Re: Radiated noise from the Cockcroft Walton bases

[Paul Smith <ptsmith@indiana.edu>]

Hi Elton,

The only thing I've looked at is the output signal from the CW bases;  
there is switching noise at the charge pump frequency (~ 1 KHz) of  
about 10 mV into 50 ohms.

I've never looked at radiated noise per se; in E852 we had the  
Russian CW bases less than a meter away from a drift chamber with no  
problems.

In both E852 and RadPhi each base and PMT was enclosed in an iron  
tube for magnetic shielding; this would also shield against any  
radiated electrical noise.  There has been some discussion of not  
having these iron tubes in the GlueX cell wall.  However, the FCAL  
will still be in some sort of metal box, so there should still be  
shielding against radiated noise.

Ideally one would like some sort of spectrum analyzer setup in order  
to measure radiated noise as a function of frequency, distance, and  
shielding.  This has not been done.

Paul


On Mar 31, 2007, at 8:42 AM, Elton Smith wrote:

>
> Hi Paul,
>
> Joe Beaufait, who has been working on installation issues in Hall  
> D, asked
> me about the radiation noise from the Cockcroft Walton bases. Could  
> you
> remind me in what detail this has been checked? Recall that we will be
> operating relatively near to the drift chambers. Since you have 100  
> bases
> built, some checkes could be done fairly quickly. I know that we  
> did not
> have any noise issues in RadPhi, but there were no chambers in the  
> system.
>
> Thanks, Elton.
>
> Elton Smith
> Jefferson Lab MS 12H5
> 12000 Jefferson Ave
> Suite # 16
> Newport News, VA 23606
> elton@jlab.org
> (757) 269-7625