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Studies of Sense Wire Displacements in MDT’s

Studies of Sense Wire Displacements in MDT’s. Monday July 26 th , 2004 CERN, Switzerland Mentor: Dr. Daniel Levin. Divine Kumah. Outline. Project Overview Scope of my project Results and Discussions Conclusion Questions. Atlas Setup (A Toroidal LHC Aparatus). MDT Chamber Setup.

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Studies of Sense Wire Displacements in MDT’s

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  1. Studies of Sense Wire Displacements in MDT’s Monday July 26th, 2004 CERN, Switzerland Mentor: Dr. Daniel Levin Divine Kumah

  2. Outline • Project Overview • Scope of my project • Results and Discussions • Conclusion • Questions

  3. Atlas Setup(A Toroidal LHC Aparatus)

  4. MDT Chamber Setup • Each MDT consists of 2 multilayers separated by a crossframe. • Each multilayer has 3 or 4 layers of cylindrical gas filled aluminum tubes • Tube diameter 30mm • Gas Mixture • Ar (93%), CO2 (7%) • Tungsten sense wire (anode)

  5. Drift Tube Operation Measured relation between drift distance and drift time for the ATLAS operating point. 4GeV Muon track produced from Garfield Simulation

  6. MDT Operational Parameters

  7. Motivation for Study • Sense wire is displaced due to • Gravity • Electrostatic Forces • Wire Displacement affects overall resolution of the detector Aims for Study • Calculate the wire sag due to these forces • Investigate the effect of sag on Drift Spectra by • Analyzing Cosmic Ray Experiment Data • Simulations in GARFIELD

  8. Gravitational Sag For Horizontal Tubes • Chambers mounted in different orientations • Sagging is minimal for vertically placed tubes Maximum Gravitational Sag for MDT tubes up to 6m Side View of the ATLAS Detector showing several orientations of the Barrel MDT chambers

  9. Electrostatic Amplification • Electrostatic forces amplify Gravitational sag • Resultant sag from Fgravityand Felec • where

  10. Experimental Setup • Two 30 x 30 cm Hodoscopes • 4 GeV Cosmic Ray muons, 3 hits/minute • Pressure – 3 bar • Temperature – 293 K • Hodoscope Positions • HV end • 1.5 m from HV end • Tube Center

  11. Garfield Simulations • Same gas mixture, temperature conditions as actual experiment. • Wire sag calculated for the different hodoscope positions • Same angular cosmic ray distribution as actual experiment www.garfield.com

  12. Drift Time Spectra Fit The rise is fitted with the Sigmoid function T0 T0 where B = t ie. Halfway up the rise The falling edge is fitted with the function Tend Tend where B = t ie. Halfway up the fall Maximum Drift TimeTmax = Tend – T0

  13. Results for 1500 psi Gas Flow

  14. Results for 2500 psi Gas Flow • Garfield Simulation • Maximum Drift Time for no-sag is 671 ns! • Ashley has simulations in progress for displaced wire positions. www.garfield.com

  15. Observations • Increased Max Drift Time ~ 50 ns • Why?Increase in maximum drift path Non-displaced wire Displaced wire • 2 Step tail • Why?Wire Displacement

  16. Conclusion • Calculated Wire Sags in MDT’s shows gravitational wire sags ~500 mm • Analysis of Cosmic Ray Experimentshows increase in Drift times ~50 ns due to wire sag • Comparison of Real Data with Garfield simulations shows strong agreement. Garfield is a reliable tool for further studies of wire sag effects

  17. Acknowledgements • Dan Levin, Ed Diehl, Ashley Thrall • Jean Krisch, Homer Neal, Jeremy Birnholtz • The University of Michigan CERN-REU Program, FORD, NSF, CERN • The UM-REU students, 2004 CERN Summies

  18. QUESTIONS??

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