Cryostat for operation with liquid helium and method of operating the same
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing cryostat systems face limitations in achieving low temperatures efficiently, with flow cryostats restricted by base temperature and helium consumption, and bath cryostats experiencing slow cooldown times and large volumes due to large cryogen reservoirs.
Innovation Solution
A compact cryostat design featuring a primary chamber with a baffle structure acting as a pumpable heat exchanger and a '1K-pot' connected to an external helium Dewar, utilizing reduced helium-4 pressure and a continuous supply to maintain low temperatures, while minimizing helium consumption and enabling miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a flow cryostat is used to achieve compact size and constant temperatures, then the base temperature is limited and helium consumption efficiency is poor
Solution Approach 1:
The cryostat is divided into distinct functional regions: a flow cryostat section for compact cooling and a bath cryostat section for temperature stabilization. The flow section uses liquid helium flow through a cold finger for rapid cooling, while the bath section maintains a helium reservoir for stable base temperature and reduced evaporation losses.
Solution Approach 2:
The flow cryostat components are nested within the bath cryostat structure. The cold finger and flow channels are positioned within the helium bath environment, allowing the flow mechanism to operate inside the broader bath system, combining both approaches in a hierarchical arrangement.
2Temperature
If a bath cryostat is used to achieve low temperatures with large cryogen reservoirs, then the volume is large and cooldown time is slow
Solution Approach 1:
The flow cryostat section performs preliminary cooling action before the bath section takes over for final temperature stabilization. Liquid helium is first pumped through the cold finger to rapidly reduce the temperature of the sample and surrounding components, then the bath helium provides fine-tuned temperature control to reach and maintain the target base temperature.
Solution Approach 2:
The cooling process is segmented into two phases: rapid cooling via flow mechanism and stabilization via bath mechanism. This division allows the system to benefit from both the speed of flow cooling and the stability of bath cooling, achieving fast cooldown to low temperatures without requiring excessively large helium reservoirs.
3Temperature
If a bath cryostat is used to maintain low temperatures, then large reservoirs of cryogen are required increasing volume
Solution Approach 1:
Instead of uniformly distributing large helium reservoirs throughout the cryostat, the invention concentrates the bath helium in a localized region around the sample area. The flow channels deliver helium precisely where cooling is needed, allowing temperature control with minimal overall cryogen volume and compact device dimensions.
4Volume of moving object
If flow cryostat design is used to reduce volume, then base temperature accessibility is limited
Solution Approach 1:
The flow cryostat is nested within the bath cryostat structure, where the flow section handles rapid cooling and the bath section provides the helium reservoir necessary for reaching and stabilizing at lower base temperatures. This nested arrangement allows the compact flow design to benefit from the temperature-reaching capability of the bath system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves faster cooldown times and reduced helium consumption, allowing for compact and cost-effective operation at temperatures between 1.5 K to 1.8 K, enabling new cryogenic applications and simplifying manufacturing processes.
Implementation Method 1
the baffle structure defines at least one flowpath for the flow of gaseous helium-4, wherein each flowpath forms a detoured connection between the pot region and the main region
Implementation Method 2
configured for operation with a minimized bath of liquid helium-4, which can be maintained under reduced pressure, thereby reaching temperatures that are correspondingly lower
Implementation Method 3
gaseous helium-4 is pumped off through the outlet means by means of a pumping system connected to the cryostat's outlet means
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A cryostat for operation with liquid helium, comprises a primary chamber (2) with a main region (4) and a pot region (6) for containing a bath (8) of liquid helium-4, primary inlet means (12) for introducing liquid helium-4 and primary outlet means (14) for releasing gaseous helium-4, the primary inlet means comprising a transfer line (16) extending into the primary region. The cryostat is configured for operation under a continuous supply of liquid helium-4 and at a reduced helium-4 pressure, whereby gaseous helium-4 is pumped off through the outlet means. The primary chamber comprises a baffle structure (18) arranged between the pot region and the main region, the baffle structure defining at least one flowpath (20a, 20b) for the flow of gaseous helium-4, each flowpath forming a detoured connection between the pot region and the main region. A method for operating the cryostat comprises a cool-down phase followed by a stationary phase. In the cool-down phase, liquid helium-4 is supplied from an external reservoir through the primary inlet means into the pot region thereby evaporatingly cooling the latter until a bath of liquid helium-4 starts to accumulate on a bottom surface of the pot region. In the stationary phase, a bath temperature of liquid helium-4 is maintained by regulating the inlet flow of liquid helium-4 and/or regulating the rate of pumping off gaseous helium-4 through the primary outlet means, and optionally by controlled heating.