The Caltech Paleomagnetics/Biomagnetics clean lab facilities are housed in four rooms in the sub-basement of the Charles Arms building on the Caltech campus. Two of these rooms are large-volume, magnetically-shielded environments, one dedicated for general paleomagnetic measurements and the other for biomagnetic and rock magnetic measurements. A third room is a general-purpose, wet chemical lab with primitive facilities for DNA sequencing and tissue culture research. The fourth room houses the main computing equipment for the group, a dark room and student desks. Professor Joseph Kirschvink is in charge of the Paleomagnetics/Biomagnetics Laboratories. The facilities within each of these labs are discussed further below:
Modifications in Progress
Automatic Sample Changer
The magnetic shielding in this lab is accomplished with two layers of mu-metal, forming a cubic inner room of approximately six feet per side with residual fields ranging from 100 to less than 5 nanotesla. Housed in the center of this shielded environment is a two-axis Superconducting Technology, Inc. cryogenic moment magnetometer with a background noise sensitivity of 5 x 10-12 Am2 per axis.
The system has been upgraded with a 2G Enterprises 60-liter, cryocooled dewar and electronics and a computer- controlled sample moving system performs the actual measurements. We have interfaced a 2G/Applied Physics alternating-field demagnetization unit to the system so that it can now perform progressive, three-axis, alternating-field demagnetization experiments automatically up to peak fields of 80 mT. A magnetically shielded furnace is built into the room, permitting up to 100 paleomagnetic specimens to be thermally demagnetized at once with a cycle time of one hour. Also, a new, custom-designed oven permits Thellier experiments for more precise determinations of paleo-intensity.
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This 9m x 3m x 3m room is shielded with six tons of transformer steel to produce residual magnetic fields over most of the volume of 200 mT and less. The room is an epoxy-sealed dust and particle-free clean laboratory maintained under positive pressure with a deionized water shower entryway and includes a fume hood and distilled-water sink. A 2G Enterprises pass-through superconducting rock magnetometer is housed within this facility, mounted on a swivel-support which allows it to operate either in a vertical or horizontal mode. This system is integrated with a computer-controlled pulse magnetizer, an ARM acquisition system, a stepping motor system, and the 2G/Applied Physics alternating field demagnetization unit. The total setup thereby allows a complete IRM acquisition and alternating field cycle (30 measurements) to be performed automatically in about 20 minutes, and with the ARM facility, a complete Lowrie Fuller ARM test requires about 45 minutes.Other equipment in Pr! ! ofessor Kirschvink's paleomagnetics/biomagnetics lab include Hall probes, fluxgates, Susceptibility bridges, optical microscopes, and DNA sequencing equipment.
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The controlling hardware and software for the paleomagnetic magnetometer is currently being upgraded to improve the system's performance, flexibility, and user interface. The next generation controlling software, being written in Microsoft VisualBasic, operates in a Microsoft Windows environment. This will allow the user to perform other computational tasks, such as data analysis, while performing routine sample measurements. All controlling hardware is now external to and independent of the computer which runs the software, providing flexibility to replace or modify the controlling computer without requiring software changes or installation of specialized internal components. This new system will also allow immediate data access from networked computers.
But the big news is the AUTOMATIC SAMPLE CHANGER!!!
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