The fast shutter in BL40XU consists of a rotating disk with slits and a galvanometer shutter. The disk has slits so that x-rays can pass only when the disk is in a certain range of rotation. The galvanometer shutter selects one pulse of x-rays. There are two disks with different diameters which are rotated by motors of different rotation. By choosing the motor, the rotation speed of the motor, and the slit, a duty ratio can be chosen. The fastest one is the one shown below: it has a duty ratio of about 0.3% with a rotation of 16000 rpm. Calculated effective opening of the shutter is 10 micro seconds.

This was measured by using a PIN diode. The opening looks longer than 10 miro seconds because of the slow response of the diode. More experiments were made later with better electronics, which showed about 8 micro seconds open time.

A rotating chopper from Julich Institute in Germany is also available at BL40XU. It can be operated in synchronization with the RF signal from the storage ring, making a single-bunch experiment possible.