Shutter head unit C-SU
Description and Use
The shutter head uses a rotary solenoid to flip a Supermax coated Silicon mirror in and out of the beam.
When the shutter is closed, the beam is reflected onto a water-cooled beam dump. When open, the beam
passes straight through the unit. The open position is the electrically activated state of the solenoid.
Therefore, if the power were to fail, the shutter will close (a spring provides the force). LEDs on the shutter
head indicate the status: red for open and green for closed. The open and close positions are detected by
Power is provided via the 9-pin D plug connector and open/close status can also be monitored via this
connector. An optional Laser Shutter Controller, LSC01, supplies power and monitors the status of the
Note that the shutter is intended as a safety shutter and not for brief timing exposures. Using the LSC01,
typical opening and closing times have been measured at 30 and 60 msec respectively (as defined by the
period in which neither limit switch ‘sees’ the mirror). Note that these times cannot be equalised due to the
solenoid limitations. The clear aperture is 19mm.
The beam dump is water cooled via the connectors (6/4 M6). For a water temperature rise of ΔT °C and a
laser power P Watts, the water flow rate should be 0.014P/ΔT litres/min. e.g. for a 10° rise in water
temperature and 500W, the flow is 0.7 litres/min.
The shutter heads are provided with retractable screw rings for mounting to beam pipe. Before installing the
shutter, check that the beam is centred to the beam pipe. Also note that there is an input and output side.
Sending the beam in from the wrong side will cause it to hit the rear of the mirror mount.
The shutter will operate in any orientation.
For those who wish to provide their own controller, the drawing below shows the internal circuit of the shutter
head. Note that only 5 pins on the connector are actually used.
Any controller must supply +12V to pin 1 and be able to provide up to 1A. To open the shutter, pin 3 is taken
to 0V. This can be done via a simple switch or using a transistor.
The reflective opto-switches OPB704 detect the presence of the mirror. When the internal transistor sees
light from the diode reflected off the mirror, it conducts, pulling the base of the 2N3904 up and causing it to
conduct. The latter acts as a current booster to supply the indicator LED and pass the signal for external use
via pins 7 and 8 (going high to denote detection).
The reverse biased diode 1N4007 suppresses any back emf when the solenoid is deactivated.
Fig 1: Internal circuit of C-SU head