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Section 2.4
High-Vacuum Hardware
2.4
Chapter 2
Hardware
High-Vacuum Hardware
The High-Vacuum option, which operates in conjunction with the TTO system, reduces the amount of
gas in the sample chamber and thus minimizes stray thermal conduction from the heated sample. The
TTO system works with either the Turbo Pump High-Vacuum option or the Cryopump High-Vacuum
option. The details of the Turbo Pump and Cryopump high-vacuum systems are contained in the
Physical Property Measurement System: Turbo Pump High-Vacuum Option User’s Manual and
Physical Property Measurement System: Cryopump High-Vacuum Option User’s Manual,
respectively.
2.4.1
Contact Baffle
An integral part of either the Turbo Pump or the Cryopump High-Vacuum system is the contact baffle
assembly. The contact baffle makes thermal contact with the isothermal region of the sample chamber,
which is just above the puck. The thermal contact between the contact baffle and the isothermal region
helps create a more uniform thermal environment for the puck by causing the contact baffle to be at the
same temperature as the chamber walls that are near the puck. This is important when high vacuum is
enabled; high vacuum reduces the amount of thermal exchange gas in the sample chamber.
You insert the contact baffle into the brass fitting that is at the bottom of the baffle assembly (see
Figure 2-8B). To help safeguard the contact baffle, use it only when you are using the High-Vacuum
option. Handle the contact baffle with care, and avoid touching the delicate outer contact fingers. The
charcoal holder is used to achieve the best vacuum at low temperatures and should always be screwed
onto the bottom of the contact baffle when in the high-vacuum state. However, when performing a
temperature calibration of any sample hardware, such as TTO shoe assemblies, the charcoal holder
should be removed to ensure that adequate thermal exchange gas remains in the sample chamber at low
temperature.
Figure 2-7. Baffle Assembly with Contact Baffle
A. Charcoal Holder Removed for Puck Calibration
B. Charcoal Holder Installed for Normal Operation
Figure 2-8. Close-up View of Contact Fingers and Charcoal Holder on Contact Baffle Assembly
2-8
PPMS Thermal Transport Option User’s Manual
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