Status of the Prototype of the CBM Micro Vertex Detector M. Deveaux, Goethe University Frankfurt for the CBM-MVD collaboration

2 Physics goals of CBM CBM M. Deveaux Important probe: Open charm

Open charm reconstruction: The challenge M. Deveaux 3 [W. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745] SIS18 SIS100 SIS300 A collision rate of ~10 5 /s Au+Au is required

M. Deveaux, 4 Open charm reconstruction: Concept Primary Beam: 25 AGeV Au Ions (up to 10 9 /s) Primary vertex Secondary vertex Short lived particle D 0 (c  = ~ 120 µm) Detector 1 Detector2 Target (Gold) z Reconstruction concept for open charm Reconstructing open charm requires: Excellent secondary vertex resolution (~ 50 µm) => Excellent spatial resolution (~5 µm) => Very low material budget (few 0.1 % X 0 ) => Detectors in vacuum A good time resolution to distinguish the individual collisions (few 10 µs) Very good radiation tolerance (>10 13 n eq /cm²) Central Au + Au collision (25 AGeV)

M. Deveaux 5 Sensors for the MVD CBM SIS300 MAPS* (2003) MAPS* (2012) MIMOSA-26 Binary, 0 Single point res. ~ 5 µm1.5 µm1 µm4 µm Material budget < 0.3% X 0 ~ 0.1% X 0 ~ 0.05% X 0 Rad. hard. non-io. >10 13 n eq n eq /cm²>3x10 14 n eq >10 13 n eq Rad. hard. io > 3 Mrad200 krad> 1 Mrad> 500 krad Time resolution < 30 µs~ 1 ms~ 25 µs110 µs Optimized for one parameter Current compromise Monolithic Active Pixel Sensors (MAPS, also CMOS-Sensors) Invented by industry (digital camera) Modified for charged particle detection since 1999 by IPHC Strasbourg Also foreseen for ILC, STAR, ALICE… => Sharing of R&D costs.

The MVD for SIS100 M. Deveaux 6 Status of FAIR: SIS100 available 2018 SIS300 available later Need SIS300 for open charm production in A-A Physics cases at SIS100 (MVD) Measure open charm in p-A (p-p?) collisions  Needs ~10 6 p-Au collisions/s Measure light vector mesons in A-A collisions  Use MVD as low momentum tracker  Tag and reject conversion pairs => reduces Background  Needs ~10 4 Au-Au collisions/s

M. Deveaux 7 Running conditions (SIS-100): S. Seddiki, C. Dritsa Radiation doses per year, incl. factor 3 security margin Occupancy incl. factor 10 security margin Mi-26p-A Au-Au Au-Au Max. coll. rate [Hz] “1x10 4 ”2x10 6 2x10 4 Peak occupancy [%] Ionizing rad. dose [MRad] Non Io. rad. dose [n eq /cm²] > 1x x x x10 13

M. Deveaux 8 Status of the sensor R&D

M. Deveaux 9 Sensor R&D: The operation principle Reset +3.3V Output SiO 2 N++ N+ P+ P- P+ 15µm 50µm

10 Sensor R&D: Tolerance to non-ionising radiation +3.3V Output SiO 2 N++ N+ SiO 2 P++ GND +3.3V Non-ionising radiation Energy deposit into crystal lattice

11 Sensor R&D: Tolerance to non-ionising radiation +3.3V Output SiO 2 N++ N+ SiO 2 P++ GND +3.3V Key observation: Signal amplitude is reduced by bulk damage

12 Sensor R&D: Tolerance to non-ionising radiation +3.3V Output SiO 2 N++ N+ SiO 2 P++ GND +3.3V Electric field increases the radiation hardness of the sensor Draw back: Need CMOS-processes with low doping epitaxial layer E

S/N of MIMOSA-18 AHR (high resistivity epi-layer) M. Deveaux 13 Plausible conclusion: Radiation tolerance ~10 14 n eq /cm² reached Cooling required to operate heavily irradiated sensors Preliminary Safe operation Mimosa-9 (2005) 20 µm standard epi 0.2 x n eq /cm² D. Doering, P. Scharrer, M. Domachowski D.Doering, HK 12.8 P. Scharrer,HK 53.13

Sensor R&D: Tolerance to ionising radiation M. Deveaux 14 Pixel with pedestal correction ~1000 discriminators On - chip cluster-finding processor Output: Cluster information (zero surpressed) Imagers: Tolerate 1-2 MRad if cooled. Fast pixels are so far vulnerable: More transistors No space for radiation tolerant layout in 0.35µm CMOS.  Current tolerance: 0.5 MRad Next steps: Migrate design to 0.18 µm CMOS process  Higher intrinsic radiation tolerance  Less space constraints Status: First sensor (MIMOSA-32) under test. M. Koziel, PhD

15 Tolerance to non-ionising radiation - Annealing Annealing alleviates ionizing radiation damage substantially No indication for reverse annealing => Recover detector on the fly(?) D. Doering MIMOSA-19 imager

M. Deveaux 16 MVD-Simulation

Global design: How many MVD stations? M. Deveaux 17 5 cm Target MVD 1MVD 2 STS 1STS 2STS 3 Vacuum window

Global design: How many MVD stations? M. Deveaux 18 5 cm Target MVD 1MVD 2 STS 1STS 2STS 3 Vacuum window

Global design: How many MVD stations? M. Deveaux 19 5 cm Target MVD 1MVD 2 STS 1STS 2STS 3 Vacuum window

Global design: How many MVD stations? M. Deveaux 20 5 cm Target MVD 1MVD 2 STS 1STS 2STS 3 Vacuum window

Global design: How many MVD stations? M. Deveaux 21 5 cm Target MVD 1MVD 2 STS 1STS 2STS 3 Vacuum window

Global design: How many MVD stations? M. Deveaux 22 5 cm Target MVD 1MVD 2 STS 1STS 2STS 3 Vacuum window

Global design: How many MVD stations? M. Deveaux 23 Open charm in Au-Au 25 AGeV, accepted background tracks per collision. Bad reconstruction Some bad hits Good hits Accepted after cut on: p > 1 GeV p t > 0.3 GeV Impact parameter Not applied: Secondary vertex cut Impact parameter of mother particle Adding a third station might improve system performance substantially ! Needs full physics simulation before concluding C. Trageser, HK 53.19

Global design: How many MVD stations? M. Deveaux 24 5 cm Target MVD 1MVD 2 STS 1STS 2STS 3 Vacuum window e+e+ e-e- Sensor response simulation: J. Enders - HK M. Domachowski - HK 57.5

System integration – An MVD for CBM M. Deveaux 25 CBM-MAPS consume ~1W/cm² How to bias? How to evacuate heat? … …without material Aim for thickness of 0.3% X 0 (=0.3 mm Si equivalent) How to fix the sensors? … in vacuum?

Integration concept of the MVD Vacuum operation requires light and actively cooled device. Use cooling support from diamond to move heat out of acceptance Put heat sink and FEE outside acceptance CBM acceptance Outside acceptance Beam hole z[cm]r out r in r out Geometry of MVD-stations

Discri Sensor Discri Sensor Discri Sensor Discri Sensor Discri Sensor Discri Sensor Discri Sensor M. Deveaux 27 T. Tischler MIMOSIS1B MIMOSIS1A Discri Sensor Discri Sensor Discri Sensor Integration concept of the MVD MVD Prototype (mock up)

Simulation: Material budget of a first MVD station Conservative estimate close to 0.3% X 0 Improve using FPC with aluminum T. Tischler 300 µm Si equivalent Sensor Cable Support Heat sink

Validation of the cooling concept W / 16 cm²  T = ~10K Vacuum compatible cooling concept for 1W/cm² seems robust. Aim: Validate the cooling concept with TPG Observation: Temperature gradient on the station appears acceptable A 150 µm CVD diamond support might be sufficient for station 1 Diamond => liquid heat transport needs optimization T. Tischler

Prototype: Beam test setup M. Deveaux 30 Ambitioned performances: Up to 10 MIMOSA-26 frames/s, 3.5µm resolution. Local DAQ based on HADES TRB Gbps data, scalable. Actively cooled prototype (<0.3% X 0 ) Passively cooled telescope arms (0.05% X 0 ) T. Tischler MVD Prototype Reference telescope

Prototype: Beam test setup M. Deveaux 31 2 MIMOSA-26 operated with …. the prototype readout electronics See C.Schrader, HK 41.5 See B. Milanovic, HK 41.6

Summary M. Deveaux 32 CMOS MAPS provide an unprecedented compromise between precision measurements and rate capability. Their performances were massively improved within 10 years. MAPS are considered for STAR, CBM, ILC, ALICE, eRHIC … => Industrial trends help: Expect further improvements Integration concept for the CBM-Micro Vertex Detector: Host MAPS on a vacuum compatible diamond cooling support Readout with ultra thin flex print cables Build local DAQ based on HADES TRB Status: Prototype under construction, beam test middle 2012

Outlook: The story has just started Idea from R. De Oliveira, W.Dulinski SERNWIETE (mechanical demonstrator) A bended MIMOSA-26 in a foil Thanks to the CBM-MVD collaboration: PICSEL group, sensor production AG Prof. Stroth, MVD integration radiation tolerance studies M. Deveaux