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Next-gen X-ray crystallography

19th June 2017

Posted By Paul Boughton


The XtaLab mini II cabinet design
View inside the XtaLab mini II diffractometer
CrysAlisPro data collection and reduction software

Paul Swepston introduces a benchtop X-ray crystallography system with hybrid photon counting detector 

Riding on the success of its previous generation of products, an expert in X-ray crystallography has recently developed a new benchtop X-ray crystallography system.

The new XtaLab mini II system from Rigaku differs from its predecessor by the inclusion of a hybrid photon counting (HPC) detector, called the HyPix-Bantam.

HPC detectors are at the cutting edge of diffraction technology, and are widely used at synchrotron beamlines due to their high sensitivity and fast read-out speeds.

The whole system is controlled by the popular CrysAlisPro software, which offers users the ability to complete their structure determination with one software package.

The XtaLab mini II cabinet is compact and robust. With dimensions of just 560 x 395 x 674mm and a weight of approximately 100kg, it is a very small diffractometer, which makes it easy to install almost anywhere.

The control buttons on the front display are clearly labelled, and the fail-safe radiation enclosure means that the system is safe and easy to use even for inexperienced users. This lends itself well to being used as a teaching tool. 

Although the door is opaque, users are still able to view the inside of the cabinet via a camera linked to the PC. 

Should low temperature data collection be required, the diffractometer is compatible with various cryo devices, such as Oxford Cryosystems’ CryoStream 800 attachment. 

The system is equipped with a molybdenum fine focus X-ray source and coupled with Shine optics for enhanced flux. 

For easy maintenance and low cost of ownership, it uses a standard X-ray tube, which is readily available should a replacement ever be required. 

Goniometer 

The entire system has just three moving parts: the shutter and the phi and omega axes  of the goniometer (Fig. 2). The latter of these were designed specifically for ease of mounting – useful when training new users. 

The simple design also means minimal maintenance and no special infrastructure requirements, meaning that the system can run with very little downtime for servicing. This is important for universities or service laboratories with a high throughput of samples. HPC dectector 

The new HyPix-Bantam detector is a next-generation two-dimensional semiconductor detector designed specifically to meet the needs of the home lab diffractionist. It is an HPC detector with a large active area of approximately 3,000mm2, a small pixel size of 100 μm2 ×100 μm, and a high count rate of greater than 106 cps/pixel.

A big advantage of HPC detectors is that each pixel is independent and the overall dynamic range of a detector is the sum of the dynamic range of each individual pixel. 

Each pixel of the HyPix-Bantam has two 16-bit counters, and these can be combined to work as a single 31-bit counter, achieving very wide dynamic range. 

Another benefit of HPC detectors is the extremely low background noise and high sensitivity, meaning that even low photon counts are detected. 

The combination of all these features means that images with both strong and weak reflections present are measured extremely accurately without the need to do a second pass of reciprocal space to recollect the image at a lower exposure time. 

The nerve centre of the XtaLab mini II system is the CrysAlisPro software, which ties all the new detector features together through a highly parallelised architecture, resulting in a reliable system for generating 3D structures of crystalline materials. It is a comprehensive but user-friendly, semi-automated software package, ideal for both researcher and student level users. It links directly to Olex2, a freely available software package for structure solution and refinement. 

Applications 

In a recent application data was collected on the XtaLab mini II system at room temperature on a crystal of cytidine with dimensions 0.167 × 0.171 × 0.231mm. The exposure time was set to 10 seconds per frame with 648 images collected in just under 1 hour 50 minutes.

Excellent data was collected on this light organic sample in less than two hours using the new diffractometer.

The HyPix- Bantam detector allows data to be collected very quickly due to its high sensitivity and dynamic range.

Paul Swepston is with Rigaku





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