General performance of General performance of the IceCube detectorthe IceCube detector

and and the calibration results the calibration results

Mina InabaMina Inaba11 S.YoshidaS.Yoshida1 1 , K.Mase, K.Mase11, C.Rott, C.Rott22 ,Y.Hasegawa ,Y.Hasegawa11

1.Dept. of Physics, Chiba University1.Dept. of Physics, Chiba University2. Pennsylvania State University2. Pennsylvania State University

for the IceCube Collaborationfor the IceCube Collaboration

PD 07 @ Kobe Univ. 06/29/2007

Outline

• Introduction of the IceCube experiment• General performance of the IceCube detector• PMT/DOM Production Procedure• Calibration of PMT• Calibration of DOM• Comparison between PMT and DOM• Detector status in the ice• Summary and future work

South pole

IceCube

1 km

The IceCube experiment

~1 km

AMANDA-IIIceCube

1km3

IceTop

〜 1 km

1450m

2450m

• Cherenkov light detector

• 60 PMTs x >70 strings = >4200 PMTs

• Neutrino energy of 107(SNs)-1020eV is detectable.

• 22 strings are deployed up to now, and taking data as the biggest neutrino detector.

Module of the IceCube

PMT HV Base Board

Flasher board

Magnetic Shield Cage

Optical gel

Glass Pressure Sphere

Onboard capture of PMT waveforms

• - ATWD : 300MHz 14 bits (~400nsec) 3 different gains (x16, x2, x0.25)• - FADC : 40MHz 10 bits (~6.4μsec)

Digital Optical Module (DOM)

35.6cm

10inch R7081-02 PMT

Hamamatsu

Typical digitized waveform

General performances of the PMT

Dynamic range

•Type R7081-02 　 (bialkali)•Dynode 10 stages•Quantum efficiency 25% @420nm•Dynamic range 1000p.e. /30nsec @107 gain•Time resolution 2.2nsec•Noise rate 300Hz @ -40 ~ -20℃ ℃•Operation gain 1x107 @1300V

Noise rate QE

p.e.103temp

Dar

k co

unt

Cha

rge

[pC

]

Wavelength [nm]

QE

xCE

25%300Hz

Main board

metal cage Flasher board

Optical gel

HV board

10 inch PMT

DOMPMT

Normal checkNormal check: Linearity of the PMT gain dark noise rate charge resolution2D sensitivity scan

Golden PMTsGolden PMTs:

normal check + Absolute calibrationAbsolute calibration

Hamamatsu Chiba Univ. Wisconsin Univ. Chiba Univ. South Pole

assembles DOMs

check all DOMs (under low temperature)

Linearity of the DOM gain dark noise rate component check cold reboot communication test

Golden DOMsGolden DOMs: 2D sensitivity scan Absolute calibrationAbsolute calibration

Production Procedure

Freezer -32℃

Set up of SPE measurement

Diffuser attached to the UV LED

375nmUV LED

In the Freezer box

2kHz, ~0.01 photo-electron/shot

2( )

The parameterization of SPE CR

The exponential term Comes from an

incomplete multiplication at the first dynode

Fitted the spe charge response

with 1 exponential

+ 1 gaussian terms.

The averaged charge response

Average over 118 PMTs

One measurement

Mean 15% lessMean 15% less

Peak of gaussian Peak of gaussian ~ 1 p.e.~ 1 p.e.

Charge resolution 29%

Absolute calibration of PMT

5x10-11

337nm N2

laser Energy meter

Rayleigh scattering

4x109

Cathode hit photon#

~0.2

QE=Photoelectron#

Energy meter Numerical calculation

Cathode hit photon#

x

Rayleigh scattering cross section is well understood

Using Rayleigh scattering

Results of absolute calibration

Our data havea good correlation with Hamamatsu

QE measured by Hamamatsu(340nm)%

Systematic error

Photoelectron# : 1%Light yield : 4%Initial photon fluctuation : 4 %Pressure : 1%Photon energy probe : 5%Total ~8%

PMT 2D Uniformity ScanAveraged PMT

2D CEMap(~94PMTs)

LED

motor

PMT

The direction of the first dynode

Efficiency depends on the cathode surface.

2D CE combined with QExCE

Absolute efficiency

We can draw Absolute

2D QExCE Map !

2D Collection efficiency

Map

CE Map normalized to QE

Length on cathode [m]

Eff

icie

ncy[

%]

17.8%

18.1% 15.5%

16.0% 18.7%

15.0% 16.7%

17.9%

TA1895 TA2026

TA2086 TA2146 TA2182

TA2259 TA2349

TA2374

Systematic error ～ 8%

20

0-0.15m 0.15m

@337nm

2D QE x CE Map of PMT

Variance of the Collection efficiency0°90°

Variation of the collection efficiency

~ 15%

90° 0°

By. Y.Hasegawa

Length on cathode [cm] Length on cathode [cm]

QE

xCE

[%]

QE

xCE

[%]

Digital Optical Module = DOM

PMT Absolute Calibration

Glass + Gelmeasurement

DOM Absolute Calibration

Reminder …what is a DOM ?

PMT

GelGlass

DOM

Reference PMT Absolutely calibrated

NDfilterLED

Slit 1mm

X-stage

QE×CE Absolute calibration 4πCE scanning

LED

Systematic error ~7% @ room

Calibration of DOM

Reflectivity : 14.5%±0.73Transmission : 50.7%±2.54

By. Y.Hasegawa

15.3%14.0% 15.4% 16.3%

17.5% 16.6% 18.0% 16.0%

TA1895 TA2026TA2259 TA2349

TA2086 TA2146 TA2182 TA2374

Systematic error ～ 7%

18

0-0.3m 0.3m

@365nm

2D QE x CE Map of DOM

Comparison between PMT and DOM

PMT Calibration Transparency of glass/gel

DOM Calibration

Comparison

PMT + Glass/Gel

Wavelength [nm]

Comparison between PMT and DOM

Good agreements over the wavelengths.

337nm8.21%

365nm16.1%

520nm10.7%

572nm4.99%

DOM

NDfilter

LED

Absolute calibration of DOM

PMT + Glass/Gel

470nm17.5%

Detector status

gain

HV

Variation ~2.5%

Mean : 1.0 x 107

Variation ~7%Mean :1285V

Temperature

stri

ng

Shallow ← depth 　→　 deep

rate

IceCube is now working IceCube is now working smoothly!! smoothly!!

UTC Time

4.5Hz

-30℃ -10℃

700Hz

Summary

• General performances of the IceCube PMT were shown.

• Averaged charge response and 2D CE map over 100 PMTs are derived. We have implemented the fundamental characteristics of our detector into the detector simulation.

• We measured absolute efficiency of our PMTs. Our measurement has a good correlation with Hamamatsu.

• We compared between PMT+ Glass/Gel and DOM. It showed good agreement over the wavelength.

• IceCube is now taking data smoothly.

130.04m

Golden DOMAbsolute Calibrated detector

Standard CandleCalibrated N2 laserCone reflected light

Future workAbsolute Calibration in the iceAbsolute Calibration in the ice

Thank you !Thank you !

Backup Slides

Summarized by Y. Hasegawa

Charge resolution(sq0/q0)

Decay time (qtau/q0)

Exponential/SPE(P_ex)

Obtained Parameters

0.51±0.016 0.30±0.01 0.29±0.01

Many PMTs failed to fit at low gain

Total 118PMTs (FY2004~2006)

statistics is enough to picture average behavior !!

19.8%17.6%

17.8%16.7%

12.2%11.3%

5.28%4.29%

Keno_Inuzaka(TA1056) Daikaku_Inumura(TA1176)

18.0%17.0%

16.2%13.5%

11.5%10.5%

5.08%4.65%

17.3%14.4%

14.3%15.4%

9.89%9.66%

4.58%4.05%

Red : measured at 24℃Blue : measured at -32℃

QE measured at -32℃ 　 was 5~10% lowerlower than measured at 24℃

Sosuke_Inukawa(TA1181)

QE measurement at -32℃

After pulses

Original pulse

After pulses

•show around 　 600nsec 2 μsec 8μsec•Peak 13SPE(600nsec)•Rate Hz

ここに測定について載せる予定です

Chiris からの返事待ち

The various peaks are believed to correspond to ions of different mass

@1x107 @5x107

@1x108

Charge Response @different gains

pedestalSPE