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

2. 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

3. 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

4. An Ionization Chamber - The PIC
Pad Ionization Chamber
Parallel Ceramic Plates plated with Ag & Pt
Plates separated by distances of 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

5. The Beam Test Put 2 PICs into FNAL Booster beam
Radiation Damage Facility provides 8 GeV 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

6. Intensity Response

7. Simulating a Chamber

8. Simulation Details

9. Intensity Plots

10. Gain Plots
250 V
200 V
150 V
100 V

11. Plateau Curves

12. Leftovers