Precision Muon Tracking Detectors and Read-out Electronics for Operation at Very High Background Rates at Future Colliders S. Nowak O. Kortner H. Kroha R. Richter K. Schmidt-Sommerfeld Ph. Schwegler Max-Planck-Institut f¨ ur Physik, Munich Motivation Dr. Hubert Kroha - The muon spectrometers of experiments at HL-LHC at a Future Circular Hadron Collider (FCC-hh) require efficient muon tracking with very high Max-Planck-Institut f¨ ur Physik F¨ spatial resolution (30-40 µ m) at high background rates. ohringer Ring 6 80805 Munich - ATLAS Monitored Drift Tube (MDT) chambers have proven high reliability and high-precision tracking up to neutron and γ fluxes of 500 Hz Germany cm 2 . kroha@mpp.mpg.de - Background rates at HL-LHC are x 10 and at FCC x 40 than at LHC - sMDT chambers are very well suited large area muon tracking at FCC experiments. Limitation of sMDT performance due to signal pile-up with - Like the ATLAS MDT chambers for HL-LHC, sMDT chambers can also be bipolar shaping of the read-out electronics used for high selective Level-1 muon triggers at FCC. sMDT chambers - Bipolar shaping used to guarantee baseline stability at high rates - Disadvantage: overlap of signals with the bipolar undershoot of MDT chambers: preceding background pulses lead to deterioration of the efficiency and Drift tube detectors with 30 mm tube spatial resolution of muon pulses diameter for precision tracking in the Current γ -background ATLAS Muon Spectrometer Muon sMDT chambers: Threshold � 30 mm MDT � 15 mm sMDT New drift tube detectors with 15 mm Baseline tube diameter ∆ sMDT tube properties: t ⇒ Operated with Ar:CO 2 (93:7) at Time 0.25 Spatial resolution [mm] a gas gain of 20000 2 818 Hz/cm 2 523 Hz/cm ⇒ 185 ns maximum drift time 0.2 gain drop 2 259 Hz/cm Improvement: Bipolar shaping with baseline restoration 2 ⇒ 8 times lower occupancy 155 Hz/cm space charge fluct. No irradation 0.15 compared to MDT chambers Principle of baseline restorer (working point I Base ) ⇒ Space charge effects strongly 0.1 - Diode is non-conducting for positive signal suppressed, gain loss ∼ R 3 polarity ⇒ signal stays unchanged 0.05 ⇒ An order of magnitude higher rate capability than MDT - Diode is conducting for negative polarity 0 0 2 4 6 8 10 12 14 chambers with existing MDT (undershoot) ⇒ input current drained to ground Drift radius [mm] 15 mm ⌀ tube read-out electronics ⇒ Undershoot eliminated
Precision Muon Tracking Detectors and Read-out Electronics for Operation at Very High Background Rates at Future Colliders S. Nowak O. Kortner H. Kroha R. Richter K. Schmidt-Sommerfeld Ph. Schwegler Max-Planck-Institut f¨ ur Physik, Munich Bipolar shaping circuit with baseline restoration sMDT single-tube resolution under γ irradiation (GIF/CERN) Filter 2 BLR Comparator Filter 1 PreAmp Spatial resolution [mm] 0.2 LVDS out 0.18 MDT sMDT 0.16 0.14 sMDT 0.12 sMDT with BLR 0.1 0.08 MDT 0.06 Expectation from MDT - High bandwidth (700 MHz) transimpedance amplifier (PreAmp) 0.04 sMDT without BLR - Bipolar shaping circuit (2 filter stages) with baseline restoration and 0.02 sMDT with BLR 0 comparator with LVDS output to TDC (as MDT read-out chip) 0 5 10 15 20 2 Photon hit flux [kHz/cm ] - sMDT resolution limited at high counting rates by signal pile-up effects of Bipolar shaped pulses with baseline restoration the electronics, in contrast to MDTs where space charge effects dominate - Suppression of signal pile-up effects with baseline restoration 1 1 Signal [V] Signal [V] Muon response without BLR Muon response with BLR sMDT single-tube muon efficiency Shaped signal Shaped signal 0.5 0.5 Unshaped signal (10x) Unshaped signal (10x) 1 ) efficiency 0 0 0.9 sMDT + BLR + 0.8 σ short dead time Drift tube muon (3 0 200 400 600 800 0 200 400 600 800 Time [ns] Time [ns] 0.7 sMDT + BLR 0.6 sMDT Signal [V] Signal [V] Gamma response without BLR Gamma response with BLR 1.5 1.5 0.5 0.4 1 1 Shaped signal Shaped signal MDT s MDT, 820 ns dead time, no BLR Unshaped signal (10x) Unshaped signal (10x) 0.3 0.5 0.5 sMDT, 220 ns dead time, no BLR 0.2 sMDT, 220 ns dead time, with BLR 0 0 0.1 sMDT, 0 50 ns dead time, with BLR -0.5 -0.5 0 0 500 1000 1500 2000 0 200 400 600 800 0 200 400 600 800 Photon hit rate [kHz/tube] Time [ns] Time [ns] - At high counting rates limited by read-out electronics - γ -pulses push shaper in saturation (larger signals with longer undershoot - Use of minimum electronics dead time possible for sMDTs compared to muon pulses) - Suppression of signal pile-up effects at short dead times with baseline - Clear undershoot suppression with baseline restoration restoration
Precision Muon Tracking Detectors and Read-out Electronics for Operation at Very High Background Rates at Future Colliders S. Nowak O. Kortner H. Kroha R. Richter K. Schmidt-Sommerfeld Ph. Schwegler Max-Planck-Institut f¨ ur Physik, Munich MDT and sMDT occupancies at HL-LHC and maximum sMDT design and construction FCC-hh luminosity - sMDT chamber design and assembly procedures optimized for mass production Occupancies of MDT and sMDT tubes at maximum FCC luminosity in the - Simple and cheap drift tube design with high reliability ATLAS geometry (ATLAS operating parameters and tube lengths) - Special plastic materials selected to prevent outgassing and cracking - Industrial standard Al tubes - Wire positioning accuracy better than 10 µ m - No wire aging observed up to 9 C cm charge on wire (15 x ATLAS requirement) Internal wire locator External reference surface Grounding End-plug insulator pin base (Crastin) Contact disc Grounding Gas inlet pin Background rates in muon system Aluminum tube ⌀ 15×0.4 ATLAS at LHC design luminosity → x 10 at HL-LHC → x 4 at FCC-hh Insulator (MDT: max. 500 Hz cm 2 , max. 30% occupancy) T wister Plastic stopper (Pocan) Signal cap O-ring ⌀ 10×2.0 - Maximum sMDT occupancy at FCC is half of the MDT occupancy at (brass) Aluminum ring Brass insert HL-LHC with precision surface - FCC detectors not limited to ATLAS operating parameters and Crimp tubelet Plastic gas geometry O-ring (copper) connector ⇒ Further optimisation of tube parameters and read-out electronics ⌀ 4×1.5 (Pocan)
Precision Muon Tracking Detectors and Read-out Electronics for Operation at Very High Background Rates at Future Colliders S. Nowak O. Kortner H. Kroha R. Richter K. Schmidt-Sommerfeld Ph. Schwegler Max-Planck-Institut f¨ ur Physik, Munich Tube positioning using precisely machined jigs sMDT Chamber Construction 3D coordinate measurement Residual distribution of horizontal and vertical coordinates ( σ < 10 µ m ) - Wire positioning accuracy is reached due to tube external reference surface and high precisely machined jigs. - Wire positioning accuracy better than 10 µ m (most precise chambers so far) - Chamber assembly is conducted within one working day Summary Construction of a sMDT chamber already - sMDT chambers are a well suited for high-accuracy large area muon installed in ATLAS tracking at high background levels as required for max. luminosity at the FCC. - Semi-automated drift-tube production and chamber assembly take - The high reliability of the MDT and sMDT chambers has been proven in place in a air-conditioned clean room ATLAS. - An order of magnitude smaller occupancies of sMDT compared to MDT - Automated testing of tube leakage rate, leakage current and wire chambers. tension - Space charge effects are strongly suppressed for sMDT tubes. - 2 sMDT chambers already installed in the ATLAS detector - Performance of sMDT tubes can be further increased by optimised read-out - Additional 12 (16) sMDT chambers under construction until 2016 (2018) electronics.
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