LS-20 Instruction Manual
00629-53-000
Page 11 of 18
Issue 12 19 January 2021
8
SIL-3 Version LS-20-SIL24
To achieve EN13849-1 performance level ‘e’ the ‘SIL3’ version must be used wired as shown in
diagram 2. The ‘SIL3’ version is a twin unit which has one shutter behind another. Both shutters
must be open to allow the beam to pass through.
In this unit one set of monitor contacts is dedicated to one of the shutters, the other contact to the
other shutter, so the state of both blades can be monitored. When correctly interfaced to a
Lasermet ICS, the interlock system cannot be armed if either one or both blades are not detected
closed.
It is theoretically possible to achieve SIL 4 with the SIL3 shutter however the method of control in
this case is outside the scope of this manual.
9
Blade and Beam Dump Options
The LS-20 beam dump is removable which allows an external beam dump to be used. This could
potentially enable the shutter to be used with more powerful lasers than can be dissipated by the
shutter itself. In this instance it is vital that the external beam dump is mounted as close as possible
to the shutter and that the beam path is suitably contained to avoid risk of exposure.
It is also possible to locate a laser power meter in place of the beam dump so that the laser power
can be determined while the shutter is closed. In this arrangement it is essential that the power
meter head damage threshold is sufficient to withstand the laser beam for the length of time for
which the laser may be active with the shutter closed.
If using an external option in place of the integral beam dump, consideration should be given to the
type of blade fitted, see below.
Note that the unit is primarily intended as a safety shutter rather than a precision beam diverter or
timing shutter. Due to the free moving nature of the blade the exact exit angle of the beam through
the beam dump aperture is variable, therefore any external apparatus must be mounted as close as
possible to the shutter, it must have an aperture the same size or bigger than the port and be able to
accept small variations in beam position and angle.
Blade Type
The standard LS-20 has an angled bare stainless-steel blade with a non-precision surface which
deflects and to some extent scatters the beam. This surface is generally suitable for most
applications when the integral beam dump is used. To prevent permanent damage and invalidation
of warranty it is essential that the energy density of the laser is insufficient to ablate the blade.
It is possible to order the LS-20 with other blade materials which may be more appropriate
particularly when the integral beam dump is removed.
The ceramic blade option is recommended for Q-switched lasers where the standard stainless-steel
blade may become ablated.
