add Au197 5x41 GeV magnet configuration (scaled from top energy) (#897)

### Briefly, what does this PR introduce?

Add 5x41 GeV Au-197 magnetic field configuration as an option (using a
scaled field from the top energy config).

### What kind of change does this PR introduce?
- [ ] Bug fix (issue #__)
- [ x] New feature (issue #__)
- [ ] Documentation update
- [ ] Other: __

### Please check if this PR fulfills the following:
- [ ] Tests for the changes have been added
- [ ] Documentation has been added / updated
- [ ] Changes have been communicated to collaborators

### Does this PR introduce breaking changes? What changes might users
need to make to their code?

No, just adds new configuration.

### Does this PR change default behavior?

No.

---------

Co-authored-by: Alexander Jentsch <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Wouter Deconinck <[email protected]>

Author: 4 people

compact/fields/beamline_5x41_Au197.xml

@@ -0,0 +1,68 @@
+<!-- SPDX-License-Identifier: LGPL-3.0-or-later -->
+<!-- Copyright (C) 2023 Sylvester Joosten, Alex Jentsch, Whitney Armstrong, Simon Gardner -->
+
+  <define>
+
+    <constant name="ElectronBeamEnergy" value="5*GeV"  />
+    <constant name="IonBeamEnergy"      value="41*GeV" /> <!-- per nucleon beam energy -->
+
+    <constant name="FieldScaleFactor" value="102.24/275.0"  /> <!-- only use for light ion beams!!! ASK FF EXPERTS -->
+
+    <comment>
+       Backwards Fields
+       Values taken from: https://indico.bnl.gov/event/10974/contributions/51260/
+       Relevent values in the tables scale linearly with beam energy
+    </comment>
+
+
+    <!-- Beamline -->
+    <constant name="Q1eR_Gradient"  value="-0.739741*tesla/meter/GeV*ElectronBeamEnergy"/>
+    <constant name="Q2eR_Gradient"  value="0.66821*tesla/meter/GeV*ElectronBeamEnergy"/>
+    <constant name="Q3eR_Gradient"  value="0.21674*tesla/meter/GeV*ElectronBeamEnergy"/>
+
+    <constant name="B2AeR_B"        value="0.0106667*tesla/GeV*ElectronBeamEnergy"/>
+    <constant name="B2BeR_B"        value="0.0132222*tesla/GeV*ElectronBeamEnergy"/>
+
+    <!-- Luminosity System -->
+    <constant name="LumiSweepMag_B"     value="1/1.2*tesla"/>
+    <constant name="LumiAnalyzerMag_B"  value="1/1.2*tesla"/>
+
+
+    <comment>
+       Forward Fields
+       All magnet values are input by hand and represent the implementation in EICRoot used for the Yellow Report.
+    </comment>
+
+    <constant name="B0PF_GradientMax"  value="-8.12238283*tesla/m"/>
+    <constant name="B0APF_GradientMax" value="0.0*tesla/m"/>
+    <constant name="Q1APF_GradientMax" value="-72.608*tesla/m"/>
+    <constant name="Q1BPF_GradientMax" value="-63.24525402*tesla/m"/>
+    <constant name="Q2PF_GradientMax"  value="36.88301623*tesla/m"/>
+    <constant name="B1PF_GradientMax"  value="0.0*tesla/m"/>
+    <constant name="B1APF_GradientMax" value="0.0*tesla/m"/>
+    <constant name="B2PF_GradientMax"  value="0.0*tesla/m"/>
+    <constant name="Q0EF_GradientMax" value="-13.12887*tesla/m"/>
+    <constant name="Q1EF_GradientMax"  value="5.85089*tesla/m"/>
+
+    <constant name="B0PF_Bmax"  value="1.1840539*tesla"/>
+    <constant name="B0APF_Bmax" value="3.4314469*tesla"/>
+    <constant name="Q1APF_Bmax" value="0.0*tesla"/>
+    <constant name="Q1BPF_Bmax" value="0.0*tesla"/>
+    <constant name="Q2PF_Bmax"  value="0.0*tesla"/>
+    <constant name="B1PF_Bmax"  value="3.447989*tesla"/>
+    <constant name="B1APF_Bmax" value="2.7*tesla"/>
+    <constant name="B2PF_Bmax" value="-4.7890142*tesla"/>
+    <constant name="Q0EF_BMax" value="0.0*tesla"/>
+    <constant name="Q1EF_BMax"  value="0.0*tesla"/>
+
+    <comment>
+    These are the ten-sigma cuts for the Roman pots, translated to the physical layout we currently have.
+    They are not perfectly ten-sigma for reasons of physical geometry.
+    </comment>
+
+        <constant name="offset_central_RP_section" value ="0.71*cm"/>
+    <constant name="offset_intermediate_1_RP_section" value ="0.55*cm"/>
+    <constant name="offset_intermediate_2_RP_section" value ="0.0*cm"/>
+    <constant name="offset_outer_RP_section" value ="0.0*cm"/>
+
+  </define>