Lake Shore Cryotronics 1015, Руководство пользователя

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Lake Shore Model 1015 User’s Manual
Handling LHe & LN
2
B-1
APPENDIX B
HANDLING OF LIQUID HELIUM AND NITROGEN
B1.0 GENERAL
Liquid Helium (LHe) and liquid nitrogen (LN
2
) are often used in
association with the Model 201/208 Digital Thermometer. Although
not explosive, the following are safety considerations in the handling
of LHe and LN
2
.
B2.0 PROPERTIES
LHe and LN
2
are colorless, odorless, and tasteless gases. Gaseous
nitrogen makes up about 78% of the Earth’s atmosphere, while
helium comprises only about 5 ppm. Most helium is recovered from
natural gas deposits. Once collected and isolated, gases will liquefy
when properly cooled. Refer to Table B-1.
Table B-1. Comparison of Liquid Helium to Liquid Nitrogen
Property LHe LN
2
Boiling Point @1 atm, in °K
Thermal Conductivity (Gas), w/cm–°K
Latent Heat of Vaporization, Btu/liter
Liquid Density, pounds/liter 4.2
0.083
2.4
0.275 77
0.013
152
0.78
B3.0 HANDLING CRYOGENIC STORAGE DEWARS
All cryogenic containers (dewars) must be operated in accordance
with the manufacturer’s instructions. Safety instructions will also be
posted on the side of each dewar. Cryogenic dewars must be kept in
a well-ventilated place where they are protected from the weather
and away from any sources of heat.
B4.0 LIQUID HELIUM AND NITROGEN SAFETY PRECAUTIONS
Transferring LHe and LN
2
should be in accordance with the
manufacturer/supplier’s instructions. During the transfer, all safety
precautions written on the storage dewar and recommended by the
manufacturer must be followed.
WARNING: Liquid helium and liquid nitrogen are potential asphyxiants
and can cause rapid suffocation without warning. Store and use in area
with adequate ventilation. DO NOT vent container in confined spaces.
DO NOT enter confined spaces where gas may be present unless area
has been well ventilated. If inhaled, remove to fresh air. If not breathing,
give artificial respiration. If breathing is difficult, give oxygen. Get
medical help.