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Status of the Test System of the MWPC for the LHCb Muon

System

Andre’ Massafferri

(Universita’ Tor Vergata – INFN sezione II - Roma)

V. Bocci, R. Nobrega (Universita’ La Sapienza – INFN sezione I - Roma)

G. Carboni, E. Santovetti (Universita’ Tor Vergata – INFN sezione II - Roma)

IEEE San Diego 2006

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5 Muon Stations

Calorimeters

Tracker RICH-2

Vertex Locator

Magnet

RICH-1

Muon Detectors

Iron Filters

Chamber

MWPC in Muon System

MWPC task Fast muon triggering Muon identification

5 Stations divided in 4 Regions 19 different geometries 1368 chambers More than 120K channels

LHCb: an experiment for precise measurements of CP violation and B

mesons rare decays

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GoalFriendly and automatic procedure for diagnose

of errors of the Chamber + Electronics system

Check of our 1368 MWPC(~ 128000 channels) before installation

Database for Online Monitoring

1 - Chamber & Front-End Electronic (FEE)

2 - Test setup and description

3 - Results

4 - Cross check using cosmics

5 - Conclusion

Topics

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MWPC Design 40 pF < Cdet < 220 pF (geometry) Wire (Anode) & Pad (Cathode) readout 4-gaps MWPC gap size: 5 mm (wire plane centered) gas mixture: Ar/CO2/CF4 (40:55:5) wire spacing: 2 mm, mechanical tension: 65 gr HV = 2.650 KV gas gain: G ≈ 50 000 gain uniformity: ≤ 30%

Not wired panel

Wired panel

Side bar

Wire fixation bar

Spacer

MWPC Sandwich

M5R3 full equipped

M3R3 panel

6 FEEsSingle padFaraday cage

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Chamber & Front-End

Electronics (FEE)

CARIOCA: 8 chs current-mode Ampl • signal amplification• tail cancellation• base line restoration• digitalization into LVDS lines

DIALOG: 16 chs control chip

• 8-bits DACs for threshold voltage• width and delay adjustment• masking• 24-bits scaler • pulse injection feature• access via LVDS-based I2C protocol

The acquisition basic unitChamber: 2

bigapsLVDS

READOUTCh(AB)OR

ORSPB

CONTROL

Ch ACONTROL

Ch B

Single padlogic

Spark protection board

2 CARIOCAs + DIALOG

= FEE (CARDIAC)

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Band-width: 10 / 25 MHz depending on Polarity Sensitivity: 16 to 8 mV/fC ENC: 0.3 to 2 fC Min Detectable charge: about 40

mV/sens

FEE characteristic I

charge Anode Q > 14 fCCathode Q > 8 fC

Qth

µ signal

time

dead region

noise

Min Det

charge

AFTER TEST FEE DATABASE

Capacitance (pF)

Capacitance (pF)

Capacitance (pF)

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The Discriminator Differential Threshold Voltage

o Less sensitive to Noiseo Vth Nominal: 0 to 1.3 V o Vth Effective Abs(VrefA – VrefB) VrefA & VrefB obtained from Vth Nominal

o OffSet

(Vth Nominal @ Min Vth Effective)

740 to 860mV

FEE characteristic II

offset Vth Nominal

VrefA

VrefB

Vth Eff

Vth Nominal

Noise Rate

Analysis of

Noise X Threshold

Rate method

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Test Setup Control FEE via I2C (Service Board &

CANopen) Internal Counters (Dialog feature) External Counters (ACQ & Gate Boards and USB-VME) BarCode Reader PC (WIN, Visual C++ & ROOT) Barcode and Test Program

Full Equipped Chamber (UNDER TEST)

FEE

ACQ

LVDS

TTL

Gate Board Task

input

output

UNDER TEST

USB

Service Board (SB) controls FEE in the experiment.

ACQ is a 64-channels VME module used as external counter.

Gate Board translates the SB gate signal sent to the FEE to be used also by the ACQ.

MWPC

FEE

FEE

FEE

FEE

8X16X

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Association of Chamber to FEE boards LOCATION

DATABASE

Extraction of Chamber and FEE parameters

The Test

Protocol

Read the Chamber and FEE barcodes

USER TASK

In dressing area(1)

Preparation

SOFTWARE GOAL

Complete Test

Initialize

Press Check LVDS output line

Check Chamber-FEE association

Search for Dead Channels

Estimate Cdet (Rate Method)

Search for Short-Circuit

Search for Open Channels

Check Level Noise @ 3 specific

thresholds

Read Chamber barcode

In test area

(2) TestProcedure

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Check if FEE is working properly (pulse injection, internal counters, output lines)

Inject 500 pulses to all channels

Reading by dialog & ACQ counters

Comparison

First Step

Check LVDS output line

Cable CheckingCheck if cables are swapped

It can be useful to check cables in pit

Pulse Injection Test

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Check the Position of FEE comparison of OFFSET values

obtainedhere to the ones found on FEE

database

Check dead FEE channelsby the simple existence of Noise (min

3 pts)

Second Step

Threshold Scan Test

Check Chamber-FEE association

Search for Dead Channels

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Estimate Cdet (Rate Method)

Search for Short-Circuit

Search for Open Channels

Third Step: Cdet

The detector capacitance determines the noiselevel since it acts as aseries noise source

SPB 2 nF

bigap

Threshold Scan Test

Rate=

Nexp 2 ENV2

-Vth2

offsetMin Det signalOffset &

Min detect signalENV ENC(Cdet)

Sensitivity(Cdet) Cdet

functionsNoise fit

Short-Circuit : Noise (2nF)~Noise (300pF) saturation due CARIOCA band-width

Open Channel : Cdet ~ 0pF easy to discriminate even for M2R2 40pF

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<Cdet>

Third Step: Cdet

Criteria

channels

Cdet

+-

> 2.5

> 3 or

ERROR

Mostly associatedto setup itself

Very important Alarms !

Cdet > 300 pFor

Cdet < 20 pF

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Criteria for Noise Rateat 3 specific Thresholds

OK / WARNING / ERROR

if Rate > 1 KHz

Cathode Readout: 6 7 8 fC

Anode Readout: 10 12 14 fC

Check Level Noise @ 3 specific

thresholds

Fourth

Step

Electronic Noise can be ~100 Hz / channel

1 KHz in Noisy channels is acceptableChamber Eff >99%

@ Th = 8 fC (cathode) & 14 fC (anode)

threshold

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Results Format: DATABASE

Diagnostic file

Output file

PLots & Histograms

• Detailed description of all steps through the pre-defined ranges of: OKs , Warnings, Errors messages

• List of 33 relevant parameters, including FEE database.

• Allow further comparisons

Leds & Buttons

OKWarningERROR

Info: Where is the problem !

• Histograms of the main output parameters

• Graph of the Noise X Thr of all FEE/channels

• OffSet signature

• Vertex position (cross of each combination of two channels)

• Acquisition facility: any threshold/gate-time/ bigap-logic

• PLOT

Raw-Noise file• All points in Threshold Scan

• Can be used for further re-analysis and comparisons

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Results: First Chambers tested

@ LNF

Cdet

Alarms !

Those tests were performed using

a MaxNoiseRate cut = 2 MHz

Recently we have observed a FEE patology that distorted the Th-

Scan at high Noise Rate

We upgrade

MaxNoiseRate = 20 MHz

to detect it

About 10% needed some intervention

pointed out by the Test System Mostly Change FEE (dead,noisy)

Also bad connection, SPB, I2C (chain)

100 - M5R4 Cdet (sim) = 220 pF22 - M3R3 Cdet (sim) = 140 pF06 - M5R2 Cdet (sim) = 120 pF

128 - chambers

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More Plots:

Noise @ th = 10 fC & 6 fC

Noise @ th = 12 fC & 7 fC

Noise @ th = 14 fC & 8 fC

10 KHz

1 KHz

100 Hz

Noise Rate of 4 M5R4 chambers

12 CARDIACs @ th = 14fC

M5R4 & M3R3 & M5R2

OffSet

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Cross-Check using Cosmics• Cosmic Acquisition is being done at CERN on chambers tested in LNF

Low Eff channel

2 chambers without PLATEAUHV scan, gas, Operational Threshold & signal

coincidence between 2 Bigaps

15 M5R4 analysed up to now

100% of the defects found were successfully

detected by the Upgraded Test System

High Cdet signature

More Statistic (mainly with other chamber types) must be

collected

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Conclusions

• Automatic and fast (5-10 minutes) system has been implemented to be used also for non-experts

• System has shown to be very effective on 130 INFN chambers tested: fundamental guide to fix problematic chambers (10%)

• Cosmic Acquisition pointed an unexpected kind of problem in 0.5% of the channels. A retest using the Upgraded version of Test System has been able to discriminate all those channels

• Now we have 4 systems operating: CERN (2), LNF (1) and in the pit (1)

• We aim to minimize drastically the installation of chambers with problems