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Test of the GEM Front Tracker for the SBS Spectrometer at Jefferson Lab

Test of the GEM Front Tracker for the SBS Spectrometer at Jefferson Lab. F. Mammoliti, V. Bellini, M. Capogni, E. Cisbani, E. Jensen, P. Musico, F. Noto, G. Ruscica, M.C. Sutera, B. Wojtsekhowski. OUTLINE -JLab facility -Super BigBite Spectrometer -GEM Tracker -Mainz Test Beam Facility

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Test of the GEM Front Tracker for the SBS Spectrometer at Jefferson Lab

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  1. Test of the GEM Front Tracker for the SBS Spectrometer at Jefferson Lab F. Mammoliti, V. Bellini, M. Capogni, E. Cisbani, E. Jensen, P. Musico, F. Noto, G. Ruscica, M.C. Sutera, B. Wojtsekhowski

  2. OUTLINE -JLab facility -Super BigBite Spectrometer -GEM Tracker -Mainz Test Beam Facility -Experimental Data

  3. The Continuous Electron Beam Accelerator Facility The high resolution and high luminosity (polarized) CEBAF electron beam: -Current: up to 200 µA -Energy: up to 6 GeV -Energy resolution : 2.5*10-5 -Duty factor: 100% (continuous beam) -3 Experimental halls: A, B and C JLab, Newport News (VA)

  4. CEBAF UPGRADE • Two superconducting linear accelerators (LINACs) • Arches with Magnets that form a circuit of 1.4 Km • Electrons Energy of 10.9 GeV for Hall A, B, C and 12 GeV for new Hall D • Currents Sum: 5 μA for Hall D and 85 μA for the others Research fields • Searching for exotic Mesons • Proton and Neutron structure • Nucleus Structure • Parity Violation

  5. SUPER BIGBITE SPECTROMETER 1/3 Flexibility: use the same detectors in different experimental setup -High Luminosity: 8 x 1038 cm-2s-1 -Forward angle (down to 6°) -Large Momentum Range (2-10 GeV/c) -Moderate angular acceptance (64 mrad) -High rate capability (1 MHz/cm2)

  6. SUPER BIGBITE SPECTROMETER 2/3 Tracking Detector Configuration (X,Y) x2 (U,V) x2 (X,Y) x2 (U,V) x2 (X,Y) x2 (X,Y) x2 HCAL (U,V) x2 1st tracker 2nd tracker 3rd tracker

  7. SUPER BIGBITE SPECTROMETER 3/3 • Silicon tracker 10 x 20 cm2 • Dipole • Two GEM planes 40 x 150 cm2 • CH4 polarimeter • Second GEM tracker • Second CH4 polarimeter • Third GEM tracker • Calorimeter Why GEM detector? • Nominal spatial resolution of 60 μm • Readout flexibility • Low Cost • Resistant to shock • Rate > 5 ∙105 Hz/mm2

  8. GEM FOIL Gas Electron Multiplier GEM foil: 50 μm Kapton + few μm copper on both sides with 70 μm holes, 140 μm pitch • VGEM = 500 V → E ≈ 100 kV/cm • P = 140 μm • D = 70 μm • d = 50 μm Strong electrostatic field in the GEM holes

  9. Multi-GEM Detectors Single-GEM Triple-GEM • Cathode • Drift Region (3 mm) • GEM Foil • Induction Region (1 mm) • Anode (readout plane) • Maximum Gain 103 • Cathode • Drift Region (3 mm) • GEM Foil • Transfer Region (2 mm) • Induction Region (1 mm) • Anode (readout plane) • Maximum Gain 106

  10. GEM Prototype Assembling the GEM chambers parts requires a careful quality control at several check points and specific tools for gluing, heating, testing, cleaning GEM Prototype (10x10 cm2) built and tested at I.S.S. Roma

  11. Assembling the first 40x50 cm2 module Stretching Tendigem made in Catania Gluing the next frame with spacers 11

  12. FULLY equipped GEM module • 18 front-end cards • 2304 channels (front end cards on the othe side) • 7 independente HV levels 12

  13. Beam test @ MAINZ 1/2 Electron beam produced at MAMI (MAinz MIkrotron) at the Nuclear Physics Institute of Mainz MAMI is a continuous wave accelerator • Three GEM Chambers: 10x10 cm2 -Electron Beam energy 400 – 800 MeV -Strip distance 0.4 mm -Chamber distance 50 cm -Carbon Target -Lead glass and Plastic Scintillators

  14. Beam test @ MAINZ 2/2 -Different run performed: with beam without beam (pedestal) -Different angles between the electron beam and the plane of the GEM chambers -Different HV settings -Different Chamber positions By using APV 25 chips, it is possible to register different parts of the signal (every 25 ns), event by event.

  15. DATA ANALYSIS -More than 50 beam run analyzed -Study of the Pedestal -Study of the Signal -Study of the Clusters -Beam Profile reconsctruction -Tracking and Efficiency evaluation

  16. SIGNAL OBTAINED BY USING A 90Sr SOURCE FRONT CHAMBER MIDDLE CHAMBER

  17. PEDESTAL RUN STUDY ADC mean value obtained each 100 events in a single pedestal run: values change in different samples! IDEA: we decide to create a pedestal for each beam run by using the adc mean values of 200 events for all samples (1200 values).

  18. ADC(A.U.) SIGNAL New pedestal signal Beam run before the pedestal suppression 1 strip = 0,4 mm signal Beam run after pedestal suppression Strips

  19. SIGNAL IN DIFFERENT SAMPLES SAMPLE 2 SAMPLE 3 SAMPLE 1 SAMPLE 4 SAMPLE 5 SAMPLE 6

  20. SIGNAL SHAPE Signal shape: - τ1 and τ2 are the slope and falling time of the signal, respectively; - t0 is the stop time; - A is the Amplitude; Signal Amplitude for different strips. Peak around strip # 200 (ok!) and more or less 0 in all the others.

  21. STUDY OF THE CLUSTERS 1/2 A tree is filled, event by event, with different informations for each beam run: • Number of clusters; • Number of strips for each cluster; • Index of the first strip of each cluster; • ADC sum of each cluster; • Centroid of each cluster; RUN #446 – 300 EVENTS – SAMPLE 2: from 0.25 to 0.50 ns CLUSTERS NUMBER STRIPS NUMBER OF EACH CLUSTER

  22. STUDY OF THE CLUSTERS 2/2 Centroids plot Adc sums of single cluster vs strip VERY LOW PILE-UP!

  23. Examples of CENTROID EVALUATION for 2 RUN with different Energy 400 MeV ABOUT 4-6 mm 800 MeV Beam Profile

  24. TRACKING AND EFFICIENCY1/2 X Z -POSSIBLE EVENT IF THERE IS A CLUSTER IN ALL CHAMBERS -HIT POSITION WITH σ FOR EACH CHAMBER -WE CONSIDER X = a*Z + b with a and b obtained by linear fit -BY USING P0 (x0, y0) and P1 (x1,y1) WE OBTAIN a AND b -WE CONSIDER P3 (x3,y3) and if lx3 -az3 –bl<σ3 THAN THE SIGNAL OF THE 3 CHAMBERS BELONGS TO THE SAME PARTICLE OTHERWISE IT IS REJECTED

  25. TRACKING AND EFFICIENCY 2/2 NUMBER OF EVENTS IN TRAJECTORY EFFICIENCY= NUMBER OF EVENTS (TRIGGER) RESULTS FOR A RUN WITH HV = 3950 V

  26. CONCLUSIONS: -GEM Tracker operated stably during the test at Mainz -Study of pedestal and signal -Study of clusters -Beam Profile was reconsctructed -Preliminary Efficiency was evaluated -GEM Tracker is a complex detector and improvement is still in progress

  27. THANKS FOR YOUR ATTENTION

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