Recent Upgrade of g4lbnf: Horn B & C, Conceptual Design revision 2 Paul Lebrun ND/Fermilab. January 10 2017 Realistic Horns in G4LBNF 1
This a corrected version of the talk written a week ago, presented on Friday January 6 January 10 2017 Realistic Horns in G4LBNF 2
Outline Horn B & C, revision 2 => Coded up. ==> geantino plots ✔ (Horn A, small improvements to the code. ) ✔ Comparison, Horn “ideal” (as coming out of the genetic algorithm based optimization ✔ of Laura F. et al) vs “Realistic”, detailed G4 implementation of all “relevant” volumes found in the NX-9 CAD model, and corresponding changes to the magnetic field map. Next steps: ✔ – Retune a bit (spacing between horns, horn current..) – small changes in horn length??? Is this worth trying? – Study the effect of field maps upgrades in the Inner/Outer conductor regions, and other non-unformities – Realistic Beam window, Rev X. ? January 10 2017 Realistic Horns in G4LBNF 3
… Few programming notes.. Now using Geant4 v 4.10.2.p02 .. The change I made to the code ✔ caused crashed using the previous release, due to bug in the G4 geometry navigation code, fixed months ago... So, I am using ROOT 6.x, and a newer compiler, as I haven't found a ✔ matching DK2Nu with the old old ROOT and this new compiler. – This might break the old style nutrino N-tuples code. My advice: use the Dk2NU package from now on. I haven't not yet committed the changes.. Bigger change then just G4. ✔ Laura F. has upgraded our neutrino analysis script(s), but... is it in use?? January 10 2017 Realistic Horns in G4LBNF 4
… Coding the realistic geometry.. No changes in the methodology.. Fired up the Citrix server, ✔ TeamCenter, get to the model #, run Nx9, and do the measurements that are needed.. TeamCenter Doc# entered in the code. Enter the geometry, mostly “hardcoded” in the ✔ LBNEVolumePlacements class. One by one, trying to check every number twice... – Curves ==> Polygonal shape. Conceptual Design Rev1 no longer avialable at run time: if needed, ✔ you'll need to re0build g4lbne from a previous release (v3r4p4 ?.. ) (a good thing a few of us will stay around for the next ~30 years). ✔ January 10 2017 Realistic Horns in G4LBNF 5
Nx9 screen captures... (Horn B) Outer Conductor Current Eq section 1 m. I/O trans. I/O Insulator Inner Conductor January 10 2017 Realistic Horns in G4LBNF 6
.. found wire frame a bit more convenient.. Welds Hanger rings Nx9 has good interactive feature to explore the model...Not all features are implemented in the G4 model: simplified some curve, beveled edges for flanges. Also, drain holes not implemented January 10 2017 Realistic Horns in G4LBNF 7
.. comparison with Geantinos plots.. Nx9 cut view G4lbnf geantinos R/Z plot Spider hanger added.. (NuMI) January 10 2017 Realistic Horns in G4LBNF 8
For sake of completion, HornA. Nx9 cut view G4lbnf geantinos R/Z plot Spider hanger added.. (NuMI) “tapered geometry” January 10 2017 Realistic Horns in G4LBNF 9
Note: The upstream Inner/Outer transition, and associated flanges, are crudely represented in G4blnf, simply because they upstream of the starting point of the target. The 4 titanium tubes that support the downstream end of the target, and provide Helium gas for cooling are not shown in the previous slide, but are implemented in the both the NX9 and G4lbnf models. January 10 2017 Realistic Horns in G4LBNF 10
Horn C. G4lbnf geantinos R/Z plot Current equalizer sections, Spider hanger upstream added.. (NuMI) January 10 2017 Realistic Horns in G4LBNF 11
Neutrino (in neutrino mode) spectrum, far detector. Idealistic vs Realistic Simply replace the Idealistic (as taken of the “run26_8079_NumiTarget” from Laura). All horns are either “ideal” shape (polygonal, from the optimizer) or Realistic (Nx9 models) . All realistic horns are revision 2. January 10 2017 Realistic Horns in G4LBNF 12
The target is always “engineered”, see Cory Crowley's DUNE DocDb note 1923-v2. All Horns are at Rev 2 (Team Center document #F10068454, #F10071359, #F10071767) respectively. These Ideal horns were obtained via the Laura's optimization procedure, based on a genetic algorithm. However, the Horn A IC downstream radius that was found to be too DUNE-doc-1923-v2 small to accommodate for the NuMI style target. We had to increasse it from 21 mm to 33 mm. This new “ideal” horn A is the basis for the results shown in this talk. (Early version presented at the Beam Simulation meeting on Friday Dec. 16 2016 had that radius at 21 mm). As shown later, this is a critical design parameter for Horn A, for the neutrino spectrum at 4 to 5 GeV. We now compute the ratios, Realistic (a.k.a. engineered) over Idealistic. January 10 2017 Realistic Horns in G4LBNF 13
Neutrino (in neutrino mode) spectrum, far detector, ratio Realistic (a.k.a engineered) / Idealistic Loss due Gain due to increase realistic sim”: of focusing power absorption In realistic sim. Big effect in the 4 to 6 GeV region, as anticipated by Laura.! We have a bit more focusing power in HornA, as seen later. As pointed by Mary B., not good news for systematics, if we expect new physics in this energy range. January 10 2017 Realistic Horns in G4LBNF 14
Details needed! One Horn is “Ideal”, two “Real” Here, the black square curve is the same as the previous slide. We then study the case (colored curve) where we compute the ratio of flux, between the partial realistic scenario, where only one horn is idealized. The denominator is always “All Horn ideal”. Horn A shape and field integral seems to matter most for E ~ 3.5 GeV/c. The trailing edge of the focusing peak (5 GeV) is gone when Ideal Horn A is used. January 10 2017 Realistic Horns in G4LBNF 15
An other way to compare.. : One horns “realistic”, two “idealized” Indeed, the focusing difference at 3.75 and 5. GeV is due to HornA shape difference, most likely at small radius, downstream section of the IC & IO transition. Is this worth addressing ? Overall, as we added material with the realistic version, we loose neutrinos at low energy, in the focusing peak, and gain quite a a tiny bit at high energy (5 Gev). January 10 2017 Realistic Horns in G4LBNF 16
Impact on the Near to Far ratio. This is the ratio of ratios previously shown, Near over Far. As expected, Horn A shape change induced a signficant effect at 2.5 GeV. And, as shown in previous slides, a bigger “oscillation” at 4.5 GeV/c January 10 2017 Realistic Horns in G4LBNF 17
Probable Root Cause: Focusing changes: Effective magnetic length of horns.. Ideal vs realistic.. Horn B Horn A Geantino plot. In the ideal version, the I/O transitions region are much simplified, they are nearly vertical lines. We (Cory C. ? ) could compromise and reduce a bit the length of the IC, to match the same B.dl that enter (or leaving) the I/O transition.. Or, more simply, adjust to the distance between Horn A and Horn B. Then study the sensitivity of the Near/Far versus these parameters. January 10 2017 Realistic Horns in G4LBNF 18
Here, went back the the simplified cylindrical target that fits into the strongly tapered Horn A. We vary the radius of this tapered section, from 21 mm to 33 mm. (The target had a radius of 14 mm, which is very thicvk, but it should not affect our conclusion) The gain at 5 GeV can indeed be very strong.. January 10 2017 Realistic Horns in G4LBNF 19
Here, we vary the distance between Horn B and Horn A. The “nominal” distance (via G4UI data card) is set to 2900., where the start of horn A defined as the position of the start of the IC. The size of the induced “oscillation” in the spectrum is about 1 % per 5 cm. Since the mechanical/survey tolerance will be at least 10 time better, we are O.K. January 10 2017 Realistic Horns in G4LBNF 20
Here, we vary the longitudinal distance between the target and Horn A. The denominator corresponds always to the “nominal” position of the target, whose most upstream fins is aligned with respect to the field region of the horn. Positive Dz corresponds to moving the 2m. Long target into the horn. If so, high energy pions, produced at relatively small angles are no loger focused, and one loose yield for neutrino energy of 5 GeV. January 10 2017 Realistic Horns in G4LBNF 21
Effect of downstream target support.. <~ 1 % change across the spectrum! Perhaps sensible: In the focusing peak, pions at a bigger radii than the bulk of the support, which at a Radius of ~ 40 mm. Not affected.. At higher energy production of pions that can be focused by HornC do compensate the absorption. And, of course, no magnetic effects. January 10 2017 Realistic Horns in G4LBNF 22
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