Dewar Cold Shield Assembly for Faster Cool-Down and Isolation
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Solution Overview
Problem
Traditional Dewar flask designs face challenges in balancing line-of-sight stability, thermal isolation, reduced cool-down times, and effective cold shielding due to increased mass and thermal/mechanical loads from larger sensing elements, as well as longer cold shields that prolong thermal equilibrium.
Innovation Solution
A Dewar apparatus featuring a focal plane array coupled to a carrier and a cold bridge, with a cold shield aligned with the optical axis and a noncollinear cryostat enclosure, allowing for improved heat transfer and compact configurations through direct-metal bonding and noncollinear cryostat orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of sensing elements is increased to improve resolution and field-of-view, then measurement precision is improved, but the mass of the detector system increases which worsens thermal isolation
Solution Approach 1:
The patent transitions from a conventional collinear arrangement (cryostat bore along optical axis) to a non-collinear configuration where the cryostat bore is offset from the optical axis. This dimensional repositioning allows the cold shield to extend further along the optical axis without being constrained by a collinear cryostat structure, thereby improving thermal isolation for high-resolution detectors with increased element count
2Object-affected harmful factors
If the cold shield length is increased to improve cold shielding effectiveness, then protection from background radiation is improved, but the time to achieve steady-state thermal conditions increases which worsens cool-down time
Solution Approach 1:
By positioning the cryostat bore non-collinearly with respect to the optical axis, the patent creates additional spatial freedom that allows the cold shield to achieve effective length and shielding coverage without proportionally increasing the thermal mass and cool-down time associated with collinear extensions
3Strength
If the cryostat bore is used to provide structural stiffness, then strength is improved, but thermal isolation is worsened due to increased thermal conduction paths
Solution Approach 1:
The patent extracts the structural support function from the cryostat bore by implementing a separate support structure that does not rely on the cryostat bore for mechanical stiffness. This separation allows the cryostat bore to be optimized purely for thermal isolation without compromising structural integrity
Solution Approach 2:
The non-collinear configuration separates the structural support function from the thermal shielding function spatially, allowing independent optimization of both functions without the trade-off inherent in collinear designs
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
This configuration enhances thermal stability and reduces cool-down times while maintaining line-of-sight stability and effective cold shielding, enabling efficient noise reduction in infrared sensor systems.
Implementation Method 1
a cold bridge coupled to the FPA carrier... coupled to the cold bridge (e.g., via a direct-metal bond)... such that the cold bridge is thermally contiguous with the carrier
Implementation Method 2
high thermal isolation... improved and compact Dewar flask designs... enhances thermal stability
Data Source
AI summary
A Dewar apparatus includes a focal plane array (FPA) component coupled to an FPA carrier, and a cold bridge coupled to the FPA carrier. A cold shield is aligned with the optical axis and coupled to the cold bridge (e.g., via a direct-metal bond), and at least one cryostat enclosure is similarly coupled to the cold bridge such that it has an axis that is noncollinear with the optical axis.