DOM and String Performance

Kael HansonIceCube – In-Ice Devices

Berkeley Collaboration MeetingMarch 21, 2005

Berkeley, CA

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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.

PY03 Accomplishments• 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.

Risks / Concerns• 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?

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PY04 Production

IceCube DOM Production PY4 - Summary

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DOMs ready for DFL @ PSL -cumulative planDOMs ready for DFL @ DESY -cumulative planDOMs ready for DFL @ Swed -cumulative planDOMs ready for DFL - cumulative planall sites

Ship 248 on 7/16

Ship 208 on 9/10

Ship 80 on 10/8

Ship 88 on 7/30Ship 56 on 10/1

Ship 72 on 7/23Ship 72 on 10/8

Summary:1. PSL integrates 610 DOMs from 4/2 to 9/3, ships 536 of 549 after 90% assumed FAT yield in 6 FAT cycles.2. DESY integrates 160 DOMs from 4/23 to 8/6, ships 144 of 144 after 3 FAT cycles. 3. Sweden integrates 160 DOMs from 4/30 to 8/27, ships 144 of 144 after 4 FAT cycles.

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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.

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PY03 DOM Testing

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PY04 Pole Testing

PY04 South Pole DOM Test Plan

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11/13 11/27 12/11 12/25 1/8 1/22

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Incoming

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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.

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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.

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Data Taking Summary for String 21

Initial Phase (Runs < 650)• Readout format not optimized• Many missing DOMs (bad

configuration – also not all quads powered because of connector leakage)

Runs 650 - 828• 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• DOMHub configuration fixed –

ALL DOMs reading out on string / surface tanks.

Special Runs 1270 + 1271• Special flasherboard runs.

Uncontrolled DOM MB version – hacked to provide flasherboard support

Runs 1420+• Same as config #2

Projected for near future• 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

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Local Coincidence

B

A

C

For this DOM to readout a hit:must be a hit in either A or C

• 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.

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Local Coincidence II

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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.

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Rates in Deployed DOMs

Deployed DOM Rates

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21-01 21-06 21-11 21-16 21-21 21-26 21-31 21-36 21-41 21-46 21-51 21-56

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Run 804

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FAT Rate vs. In-Ice Rate

In-Ice vs. FAT Rate

y = 3.29x

R2 = 0.5875

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In-Ice Rate [Hz]

FAT R

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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.

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IceTop High Gain

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IceTop Low Gain

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In-Ice

Extra Slides

Supplementary Material

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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.

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PMT Afterpulsing

MBID Events AP Ratio

5b1167dc9fa2 2856 66 0.023

58d02ed78f37 5258 133 0.025

227a98ab9a22 3880 84 0.022

1aa46e241d8b 2601 54 0.021

789b9a06d28e 4390 78 0.018

66d6302e86d7 7142 104 0.015

6f5f9b170405 7645 132 0.017

06f03e3b1175 7753 200 0.026

78d52c98293c 1074 25 0.023

28bded357ae0 259 9 0.035

4fb2e7dcd3cf 7142 167 0.023

Multi-pe pulses

Single-pe pulses

Afterpulse data from FAT4