1 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

2 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

3 Goal Friendly and automatic procedure for diagnose of errors of the Chamber + Electronics system Check of our 1368 MWPC (~ 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

4 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/CO 2 /CF 4 (40:55:5)  wire spacing: 2 mm, mechanical tension: 65 gr  HV = KV  gas gain: G ≈  gain uniformity: ≤ 30% MWPC Sandwich M5R3 full equipped M3R3 panel 6 FEEs Single pad Faraday cage

5 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 unit Chamber: 2 bigaps LVDS READOUT Ch(AB) OR SPB CONTROL Ch A CONTROL Ch B Single pad logic Spark protection board 2 CARIOCAs + DIALOG = FEE (CARDIAC)

6  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 fC Cathode Q > 8 fC Qth µ signal time dead region noise Min Det charge AFTER TEST FEE DATABASE Capacitance (pF)

7  The Discriminator Differential Threshold Voltage oLess sensitive to Noise oVth Nominal: 0 to 1.3 V oVth Effective Abs(V refA – V refB ) V refA & V refB obtained from Vth Nominal oOffSet (Vth Min Vth Effective) 740 to 860mV FEE characteristic II offset V th Nominal V refA V refB Vth Eff V th Nominal Noise Rate Analysis of Noise X Threshold Rate method

8 Test Setup Control FEE via I 2 C (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 8X 16X

9 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) Preparatio n 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 3 specific thresholds Read Chamber barcode In test area (2) Test Procedure

10 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 Checking Check if cables are swapped It can be useful to check cables in pit Pulse Injection Test

11 Check the Position of FEE comparison of OFFSET values obtained here to the ones found on FEE database Check dead FEE channels by the simple existence of Noise (min 3 pts) Second Step Threshold Scan Test Check Chamber-FEE association Search for Dead Channels

12 Estimate Cdet (Rate Method) Search for Short-Circuit Search for Open Channels Third Step: Cdet The detector capacitance determines the noise level since it acts as a series noise source SPB 2 nF bigap Threshold Scan Test Rate= Nexp 2 ENV 2 -V th 2 offset Min Det signal Offset & Min detect signal ENV 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

13  Third Step: Cdet Criteria  channels Cdet  + -   > 2.5    > 3  or ERROR Mostly associated to setup itself Very important Alarms ! Cdet > 300 pF or Cdet < 20 pF

14 Criteria for Noise Rate at 3 specific Thresholds OK / WARNING / ERROR if Rate > 1 KHz Cathode Readout: fC Anode Readout: fC Check Level 3 specific thresholds Fourth Step Electronic Noise can be ~100 Hz / channel 1 KHz in Noisy channels is acceptable Chamber Eff Th = 8 fC (cathode) & 14 fC (anode) threshold

15 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 OK Warning ERROR 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

16 Results: First Chambers 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) M5R4 Cdet (sim) = 220 pF 22 - M3R3 Cdet (sim) = 140 pF 06 - M5R2 Cdet (sim) = 120 pF chambers

17 More Plots: th = 10 fC & 6 fC th = 12 fC & 7 fC th = 14 fC & 8 fC 10 KHz 1 KHz 100 Hz Noise Rate of 4 M5R4 chambers 12 th = 14fC M5R4 & M3R3 & M5R2 OffSet

18 Cross-Check using Cosmics Cosmic Acquisition is being done at CERN on chambers tested in LNF Low Eff channel 2 chambers without PLATEAU HV 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

19 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