= Beam shutter =

== Shutter for the input beam ==

 * We tried to install a medium-speed shutter in 2017 to shut the input beam after the IMMTs so that installation work after the PRM can be done without wearing safety glasses.
 * However, the shutter did not work somehow and the anticipation failed.

== Shutter for the output mode-cleaner ==

 * We planned to reuse the shutter to shut the beam before the OMC so that the OMC can be protected until the main interferometer is robustly operated in the dark fringe.
 * We planned to use the same shutter we purchased for the input beam in 2017.

== Shutter spec ==

 * The shutter is a product by Uniblitz. The product name is CS65E1ZM0-ECE. The blade is made of BeCu and coated by AlMgF2. The damage threshold for 1064nm CW is 2.5W/mm2.
 * If the shutter is used after the IMMT2, the beam radius is 4mm and the max tolerable power will be 125W.
 * If the shutter is used before the OMC, the beam radius is 0.45mm and the max tolerable power will be 1.5W.

 * The total opening time is 54msec. The shutter speed is higher than this if the beam is placed near the center of the shutter.
 * The shutter is vacuum compatible: 1e-8 torr.

 * The shutter driver is VED24.