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Download 1070-150 Rev. B5 PQ
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Chapter 1 Introduction and System Setup Section 1.4 Safety Precautions WARNING! If a dewar ruptures or cryogenic materials spill, vent the room immediately and evacuate all personnel. Only perform cryogen transfers when you are in a well-ventilated room. Cryogens expand to hundreds of times their liquid volume when they boil, which occurs well below room temperature. A relatively small volume of liquid nitrogen or helium can displace all the air in a room during a spill. Nitrogen and helium are colorless and odorless, and the only symptoms of insufficient oxygen are dizziness and unconsciousness, followed by death. 1.4.2 Magnets WARNING! All magnet-safety precautions must take into account the strong threedimensional fields produced by the superconducting magnets. People wearing a pacemaker or other electrical medical device must stay at least 16.5 ft. (5 m)2 from the PPMS dewar. Ferromagnetic objects must be kept at least 16.5 ft. (5 m) from the PPMS dewar. Magnetic fields must be at zero (0) before you disconnect the magnet controller from the probe head. Helium levels must be at least 60% to use a magnet to full field. Never disconnect a charged magnet from the magnet control electronics (Model 6700 or Model 3120), and never disconnect any other system connections while a magnet is charged. The superconducting PPMS magnets can trap magnetic flux, so it would be possible to leave a charged magnet that is completely disconnected from the rest of the system. Under such circumstances, you have no means to discharge the magnet directly. Several different cables have connections for magnet control. In the event that you must disconnect the probe from the magnet controller, verify that the magnet has been driven to zero field before you disconnect any cables, with the exception of the sample-chamber connection. The sample chamber connection⎯that is, the cable from the gray Lemo connector that is on the PPMS probe head⎯is the only cable that you can safely disconnect while the magnet is charged. You must leave all other connections intact. The safety guidelines given here are generalized to a 9-T longitudinal magnet. Verify that any person wearing a pacemaker or other electrical or mechanical medical device stays at least 16.5 ft. (5 m) from the PPMS dewar. This distance applies to people located in adjacent rooms and on floors above and below the equipment, because the magnets produce three2 At the current time (August 2004), 5 m should be a large enough distance to protect wearers of metallic implants or medical devices from most magnetic fields produced by Quantum Design magnets. However, the safe distance from newer magnets (in development) could be greater. Hence, personnel who work with and around the superconducting magnets should review thoroughly documentation for new equipment. Quantum Design PPMS Hardware Manual, 1070-150, Rev. B5 February 2008 1-5
