CERN Accélérateur de science

Report number	AIDAinnova-CONF-2024-004
Title	Hybrid cycle with Krypton for cooling of future silicon detectors in HEP
Author(s)	Contiero, Luca (Norwegian University of Science and Technology (NTNU) (NO)) ; Hafner, Armin (Norwegian University of Science and Technology (NTNU) (NO)) ; Banasiak, Krzysztof (Norwegian University of Science and Technology (NTNU) (NO)) ; Barroca, Pierre Andre (CERN) ; Allouche, Yosr (Norwegian University of Science and Technology (NTNU) (NO)) ; Verlaat, Bart (CERN) ; Petagna, Paolo (CERN)
Publication	2022
Imprint	2022-06-10
Study	AIDAinnova
Project	WP10: Advanced Mechanics for Tracking and Vertex Detectors
Keywords	krypton ; cooling ; ejector ; detector
Abstract	The Large Hadron Collider (LHC) will soon deliver much more radiation after LS4. The level of radiation has already pushed the current CO2 cooling unit to its limit, represented by the triple point (≈ -56°C). To sustain the harsh requirements imposed in terms of radiation, temperature levels, and mass minimization, the sensors should be maintained at a temperature sufficiently low to prevent thermal runaway, while at the same time the heat load generated inside the readout electronics and sensor must be removed. The refrigerant Krypton stands out as the most promising coolant thanks to its superior thermal performance with smaller cooling pipes inside the detector and its high resistance to radiation, being a noble gas. As a side effect of reaching temperature levels unattainable by CO2, higher radiation length is expected due to the larger atomic number and lower liquid-vapor density ratio. Besides investigating the work done so far on thermal management design aimed at reducing the temperature difference between sensor and coolant, it is crucial to ensure a stable and controlled cooling rate without shocking the detector. Krypton, being a high-working-pressure fluid, is able to efficiently remove the heat generated inside the detector via the use of small tubes, with less impact in terms of space compared to other low-temperature working fluids. The same silicon sensor technology currently used with two-phase CO2 flowing in titanium tubes located close to the heat source (electronics and sensors) will be adopted. A much lower critical and NBP temperature compared to CO2 requires a completely new cooling cycle. In fact, the vapor phase at room temperature imposes a gentle supercritical cool-down process to avoid shocking the detector. A special cycle technology is also needed to work either in subcritical or supercritical state, covering a very large temperature range. A specific control logic must be implemented to gently cool down the detector while maintaining an acceptable temperature gradient along the detector. Different components are activated according to the operating conditions in terms of the working envelope (either subcritical or supercritical), as well as the temperature levels.
Submitted by	camila.pedano@cern.ch