Figure 1: P14 Beam Conditioning Unit
Figure 2: Layout of P12 Double-Multilayer Monochromator
Figure 3: MARVIN sample changer at P13
The Fiedler team focuses on the construction, customisation and integration of X-ray optics, precision mechanics, robotics, control electronics, cryogenics and control software for synchrotron-based structural biology research.
Previous and current research
EMBL has designed, built and operates three beamlines for structural biology at the PETRA III synchrotron radiation source on the DESY campus in Hamburg. Beamline facilities are dedicated to the leading techniques for X-ray-based structural research of biological samples: small angle X-ray scattering and macromolecular crystallography. Our team provides expertise in X-ray optics, precision mechanical engineering, robotics, control software and electronics. It is in charge of the X-ray optical elements, experimental endstations, vacuum system, cryogenic system, control system, data-acquisition system, technical infrastructure and parts of the civil engineering.
All three beamlines are in full user operation. They feature focusing X-ray optics based on adaptive bimorph mirrors and on Compound Refractive Lenses, multi-degree-of-freedom heavy-duty detector stages for the large and fast area pixel detectors, white and monochromatic X-ray beam monitors systems and in-house developed beam conditioning units. The main part of the instrument control, including motion control, is carried out using an industrial field bus system. A central cryogenic supply system for the different liquid nitrogen consumers at the beamline endstations, comprising control and safety system, has been implemented.
Each beamline is equipped with a fixed-exit double crystal monochromators (DCM) with liquid nitrogen cooling. Their thermal and vibrational stability are under continuous improvement making use of interferometer based metrology and Finite Element Analysis.
As an alternative to the DCMs, a double-multilayer monochromator (DMM) system has been developed in house. It offers a wider energy bandpass and can enhance the totally available flux density by 1-2 orders of magnitude. At the P12 beamline, a DMM is in user operation delivering the beam with the highest photon flux for SAXS experiments at PETRA III, and worldwide.
Instrumentation for time-resolved studies
The extreme intensities achieved with the DMM optics can be used to carry out time-resolved solution-scattering studies down to the microsecond range. In general, this requires a series of additional devices, such as a laser triggering system, synchronization electronics or an X-ray beam chopper, which are developed and/or implemented by the instrumentation team.
There is a strong demand to automate the measurement process at structural biology beamlines as much as possible, so as to allow for high throughput and remote experiments. In this context, a robotic sample mounting system named MARVIN has been developed for the MX applications (see figure 3). This is characterised by high sample-storage capacity, fast sample-mounting speed and flexibility. It is integrated, like all beamline elements, into a software-based control system which allows for a heterogeneous control environment and provides distributed access. Two instruments, serving a horizontal and a vertical diffractometer, have been developed for the P13 and P14 beamlines and are in user operation.
Future projects and goals
- X-ray optics are constantly upgraded in order to stay at the cutting edge in terms of beam parameters for structural biology beamlines. A multilayer monochromator is planned for the P14 MX beamline, similar to the instrument developed for P12. In combination with new focusing optics, record flux densities are expected to be achieved which will be used in particular for new serial crystallographic applications.
- The next step for completing the automation pipeline for MX has been the implementation of the Crystal Direct Harvesting system (EMBL Grenoble/ARINAX) in the sample preparation laboratory attached to the beamline facilities. Based on the same robotic platform as for the MARVIN systems, an automatic transfer of the samples prepared by the CDHarvester is under development.
- In the next years, DESY plans to transform the PETRA III synchrotron into a diffraction limited storage ring (PETRA IV), which will necessitate also major upgrades of the EMBL beamlines. The team wants to contribute to the modification of beamline layouts, the design of new X-ray optics and instrumentation for the endstations that are complying with the increasing requirements in vibrational stability and power density.