1. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Considerations on the material budget of the CBM Micro Vertex Detector. Outline: Why a new estimate of the MVD material budget Material Budget as a function of readout time and others Consequences Summary + Conclusion M. Deveaux, University Frankfurt, IPHC Strasbourg

2. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt The conceptional design of the MVD S. Belogurov et. al The question: What is the material budget of this structure? Artistic view on the CBM-MVD

3. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt The material budget of the MVD C. Müntz, CBM Collaboration Meeting, D r esden, Sep 2007 First estimates were done based on experiences of other experiments. Estimate was 0.3 – 0.6 % X 0 But: The thickness of cooling structures depends on necessary cooling power (etc...) CBM requirements are harder than the ones of the cited experiments The material budget of the different components needs to be derived accounting for other design parameters

4. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt The power dissipation of MAPS Sensor array Discriminators On - chip cluster- finding processor Bonding pads + output Amplis. Pixel column Readout bus Only one pixel / col. ac- tive, low power dissipation Permanently biased, high consumption. 1 cell : „P col “ Power scales with occupancy. Neglected in the following Basic assumption: Power scales with number of the end of column logics (discriminator + cluster finding processor)

5. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt The power dissipation of MAPS p p The surface of one collumn is: With: f pixels / s Time resolution of MAPS Readout freq. (Pixels / time) Power of one logic cell pixels

6. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Thickness of the cooling support TPG Cooling Support MIMOSA Heat sink L T1T1 T2T2 Power dissipation MAPS Heat conduction TPG Temperatures d

7. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Thickness of the silicon TPG Cooling Support Sensor DAQ Sensor DAQ SENDAQ SEN Thickness of one chip: 50 µm But we need more than one to cover the blind readout electronics Blind Sensitive Slow MAPS Fast MAPS

8. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Thickness of the silicon Blind Sensitive Blind Sensitive Time resolution of MAPS Readout freq. (Pixels / time)

9. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Material budget of the cables TPG Cooling Support MIMOSA Heat sink Flex print cables Readout electronics L Assumption: Every chip needs one cable (to be refined) Thickness individual cable

10. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Thickness of the full ladder Thickness of glue etc. Full equation: Simplified equation:

11. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Correlations of the thickness Big stations are thick stations Small pixels make thick stations The faster the station the thicker it is What do we learn from this? A fast and simple readout reduces thickness

12. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Correlations of the thickness Big stations are thick stations Reduce L? BUT: We must fit CBM-geometry We have the right to tune the parameters. What are the constraints? Speed up readout? BUT: Low signal analogue electronics. Already optimized to the edge.

13. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Correlations of the thickness Use bigger pixels Generates problems with radiation hardness We have the right to tune the parameters. What are the constraints?

14. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Radiation damage (non-ionizing) „Bulk damage“ caused by massive particles Conduction band Valence band P-Doping Defect states Non-irradiated Irradiated Radiation damage takes effect by trapping signal charge Effect gets more important for long diffusion paths

15. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Correlation of thickness Only smallest pixels will allow for the ambitioned radiation hardness Mi-9 Mi-15 Mi-18 CBM Goal Parallel readout possible

16. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Correlation of thickness Material budget (this work) Earlier studies (radiation hardness aspects not yet known) z = 10 cm

17. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt How to proceed to reduce thickness 15 mm ~ 2...4 mm One might use a particular chip geometry: and move the first station to z = 5cm. ~ 2...4 mm Sensor Discriminator DAQ Bonding

18. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt How to reduce thickness Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding Sensor Read out electronics Bonding y [mm] Dose [ n eq / cm 2 / coll. ] X [mm] BEAM Delta electrons produced in the target Beam hole Delta electron hole Short ladders => few cooling material (scales with L²) No cables in the detector acceptance Delta electron area => Very high occupancy + radiation dose => Accept hole, cover it with extra thin section of the second station ? y x z Delta electron area

19. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt How to proceed First station at z = 5 cm CBM Design goal z = 5 cm R&D?

20. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt The MVD-Computer: Design your own MVD-station See CBM-MVD Wiki

21. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt The MVD-Computer: Design your own MVD-station See CBM-MVD Wiki

22. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Summary and conclusion The material budget of the MVD was studied. It was found to increase with: Increased diameter Increased radiation hardness (smaller pixels) Faster readout The material budget of the first MVD station (z = 10 cm) was found 0.7 - 1.3 % X 0 (assuming today’s MAPS radiation hardness and naive detector design) Achieving an acceptable value (< 0.5 % X 0 ) seems feasible. But all parameters have to be optimized simultaneously. One option: To move the first station back to z = 5cm To put a hole to the region bombarded with delta electrons To consider an readout time of 20 µs instead of 10 µs A software, the „MVD-Computer“ is provided to support this optimization There are still many preliminary parameters used. Detailed knowledge is needed for precise estimates on the material budget

23. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Delta electrons and occupency Relative Occupency (@ 5cm)

24. M. Deveaux, CBM-Collaboration-Meeting, 25 – 28. Feb 2008, GSI-Darmstadt Internal structure of a MAPS - chip Sensor array ~1000 on - chip ADCs and/or discriminators On - chip cluster- finding processor Output: Cluster information (zero surpressed) SensorBlind area Bonding pads Every MAPS-Chip contains a sensitive and a blind area Blind area of one chip needs to be covered by sensor of second chip