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MICROMEGAS per l’upgrade delle Muon Chambers di ATLAS per SLHC

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Presentation on theme: "MICROMEGAS per l’upgrade delle Muon Chambers di ATLAS per SLHC"— Presentation transcript:

1 MICROMEGAS per l’upgrade delle Muon Chambers di ATLAS per SLHC
Arizona, Athens (U, NTU, Demokritos), Brookhaven, CERN, Harvard, Istanbul (Bogaziçi, Doğuş), Naples, Seattle, USTC Hefei, South Carolina, St. Petersburg, Shandong, Thessaloniki M.Alviggi, GR1-Napoli, 16 dicembre 2008 Thanks to P.Iengo per la maggior parte dei plot


3 Micromegas as candidate technology
Combine triggering and tracking functions Matches required performances: Spatial resolution ~ 100 m (track< 45°) Good double track resolution Time resolution ~ few ns Efficiency > 98% Rate capability > 5 kHz/cm2 Potential for going to large areas ~1m x 2m with industrial processes

4 Prototype P1 Standard bulk micromegas fabricated at CERN-TS/DEM
Homogeneous stainless steel mesh 325 line/inch = 78 m pitch Wire diameter ~25 m Amplification gap = 128 m 450mm x 350mm active area Different strip patterns (250, 500, 1000, 2000 µm pitch; 450mm and 225 mm long) Drift gap: 2-5 mm

5 Test beam set up 2007 Test beam set up 2008 Test beam set up P1 CERN H6 beam line in November 2007 & June to August 2008 120 GeV pion beam Scintillator trigger External tracking with three Si detector modules (Bonn Univ.); independent DAQ Three non-flammable gas mixtures with small isobutane admixture used in 2008: Ar:CO2:iC4H10 (88:10:2), Ar:CF4:iC4H10 (88:10:2), Ar:CF4:iC4H10(95:3:2) Data acquired for 4 different strip patterns and 5 impact angles (0 to 40 degrees)

6 Readout DAQ based on ALTRO CHIP FEC DAQ PC (ALICE DATE) 32 channels
trigger DAQ PC (ALICE DATE) FEC 32 channels 200 ns integration time 64 charge samples/ch 100 ns/sample 15 pre-samples 1 ADC count ~ 1000 e- 32 channels Micro Megas Two inverted diodes for spark protection Zero channels died Typical ADC spectra Noise subtraction (from 12 pre-samples) Cluster position from center of gravity 6

7 Cluster charge distribution
Gas mixture: Ar:CF4:iC4H10 (88:10:2) Drift gap 5 mm; drift field = 200 V/cm Strip pitch = 250 µm Horizontal axes: ADC count ADC count = 1000 electrons Gain measurement from HVmesh scan Exponential gain increase Stable operation (small spark rate) for gain of 3–5 · 103 Cluster charge (ADC counts) HVmesh = 460 V


9 Spatial resolution Si tracker σextr≈ 50 µm MM cluster position
Convoluted Strip pitch: 250 µm Gas: Ar:CF4:iC4H10 (88:10:2) Track impact angle: 90° Convoluted resolution of Si tracker + extrapolation σ(Si+MM) = 63 µm MM intrinsic resolution σ(MM) ≤ 40 µm

10 Spatial resolution … more
‘x-raying’ the micromegas Look for areas where micromegas is inefficient, i.e. tracks in Si tracker with no hits in the micromegas  pattern of pillars Si tracks Equipped micromegas area (8 mm) 2.54 mm Pillar distance

11 Micromegas as a TPC…. Track inclination: 40° Ar:CF4:iC4H10 (95:3:2)
Drift field: 360V/cm Cluster First strip Last strip Even with non-optimal r/o electr. measuring the arrival time on each strip it is possible to measure the drift velocity or, with known drift velocity, the drift distance Rob Veenhof vd = 8.4 cm/us Drift path (mm) 8 cm/µm Drift time (ns)

12 …Micromegas as a TPC A time resolution of a nanosecond results in space points with a resolution along the drift direction of 100 µm Each micromegas gap delivers a set of space points, the more the track is inclined the more space points are available Solves the problem of spatial resolution for large track inclination

13 Therefore… Robust detector Works with non-flammable gases
Spatial resolution is excellent with small strip pitch MM as TPC will give track segments & excellent space resolution; needs time measurement (ns) Electronics should measure time, may relax on charge Trigger capability to be proven with faster electronics

14 What next ? Test beam stopped ; setting up cosmics test stand in and in few other labs (Naples,Demokritos)  optimize gas mixtures wrt drift velocity, diffusion, primary ionization, sparks, ageing… Analysis of test beam data taken in 2008 with goals: Definition of readout segmentation Definition of requirements for r/o electronics Construction and test of 1300 x 400 mm2 prototype (Rui de Oliveira)

15 The 50% prototype Active area: 1.3 x 0.4
Segmented mesh (cut) to reduce mesh capacity 250 and 400 µm strip pitches Long and short strips Construction has started in CERN/TS-DEM Expect MM board to be ready by early 2009 Chamber to be completed spring 2009 Test beam in May 2009 The stretched micromegas mesh on its frame

16 Backup Richieste CSN1 RD51

17 σ = 30 ns σm ≈ 1.2 ns ns*100

18 Inclined tracks Cluster First strip Last strip Impact angle: 50°

19 Micromegas as TPC (II) Track under 50° with relative time info

20 Software tool Software tool* for quasi online and off-line reconstruction (based on ROOT) Permits alignment of Si tracker modules with MM chamber Combines data from Si tracker and MM ‘online’ resolution Also: simple event display *) Thanks to Woo Chun Park (U. South Carolina)

21 Simple event display Si module1 Si module3 Si module6 Micromegas

22 Spatial resolution – ‘online’
Si tracker Micromegas Beam Residuals of MM cluster position and extrapolated track from Si Convolution of: Intrinsic MM resolution Tracker resolution (extrapolation) Multiple scattering ⎬ ~60 µm Gas: Ar:CF4:iC4H10 (88:10:2) Drift field: 200 V/cm Strip pitch: 500 um Strip width: 400 um Strip pitch: 1000 um Strip width: 900 um Strip pitch: 250 um Strip width: 150 um : 85 um MM: 60 um : 102 um MM: 82 um : 212 um MM: 203 um mm mm mm

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