[Paper Review] Study of a New Target Design with an Additional Horn for NuMI Beam

Jyoti Tripathi|arXiv (Cornell University)|Oct 10, 2017

Radiation Therapy and Dosimetry1 references3 citations

TL;DR

This paper proposes a new NOvA target design with graphite fins inserted into Horn 1 and an additional identical Horn 2 placed at 6 m and 16 m along the stripline to enhance neutrino yield. Simulations show a 21.7% gain in $ν_{\mu}$ events at the Far Detector and a 25.4% gain in $ν_e$ contamination reduction, with optimal performance in both FHC and RHC configurations, without shifting the neutrino spectrum peak.

ABSTRACT

This paper describes the simulation studies done for the standard NOvA target and the proposed new minimal NOvA target design, in forward and reverse horn current for studying the neutrino and antineutrino event yield and the background contamination at the near and far detector. The standard NOvA target is segmented into 48 graphite segments (fins) with two magnetic horns, Horn 1 placed at MCZERO and Horn 2 placed at 19.18 m from MCZERO. The new minimal target design has 24 graphite fins extended into Horn 1. It shows the study for the position optimization of the Horn 2 relative to Horn 1 for the standard and the new minimal target design. The effect of introducing an additional horn (identical to Horn 2) with the new minimal target design, on the neutrino yield and the energy spectra, has also been explored.

Motivation & Objective

• To increase neutrino yield in the NOvA experiment by redesigning the target to be inserted into the magnetic horn for improved focusing.
• To evaluate the impact of placing an additional Horn 2 (identical to existing Horn 2) along the stripline to refocus low-energy pions overfocused by Horn 1.
• To optimize the position of the second Horn 2 relative to Horn 1 and the new target design for maximum neutrino flux gain.
• To assess the feasibility and performance of the new minimal target design under high-proton-on-target conditions.
• To quantify improvements in $ν_{\mu}$, $υ_{\mu}$, and $ν_e$ event yields and contamination levels compared to the standard target and horn configuration.

Proposed method

• Used the FLUGG simulation framework integrating Geant4 geometry with FLUKA physics models to simulate particle interactions and decays in the NuMI beamline.
• Modelled the new minimal target with 24 upstream fins (unchanged from standard) and 24 downstream fins (reduced height to 17 mm) inserted into Horn 1 for improved beamline integration.
• Simulated the beamline with a 1.1 mm beam spot, 200 kA horn current, and 6×10^20 protons on target, scaling results for comparison.
• Placed two identical Horn 2s at varying positions (6 m and 16 m) to study refocusing of pions exiting at large angles from Horn 1.
• Scanned the position of the second Horn 2 relative to the first and Horn 1 to identify optimal configuration for maximum neutrino yield.
• Compared event yields and energy spectra for $ν_{\mu}$, $ν_e$, $υ_{\mu}$, and $ν_e$ contamination between standard and new target designs in both FHC and RHC modes.

Experimental results

Research questions

• RQ1 What is the gain in $ν_{\mu}$ event yield at the Far Detector when the new minimal target design is used with Horn 1 only?
• RQ2 How does introducing an additional Horn 2 at optimized positions affect the neutrino flux and spectrum shape compared to the standard configuration?
• RQ3 What is the improvement in $ν_e$ contamination and $ν_{\mu}$ yield when the new target is used with dual Horn 2s in FHC and RHC modes?
• RQ4 Does inserting the target fins into Horn 1 preserve the peak position of the neutrino energy spectrum while increasing yield?
• RQ5 What is the optimal placement of the second Horn 2 relative to the first and Horn 1 for maximum neutrino yield in the new target design?

Key findings

• The new minimal target design increases $ν_{\mu}$ event yield by 11.5% at the Near Detector and 11.3% at the Far Detector in FHC configuration compared to the standard target.
• With the addition of a second Horn 2 placed at 6 m and 16 m, the $ν_{\mu}$ event yield increases by 21.7% at the Far Detector, with a 25.4% gain in $ν_e$ contamination.
• The $ν_{\mu}$ energy spectrum peak remains unchanged when using the new target design, indicating no spectral distortion despite increased yield.
• In RHC configuration, the new target with dual Horn 2s yields a 24.7% gain in $υ_{\mu}$ at the Near Detector and a 22.8% gain at the Far Detector, with a 36.4% increase in $ν_e$ contamination.
• The optimal configuration for maximum $ν_{\mu}$ yield places the first Horn 2 at 6 m and the second at 16 m from MCZERO, outperforming standard and single-Horn 2 configurations.
• The new target design increases $ν_e$ event yield by 29.6% at the Near Detector and 30.2% at the Far Detector in FHC, indicating improved sensitivity to $ν_{\mu} \to \u03bd_e$ oscillations.