Experience from ZEUS Microvertex detector is running for more than five years without access! E.N Koffeman NIKHEF & University of Amsterdam

HERA II Expected increase of luminosity with 5x Polarised electron beam 2001-2003 serious background problems Recovery in 2004 but end of HERA (June 2007) nearby Els Koffeman - VERTEX'06

ZEUS ZEUS tracking upgrade to improve b,c tagging in DIS Vertex detector: MVD electron quark pair proton Els Koffeman - VERTEX'06

MVD history 1997 proposal 1998 design 1999 testbeam 2000 cosmic test 2001 installed 2002 cosmics 2003 ep collisions 2007 HERA shutdown Els Koffeman - VERTEX'06

LAYOUT 30 ladders with a double, perpendicular layer of strips sensors: true 3D space points. All ladders are identical. Note elliptical beampipe and the off-center beamline ! (minimise the effects of synchrotron radiation) Els Koffeman - VERTEX'06

Micro Vertex Detector Els Koffeman - VERTEX'06

1 mm 0.1 mm 8 micron oxide 12 micron p + probe pad polysilicon resistors guard rings strip number survey mark detail strip 0.1 mm Els Koffeman - VERTEX'06

TESTBEAM Detector + hybrid tested in 6 GeV electron beam Point resolution 7 micron for single sensor. 12 micron for module Charge sharing works well Els Koffeman - VERTEX'06

Radiation damage Helix-128.3 chip tested to 5 kGy Sensors Monitoring Tested 3 kGy 10 13 (1 MeV N eq/cm2) Monitoring Pin diodes Radfet TLD Els Koffeman - VERTEX'06

ZEUS material Study (hadronic) interactions in data and Monte Carlo Good agreement with MC (improved in 2006) MC data 3%Xo in a ladder Els Koffeman - VERTEX'06

Performance Helix 3.0 Chip- 8 chips per module 200 kchannels 2003-2006 Els Koffeman - VERTEX'06

Bad channels 1 module = 1k channels, 150+56 modules (barrel + wheels) Bad channels increase from 4% in 2001 to 8% in 2006 Els Koffeman - VERTEX'06

Alignment with cosmics r-z r-Φ Cosmic alignment already available in 2003/2004 Includes both errors from hit reconstruction and track parameters. Els Koffeman - VERTEX'06

Alignment revisted Cosmic alignment worked well, used in early data Limited accurracy for not-horizontal ladders ep- data alignment only completed recently All ladders now aligned with same accuray No difference in sensor-to-ladder positions Ladders positions stable Possible overall movement ? 25 micron residuals Els Koffeman - VERTEX'06

Impact parameter All track residuals around 25 micron Impact parameter resolution 100 micron (long extrapolation length and non-negligible amount of material) Els Koffeman - VERTEX'06

D+ in DIS DIS event from 12-Mar-2005 + K 500 m D+ vertex Primary vertex D+ vertex + K Els Koffeman - VERTEX'06

One more….. 500 m   K+ Els Koffeman - VERTEX'06

Preliminary Els Koffeman - VERTEX'06

Summary Zeus vertex detector runs reliably and stable Pattern recognition, alignment, track fitting worked well within a year but, after five years still significant improvements material description alignment real tracks finetune trackfit optimise reconstruction This shows You need for a stable detector system You must try to keep the experts around You need real physics data to get the ultimate performance out Els Koffeman - VERTEX'06

Micro Patterned Gaseous Detectors GEM High field created by Gas Gain Grids Most popular: GEM & Micromegas Micromegas improved granularity : wire chambers react on COG of many electron clouds/clusters Els Koffeman - VERTEX'06

Gridpix GridPix: the electronic bubble chamber 14 mm Modified MediPix He/Isobutane 80/20 14 mm Modified MediPix Efficiency for detecting single electrons: ~ 95 % δ-ray! Els Koffeman - VERTEX'06

GridPix MediPix2 & Micromegas: apply the ‘naked’ MediPix2 chip without X-ray convertor! 55Fe Cathode (drift) plane Drift space: 15 mm Micromegas Baseplate MediPix2 pixel sensor Brass spacer block Printed circuit board Aluminum base plate Very strong E-field above (CMOS) MediPix! Els Koffeman - VERTEX'06

Energy resolution in Argon IsoC4H10 80/20 Observation of two lines: Kα @ 5.9 keV Kβ @ 6.4 keV FWHM of the Kα distribution 16.7 % Gain fluctuations < 5% Very good energy resolution: Very precise dimensions d < 0.1 μm Els Koffeman - VERTEX'06

‘wafer post processing’ INGRID Integrate GEM/Micromegas and pixel sensor ‘GEM’ ‘Micromegas’ ‘wafer post processing’ by Univ. of Twente/MESA+ Els Koffeman - VERTEX'06

Gossip MIP InGrid Cathode foil CMOS chip ‘slimmed’ to 30 μm Drift gap: 1 mm Max drift time: 16 ns GOSSIP: Gas On Slimmed SIlicon Pixels new vertex detector! Els Koffeman - VERTEX'06

Advantages of Gossip Generate charge signal in gas instead of Si (e-/ions versus e-/holes) Amplify # electrons in gas (electron avalanche versus FET preamps) Potentially radhard Low power dissipation of preamps No detector bias or leakage Ultralight structure (CMOS wafer can be thinned ; no bumping!) Els Koffeman - VERTEX'06

ATLAS B-layer ? Radiation tests (so far good) Spark protection (two concepts being tested) Modify Timepix chip –> Gossipo Prototyping Lots of ideas Real Challenge! Els Koffeman - VERTEX'06