A fast precision tracking trigger with RPCs for high luminosity LHC

upgrade

G. Aielli, B. Liberti,*R. Cardarelli and R. Santonico

University and INFN Roma Tor VergataTIPP Chicago 13 June 2011

Radiation and cavern background

R

Hz/

cm2

Simulation

MDT measurement

CSC measurement

scale to adjust

uncertainty estimate

.L1 trigger

Present trigger : BW TGC

integrating NSW in trigger

Realtime reconstruction of EI segment

• Bunch - ID• Requirement of matched pointing segment fake removal

• track by track correction for • multiple scattering in calo• size of luminous region

smearing by 2-3 mrad to correct Improved pT resolution at L1

Required angular resolution = 1 mrad

Required to send (R, f, dq) to sector logic

max allowed delay 1.088 msec to arrive at sector logic input

X

X

RPC for the Small Wheel upgrade

• Baseline: Hybrid RPC-sMDT detector– Integration of mechanical structure – Sharing of LV and Readout

• RPC is designed to provide:– 1 mrad angular resolution on bending

coordinate– 1 mm resolution second coordinate– Sub ns timing and TOF capability– Full coverage and tracking efficiency > 97%

1st layer 2nd layer

30-40 cm

θ

• The trigger function is provided by an electronic chain measuring the azimuth angle from digital local coordinates. – The zero suppression is applied on

chamber– The angle calculation requires about

50 ns on top of the signal delivery time to USA15

Proposal Strategy and key points • Rate capability enhancement

– New FE electronics allowing a working point with 1/10 of charge delivered in the gas with respect to ATLAS standard achieved

– New detector layout 1+1 mm gap allows to at least halve the total charge delivered for a given signal, improving also the prompt charge distribution and the timing prototype under test 2011 H8 campaign.

• Timing– 1+1 mm gap 0.5 ns sigma for each gas gap

• Trigger based on fast precision measurement (~0.3 mm on a single gap) including zero suppression

• Uncorrelated background pileup suppression strict space-time coincidence – 2 ns width coincidence, correction for signal propagation delay on strips is not needed– Virtual PAD of ~30x1 cm^2– 2/3 majority per chamber (2 chambers per station)

• Integration with sMDT chamber– Sharing mechanics due low profile chamber (3.5 cm)– Sharing LV services and readout for the second coordinate– Provide timing and hit position for the tube

Detector proposal outline • Detector element baseline: 1+1 mm gap

– average total charge delivered 0.5 pC per count– Time resolution of about 0.5 ns (e.g. almost gaussian time distribution)– Full efficiency at 10 kHz/cm^2– Intrinsic space resolution better than 0.3 mm– Resistive plate baseline: ATLAS standard laminate

• Chamber baseline: RPC Triplets– Triplets will be used for redundancy in a 2/3 majority

• Readout Baseline: Eta + Phi on the single gap– Eta segmented in 2 mm pitch strips read out by Maximum Selector.

Optionally the average of each 8 strips can be read by the MDT mezzanine spare channels.

– Phi segmented in ~1 cm strips (variable with the radius), read out by the spare Mezzanine channels.

Trigger proposal outline

• Coincidence type baseline: – (2/3maj AND 2/3maj )Eta

• Space time coincidence– DEta expected to be a ~1 cm. To be calculated by the MC taking

in to account multiple scattering and maximum deflection on the bending coordinate

– Dphi defined by the coincidence width x signal propagation speed

– Time coincidence baseline ~2 ns with 1+1 mm gap (no propagation time correction is needed see after)

– Trigger occupancy baseline estimated in about 44 Hz per station. Can be easily improved

1

1. Phi strips

3. Eta strips

2. Gas volume

4. Spacer2

34

Draft layout of a EIL chamber (triplet)

Fast precision trigger with ( RPC) for ATLAS SW

• Fast precision trigger required :– Precision spatial information from the front-end

electronics of RPC ( 2mm strip pitch ~0.3 mm resolution)

– Fast trigger decision ( 50 ns + cable length latency)

– High rate uncorrelated background rejection

Overall CS=2 result No systematic correction

Strip by strip

Tracking residuals H8 test beam results

Precision spatial information from the front-end electronic of RPC ( 2mm pitch)

RPC

strip

Pitch 2mm

ACES 2011 13

RPC based fast trigger scheme for the SW• The New RPC Front End allowed a new

working mode with a factor 10 less of charge per count 10 KHz/cm^2 as tested

• Tracking trigger: a new type of – low-cost – low-consumption – Fast– compact

electronic readout circuit allows fast precision tracking for local trigger generation on the Eta.

• It works finding the maximum of the RPC charge distribution

CERN, 9 March, 2011

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

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1Integral charge per strip for a RPC gap

Integral charge per strip

Strip coordinate (mm)

2 mm

2

1)/

2

1 /cosh

stripeach over gintegratin

/cosh),(

x

xxx

x

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i

earctgA

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AQ

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Amp and MaximumSelector

Maximum selector• N strips are processed at the same

time (N can vary reasonably in the range of ~10)

• The Maximum selector amplifies the inputs and outputs a negative signal only in correspondence of the strip above a settable fractional threshold, normalized to the average charge provided

• The threshold is chosen to have one or two strips firing (cluster size 1 or 2)

• The decoder transforms the simple digital pattern in to a number representing the hit coordinate on the chamber

• The processing time of (7-10 ns) is highlighted in figure

7-10 ns

Maximum Selector performance

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CH1 inCH2 inCH3 inCH4 inCH5 in

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CH1 outCH2 outCH3 outCH4 outCH5 out

t (ns)

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(mV)

Ch3 slightly >Ch4 Ch4 slightly >Ch3Ch3 = Ch4

Readout and trigger scheme example2 mm pitch micro stripsgrouped by 8

Maximum selector2 transistor 20 mWper channel

decoder

Output : binary number giving the position of the maximum; 8x4 strips =5 bits +1 for CS=2

Strip pitch 2 mm σ = 2 mm / √12 = 580 µm (only CS=1)σ = 2/2 mm / √12 = 289 µm (CS=1 or 2)

Single RPC plane spatial resolution

N1

N2

TRIGGERDECISION:N2-N1 <X

40 ns delay for processing

RPC2RPC1

It will be tested in the summer H8 test beam

Stripped readout plane

Overall Muon station Trigger scheme

N1+T1Optical link

RPC

1

ORMax

selector

RPC

2

ORMax

selector

RPC

3

ORMax

selector

2/3majority

Latch

AND

Decoder+FIFO

1MHz

2kHz x 100 strips

44 Hz

2 ns 10 ns

0.7 kHz

1MHz

RPC

1

ORMax

selector

RPC

2

ORMax

selector

RPC

3

ORMax

selector

2/3majority

Latch

2 ns

0.7 kHz

Chamber 1 Chamber 2

Front End Front EndFront EndAND 2ns

Strip delay correction

• Using the doublet 2 ns coincidence (2/3 majority)• Maximum geometrical delay: Dx*tan /a c negligible• Mean-timer electronics not necessary• Equivalent to ~30 cm segmentation in Phi • Overall virtual PAD of 30x1 cm^2

Dx

Front End

a

2ns

* c/

2

Trigger diagramRP

C 1

OR 5 stripsMax

selector

RPC

2

OR 5 stripsMax

selector

RPC

3

OR 5 stripsMax

selector

2/3majority

Latch

AND

Decoder+FIFO

1MHz/ 5 strips

0.7 kHz x 100 strips (one chamber)

44 Hz

2 ns 10 ns

N1+T1

0.7 kHz on 30 cm virtual PAD

Optical link

Chamber 1

RPC layout details

• The RPC layout follows the MDT one• Eta strip pitch 2mm • External chambers along R have increasing Phi strip pitch • Total channels per wheel ~200000 all included• On wheel power consumption ~4 kW (includes FE, maximum selector and

decoder)• The low voltage supply can vary in the range of 2-3.5 V, can be integrated

with the MDT system

# MDT # Channels # Layers Total Eta # Channels Pitch Total Phi Station Total channels Local Power

tubes/layer Eta/ Layer X Chambers per station Phi/Layer Phi (mm) per station Power (W) per wheel Consumption (W)

EIL0 72 540 2 X 2 3240 125 20 750 80 31920 638EIL1 72 540 2 X 2 3240 125 14 750 80 31920 638EIL2 96 720 2 X 2 4320 125 8 750 101 40560 811EIS0 72 540 2 X 2 3240 100 20 600 77 30720 614EIS1 88 660 2 X 2 3960 100 14 600 91 36480 730EIS2 72 540 2 X 2 3240 100 8 600 77 30720 614Total per Wheel 21240 4050 202320 4046

Conclusions

Detector:• 10 kHz/cm^2 is done• 0.3 mm spatial resolution is

done• Layout of detectors is in

advanced phase

Electronics:• Front-end is done• Maximum selector is done• Trigger strategy baseline

defined to reject the uncorrelated background

• Minimal number of channels and interconnections