Deveaux, M.

Koziel, M.

Müntz, C.

Stroth, J.

Tischler, T.

GSI Repository

The CBM-MVD: Progress in Mechanical Integration ∗M. Koziel1, T. Tischler1, C. Mu¨ntz1, M. Deveaux1, and J. Stroth1,2 for the CBM-MVD collaboration1Institut fu¨r Kernphysik, Goethe-Universita¨t, Frankfurt, Germany; 2GSI Darmstadt, GermanyThis report summarizes the activities undertaken towardsthe construction of the Micro Vertex Detector (MVD) of theCompressed Baryonic Matter (CBM) experiment.Quality assurance of 50 µm thin PRESTO sensors:Thinned MIMOSA-26 sensors will be used for assemblythe so called PRESTO module. PRESTO addresses thedouble-sided integration of 15 MIMOSA-26 sensors (dum-mies and working sensors) onto a 8 × 8 cm2 CVD di-amond support (see [1] for more details). Sensors willbe connected with the R/O system by means of a newlydesigned ultra-low material budget flex cable employingcommercially available processes based on copper traces[2]. Constructing the PRESTO allows to estimate the inte-gration yield providing that the employed sensors are testedprior to assembly. Up to now, 18 MIMOSA-26 AHR sen-sors thinned to 50 µm were probe tested using the setupdescribed in [3]. The setup allows testing the standard op-eration modes of the sensor as well as measure the fixedpattern and temporal noise by the means of so called s-curves. 12 sensors were found without a significant num-ber of dead/noisy pixels; they were qualified as fully oper-ational. Four sensors exhibiting some dead rows/columnswere marked as faulty. The two remaining sensors were notoperational due to a power supply short (one sensor) andproblems while powering one out of the four MIMOSA-26sub-matrices. The estimated yield was then of about 65%which is in agreement with expectations for this type ofsensors [4]. The temporal noise was found to be of about1.6-1.8 mV and the fixed patter noise of about 0.5-1.0 mV.This is by factor of 2-3 higher than the noise specifiedby a sensor provider. This was nevertheless as expectedsince the sensor power signals were generated outside theprobe card. The addressed probe tests allowed also to es-tablish test procedures required for non-destructive tests ofthinned CMOS sensors and can be applied for testing thefinal MVD sensors.Development of a custom made glue: An ”ideal”adhesive for the integration of the sensors onto their sup-ports should be easy to dispense in a thin and uniformlayer—calling for a low viscosity—, radiation hard as wellas flexible (to compensate for the thermal expansion mis-matches between the sensor and their support material)within the temperature range foreseen for the operation ofthe MVD sensors. Since there are none ”on-shelf” productsthat meet these requirements, a custom-made, two com-pound adhesive with a working name RAL-247 was man-∗This work has been supported by BMBF (05P12RFFC7), EU-FP7HadronPhysics3, HGS-HIRe, GSI and HIC for FAIR.ufactured at the Rutherford Appleton Laboratory (RAL),Composites and Materials Testing Group, UK. The gluefeatures a glass temperature of -45 ◦C, a viscosity of be-low 100 mPa·s and a curing time of 48 h at +50 ◦C. Toinvestigate its radiation hardness, RAL-247 samples wereirradiated with X-rays to 100 Mrad and to a proton dose ofabout 1015 neq/cm 2. The irradiated samples were sent toRAL for further Dynamic Mechanical Analysis tests whichunraveled no significant change of properties [5] that con-firms the expected radiation hardness at the range of radia-tion doses expected at the MVD.Development of the heat sinks for the MVD: Theoperation of the MVD in vacuum requires a continuouscooling of the sensors to limit radiation induced defects aswell as noise. To keep the material budget of the individualMVD station as low as possible, the cooling approach ofthe MVD employs highly thermal conductive sensor sup-port materials (CVD diamond [6] and encapsulated highperformance graphite) in the acceptance of the MVD andactively cooled aluminum-based heat sinks outside of thisarea. To evaluate the cooling concept and its vacuum com-patibility, half-station heat sinks of the first three MVD sta-tions were manufactured at COOLTEK GmbH. The heatsinks incorporate a buried cooling pipe and have thermallybeen simulated prior their manufacturing using a worst casescenario for the sensor power dissipation plus an additionalsafety factor of four. These heat sinks are currently be-ing evaluated under laboratory conditions focusing on theirvacuum compatibility [7]. The heat dissipation of the MVDsensors is provided by kapton insulated flexible heatersfrom OMEGA Engineering, INC.References[1] M. Koziel et al., ”PRESTO: PREcursor of the Second sTatiOnof the CBM-MVD.” GSI annual report 2014.[2] P. Klaus et al., ”Ultra-low material budget Cu flex cable forthe CBM-MVD. ”GSI annual report 2014.[3] M. Koziel et al., GSI annual report 2013.[4] L. Greiner et al., CPIX 2014, Bonn, Germany[5] Private communication, Simon Canfer Rutherford AppletonLaboratory, Composites and Materials Testing Group, UK.[6] Diamond Materials GmbH, Germany[7] G. Kretzschmar et al.,”Vacuum compatibility of the CBM-MVD.” GSI annual report 2014.MU-NQM-CBM-18 GSI SCIENTIFIC REPORT 201454 DOI:10.15120/GR-2015-1-MU-NQM-CBM-18

The CBM-MVD: progress in mechanical integration

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The CBM-MVD: progress in mechanical integration

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