Re: FCal

["Mark M. Ito" <marki@jlab.org>]

Better to comment late than never. ;-)

Using the lead tungstate gives a big improvement in photon energy 
resolution for PrimEx, from 5.4% in the lead glass to 2.5% in the lead 
tungstate at 1 GeV.

whitey@jlab.org wrote:
> Hi Elke,
>
>  The 3 main reasons for the support structure are to force the blocks
> tight together so there is no gap between (tolerance can build up over 60
> blocks across)and to hold the blocks in place against the force of the
> cell wall against them (that keeps pressure on the cookie). Also, a
> structure is needed to hold the TOF. We can probably still stagger and
> keep the round shape.
>
> I will speak with Dave Kashey about this matter.
>
> Cheers,
> Tim
>
>   
>> Dear Tim et al.,
>>
>> something to think about. On Saturday Curtis and I talked to the primex
>> people and Ashot mentioned that the primes calorimeter is staggered with
>> out supporting the lead-tungsten and lead glass blocks.
>>
>> The have quite some blocks and what i understood the calo weighs 8 tonnes.
>> Mt question is why do we need a support structure for the FCal. Dave Kashy
>> was involved in the design of the primex calorimeter, maybe we can talk to
>> him ones on this issue.
>>
>> One reason why I'm asking is that there is the idea to reuse the Primex
>> blocks for the inner part of the FCal. one thing is they are only 20x20
>> mm^2 but the other issue is there might be an upgrade for the FCal to
>> replace some of lead glass blocks with time with lead tungsten ones. so we
>> would need a new cellular wall and so on and so on. Of course the
>> staggering does not work for a round calorimeter, but do we need really a
>> round one. Okay we have to think this over a bit.
>>
>> Cheers elke
>>
>>
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>
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