577 / 2019-03-20 20:04:19

The Recent Progress of High Pressure Neutron Diffractometer at CMRR

Neutron powder diffraction; High pressure; High temperature

全体主题 > High Pressure Physics and Materials Science

Fenghuang is a high pressure neutron diffractometer at the China Mianyang Research Reactor (CMRR) dedicated to research on the microstructure of materials at ambient and extreme conditions. It was firstly built in 2005 at the Swimming Pool Research Reactor-300 (SPRR-300) in Mianyang, and then moved to CMRR in 2013. Through the combination of a horizontally focusing neutron guide and a vertically focusing monochromator, the neutron flux at the sample position is up to 2.84 × 106 n s−1cm−2. The resolution of the diffractometer can be adjusted by a horizontal slit for different sample. The superposition scan mode enables each detector to measure the complete diffraction pattern and simplifies the correction of the efficiency of the counting channels.
Because of its high flux, Fenghuang can be used to measure small samples (mm3), such as high-pressure samples. The high-pressure devices, including two self-designed opposed-anvil high-pressure equipment (maximum load are 300 kN and 1500 kN) and a Paris-Edinburgh pressure (maximum load is 2000 kN), were equipped. The 1500 kN pressure equipment can also generate the maximum current of 500 A to heat the high-pressure cell with water cycle protection. Thus, a sample environment of high pressure coupled with high temperature can be achieved. Fenghuang offers a suite of sample temperature environments. A closed-cycle cryostat (7 K to 300 K) with a diameter of 9 mm TiZr nullscattering alloy sample holder is suitable for studies at ranging from 7 K to ambient and its neutron transmission is 83%. Samples can be replaced directly while helium flow is maintained in the cryostat at low temperature. A vacuum high-temperature furnace (T ≤ 1000 ℃) with vanadium heating elements and a diameter of 10 mm sample container is available and its neutron transmission is 77%. A low-temperature (3 K to 300 K) and gas high-pressure (≤100 MPa) device refrigerates by a cold finger of closed-cycle Displex refrigerator. It can be used also in combination with piston cylinder-type high-pressure generating device which replaces the gas sample cell. A new vacuum furnace (T≤ 1600 ℃) is also being constructed. A 12-sample changer for room temperature was equipped as well.