sPHENIX HCal discussion

[EdwardOBrien <eobrien AT bnl.gov>]

        John,
         Your analysis seems quite reasonable. Then you're proposing
        that we use standard steel for the performance prototypes
        for both the Inner and Outer. The mechanical or engineering
        prototypes are to be made of the actual material we intend to
        use. Do you think that it is worthwhile adding a GEANT4
        performance study of a 310 stainless vs standard steel
        calorimeter to our list of detector simulations. I am sure
        that a committee will ask.

        Ed


On 6/19/2015 11:41 AM, John Haggerty wrote:
> The question of whether we need to make the IHCAL performance prototype
> out of stainless steel came up at yesterday's meeting again.  It's
> harder to work with mechanically, and more expensive, and I don't think
> there will be any discernible difference, and here's my analysis of that
> question.  Of course, I could be wrong, so more eyes on the question
> would be good.
>
> The non-magnetic stainless steel we used in the PHENIX absorber on the
> central magnet came with an assay that had these components:
>
> >      Z       A     rho       X       %
> > C    6  12.011   2.266  42.698   0.050
> > Mn  25  54.938   7.473  14.640   0.960
> > P   15  30.974   1.820  21.205   0.025
> > S   16  32.060   2.086  19.493   0.000
> > Si  14  28.086   2.329  21.823   0.560
> > Ni  28  58.700   8.907  12.679  19.380
> > Cr  24  51.996   7.194  14.944  24.450
> > Mo  42  95.940  10.222   9.801   0.250
> > Co  27  58.993   8.800  13.631   0.150
> > Cu  29  63.546   8.933  12.862   0.280
> > N    7  14.007   0.001  37.989   0.055
> > Fe  26  55.847   7.873  13.839  53.840
> >                  7.874  13.873
>
> and if you cruise the web, you'll see that's typical for "310 stainless
> steel."  (The above table was from when we got it and I calculated the
> radiation length of the mixture for fun; if I did the weighting right,
> the radiation length of the SS310, the 13.873 g/cm^2, is pretty close to
> elemental Fe, which is >99.5% of a carbon steel like 1006 which we'll
> use in the flux return; the density is pretty much the same, too.)  It's
> not mysterious, the other big components, Ni and Cr, surround Fe on the
> periodic table, and have quite similar properties.
>
> I thought I better check a little further, so I used my super-idealized
> model of the IHCAL based on a GEANT example to look at the difference; I
> made a nominal 1 interaction length calorimeter out of 4 Fe plates
> (that's the "4 crossing") 42 mm thick (the interaction length of Fe is
> 167.7 mm), and shot some 10GeV pi+'s at it and used matScan to measure
> the interaction length.
>
> > The calorimeter is 4 layers of: [ 42mm of G4_Fe + 7mm of G4_POLYSTYRENE ]
> >  mean Energy in Absorber : 1.74625 GeV +- 1.86963 GeV
> >  mean Energy in Gap      : 56.5529 MeV +- 61.824 MeV
> >  mean trackLength in Absorber : 1.1057 m   +- 1.19615 m
> >  mean trackLength in Gap      : 19.1849 cm  +- 19.3933 cm
> >
> > and the matScan agrees with my arithmetic:
> >
> >
> > /control/matScan/singleMeasure 0 0
> >
> >          Theta(deg)    Phi(deg)  Length(mm)          x0     lambda0
> >                   0           0      1017.6     9.62684     1.03024
>
> The material G4_STAINLESS-STEEL packaged with GEANT isn't 310, it's
> about 74% Fe, so we should cook up the material correctly, but just to
> get a quick idea, here are the statistics from running 10 GeV pions
> through that, and the matScan:
>
> > The calorimeter is 4 layers of: [ 42mm of G4_STAINLESS-STEEL + 7mm of
> > G4_POLYSTYRENE ]
> >  mean Energy in Absorber : 1.7336 GeV +- 1.76738 GeV
> >  mean Energy in Gap      : 59.5918 MeV +- 65.2185 MeV
> >  mean trackLength in Absorber : 1.03557 m   +- 1.08142 m
> >  mean trackLength in Gap      : 18.3985 cm  +- 18.4141 cm
> >
> >          Theta(deg)    Phi(deg)  Length(mm)          x0     lambda0
> >                   0           0      1017.6     9.73369     1.04876
>
> So I think it's ok to make the prototype out of pretty much any steel as
> far as its properties as an absorber, as far as I can see.  Probably not
> so true for the mechanical prototype, where we may have to learn to deal
> with a material that is rather difficult to work with.
>
>
>
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