Last week, the Planck space mission released the most accurate and detailed map ever made of the oldest light in the universe, revealing new information about its age, contents and origins.
Materials produced by Ames Laboratoryâ€™s Materials Preparation Center are integral to the Planck mission that was launched into space on May 2009. The MPC synthesized over 20 kilograms of a lanthanum-nickel-tin alloy for use in a metallic hydride sorption cryocooler system built by NASAâ€™s Jet Propulsion Laboratory. The cryocooler is cooling instruments on the satellite.
The Planck satellite is collecting precise measurements of Cosmic Microwave Background, the remnants of radiation that filled the universe immediately after the big bang. Scientists will use the data to help answer questions about how the universe began, how it evolved and how it will continue to evolve.
The MPC not only cast the lanthanum-nickel-tin alloy for the Planck cryocooler systems, but it also produced the high-purity lanthanum and refined the nickel, all with the precision required to meet stringent purity and homogeneity specifications.
The project drew on a significant range of MPC skills: high-purity rare earths production, electron beam melting, arc casting, interstitial gas tests, electron-microprobe tests, metallography, rolling mill work and annealing furnaces.
Creating the materials was a big job. To ensure quality, MPC staff had to make the 20 kilograms in 50 gram batches, for a total of 400 batches. Casting large amounts of the alloy caused inhomogeneity within ingots, and gas-atomized particles proved very homogenous but didnâ€™t provide the needed performance, in this case. So small ingots were created in an arc melter, a type of furnace that melts metals with a 400-500 amp electronic arc through argon gas. The components of the alloy posed another challenge: their varied melting points required some special preparation of the materials.
â€œWe rolled the nickel and formed it into a dish-like shape. Then we put the tin and lanthanum in the nickel dish and heated the nickel from the edges,â€ says Trevor Riedemann, manager of the MPCâ€™s rare-earth materials division. â€œAs the nickel got hotter and hotter, the other two materials melted on the dish and created an intermediate intermetalic. From there, we melted the whole thing several times in the arc melter.â€
â€œThe project was a chance for everyone at the MPC to do some arc melting or to weigh materials while someone else ran the arc melter, so we could make as many ingots as possible,â€ Riedemann says. â€œIt was a great project because it fully engaged the MPC, and everyone had a role.