April 4, 2007 Rolf Nahnhauer1 DESY-PROJECT IceCube Digital Optical Module Production

April 4, 2007 Rolf Nahnhauer2

April 4, 2007 Rolf Nahnhauer3 IceCube Status April 2007

April 4, 2007 Rolf Nahnhauer4 THE ICECUBE OBSERVATORY IceTop air shower array 80 pairs of ice Cherenkov tanks IceCube deep ice array 4800 optical modules on 80 strings instrumented volume : 1 km3 first string deployed : January 2005 ~ atm. per year

April 4, 2007 Rolf Nahnhauer5 2005, 2006, 2007 Deployments AMANDA IceCube string deployed 12/05 – 01/ DOMs deployed to date Next year looking for 14 to 18 strings. Want to achieve steady state of >= 14 strings / season IceCube string deployed 01/05 IceCube string and IceTop station deployed 12/06 – 01/07 IceCube Lab commissioned = 22 strings to date

April 4, 2007 Rolf Nahnhauer6 Hotwater drilling: Trend towards increasingly stable operation continued. Experienced crew IceCube Pole Season 2006/2007

April 4, 2007 Rolf Nahnhauer7 IceCube lab commissioned, South Pole computing system (SPS), all racks and infrastructure installed, 64 bit implemented on SPS and SPTS, About 10 racks of computers and hubs. Working simulation, exp control, PnF IceCube Pole Season 2006/2007

April 4, 2007 Rolf Nahnhauer8 IceCube Events Neutrino in IC 9Flasher Pulse in IC 22

April 4, 2007 Rolf Nahnhauer9 IceTop: cosmic-ray physics IceCube: calibration, background tagging IceTop/In-ice coincident events

April 4, 2007 Rolf Nahnhauer10 Atmospheric neutrinos in IC 9, 2006 John Pretz, Ph.D. thesis Ratio of data to simulation: R= (syst) (stat) given at cut strength upgoing muon events purity of neutrino sample > 95% First IceCube Results

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April 4, 2007 Rolf Nahnhauer12 PRODUCTION SCHEDULE Numbers from February 2004 slightly changing with time Baseline change: 80 strings  70 strings + 10 strings from contingency xxx

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April 4, 2007 Rolf Nahnhauer15 DOM Production DESY IntegrationStatus - PY 07 ( April 2008-March 2009) PYYear# DOMs ready 034/04-3/ /05-3/ /06-3/ /07-3/ /08-3/ ? DOM integration at DESY will finish 7/08 to 11/08 decision how many DOMs for how many strings have to be produced, will come in summer 2007

April 4, 2007 Rolf Nahnhauer16 FUTURE PRODUCTION and TESTING

April 4, 2007 Rolf Nahnhauer17 DOM Production and Testing at DESY

April 4, 2007 Rolf Nahnhauer18 DOM PRODUCTION at DESY Production of up to 1300 Optical Modules until mid 2008 Production comprises: Gel mixing, filling and potting PMTs Collar mounting and assembly of electronics Sealing of DOMs at low pressure Harness DOM with suspension Finally pack DOMs and ship them to the pole

April 4, 2007 Rolf Nahnhauer19 PROJEKT-ABLAUF

April 4, 2007 Rolf Nahnhauer20 Dr. H. Waldmann 100% Dr. J. Bolmont ( postdoc) 65% xx S. Henze xxx J. Pieper S. Ladegast

April 4, 2007 Rolf Nahnhauer21 OMP-Projekt Investitionen #OM

April 4, 2007 Rolf Nahnhauer22 OMP-Projekt Personalbedarf Weeks kEuro Produktion Physiker Postdoc Ingenieure Techniker/Werkstaetten Produktion Physiker Postdoc Ingenieure Techniker/Werkstaetten

April 4, 2007 Rolf Nahnhauer23 DOM TESTING Electronic and optical requirements Reboot- and communication over a wide temperature range from +20°C to -45°C Single photo electron detection Wide dynamic signal range – capable to handle large light pulses with up to several 1000 photo electrons per microsecond Time resolution better than 5ns for single photo electron pulses High voltage calibration of the PMT better than 5% Optical sensitivity within low variations for different DOMs Dark noise rates less than 1kHz in ice Mechanical requirements Vibration and pressure fluctuation during transport Rapid temperature variations from +20°C to -45°C Very high environment pressure up to 650 bar

April 4, 2007 Rolf Nahnhauer24 DOM FINAL ACCEPTANCE TEST XY X + Y > 180 h A full set of different tests is performed for defined temperatures Test of the electronics (mainly running diagnostic programs, checking the hardware components) PMT high voltage calibration Rate monitoring while DOMs are illuminated with light of different wavelength Dark rate monitoring Data taking with a DAQ system similar to the final low level south pole DAQ (Linearity and time resolution tests) Timing scenario:

April 4, 2007 Rolf Nahnhauer25 DARK FREEZER LAB Large cooling chamber (4 x 6 x 2 m) Temperature control with cooling aggregate and heaters Minimal temperature for test cycle is -45°C (in the US -55°C for IceTop DOMs) Optical fibers and mirror system installed on each test station DOMs sit on top of cylindric cans Cans are taped with aluminum foil to distribute the light DOMs are covered with black plastic bags to keep them as dark as possible for the measurements

April 4, 2007 Rolf Nahnhauer26 TEST ENVIRONMENT SETUP Dark Freezer Lab (DFL) with 64 test stations Same DAQ and wiring as for the South Pole system Simulated cable length up to 3km Light is distributed equally to the DOM stations via optical fibers Time synchronization of multiple domhubs with a global GPS clock Light system allows event simulation Different light sources: Laser for time calibration, pulsed LED for linearity test, DC lamp with monochromator for optical sensitivity test

April 4, 2007 Rolf Nahnhauer27 DFL STATION CALIBRATION Light yield differs for all stations There is a wavelength dependence of the optical system For studies of the optical sensitivity the stations have to be calibrated During test runs a well characterized monitor PMT takes direct signals from the light sources Together with the calibration information the relative optical sensitivity of the DOMs can be evaluated

April 4, 2007 Rolf Nahnhauer28 ELECTRONIC TESTS A self test of the electronic components runs on the DOM  performed on bare mainboards before delivering  performed on integrated DOMs as functional test Reboot tests are performed during the complete test cycle DOMs are turned on and off more than 100 times over a test run in addition tests of software uploads are performed For the tests of the local coincidence chain the DOMs in the DFL are connected pairwise like on a real string

April 4, 2007 Rolf Nahnhauer29 DOM CALIBRATION I ATWD Calibration : Reconstruction of PMT voltage waveform from ATWD data requires: Voltage calibration of ATWD Measurement of amplifier gain for ch0, ch1, and ch2 Frequency calibration of ATWD Baseline measurement Performed using the internal pulser and oscillator

April 4, 2007 Rolf Nahnhauer30 DOM CALIBRATION II Dark noise events are used to record the charge spectrum of single photo electron events Calculation of the mean charge for different PMT high voltage settings reveals the gain Finally this results in a linear fit of the gain versus high voltage relation Working voltage yields gain = 10 7 Requirements: Peak to valley ratio > 2.5 Gain > 5  10 7 at 2000 V overall relative error < 5% Charge Spectrum of single photo electron events at 1400 V Gain versus voltage[V]

April 4, 2007 Rolf Nahnhauer31 TIME SYNCHRONIZATION Each DOM runs with an individual clock A global time synchronization has to be performed regularly to match the DOM-time to a global time including signal run-time The RapCal method : Time stamped bipolar pulses are sent from the DOR card to the DOM and vice versa This gives a coarse time synchronization of the order of 50ns (local clock speed) In order to improve the time synchronization accuracy the bipolar pulses are fitted at arrival, giving an exact time e.g. for zero crossing of the waveform With that information the round trip time can be calculated and the accuracy of the time calibration is improved to better than 5ns

April 4, 2007 Rolf Nahnhauer32 TIME RESOLUTION Pulse laser sends accurate signals (~75ps wide) to the DOMs A bare mainboard records the absolute pulse time (sync pulse) Analyze the distribution of time differences of DOM’s and sync pulse The width of the distribution gives an upper limit for the DOM time resolution Fraction of late pulses identify noise and time calibration problems An overall comparison of the signal time offsets of all DOMs give information about the time resolution stability Light and signal travel time

April 4, 2007 Rolf Nahnhauer33 LINEARITY DOMs are illuminated with different light intensities using a pulsed LED with different power settings Different filters are brought into the light path to attenuate the amount of light Plots show the charge distribution for different filter settings (low to high attenuation) Plotting the mean charge versus light intensity gives the linearity characteristic for a DOM

April 4, 2007 Rolf Nahnhauer34 OPTICAL SENSITIVITY Sensitivity of integrated DOMs differs due to transmission characteristic of glass (sphere,PMT), gel and the PMT quantum and collection efficiency Do rate measurements while the DOM is illuminated with light of varying wavelength Data has been already recorded, analysis is in preparation Measure behaviour of subsystems: e.g. transmission of gel samples with respect to air Allows relative comparison of different production batches

April 4, 2007 Rolf Nahnhauer35 DARK NOISE Readout on board scaler – discriminator crossings of PMT signal Requirements: Mean noise rate < 3kHz No outliers within 5σ (Noise rate in ice is much lower (~700Hz)) Search for spikes in noise rate background – maybe an indication for problematic PMTs or HV generators Coincidence spikes are likely caused by some outside influences [Hz] Histogram of the dark noise rates for a single DOM

April 4, 2007 Rolf Nahnhauer36 DOM - Passport Decision June 2005: use formalized DOM-passport for characterization and qualification of DOM’s (ready early 2006)

April 4, 2007 Rolf Nahnhauer37 DOM-Production Year DOMs produced DOMs OK  final DOMs shipped only ~1% of DOMs are cannibalized – goal was 5% or better good components are used in next years production

April 4, 2007 Rolf Nahnhauer DOM TESTING + USAGE timeloadgoodbadcomment FAT gel, 1 MB, 1 HV FAT gel, 1 MB FAT MB,3 FB,1 HV FAT use 5 CAEN HV locationnumberqualitypurpose Pole42gooddeploy DFL3goodstandard Madison8badCheck Dortmund1badHV-tests -6badcannibalize Production efficiency:  P 2004 = 75 % Wanted:  P = 95 %

April 4, 2007 Rolf Nahnhauer DOM TESTING Timeloadgoodbad  FAT FAT FAT FAT FAT FAT *) in all cases +3 permanent DOM’s from FAT3 for comparison FAT5 FAT6 FAT7 FAT8 FAT9

April 4, 2007 Rolf Nahnhauer DOM TESTING timeloadgoodbad  FAT FAT FAT FAT FAT FAT FAT FAT10 FAT11 FAT12 FAT13 FAT14 FAT15

April 4, 2007 Rolf Nahnhauer DOM TESTING timeloadgoodbad  FAT FAT FAT FAT xx.yy34 FAT16FAT17 No dominant error source could be identified in FATs Different small problems appeared for all FATs

April 4, 2007 Rolf Nahnhauer42 Summary DOM first year mass production is running without problems Production team well trained Delivery of components mostly smooth Storage space sufficient but at the limit, many transports between Zeuthen and Wildau necessary Many small problems contribute to test failure rate Total failure rate after rework sufficiently small (better than expected) DESY well prepared for continuous mass production until autumn 2008