An RPC-Based Technical Trigger for the CMS Experiment

12th Workshop on Electronics for LHC and Future Experiments Valencia 25-29 Sept. 2006 F. Loddo I.N.F.N. Bari

An RPC-Based Technical Trigger for the CMS

Experiment Outline:

Requirements Implementation Performance during CMS MTCC

Flavio Loddo

I.N.F.N. Bari

On behalf of the CMS RPC/Trigger Collaboration


Motivations and requirements

Goal of this project is to produce an RPC-based Cosmic Ray Trigger for: the Commissioning of RPCs, to test the detector efficiency the Magnet Test-Cosmic Challenge later running of CMS as Technical Trigger, to calibrate the

detectors in the off-beam periods

The main requirements are: Compact Inexpensive

Use existing infrastructures and services (electronics and cables in the experimental hall)


Block diagram of CMS RPC Electronics full chain

datacontrol (DCS)

DetectorDetector

Periphery

Trigger Crate (12)

LMUX

LINK BOARD (Slave)

FEC

FEB

LINK BOARD (Master)

FEC

FEB

electrical

LMUX

TRIGGER BOARD

PAC

PAC

GB&

SORTER

SPLITTER BOARD

FanOut

Rx

SORTER Backplane

SORTER

SORTER

SORTER

GB & SORTER BOARD

SORTER

SORTER

SORTER

DATACONCENTRATORCARD

EVENTCONCENT

electrical

Sorter Crate (1)

Counting Room

SORTER BOARD(on Backplane)

SORTER

SORTER

SORTER

Tx

electrical

TTc Rx

Diagnostics

108 12

2

1

3

144 links/crate1732/total

CONTROL BOARD

CCU

Link Box

optical

Tx

Tx

Rx

RxReadout

Concentr.

60

96 LB boxes

108 GOHlinks

"Vme" DCS

"Tracker type, DOH based " DCS

datacontrol (DCS)

DetectorDetector

Periphery

Trigger Crate (12)

LMUX

LINK BOARD (Slave)

FEC

FEB

LINK BOARD (Master)

FEC

FEB

electrical

LMUX

TRIGGER BOARD

PAC

PAC

GB&

SORTER

SPLITTER BOARD

FanOut

Rx

SORTER Backplane

SORTER

SORTER

SORTER

GB & SORTER BOARD

SORTER

SORTER

SORTER


EVENTCONCENT

electrical

Sorter Crate (1)

Counting Room


SORTER

SORTER

SORTER

Tx

electrical

TTc Rx

toDAQ3 Slinks

Diagnostics

108 12

2

1

3


CONTROL BOARD

CCU

Link Box

optical

Tx

Tx

Rx

RxReadout

Concentr.

60

96 LB boxes

108 GOHlinks

"Vme" DCS


datacontrol (DCS)

DetectorDetector

Periphery

Trigger Crate (12)

LMUX

LINK BOARD (Slave)

FEC

FEB

LINK BOARD (Master)

FEC

FEB

electrical

LMUX

TRIGGER BOARD

PAC

PAC

GB&

SORTER

SPLITTER BOARD

FanOut

Rx

SORTER Backplane

SORTER

SORTER

SORTER

GB & SORTER BOARD

SORTER

SORTER

SORTER


EVENTCONCENT

electrical

Sorter Crate (1)

Counting Room


SORTER

SORTER

SORTER

Tx

electrical

TTc Rx

toGlobalMuonTrigger

Diagnostics

108 12

2

1

3


CONTROL BOARD

CCU

Link Box

Tx

Tx

Rx

RxReadout

Concentr.

60

96 LB boxes

108 GOHlinks

"Vme" DCS


444 + 84 (HO) links

opticaloptical

The Resistive Plate Chambers are part of the CMS Muon Trigger System


Cosmic Trigger with RPC Trigger electronics?

In CMS the RPC Trigger Boards are connected in vertex geometry, which is not adequate to cosmic trigger

It could be possible with additional optical splitters and TBs, but the new proposed architecture provides redundancy and an independent tool for calibration and debugging

Overall costs are similar to the solution with additional splitters and TBs


RPC Technical Trigger: Implementation

Phase I: Sector-based Trigger for testing RPC (and DT) during Commissioning and MTCC

Phase II: Wheel-based trigger (Technical trigger) to be used during CMS

RBC (RPC Balcony Collector), on the detector

RBC + TTU (Technical Trigger Unit), in the Counting Room


RPC Technical Trigger: Implementation

Experimental Hall

30

6 Fibers/wheel

To Global Trigger

LBBox

RBC

LBBox

LBBox

RBC

LBBox

LBBox

RBC

LBBox

LBBox

RBC

LBBox

LBBox

RBC

LBBox

LBBox

RBC

LBBox

TT

UT

TU

TT

UT

TU

TT

U

5 wheel Triggers

Counting RoomT

echn

ical Trig

ger L

og

ic

Tech. Trigger


RBC Implementation The RPC signal cables (LVDS) are connected to the Link Boards (LB)

for synchronization, data compression and optical conversion

Each LB reads 96 strips of one partition (1 roll = half/chamber) and can produce 1 OR to be used for our goal

On LB front-panel, the CSC connector is used only in the Forward region, to send synchronization signals from RPC to CSC. It can be used in the Barrel to send signals from LB to RBC

In the endcap, the cosmic muon rate is very low and not adequate for fast monitoring run with cosmics

↓Technical Trigger involves only the Barrel RPCs

Each LBBox (LBB) houses 13 or 15 LBs of 1 Barrel Sector The LBBs are distributed in the 30 periphery racks in groups of 2 We can house 1 RBC/rack 1RBC/2 sect 30 RBCs in total


•RBCs will be housed in slot #12 of LBBox of odd sectors. The ORs and LHC_Clock are collected by 2 FrontPlanes

•RBC_Fake (just a connector collecting the ORs to be sent to RBC) will be housed in slot #12 of LBB of even sectors

•I2C (from Control Board) and Power Supplies will be accessible on the backplane

RBC Implementation

LBB with RBC

LB FrontPlane 1 LB FrontPlane 2

LB

LB

LB

LB

LB

LB

LB

LB

LB

LB

LB

LB

LB

Co

ntr

ol

Bo

ard

Co

ntr

ol

Bo

ard

RB

C

RBC FP1 RBC FP2

7 ORs 6 Ors + CLK + RCO

OUT

7 ORs

1

LB FrontPlane 1 LB FrontPlane 2

LB

LB

LB

LB

LB

LB

LB

LB

LB

LB

LB

LB

LB

LB

LB

Co

ntr

ol

Bo

ard

Co

ntr

ol

Bo

ard

RBC FP1 RBC FP2

7 or 9 ORs 6 Ors

LBB without RBC (and with RBC_FAKE)


•Receive 2x13 (or 15) ORs from LB (LVDS)

(OR of 96 strips (1 bi-gap = half RPC))

•Mask noisy/dead Ors

•Produce Sector Trigger (LVDS) according to pre-loaded patterns, with selectable Majority level (16)

•Force selected ORs to be in the coincidence, to

increase trigger selectivity

• Introduce latency (step = 25 ns) for synchronization with other triggers

•I2C Interface

•Transmit input OR to Counting Room using the GOL optical transmitter for Wheel-based trigger

RB4

RB3

RB2_OUT

RB2_IN

RB1_OUT

RB1_IN

Generic Barrel Sector

RBC Main Features


RBC Main Features

Based on Xilinx Spartan-3 Configure with JTAG through Flash Prom Not inserted in the CCU chain controlling LBs

firmware upgrade only in situ This is not a major limitation, since all internal

parameters and muon patterns are configurable via I2C The ORs will be available also in the Counting Room,

where the TTU Boards might be upgraded “on line” through Slow Control


RBC Block diagram

LV

DS

Receiver

GOL

QPLL

Trigger #1 (LVDS)

I2C AgilentHFBR-5720

40 MHz LHC Clock

Pattern

C

om

parato

r

Reconf

Controller

LV

DS

Drive

r

FPGA (Spartan III)

Trigger #2 (LVDS)

to TDC

Config. PROM

Backup Flash

EpromD

elay u

nit

(25 ns T

aps)

TLK2501

Only for test

purpose

Input ORs

13+13(or 13+15)

JTAG


RBC SEU Strategy

On the detector periphery the environment is not critical:

•Total DOSE < 1 krad

•Neutron flux (E > 20 MeV) < 100 cm-2s-1 Fluence < 1010 cm-2

Optical transceiver: Agilent HFBR-5720L

Tested by E. Denes, T. Kiss et al. (ALICE)

• Fluence: 1011 n/cm2 at different energies: 10 MeV, 150 MeV, 180 MeV

Serializer

Rad-tolerant GOL chip developed at CERN

The most sensitive device is the SRAM – FPGA!


RBC SEU Strategy

Since also LBs are based on Spartan-3 devices, the same strategy is adopted to mitigate the SEU effects on FPGA:

•periodical re-load configuration SRAM from Flash EPROM (extremely robust against our level of irradiation)

•upon the receipt of the Reconf signal from LB, the time to load the bitstream is ~ 200 ms

•backup Flash Memory to store internal registers for fast reload

Test on Spartan-3•Performed by Fabula et al. (Xilinx) and presented at MAPLD 2004

•Test facility: Los Alamos Neutron Science Center

bit ~ 3.0x10-14 cm2/bit ~ 2.9x10-8 cm2 (E > 10 MeV)

Time to Configuration upset = 1/(*Flux) ~ 95 Hours/device


RBC prototype


Backplane connector:•3.3 V•2.5 V•GND•I2C

Front side

RBC prototype

•10 Layers PCB 14x14 cm2

to be housed on Mother Board, fitting LBBox dimensions


Since last June, 2 RBC prototypes + 1 RBC_fake are providing two Cosmic Triggers to the

detectors involved in the CMS Magnet Test Cosmic Challenge

W+2: Sect. 10 Sect. 11

Sect.10-11 patternsOR

RBC2

W+1: Sect. 10 RBC1

RBC Trigger in MTCC

(but only Sect.10 equipped with LBs during MTCC phase I)

RPC-TB pointing to the tracker

RBC LVDS-LVPECL Transceiv.

LVPECL Receiv.

LVDS Driver

LTC or

PSB

150 m (shielded twisted cable)

The RBC triggers were well synchronized with RPC-TB trigger and with other muon triggers (DT and CSC)


RBC Trigger rate in MTCC: rate plateau

Some measurements to find the working point of the RBC1 and RBC2 triggers vs. variation of the RPCs HV set points

Majority 5/6 - trigger rate ~30 Hz per wheelMajority 6/6 - trigger rate ~13 Hz per wheel

W1/S10 RB1in

0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

16,00

8,4 8,6 8,8 9 9,2 9,4 9,6 9,8

HV(kV)

Tri

g R

ate

(Hz)

Majority: 6/6


RBC in MTCC: Iguana Event Display

Combined offline RPC (green) and DT digis


Examples of DQM plots: RPC Barrel Wheel +2 Sector 10

Station 4


Examples of Drift Tube occupancy plots triggered by

RBC

Z


•Receive optical link from RBCs

•Combine ORs from 1 Wheel and produce Wheel Cosmic Trigger Global Trigger as Technical Trigger

Wheel Trigger OpticalTransceiver

TLK2501Pattern

Recognition Processor

TTCrxQPLLVME InterfaceVME Interface

Comm. line

Deskewed HF clock

LHC Clock

6 Fibers

Phase II: Wheel-Based Cosmic TriggerPhase II: Wheel-Based Cosmic Trigger


The required functions are performed by the RPC Trigger Board (designed by Warsaw RPC Trigger Group):

• TTU needs:

1. 30 signals from detector: 1.6 GHz GOL drive multimode fiber;

2. each fiber transfers 26 or 28 bits @ 40 MHz;

3. signals must be synchronized;

4. pattern logic to make cosmic trigger

• RPC Trigger Board offers:

1. 18 inputs: 1.6 GHz GOL driven multimode fiber;

2. Opto-synch FPGA/3 optical inputs and maximum 72 bits @ 40 MHz;

3. Up to 4 PAC mezzanine boards for pattern recognition algorithm

RPC Trigger Board as TTU


TB as Technical Trigger UnitTLK2501 Max. 72 bit/synch

OP

TO

B

RD

OP

TO

B

RD

OP

TO

B

RD

OP

TO

B

RD

OP

TO

B

RD

OP

TO

B

RD

OP

TO

B

RD

OP

TO

B

RD

OP

TO

B

RD

SY

NC

HS

YN

CH

SY

NC

HS

YN

CH

SY

NC

HS

YN

CH

Pattern Comparator

Pattern Comparator

Pattern Comparator

Pattern Comparator

DAQ Concentrator

VME Interface

VME Connector

Custom Backplane Connector

Ghostbuster Sorter

• 3 Trigger Boards can be used to cover the whole Barrel, using 12 links per TB

• The Stratix2 PAC mezzanine board have huge amount of logic cells, enough to implement cosmic pattern recognition: 1 or 2 PACs should be enough

• VHDL code for data transmission and Internal Interface (VME driven internal bus) developed by Warsaw Group can be used

• Warsaw software for FPGA upload and diagnostic tools can be used

• TTU custom backplane (for TTCrx and to send out the Trigger) must be designed, but can be derived from the design of TB backplane


Conclusions

The RPC Technical Trigger project is under progress: 2 RPC Balcony Collector (RBC) prototypes are in

use for MTCC to provide 2 Sector-based triggers The full production is expected to be available

before the end of 2006 The design of the new firmware and the backplane

for the Trigger Board-TTU will start in few weeks

An RPC-Based Technical Trigger for the CMS Experiment

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