Single crystal X-ray diffraction HPAD based systems

Structure determination of single crystals

XtaLAB PRO MM007

The XtaLAB PRO MM007 is designed around the popular HPAD (hybrid pixel array detector) technology. This systems may be configured with either the single or dual wavelength rotating anode X-ray sources making it suitable for a wide range of sample types, from inorganic structures to organic compounds and MOFs.

The near perfect detector, based around the latest HPAD advances, greatly expands the capabilities of the systems in terms of speed of data acquisition and more accurate measurement of weak data. The standard detector in the XtaLAB PRO series is the PILATUS3 R 200K, which is well proven in the field and based on the same technology adopted by synchrotron beamlines around the world. The outstanding characteristics of these detectors ensure that every XtaLAB PRO diffractometer will produce the best data possible for the X-ray source selected.

Features

  • True shutterless data collection
  • Extremely low noise detector allows better measurement of weak data
  • ‘Top-hat’ point spread function of one pixel
  • High performance, low maintenance rotating anode
  • Ergonomic enclosure design
  • kappa goniometer; optional partial chi goniometer
  • Optional cryo-devices including Oxford Cryo 800 and Cobra
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XtaLAB PRO accessories

Description
Oxford Cryo 800

The Oxford Cryostream Cooler: The 800 Series Cryostream is the most robust, efficient and user-friendly liquid nitrogen based low temperature system available today. Specific features include a superior laminar flow system, meaning virtually zero risk of icing, extremely quiet running and a fast-start system resulting in a cool-down time to 100K of just 20 minutes.

Oxford Cobra

The Oxford Cobra is the non-liquid nitrogen Cryostream. Combining the efficiency of a Cryostream with the advantages of a non-liquid system, the Cobra offers the ultimate solution for both macromolecular and small molecule crystallography.

VariMax VHF

The VariMax VHF optic (for rotating anode sources) is optimized for small crystals, where a higher flux is achieved by increasing the divergence angle.

The PILATUS3 R detector series are designed for home laboratories to provide the best possible data collection peformance. These detectors combine two key technologies, single-photon counting and hybrid pixel technology, which eliminates detector noise and provides sharper, better resolved Bragg peaks. The following are a list of frequently asked questions regarding HPAD detectors and how they compare to other detection devices, such as CCDs and phosphor-based CMOS detectors.

How do PILATUS3 R detectors achieve direct detection?

PILATUS3 R detectors are Hybrid Pixel Array Detectors (HPADs), which convert X-ray photons directly into electron/hole pairs in the silicon wafer as shown below. Unlike other detectors they do not need to convert the X-rays into visible light as an intermediate step.

  1. X-ray photon absorbed in the Si wafer.
  2. Electron-hole pairs are generated and holes are funneled towards indium bump.
  3. Si wafter is connected to CMOS circuit by indium bumps for effective charge transfer.
  4. Pixel signal processing unit, shapes and amplifies then compares vs reference value. If above, it is counted, if below not counted.

How does a PILATUS3 R differ from a standard CMOS or CCD detector?

The primary differentiator between PILATUS3 R and both CCD (Charged Coupled Device) and standard CMOS (Complementary Metal Oxide Semiconductor) detectors is the direct detection of X-ray photons and the hybrid pixel that counts events above a threshold. Both CCD and standard CMOS detectors require the X-ray photon to first be converted to visible light as an intermediate step. Standard CMOS detectors use a fiber optic stub and CCD detectors use a fiber optic taper, and both are integrating detectors, not photon counting.


  1. X-ray photon absorbed – visible light produced and scattered in all directions.
  2. Light passes into fiber optic stub, reflection from surfaces causes more scattering and diffusion.
  3. Light passes along fiber optic stub, more scattering and diffusion before striking a photodiode.
  4. Electron-hole pairs are generated in the photodiode.
    Amplification, transmission and digitization.

Light loss, diffusion and scattering occurs at all five interfaces leading to signal loss and noise. Amplification, transmission and digitization also add noise.

But PILATUS3 R detectors contain a CMOS chip...

Correct, PILATUS3 R and standard CMOS detectors both contain devices that are manufactured using CMOS technology, but they operate in very different ways.

What are the advantages of PILATUS3 R detectors compared to standard CMOS or CCD detectors?

HPADs have some advantages over integrating detectors, such as CCDs and standard CMOS detectors. For example, both CMOS and CCD detectors convert X-ray photons to light using a fiber optic stub (CMOS) or taper (CCD). Light loss occurs at the interfaces between the phosphor-stub and stub-sensor as well as in the glass material itself. Light diffusion and light loss also occur through the fiber optic stub. As a result, CCDs and standard CMOS detectors have a point spread function with longer tails than a Gaussian causing data to spread across many pixels.

HPADs also have the advantage that they are inherently free from dark current and readout noise. The absence of these noise sources allows PILATUS3 R detectors to produce data with excellent signal-to-noise ratio.

What does ‘top-hat’ point spread function mean?

As a result of no light diffusion within the detector, PILATUS3 R spots have a ‘top-hat’ point spread function of one pixel rather than the long tail PSF seen with CMOS and CCD detectors.


Comparison of ‘top-hat’ vs Gaussian Point Spread Functions

I thought PILATUS3 R detectors were just for synchrotrons. Are they really suitable for the home lab?

Considering the main features of PILATUS3 R detectors, direct detection and single photon counting, they actually suit the home lab perfectly: recording the highest signal and lowest noise from the incident photons available.

The PILATUS3 R has a pixel size of 172 microns. Can I resolve long unit cells?

Yes, we have collected data on Mouse Angiotensinogen with resolution of the 462 Å cell axis at 260 mm. We have also resolved the 616 Å edge of a ribosomal subunit at 200 mm.

Are the PILATUS3 R detectors offered by Rigaku the same detector I use at the synchrotron?

Yes, one slight change in speed, the home lab versions run at 20 Hz or 7 ms readout time.

Can the PILATUS3 R operate in shutterless mode as I do at the synchrotron?

Yes

How do I calculate a strategy when using shutterless mode?

The data collection strategy protocol is the same for both shutterless and conventional data collection with regard to desired completeness and redundancy. In the case of shutterless data collection, you have the advantage that you can collect narrower images without the penalty of longer data collection times. This can be an invaluable benefit for samples whose orientation or mosaicity are not ideal.

What are the cooling requirements for PILATUS3 R detectors?

The PILATUS3 R 200K-A detector is fully air-cooled and maintenance-free. PILATUS3 R 300K and 1M use low-maintenance, closed-circuit water cooling for temperature stabilization at 23° C.

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