HRPD

1. Top-loading 100 mm Closed Cycle Refrigerator (CCR) with a base temperature of 7 K. In-situ-heated slab geometry cans may be run up to ~ 400 K in this CCR; a specially-shielded sample holder may be heated up to ~ 680 K.
2. Top-loading 50 mm ‘orange’ cryostat with a base temperature of 1.5 K. He-3 or dilution inserts are available for experiments in the hundreds/tens of mK ranges.

HRPD uses a suite of heated slab geometry sample containers for controlled high-precision temperature-dependent studies (below). Cells (1) through (4) have dimensions perpendicular to the incident beam of 18 mm x 23 mm (w x h) and depths of (1) 2 mm, (2) 5 mm, (3) 10 mm and (4) 15 mm. A special narrow cell (10 x 23 x 5 mm) is also available (5). Typically, the thinner cells are used for small or highly absorbing samples.

Samples are sandwiched between steel-framed vanadium windows screwed onto the Al-alloy slab-can frames (usually with an indium-wire seal). Exposed surfaces on the front of the sample container are shielded with Gd and Cd foil. Heating is achieved using a Watlow Firerod cartridge heater inserted in the frame; measurement and control is achieved using an ITS-1990-calibrated RhFe sensor inserted in the opposite side of the frame. Extensive testing has shown that heating / cooling rates of 3 – 6 K per minute followed by a minimum wait of 10 minutes to achieve thermal equilibration ensures uniform and accurate sample temperature determination from the RhFe sensor and reduces the magnitude of any thermal gradients. For high-precision thermal expansion studies, this protocol is essential.

Study of crystalline solids that are liquids or gases at STP is done routinely on HRPD; we can readily solidify and grind such materials under liquid nitrogen and load the powders into nitrogen-cooled slab cans for study on HRPD. For some highly volatile, toxic or otherwise hazardous materials, we have gas-handling slab geometry sample holders that allow substances to be condensed directly into the sealed cell. This inevitably has the risk of producing poor powder samples with very large grains and/or some degree of preferred orientation.

1. Top-loading furnace (RAL2) with a maximum working temperature of 1050°C (1323 K).
2. Risø furnace with maximum temperature of 2000°C (2273 K)
3. A basic ‘low temperature’ furnace with a maximum working temperature of 400°C (673 K) has the advantage of a lower background (since it has only one set of vanadium foil shields) and very straightforward operation. Unlike the higher temperature furnaces, this device has no active cooling, so cooling back to room temperature for a sample change or post-heating measurement can be very slow.

​Most high-T measurements are done in unsealed cylindrical vanadium sample holders with diameters of 3, 6, 8, 11 or 15 mm, that should usually be filled to a depth of 20 mm. Other sample cells are available for extreme high temperatures, for samples that need to be sealed, or for materials that are likely to be react with vanadium. These include cylindrical containers made of stainless steel, platinum, tantalum, or molybdenum alloy (TZM).

Please contact an instrument scientist to discuss your needs.

HRPD has a sample vacuum vessel manufactured from mild steel so it is not possible to run any magnets on the instrument at present. In the future, a shielded 6 T magnet may become available, and the HRPD-X upgrade​ will deliver a non-magnetic sample tank intended to allow measurements in fields up to 10 T sometime after 2027.

Bottom-loading 20-position sample changer, currently configured for 6 and 8mm diameter vanadium cans. Room temperature operation only.

1. Standard Al7075 alloy or TiZr null-scattering alloy pressure vessels, which allow variable pressure and temperature experiments under inert-gas pressures up to 450 MPa (Al) or 540 MPa (TiZr).
2. TAV6 gas cells: Ti-6Al-4V-alloy gas-pressure vessels are now available for use on HRPD. The 540 MPa variant has a 5.3 mm wall thickness (cf., 10.5 mm in the standard TiZr cell) and a 7.0 mm bore. Good quality data can be obtained in HRPD’s backscattering detectors, even from low-symmetry complex crystals using this cell. The 770 MPa variant has a 10.5 mm wall thickness; data can be measured in backscattering, albeit with a much greater attenuation.

A wide-range of other gas-handling or gas-flow apparatus is available for in-situ reaction experiments. Contact an instrument scientist to discuss your requirements.

We have a McLennan rotation stick available that allows us to make measurements on a sample undergoing continuous rotation. This may be used to reduce the effect of preferred orientation in powders loaded into cylindrically-symmetrical sample containers. We can also collect pseudo-powder patterns from single crystals during continuous rotation. The benefit of this is to refine highly precise lattice parameters to complement a true single crystal dataset measured on SXD (or elsewhere).

A recent addition to our available sample environment equipment is a system for carrying out simultaneous neutron powder diffraction and Raman spectroscopy. This consists of a specialised CCR centre stick that can support any one of our usual sample holders (vanadium cylinders, aluminium slabs) but which is equipped with optical access from above using a very long working length telescopic lens. The optical sample chamber sits directly on top of the neutron scattering sample holder, so the two samples are under virtually identical environmental conditions.

Raman spectra are measured using one of two available portable systems. We use B&WTek i-Raman Plus spectrometers, one equipped with a 532 nm laser (~40 mW, 65-4200 cm^-1 at a resolution of 4 cm^-1) and another​ equipped with a 785 nm laser (~340 mW, 65-3350 cm^-1 at a resolution of 4 cm^-1). We also have a video microscope that can be coupled to the spectrometers for offline analysis (e.g., checking deuteration levels).

The Raman stick has an operating temperature of 20 – 300 K. It is not yet a fully mature system, so please contact an instrument scientist to discuss the practicalities of using it for your research.