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Cryo-electron Microscopy Specimen Preparation By Means Of a Focused Ion Beam
Published on: July 26, 2014
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Heat Transfer Analysis of Cryogenic EXLO Specimen Handling
Kyle W Beggs1, Thomas E Dougherty2, Alain J Kassab1
1Centecorp LLC, Longwood, 147 Parsons Rd, FL 32779, USA.
Summary
Cryogenic lift-out specimen handling (cryo-EXLO) analysis shows specimens stay below critical vitreous temperature hundreds of micrometers above liquid nitrogen surfaces. This allows ample manipulation time, even without continuous cryogen replenishment.
Area of Science:
- Cryogenic Engineering
- Materials Science
- Heat Transfer
Background:
- Cryogenic specimen handling is crucial for preserving sample integrity.
- Maintaining temperatures below the vitreous transition point is essential for cryo-EXLO.
- Accurate thermal analysis is needed to define safe manipulation zones.
Purpose of the Study:
- To analyze heat conduction during ex situ lift-out specimen handling under cryogenic conditions (cryo-EXLO).
- To compare computational thermal analysis with experimental temperature measurements.
- To determine the thermal viability of cryo-EXLO at various heights above a cryogenic surface.
Main Methods:
- Conduction heat transfer analysis using a finite-volume solver.
- Experimental temperature measurements utilizing a type K thermocouple.
- Simulations performed for specimen handling above a liquid nitrogen (LN2) cooled surface.
Main Results:
- Specimen temperature remains below the critical vitreous temperature up to hundreds of micrometers above the LN2 surface.
- Temperatures above the cryogenic shuttle sample holder stay below the vitreous temperature for tens of minutes without active cryogen addition.
- The analysis validates the feasibility of cryo-EXLO with sufficient thermal margin.
Conclusions:
- Cryo-EXLO is thermally viable, offering a significant working distance above the cryogenic surface.
- Extended manipulation times are achievable without continuous cryogen replenishment.
- Periodic cryogen top-offs can enable virtually unlimited cryo-EXLO manipulations with the current setup.
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