovery-linac(ERL)-based light source, we constructed the Compact ERL (cERL) during 2009-2013. In March, 2014, we succeeded in recirculating the CW beams of 6.5 ΠA in the cERL; the beams were successfully transported from the gun to the beam dump under energy recovery operation in the main linac. We report our experience on commissioning the cERL, as well as the results of initial measurements of beam properties.