MSA15 attenuators are designed for in-line beam power control. All MSA models contain two ZnSe Brewster
plates in a ‘Vee’ configuration to eliminate lateral beam deviation, and to allow internal dumping of unwanted
Model MSA15-200 uses a stepper motor to drive the rotation action of the plates, with 200 step resolution over
the range from full power to minimum power transmission (0 to 90° rotation).
Standard (uncoated) or enhanced Brewster plates are available.
The complete MSA15 consists of two separate units connected by electrical cable:
(1) the optical head and motor, and
(2) the electronics drive/control unit.
Technical specifications, optical / mechanical
Dimensions : See Figure 79.301.
Construction : Aluminium alloy, black / dove grey finish; ZnSe optics.
Clear aperture : 18.0 mm diameter.
Beam deviation : <0.2mm laterally.
<2 arcminutes angular.
Cooling : Air cooled.
Fittings, (2 off) : Free-rotating coupling rings, with 52.0mm dia. x1.5mm pitch threads
Max CW power : 250W CW.
Polarization : Input must be linearly polarized.
Operation speed : 500msec from maximum to minimum power.
Transmission : 6% – 100% of P-pol. (std version).
0.1%- 99% of P-pol. (enhanced).
Brewster plates (2 off) : Type ZBW5018 (standard).
Type EZBW5018 (enhanced).
Rotation angle resolution : 27 arc minutes.
Range : 12.15° to 102.6° in 256 steps, 0° to 90° in 200 steps
Step accuracy : 3 arc minutes
Technical specifications, electronic
Power supply : Mains, 230V AC or 115V AC (Determined at manufacture)
Electronics package size : 250x200x127 mm (10″x8″x5″).
Control : PIC16C55
Display : LED display of plate orientation over the range 0 to 90°.
Setting : User-set plate orientation over the range 0 to 90° via hexadecimal
thumbwheel switches, and port.
Control option : Toggle switch controls whether position input is taken from thumbwheel
switches or port.
The attenuator head with standard, uncoated, Brewster plates plus electronics drive unit is model MSA15-200.
The attenuator head with enhanced Brewster plates, plus electronics drive unit, is model MSA15-200E.
Alternatively, either can be shipped without the drive unit, but only a driver board for the stepping motor and
data sheets on its use. This option is for the user who wishes to build their own control box (parts MSA15-200X
Operational notes / associated equipment
The recommended power limit (250W CW) is set by the limit on dumped power into the air-cooled internal
beam dump chamber. The Brewster plates, whether standard or enhanced type, are capable of handling
considerably higher powers. MSA15 connects directly to OPG optical piping.
See also ‘Operational Notes’, data section 79.00