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Published May 3, 2008 | public
Journal Article Open

Rapid, Precise, and High-Sensitivity Acquisition of Paleomagnetic and Rock-Magnetic Data: Development of a Low-Noise Automatic Sample Changing System for Superconducting Rock Magnetometers


Among Earth sciences, paleomagnetism is particularly linked to the statistics of large sample sets as a matter of historical development and logistical necessity. Because the geomagnetic field varies over timescales relevant to sedimentary deposition and igneous intrusion, while the fidelity of recorded magnetization is modulated by original properties of rock units and by alteration histories, "ideal" paleomagnetic results measure remanent magnetizations of hundreds of samples at dozens of progressive demagnetization levels, accompanied by tests of magnetic composition on representative sister specimens. We present an inexpensive, open source system for automating paleomagnetic and rock magnetic measurements. Using vacuum pick-and-place technology and a quartz-glass sample holder, the system can in one hour measure remanent magnetizations, as weak as a few pAm2, of ~30 specimens in two vertical orientations with measurement errors comparable to those of the best manual systems. The system reduces the number of manual manipulations required per specimen ~8 fold.

Additional Information

Copyright 2008 by the American Geophysical Union. Received 12 October 2007; accepted 19 February 2008; published 2 May 2008. This paper is dedicated to the memory of William S. Goree (1935–2007), who revolutionized the field of paleomagnetism by developing and commercializing superconducting moment magnetometers for geophysical use. The refinement of the sample changer has been supported by a continent-wide consortium of faculty, consisting of Scott Bogue (Occidental College), David Evans (Yale), and Benjamin Weiss (MIT). Numerous students in, and visitors to, the Caltech lab helped debug the system. Victor Nenow gave much advice on earlier versions of the controlling electronics, and Ricardo Paniagua of the Caltech Physics shop solved the problem of mass-producing the plastic cups for the snake chain. Former students Gaylon Lovelace, Hiroshi Iishi, Bryce Engelbrecht, Theresa Raub, and Isaac Hilburn played key roles in constructing the early versions of the sample changer and software at Caltech and modern incarnations at Yale and MIT. Research support over the past 25 years from the NSF, NASA, NIH, the Agouron Institute, and the Caltech SURF program made these developments possible. We thank Joshua Feinberg and Craig Jones for insightful reviews.



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