SL1Calo Input Signal-Handling Requirements Joint Calorimeter – L1 Trigger Workshop November 2008...

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SL1Calo Input Signal-Handling Requirements

Joint Calorimeter – L1 Trigger WorkshopNovember 2008

Norman Gee

Norman Gee -Joint Calo/L1Calo Workshop

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Overview

• Input processing and tower building

• Channel mapping

• Special processing

– LAr Strips

– Preshower

– Tilecal rear sampling

• Instrumentation

• Error Handling, Testing, Readout


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Input Processing 2008

Present Trigger Tower summation & digitisation

Cell ShapeGain

TowerSum

PatchPanels

On/Off FADC

FIRFilter

LUT

Sum

On Detector

USA 15

Delay

Summing Cellswith Equal PulseShapes,Equal Gains

Summing inGap region

AnalogueSum

Receivers

,Matrix

AnalogueET

Sync

Time-alignedTowers

CalibratedTowers

e

Jet

PF


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Digital Processing Elements 2017

• Need to improve L1Calo selectivity – particularly better electron purity

• Assume** move to “Minitowers” in place of trigger towers

– Separate summation in depth

– LAr: smaller area in ,• E.g. 0.05 x 0.1 (front) • 0.05 x 0.05 (middle)• 0.05 x 0.1 (back)• Use pre-shower detector

– Tile: Separate in depth, 0.1 x 0.1• Use 3rd sampling in trigger?

• ** there are many assumptions in this talk - Details need Monte Carlo study


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Building minitowers from digital signals

• Easiest for L1Calo if all cells contributing to a given minitower…– are brought to a common analogue phase and shape before digitisation– digitised by FADCs aligned with pulse peak, using a common clock (for Mux)– (Not assumed to have equal gains)

Cell ShapeGain

MuxOn/Off

FIRFilter LUT

SumOn Detector

USA 15

FADC

Digitise Cellswith Equal PulseShapes andEqual phaseper minitower

DemuxSync

Time-alignedCells

CalibratedMiniTowers

OptTx

CalibMux

MultiplexedMiniTowers

to algorithms

Delay OptRx

NoiseCut


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Building Digital Minitowers

• What happens if cells are not same shape when digitised?– Should not happen if they are all from the same depth sampling

• Answer – add extra digital filter to adjust shape digitally before addition– Effect on resolution needs checking– Implies very large number of coefficients to download

Cell ShapeGain

MuxOn/Off

FIR+ PF LUT

SumOn Detector

USA 15

FADC

Digitise Cellswith Equal PulseShapes andEqual phaseper minitower

DemuxSync

Time-alignedCells

CalibratedMiniTowers

OptTx

CalibMux

MultiplexedMiniTowers

to algorithms

Delay OptRx

NoiseCut

Re-shape


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Uncertainties

• Some questions to be looked at with MonteCarlo:

– What pulse shape is best for the trigger?

– Do we need to follow the baseline?

– What digitisation frequency do we need?

– What trigger tower size is best?

– Do we use the peak-finding in sampling 2 to sample the other layers?• (Not in Tilecal - would wreck isolation)


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Current Channel Organisation

• Present Cluster and Jet-ET processor is organised in quadrants per crate

– (one quadrant per Cluster crate, two quadrants per Jet-ET crate)

– Increasing along crates, increasing up the backplane• Input (on LVDS links, via the backplane) is organised as an - matrix

– To populate the algorithms near the top and bottom of the crate, some data is duplicated, and copies are sent on more than one link

• Pre-processor modules are organised to provide this– So analogue signals must be in a matrix– Very different from calo signal organisation

• Large installation of analogue patch panels

• This is a big issue for SL1Calo because of thehuge number of signals and high speeds

Electromagneticcalorimeter

Hadroniccalorimeter

Trigger towers (


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Special Processing

• Strip layer:• We should find and count clusters. Output data to contain details, e.g.

– Flag to indicate one cluster or many position of the highest peak

• If ATLAS uses track trigger at L1 or L1.5, it will be useful to match tracks to precise cluster positions

• Preshower:• Not used in L1Calo at present. Real-time energy correction for dead material?

• Tilecal rear sampling– Additional muon indicator, perhaps just needs lower and upper threshold?– Also useful in cosmic trigger– Need to extract these data somewhere from SL1Calo input processing, to be

built in sent to SL1Muon


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Instrumentation, Calibration

Rate meters

• Present Preprocessors include rate metering and histogramming

– Rate meters are in constant use to help control hot towers

– Histogramming not so much used• We can run rate meters or histograms, not both

• Ratemeters measure the rate of tower hits above a programmable threshold

• We should presumably include rate metering for minitowers

Calibration

• LAr RODs have special functions for calibration

• With ten times the number of towers, this becomes important for SL1Calo as well

– We should agree on the calibration procedures early on, and include in the minitower building


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Error Handling, Testing, Readout

• Understanding errors is critical in L1Calo. A single high-rate error source on a digital link can kill us. Links must be error-free to 1 bit in 1010

– We have built-in error detection (parity error counting) and error handling (zero the bad data)

• Need to think about SL1Calo data link quality, error detection & correction (including links from calorimeters)

• We can inject digital data at many places in L1Calo, and check correct data processing and readout when running at full rate– Extremely useful (vital !!) during construction, then to verify connectivity,

check algorithms,… • must be included in SL1Calo

• We read out inputs and outputs from every module– Intermediate info can be discarded in RODs if the system is stable– What will Calorimeter readout contain?

SL1Calo Input Signal-Handling Requirements Joint Calorimeter – L1 Trigger Workshop November 2008...

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