1. Argon Purity: Fundamentals Where: [e] – electron concentration [S] – concentration of electronegative impurities k s - attachment rate constant [P] – concentration of positive ions k r – recombination rate constant In practice [P] is negligibly small, hence N(t) = N(0)e -t/  with  = 1/(k s [S])

2. Argon Purity monitor

3. Purity monitor: signals In principle In practice (including shaping time of charge amplifier)

4. Purity monitor: system components

5. Drift chamber: geometry

6. Drift chamber

7. System components UV Light source Pulsed (few microsecs) High power Quartz fiber (~ 1mm) High voltage PS (3 kV)/HV filters (3 channels) Low noise charge amplifier [Amptek250?] Waveform digitizer (digital scope) Low voltage PS (for the amplifier) Feed throughs: fiber/signal/HV

8. Accuracy/Sensitivity k – ‘stochastic’ term  light source intensity h – electronic noise term  low noise, high gain amplifier Extending the range: long lifetimes (I wish ) – tracks, dE/dx Shorter lifetimes: shorter detector, O2 standard monitors?