Comissioning the NuMI Beam at Fermilab with Ion Chamber Arrays

1. Uncorrected Corrected horn baffle target ±1% Hadron Monitor Installed on a dual-rail support structure with remote-handling capability mMon Center Pixel • Measures intensity and position of the remnant hadrons from the primary proton beam • Max flux ~1E9/cm2/spill, ~2E9 Rad/yr mMon Chamber ppp On Target ppp On Target ppp On Target ppp On Target Operating at 300V Center Pixel Signal (Arb) • 7x7 IC array, 1mm electrode separation • Components Rad Tested up to 12GRad (6 NuMI years) HadMon Center Pixel ppp On Target 32” ppp On Target ppp On Target HadMon Chamber ppp On Target Operating at 190V Center Pixel Signal (Arb) Water level indicated by beam instrumentation after efforts to drain target in place, confirmed with boroscope Chambers Increased intensity  slower turnon Tray 241Am a source Kapton Cables Beam Intensity (E12 ppp) No change in charge collection efficiency above 40V Ion Chamber Calibration Water leak in the cooling line • Monitors flushed with He gas • Each chamber mapped with 1Ci g-source (241Am, 30-60keV) • Press. & Temp calibration developed Beam RMS spread from multiple scattering • 1% relative calibration Plateau currents for 288 muon chambers Comissioning the NuMI Beam at Fermilab with Ion Chamber Arrays M. Bishai, M. Diwan, B. Viren Brookhaven National Lab D. Naples, D. Northacker, J. McDonald Dept. of Physics, University of Pittsburgh A. Erwin, H. Ping, C. Velissaris Department of Physics, University of Wisconsin – Madison D. Indurthy, R. Keisler, S. Kopp, S. Mendoza, M. Proga, Z. Pavlovich, R. Zwaska Department of Physics, University of Texas – Austin D. Harris, A. Marchionni, J. Morfin Fermi National Accelerator Laboratory Horn Studies Beam Based Target & Baffle Alignment Muon Monitors In the LE position, horn-target positions are tuned to focus mainly lower energy p’s(4-6GeV) 2E7/cm2/spill .5E7/cm2/spill 4E7/cm2/spill • Rail system allows variable positioning of the target w.r.t the horns  focusing different energies • 3 target positions: Low energy (LE), medium energy (ME), high energy (HE) Beam’s Eye View • In LE position, horns focus LE (4-6GeV) p’s only Graphite target Increased horn current  increased numbers of focused pions Graphite protection ‘baffle’ Water cooling line 210m • Scans to align the target • Beam translated horizontally across the target/baffle • Measure integrated charge in the downstream monitors • Shape of Monitor Signal v. Beam Position on Target curve used to characterize target alignment • Peaks correspond to target apertures • Asymmetry.25mm target misalignment w.r.t. baffle • Target center @ 1.25mm beam-left, 1mm high (vertical scans not shown). • Beam Instrumentation Performance Studies In-Beam Profiles Horizontal 2D projections provide beam centroid alignment to better than 100mrad off the target Hadron Monitor Vertical HE Position Muon Monitors LE Position HV connections Aluminum Wire Gasket Horizontal • 3 stations at 740,750,770m • Dolomite rocks screens lower energy particles, so subsequent alcoves see higher energy muons • 9x9 array ceramic IC’s (3mm gap) • Measures position & intensity of tertiary muon beam downstream of the absorber Total Charge (Arb) Beam through the apertures  more non-interacted protons @ the HM Total Charge (Arb) Baffle Baffle Baffle Baffle Target Target Signal connections HE Position Muon Monitor LE Position Target Vertical HE position  more peaked mMon profiles Total Charge (Arb) Total Charge (Arb) Baffle Baffle Beam through the apertures produce deficits of muons @ the alcoves Target Baffle Baffle Beam on Baffle yields muons focused by horns LE Position Target Leak & Recovery HE Position Vertical Target Scans No Water • Leak discovered in mid-March • Resumed running in Apr. • Target scans used to diagnose water level in target After effort to drain in place Total Charge (Arb) All alcoves sensitive to horns with the HE beam Total Charge (Arb) Water fills most of target Baffle Baffle Target Target Baffle Baffle Target fully drained Attenuation from water Beam Monte Carlo of Vertical Target Scans LE Position No water HE Position Total Charge (Arb) Increasing Slope  intermediate water level Total Charge (Arb) • Water fills target Baffle Baffle Target Target Baffle Baffle Vertical beam Position (mm)