title: Automatic loop centring with a high-precision goniometer head at the SLS macromolecular crystallography beamlines.
abstract: Automatic loop centring has been developed as part of the automation process in crystallographic data collection at the Swiss Light Source. The procedure described here consists of an optional set-up part, in which the background images are taken, and the actual centring part. The algorithm uses boundary and centre-of-mass detection at two different microscope image magnifications. Micromounts can be handled as well. Centring of the loops can be achieved in 15-26s, depending on their initial position, and as fast as manual centring. The alignment of the sample is carried out by means of a new flexural-hinge-based compact goniometer head. The device features an electromagnet for robotic wet mounting of samples. The circle of confusion was measured to be smaller than 1 µm (r.m.s.); its bidirectional backlash is below 2 µm.
authors.affiliation: Paul Scherrer Institut, Villigen, Switzerland. anuschka.pauluhn@psi.ch
authors.forename: Anuschka
authors.initials: A
authors.lastname: Pauluhn
authors.forename: Claude
authors.initials: C
authors.lastname: Pradervand
authors.forename: Daniel
authors.initials: D
authors.lastname: Rossetti
authors.forename: Marco
authors.initials: M
authors.lastname: Salathe
authors.forename: Clemens
authors.initials: C
authors.lastname: Schulze-Briese