Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Motion at cryogenic (2.8) K

Motion at cryogenic (2.8) K

Motion at cryogenic (2.8) K

I am trying to align light from an optical fiber in an imaging assembly. Currently the optical fiber is outside of the cryostat and the light is coupled in through a window and the fiber is outside the cryostat. I am investigating putting the fiber and all the optics inside the cryostat, but I will need some way to position the fiber at 2.8 K with ~1 um accuracy over about 500 um travel in x, y, z, and would like the positioner to have as small a package as possible. My only choices seem to me magnetoresistive inchworms or stepper motors, neither of which is very small. Any advice on what to use or where to look?


RE: Motion at cryogenic (2.8) K

You can find a lot of good info at this site:


It sounds challenging.  Best of luck.


RE: Motion at cryogenic (2.8) K

In my 30+ years I found that if a problem is difficult, it is time to check if it is necessary at all. For example couldn't you position the fibre just once, permanently ?


RE: Motion at cryogenic (2.8) K

nbucska, you're philosophy is sound. We've looking into one-piece designs, but our detectors are very new and we need to have enough degrees of freedom to check alignment, at least until the detectors become mature.

In case anyone is following this tiny thread, I'll give an update. We've settled on a more-or-less conventional optical mounting scheme with 80-tpi screws lubricated with molibdinum disulfide (sp?). To adjust the mount we're using wiggle stick feed through that also slides and rotates to. An allen key at the end of the wiggle stick lets us turn the screws very easily. Viewports on the side of the vacuum chamber let us see what we are doing. One advantage of working at cryogenic tempreatures is that there is very little temperature-dependent mechanical drift, once things are cold, so the alignment need only be done once.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close