Demonstrate that component alignment can be done to the same precision and show the feasibility of a full-length segmented x-ray FEL based on SCU technology.
One of the most challenging aspects of the SCU project is the position control and stability of magnetic components to the micron level, which will be developed and tested with the PATS.
There are two absolute encoders and here is the explanation from Gary: The original design was an actuator with 1 micron repeatability. Harmon specified a linear encoder. An encoder with 50nm resolution was selected. Heinz-Dieter in his PRD stated we needed 250nm resolution. With the linear encoder that resulted in ±5 pulses. Harman said that may be OK, but more pulses would be easier to tune. He suggested the AksIM-2 rotary encoder. I selected 17 bit resolution. That results in 131,072 counts per 500 microns, or .0038147 microns/pulse, approximately 66 pulses/250nm. This may be easier to tune. I put both encoders in this version of the actuator to experiment with both, to determine if one or the other could do the job, or if both are required.
Travel range of each actuator
5 mm (+/- 2.5 mm)
Lead screw pitch
0.5 mm/rev
Required positioning accuracy
0.25 um
Gear reducer