1. Calibration, Simulations, and “Remaining” Issues
J. Jerz
J. Klein
A. Rahman

2. Goal of calibration program:
To make a prediction with uncertainties on the relative number of events counted in each detector (and perhaps in each energy bin)
en = neutron detection efficiencyincludes similar integral+
capture efficiency
ee = cut efficiencies other than E (Dt, Dr, etc.)
Dt = livetime
Ps = survival probability
r = response function for positrons—not necessarily Gaussian!

3. Detector acceptances can differ through:
Number of proton targets
Gd loading fraction
Scintillator response (photons/MeV), including aging effects
Optical Response, including attenuation lengths of media (5 for 3 zone, 3 for 2 zone), angular and wavelength response of PMT’s, Rayleigh scattering, specular and diffuse reflection from all surfaces
Number of working PMT’s, as well as individual gain and efficiencies
Number of working electronics channels, including individual efficiencies
And we need to do this for all positions, times,…

4. Detector Response = distances through media from interaction to PMT i
= 1/attenuation lengths (scattering+extinction)
= Number of photons/wavelength interval and angle for particle of energy E (may be id-dependent)
= PMT response in terms of wavelength and incidence
= channel efficiencies as a function of gain and threshold

5. Some basic calibration questions:
How many zones will we have?
How much self-calibration can be done?
What are `baseline’ optical properties?
How finely do we need to sample positions?
How well do we need to know sampling positions?
How often will we need to calibrate?

6. Prediction (reponse r) must be integrated over:
Time
Event positions (and directions)
Event energies
Particle types (n,e+,e-,g,a,…)

7. Source Types and Systems
SNO radioactive sources:
16N  6.13 MeV ’s
Cf  neutrons
8Li  ’s, E<14 MeV
Low energy radioactive sources
Radon `Spikes’
Other sources:
AmBe  4.44 MeV +neutron
Vetoed cosmics neutrons, spallates
Other spikes  Pb?
Position uncertainty: +/- 5 cm multi-axis
+/- 2 cm single-axis

8. Self-Calibration with Neutrons

9. Self-Calibration with Neutrons

10. Self-Calibration with Neutrons
Small uncertainties
On Dt (~0.3 ms) are
< 1% on acceptance

11. Can neutron tail change independently of mean?
How important are local effects (dead PMT’s, etc.)
Can there be differential non-linearities? (MPE, xtalk, ?)
Can spallation nuclei give us restrictions on above?

12. Loss of gammas creates tail on neutron response
3zone
2 zone

13. Optical measurements from single radial position suffers
from large covariances between media:
Occupancy in PMT j for
calibration run i
If global attenuation changes, which medium is it?
2 zones=3 zones
3 zones=5 zones

14. Parameter Sensitivities

15. Parameter Sensitivities

16. Plans Quickly finish up parameter sensitivity studies
Include systematics and backgrounds for neutron fits
Move simulation further into reality mode 1
Simulation source studies
Calibration system mechanical designs