[Solid_baffle] baffle material

[Zhiwen Zhao]

Dear All

As we are discussing baffle material again, I added some of you to the 
"solid_baffle" list.
Let's use it so that emails are archived like here
https://mailman.jlab.org/pipermail/solid_baffle/

I think we should design baffle and neutron shielding together.

= note from Roger  =============================================
"recommended Copper Tungsten Alloy (W70/Cu30) used by Qweak collimator, 
which is eat-resistant, ablation-resistant, highly thermally and 
electrically conductive, and easy to machine. he had some concerns about 
neutrons"

= note from Rich ===========================================
There are some slides in this talk
https://hallaweb.jlab.org/wiki/images/9/95/Baffles_5-15_rsholmes.pdf (two
slides from Zhiwen and three of mine), which also are summarized in my
baffle writeup at
https://hallaweb.jlab.org/wiki/images/9/91/Baffles_writeup_2-2016.pdf. With
Cu the photon rate is about 15% higher than for Pb overall. The energy
dependence of this probably should be checked. With Pb lined Cu the photon
rate is about 8% higher, and if the last baffle is solid Pb it performs
about the same as Pb. Pb lined Cu has some of the advantages of solid Cu,
though it would be the same as far as machining the slits is concerned.

There were questions about the activation of Cu which I'm not sure we 
ever got a good answer to.
==============================================================

thanks

Zhiwen

On 7/11/2016 4:18 PM, Zhiwen Zhao wrote:
> So the baffle in pCDR gives slightly better trigger and worse background 
> for Copper than lead
> After Rich finishes tuning the new baffle, we can test background and 
> trigger again to see if these conclusions hold
> 
> Who is working on evaluating it with engineering input?
> 
> Do we need to decide on the default material before reply to the review 
> by Aug?
> 
> Zhiwen
> 
> On 7/11/2016 3:33 PM, Paul A Souder wrote:
>> I would think that final background rates and engineering input would be
>> needed before the final decision is make.  Both Cu and Pb have 
>> advantages.
>>
>> Paul
>>
>> From: Solid_baffle <solid_baffle-bounces at jlab.org
>> <mailto:solid_baffle-bounces at jlab.org>> on behalf of "Richard S. Holmes"
>> <rsholmes at syr.edu <mailto:rsholmes at syr.edu>>
>> Date: Monday, July 11, 2016 at 3:22 PM
>> To: Zhiwen Zhao <zwzhao at jlab.org <mailto:zwzhao at jlab.org>>,
>> "solid_baffle at jlab.org <mailto:solid_baffle at jlab.org>"
>> <solid_baffle at jlab.org <mailto:solid_baffle at jlab.org>>
>> Subject: Re: [Solid_baffle] baffle material
>>
>> There are some slides in this
>> talk 
>> https://hallaweb.jlab.org/wiki/images/9/95/Baffles_5-15_rsholmes.pdf (two
>> slides from Zhiwen and three of mine), which also are summarized in my
>> baffle writeup
>> at 
>> https://hallaweb.jlab.org/wiki/images/9/91/Baffles_writeup_2-2016.pdf. 
>> With
>> Cu the photon rate is about 15% higher than for Pb overall. The energy
>> dependence of this probably should be checked. With Pb lined Cu the
>> photon rate is about 8% higher, and if the last baffle is solid Pb
>> it performs about the same as Pb. Pb lined Cu has some of the advantages
>> of solid Cu, though it would be the same as far as machining the slits
>> is concerned.
>>
>> There were questions about the activation of Cu which I'm not sure we
>> ever got a good answer to.
>>
>>
>> On Mon, Jul 11, 2016 at 3:02 PM Zhiwen Zhao <zwzhao at jlab.org
>> <mailto:zwzhao at jlab.org>> wrote:
>>
>>     Dear All
>>
>>     The question about baffle material was raised by the review committee
>>     and need to be addressed
>>
>>     I had the study last year showing Copper seems not a bad choice among
>>     other materials.
>>     
>> http://hallaweb.jlab.org/12GeV/SoLID/download/baffle/talk/solid_baffle_zwzhao_20150316.pdf 
>>
>>     I think Rich also had some study favoring Copper, but I can't find 
>> the
>>     record any more.
>>
>>     If we decide on Copper, we can
>>     1. use that to do background and trigger study from now on.
>>     2. Rich could further tune baffle because Copper can be machined with
>>     good precision.
>>         (for example, maybe the inner surface of baffle slit can have 
>> some
>>     angle to follow electrons within the 9cm length)
>>
>>     Practically, it would be some kind Copper alloy.
>>     Roger from hallC has good suggestion and experience from Qweak
>>     Collimator
>>     Seamus, maybe you can even get some cost estimation to update the 
>> very
>>     rough number in pCDR.
>>
>>     Thanks
>>
>>     Zhiwen
>>     _______________________________________________
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>>     Solid_baffle at jlab.org <mailto:Solid_baffle at jlab.org>
>>     https://mailman.jlab.org/mailman/listinfo/solid_baffle
>>
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