[Eg2] Fwd: Target densities

[Will Brooks]

Dear Youri,

  Thanks for the detective work!

It would be great if he could do a measurement of the remaining sample, 
just for completeness.

It seems that in our NIM paper we also used 2.2 g/cm3. However, for the 
Material Data Sheet that may just be a reference value given the 
production method, not a precisely measured value. Since people are now 
doing data mining on the EG2 data, some analyses require or would 
benefit from an absolute knowledge of the densities. Carbon is the only 
one that can vary, so it might be worth measuring that one, if possible.

Thanks,

  - Will



On 1/21/11 10:53 AM, Youri wrote:
> Dear Will,
>
> Gary Slack has found the files regarding carbon target. The Material Data
> Sheet provides density 2.2 g/cm3, and Gary told me that he never have
> tried to "check" this number by direct measurements. Gary also told me
> that he has in his lab leftovers of the carbon material. You can easily
> see the importance of the news. I asked Gary to keep everything and wait
> for the corresponding decision. Please let me know.
> My best regards,
>                    Youri
>
>
>
> -------- Original Message --------
> Subject: 	[Eg2] Target densities
> Date: 	Tue, 11 Jan 2011 17:46:41 -0600
> From: 	Dupré Raphaël<raphael.dupre at gmail.com>
> To: 	EG2<eg2 at jlab.org>
>
>
>
> Hi everybody,
>
> After this afternoon meeting I have some concern about the values for
> the target thickness especially Carbon.
>
> In the NIM paper there is a table indicating areal densities as: C = .38
> ; Fe = 0.31 ; Pb = 0.16 g/cm2
> Simple calculation with Hyupwoo numbers gives 2H = .325 g/cm2
>
> Then ratios of electrons from the targets in data should give something
> around: C = 1.17 ; Fe = .95 ; Pb = .49
> I found with my cuts: C = .91 ; Fe = .96 ; Pb = .46 It is a good
> agreement except for Carbon!
>
> If I use Hyupwoo numbers for the Carbon areal density, I find the same
> than in the NIM paper, but I am concerned with the value of 2.267 g/cm3
> because graphite seem to have variable density depending on the web site
> you consult, what I could grab was that raw mineral graphite is between
> 2.09 and 2.3 g/cm3 but that once treated it can get much lighter (I seen
> 1.57, 1.7 and 1.8 in various places). On the NIST web site they use
> density of 1.7 g/cm3 for graphite and that would lead to an areal
> density of .29 g/cm2 which give a ratio in data of .90 in agreement with
> what I observe in data.
>
> --
> Raphaël Dupré
>
>
> Argonne National Laboratory
>
> Université Claude Bernard Lyon 1
>
>