PRIGo: a new multi-axis goniometer for macromolecular crystallography.

The Parallel Robotics Inspired Goniometer (PRIGo) is a novel compact and high-precision goniometer providing an alternative to (mini-)kappa, traditional three-circle goniometers and Eulerian cradles used for sample reorientation in macromolecular crystallography. Based on a combination of serial and parallel kinematics, PRIGo emulates an arc. It is mounted on an air-bearing stage for rotation around ω and consists of four linear positioners working synchronously to achieve x, y, z translations and χ rotation (0-90°), followed by a ϕ stage (0-360°) for rotation around the sample holder axis. Owing to the use of piezo linear positioners and active correction, PRIGo features spheres of confusion of <1 µm, <7 µm and <10 µm for ω, χ and ϕ, respectively, and is therefore very well suited for micro-crystallography. PRIGo enables optimal strategies for both native and experimental phasing crystallographic data collection. Herein, PRIGo hardware and software, its calibration, as well as applications in macromolecular crystallography are described.

Automatic loop centring with a high-precision goniometer head at the SLS macromolecular crystallography beamlines.

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.

Free-moving Quantitative Gamma-ray Imaging.

The ability to map and estimate the activity of radiological source distributions in unknown three-dimensional environments has applications in the prevention and response to radiological accidents or threats as well as the enforcement and verification of international nuclear non-proliferation agreements. Such a capability requires well-characterized detector response functions, accurate time-dependent detector position and orientation data, a digitized representation of the surrounding 3D environment, and appropriate image reconstruction and uncertainty quantification methods. We have previously demonstrated 3D mapping of gamma-ray emitters with free-moving detector systems on a relative intensity scale using a technique called Scene Data Fusion (SDF). Here we characterize the detector response of a multi-element gamma-ray imaging system using experimentally benchmarked Monte Carlo simulations and perform 3D mapping on an absolute intensity scale. We present experimental reconstruction results from hand-carried and airborne measurements with point-like and distributed sources in known configurations, demonstrating quantitative SDF in complex 3D environments.