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Instrumentation of the Very Forward Region of a Linear Collider Detector

This paper discusses the instrumentation and functions of the very forward region of a linear collider detector, including measurement of luminosity, detection of electrons and photons at low angles, fast beam diagnostics, and inner detector shielding. It also addresses the requirements on mechanical design, alignment, and precision, as well as performance simulations and beam parameter determination.

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Instrumentation of the Very Forward Region of a Linear Collider Detector

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  1. Instrumentation of the Very Forward Region of a Linear Collider Detector Univ. of Colorado, Boulder, AGH Univ., INP & Jagiell. Univ. Cracow, JINR, Dubna, NCPHEP, Minsk, FZU, Prague, IHEP, Protvino, TAU, Tel Aviv, DESY, Zeuthen Wolfgang Lohmann DESY PRC

  2. The Very Forward Calorimetry Collaboration see: PRC R&D 01/02(2002)

  3. Functions of the very Forward Detectors • Measurement of the Luminosity with precision O(10-4) • Detection of Electrons and Photons at very low angle – extend hermiticity (Important for Searches) • Fast Beam Diagnostics • Shielding of the inner Detector L* = 4m 300 cm VTX FTD IP LumiCal: 26 < q < 82 mrad BeamCal: 4 < q < 28 mrad PhotoCal: 100 < q < 400 mrad LumiCal BeamCal

  4. Measurement of the Luminosity Two Fermion Cross Sections at High Energy, Physics Case: Giga-Z , e+e- W+W- Gauge Process: e+e- e+e- (g) Goal: 10-4 Precision • Technology: Si-W Sandwich Calorimeter Optimisation of Shape and Segmentation, Key Requirements on the Design • MC Simulations • Close contacts to Theorists (Cracow, Katowice, DESY)

  5. Requirements on the Mechanical Design LumiCal IP LumiCal < 4 μm Requirements on Alignment and mechanical Precision (rough Estimate) Inner Radius of Cal.: < 1-4 μm Distance between Cals.: < 60 μm Radial beam position: < 0.7 mm < 0.7 mm

  6. Concept for the Mechanical Frame Decouple sensor frame from absorber frame Sensor carriers Absorber carriers

  7. Laser Alignment Test • Simple CCD camera, • He-Ne red laser, • Laser translated in 50 mm steps Jagiellonian Univ. Cracow Photonics Group reconstruction of the laser spot (x,y) position on CCD camera

  8. Performance Simulations for e+e- e+e-(g) 0.13e-3 rad 0.11e-3 rad 30 layers 15 rings Constant value Constant value Simulation: Bhwide(Bhabha)+CIRCE(Beamstrahlung)+beamspread Event selection: acceptance, energy balance, azimuthal and angular symmetry. 4 layers 11 layers 15 layers 10 rings 10 rings 20 rings

  9. Determination of shower Coordinates Strip version ΔE~0.31√E

  10. Determination of the Acceptance region Eout-Ein P = Eout+Ein Out In P 1 ring 2 rings 3 rings

  11. Fast Beam Diagnostics e+ e- • e+e-Pairs from Beamstrahlung are deflected into the BeamCal • 15000 e+e- per BX 10 – 20 TeV Rad. hard sensors • 10 MGy per year • direct Photons for q < 200 mrad GeV Technologies: Diamond-W Sandwich Scintillator Crystals Gas Ionisation Chamber

  12. Schematic Views Heavy crystals W-Diamond sandwich sensor Space for electronics

  13. Beam Parameter Determination with BeamCal Observables detector: realistic segmentation, ideal resolution single parameter analysis, bunch by bunch resolution first radial moment thrust value total energy angular spread L/R, U/D F/B asymmetries

  14. and with PhotoCal IP >100m Photons from Beamstrahlung Heavy gas ionisation Calorimeter nominal setting (550 nm x 5 nm) L/R, U/D F/B asymmetries of energy in the angular tails

  15. Detection of High Energy Electrons and Photons √s = 500 GeV Single Electrons of 50, 100 and 250 GeV Comparison Sampling Heavy Crystal Comparison 500 GeV - 1TeV

  16. Realistic beam simulation Efficiency to identify energetic electrons and photons (E > 200 GeV) √s = 500 GeV Includes seismic motions, Delay of Beam Feedback System, Lumi Optimisation etc. (G. White) Fake rate

  17. Sensor prototyping, Crystals Light Yield from direct coupling Compared with GEANT4 Simulation, good agreement and using a fibre ~ 15 % Similar results for lead glass Crystals (Cerenkov light !)

  18. Sensor prototyping, Diamonds Scint.+PMT& Diamond (+ PA) gate signal ADC Pads Pm1&2 May,August/2004 test beams CERN PS Hadron beam – 3,5 GeV 2 operation modes: Slow extraction ~105-106 / s fast extraction ~105-107 / ~10ns (Wide range intensities) Diamond samples (CVD): - Freiburg - GPI (Moscow) - Element6

  19. Diamond Sensor Performance Linearity Studies with High Intensities Response to mip Pm-Pm Pm-Pads Pm-Pad2 Pm-Pad1 Pm-Pad3 Pm-Pad4

  20. Application as beam halo monitor PITZ Facility at Zeuthen Position of the Diamond Laser Reference Pulse Diamond Response (on top of dark current)

  21. Summary • We learned a lot …… • We are motivated to continue • LumiCal: More detailed Monte Carlo Studies on the bias in q, Acceptance boundaries, two photon background; Mechanics Support, Laser Alignment, Sensors Prototype in 3 years. • BeamCal: MC to reduce segmentation, not performance, beam diagnostics; Feasibility Study for Large Area Diamond Sensors (Coll. with IAF) Preparation of a Prototype • PhotoCal: We are just at the beginning….

  22. Energy and polar angle resolution, pad version

  23. Shower LEAKAGE in old (TDR) and new LumiCal design Shower in LumiCal (new design) Shower in LAT (TDR design)

  24. Diamond performance as function of the absorbed dose Linearity of a heavy gas calorimeter (IHEP testbeam)

  25. Pile up effects 200 GeV Electrons Efficiency less then 90%

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