Freeze-In and Hole Ice Studies with Flashers Michelangelo D’Agostino UC Berkeley Baton Rouge Collaboration Meeting April 9, 2006

Outline description of the analysis a first quick-and-dirty look at the data: can we see the freeze-in and transition to hole ice in string 39 data? comparison to simulation future work more “exploration” than “verification”

Analysis for string 39, a set of flasher runs was taken just after deployment, in water, and repeated at various later times data for DOM’s 4, 12, 18, 19, 36, 40, 42, 48, 54, and 55 two types: INTRA-TDEP—flash the 6 horizontal and 6 tilted LED’s separately INTRA-1LED—flash each of the 12 LED’s individually also wet string flashing to frozen string receiving and vice versa (haven’t looked at these)

Analysis as a first test, let’s look at the average calibrated ATWD waveform in the DOM above the flasher (Chris Wendt’s idea) for each waveform, feature extract the leading edge line up all the leading edges in the same bin and take an average of 500 this method throws out any relative timing information, which might also be useful

Results note the scales: many fewer PE’s for horizontal LED’s, as expected 6 Tilted LED’s Only 6 Horizontal LED’s Only DOM 39-18 Jan. 5 (black) at 4 C vs. Feb. 10 at -25  C (green)

Results statistically significant 6 Tilted LED’s Only 6 Horizontal LED’s Only statistically significant general trend: fewer PE’s for tilted LED’s and same or more PE’s for horizontal LED’s DOM 39-18

Integrated Charge variation with depth is an ice properties effect (cf. simulation) 6 Tilted LED’s Only for all DOM’s but 1, the in ice data shows lower charge, as we could see from the waveforms

Integrated Charge 6 Horizontal LED’s Only less of a clear trend; for quite a few, later data shows more charge

Integrated Charge Is this an effect of hole ice, or of something systematic? Possibly a temperature effect?

Single LED DOM 39-19 Horizontal LED’s Vertical LED’s Pair 1 Pair 2

Horizontal LED’s Vertical LED’s Pair 1 Pair 2 Pair 3 Pair 4 Pair 5 Pair 6 -variation depends on azimuthal angle around the DOM -vertical and horizontal LED’s at the same azimuth show a similar level of variation between water and ice -smoking gun: this is not a systematic or temperature effect on the PMT or electronics; it’s a physical difference between the water and the ice

Photonics Simulations hacked photonics to include hole ice scattering around a 12 LED flasher board source includes the best understanding we have of the fully layered ice get the bare probability distribution as a function of time (no PMT or waveform simulation); since the data has very many PE, it should be decently close to the PDF 2 sets: 1 with no hole ice scattering 1 with a 30 cm diameter cylinder of 10 cm, 50 cm, and 100 cm effective scattering length hole ice

Photonics Simulations 6 Tilted LED’s Only 6 Horizontal LED’s Only DOM 18 less charge with hole ice same or more charge with hole ice

Photonics Simulations 6 Tilted LED’s Only hole ice shows less charge variation with depth like in the data

Photonics Simulations 6 Horizontal LED’s Only hole ice shows same or more charge, quite like the data

Interpretations seems to be a strong case for saying that we can see the freeze-in transition to hole ice: data is consistent with highly scattering hole ice hole ice has 2 effects: scatters light out of the tilted LED beams and results in less charge increases the acceptance of the receiving DOM for the horizontal LED’s resulting in the same or more charge the hole ice scattering is not azimuthally symmetric

Future Work look at waveforms in other DOM’s up and down the string FADC waveforms? need full detector Monte Carlo to make more realistic comparisons the ratio of charge for tilted LED runs to charge for horizontal LED runs varies with the hole ice scattering length in the simulation (i.e. hole ice isotropizes the light output); use this to say something more quantitative

Results 6 Tilted LED’s Only 6 Horizontal LED’s Only Jan. 5 at 5  C (black) vs. Jan. 13 at -21 C (blue) vs. Feb. 10 at -27  C (green) DOM 39-12

Results 6 Tilted LED’s Only 6 Horizontal LED’s Only DOM 39-36

Results 6 Tilted LED’s Only 6 Horizontal LED’s Only DOM 39-42

Results 6 Tilted LED’s Only 6 Horizontal LED’s Only DOM 39-48

Results 6 Tilted LED’s Only 6 Horizontal LED’s Only Jan. 5 at 3  C (black) vs. Jan. 13 at -1  C (blue) vs. Feb. 10 at -11  C (green) DOM 39-54