1. CBM Collaboration Meeting. GSI, Darmstadt. 10.03.2009 CBM Silicon Tracking System. CBM-01 sensors characterization. V.M. Pugatch Kiev Institute for Nuclear Research Thanks to coauthors: M. Borysova 1, J.M. Heuser 2, O. Kovalchuk 1, V. Kyva 1, A.Lymanets 1,3, A. Melnyk 1, V. Militsiya 1, O. Okhrimenko 1, A. Chaus 1, D. Storozhik 1, V. Zhora 4 1 KINR, Kiev 2 GSI, Darmstadt, 3 now at FIAS, J.W. Goethe University, Frankfurt, 4 Institute of Microdevices (Kiev)

2. R&D: Agreement ‘KINR-GSI’ A low-mass mechanical assembly of double-sided silicon microstrip sensors and their connection through analog readout cables to a readout electronics construction of an experimental test stand A quality assurance procedure suitable for a future larger detector module production.

3. Mounting CBM01 sensor Hollows were made in a supporting frame (AEROPLAST Carbon fiber) supporting frame to allow bonding from both sides of the double-sided CBM01 sensor Two-layer micro-cables were produced and bonded (IMD, Kiev) to match 50.7 μm pitch CBM01 sensor (50 x 50 mm 2 ) : Even strips – to upper layer (101.4 μm pitch); odd strips to the bottom layer (101.4 μm pitch); - the same structure for p- and n-side of a sensor.

4. Micro-cables A double-layer micro cables 25 µm width 20 µm thick Al strips 101.4 µm pitch on 24 µm thick polyimide film have been designed and produced at the Institute of Microdevices (IMD, Kiev). Different cables of that type have been tested by implementing them for the CBM01 sensors readout

5. Sensors characterization CBM01B1, CBM01B2 as well as CBM01 sensors have been mounted and connected to a discrete electronics at the readout board. Tests are performed at KINR using laser pulses (640 nm) and radioactive sources. IV - CBM01 Laser pulse amplitude at n-side strips as a function of the applied voltage (irradiation from the n-side). Full Depletion Voltage- CBM01

6. Laser Stand - a part of the Quality Assurance System Laser Stand (LS) for testing STS Si-microstrip detector modules has been designed and built at KINR. laser beam wavelength – 640 nm, diameter of the laser beam spot ~10 µм step in X and Y – directions (15x15 cm 2 ) –10 µм. Response of two adjacent strips: Laser beam was moved from one strip to another. Software/hardware allows to move a laser beam over the silicon detector surface.

7. Laser beam characterization of CBM01 sensors Charge, Strip ” k” Charge, Strip “k+1” Total pulse amplitude from two adjacent strips versus detector voltage (laser beam, 640 nm, from the p-side). Two-dimensional spectra show unexpected performance of the inter-strip gap: total amplitude goes down at 40 V in comparison with unbiased sensor, linear inter-strip region gets narrower at 40 V (from 25 to few μm). The figures near dots indicate the coordinate of laser spot (in μm)

8. Ra-226, 4 lines – alpha-source. Charge, Strip ” k” Charge, Strip “k+1” Measurements with radioactive sources Interstrip gap data strips functionality charge sharing full depletion voltage leakage current Test setup at KINR: coincident energy spectra for pairs adjacent strips Spectrum is deteriorated when a biasing voltage is applied. Amplitude of signals decreases: Unexpected performance in the inter-strip gap

9. Sr-90 – β-source. MIP – hit trigger PM – Si-strip coincidences. PM-1 PM-2 Sr - 90 РС – interface PC Pentium 1200 MHz Si-det. Test Setup built and running at the KINR for (8 x n) channels Measurements with radioactive sources

10. Measurements with radioactive sources 90 Sr – β-source (CBM01 sensors) p-strip MIP-spectra MIP-spectra for all types of sensors have Landau-shape at low bias voltage. At bias voltage higher than 30 V it is of a gaussian shape.

11. Summary. Pre-Prototype Detector Module components (supporting frames, sensors, microcables, cooling) and their connections were produced and tested. All type of CBM01 sensors: -Unexpected performance in the interstrip gap. -Long term instability of the leakage current Supporting frames perfect features (low mass, mechanical rigidity, thermoconductivity, easy connection and geometry shaping etc.,) Microcables (including double-layer structure) perfect electrical and mechanical features matching CBM request. Real Modules assembly and their Quality Assurance could be provided by KINR in collaboration with IMD (Kiev), IAP (Sumy) and AEROPLAST (Kiev).