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The PrimEx-I Beam line

Analysis of beam line configurations for PrimEx-II with varying magnet and shield settings to optimize particle background reduction and efficiency. Results suggest ideal setups for photon and charged particle distributions.

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The PrimEx-I Beam line

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  1. The PrimEx-I Beam line

  2. MC Results for the PrimEx-I configuration Beam Background on HyCal: Energy Distribution (arbitrary numbers) (Photons)/(All)=(50,250/72,980) = 69% (Charged Part.)/(All)=(22,730/72,980) = 31% Charged particles dominate at E> 1 GeV Photons dominate at E < 1 GeV Pay attention the Y-scale is LOG PrimEx-II Beam Line, August 5, 2010

  3. MC Results for PrimEx-I confogureation: Beam Background on HyCal: XY Distribution (for illustration) Charged Particle Distribution on HyCal Photon Distribution on HyCal PrimEx-II Beam Line, August 5, 2010

  4. Step #1: What if we take the Permanent Magnet off from the beam line?(Charged Particles only, for now) Effect of the Permanent Magnet Field On the CHARGED background: Bperm=0 KG, total Number=42,680 (188%) Bperm=7 KG (the Current)= 22,730 (100%) Bperm=14 KG (doubled) = 7,769 (34%) Conclusion #1 Permanent magnet effectively cuts the Charged background at less than ~1 GeV range. Total efficiency is a factor of 2. We need Permanent Magnet!!! PrimEx-II Beam Line, August 5, 2010

  5. Step #1: What if we take the Permanent Magnet off from the beam line?(All Particles now) Effect of the Permanent Magnet Field on all particle background: Bperm=0 KG, total Number=95,170 (130%) Bperm=7 KG (the Current)=72,980 (100%) Bperm=14 KG (doubled) = 47,600 (74%) Conclusion #2 Permanent magnet does not cut the Photon component of the background. But, the total net effect is ~30% reduction for 7KG We need Permanent Magnet!!! PrimEx-II Beam Line, August 5, 2010

  6. Step#2: Different Diameter Pb-Shieldings(Bperm=7KG (current one), for now) Charged Particles Effect of the Pb-shield diameter on charged particle background: Diam.= 2.5”, total Number=32,050 (141%) diam.=1.53”(the Current) =22,730 (100%) diam.=0.8” = 8,801 (39%) Conclusion # 3 Pb-shield effectively cuts the Charged background at less than ~2 GeV range. Total efficiency is about factor of 2.5 We need smaller diam. Pb-shielding!!! PrimEx-II Beam Line, August 5, 2010

  7. Step#2: Different Diameter Pb-Shieldings(Bperm=7KG (current one) for now) Photons Only Effect of the Pb-shield diameter on Photon background: Diam.= 2.5”, total Number=56,160 (112%) diam.=1.53”(the Current) =50,250 (100%) diam.=0.8” = 28,970 (58%) Conclusion # 4 Smaller diam. Pb-shielding effectively cuts the Photon background also. Total efficiency: factor of ~2 We need smaller diam. Pb-shielding!!! PrimEx-II Beam Line, August 5, 2010

  8. Background Relative Composition for 0.8” Pb-Shild and Bperm = 0 KG Relative composition of particles for 0.8 inch diam. Collimator and Bperm = 0 KG All particles > 0.1 GeV (57,330) 100% Photons (33,120 58% Charged particles (24,210) 42% Conclusion # 5 For this case Photon to Charged Ratio is about 50:50 Try to increase the Permanent Magnet !!! PrimEx-II Beam Line, August 5, 2010

  9. Effect of Bperm on Charged Background for 0.8” diameter PB-Shielding Relative cut efficiency of the Permanent Magnet for the fixed collimator (0.8 inch diam.) B(perm. m.) = 0 KG 100% B(perm. m. ) = 7 KG 36% B(perm. m.) = 14 KG 10% B(perm. m.) = 21 KG 5% Conclusion # 6 For 0.8” Pb-shielding 7 KG or more field in permanent magnet is needed. We need smaller diam. Pb-shielding And higher Bdl permanent magnet !!! PrimEx-II Beam Line, August 5, 2010

  10. XY-Distribution on HyCal for 0.8 “ Pb-Shielding (Bperm = 0 KG) Photon Distribution on HyCal Charged Particle Distribution on HyCal PrimEx-II Beam Line, August 5, 2010

  11. XY-Distribution on HyCal for 0.8 “ Pb-Shielding (Bperm = 7 KG) Photon Distribution on HyCal Charged Particle Distribution on HyCal PrimEx-II Beam Line, August 5, 2010

  12. XY-Distribution on HyCal for 0.8 “ Pb-Shielding (Bperm = 14 KG) Photon Distribution on HyCal Charged Particle Distribution on HyCal PrimEx-II Beam Line, August 5, 2010

  13. Conclusion # 7 MC simulations show that the optimum configuration for the PrimEx-II Beam line is: Pb-shielding with the 0.8” diameter hole; Permanent magnet with either one element (7KG) or two (14 KG) Next question is: do we gain if we try to extend the distance from Collimator to Pb-shielding ? PrimEx-II Beam Line, August 5, 2010

  14. Effect of Moving Down the Target and PS (+50 cm) on Beam Backgroundfor 0.8” diameter Pb-Shielding, All Particles Relative cut efficiency of the Permanent Magnet for the fixed collimator (0.8 inch diam.) PrimEx-I Conf., Bperm=7 KG 100% +50 cm, Bperm = 7 KG 41% +50 cm, Bperm =14 KG 35% Conclusion # 7 For 0.8” Pb-shielding 7 KG or more field in permanent magnet is needed. We need smaller diam. Pb-shielding And higher Bdl permanent magnet !!! PrimEx-II Beam Line, August 5, 2010

  15. Effect of Moving Down the Target and PS (+50 cm) on Beam Background for 0.8” diameter Pb-Shielding, Charged Particles Conclusion # 8 We need smaller diam. Pb-shielding And higher Bdl permanent magnet !!! PrimEx-II Beam Line, August 5, 2010

  16. Effect of Main Collimator “Tapering” on Background Charged Particles, 14 KG Everything is the same as was in the Previous slide only the down half of the Permanent magnet is “tapered” by 1 mm Relative efficiency of the main Collimator PrimEx-I Conf., + 50 cm down, Bperm=7 KG existed collimator 100 % 1 mm tapered collimator 74 % Conclusion # 9 Tapered Collimator is better PrimEx-II Beam Line, August 5, 2010

  17. Effect of Main Collimator “Tapering” on Background Photons, 14 KG Everything is the same as was in the Previous slide only the down half of the Permanent magnet is “tapered” by 1 mm Relative efficiency of the main Collimator PrimEx-I Conf., + 50 cm down, Bperm=7 KG existed collimator 100 % 1 mm tapered collimator 65 % Conclusion # 10 Tapered Collimator is better PrimEx-II Beam Line, August 5, 2010

  18. Effect of Main Collimator “Tapering” on Background All Particles, 14 KG Everything is the same as was in the Previous slide only the down half of the Permanent magnet is “tapered” by 1 mm Relative efficiency of the main Collimator PrimEx-I Conf., + 50 cm down, Bperm=7 KG existed collimator 100 % 1 mm tapered collimator 65 % Conclusion # 10 Tapered Collimator is better PrimEx-II Beam Line, August 5, 2010

  19. Effect of Main Collimator “Tapering” on Background All Particles, 21 KG Everything is the same as was in the Previous slide only the down half of the Permanent magnet is “tapered” by 1 mm Relative efficiency of the main Collimator PrimEx-I Conf., + 50 cm down, Bperm=7 KG existed collimator 100 % 1 mm tapered collimator 58 % Conclusion # 10 Tapered Collimator is better PrimEx-II Beam Line, August 5, 2010

  20. Effect of Main Collimator “Tapering” on Background All Particles, 21 KG, 2 mm “tapering” Everything is the same as was in the Previous slide only the down half of the Permanent magnet is “tapered” by 1 mm Relative efficiency of the main Collimator PrimEx-I Conf., + 50 cm down, Bperm=7 KG existed collimator 100 % 1 mm tapered collimator 63 % Conclusion # 11 1mm wall tapered Coll. is enough! PrimEx-II Beam Line, August 5, 2010

  21. Final Comparison of Background Net GainAll Particles The old PrimEx-I configuration vs. the Suggested new PrimEx-II configuration: (+50 cm, 21 KG perm. mag, 1mm tapered Collimator) Relative gain: PrimEx-I conf. 100 % sugg. PrimEx-II conf. 19 % Conclusion # 12 We expect ~5 times less background! PrimEx-II Beam Line, August 5, 2010

  22. Final Comparison of Background Net GainAll Particles The old PrimEx-I configuration vs. the Suggested new PrimEx-II configuration: (+50 cm, 21 KG perm. mag, 1mm tapered Collimator) Relative gain: PrimEx-I conf. 100 % sugg. PrimEx-II conf. 19 % Conclusion # 12 We expect ~5 times less background! PrimEx-II Beam Line, August 5, 2010

  23. Effect of Z-distance on HyCal backgroundNo Physics Target(All Particles) The Target and PS moved down for 32 cm Relative Change: PrimEx-I Zdist. 100 % sugg. +32 cm PS down 105 % Conclusion # 13 Practically no change in background PrimEx-II Beam Line, August 5, 2010

  24. Effect of Z-distance on HyCal backgroundNo Physics Target(Charged Particles) The Target and PS moved down for 32 cm Conclusion # 14 Practically no Charge Particle contribution in background PrimEx-II Beam Line, August 5, 2010

  25. Summary++ Based on the current Monte Carlo simulations: We do not need to increase the Pb-shielding diameter; The background on HyCal is significantly less for the smaller diameter Pb-shielding; 0.8” diameter is the smallest we can have. It can be done by inserting a ~10 r.l. ring inside of the existing beam pipe (Dave Kashy); “Tapered” main Collimator is another factor of 2 more effective D. Kashy’s suggested version #3 is the best for the PrimEx-II beam line It will potentially reduce the background on HyCal by factor of 5 Interactive Geant shows that +32 cm down for PS is not critical for the 0 run. Detail simulations for this part will be provided in next few days. PrimEx-II Beam Line, August 5, 2010

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