Re: congratulations / clock?

[Peter Kammel <kammel@npl.uiuc.edu>]

Dear Kevin and Fred,

I basically agree with what has been said, otherwise I would have reacted
earlier under the palm trees. Now only a few remarks after I am back in
Illinois.

Thanks for your initiative and best regards

Peter

On Mon, 16 Jun 2003, Fred Gray wrote:

> > What do you mean by high-precision?  Do you need the clock for timing 
> > accuracy, as in MuLan, which will require the nominal frequency to match 
> > the actual frequency to a few parts in, say, 10^6?  
> 
> Yes, it's a lifetime measurement, and these are the devices that will be
> used to assign times. 

Few 0.1 ppm would be better. The experimental is designed so that
individual uncertainties are at the few ppm level, the clock
stability should be a negligible contribution to that. 

> 
> > We can divide this down from the 200MHz sine wave with a high speed ECL 
> > flip-flop based circuit ... conversion to NIM is probably best done with 
> > a high speed NIM discriminator module, unless it is essential that that 
> > 50% duty cycle be dead on (that is, the compressors operate on both 
> > clock edges....)
> 
> I don't know how critical the duty cycle is for the compressors.  For the 
> CAEN TDCs, it is definitely an important issue.  I'll write to Rene now 
> about this one.
> 
OK
> > ECL is no problem ... but just so that we are on the same page: does the 
> >  device require ECL logic levels for the clock (-0.8V and -1.6V) or 
> > signals compatible with ECL, but without the offset (0.8Vpp)?  Again, 
> > we'll divide this one down from the main 200MHz clock.
> 
> We currently use the ECL logic levels, including the offset.  
> The documentation claims that all inputs (including the clock) are treated
> differentially.  However, the documentation for this module is known to be 
> wrong about quite a few things.
> 
It would be crazy if the ECL receiver is not differential...

> > This one is slightly more challenging, just because it is a factor of 40 
> > smaller than the 200MHz clock.  If this really doesn't need to be high 
> > precision, we might be able to get away with a cheap crystal oscillator 
> > signal that we convert to ECL.  Same ECL level questions.
> 

As stated earlier we can subdivide using PSI modules and FPGA. So we will
derive the TDC400 clock from the main Boston clock, but Boston does
not need to worry about this distibution.

> Alternatively, the current setup (derived from the PSI accelerator clock 
> through a PSI clock divider module) will probably continue to be adequate.
> 
> > Final question:  when is all this stuff needed at PSI?
> 
> My understanding of the timeline is the following:
> - The TPC has successfully seen muon tracks while filled with nitrogen.
> - Conditioning of the TPC with protium is currently underway; it is likely 
>   to be ready to go again this week.  (Late-breaking correction: due to
>   a hot spot, they had to go back to nitrogen.)
> - Over the next couple of weeks, we will attempt to take some data as a 
>   proof of concept.  (Assuming, as always, that the TPC can be made to work.)
> - In July, fix up any remaining issues and possibly install the new ePC2.
>   More importantly, a review by the lab directory will be done to determine 
>   how long the run is allowed to go.
> - In early August, re-commission everything with the new ePC2 (if we decided
>   to install it).  Begin production running.
> - September 17: if we didn't get an extension, the muE4 beamline is shut 
>   down for a complete overhaul, and muCap is done for a while.
> - October 15: if we did get an extension, ditto.
> 
> So, it probably needs to be installed by early August.

OK
> 
> -- Fred
> 
> -- Fred Gray / Visiting Postdoctoral Researcher                         --
> -- Department of Physics / University of California, Berkeley           --
> -- fegray@socrates.berkeley.edu / phone 510-642-4057 / fax 510-642-9811 --
> 

Peter Kammel  /  pkammel@uiuc.edu
Department of Physics, Loomis Laboratory
University of Illinois at Urbana-Champaign
1110 West Green Street, Urbana, IL 61801 
Tel (217) 333-5424 / Fax (217) 333-1215