Montana Instruments Cryostation s Series - System Performance Checks

System User Manual
62
7.3 System Checks
For the system to achieve optimal performance, several aspects of the system must be handled
carefully. Neglecting any one of these may have a significant impact on the base temperature or
vibration performance. There are several basic checks users can do to help diagnose general problems.
7.3.1 Temperature Optimization
The cryostat platforms are optimized to control heat loads coming into the sample. To ensure the
lowest possible base temperatures, follow the best practices below.
1. Use proper thermal lagging techniques for any wiring (including coax) entering the sample
space. Ensure thermal clamps are tightened down. See Thermal Lagging Techniques on page 42
for details.
2. Avoid “touches” between the various stages (such as a platform component touching a Stage 2
component, or a Stage 2 component touching a Stage 1 component), as these become sources
of heat flow.
a. Ensure wiring or cabling does not come in contact with the inside of the radiation shield.
b. Ensure the radiation shield or radiation windows do not come in contact with any part of
the outer vacuum housing or windows. For low working distance setups, the windows
may touch after the vacuum is pulled.
3. Always use the appropriate wire and size for the application. See Sample Chamber Wiring on
page 42 for details.
a. Avoid using copper wire unless absolutely required. The electrical conductivity of
phosphor bronze is typically sufficient for most applications.
4. Ensure the screws holding the platform to the support base and the screws securing the
radiation shield are in place and tightened (5 in-lbs). Failure to tighten the screws will reduce the
ability of the system to pull heat from the sample platform and may increase vibrations.
5. Use inner “cold” windows or blanks on the radiation shield whenever possible. The added heat
load can significantly increase the base temperature of the platform.
6. Check the helium pressure. If there is a helium leak, cooling performance will be hindered
significantly. See Helium Check on page 64 for details.
7. Ensure the User temperature channel heater is not on.
» NOTE
During a cooldown, the system will steadily ramp down in temperature to 4.2 K, then can take longer
to reach and stabilize at the base temperature. Options and energy inputs (i.e. laser power) may
impact cooldown times and cause slightly higher base temperatures.
7.3.2 Vibration Mitigation
The cryostat and sample chamber have several vibration damping design features to reduce the effects
of cryocooler mechanical vibrations on the sample platform. To ensure the lowest possible mechanical
vibrations, follow the best practices below.