The PrimEx-I Beam line

MC Results for the PrimEx-I configuration. Beam Background on HyCal: 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 A. Gasparian Hall B, June 1, 2009

MC Results for PrimEx-I confogureation:. Beam Background on HyCal: MC Results for PrimEx-I confogureation: Beam Background on HyCal: XY Distribution (for illustration) Charged Particle Distribution on HyCal Photon Distribution on HyCal A. Gasparian Hall B, June 1, 2009

Step #1: What if we take the Permanent Magnet off from the beam line 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!!! A. Gasparian Hall B, June 1, 2009

Step #1: What if we take the Permanent Magnet off from the beam line 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!!! A. Gasparian Hall B, June 1, 2009

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!!! A. Gasparian Hall B, June 1, 2009

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!!! A. Gasparian Hall B, June 1, 2009

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 !!! A. Gasparian Hall B, June 1, 2009

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 !!! A. Gasparian Hall B, June 1, 2009

XY-Distribution on HyCal for 0.8 “ Pb-Shielding (Bperm = 0 KG) Photon Distribution on HyCal Charged Particle Distribution on HyCal A. Gasparian Hall B, June 1, 2009

XY-Distribution on HyCal for 0.8 “ Pb-Shielding (Bperm = 7 KG) Photon Distribution on HyCal Charged Particle Distribution on HyCal A. Gasparian Hall B, June 1, 2009

XY-Distribution on HyCal for 0.8 “ Pb-Shielding (Bperm = 14 KG) Photon Distribution on HyCal Charged Particle Distribution on HyCal A. Gasparian Hall B, June 1, 2009

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 ? A. Gasparian Hall B, June 1, 2009

Effect of Moving Down the Target and PS (+50 cm) on Beam Background for 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 !!! A. Gasparian Hall B, June 1, 2009

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 !!! A. Gasparian Hall B, June 1, 2009

Move down the Target, Pb-Shielding and PS for 50 cm, use that distance 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); With that there are 2 options: Leave the Collimator to Target distance as it is with the existing 7 KG Permanent Magnet; Move down the Target, Pb-Shielding and PS for 50 cm, use that distance to insert one more unit of Permanent Magnet (14 KG total). This is the most desirable option if it is all possible for this short time. A. Gasparian Hall B, June 1, 2009