Procedures for Making the Standard 7/2 Cell Assembly in T-Cup or T-25

This manual is intended to provide information on how to put together a cell assembly for multianvil experiments using 7 mm octahedral pressure medium and 2 mm edge length truncation on the WC cubes. Although most of the pictures were taken from the T-Cup, or T-10, where 10 mm WC anvils are used, the same assembly can also be used for the T-25, where 25 mm anvils are used.

Figure below shows the cell assembly. The three brown parts in the middle represent the sample capsule. This is due to machining difficulties using boron epoxy (BE) as pressure medium. In certain cases a single piece made of MgO will be used. BE capsules are amorphous and therefore do not contaminate sample diffraction patterns. It is used for samples with weak scattering power. For samples with strong scattering power, MgO can be used. MgO capsules are much easier to handle.

Figure 1. Exploded view of the cell assembly.

Step 1. Prepare for parts

This step can be done well before the start of making the cell.

1.1 Gather all the parts needed. The “octahedron” is made of several independent pieces of various materials. These pieces are available at the sample preparation area. In order to use them, you should contact Uchi or Yanbin first and they will give you the correct parts for your experiments.

1.2 Bend the four Mo strips so that each of them has a small 90 degree bend. This is achieved by pressing the Mo under a razor blade, with only about 0.3 mm sticking out under the blade. Put another blade under the exposed Mo and bend it upwards. The width of the bend should be no longer then 0.2 mm.

1.3 Glue the LaCrO3 thermal insulating disk onto the trapezoidal MgO wedge using the 5 min epoxy resin.

1.3.1 Squeeze equal portions of parts A and B from the epoxy tube onto a piece of weighing paper. Use a tooth pick to mix the two parts THUROUGHLY until the mixture turns into a homogeneous milky white color with a thick paste like consistency. Use a probe and pick a tiny drop of mix and put it in the corner of the MgO wedge. Put four tiny drops on four corners and glue the LaCrO3 disk onto the MgO wedge. Always use ad little as glue as possible!!

1.3.2 Centering of this piece relative to the MgO is very important, as later the TiC/diamond disk will be glued right onto the insulator, which determines the centering the sample capsule.

1.4 Repeat the steps in 1.3 to glue the other LaCrO3 disk to the second MgO wedge.

1.5 Glue the Mo strips onto the MgO wedges. The small bend should be in contact of the LaCrO3. Use only one small drop of 5-min epoxy at the center of the MgO wedge. See step 1.3.1 for mixing the epoxy.

1.6 Repeat step 1.5 to glue the second Mo strip onto the same MgO wedge.

1.7 Repeat steps 1.5 and 1.6 to glue two Mo strips onto the second MgO wedge.

1.8 Prepare the thermocouple.

1.9 Prepare cubes: All WC cubes must be cleaned!

1.9.1 Glue pyrophyllite gaskets: There are two types of pieces of gaskets. The trapezoidal shaped (wedges) and cube shaped.

1.9.1.1 Glue one wedge one each of the eight cubes. Tips: This is done by pushing the 10 mm cube against two other cubes, which form a right angle corner. The wedge gasket should be in contact with both large cubes. Use super glue for this: pick a tiny drop of glue with a probe and put it on the wedge at a location that is farther away from the cell.

Figure 2. Define the corner for mounting the wedge gasket.

Figure 3. Glue the gasket with a tiny drop of super glue.

1.9.1.2 Glue an additional wedge on two of the eight cubes. Tips: use two cubes that already have one wedge glued on them. Put them against one face of a larger cube. Turn the second cube so that the wedge is facing up. The wedge on the first cube touching the second cube. This will form a half “cage”. Put a white spacer (an octahedral cap whose shape and dimensions are identical to those of MgO caps) into the cage. Glue a “cube” gasket right on top of the wedge that touches both WC cubes. Now the second wedge can be pushed all the way against the white cap and the “cube” gasket. This will ensure the location of the second wedge gasket. Note: the “cube” gasket is NOT a perfect cube. So its orientation is important. The thickness is 2.36 mm and the width is 2.16 mm. The 2.16 mm width should be mating with the slanted side of the wedge gasket and the 2.36 mm thickness should match the thickness of the wedge gasket measured from the cube surface and up.

Figure 4. Use two anvils (each with a wedge already mounted) and the white spacer to define locations for the cube gasket. Glue the cube to the wedge that is in between the two anvils. Now the location of the second wedge gasket is fixed.

1.9.1.3 Glue “cube” gaskets on two of the cubes that have only one wedge. See tricks shown in Figure 4.

1.9.1.4 Glue wood spacers. On each cube, glue a wood spacer on each face that has a wedge gasket. The spacer should be located at the opposite corner from the wedge, but not too close to the corner (allow space for thermocouple wires).

Figure 6. A finished set of eight cubes with gaskets and balsa wood spacers mounted. Note that two cubes have three pieces

1.10 Prepare mica insulation sheets. These sheets are about 150 microns thick.

1.10.1 Cut six (6) pieces of mica, each about 22 mm square. Cut two slots in each two of the six squares. See figure for the locations of the slots.

1.10.2 Insert a piece of copper electrical contact into each slot. These copper pieces are 50 microns thick. Use a tiny drop of super glue between the copper and mica. The viscosity of the glue is low so is should not form a thick layer between the mica and the copper.

Step 2. Loading the Sample

Step 3. Assemble the cell in the T-Cup

Follow the sequence below to complete the assembly in the bottom T-Cup nest:

Last updated Jan 28, 2002 by Yanbin Wang