Details

Autor(en) / Beteiligte

• Thomson, Marcus James

Titel

The (222)Radon Spike source calibration of the Sudbury Neutrino Observatory detector

Ort / Verlag

ProQuest Dissertations Publishing

Erscheinungsjahr

2004

Link zum Volltext

• ProQuest

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• On 20 February 2003 the Radon Spike, a containerless 222Rn calibration source, was added into the SNO detector at the end of the salt phase. The Radon Spike was designed and built from an original concept by SNO researchers. Twenty-six 50 ± 1 mL aliquots of saline, 222Rn-infused D2O were injected in a planar array of approximately equidistant points inside the detector, delivering a total of 81 ± 4 Bq of 222Rn into one kilotonne of ultra-pure, saline D 2O. The results were used to determine the detector's response by location inside the D2O target and the efficiency of Monte Carlo models used to simulate the radon spike. Tagged by dissolved 222Rn, the D2O was seen to circulate and quickly descend toward the bottom of the D2O target. The angular speed of rotation, [special characters omitted], for the first five to eight hours following the spike was 0.20 ± 0.01 rad/hour near the centre of the D2O target to 0.022 ± 0.005 rad/hour near the AV which contains the D2O. The radon spike was found to decay more quickly than would be expected from pure 222Rn. Immediately following the spike, the concentration of 222Rn in the D2O was sufficient to make it possible for 222Rn to escape into the vapour space above the D 2O. The total energy spectrum measured for the 222Rn spike was found to agree with the predicted spectrum when total energy is equal to or greater than 3.8 MeV. Detector spatial asymmetries have been found by dividing the AV into cells of equal volume and analysing their frequency as a function of counts per cell. Asymmetries were found to contribute to a broadening of the (purely statistical poissonian) distribution by approx. 0.33σ events per cubic metre in the AV. This is a measure of the precision we can have on the number of events per cubic metre. Optical efficiency variations in the photomultiplier tubes were found to be at least partially responsible for the spatial asymmetries.