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

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

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

4. 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

5. 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

6. Micro Vertex Detector
Els Koffeman - VERTEX'06

7. 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

8. 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

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

10. 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

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

12. 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

13. 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

14. 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

15. 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

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

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

18. Preliminary
Els Koffeman - VERTEX'06

19. 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

20. 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

21. 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

22. 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

23. Energy resolution in Argon IsoC4H10 80/20
Observation of two lines:
5.9 keV
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

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

25. 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

26. 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

27. 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