YAG screen

The component consists of 

• An electronics junction box of aluminium. Its internal components (a solenoid valve for pneumatics, a clamp of aluminium and a pneumatics cylinder, made of steel and stainless steel) are represented as homogenised material (standard Cable and 50% of void).
• Linear pneumatic feedthrough
• The mirror is made of Quartz, it is located in the mirror holder and can be tilted with respect to the beam axis (in the drawing the tilt is 45°).
• YAG crystal holder. It does not go into the direct beam, but holds the YAG garnet. The crystal thickness is normally very thin, 100 μm, therefore it is not modelled. The crystal holder can also be tilted to normal incidence (5° in the drawing).

There are two configurations, outside- and in-beam, controlled by the InBeam variable. In the in-beam configuration the screen is inserted in the beam, while in the outside- configuration its outside the beam, therefore the thread, the mirror and the screen holder are not built in order to speed up geometry tracking.

The beam axis is specified by the setScreenCentre method as shown e.g. here. If the beam axis is specified, the scren holder and the mirror are built at this axis, otherwise their location is defined by the threadLift variable.

In the singleItem geometry the YAG screen is built as a single component, while normally it is attached to a vacuum component (e.g. ion pump). Its mirror and screen holder as well as part of the feed-through are inserted inside this vacuum component and therefore the cell where these parts are inserted becomes complicated.

The YagScreen class can split and redefine this cell if the cell is removed and the pipeSide and pipeFront variables are set. This simplifies the outer rule of the mirror and screen holder and therefore improve geometry tracking performance. A real life example is shown in lines 163-165.

YAG screen can be either inserted into any component or used together with normal or big type special YAG units.