ICRR nWS.. 2011 Mar.

Calibrations inIceCube
Akiko Kawachi
Tokai Univ.
for IceCube Collaboration

1km Cubic Detector

1450m

2450m
60 optical sensors
On each string

Systematics ?
• Detector Uncertainties•Sensors• absolute & relative efficiencies• charge response & waveforms• timing• Geometry• Ice Property• absorption /scattering• Systematics in Analysis• Theoretical Uncertainties

Detector Uncertainties andCalibrations• Detector Uncertainties•SensorsLab.
• absolute & relative efficiencies• charge response & waveforms• timing• Geometry• Ice Property•absorption /scattering
In Situ.

Sensors: Digital Optical Module• local coincidence• degitizers• “flasher” Unit• Hamamatsu R7081-02(10”)• 10 dynodes, ~1.5kV : gain ~10^7• single p.e. sensitivity

Lab. Calibrations for Modeling

Single p.e. response

PMT & DOM acceptance vswavelength
2d cathode response
Abbasi et al., (2010)NIMPA 618 pp.139.

In Situ Calibrations & Light Sources•Sensors• absolute & relative efficiencies• charge response & waveforms• timing• Geometry• Ice Property•absorption /scattering
In Situ.

•Flashers•“Standard Candles”•Downgoing muonsFlashers:
Upward pointing
LEDs
Horizontal
LEDs• Twelve violet (405nm) LEDs at each DOM• brightness & width variable : max. ~9e10 photons• flashing pattern variableFlash and measure everywhere :(a) intra-string Geometry

ΔｚPeak D

depth

Absorption coefficient [m-1]

Effective scattering coefficient [m-1](b) Ice Property：AMANDA Result

wavelength
2300 m•scattering on bubbles, dust grains•Absorption by ice, dust grains•Layer structure
Ackerman et al., (2006), J.Geophys.Res.111,D13203

Flasher data: Likelihood minimizationfits to get Ice parameters
 “SPICE” model

Compare waveforms w/ simulation to iterate coef.
Based on the works of Dima Chirkin

In Situ Calibrations & Light SourcesWide propagation of photons•Sensors• absolute & relative efficiencies
For UHE events• charge response& waveforms• timing  energy scale calibration
 saturation• Geometry• Ice Property•absorption /scattering
In Situ.

•Flashers•“Standard Candles”•Downgoing muons

“Standard Candle”s:Filter
Nitrogen
Laser

Reflectivecone• Nitrogen (337nm) pulse lasers w/ optics & electronics• Brightness absolutely calibrated and variable
input : 2e11- 4e12 ph (SC-I) / 1.7e10- 2.5e13 (SC-II)~ 1-100PeV n e cascade events

“Standard Candle” Runs

Standard Candle Ⅰ
2007-Sep.

Peak D

Standard Candle II2008-Jun.
5763 55 64

SC Events: How they lookSC2 10% : Data
Depth[m]Peak Dsaturated
Radial distance [m]104102

Peak D

Response near saturation:

Data
MCStr.55-D42

NPE Response vs input photon

6VSignal voltage [mV]

DataMCTime – flasher time [nsec]

Sensitive to Ice property models(1):saturated

Data
MC: model1(aha)
MC: model2 (spice1)

Depth (m)Deviation between models and data depends on layers.

Sensitive to Ice Property Model(2)MC2(spice1)

Data/MC2(spice1)

Data
Depth (m)1

MC1(aha)X-Y(m)

Data/MC1(aha)1Deviation of “Total NPE” estimation
SC2 10% 2.1e12ph:200e3(data-MC)/MC : -14.4% (aha): -17.6% (spice1)

SummaryIn order to understand the detector uncertainty,lab and in-situ calibrations to obtain fundamental
calibration quanta have been done by IceCubegroup.
Study with the known light sources are on-goingand offer/examine more precise modeling ofsensor s & ice.