Undulator wake-up

The undulator needs a wake-up: After a break of 187s the feed-back system of the undulator is switched off and a break is enabled (stand-by mode). This counter measure against vibrations has been implemented on request by BL scientists. The undulator still accepts move commands. However, it may take 0.1s (PEX 0.6) until the breaks are disabled and the feed-back it active.

If the linear-encoder position of the undulator drifted during stand-by, the feed-back system corrects this before the gap move begins (init sequence). Therefore a wake-up call that moves the undulator to the start position of a scan is advised. The wake-up call should be a move greater than 4 microns. Otherwise the undulator sees no need to act and does not execute the init sequence.

Normal moves (aka non-scan moves) can be issued without any wake-out calls.

If the current position of the undulator differs by more that 4 micron from the setpoint, the undulator exits the stand-by state and corrects the position. Experience shows that this happens only after a restart of the accelerator.

2019-11-13