Evaporation Hearth and Metal Charges

Each of the evaporators contains a rotating, water cooled hearth with four pockets. A knob on the control pannel selects the pocket which is active. The knob can be turned to any one of the four pockets in either direction, but there is about a 10 second delay between when the knob is changed and the hearth actually rotates. The hearth only rotates in one direction.

Certain pockets are reserved for certain metals. Other pockets are multi-use. In general, the pockets are labeled with the acceptable charge materials. If you are unsure which pocket to use, contact the module lead or the MCR staff.

Figure 15: Ebeam-1 Hearth Rotation Control. Positions 5 and 6 are unused. Note the pocket contents labels.

Figure 16: Ebeam-2 Hearth Rotation Control.

Certain metals (Titanium and Aluminum, for example) can be placed directly into one of the pockets in the hearth. Other metals (Gold, and silicon, for example) should first be placed in a crucible (made of molybdenum, tungsten, alumina, or graphite depending on the charge material).

Figure 17: Ebeam-1 Hearth. A chromium charge has been placed directly in the hearth pocket.

Figure 18: Ebeam-2 Hearth. A chrmomium charge has been placed directly in the hearth pocket.

When loading charges into the hearth (either directly into the pockets or in a crucible), care should be taken to ensure that the pockets are loaded with enough charge but not overloaded. If a pocket is overloaded, the charge may jam in the rotation mechanism. If the pocket is not loaded with enough of a charge, the electron beam will evaporate the crucible or the hearth itself causing damage.