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

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!

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,…

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

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?

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

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

Self-Calibration with Neutrons

Self-Calibration with Neutrons

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

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?

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

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

Parameter Sensitivities

Parameter Sensitivities

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