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P-Series

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 each use.

 

Specifications:

Length:  12.5 cm.
Base Height: 2.5 cm.
Width: 7.5 cm.
Total Height: 9cm.
Weight: approx. 1 kg.

P-Series diagram

 

 

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 materials.

 

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.

 

HIGH PRESSURE STUDIES

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

  1. Clean the two diamond anvils as instructed above.
  2. 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.
  3. 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.
  4. 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.
  5. 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 loaded.
  6. 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.
  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 this technique.
  8. Record the current pressure and begin experiments.
  9. ALTERING PRESSURE:
    The
    pressure can be repeatedly altered by tightening or loosening the knurled knob slowly. CAUTION: Releasing the pressure abruptly may cause sample failure.
  10. Calibrate the pressure according to step 7, then continue experiments.
  11. 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.
  12. Disassemble and store the instrument as instructed.

 

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Copyright 2008 by High Pressure Diamond Optics, Inc.
Last updated: August 12, 2008