The Level 1 SciFi Trigger A Fast Track Trigger implemented with FPGA's

1
The Level 1 SciFi TriggerA Fast Track
Trigger implemented with FPGA's

• Presented by
• Stefan Grünendahl
• at the
• VIth International Conference on Particle Physics
  and Advanced Technology, Como, Oct. 1998

• Contents
• The DØ Upgrade
• Physics Motivation
• Accelerator Environment
• The Scintillating Fiber Tracker
• The SciFi Trigger
• System Overview
• The Frontend Board
• Other Components
• Status and Conclusions

2
The Fiber Tracker L1 Trigger Group

• LAFEX/CBPF, Rio de Janeiro, Brazil
• Mario Vaz - CBPF/LAFEX DEL/UFRJ
• Northwestern University
• Paul Rubinov
• University of California/Davis
• Sudhindra Mani
• Fermilab
• John Anderson,
• Linda Bagby,
• Fred Borcherding,
• Stefan Grünendahl,
• Dave Huffman,
• Marvin Johnson,
• Jameson Olsen,
• Manuel Martin,
• Mike Matulik,
• Pat Sheahan,
• Kin Yip

3
The Detector

• calorimeter replacement of preamps/shapers
• muon system
• replacement of muon chamber readout electronics
• Iarocci drift tubes replace forward muon chambers
• central and forward scintillator pixel layers
  enhance trigger capability.
• DAQ trigger add track and vertex triggering,
  add buffering, add processing power
• central tracker
• 2 T supraconducting coil inside r70 cm
  calorimeter bore
• lead/scintillator preshower detector with
  fiber/VLPC readout
• 16 layer SciFi/VLPC tracker (80k channels)
• 4 barrel / 16 disk Silicon tracker (1M channels)
• forward tracker/preshower scintillator cells
  with fiber/VLPC readout

The DØ upgrade builds upon the strengths of the
existing detector (excellent calorimetry, muon
coverage) and augments it with a high resolution
Silicon/Scintillating Fiber tracker.
4
Physics Goals

• Increase samples by factor 20
• top decays O(1000)
• Ws O(100,000)
• Zs O(10,000)
• Precision Tests of the Standard Model
• Continuation of present DØ physics
  program, with some shift in emphasis
• precision measurements
• (top mass, W mass, ...)
• Constrain the Higgs Boson Mass
• improvements to B physics capabilities
• (Bs mixing, CP violation, )
• QCD with W, Z, photon
• Extend the Discovery Reach
• Significant improvement to physics reach
• few fb-1 data samples allow significant increases
  in the reach for SUSY, leptoquarks,
  W,Z,anomalous couplings.
• Extended luminosity (5 - 25 fb-1) intermediate
  mass Higgs

5
Tevatron Impact

• Impact on DØ
• Integrated L Þ rad damage in tracking chambers Þ
  replace
• Shorter bunch crossing interval Þ avoid pileup Þ
  electronics pipeline
• Systems either Upgraded Cal, Muon,Trig/DAQ
• or Replaced Tracking System
• Solutions involve new Detector Technologies
• Silicon strip detectors, SciFi, trigger
  processors
• The DØ Upgrade is designed to exploit unique
  opportunities offered by the Tevatron during Run
  II and beyond

6
DØ Tracking
calorimeter cryostat

• Solenoid
• 2 Tesla superconducting
• Fiber Tracker
• Eight layers Sci-Fi ribbon doublets (x-u or x-v)
• 77,000 830 mm fibers w/ VLPC readout
• Silicon Tracker
• Four layer barrels (double/single sided)
• Interspersed double sided disks
• 800,000 channels
• Preshowers
• Central
• Scintillator strips
• 6,000 channels
• Forward
• Scintillator strips
• 16,000 channels

1.1
1.7
50 cm
1.3 m
7
Fiber Tracker

• Barrels
• 8 carbon fiber barrels
• 20ltrlt50cm
• full coverage to h 1.7
• Scintillating Fibers
• 830 mm Ø, multiclad
• 2.6 m active length
• 10m clear waveguide to photodetector
• radiation hard (100 krad) (10 years _at_
  R 20 cm _at_ 1032 cm-2s-1)
• Fiber Ribbons
• 8 axial doublets
• 8 stereo doublets (2o pitch)
• Readout
• 77,000 channels
• VLPC readout
• run at low temperature (9 K)
• fast pickoff for trigger
• SVXII readout

8
Tracking Trigger
Trigger response for Z ee with 4 min.bias

• Feed all axial fibers plus preshower into gate
  arrays
• Trigger if a fiber combination is consistent with
  PT gt (1.5,3,6,8) GeV
• Tag categories (incl. CPS info) track, isolated
  track, electron, ...

9
Trigger Schematic
10
Trigger Architecture
p-bar
p
Muon
Silicon
SciFi
Calo
L0
PS
L1 Trigger
L1
10 kHz
Trigger Framework
L2 Preprocessors
Global L2 Stage
Buffers
250kb/evt
1kHz
L3 Processors
10-20Hz
tape
11
System Overview

• L1 System overview
• Frontend Board (on cassette)
• VLPC signal discrimination
• track pattern matching
• track sorting list building per 4.5 sector
• Receiver Concentrator system (two crates)
• list building per octant (L1)
• list building per sextant (L2)
• L1-CFTTM and L2pp links
• L1 CFT Trigger Manager
• forms trigger (and/or) terms for L1

12
SciFi VLPC Cassette

• 1024 VLPC channels
• two FE boards two 4.5 trigger sectors
• CFT Trigger Boards
• 480 CFT channels, 32 CPS channels/board
• 1 SIFT SVX channel per CFT channel housed in 7
  Multi Chip Modules (MCMs)
• 2 SIFT SVX channels per CPS channel

13
FE Board Signal Flow

• VLPC
• (Charge Divider) (for Preshower Detectors)
• SIFT Discriminator (with SVX) in Multichip
  Module
• Hit Latch
• Shipping to/from Neighbour FE Board
• Tracking FPGA
• Sorting of Track Lists
• Shipping to Muon L1 System
• Preshower Matching
• Sorting of (matched) Track Preshower Lists
• Shipping to Receiver Cards

14
FE components SIFT SVX

• SIFT ASIC by ADEPT IC Design in 0.8 mm
  technology
• 1 SIFT - SVX channel per CFT Fiber
• 2 SIFT - SVX channels per preshower channel
• Housed in 1 MCM (2 trigger thresholds - 1 high
  and 1 low)

timing
15
SIFT Threshold
16
SIFT Gain to SVX

• SIFT x2 Gain is 0.4 into the SVX
• x1 Gain is 0.2
• Very linear

17
Track Finding

• Use digital output from SIFT, and feed into gate
  arrays
• Match hit pattern against orbit trajectories for
  all possible tracks from PT of 1.5 GeV/c to
  infinity
• tracking efficiency baseline algorithm uses 8
  out of 8 layers
• with an option to require only 7 out of 8 layers
  - at highest Pt
• Minimize backplane connections Track anchor
  layer is the outer layer (layer 8)
• A 1.5 GeV/c track can span 2 sectors
• Hits are transmitted across the backplane from a
  sector on either side (layers 1-7 CPS) for
  track matching

18
Seamless Tracking

• Seamless tracking requires fiber sharing between
  nearest neighbor sectors
• 1.5 GeV contained in 2 sectors
• Layer 1 anchor would require two neighbor sharing
  of CPS

19
Signal Routing

• Division between 2 FE boards on a cassette
• Green and Yellow are sent left
• Red and Yellow are sent right

20
Track Finding (cont.)
Example binning by offset

• All tracks are binned into 4 Pt bins - boundaries
  are user settable
• Max of 6 tracks per Pt bin
• 6 highest Pt tracks are sent to muon
• Tracks are sent in Pt bin order - highest first
• Tracks are not Pt ordered within the bin
• Equations can be adapted to
• as-built geometry
• luminosity
• special triggers

21
Track Binning

• PT binning yields sharper turn-on than offset
  binning

22
Track Finding (cont.)

• Problem huge, sparsely populated space of track
  solutions has to be collapsed for output
• Solution Priority encoding of found tracks only
  the highest (90 eff) and lowest (extra 9 eff)
  Pt tracks per Pt bin are selected for each
  fiber in layer 8 (2 tracks per fiber)
• Allows fast hardware algorithm
• Monte Carlo studies indicate only 1 real track
  per fiber is gt98 efficient
• Need 2 tracks because of extra hits at high
  luminosity which create a fake track (7 points on
  original track and 1 fake)
• Fake track can be higher or lower in Pt than real
  one

23
FPGAs

• Example Altera 10K devices
• 1 LE 4-input gate
• number of LEs needed 2.5 number of
  equations (track finding) 3 number of
  equations (serialization) I/O
  overhead (input multiplexing)
• largest devices hold one full PT bin (6
  devices/FE board)
• alternative 2x2X4 smaller devices)

24
Time to L1 Muon

• We project that all the tracks are at MUON by
  800ns absolute

25
Trigger Concentrator System

• Common design for CFT/CPS, FPS and Forward proton
  detector
• CFTCN, FPSCN, ...
• Four Board Types in Special Crate
• Receiver board
• L1 Concentrator board
• L2 Concentrator board
• Controller board
• L3 Read-Out
• diagnostics
• mark and pass ...

26
CFT/CPS Geometry

• Geometry for the CFT L1 and L2
• Octants to L1CFT (matches calorimeter geometry)
• Sextants to L2CFTpp L2STTpp (matches silicon
  geometry)

27
L1 Receiver/Concentrator

• L1 data is processed for each octant (10 sectors
  45 degrees)
• Creates 17 sums
• 16 -- Number of tracks in each of 4 Pt bins,
  cluster(x2), Isolated(x2)
• Total number of hits in the octant
• 2 L1 outputs per card so can feed 2 CFTTM trigger
  manager boards (32 AND/OR)
• Passive splitting would allow up to 4 CFTTM
  trigger manager boards (64 AND/OR terms)

28
L1CFTTM

• L1 Trigger Manager
• identical to the one used in muon system
• sixteen 1 GB/s serial inputs (copper)
• sixteen AND/OR terms to Trigger Framework
• can be global terms or e.g. eightfold (per
  octant)
• FPGA to compute trigger terms from input data
• Scalable just add more boards...

29
L2CFTCN

• L2 data is processed by a separate set of boards
• 60 degree sectors are required for STT
• does not match 4.5 degree sectors of CFT
• Create 3 approximately 60 degree sectors in each
  180 degree half -
• 13 FE sectors (58.5 degrees)
• 14 FE sectors (63 degrees)
• 13 FE sectors (58.5 degrees)

30
L2CN

• L2 Concentrator Board
• Collects Data from 1 or 2 Receiver Boards
• Uses token passing to collect data within 2.1 ms
• Output NOT sorted by Pt within each of the 4 Pt
  bins
• Therefore very large maximum size of list (48
  tracks)

31
Tracks for L2

• Sent in Pt bin order
• but NOT Pt ordered in bin
• First - Highest bin for all sectors starting with
  first sector
• Next highest for all sectors
• Third highest for all sectors
• Fourth highest for all sectors
• Transfer stops after track 48

32
To L2STT

• STT searches SVX data (in L2/L3 event buffer)
  for hits in CFT road
• Purpose offset vertex trigger
• Two 60 degree sectors are sent to every L2STT
• STT selects tracks roads that pass through its
  local silicon -gt this gives a large CFT overlap
  for STT roads
• It takes less than 5 µs to send the data
• The maximum number of tracks sent to a given STT
  fiber road card is 48 times 2

33
To L2CFT

• Each 60 degree sector is sent to L2CFT.
• Data is identical to that sent to the L2STT

34
Summary

• Overall design for CFT, CPS and FPS complete
• New technology (FPGAs) meets
• Timing constraints
• allows feeding of L1 info to other detectors
• Flexibility
• allows for adaptable thresholds/PT bins
• allows to load as-built detector geometry
• Scalability
• can add trigger terms by adding TM cards

35
backup slides

• Silicon detector
• etc.

36
List of Terms

• CPS - Central PreShower
• FPS - Forward PreShower
• CFT - Central Fiber Tracker
• FE - Front End electronics board
• SIFT - Scintillating Fiber Trigger chip
• SVX - SVX2e chip
• MCM - MultiChip Module
• L1CFT - CFT Level 1 Trigger
• TM - Trigger Manager
• CN - Concentrator System

37
The VLPC

• Visible Light Photon Counter (VLPC)
• Avalanche Photo Diode
• well matched to light from fiber (l 525 nm)
• quantum efficiency 80
• fast response, high rate capability
• SiAs (band gap 0.05 eV)
• high gain (40,000) , low gain dispersion
• operates at 8 K lt T lt 10 K, 6 V lt Vbiaslt 7.5 V

38
L1/L2 Trigger Configuration
Cal e / j / Et
CAL
CAL
FPS CPS
PS
PS
Global L2
CFT/ CPS
CFT
Track
SC
Muon
Muon
MDT
PDT
L1 ET towers, tracks consistent with e, m, j
L2 Combines objects into e, m, j
39
Trigger Example
Central Electrons
L2 Terms ET gt 7 GeV Isolation, Shape
Cuts Match Cluster / Track L2 Rate 48 Hz
L1 Terms 1 Central EM tower gt 7 GeV
plus 1 CFT track gt 6 GeV/c
with Matching CPS L1 Rate 220 Hz
L3 Terms ET gt 20 GeV Shape Cuts L3 s
0.01 mb, 2 Hz
40
Front End Crates

• Directly on cryostat
• 200 boards (80 CFT Trigger, 76 CFT Stereo, 32
  FPS, 10 CPS Stereo), 4 slots (two cassettes) for
  spares
• up to 16 boards/crate

Cryostat map