[time-nuts] Cheap Rubidium

Demian Martin demianm_1 at yahoo.com
Fri Dec 25 05:46:00 UTC 2009


MuMetal us great when you need a shield that is thin and pretty light. It
needs to be hydrogen annealed after you form it etc. and its expensive.
However for shielding what you need is a magnetic shunt. If weight isn't a
problem (probably isn't if it's a stationary application) the cheap way to
get good shielding is cast iron sewer pipe. The thickness is enough that
even if its hard magnetically very little flux will get past it. Plus, once
it's at temperature it will take a long time to change. It's very heavy but
that helps reduce the internal vibration. The styling may be an issue, you
might want to make an external housing. Here are some general details:
http://www.acipco.com/adip/pipe/flanged/specs.cfm 


>Date: Thu, 24 Dec 2009 15:55:23 -0500
>From: Bob Camp <lists at cq.nu>
>Subject: Re: [time-nuts] Cheap Rubidium
>To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
>Message-ID: <8F61B9AF-818D-4D1C-B7A9-AC005D688E19 at cq.nu>
>Content-Type: text/plain; charset=us-ascii
>Hi

>Every time I've tried the coli thing, field uniformity has become an issue.
I'm also not real sure just how stable multi axis mag sensors are.

>If I had a bunch of mu metal sitting in the basement I'd certainly use it
in the setup. Last time I checked the stuff was not cheap ....

>Bob

Demian Martin
Product Design Services
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