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XFEL-PIXEL Readout and control. Detector requirements/proposal Basic concepts for experiments Control electronics Selecting/rejecting bunches Backend-systems Time schedule Conclusion. Detector requirements. Call for experiments: large pixel detectors: > 1Mega-Pixel

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Xfel pixel readout and control
XFEL-PIXELReadout and control

Detector requirements/proposal

Basic concepts for experiments

Control electronics

Selecting/rejecting bunches


Time schedule


Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05

Detector requirements
Detector requirements

Call for experiments:

large pixel detectors: > 1Mega-Pixel

large number of frames: XFEL: 30000 bunches/sec

large dynamic range 104-106 Photons/pixel/frame

distinguish 0 and 1 Photon, rest Poisson-limit

With 2Bytes/pixel and 1MPixel 60GByte/sec

- but experiments will not handle frame rate

- Data reduction of "compression" is not effective:

Statements of nearly nothing to factor 2-4.

Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05

Three proposals
Three Proposals

AP-HPAD: analogue pipe-line Hybrid Array Pixel Detector

Si-pixel: ASIC stores signal while bunch train into capacitors

digitization/data-transfer in pause between trains

400 frames/train

LSDD: Linear silicon drift detector

One dimension is coded into drift-time: 200MS/s while train

data transfer in pause between trains.

600 frames/train

LPD: Large Pixel Detector

analogue pipeline while train digitization between trains

512 (256) frames/train

Þ All extendable beyond 1Mpixel

All around every 5-10 bunch

All might run in parallel

Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05

Idea basic setup of all experiments
Idea: Basic setup of all experiments

Specific to

experiment, here AP_HPAD

Generic for all experiments

Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05

Idea concept for control electronics
Idea: Concept for control electronics

General task:

- Boot

- Collect information

- Synchronize to XFEL

clocks, time

- Synchronize

Interface electronics


Experimental area

- Generate/distribute


- User interface

- Write to backend


- Usage at other laboratories

Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05

Selecting rejecting bunches
Selecting/rejecting bunches


- Best use of limited pipeline in detector-head

- Limit resources for backend

Staged concept:

- Store predefined bunches into pipeline of experiment

- Fast reject (before next bunch): hardware detector,....

- Slow reject: After bunch train

Handle slower information, information from XFEL

- Transfer to backend-system

More fancy selection in CPU-farm

Rates: hard to guess, input from science needed

- gas stream through X-ray-beam:

- solid targets in beam (just first bunch)

- that is not all. Who needs what?/how much?

Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05

Idea data stream to and concept of backend system
Idea: Data stream to and concept of backend-system


- Collect complete frames into one CPU

- Data in mass storage sorted for "Offline"-analysis


- Calculation on frames before sending to mass storage

- Decisions on frame to store/reject inside backend system.

- Rejecting frames on more fancy information from external


- Write data frame-wise to mass storage - easier offline.

Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05

Interface experiments to backend system
Interface: Experiments to backend-system


Data from Pixels written to

RAM and read in other


By that:

One group of frames

transfers to 1 Link to BE.

Still 8 or more

of such modules transfer to

same backend-system

Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05

Xfel pixel readout and control

Need, controlled time sequence:

So that each CPU gets data from all interface-modules

without time conflict

Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05

Idea concept of backend system
Idea: Concept of backend-system









Stage 1: »100 Links/1Gbit/s

Interface electronics



Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05


- Not well defined, what does which of experiment

- AP-HPAD: 2Bytes/pixel/frame is reasonable

- LSDD: Start with over sampling:

Where to reduce to what, has to be a common diccussion

- LPD: Rate expected to be similar to AP-HPAD,

but I haven't seen their proposal.

- First tests of compressions had been not effective

Recent statement for single case was factor 2-4.

Estimate to storage:

1Mpixel * 500bunches/train * 2Bytes/pixel * 10trains/s


Discussion with inputs from backend/science needed to settle


Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05

Time schedule
Time schedule

2007: Experiments write proposal 15-April 2007

end 2007-2013: Designing, Constructing, but also

Laboratory tests and usage at other beam lines

2009(?) DAQ needed for tests - no large CPU-farm

LCLS has 120Hz and not 30000bunches/sec

2013: 1Mpixel dedectors at XFEL 3*(10-20GB)/sec

20xx: Upgrades beyond 1MPixel (e.g. 4Mpixel)

Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05


Concept is there, open to change and do an other way

Two aspects: Control electronics


Ideas about numbers, but a lot of open questions

Discussions needed with input for

- effort in backend

- science requirements

- offline possibilities

- feasibility of interface-electronics

Common effort for all experiments is a strong wish

Peter Göttlicher, DESY-FEB, XFEL-DAQ-2007/03/05