Beam Tests of Ionization Chambers for the NuMI Neutrino Beam Monitoring System MINOS

The MINOS Experiment Near Detector: 980 tons Far Detector: 5400 tons Long Baseline Neutrino Oscillation Experiment  beam and directed down into the Earth Position a detector near to the beam and observe the spectrum (Near Detector) Place another detector 730 km away and observe the spectrum (Far Detector) Comparison of the spectra reveals the oscillation signature Near Detector: 980 tons Far Detector: 5400 tons Det. 2 Det. 1

The NuMI Beamline 2.5 x 1013 protons per pulse (120 GeV) 9.6 ms pulse length 1.9 s cycle time  250 kW Beam Power ~ 4 p+ created per proton incident on C target Focus 4-10 GeV p+ (makes 1-5 GeV nm) ~ 2000 nm CC events / year in Far Detector ~ 107 nm CC events / year in Near Detector Monitors see up to 109 charged particles / cm2 / spill 120 GeV p

An Ionization Chamber - The PIC Pad Ionization Chamber Parallel Ceramic Plates plated with Ag & Pt Plates separated by distances of 1 - 5 mm with ceramic washers Positive High Voltage is applied to the HV plane Charge is collected on the sense plane A guard ring surrounds the sense pad and provides a more uniform field Uses a He or 98% He, 2% H2 gas at 1 atm. and room temperature Sense HV

The Beam Test Put 2 PICs into FNAL Booster beam Radiation Damage Facility provides 8 GeV protons @ 0.1 - 4 x 1012 protons/spill Protons delivered in a 5 cm2 spot in 1.56 ms Test 1 & 2 mm plate separations Segmented Ionization Chambers measure the horizontal and vertical profiles

Intensity Response

Simulating a Chamber

Simulation Details

Intensity Plots

Gain Plots 250 V 200 V 150 V 100 V

Plateau Curves

Leftovers