1. Analyzing Praxial Platform Positions on MDT Barrel Chambers Using X-Ray Tomograph Measurements Chris Hayward Advisor: Silvia Schuh August 14, 2003 UM CERN 2003 Summer REU

2. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU Outline ATLAS Muon Spectrometer MDT Chambers RASNIK system X-Ray Tomograph My Project ROOT Current Status/Results Acknowledgements

3. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU ATLAS – A Toroidal LHC Apparatus

4. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU Muon Spectrometer Outer layer of ATLAS. Uses magnetic field to deflect muons and measure their momentum. High momentum resolution (order 10% for p t ~1 TeV) necessary to detect SUSY, Higgs, and other physics. MDT wire positions must be know with high precision.

5. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU Monitored Drift Tube (MDT) Chambers MDTs: Al tubes, W wires. Filled with Ar/CO 2. ~2000 V applied. Detect charged particles. Used to reconstruct muon tracks. Chambers: 2 multi-layers with 3 or 4 monolayers glued on either side of support structure (spacer frame). Barrel and endcap types. Largest barrel chamber, NIKHEF 5 m 2.2 m

6. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU RASNIK System “Monitored”: RASNIK system provides dynamic alignment information; goal: ~30 microns. RASNIK: LED & CCD system used to monitor deformations. Inplane (mounted on spacer frame): deformations due to magnetic field, varying chamber sags, temperature, etc. Station-to-station (praxial, projective): RASNIK system mounted on platforms glued to chambers; platform position relative to wire grid must be well-known.

7. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU X-Ray Tomograph Central quality control of MDT chamber mechanical construction. MDT wire placement precision goal: RMS < 20 micrometers for whole chamber. Samples 15% of MDTs from 13 sites around the world. X-ray beams X-ray sources Calibrated rulers Scintillators 2.2 m 0.6 m

8. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU Measurement Principle Small barrel chamber Long beams Support frame 10000 Full Scan 20000 X-ray carrier position (mm) 100002900 Scintillator counts/20  m Tube walls X-ray carrier position (mm) 162 0 Scintillator counts/20  m One corridor W absorbs more x-rays than Al. Yields a shadowgram from which wire positions can be extracted. Calibration rulers provide vertical scale & orthogonality information. Peak position  = 1.7  m

9. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU Measurement Results

10. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU My Project Praxial platform positions relative to wire grid are measured by xtomo. These measurements must be analyzed for systematic errors (due to construction and/or measurement process). I wrote a program using ROOT that reads in barrel chamber data, stores the data in a TTree, and plots default histograms which we developed.

11. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU Program Components 1. Search data directories for barrel chambers scanned since last run. 2. Read in data from new chambers and store in a ROOT TTree. 3. Calculate mean parameters per tool/platform and side. 4. Plot a set of standard histograms and allow the user to plot others. 5. Store data in a ROOT TFile which can be easily accessed and analyzed through the ROOT interactive interface.

12. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU ROOT TTrees are ROOT TObjects that are used to store many different kinds of data. I created a class “Chamber”. Each TBranch of my TTree stores one Chamber object. Useful to inherit from TObject because it enables use of ROOT’s powerful I/O. TTrees also offer very effective compression and organization; members of a class can be read without reading the whole object.

13. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU A Chamber Branch

14. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU Current Status/Results The program is ready to do analysis, but we must update old HTML data files before we can analyze all the chambers we plan to. I am staying an extra week to go a bit further in the analysis. Our goal is to analyze ~50 chambers (over half of those measured).

15. C. Hayward 7/30/2003 UM-CERN 2003 Summer REU Acknowledgements Silvia Schuh Professor Jean Krisch, Professor Tom Dershem, Professor Steve Goldfarb, and Professor Homer Neal CERN The ROOT Team ROOTTalk subscribers University of Michigan CERN REU program UM Physics Department Michigan Center for Theoretical Physics UM Global Intercultural Experience for Undergraduates Ford Motor Co.