1. Probe background, technology, calibration, MCNP D ARIN D ESILETS Hydroinnova

2. The instrument: CRS-1000 Darin Desilets 2 80 cm Bare tube (secondary sensor) Moderated tube (primary sensor) Charge controller and 30 Ah battery Data logger Pulse module Connection to Iridium or cell phone

3. The instrument: CRS-1000/B Darin Desilets 3 Pulse module Bare or moderated tube inside 130 cm Charge controller and 30 Ah battery Data logger Connection to Iridium or cell phone antenna

4. Comparison Darin Desilets 4 Tradeoffs size/weight long-term performance power consumption sensor cost expandability protection from moisture Sensitivity to soil moisture CRS1000CRS1000/B

5. Same sensitivity? Darin Desilets 5 major rain event

6. Neutron scattering theory Darin Desilets 6  s (barns)  (-) H20.01.00 C4.80.16 O4.20.12 Si2.00.07

7. Neutron scattering theory Darin Desilets 7 E < 0.1 eV E > 10 eV Moderated tube Bare tube

8. Energy sensitivity for moderated and bare detectors Darin Desilets 8

9. Why use bare counter? o Built-in pressure/solar activity correction o Provides long-term check on stability o Separate snow from soil moisture (?) o Basic research – Canopy snow and water – Biomass o Added issues: – Presence of local absorbers (no universal cal!) – Some very local responses – Greater depth penetration? Darin Desilets 9

10. Bare counter enhancements? Darin Desilets 10 Kerplop! Bare Moderated

11. Improved uncertainty for soil moisture determinations o Limiting case 1: bare tube has same sensitivity to soil moisture as moderated tube. Add counting rates, reduce  stat by ~40% o Limiting case 2: bare tube has low sensitivity to soil moisture Use bare to reduce  syst Darin Desilets 11   total=   stat +   syst

12. Modeling neutrons with MCNP o Monte Carlo Neutral-Particle o The original Monte Carlo application o Remains the “gold standard” for neutron transport o Flexible source specification, geometries, tallies o Overkill? Maybe so Darin Desilets 12

13. Summary o Current configuration is optimized for COSMOS—but other configurations are possible. o Bare counter: not critical but has certain advantages when used with mod tube. o MCNP code: an essential tool for basic research with the cosmic-ray probe. Darin Desilets 13