Development of a Mechanically Pumped Two-Phase CO2 Cooling Loop for the AMS-2 Tracker Experiment

Abstract

The Alpha Magnetic Spectrometer AMS-2 is planned for a five years mission as attached payload on ISS, the International Space Station. It is an international experiment searching for anti-matter, dark matter, and missing matter. AMS-2, an improved version of AMS-1 flown on STS 91, consists of various particle detector systems, one of these being the (Silicon) Tracker. The trade-off based choice and the experimental feasibility demonstration of a mechanically pumped two-phase CO 2 cooling loop for the Tracker is discussed in detail. The current status and ongoing and planned development activities are discussed.

Experimental investigation on startup of a novel two-phase cooling loop

“…Considering the issues about designing and testing MPCL for future space missions, an experimental setup is constructed according to the model proposed by National Aerospace Laboratory (NLR) in the Netherlands [12,13]. The design of such a system had to consider the particular characteristics related to its applications and restrictions, as well as the use of an alternative working fluid.…”

“…For instance, the start-up of LHP is often a complicated task, and it is needed to take into account a lot of factors, such as the initial states of the working fluid across the primary wick in the evaporator, the elements geometry structure, and the ambient conditions of the system [6][7][8][9][10][11]. As a novel cooling technology, the mechanically pumped two-phase cooling loop has shown much predomination characteristics and been designed for many years [12,13], however, it is lack of reports on the experimental investigation about this system in public paper, especially for the study on the processes of startup. In this study, the experiments on the startup processes under variety of conditions are carried out to reveal the behaviors of startup of MPCL in different evaporative temperatures, variable mass flow or heating load and some abnormal startup prehistory.…”

Thermal Modeling Issues Concerning the Mechanically Pumped Two-Phase CO2 Cooling for the AMS-2 Tracker

“…Together with the existing complicated three-dimensional configuration, the severity of the specifications require the power dissipated in the Tracker (approximately 200 W) to be removed by means of an active mechanically pumped two-phase loop. The rationale behind the choice for this system is given in [2,3]. It is based on NLR's experience with two-phase heat transfer using several working fluids in various types of applications, e.g.…”

“…The pump characteristics of available space qualified pumps demand low system pressure drops. This is the main reason that carbon dioxide is chosen as the working fluid [2,3].…”

New Monitoring Interface for the AMS Experiment

“…The final push came in 2019. In the latter half of 2014, the old pumps on the mechanically pumped two-phase CO2 cooling loop [3], which circulated coolant to the Silicon Tracker, reached their designed lifetime. In order to prolong the lifetime of the AMS experiment, an upgraded cooling system known as the Upgraded Tracker Thermal Pump System (UTTPS) was designed, manufactured, tested, space qualified, and deployed to the ISS in November 2019.…”