Microimaging

The Great micro-imaging accessories are built up from the following components:

• The Gradient Controller calculates the gradient pulses "on the fly" allowing for an infinite number of gradient switching points during experiments without limitation of waveform memory size. The intelligent gradient controller has several modes to control gradient waveforms which can be configured for complex gradient shapes, waveform lists, or just fast throughput. The gradient controller provides 16-bit resolution output for the X, Y, Z gradients with a time resolution of 25 ns.

• The Great Master Unit is the interface between the gradient controller and the gradient current amplifiers. The digital gradient pulse information is routed to the individual gradient amplifiers and to the Great Bo compensation unit. The applied duty cycles and the temperature of the gradient coils are controlled during the experiments, as well as the state of the individual current amplifiers in order to protect the gradient coils and the imaging accessory.

• The Gradient Power Supplies Great40 and Great60 provide 40 A and 60 A maximum current respectively and 120 V.
  
  
  • The current regulated amplifiers get digital gradient pulse input, which is converted to analog signals in the amplifiers and not in a separate analog unit. Such a design prevents distortions, caused by analog signal transfers.
  • The maximum current output stage of the amplifiers can be set in steps of 10 A, which increases the dynamic range of the output current.
  • The amplifiers include blanking units for dedicated applications.
  • Offset adjustment is under software control as well as impedance matching for a wide range of gradient coil loads.

• The Great Bo Shift Compensation Unit receives the input signal from the DPP in digital form. The adjustments are under software control and settings for various gradients, magnets or methods can be stored on disk in the same manner as for shim settings.

• The Gradient Water Cooling Unit, BCU 20 provides cooling water for the gradient systems. The temperature can be adjusted manually or under software control. The unit can not only be used for cooling the gradient coils, but also for temperature adjustments of the sample up to approximately 50 °C.

• The Imaging Probes feature exchangeable rf coils in various diameters for single or dual frequency ¹H and X-nucleus applications. Thus, the filling factor and sensitivity can be optimized for all types of samples, even with diameters down to less than 1 mm. For most systems variable temperature operation is also possible. Finally, special probes are also available for diffusion experiments.