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Optimizing the DMC Detector for Enhanced Performance in Cold Powder Diffraction

This presentation from the MCNSI Meeting in Grenoble on May 26, 2005, discusses the optimization of the DMC detector, which is over 25 years old, for use in cold powder diffraction. The current detector lacks available spares and does not meet modern performance standards. We will explore the schematic design, simulated vs. measured data, and the proposed changes, such as increasing the detector height from 9 cm to 30 cm, while changing the detector-sample distance for improved intensity and resolution. Ongoing projects and component developments will also be highlighted.

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Optimizing the DMC Detector for Enhanced Performance in Cold Powder Diffraction

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  1. MCNSI Meeting Grenoble, 26 May, 2005 Detector Optimisation for the Cold Powder Diffractometer DMC U. Filges Laboratory for Material and Developments Paul Scherrer Institut CH-5232 Villigen

  2. Motivation MCNSI Meeting Grenoble, 26 May 2005 • DMC detector is about 25 • years old • no spares available detector performance\design is not state of the art (BF3, pressure) View on DMC at SINQ

  3. Schematic Design of DMC MCNSI Meeting Grenoble, 26 May 2005 Schematic design of the cold powder diffractometer DMC and McStas Model

  4. Virtual Experiment MCNSI Meeting Grenoble, 26 May 2005 McStas instrument file for the DMC instrument including cold source, neutron guide and all components of the diffractometer including sample Na2Ca3Al2F12– virtual experiment comparison of measured and calculated data - sample Na2Ca3Al2F12; height: 30 mm; diameter: 10 mm - measured and calculated data agree very well Bragg peak resolution   16 Bragg peaks including symmetrically equivalent reflections(range of 20 – 100 degree)  used wavelength: 2.567 Å

  5. Simulation result I MCNSI Meeting Grenoble, 26 May 2005 Comparison of simulated and measured data: part 20 – 62°

  6. Simulation result II MCNSI Meeting Grenoble, 26 May 2005 Comparison of simulated and measured data: part 62 – 100°

  7. Simulation result III MCNSI Meeting Grenoble, 26 May 2005 Comparison of peak resolution for Bragg peaks 28.98° (left) and 51.4° (right)

  8. Optimized Detector Parameters MCNSI Meeting Grenoble, 26 May 2005 detector height – from 9 cm of the present detector to 30 cm of the new detector system decreasing the detector-sample distance from presently 1.5 m to a smaller distance => increasing intensity; decreasing instrument resolution BF3 Detector replaced by a He-3 detector under higher pressure

  9. Changing the Detector Height MCNSI Meeting Grenoble, 26 May 2005 G = 3.4 Comparison of PSD images of the 9cm/30cm-detector for bragg reflections 35.73° , 51.42° and 90.2°

  10. Changing the Detector – Sample Distance MCNSI Meeting Grenoble, 26 May 2005 Comparison of intensity gain vs. loss of resolution for bragg reflection 41.49°

  11. Ongoing Projects MCNSI Meeting Grenoble, 26 May 2005 continuation of FOCUS intercomparison (McStas/Vitess) including the new 2D-Detector • component development • extension of Guide_tapering component – avoid direct view to the guide entry • multi-pipe window component SINQ – hall extension sector 50; in opposite to the present guide hall

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