The refrigeration system of the Hot Universe Baryon Surveyor (HUBS) mission intends to use the FAA paramagnetic salt adiabatic demagnetization refrigerator (ADR) to obtain temperatures below 100 mK. In order to obtain the 1 K pre-cooling temperature required by the FAA stage, one option is to use a GGG paramagnetic salt ADR, and the other option is to use a helium sorption cooler. A helium sorption cooler and the corresponding helium gas gap heat switch have been developed, and a cooling temperature of 800 mK has been obtained. This paper gives a detailed introduction to the prototype's structure, cooling performance, existing problems, and the next optimization measures.
The Hot Universe Baryon Surveyor (HUBS) mission requires a refrigeration system with temperatures below 100 mK to meet the high-resolution detection requirements of its superconducting transition edge sensor. The refrigeration scheme is to use a 4 K mechanical cryocooler as the pre-cooling stage and then use adiabatic demagnetization refrigerators (ADR) to obtain mK temperatures. One option for the pre-cooling stage is to use a pulse tube cryocooler. At present, a thermalcoupled and gas-coupled composite prototype based on helium-4 as the working gas has been successfully developed, a no-load temperature of 3.1 K, and a maximum cooling capacity of 22.0 mW at 4.2 K has been obtained, which can barely meet the demand. The calculation results show that the use of helium-3 instead of helium-4 as the working gas of the gas-coupled second and third stage is expected to further increase the cooling capacity to 53.1mW/4.2K, but 53 standard liters of helium-3 needs to be charged at room temperature. In order to reduce the amount of helium-3, a thermal-coupled three-stage pulse tube cryocooler is further designed. When the first and second compressors and their cold fingers use helium-4, while the third compressor and its cold finger use helium-3 as the working gas, the calculation results show that a cooling capacity of 57.5 mW/4.2 K can be obtained, and the amount of helium-3 that needs to be charged at room temperature is 11 standard liters, which effectively reduces the cost.
Transition Edge Sensor (TES) is a key component for Hot Universe Baryon Survey (HUBS), which is proposed in China to address the so-called “missing baryon problem”. A stable heat sink below 100 mK is needed for the detector’s noise suppression and high resolution. Since HUBS is a satellite based observation mission, a complicated cooling system suitable for space application becomes an important supporting sub-system. A compounded cooling system, including a mechanical cryocooler and an adiabatic magnetization refrigerator (ADR), has been proposed for HUBS. The mechanical cryocooler is used as the pre-cooling 4 K stage, and the ADR is responsible for further reducing the temperature to below 100 mK. High-frequency pulse tube cryocooler (HPTC) and HPTC combined with Joule Thompson cooler (J-T) are two candidates for the mechanical pre-cooling stage, both of which are currently under development. The ADR is being designed and processed. In this paper, we will present the preliminary architecture of the HUBS cooling system, as well as the latest states of HPTC, J-T, and ADR.
The high-resolution X-ray imaging spectrometer of the Hot Universe Baryon Surveyor (HUBS) mission is based on the superconducting transition edge sensor (TES) technology. A TES serves as a thermometer for sensing the temperature change of a microcalorimeter to measure the energy of incident X-rays. In order to achieve high sensitivity, TES needs to operate at temperatures below 100 mK. A combination of a 4 K pre-cooling system and a sub-K cooling system is required to achieve such a low temperature. In this paper, it is proposed to directly obtain the 4 K temperature by a high frequency pulse tube cryocooler (HPTC) for HUBS. The advantages of this technology is compact structure and high reliability, compared with other technologies (for instance, multi-stage Stirling cryocoolers + Joule-Thompson cooler). We have constructed a multi-stage HPTC. The test cooling performance, as well as the design of the cryocooler, existing challenges and proposed solutions will be presented.
The Hot Universe Baryon Surveyor (HUBS) mission is proposed to study “missing” baryons in the universe. Unlike dark matter, baryonic matter is made of elements in the periodic table, and can be directly observed through the electromagnetic signals that it produces. Stars contain only a tiny fraction of the baryonic matter known to be present in the universe. Additional baryons are found to be in diffuse (gaseous) form, in or between galaxies, but a significant fraction has not yet been seen. The latter (“missing” baryons) are thought to be hiding in low-density warm-hot ionized medium (WHIM), based on results from theoretical studies and recent observations, and be distributed in the vicinity of galaxies (i.e., circumgalactic medium) and between galaxies (i.e., intergalactic medium). Such gas would radiate mainly in the soft X-ray band and the emission would be very weak, due to its very low density. HUBS is optimized to detect the X-ray emission from the hot baryons in the circumgalactic medium, and thus fill a void in observational astronomy. The goal is not only to detect the “missing” baryons, but to characterize their physical and chemical properties, as well as to measure their spatial distribution. The results would establish the boundary conditions for understanding galaxy evolution. Though highly challenging, detecting “missing” baryons in the intergalactic medium could be attempted, perhaps in the outskirts of galaxy clusters, and could shed significant light on the large-scale structures of the universe. The current design of HUBS will be presented, along with the status of technology development.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.