Second stage cooling from a Cryomech PT415 cooler at second stage temperatures up to 300 K with cooling on the first-stage from 0 to 250 W

The amount of cooling delivered to the second stage of a two stage cooler is dependent on the second stage temperature and the amount of refrigeration provided by the cooler first stage. The second stage cooling as a function of temperature for a Cryomech PT-415 cooler (1.5 W at 4.2 K with 42 W on the first stage) has been estimated by scaling similar data that was measured for a Cryomech PT-410 cooler (1.0 W at 4.2 K with 28 to 30 W on the first stage). In order to accurately calculate the cool-down time for a superconducting magnet using PT-415 K coolers one must know how much cooling can be delivered by the cooler second-stage as a function of the second-stage temperature and the added cooling delivered to the cooler first-stage. There are applications where PT415 coolers are used in the temperature range from 15 to 25 K to liquefy hydrogen or cool magnets fabricated from MgB 2 . This report describes the method for estimating the cooler performance for a PT415 cooler as well as the results of the measurements on several PT415 coolers.