# Presentation: 431275

## Slide 1

## Overview

- Design Requirements
- IceCube DAQ
- Reliability, QA
- Lessons Learned
- Performance

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## Design Requirements

- Reliability / Robust Design
- Remotely controllable
- Failure must not propagate
- Resistant to Radio Frequency Interference
- Hit rate is ~1kHz
- Low power consumption < 5W/DOM
- Surface temperatures     -20°C - -70°C
- At-depth temperatures    -10°C - -35°C

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**Notes:**
Low Power: Fuel flown in
Copper cable: Reliability of optical connectors
1TP : No Main Cable connection in ice; Wire pair diameter vs. loss; Cargo bay LC130
+-48V : personnel safety

## Physics Requirements

- Timing, 7ns RMS		3ns RMS
- Waveform capture
- 300MS/s for 400ns, 40MS/s for 6.4μs
- Charge Dynamic Range
- >200PE/15ns		~500PE/15ns
- Insitu Calibration (internal and external)
- Hardware Local Coincidence

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**Notes:**
Timing refers to Photon arrival time resolution

## IceCube

- 70-80 Strings
- 60 DOMs per String
- IceTop Air Shower Array on top of String

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**Notes:**
70-80 Strings 
-> 60 Optical modules per string (DOM)
-> all strings end in the counting house

## DAQ System Overview

- Ethernet

- DAQ
- E
- l
- e
- c
- t
- r
- o
- n
- i
- c
- s

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**Notes:**
Strings with DOMs connected
Strings end in DOMHub (1 DOMHub per String)
Custom Hardware: - DOM
			- DOR Cards at the surface end of Cable
- After the DOMHub standard computer HW and Ethernet is used

## Timedomains

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**Notes:**
We don’t send a Clock Signal to the DOMs over the wire-pair
 -> Each DOMs uses its own Clock(Time) source
 -> The Surface HW (DOR) uses GPS “master time units”
 -> We do time calibration (Tcal) between the DORs and DOMs
   -> Stringprocessor converts the local DOM time to the GPS master time. 

## DOMHub

- 8 DOR Cards

- GPS
- distr.

- Chassis Fans

- Power Distr. Card

- DOM Power Supplies

- CPU

- Hard Drive

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**Notes:**
A DOMHub is a rack-mountable PC with an PCI backplane.
DOR Cards plugged in to the DOMHub make the Interface to the DOMs.
DOMHubs are self contained (Own DOM power supply and has alternative clock source if GPS is not present)

## DOM Readout Card

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**Notes:**
Left Side: 2 Connector servicing 2 twisted quads (8 DOMs)
Right Side: 96V and GPS input
Two FPGA: one for PCI and one for communications

## Main Cable

- 0.9mm Twisted Quad Copper Cable
- 2.5km long (continuous in ice) + Surface Cable
- 2 DOMs per wire pair
- Power, Timing and Communications over the same wire pair
- > 50dB suppression near end cross talk
- > 30 db suppression far end cross talk

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**Notes:**
Just for quick reference:
We use Twisted Quads because the use less space than Twisted pairs
Each DOM has its own connector for easy deployment

## Digital Optical Module

- Passive Base
- HV Supply
- Flasher Board
- Main Board
- Delay Board

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**Notes:**
Benthos Sphere
10’’ PMT
Mu metal shield
Flasher board used to calibrate neighbor DOMs
Flasher Board and MainBoard are attached to the PMT neck
Cathode is on “Ground” level to avoid an electric field in the Gel
 -> PMT signal is on High Voltage -> Transformer coupled (Better performance, than capacitors, for long pulses)

## DOM Main Board

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**Notes:**
Point out:
Analog section
ATWD (custom SCR based ADCs)
FPGA/CPU/memory/CPLD
X-Tal
Communications / Local Coincidence
Power Supply
 -> Also note the 2 big white capacitors. Foil and NOT Electrolytic 

## DOM Main Board

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## DOM Main Board

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## Altera Excalibur

- FPGA 400,000 Gates
- ARM9 CPU
- Bus bridges between CPU and FPGA
- Dual Ported Memory between CPU and FPGA
- Power consumption 0.5 – 0.7W

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**Notes:**
Bridges between FPGA and CPU (Dual Ported Memory, Bus from CPU to FPGA and FPGA to CPU)

CPU: High level control
FPGA: Used for fast, timecritical deterministic tasks

e.g.
Communications: Low level is in FPGA. High level in CPU (retransmit, ..). DPM serves as data buffer
DAQ: FPGA collects data, subtracts pedestal, compresses data, DMA transfer to CPU memory through bus bridge.

## DOM Main Board

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## ATWDAnalog Transient Waveform Digitizer

- ASIC
- Switched Capacitor Array
- 4 Channels x 128 Samples Deep
- Sampling on Launch
- Sample Speed 250 - 800MSamples/s
- Digitization, ~30μs/waveform
- Power consumption 125mW

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**Notes:**
ATWD is an ASIC developed at LBNL
Used before in Nestor and KamLAND
Starts sampling on launch -> delay for signal required

## DOM Main Board

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## Oscillator

- Reference “time” of DOM
- Short term stability
- Screened for short term stability

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**Notes:**
Reminder: Local clock
Stability for less frequent time calibrations

Critical Part:
Used for clocking
Local DOM “time” based on it -> good short term stability

## DOM Main Board

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## Local Coincidence

- Reduce Data Rate
- Rate without LC ~1KHz
- Rate with LC <10Hz
- Dedicated Full Duplex LC connection
- Transmit and Receive go through FPGA
- LC functionality can get reprogrammed

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**Notes:**
Main Noise source is radioactive decay in Benthos Sphere

## Reliability, QA Overview

- DOMs are not accessible after deployment
- By Design
- Production
- Testing

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**Notes:**
Because of the volume of Items I split it up into 3 Groups. Some points could fit into more than one group.

## Design

- Qualified Manufacturer List
- GIDEP (Government-Industry Data Exchange Program)
- No Electrolytic Capacitors
- Derate Parts
- HALT (Highly Accelerated Lifetime Testing) Input
- Serial number; electronic, barcode and human readable
- Robust Bootstrap boot mode
- Little Redundancy in the DOM (Deployed Spares)
- No MTBF calculations (Temperature range)

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**Notes:**
HALT testing: -80C to +80C and 30G rms vibration

Designing was an iterative process. 

## Production

- IPC610 class 3 for Board production and loading
- No Microwelds in PCB
- Use of Industrial Temperature Parts
- Tin-Lead Parts wherever possible (NO pure tin parts)
- Close work with Board manufacturer and loading house for fast feedback
- Several Optical inspection Steps
- Digital picture of Boards after loading
- ESD Precautions

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**Notes:**
IPC610 class 3: sets tolerances for PCB production and Board loading
e.g. wetting of pins, alignment of Parts, trace width and spacing

Microwelds:
Standard practice
Allowed in class 3
- Repairing discontinuities by welding copper tape to the trace

No Military parts used. They are too expensive. Lifetime buy for critical parts

## Testing

- Initial room temperature Test
- HASS (Highly Accelerated Stress Screening)
- 48 hour Main Board burnin hot and cold
- Interface test
- Integrated DOM burnin 21 days at various Temp.
- Test before Deployment at ~-25°C
- In Summary; Testing, more Testing and even more ...
- All Test results are stored in Database
- ESD Precautions

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**Notes:**
HASS testing: -50C to +65C and 7G rms vibration
Integrated Burnin: 14 days at –55C

## Lessons Learned

- Test Framework (bench, integration, before deployment and after deployment)
- DOMHub can run standalone
- Terminal Connection to DOM
- Script Language/Interpreter on DOM

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## Performance

- One String and 4 IceTop Stations are deployed
- Time Calibration
- Noise/Discriminator Threshold
- Muon Reconstruction

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**Notes:**
One String is in the Ice. Don’t expect a lot of physics.

## Time CalibrationReciprocal Active Pulsing 

- Verified using:
- Flasher Boards
- IceTop –IceCube coincidences
- AMANDA – IceCube coincidences

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**Notes:**
As mentioned earlier, each DOM has its own “time”.
Important to verify we can synchronized the clocks.

Standard synchronization is RAP Cal. It is working.
RAP Cal was verified using:
- Flasher boards (establishing time between DOMs)

## Clock Stability

- Time Calibration every 3.5s

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**Notes:**
1st: Short term stability. Each Sample is referenced to the previous sample
2nd: Long term stability. Each data point is reference to the first data point.

## Noise/Discriminator Threshold

- PMT Gain 107
- Noise in the Ice is ~800Hz
- Threshold as low as ~1/8SPE

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**Notes:**
Important for the physics is the noise and from there the discriminator threshold.
For the plots
Using Local Coincidence, the Rate drops to <10Hz

## Muon Reconstruction

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## Summary

- DAQ Design
- Reliability
- One IceCube string deployed
- Four IceTop Stations deployed
- String is working very well
- All 76 DOMs function well
- In Jan, Feb up to 10 more Stings deployed
- Full Array deployed by 2009-10

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## Thank You

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