Radial distribution chamber (‘UFO’)
The radial distribution chamber is responsible for transferring samples between the different chambers on the endstation. It is interchangably referred to as the ‘UFO’ due to its flying-saucer shape.
It consists of a 2-slot receiver ‘disc’ on the end of a linear transfer arm. The disc can be freely rotated in either direction by pushing it with a wobblestick.
Control of the UFO is currently entirely manual, using the large control wheel on the top of the chamber:
Turning the wheel counter-clockwise (as viewed from above) will always extend the linear arm. Turning it clockwise will first retract the arm, then continuing to turn it once fully retracted will cause the entire transfer arm to rotate clockwise inside the UFO chamber (e.g. to face a different port). It is not possible to rotate the arm counter-clockwise.
If the head of the transfer arm (containing the samples) is misaligned by a few degrees, a mechanical guide will push it into correct alignment when you pass through a port. If you are too misaligned, or trying to drive through a closed gate valve, the head will just run into a wall and stop. This does not risk any damage unless you are moving it very quickly or if you keep trying to apply excessive force to turn the wheel. When the alignment is OK, very little force is required to drive the UFO arm into a chamber.
When you are rotating the UFO arm, there is no tactile feedback to let you know whether you are aligned to a port. You need to do this visually by looking through one of the chamber windows. Typically you will not have good line-of-sight of the UFO head, but you can gauge alignment by looking for the UFO tail to be aligned to an opposite port, as shown below:
Warning
Nothing prevents you from driving the UFO arm too far into a chamber and bashing into a manipulator. While extending the arm, you or a colleague need to be looking carefully into the chamber you are driving into
Warning
Nothing prevents you from driving into a closed gatevalve, nor closing a gatevalve onto the extended UFO arm
Warning
Nothing prevents you from opening a closed gatevalve when the pressure difference is inappropriate (e.g. opening the UFO chamber to a vented loadlock)
Cold transfers
It is possible to dock the UFO head in a special chamber where it can be cooled down with liquid nitrogen. This enables moving from one cold manipulator to another without the sample temperature ever exceeding appproximately 100K. This would primarily be of interest for special sample preparation recipes where the surface is irrecoverably lost if the sample warms up. Speak to the beamline staff if you would like to use this option.