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HRPT: High-Resolution Powder Diffractometer for Thermal Neutrons

Laboratory for Neutron Scattering, Paul Scherrer Institute

This web-page is not anymore updated!

Please use new HRPT web-page shown below


Technical Specifications:

HRPT layout

Neutrons: thermal (0.94-2.953Å) beam 1RNS41 from a water scatterer close to the SINQ target.

Neutron flux measured by gold foil activation.

Primary collimation: Gd-O Soller collimators with a1 = 6', 12', 24' (high resolution), - = approx. 40' (high intensity)
Liquid N2 cooled Si filter: 20 cm length
Monochromator: Ge (hkk) of wafer type, 28 cm high, variable vertical focusing, total mosaic halfwidth 15'
Secondary collimation: variable computer controlled slit system for monochromatic beam
Radial collimators:
(from JJ X-Ray, Risø, Denmark)
Oscillating mylar-Gd-O collimators to eliminate Bragg peaks from sample environment such as from cryostat or furnace tails. FWFM are 14mm and 28mm.
PSD detector:
(LCP1600 from Cerca, F-26104 Romans) (more pictures)
3He (3.6 bar + 1.1 bar CF4), 25 x 64 = 1600 counters, step 0.1, 15 cm high, radius 1.5 m, effective detection length 3.5 cm
Stroboscopic mode of operation The maximal time resolution is 10ms: for instance a process started with the strobe signal each minute can be chopped by time interval of 10 milliseconds resulting in simultaneous collection of 3000 powder diffraction spectra corresponding to the different time from the strobe signal. Maximal number of histograms is about 100000.
HRPT gas mixture cleaning/adding system (more pictures) cleaning of the gas mixture from (O2, H2O, etc) by a circulation of the gas mixture through the appropriate filters without pumping out the mixture.
Sample containers, beam size, sample space: cylindrical, normally V tubes (also double cylinders), diameters 5 to 10 mm, usable height up to 50 mm, sample under He gas atmosphere for good thermal contact, sealed by In wire on the top flange of 25 mm diameter, M6 screw to fix the sample container;
diameter of sample table = 40 cm, height sample table to neutron beam center = 270 (400) mm;
evacuated Al pot with oscillating closed-cycle He refrigerator.
Sample temperature: 120 mK - 1800 K
Magnetic field: superconducting magnet MAO6, field H vertical to scattering plane, H up to 6 T. MAO9 at HRPT (tight fit)
Zero matrix pressure cells: up to 8, 15 kbar for full scattering angle range. Example of pattern,
Sample changers: Room temperature sample changer for eight (8) samples, low temperature sample changer for four (4) samples (more pictures) , low temperature sample changer for five (5) samples with sample rotation

V. Pomjakushin, "High Resolution Powder Diffractometer for Thermal Neutrons." (pdf 31 Mb).
Talk given at the AIC Information Day on "Large Facilities for Crystallography Studies: Synchrotron and Neutron sources" October 19th, 2009 , Paul Scherrer Institut, Villigen, Switzerland.
"Experimental powder diffraction using HRPT as an example" as it is (pdf 41 Mb).
Master class, October 26th, 2013, Paul Scherrer Institut

Possible choice of neutron wavelength and corresponding effective counting rates (calibrated by V) of the HRPT detector relative to the choice of λ = 1.886 Å in HI mode with 40- collimation. Typical  modes of HRPT are HI:40-, MR:12-24, HR:6-12. Counting rates are decreased by the factor of ~3 and ~(8-10) for MR and HR, respectively. Typical resolution parameters.

V. Pomjakushin, Last modified: 05/Mar/2014 11:43