1 / 26

IceCube Calibration Overview

IceCube Calibration Overview. Kurt Woschnagg University of California, Berkeley MANTS 2009 Berlin, 25 September 2009. 4800 identical sensors in ultraclean, stable ice. Database. timing. charge. High level. Low level. ice properties: scattering, absorption, hole ice.

lynna
Download Presentation

IceCube Calibration Overview

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. IceCube CalibrationOverview Kurt Woschnagg University of California, Berkeley MANTS 2009 Berlin, 25 September 2009 4800 identical sensors in ultraclean, stable ice

  2. Database timing charge High level Low level ice properties: scattering, absorption, hole ice event energy track pointing g geometry m efficiency n

  3. Geometry calibration Stage 1 Requirement: position of every DOM known to 1 m Absolute surface coordinates

  4. Geometry calibration Stage 1 tower base plate How deep? How straight? well depth water surface pressure sensors string depth in water bottom DOM (defines string depth)

  5. Geometry calibration Stage 2 Relative depth adjustments Gaussian fit t0 = a - b·d t (ns) dD L z=0 Hyperbola fit Distance between DOMs [m] Flash all horizontal LEDs and look at photon arrival times at receiving DOMs z [m]

  6. Geometry calibration Stage 2

  7. Timing calibration Requirement: single-photon timing resolution < 5 ns RAPcal – run by DAQ every few seconds – synchronizes local clocks with master clock for 76 OMs monitored for every run: In-ice DOMs IceTop

  8. Timing calibration: verification with flashers

  9. Timing calibration: verification with muons Reconstruct muon tracks without DOM i. Look at time residuals for DOM i for nearby (<10 m) tracks:

  10. Charge calibration Translate digitized waveform signal (V) to number of photo-electrons (pe) DOMcal • DOM-resident calibration software • runs regularly (~every few weeks) • PMT gain as function of HV • Analog frontend gains and offsets • Discriminator thresholds • Digitizer sampling speed • PMT transit time

  11. Charge calibration: PMT linearity & saturation Pre-deployment lab measurements (at low gain) Saturation curves measured in-situ with flasher data Need DOM-specific saturation curves

  12. PMT and DOM efficiency Lab measurements & Golden DOMs

  13. Understanding the ice “Three feet of ice does not result from one day of cold weather” Chinese proverb The deepest IceCube ice is 100,000 years old

  14. Understanding the ice What is the scattering/absorption length?

  15. Understanding the ice What is the scattering/absorption length? “Answer the question, jerk!” John McEnroe

  16. Understanding the ice What is the scattering/absorption length? “Answer the question, jerk!” John McEnroe

  17. Understanding the ice What is the scattering/absorption length? “Answer the question, jerk!” John McEnroe “You can not be serious!” John McEnroe

  18. Ice properties ↔ dust concentration ↔ climate South Pole (US) Dome Fuji (Japan) Vostok (Russia)

  19. Understanding the ice The dust layers are not completely horizontal

  20. Understanding the ice There may be shear in the deep ice • Geometry changes over time The “hole ice” is different from the “bulk ice” • Air bubbles make acceptance more isotropic “hole ice” (trapped bubbles)

  21. Calibration instrumentation • LED flasher boards • “Standard Candle” lasers • Dust loggers • Bubble cameras • Transmissometers • Pressure sensors • Thermistors • Golden DOMs 65cm

  22. Energy calibration

  23. Energy calibration: Standard Candles • Nitrogen laser • Calibrated output • Cherenkov cone

  24. overlapping energy region useful for cross-calibration depends on brightness setting, # of LEDs, pulse width flashers SC I SC II Energy calibration cascade energy* GeV TeV PeV EeV *applying rule-of-thumb: 105 photons/GeV

  25. Pointing accuracy “calibration” 1. IceTop coincidences Mismatch angle between IceTop and in-ice reconstructed track 2. Moon shadow

  26. IceCube calibration summary Low-level calibrations • Geometry, timing • mature, understood (lots of experience from AMANDA) • Waveforms/charge • basics (SPE) understood • more work needed as complex NPE waveforms included • Ice • description more detailed than simulation can handle High-level calibrations • Energy calibration • have special devices, depends on low-level calibration

More Related