IKZ has joined the international Einstein Telescope collaboration
Growing particularly large silicon crystals will support the construction of a gravitational wave observatory
The Einstein Telescope (ET) is a planned next-generation gravitational wave observatory in Europe, designed to detect and study gravitational waves with unprecedented sensitivity. It will use a network of underground laser interferometers to explore cosmic events such as black hole mergers and neutron star collisions, enhancing our understanding of the universe. The interferometers operating at cryogenic temperatures rely on crystalline silicon for the test mass mirrors and suspension system.
Silicon crystal growth using the Float-Zone (FZ) method is a long-standing expertise at the IKZ. The crucible-free FZ technique stands out for its ability to produce silicon crystals of ultra-high purity and crystalline perfection. In the semiconductor industry, the FZ method is used to manufacture substrates for high-power devices critical for energy conversion, including applications in e-mobility and renewable energy. For ET mirrors, FZ silicon would offer excellent optical quality and low absorption due to its high purity and lack of structural defects, such as dislocations. However, the FZ method currently cannot achieve the dimensions required for ET mirrors. The largest FZ crystal diameter that can be achieved nowadays is 200 mm.
For growth of large silicon crystals, the IKZ laboratory features a state-of-the-art FZ crystal puller PVA-TePla FZ30M, a 2.8 € million investment made in 2020. Silicon crystals with a large diameter of 150 mm and ultra-high purity (specific electrical resistivity > 10 kΩ×cm) were delivered for test mass mirrors to ET-Pathfinder, which is a R&D infrastructure for testing and prototyping innovative concepts and enabling technologies for the Einstein Telescope.
In the future, IKZ aims to further support the development of silicon mirror material in collaboration with partners from industry and academia, such as the newly established German Center for Astrophysics (DZA).
For the ET mirror suspension system, thin and long silicon fibers with a diameter of about 3 mm are required. As part of the BMBF joint research project 3G-GWD, a crystal growth setup was developed at IKZ to enable the stable production of such monocrystalline silicon fibers. Using the FZ method and a similar approach known as the Pedestal method, silicon fibers with a uniform diameter of 3 mm and lengths of up to 1 m were successfully grown. These fibers were supplied to ET Pathfinder, the University of Glasgow, and the University of Camerino for tests on mechanical strength and material characterization.
Contact:
Leibniz-Institut für Kristallzüchtung (IKZ)
Dr.-Ing. Robert Menzel
+49 30 246-499-404
robert.menzel(at)ikz-berlin.de
www.ikz-berlin.de
Press release IKZ, 12 December 2024