[Ifeffit] current-amp recommendation

Bruce Ravel bravel at bnl.gov
Tue Nov 14 14:43:36 CST 2017

Hi Matthew,

At NSLS-II, we use a solution developed here at BNL for quad BPMs and 
other current-measurement operations.  (I am using it for ion chambers 
at my beam line.)

It is a box developed in the Instrumentation Division with a current 
amplifier, an A2D converter, and a microprocessor all inside a box 
that's about the size of a box of Pop Tarts.  It has 4 SMA input 
channels and a single gain for all four channels.  SMA to BNC cables are 
readily available from all the standard vendors.  The output is an 
ethernet cable.  The microprocessor runs a small debian system and 
starts an EPICS IOC and a DHCP client on boot.  the 4 current get 
exposed as 4 PVs and the IOC does a lot of useful statistics on the fly.

Seems to work pretty well.

You could contact Pete Siddons.  (Search for Siddons at the BNL website. 
  When I tried it, the second hit was his staff page.)


On 11/14/2017 03:16 PM, Matthew Marcus wrote:
> I've gotten involved with a project in which stabilization of the 
> position of a monochromatic, soft X-ray beam is needed.  The
> offending frequencies seem to be vibration frequencies like 57 and 
> 116Hz.  We have in mind to use a thin Au film with a gap in the
> middle, measuring the drain current from the films, much as people 
> normally use the jaws of slits.  Now, I'd like to find a couple
> of current amplifiers which are small enough so that they can be 
> connected with very short cables to the BNC connectors on the
> air-side of this detector, and which would have decent frequency 
> response and low noise with inputs of the order of 0.1-1nA.
> Although this topic is outside the realm of XAFS analysis with IFEFFIT, 
> I figure that people on this group might have some
> good experience.
>      mam
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  Bruce Ravel  ------------------------------------ bravel at bnl.gov

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS-II
  Building 743, Room 114
  Upton NY, 11973

  Homepage:    http://bruceravel.github.io/home/
  Beamline:    https://www.bnl.gov/ps/beamlines/beamline.php?r=6-BM
  Software:    https://github.com/bruceravel
  Demeter:     http://bruceravel.github.io/demeter/

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