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

Abstract

Abstract. 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. IntroductionThe Cryomech PT410 and PT415 pulse tube coolers are used for cooling superconducting magnets and other applications [1]. These coolers are also the central element in the small helium liquefiers produced by the company for universities and other institutions that require liquid helium for research and product development [2]. Most of the uses for these coolers involve the re-condensation of liquid helium using a thermal-siphon cooling-loop or in a liquid helium tank [3], [4]. When a cooler is used for helium re-condensation, the cooler second stage performance 4.2 K is often all that is needed. When something goes wrong with a magnet cryostat or magnet cooling system, more knowledge about the cooler performance is needed to determine what went wrong [5], [6]. Using a cooler to cooldown a cryostat requires knowledge of the cooler performance over a wide temperature range [7].Cooler operating data over a range of temperatures on both stages is critical for understanding how a device is cooled-down using these coolers. Two-stage coolers may also be used for cooling at higher temperatures (say up to 28 K) to cool MgB 2 magnets [8]. These coolers can also be used for the hydrogen liquefaction and hydrogen re-condensation after liquefaction [9], [10]. For these reasons, it is important to understand how these coolers behave as a function of 1 st and 2 nd stage temperatures.

Methods of speeding up the cool-down of superconducting magnets that are cooled using Small coolers at temperatures below 30 K

“…Each coil is cooleddown and cooled with three Cryomech PT415-RM pulse tube coolers [14]. These three coolers cooldown 1240 kg of cold mass, liquefy 12 L of helium gas and keep the coils at ~4 K. At 4.2 K, PT415-RM coolers with remote motors produce ninety percent of the cooling of three standard PT415 coolers [15]. Two of the three coolers are adequate to keep the magnet coils at 4.5 to 4.6 K, once the cryostat has been filled with liquid helium [16].…”

Thermoeconomic cost optimization of superconducting magnets for proton therapy gantries

“…The first cryocooler model (so-called High Temperature (HT) cryocooler) has a load curve (Q ˙ cap (T i )) interpolated from a commercial single-stage cryocooler with a quiescent no-load temperature of 12.6 K. The second cryocooler model (so-called Low Temperature (LT) cryocooler) implements the load curve fit in Ref. [15] for a PT415 with an unloaded first stage (i.e., providing cooling only at a single temperature). The curve fit for both cryocoolers cooling capacity is shown in Eq.…”

“…To allow a continuous parameterization of operating temperature, two synthetic cryocoolers are considered with properties inspired from industry. The first cryocooler model (so-called High Temperature (HT) cryocooler) has a load curve ( Qcap (T i )) interpolated from a commercial single-stage cryocooler with a quiescent no-load temperature of 12.6 K. The second cryocooler model (so-called Low Temperature (LT) cryocooler) implements the load curve fit in reference [15] for a PT415 with an unloaded first stage (i.e. providing cooling only at a single temperature).…”

Design and characterization of the POLARBEAR-2b and POLARBEAR-2c cosmic microwave background cryogenic receivers

“…Measurement of the load curve of a PT415 first stage is more difficult but less variable from unit-to-unit, and has been done to high temperatures. 8 Generally, minimizing loading between stages is crucial for basic functionality of the cryostat, while precise optimization of the cryogenics is critically important for creating a high duty cycle receiver with minimal complications in readout and biasing of the detectors. The lowest temperature reached by each stage of the PTC is referred to as the base temperature, which is a balance of the PTC cooling capacity and the parasitic loading.…”