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NIST Center for Neutron Research

CHRNS: MACS sample rotator

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Principle

Given that neutron instrument motors and detectors take several seconds to move and reach a stationary state to make the next data point measurable, we are developing a constantly rotating sample device that removes the deadtime associated with moving. For optimal samples, the continuous data collection and sample rotation can result in a double neutron count duty cycle.

 We have recent experience adding a CHRNS: Cryogenic Goniometer to NICE and the motor control system, VIPER, was also updated to be compatible with time-stamps giving confidence in a swift incorporation of this device into the experiment control and data acquisition procedures.


System: Rotation Stage for 100mm ILL Cryostat

The rotation system consists of:

  • rotation stage to be mounted on top flange of the 100mm ILL cryostat
  • rotatable sample stick to be inserted in 100mm sample well
  • controller, cables

Specs for the rotation system:

  • Aperture diameter: 100+ mm
  • 360 deg rotation with adjustable rotation limits
  • Bi-directional rotation
  • Position accuracy at sample position: 0.005 deg
  • Backlash at sample position: no more than 0.01 deg
  • Axial load capacity results from operation with vacuum in the sample well
  • Rotation speed MAX: no less than 2 deg/s
  • Rotation speed MIN: up to 0.1 arcmin/s
  • Distance from cryostat top flange to sample position: 1192mm
  • Nothing magnetic allowed within sample position, up to 1000mm above sample position
  • Sample stick material: 316 SS
  • Sample stick shall be ‘very stiff’ to avoid twist while rotation
  • The stick should be designed for continuous rotation back and forth with >1 year between service/failure
  • Calibrated, 1.4K– 300K, Cernox sensor attached at the sample stick bottom end
  • Sample mount: 5/16-18 threaded stud
  • Heat buffers to allow normal operation of the cryostat down to 1.5K at sample position
  • Sample stick shall be easily removable from the cryostat for sample change without removing the rotation stage mounted on top flange of the cryostat
  • Rotation system shall provide vacuum in the sample well of the cryostat, leak rate shall be better than 1e-8 mbar/lt sec

 

 

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Created February 4, 2023