# Presentation: 235598

## The         Level 1 SciFi TriggerA 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

## 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

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

**The Fiber Tracker L1 Trigger Group**

- Como, Oct. 1998

## The Detector

- 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.

- 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 r=70 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

- Como, Oct. 1998

## Physics Goals

**Physics Goals**

- Increase samples by factor 20
- top decays: O(1000)
- W’s: O(100,000)
- Z’s: 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

- Como, Oct. 1998

## Tevatron Impact

- Impact on DØ
- Integrated *L** ** *rad damage in tracking chambers replace
- Shorter bunch crossing interval avoidpileup   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**

- Como, Oct. 1998

## DØ Tracking

**DØ Tracking**

**calorimeter cryostat**

**1.1**

**1.7**

- 1.3 m

- 50 cm

- Solenoid
- 2 Tesla superconducting
- Fiber Tracker
- Eight layers Sci-Fi ribbon doublets  (x-u or x-v)
- 77,000  830 m 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

- Como, Oct. 1998

## Fiber Tracker

**Barrels**
**8 carbon fiber barrels**
**20<r<50cm**
**full coverage to********= 1.7**
**Scintillating Fibers**
**********m ****Ø****, ****multiclad**
**2.6 m active length**
**10m clear waveguide to photodetector**
**radiation hard  (100 krad)            (10 years @ R = 20 cm @ 10****32 ****cm****-2****s****-1****)**
**Fiber Ribbons**
**8 axial doublets**
**8 stereo doublets        (2****o**** pitch)**
**Readout**
**77,000 channels**
**VLPC readout**
**run at low temperature (9 K)**
**fast pickoff for trigger**
**SVXII readout**

- Como, Oct. 1998

## Tracking Trigger

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

- Trigger response for Z ee with 4 min.bias

- Como, Oct. 1998

## Trigger Schematic

- Como, Oct. 1998

## Trigger Architecture

**L1 Trigger**

**L1**

**Global L2 Stage**

**L2 Preprocessors**

**Buffers**

**Silicon**

**SciFi**

**PS**

**Muon**

**Calo**

**p-bar**

**p**

**L3 **
**Processors**

**Trigger**
**Framework**

**10 kHz**

**1kHz**

**10-20Hz**

**tape**

**250kb/evt**

**L0**

- Como, Oct. 1998

## 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

- Como, Oct. 1998

## 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 (MCM’s)
- 2 SIFT + SVX channels per CPS channel

- Como, Oct. 1998

## 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

- Como, Oct. 1998

## FE components: SIFT + SVX

**FE components: SIFT + SVX**

- SIFT : ASIC by ADEPT IC Design in 0.8 m 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

- Como, Oct. 1998

## SIFT Threshold

- Como, Oct. 1998

## SIFT Gain to SVX

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

- Como, Oct. 1998

## Track Finding

- Use digital output from SIFT, and feed into gate arrays
- Match hit pattern against orbit trajectories for all possible tracks from P**T** 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

- Como, Oct. 1998

## 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

- Como, Oct. 1998

## Signal Routing

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

- Como, Oct. 1998

## Track Finding (cont.)

- 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

- Example: binning by offset

- Como, Oct. 1998

## Track Binning

- P**T** binning yields sharper turn-on than offset binning

- Como, Oct. 1998

## 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 >98% 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

- Como, Oct. 1998

## FPGA’s

- Example: Altera 10K devices
- 1 LE = 4-input gate
- number of LE’s  needed     ~ 2.5 × number of equations (track finding)    + ~ 3 × number of equations (serialization)                 + I/O overhead (input multiplexing)
- largest devices hold one full P**T** bin (6 devices/FE board)
- alternative: 2x2X4 smaller  devices)

- Como, Oct. 1998

## Time to L1 Muon

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

- Como, Oct. 1998

## 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 ...

- Como, Oct. 1998

## CFT/CPS Geometry

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

- Como, Oct. 1998

## 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)

- Como, Oct. 1998

## 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...

- Como, Oct. 1998

## 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)

- Como, Oct. 1998

## L2CN

- L2 Concentrator Board
- Collects Data from 1 or 2 Receiver Boards
- Uses token passing to collect data within 2.1 s
- Output _NOT_ sorted by Pt within each of the 4 Pt bins
- Therefore: very large maximum size of list (48 tracks)

- Como, Oct. 1998

## 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

- Como, Oct. 1998

## 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 -> 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

- Como, Oct. 1998

## To L2CFT

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

- Como, Oct. 1998

## Summary

- Overall design for CFT, CPS and FPS complete
- New technology (FPGA’s) 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

- Como, Oct. 1998

## backup slides

- Silicon detector
- etc.

## 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

- Como, Oct. 1998

## The VLPC

**Visible Light Photon Counter (VLPC)**
**Avalanche  Photo Diode**
- well matched to light from fiber ( = 525 nm)
- quantum efficiency 
- fast response, high rate capability
- Si:As (band gap = 0.05 eV)
- high gain (40,000, low gain dispersion
- operates at  8 K < T < 10 K,  6 V < Vbias< 7.5 V

- Como, Oct. 1998

## L1/L2 Trigger Configuration

- L2: Combines
- objects  into e, , j

- CAL

- FPS
- CPS

- CFT

- SC

- MDT

- PDT

- PS

- CAL

- CFT/
- CPS

- Muon

- L1: ET  towers, tracks
- consistent with e, , j

- Muon

- Global
-    L2

- Track

- PS

-   Cal
- e / j / Et

- Como, Oct. 1998

## Trigger Example

_**Central Electrons:**_

- L1 Terms:
-     1 Central EM tower > 7 GeV
-                   plus
-     1 CFT track > 6 GeV/c
-          with Matching CPS
- L1 Rate 220 Hz

- L3 Terms:
-     ET > 20 GeV
-     Shape Cuts
- L3  = 0.01 b,  2 Hz

- L2 Terms:
-     ET > 7 GeV
-     Isolation, Shape Cuts
-     Match Cluster / Track
- L2  Rate 48 Hz

- Como, Oct. 1998

## 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***_

- Como, Oct. 1998