| 摘要 |
<p>A cooling apparatus utilizing liquid nitrogen for cooling specimens to temperatures in the range from -100 DEG C. to -195 DEG C. in propane, halogenated hydrocarbons, isopentane, or other cooling media. Freezing of the cooling media is avoided by means of an arrangement wherein the liquid nitrogen cools the cooling-bath container and/or the liquifier only initially, but after the desired cooling-bath temperature has been reached, the liquid nitrogen level is lowered to below the height of a protective shell which results in further cooling being only indirect, via solid/solid contacts and via the gas phase. A constant cooling-bath temperature is ensured by means of a thermostatic temperature-control system while trouble-free standby operation is ensured by means of an automatic system for replenishing liquid nitrogen, and by a system for controlling the level of liquid nitrogen. Safe disposal of the cooling media which may be combustible and/or toxic is provided for.</p> |
