The NA61 Vertex Detector Considerations on site M. Deveaux, Goethe University Frankfurt

What is the topic ? M. Deveaux, NA-61 Collaboration Meeting, October The properties of the MIMOSA-26 sensors (reminder) Operating MIMOSA-26 in an 2015 heavy ion run with NA61? Lessons learned on this meeting

3 CMOS-MAPS, the fundamentals Monolithic Active Pixel Sensors (MAPS, also CMOS-Sensors) Invented by industry (digital camera) Modified for charged particle detection by the PICSEL group, IPHC Strasbourg Selected communities participating in MAPS R&D CBM MVD ALICE ITS STAR HFT EU-DET TESLA ILC Vertex AIDA

M. Deveaux 4 MIMOSA-26: The operation principle Reset +3.3V Output SiO 2 N++ N+ P+ P- P+ 15µm 50µm

Pixel readout concept 5 External ADC Sensor Offline Cluster finding Output Add pedestal correction ~1000 discriminators On - chip cluster-finding processor Output: Cluster information (zero surpressed) MAPS are built in CMOS technology Allows to integrate: sensor analog circuits digital circuits on one chip.

Block diagram of MIMOSA-26 M. Deveaux, NA-61 Collaboration Meeting, October x analog out (obsolet) Readout sequencer Slow control interface (JTAG) Bias DACs (Threshold generation…) Coll. discri- minators Zero suppr. computer Output memory Sensor array (21200 x µm²) 18.4 x 18.4 µm pixel pitch

The NA-61 MVD, a spin-off of the CBM-MVD project? M. Deveaux, NA-61 Collaboration Meeting, October The CBM-MVD prototype: Based on 12 MIMOSA-26 Results from SPS-beam test: MIP efficiency: > 99 % Spatial resolution: ~ 4 µm Vacuum compatible cooling support (CVD diamond) Material budget: <0.3% X 0 (incl. two silicon layers and support) The CBM-MVD prototype is not meant for physics but it has about the complexity of the NA61 prototype NA61 may start its activity supported by existing know how and tested hardware components

The idea: An MVD prototype which might see open charm M. Deveaux, NA-61 Collaboration Meeting, October [W. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745] SIS18 SIS100 SIS300 SPS CBM ~ D/coll. NA-61~ 0.1 D/coll. CBM - >> 50 kHz (heavy ion, minimum bias, untriggered) NA Hz (out of 2 kHz minimum bias, triggered)  A measurement within 2015 HI-run might see open charm  But: Needs a complex detector system

Our understanding of the geometry M. Deveaux 9

Location of the MVD M. Deveaux 10 Beam pipe Beam Position monitor Target “Aquarium” “Diffusion pump” Magnet cooling

Location of the MVD M. Deveaux 11 Requirements: Minimal material within the +/- 45° acceptance of NA61 TPC sensitive to temperature changes => Keep 20°C stable No particular precautions concerning EM-compatibility needed Should rather hang on rails than stand on magnet support system Keep front of the detector air tight Sufficient space for cooling system + electronics available

M. Deveaux 12 An alternative geometry proposal

M. Deveaux 13 An alternative geometry proposal Total: 8 chains (1 TRB-3) to steer 12 sensors

Accounting for Sergeys ladders M. Deveaux 14 Limited manpower for design/production  Minimize complexity  Use only one kind of ladder  Ladder must match size of last station  Box will be cubic Beam hole Detector plane Ladder

Integration of the box M. Deveaux 15 1) Need cubic box, hanging on rails 2) Beam pipe and target holder need to be adapted 3) Space between box and Vtx-TPC is used for thermal isolation Open issue: Vibration/Stability – Detector resolution < 4µm

Accounting for acceptance M. Deveaux 16 Beam hole Detector plane Ladder CBM-MVD single sided prototype Constraints: Need opening angle 45° Max. 25 cm Max. 10 cm  Need reworked readout cables + Money and manpower

Ladders, strong and weak points M. Deveaux 17 + Outstandingly low material budget + Perfect cooling power + Highly integrated device - Width only 15mm - Problems with thermal expansion  Ladder is bent at room temperature  Bending radius temperature dependent - Ladder seems flexible

Integration on the ladder, open issues M. Deveaux 18 14mm 15mm Cable… width ( ) = 2 sensors in reality Ladder not wider than sensor  No landing space for cable  Cable integration not possible Ladder flexible  Wire bonding works with ultra-sound  Sound might be absorbed  Feasibility of bonding needs to be demonstrated

Integration M. Deveaux 19 Cable Sensor Option A – Move Sensor 5mm 50µm Colling issues might be solved but: Extreamly fragile => R&D + extreamly high risk Cable Sensor Option B – Extend ladder Solved integration issues but: Needs new tooling Eventually new R&D => R&D + costs + manpower In any case: Bonding has to be demonstrated, might need dedicated tools

System protection and interlock M. Deveaux 20 Beam hole, 6mm diameter Sensors are very close to the beam: =>During beam tuning, sensors may be hit by beam =>In case of trim magnet failure, sensors might be hit Tolerance of sensors to heavy ions is unknown (to me) =>Don’t take risks, consider protection systems =>Might base on veto detector

System protection and interlock M. Deveaux 21 Beam hole, 6mm diameter Sensors are very close to the beam: =>During beam tuning, sensors may be hit by beam =>In case of trim magnet failure, sensors might be hit Add mechanics to drive out the sensors during beam tuning !!! The sensors, not the full box Use this mechanics to extend beam hole in case of beam focusing problems

System protection and interlock M. Deveaux 22 Beam hole, 6mm diameter Sensors are very close to the beam: =>During beam tuning, sensors may be hit by beam =>In case of trim magnet failure, sensors might be hit Add interlock: a)Move out sensors in case of beam loss b)Dump beam (if possible) Not clear if b) will work, a) will need >1s Have to check tolerance of MAPS to ions (?)

DAQ & electronic issues M. Deveaux 23 TRB3 FPGA Board Purchase: M. Traxler, GSI NA61 DAQ A black box… … but it does certainly exist Somewhat not addressed during this meeting  Remains to be done

My personal conclusion M. Deveaux 24 Very useful meeting so far Collected some answers and many important questions Collected constraints for integration to NA61 Ladder design: Need to decide if (high risk) integrate on existing ladder of (high efford) modify ladder Need engines to drive out detector (interlock). Existing veto detector might trigger this. Need to understand tolerance to heavy ions DAQ still pending Still a lot of work to be done, project complexity increases.