Piezo Positioning

The Montana Instruments Cryostation platforms can incorporate precision nano-positioning stages for translating, rotating, or tilting your sample. These are integrated into the cold space either on the standard platform or by using an optional recessed platform.

Many applications require that the sample is moved, for example:

  • Precise alignment of the sample to the optical path.
  • Scanning of the surface.
  • Large range of motion, for example, moving between a reference spot and a measurement area to remove the effects of the optical path.

The user may select a taller window assembly if they wish to get the proper optical access geometry.

INTERNAL PIEZO OPTIONS

There are several approaches to move your sample with respect to the optics. Consult with Montana Instruments for help choosing the best positioning solution for your setup and application. 

  1. Attocube precision motion stages are available in linear (x/y/z), rotation, or tilt configurations and may be stacked.
  2. Janssen Precision Engineering offers translation, rotation, and hexapod positioning configurations.
  3. Other nano-positioners designed specifically for cryogenic environments are available with unique technological features and benefits.

Attocube Cryogenic Tested Precision Motion Stages

To select the proper Attocube stage:

  1. Decide on the motion direction, magnitude and precision required. Attocube piezo stages are available in linear (x/y), vertical (z), rotation, or tilt.
  2. Determine the number of stages required.
  3. Contact Attocube and discuss the stage size, stage stack height, and the position control required.
  4. Decide if you need feedback (RES option).
  5. Select the proper stages, controller, and interface features.
  6. Work with Montana Instruments to determine the cold linking design between the cold stage and the sample on the stack.

The attached Attocube-Stages-Chart.pdf shows a summary list of the Attocube stages and their capabilities. This table is a guide for rough capabilities; see the Attocube catalog for the latest options and compatibility.

All stages indicated by /LT can be used for Low Temperature and are compatible with magnetic fields. The stages may be stacked – a typical combination is X,Y,Z with Z on the bottom. See the Attocube catalog for restrictions on stacking. The stages can be driven with coarse stepping via the slip-stick principle, or by fine positioning/scanning via DC offset voltage.

Note the use of motion stages will affect your sample vibrations, dependent on the stage used, and your base temperature slightly.

Montana Instruments will work with Attocube to help you find the right stages for your application. We can integrate those stages so your system will arrive tested and working.

FLEXIBLE THERMAL LINK

When piezo stages are mounted into a system directly on the cold platform, there needs to be a flexible link to thermally connect the sample mount on top of the stages to the cold platform. These will keep the sample within 0.2K of the platform. These are custom made depending on the stage height and motion directions. 

PIEZO RECESSED OPTION

The Cryostation is available with provision for integrated recessed piezo translation stages. These stages may be recessed into a nanopositioning insert or “pocket” below the main interface plane of the sample chamber.

The image below shows a cross section of the sample chamber base with the recessed nano-positioning insert pocket in place. The copper colored rectangle is shown extending down into the base chamber. The pocket may be removed, and the stages pre-assembled into it for installation into the sample space. 

The images below show the piezo pocket removed from the system with the stages installed and a flexible link on top. This “recessed pocket” allows you to work on your sample mount assembly with the unit out of the housing, then insert it into the housing when ready.

The piezo recessed option allows use of the recessed pocket, as well as a raised platform for non-recessed experiments. Below is an exploded view of the assembly in two configurations. On the left is the raised platform assembly. This can be removed and replaced by the nano-positioning insert assembly. This is shown on the right with the Attocube ANP-101 series XYZ positioners inserted into the recessed pocket.

Here the Z stage is on the bottom, with the horizontal stages arranged as X and Y stages in the center of the sample chamber. At the top of the stack is the flexible thermal link. It is held at the right height by the surrounding ring. The sample is placed on the small platform which is bolted to the top of the stack. This platform is thermally connected to the outer ring, which is cooled to about 3K. The thermal connections to the sample plate on top of the stack are necessary because the piezo stages are weak thermal conductors. The thermal connections provided are specially designed to be very flexible and allow stage motion in any direction. Below are additional views of the assembly.

The user could design other mechanical approaches to manipulate the sample, including a direct connection if desired. These approaches often depend on the specific application.

Piezo Recessed Option Without Stages

The user of a piezo-ready Cryostation is not required to use the Attocube stages. The standard sample mount may be mounted on top of the flat plate. This mount will be higher than the standard mounting location, due to the thickness of the flat platform. The image below shows the raised platform assembly. The Attocube stages are also not required to be recessed in the pocket. One or more stages can be configured on top of the flat mounting platform.

ABOUT USER PROVIDED PIEZO STAGES

In some cases, the end user may provide their own piezo stages to be integrated. This may be because they already have the stages or have acquired them via another channel.

Montana Instruments offers to install, wire, integrate and test the stages in the Cryostation environment. This usually involves installing them in our flexible thermal link, providing the proper wiring to minimize heat loss, installing and thermally lagging that wire properly, and testing this assembly in the cryostat. We will test for range of motion, try to identify any stage functional problems, and test for thermal performance in the system. This involves cooling down the system with the stage installed and verifying the base temperature of the sample on the piezos and flex link. This often involves a custom sample mount unique to the user. We do not test for vibrations of the sample on top of the stack, unless the end user has requested and paid for this service. This is often time consuming and may involve special test fixtures. The real value here is that we test for stage motion in the flex link at low temperatures and we optimize the base temperature.

We offer this service at minimal cost, because it can really help the end user. It is possible for a user to do this themselves, but if it is done incorrectly it will lead to customer frustration and require support from Montana Instruments to determine the problem and solution. A new user who does not know the subtleties of wire selection and routing can spend a lot of time and end up with a poor result. We often talk to users who have used copper wires, or poorly lagged the wires and have temperature many degrees above their goal. This may appear like a system performance issue, when the problem was introduced post-delivery. Please take advantage of our experience, and if in doubt, ask questions.

Once the stages have been tested in the system, to prepare the system for shipping, we remove the stages from the system. It is not safe for the stages to travel installed in the cryostat, except in special situations where we know the shipping method and have properly packed the stages for the trip. It is almost always better to ship the stages separately. They will be provided in a foam case, along with the flex link in a separate holder.

When you get the system, you should locate the stages and link and assemble them carefully per the user instructions. The help article How to Install Nanopositioners in Montana Instruments Systems provides a series of step by step videos showing proper assembly and installation techniques. This, if done carefully, should take about 30 minutes to assemble into the flexible link and wire. These steps are necessary even if the stages are purchased through Montana Instruments. Again, please let us know if you have any questions and we will be happy to help. 

Note: If there are any problems with user supplied stages, they must be supported by the end user. That is, if they arrive non-functional, even if they are new, then the user must arrange and pay for return shipping and any repair costs. We have seen a number of failures of the stages when unpacked new, and can work with Attocube or other vendors to try to debug these situations.