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DOM and String Performance

DOM and String Performance. Kael Hanson IceCube – In-Ice Devices Berkeley Collaboration Meeting March 21, 2005 Berkeley, CA. The DOM. Highlights of DOM Capabilities. Incredible dynamic range: 1 pe to 25000 pe Low photon counting background: in-ice rates of order 700 Hz

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DOM and String Performance

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  1. DOM and String Performance Kael Hanson IceCube – In-Ice Devices Berkeley Collaboration Meeting March 21, 2005 Berkeley, CA

  2. The DOM Highlights of DOM Capabilities • Incredible dynamic range: 1 pe to 25000 pe • Low photon counting background: in-ice rates of order 700 Hz • Complete self-contained digital data acquisition system that is field reconfigurable • High-precision timing over vast network of 1000’s of sensors to nanosecond scale. Risks / Concerns PY03 Accomplishments • Complex system • Steep learning curve: propagation of knowledge is slow process. • Difficult to debug - encountering this /w/ Q2 and elsewhere. • We should resist the tendency to make changes especially because of this complexity. • We have never operated a DOM in its real mode. Surprises await? • Prototyped, built, and tested 400 DOMs • Shipped 280 to Pole • Deployed 76: 16 IceTop + 60 In-Ice PY04 Goals • Understand DOM performance at Pole • Complete design verification in NH • Build 930 DOMs – 800 to Pole.

  3. PY04 Production

  4. DOM Testing • PY04 testing will begin 4/16 at PSL – mid-May for DESY and Uppsala • Follows same basic plan from last year with some additional analyses that were previously skipped. • All failures from all sites being tracked with formalized system of Non-Conforming Materials which includes a failure review with recommended corrective actions. • Need to increase 1st pass yield – not even PSL site can handle large number of DOMs in failure review. • We took measures to reduce or eliminate major contributors to last year’s failures: • Flasherboard • Reboot problems • PMT Gain • Gel • Optical diffusing system improved for this year’s run to reduce fiber temperature variations.

  5. PY03 DOM Testing

  6. PY04 Pole Testing

  7. String Operations - Planning • Want to establish baseline for taking data that is all-around OK. • From this default point, can schedule special runs or other activities as needed: • Flasher runs for calibration, timing verification • Low-level communication testing • Whatever else • Runs coordinated from central point to avoid resource contention, provide control gate. • Note this enforces but does not define rules for deploying and maintaining DAQ software. • Original planning phone call, prototype plan documented athttp://icecube.wisc.edu/mailing-list-archives/ice3in_ice_archive/pdf00015.pdf • ICCOC accepts input from collaboration, submits plans weekly to IceCube winterovers.

  8. DAQ Configuration + Status @ Pole • TestDAQ – the DAQ used in the FAT • Monolith – an offline string processor, trigger framework, and event builder to trigger, build, and write out events in the real DAQ format. • Handoff to online filtering through DAQ-dispatch not implemented but working on getting the machinery in place to exercise that system this year before DAQ comes online. • 4 DOMs on Q2 – quad at top of string – has communication problems when in bootloader state. Communication at acceptable rate (few retries, but detectable) when in normal data-taking mode. Root cause still unknown – under investigation.

  9. Data Taking Summary for String 21 Initial Phase (Runs < 650) Runs 650 - 828 • Readout format not optimized • Many missing DOMs (bad configuration – also not all quads powered because of connector leakage) • TestDAQ run configuration file • Readout format optimized • 15 min nohits • 200 sec hit • DOMHub configuration file error causes 21-15 to 21-18 to be excluded from run. Runs 828 - 1200 Special Runs 1270 + 1271 • DOMHub configuration fixed – ALL DOMs reading out on string / surface tanks. • Special flasherboard runs. Uncontrolled DOM MB version – hacked to provide flasherboard support  Runs 1420+ Projected for near future • Same as config #2 • Adding regular DarkNoise runs (1:50 ratio). • More flasherboard runs from entire string. “Official” DOM MB release 314 /w/ flasherboard support installed on all DOMs 

  10. Local Coincidence • Baseline of majority of data running this year is likely to utilize local coincidence (LC). We have prototype feature extraction running in TestDAQ domapp code but it is not the ultimate solution and current software does not fully support it. • LC operation works for all deployed modules – reduces the data rate from 700 Hz singles’ hit rate to 10 Hz (see next slide). My prediction is that we become quickly habituated to hard LC and adopt that as future year baseline – it has dramatic impact on requirements of the surface DAQ. • Emphasis on simple NN LC this year – we still have not implemented (or fully designed) scheme for non-NN LC.

  11. Local Coincidence II

  12. In-Ice Noise Rates • Turned out better than expectation of 850 Hz average noise rate. • Next slide shows DOM noise rates taken from monitoring scalers from two different runs about 1 week apart: apparent that top of string has settled down to final level. DOMs at bottom still quieting down. • All DOMs show same noise characteristics, irrespective of manufacturing site, with overall average of 750 Hz, including elevated noise DOMs at string bottom. • Rate is strongly correlated to (much higher) rate measured in FAT with multiplicative factor of approximately 3. We can explain easily a factor of two – however the extra 50% is unresolved – likely radioactive background very hard to eliminate without great effort. • Monitoring (Ignacio) turned up 21-30: DOM which has unstable noise rate – root cause under investigation.

  13. Rates in Deployed DOMs

  14. FAT Rate vs. In-Ice Rate

  15. DOM Waveforms • Slide 14: IceTop high gain DOM (5.0E+06). Typical muon waveform • Slide 15: IceTop low gain DOM (5.0E+05). Typical muon waveform. Gain needs a little adjusting, probably, to hit target. • Slide 16: In-Ice DOM (1.0E+07). Single pe waveforms – multiple pulses separated by 100’s of ns due to scattering in ice. Top plot shows high-resolution ATWD where pulses clearly resolve. Lower plot shows FADC capture – 1.4 us long but only sampling at 40 MHz so pulse shaper smears first 3 pe together.

  16. IceTop High Gain

  17. IceTop Low Gain

  18. In-Ice

  19. Extra Slides Supplementary Material

  20. Gel Clouding • Some indications that gel becomes cloudy at low temperature. • Top picture taken in chest freezer at -49 °C – bottom picture is room temperature DOM. • Visible clouding, but … • Noise rates observed in DFL and along string are what is expected over temperature range. • Full UV-VIS spectrophotometer scan of gels at low temperature planned (D. Lee) • PY04 DFL testing with more well understood fibers will be able to resolve this on DOM-by-DOM basis.

  21. PMT Afterpulsing Multi-pe pulses Single-pe pulses Afterpulse data from FAT4

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