The high pressure diamond anvil cell can be used to study
physical properties of interest materials under measurable pressure conditions
of 70 kbars and up.
WARNING: DO NOT APPLY PRESSURE ON THE BARE DIAMOND ANVIL SURFACES.
Store the instrument with a piece of cardboard between
the two diamond anvils to prevent abrasions. Anvils should be inspected before and after
Length: 12.5 cm.
Base Height: 2.5 cm.
Width: 7.5 cm.
Total Height: 9cm.
Weight: approx. 1 kg.
|The instrument is a leverage mechanism
designed to bring two anvils together. The anvils act both as windows and as a pressure
bearing medium. The diamonds are gem quality stones averaging 18 points in weight with
working surfaces of 0.6 millimeters. These anvils are free from imperfections and are
skillfully manufactured for parallelism of the pressure bearing surfaces and correct
crystallographic orientation. The diamonds are easily cleaned with a solvent such as
alcohol or acetone.
The pressure range of
this instrument is 70 kilobars and up. The measurement of pressure in the diamond cell is
accomplished by the ruby chip fluorescence method. Other techniques used in the
calibration of the instrument involve the visual observation of phase changes of known
CLEANING THE ANVILS
Remove the two pistons from the block before proceeding
to the following steps. The anvils can be cleaned by wiping acetone or alcohol across the
working surfaces using tissue paper twisted into a pointed tip or a tweezers wrapped with
tissue paper. Do not let the solvent come into contact with the epoxy as it will
eventually loosen the bond holding the diamond to its mount. The undersides of the diamond
anvils are cleaned by scrubbing with a round toothpick or placing a drop of acetone into
the aperture if necessary.
WARNING (FOR THE DIAMOND ANVIL CELL WITH HEATING ELEMENT ONLY) : DO NOT LET WATER COME
INTO CONTACT WITH THE HIGH TEMPERATURE CEMENT AS IT CAN DISSOLVE THE CEMENT
- Clean the two diamond anvils as instructed above.
- PRACTICE FOR ASSEMBLY OF THE PISTONS AND THE CYLINDER:
The instrument has been designed to have a tight fit between the piston and cylinder to
achieve and maintain the parallelism of the diamond anvils as pressure is changed. We
recommend that users practice assembling the pistons and cylinder to acquire a sense for
the feel of the fit without the other piston in place. With the instrument inverted,
unscrew the knurled knob and move the top pressure plate ninety degrees releasing the
lever arms and the bottom pressure plate. Insert the piston into the cylinder with the red
marking aligned to the red dot on the block and the diamond anvil up. Rotating the piston
slightly while inserting it into the cylinder will ease the procedure. Remove the piston
from the block and insert the second piston with the dots aligned and the diamond anvil
down. Repeat this exercise to gain experience with the feel of the fit.
- GASKET PREPARATION:
A pre-indented gasket is recommended prior to making the
sample chamber hole. To indent a gasket, align the red dot on the piston with the red dot
on the block, then insert the piston into the cylinder. Support the gasket with small
balls of paraffin or wax on the anvil. Make alignment markings on the gasket with wax or
nail polish for future reference. Insert the other piston with dots aligned and
immediately fit the bottom pressure plate over the piston and the knurled knob with the
top pressure plate over the lever arms. Indent the gasket to half its thickness by turning
the knurled knob. Several attempts may be needed before obtaining a satisfactory result.
Be sure to align the marking you just made on the gasket to the piston before indenting
the gasket. Drill a sample chamber hole as close to the center of the indentation as
possible. Remove any rough edges (burrs) around the hole with a micro drill bit.
- SAMPLE PREPARATION:
Cut soft samples into small pieces (e.g. 50 microns die). Harder
samples may be polished with fine grit sandpaper and reduced by using a sharpened needle.
- LOADING SAMPLE:
Clean the diamond anvils with paper tissue. With the instrument inverted and bottom
pressure plate disconnected, align the red dot on the piston with the red dot on the block
when inserting the piston. Position the gasket on the anvil with balls of paraffin, noting
previous alignment markings. While viewing under magnification, level the lower support,
load the sample, load the pressure calibrant (e.g. ruby chips) and pressure-transmitting
medium. Several attempts may be needed when performing this step. Immediately insert the
other piston with dots aligned to seal the sample chamber. Fit the bottom pressure plate
over the piston and fit the knurled knob with the top pressure plate over the lever arms.
Tighten the knurled knob until a moderate pressure is applied to the gasket. This
procedure is needed to ensure the pressure-transmitting medium has been successfully
- OBSERVE THE CHAMBER HOLE:
Under pressure, the hole will change shape slightly. However, if the hole is significantly
deformed, the instrument may have lost the pressure medium. If medium loss is uncertain,
apply more pressure by tightening the knurled knob and observing the sample hole for any
changes. Begin the process from step 1 if the pressure medium has been lost. Otherwise,
proceed to step 7.
- PRESSURE CALIBRATION:
Ruby fluorescence can be used to calibrate the in-situ pressure. The
frequency shifts of the R1 and R2 lines determine the
pressure by using the following formula:
Where Δλ and λ0 are the wavelength (in nm)
change under pressure and the wavelength at ambient pressure respectively.
Lower case letter b is a parameter, would be 5 or 7.665 corresponds to
non-hydrostatic or quasi-hydrostatic pressure respectively. Light sources
using an argon ion laser from 488 nm and 514.5 nm lines are commonly used in
- Record the current pressure and begin experiments.
- ALTERING PRESSURE:
The pressure can be repeatedly altered by tightening or
loosening the knurled knob slowly. CAUTION: Releasing the pressure abruptly may cause
- Calibrate the pressure according to step 7, then continue
- To disassemble the diamond anvil cell, invert it and
slowly turn the knurled knob. Insert a tool, such as the bent paper clip provided, through
both holes in the lower piston to push out the other piston. Using a tool to remove the
pistons prevents abrasion of the anvils.
- Disassemble and store the instrument as instructed.
Copyright © 2008 by High Pressure Diamond Optics, Inc.
Last updated: August 12, 2008