A Test of the Laser Alignment System ALMY at the TTF-FEL

(MO-3-25)

S. Roth, S. Schael *, G. Schmidt  

DESY, Hamburg, *MPI M$\ddot{u}$nchen

The laser alignment system ALMY was tested at the undulator section of the TESLA test facility.

ALMY is a multi-point alignment system that uses an infrared laser beam, acting as alignment reference, which transverses several transparent silicon sensors. The sensors measure the laser beam position in both transverse coordinates. Thermal effects are shielded by means of an alluminium tube around the laser beam.

The test has shown that the position of the undulator modules relative to each other has been determined with a precision of 0.1 mm, limited by the accuracy of the mechanical support of the sensors. Additionally, ALMY allows to measure movements or drifts over several days and we found that the undulator components are stable within 10 micro meter. The resolution of the sensors is better than 2 micro meter over the 15 m long alignment system.