|The compact cylinder cell is a high-pressure
diamond cell designed to facilitate light scattering and X-ray diffraction of materials at
pressures to one million atmospheres. Machined from 440C steel, the circular halves of the
instrument feature a piston and cylinder arrangement. The diamond mounts are flat tungsten
carbide discs. Cone angle openings of 60º are located top and bottom. Side ports provide
access to the sample through the gasket for use with high-intensity radiation such as
produced by a synchrotron source. Pressures are generated by tightening four Allen screws
compressing Belleville spring-loaded washers. The piston and cylinder arrangement provides
superior stability. The compact dimensions of this diamond cell allow it to fit a variety
of instrumentation and microscope stages. Assembled with either Type I or Type IIa anvils,
this cell is ideal for most high-pressure studies including Raman, Brillouin, and infrared
spectroscopy as well as single-crystal or powder X-ray diffraction.
Limited production in 2004 of Vascomax cells for liquid nitrogen cryogenic experiments.
The selection of diamond type and culet size should be based upon the choice of experimental techniques to be employed and the maximum pressures to be achieved. The diamond anvils are skillfully cut from natural, gem quality stones with 16 pavilion facets, a 70% table, and a working surface called the culet. The table and culet of the anvils are precisely cut to be parallel to the crystallographic (100) plane. The smaller the diameter of the culet the higher the pressure that can be achieved. Typical culet sizes range from 0.2 to 0.6 mm.
Mounts can be constructed of various materials, with beryllium and tungsten carbide the most popular. The beryllium mounts are used in X-ray diffraction experiments because they are invisible to X-rays but they cannot withstand pressures above 40 GPa. The tungsten carbide mounts can withstand the highest pressures and are a favorite for spectroscopic studies.
Gasket material also defines the attainable pressure extreme. Popular choices are Inconel steel, stainless steel and rhenium. Because of its shear strength, rhenium gaskets can be used to the highest pressures. Typical thickness and hole sizes range from 0.15 to 0.25 mm.
· 1,000,000 atmospheres = 100 GPa = 1,000 kbar.