Lithium collection lens filling process for Fermilab antiproton source

The most critical step in fabrication of the lithium collection lens is the introduction of molten lithium into the core of the lens. A preload (hydrostatic compressive stress) of approximately 2500 psi is desired within the solid lithium for proper lens operation. Instrumentation that is accurate at temperatures well above the melting temperature of lithium (180.6 °C) must be used to monitor the pressure during the fill to achieve the desired preload. Measurements from recent lens fills show that as the lens cools, the preload decreases by approximately 50 psi/°C on average. This paper shows that this apparent thermal expansion modulus can be determined analytically as well as numerically. These results are then compared to measured values.