Optical Sensor and DAQ in IceCube Albrecht Karle University of Wisconsin-Madison Chiba July, 2003

Outline Events signatures and their requirements on DAQ. The design of the optical sensor for IceCube. A brief construction status.

The IceCube Collaboration Institutions: 11 US, 9 European institutions and 1 Japanese institution; ≈150 people 1.Bartol Research Institute, University of Delaware 2.BUGH Wuppertal, Germany 3.Universite Libre de Bruxelles, Brussels, Belgium 4.CTSPS, Clark-Atlanta University, Atlanta USA 5.DESY-Zeuthen, Zeuthen, Germany 6.Institute for Advanced Study, Princeton, USA 7.Dept. of Technology, Kalmar University, Kalmar, Sweden 8.Lawrence Berkeley National Laboratory, Berkeley, USA 9.Department of Physics, Southern University and A\&M College, Baton Rouge, LA, USA 10.Dept. of Physics, UC Berkeley, USA 11.Institute of Physics, University of Mainz, Mainz, Germany 12.University of Mons-Hainaut, Mons, Belgium 13.Dept. of Physics and Astronomy, University of Pennsylvania, Philadelphia, USA 14.Dept. of Astronomy, Dept. of Physics, SSEC, University of Wisconsin, Madison, USA 15.Physics Department, University of Wisconsin, River Falls, USA 16.Division of High Energy Physics, Uppsala University, Uppsala, Sweden 17.Fysikum, Stockholm University, Stockholm, Sweden 18.University of Alabama 19.Vrije Universiteit Brussel, Brussel, Belgium 20.Dept. of Physics, niversity of Maryland, USA 21.Chiba University, Japan

IceCube 1400 m 2400 m AMANDA South Pole IceTop Skiway 80 Strings 4800 PMT Instrumented volume: 1 km 3 (1 Gt)

Track reconstruction in low noise environment Typical event: PMT fired Track length: km Flight time: ≈4 µsecs Accidental noise pulses: 10 p.e. / 5000 PMT/4µsec Angular resolution: 0.7 degrees Effective muon detector area: 1 km (after background suppression) AMANDA-II 1 km 10 TeV

Point sources: event rates Atmospheric Neutrinos AGN* (E -2 )Sensitivity (E -2 /(cm 2 sec GeV)) All sky/year (after quality cuts) 100,000 - Search bin/year year: Nch > x year: Nch > 43 (7 TeV) x Flux =dN/dE = *E -2 /(cm 2 sec GeV) equal to AMANDAB10 limit

Point source sensitivity IceCube 3 years (1yr) The sensitivity of IceCube to an E^-2 neutrino spectrum is comparable to the sensitivity of GLAST to an E^-2 photon spectrum

Cascade event Energy = 375 TeV e + N --> e- + X The length of the actual cascade, ≈ 10 m, is small compared to the spacing of sensors ==> ≈ roughly spherical density distribution of light 1 PeV ≈ 0.5 km diameter

     Double Bang  + N -->  - + X  + X (82%) E << 1PeV: Single cascade (2 cascades coincide) E ≈ 1PeV: Double bang E >> 1 PeV: partially contained (reconstruct incoming tau track and cascade from decay) Regeneration makes Earth quasi transparent for high energie  ; (Halzen, Salzberg 1998, …) Also enhanced muon flux due to Secondary µ, and µ (Beacom et al.., astro/ph ) Learned, Pakvasa, 1995

Density profile of double bang event -300 m300 m0 m 300 m 0 m Shown is the expected photoelectron signal density of a tau event. The first   interaction is at z=0, the second one at ≈225m. The diagram spans about 400m x 800m. Photoelectrons/PMT

Capture Waveform information Complex waveforms provide additional information E=10 PeV µsec Events / 10 nsec String 1 String 2 String 3 String 4 String 5

Observed waveforms in Ice N2-Laser event generated by in situ laser: Amplitude: ≈ 10^10 photons, Wavelength: ≈ 335 nm Pulse width: ≤ 10 nsec - comparable to ≈300 TeV cascade 2 µsec SimulationData 45 m 115 m 167 m Distance of OM * *HV of this PMT was lowered

E µ =10 TeV ≈ 90 hitsE µ =6 PeV ≈ 1000 hits Energy reconstruction Small detectors: Muon energy is difficult to measure because of fluctuations in dE/dx IceCube: Integration over large sampling+ scattering of light reduces the fluctutions energy loss.

Design goals IceCube was designed to detect to neutrinos over a wider range of energies and all flavors. If one would wish to build a detector to detect primarily PeV or EeV neutrinos, one would obviously end up with a different detector.

E µ =10 TeV ≈ 90 hitsE µ =6 PeV ≈ 1000 hits A remark on the side for EeV fans The typical light cylinder generated by a muon of 1E11 eV is 20 m, 1EeV 400 m, 1E18 eV it is about 600 to 700 m. This scaling gives a hint of how one could design a E>EeV optimized geometry in ice could be. (String spacing ≈ 1 km)

DAQ design: Digital Optical Module - PMT pulses are digitized in the Ice Design parameters: Time resolution:≤ 5 nsec (system level) Dynamic range: 200 photoelectrons/15 nsec (Integrated dynamic range: > 2000 photoelectrons) Digitization depth: 4 µsec. Noise rate in situ: ≤500 Hz 33 cm DOM For more information on the Digital Optical Module: see poster by R. Stokstad et al.

Assembled DOM

Photomultiplier: Hamamatsu R (10”, 10-stage, 1E+08 gain) Selection criteria -40 °C) Noise < 300 Hz (SN, bandwidth) Gain > 5E7 at 2kV (nom. 1E7 + margin) P/V > 2.0 (Charge res.; in- situ gain calibration) Notes: Only Hamamatsu PMT meets excellent low noise rates! Tested three flavors of R7081.

DAQ Network architecture Custom design: 5000 DOMs, 2500 copper pairs, 800 PCI cards (10 racks) Off the shelf IT infrastructure, Computers, switches, disks DAQ Software Datahandling software

Digital Optical Module (DOM) Main Board Test Card

Waveform Capture: Dynamic range /sampling rate (first 400 ns): ~ 14 ~300 MHz  “Analog Transient Waveform Digitizer” Dynamic range/sampling rate (~ 4000 ns): ~ MHz  FADC is appropriate solution PMT noise rate: ~ 500 Hz  Data compression/feature extraction needed

Operational parameters (typical) SPE: 5 mV Electronic noise: <0.2 (0.1) V Dynamic range: 200 PE/15 nsec 1000 PE/4 µsec Overall noise rate of DOM: Hz Design goals

IceCube String 1400 m 2400 m OM Spacing: 17 m

The DOM communicates via ≈3km copper wires to the central DAQ 2 DOMs on one twisted pair Bandwidth goal: 1 Mbit/sec

The DOM Receiver (DOR): a PCI Card

Data transmission New test cable from Ericsson tested successfully at 1 Mbit/sec. Recent from K.-H. Sulanke (DESY/LBNL) with attached file labeled: “TX0_RX1_no_problem. PDF” Figure shows bit sequence before and after transmission over 3.5 km twisted pair.

The DOM Hub (prototype)

Counting room Preliminary, (30%) 52’ x 28’

Counting House will be very similar to other buildings at the South Pole. ARO building, South Pole

Low temperature Laboratories and Test facilities The Collaboration is building production and test facilities in Europe, US and in Japan. Sensors to be tested in large dark freezers. Production, Verification and initial calibration of each DOM during extended test periods (months) prior to deployment.

Example of a dark freezer laboratory. up to °C

Production of drill components

The big reel for the hotwater drill

Hotwater Drilling New drill: Faster and more reliable. Drilling time to 2000 m depth: 35 h (AMANDA: 80h) Diameter: 50 cm Picture: AMANDA drill

South Pole Dark sector AMANDA IceCube Dome Skiway

First Deployment planned in 04/05 season. No more freezing: Deployment will be in heated environment.

Construction: 11/ /2009 AMANDA SPASE-2 South Pole Dome Skiway 100 m Grid North IceCube Next season: Buildup of the Drill and IceTop prototypes

South Pole /end Dark sector AMANDA IceCube Dome Skiway

“Size” of cascades in ice Calorimetry: Number of photons scales linearly with deposited energy. Volume illuminated by ≥ 1 p.e.is well correlated with primary energy. Photoelectrons / OM / PeV

Waveform Capture: Analog Transient Waveform Digitizer: –Four-channel MHz – MHz  422 ns –10-bit digitization in 12.8  40 MHz –Low power consumption: < 100 mW –No high-speed clocks needed (active delay line) –100 ATWDs used in AMANDA String 18 –5000 ATWDs used in KamLAND

DOM Main Board Test Card - June 2003

Schematic of IceTop detector Two Ice Cherenkov tanks at top of each IceCube hole –Each 3.6 m 2 ; local coincidence for muon vs. shower discrimination –Calibration with single ~1KHz per tank Integrated into IceCube –construction –trigger –data acquisition Heritage: –Haverah Park –Auger Single 

Coincident events Two functions –veto and calibration –cosmic-ray physics Energy range: –~3 x eV –few to thousands of muons per event IceTop

 at E>PeV: Partially contained The incoming tau radiates little light. The energy of the second cascade can be measured with high precision. Signature: Relatively low energy loss incoming track: would be much brighter than the tau (compare to the PeV muon event shown before) Photoelectron density Timing, realistic spacing Result: high eff. Volume; Only second bang needs to be seen in Ice OM early hits measuring the incoming  -track