Neutron Diffractometers

Florent Cipriani
EMBL Grenoble, BP181, rue Jules Horowitz, 38042 Grenoble Cedex 9, France

FINDer ( Fast Imageplate Neutron Diffractometer)

FINDer is a Neutron Laue diffractometer using image plates (IP) as detector.

FINDer is the industrial version of  the LADI quasi laue diffractometer that has been developed at the EMBL Grenoble outstation for protein crystallography (routinely used at the ILL since 1998). FINDer has an extended application field. It can be used either for material science (thermal neutrons, large He cryostat) or for biology experiment (cold neutrons).

The first unit has been constructed by the SICN company and is now installed at the ILL on the VIVALDI station. It sits at the end of a thermal neutron guide that provides a white beam (0.8<L<4.5 Å) that can be filtered to 0.8<L<3 Å or 3<L<4.5 Å. 

The sample environment includes an ILL 'Orange' cryostat for1.5 K to 600 K with optional standard dilution inserts (down to 50 mK) and high-pressure cells up to 49 mm in diameter.  

A time of flight analyser has been integrated in the diffractometer to monitor the tuning of the neutron band pass filter, and to record the neutrons energy spectrum together with the diffraction patterns. 

Technical and commercial information:

EMBL: cipriani@embl-grenoble.fr 
EMBLEM: martin.raditsch@embl-em.de 

Principle

A neutron image plate is a storage phosphor plate sensitive to neutrons. Image plates are two-dimensional detectors. When exposed to neutrons, 'colour centres' are created inside the phosphor in quantity proportional to the neutron dose. As in photographic films, these colour centres makes a latent image. A red laser spot that releases the colour centre reads this latent image. Blue light is then emitted in a quantity proportional to the number of colour centres. While the plate is scanned, the intensity of the blue light is recorded as a function of the laser spot position, making then an intensity map of the latent image. Unlike photographic film, the plates are reusable after erasure by exposure to light.

The detector is a vertical drum internally covered with neutron image plates. The sample sits in the centre of the drum and can be rotated around the drum axis. Different sample holders can be installed, including cryo cooling systems. The diffractometer is designed to accept further extensions for magnetic sample environment. To hit the sample, the neutron beam passes through two holes in the drum.

The detector works in three phases: firstly, an intense light erases the image plates; secondly, the sample is exposed to neutrons and diffraction is recorded on the image plate; thirdly, a reading head scans the drum (the drum rotates while the head moves along it).

The reading head is composed of a PMT placed in front of the image plate. An optical system focuses a red laser diode on the image plate, just in front of the PMT, this excites blue photostimulable luminescence that is measured in the PMT. A filter in front of the PMT eliminates the red light. The PMT current is integrated on the surface of each pixel. The drum is scanned in 'phonographic' mode (a one pixel width spiral). The pixel values are stored on a computer disk and can be displayed as colour map images on a computer screen. A set of patterns can be collected automatically from one sample. For each acquisition, the sample parameters can be set (sample orientation, temperature...)

Main features

FINDER is a turnkey diffractometer based on an open architecture and modular design for flexibility and easy integration in the user environment.

• Compact design: 2x1x1 m (HxWxD), Mounted on 3 Air Pads
• Beam height: from 1100 to 1600 mm (other upon request)
• Compatible with different sample holders, including large He cryo cooling devices
• High performance image plate detector:
• •  Sensitive area: 800 x 400 mm (4/5 of the internal surf. of a Ø 320 mm, H 400 mm cylinder)
  •  Pixel Size: from 100 x 100 to 400 x 400 µm
  • Readout time: 2 to 7 minutes, (400 to 100 µm pixels) 
  • Dynamic range: 16 bits
  • Spatial resolution: 200 µm FWHM
  • DQE: 40 to 60%
  • PC / Windows NT based architecture

• PC/Windows NT-based architecture
• Ethernet interface for data transfer
• User friendly control software:
• • Full control of the instrument through a GUI
  • One access level for tests and tuning, one access level for experiment control
  • Windows NT standard application written in Visual Basic (VB)
  • Object oriented software using ActiveX components
  • Ability to add experiment dependant controls (*temperature)
  • Time Of Flight* (TOF) option for beam energy spectrum control
  • Experiment control process can be modified easily (Visual Basic module)
   

Options

• Beam energy spectrum monitor (Time of Flight)
• Sample cryo cooling control

More information

Email: cipriani@embl-grenoble.fr