[Fwd: Re: congratulations / clock?]

[Kevin Lynch <krlynch@bu.edu>]

Oops ... forgot to respond to Peter and Steve....

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From: - Mon Jun 16 14:55:07 2003
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Date: Mon, 16 Jun 2003 14:54:46 -0400
From: Kevin Lynch <krlynch@bu.edu>
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To: Fred Gray <fegray@socrates.berkeley.edu>
Subject: Re: congratulations / clock?
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Hi again, Fred

Here are a few more detailed questions ....


Fred Gray wrote:
> On Mon, Jun 16, 2003 at 10:24:36AM -0400, Kevin Lynch wrote:
> 
> Hi, Kevin,
> 
> I'm cc'ing this to Peter and Steve; hopefully they can correct me if I'm
> wrong here, though I think Peter is on vacation now.  The frequencies that
> we need are:
> 
> To be used for high-precision timing:

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?  Or do you just need
a very tightly constrained drift specification, that is, small
day-to-day or hour-to-hour frequency drift?

> - g-2 WFDs: 200 MHz sine wave
>   * g-2 clock fanout box already being used

This shouldn't be a problem

> - ePC COMET compressors: 50 MHz, 50% duty cycle, NIM levels
>   * fanned out by controller module

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....)

> - CAEN TDCs: 25 MHz, 50% duty cycle, ECL levels 
>   * three of these; can be daisy-chained
> 

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.

> Probably not to be used for high-precision timing:
> - TDC400s: 5 MHz, 50% duty cycle, ECL levels
>   * seven of these; can be daisy-chained

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.

> - Struck flash ADCs: internal clock will be fine
> 

This is the easiest one of all  :-)


Final question:  when is all this stuff needed at PSI?

-- 
-------------------------------------------------------------------------------
Kevin Lynch				voice:	(617) 353-6025
Physics Department			Fax: (617) 353-9393
Boston University			office:	 PRB-361
590 Commonwealth Ave.			e-mail:	 krlynch@bu.edu
Boston, MA 02215 USA			http://budoe.bu.edu/~krlynch
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-- 
-------------------------------------------------------------------------------
Kevin Lynch				voice:	(617) 353-6025
Physics Department			Fax: (617) 353-9393
Boston University			office:	 PRB-361
590 Commonwealth Ave.			e-mail:	 krlynch@bu.edu
Boston, MA 02215 USA			http://budoe.bu.edu/~krlynch
-------------------------------------------------------------------------------