CBM Silicon Tracking System. First results of the detector module pre-prototype test. V.M. Pugatch Kiev Institute for Nuclear Research 11 th CBM Collaboration Meeting, GSI, Darmstadt, February 27 th ‘08 Thanks to coauthors: M. Borysova 1, J.M. Heuser 2, O. Kovalchuk 1, V. Kyva 1, A. Lymanets 1,3, V. Militsiya 1, O. Okhrimenko 1, V. Zhora 4, V. Perevertailo 4, A.Galinskiy 5 1 KINR, Kiev 2 GSI, Darmstadt, 3 now at FIAS, J.W. Goethe University, Frankfurt, 4 Institute of Microdevices (Kiev) 5 SPA AEROPLAST (Kiev)

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

dead zones  overlaps r/o 4 cm 2 cm 8 cm principle of "long-ladder" design thickness: 200 µm Si + 3  100 µm Kapton + 3  20 µm Al : ~ µm Si equiv. flat cable: challenge!! J. Heuser

LHCb Silicon Tracker – supporting boxes with cooling pipes Cooling infrastructure and temperature monitoring for the CBM detector module - design at the AEROPLAST (Kiev). Cooling inside of the supporting ladders …

ASSEMBLY of the Module prototype 1 st prototype – the design similar to the long ladders of the LHCb Silicon Tracker – modified for the double-sided version of sensors

Prototype Module: assembly scheme

Supporting frame A low mass STS - to minimize multiple Coulomb-scattering of charged particles in the detector and support materials. In 2007 few versions of the supporting frame for the CBM01, CBM01B1, CBM01B2 sensors were produced by AEROPLAST (Kiev). Construction material - Carbon Fiber (CF) material budget below 0.3% X0. low-Z material, minimization of the mass, maximum rigidity, perfect flatness, geometric thickness less than 2.5 mm, stable mechanical properties in the temperature region from -5 to 50 degrees C. Approximate weight proportions: 65% - carbon, 35 % - epoxy resin -> a density 1.5 times less than Al-alloys, elasticity module – at the level of the steel, coefficient of the thermal expansion in the temperature region +/- 60 deg. C - close to zero. Three-layer frames composed by two CF plates (0.25 mm thick) with Foam Layer (1 mm thick, density g/cm3) in between them were produced in three type of geometry shape to match the sizes of prototype silicon sensors.

LHCb IT Si-module composition From top to bottom: Si-sensors, Kapton foil, Carbon fiber, Foam, Carbon fiber

2 versions of supporting frames:

Supportting frames produced in Kiev by “Aeroplast” (see also next slides for sizes etc.,)

12 Alternative approach (commercial) Ready-to-use Al hybrid already implemented Thin Rigid

CBM-01 sensors at the supporting frame

Still a long way… - LHCb IT detector module (Si- single-sided)

… especially if to look into the details

Tests The first pre-prototypes equipped with CBM01B1 as well as CBM01B2 sensors have been mounted and connected to a discrete electronics at the readout board. Tests are performed at KINR : Radioactive source Laser (640 nm)

CBM01-B1 Si microstrip detector: p-side

I-V measurements at KINR CBM01-B1

Anton Lymanets Current-Voltage characterization of full batch of CBM01 sensors (1-24) at CIS

TEST – Quality assurance system - final goal What has to be checked: 1.Mechanical mounting 2.Electrical connections 3.Cooling flow, temperature What has to be tested/measured (quality assurance): 1.Operating channels 2.Full depletion voltage 3.Leakage currents 4.Signal/Noise 5. Long tem stability OUTCOME: Map of the operating channels of the CBM tracker.

TEST - Quality Assurance at KINR Ra-226, 4 lines – alpha-source. Interstrip gap – strips functionality, charge sharing, full depletion voltage, leakage current: Eight channels Test setup at KINR – built and running with discrete Electronics. Charge, Strip ” k” Charge, Strip “k+1”

CBM01-B1 226 Ra from n-side, n-strips HV = 10 V HV = 30 V E7E7 E8 E7E7 No. events Two-dimensional distributions for n-side strips E n7 vs E n8 for alpha-events: Irradiation from n-side See also next slides illustrating sensor performance: increasing bias voltage – from 0 to 70 V

HV = 0 V HV = 2 V HV = 3 V HV = 4 V HV = 5 V HV = 50 V HV = 70 V Two-dimensional distributions for p-side strips E p5 vs E p6 for alpha-events: Irradiation from p-side. HV from 0 to 70 V CBM01-B1 226 Ra from p-side, p-strips

CBM01-B1 226 Ra from p-side, n-strips Two-dimensional distributions for n-side strips E n9 vs E n10 for alpha-events: Irradiation from p-side. HV from 0 to 70 V HV = 50 V HV = 70 V HV = 0 V HV = 30 V

Laser test setup Similar to LHCb Laser setup at Zurich University – Measuring in atmosphere

CBM01-B1 Moving Laser (640 nm) at p-side 2-D spectrum for p-strips at HV = 50 V HV = 30 V HV = 70 V 2-D spectra for n-strips 2-D spectrum for p-strips at HV =50 V

Cooling Thermo-mechanical tests with dummy silicon samples glued by silicon glue onto the supporting frames: perfect mechanical rigidity thermo-conductivity appr. 0.6 W/m*deg in the longitudinal direction A special design has been developed for investigating cooling by circulating a liquid agent in hollow plates. Currently such structure didn’t show needed mechanical stability. It might be improved at the price of increasing the transversal size of the frame up to 5 mm (keeping material budget still within a required 0.3 X0 ).

LHCb detector modules mounted at the cooling balcony

Prototype Module assembly scheme- similar to the HERA-B double-sided Separated heat flow by making different supporting frames : - for hybrids with readout chips - for Si-sensor (to prevent heating of the sensor)

Micro-cables The readout of the microstrip sensor is planned to be performed through low-mass long readout cables with the same pitch as the sensor strips. A double-layer micro cable with 25 µm wide, 20 µm thick Al strips of (2 x 50.7) µm pitch on 24 µm thick polyimide film is currently under development at the Institute of Microdevices (IMD, Kiev). The pitch of the strips was chosen to match that of the readout chip n- XYTER that will serve for detector prototyping in the CBM experiment. A micro cable must feed signals at distances up to 0.5 m, which creates high input capacitance for read-out micro chip. This problem has been simulated using micro cables of similar structure, but with less capacitance. In this approximation pick-up signal was of the order of 1% of the main signal. Currently, three-layer micro cables (with the grounded layer in the middle) are also under design at IMD (Kiev) aimed at the prevention of a pick-up problem.

TEST – Quality Assurance Signal/Noise Ru-106 – source. MIP – hit triggering (two PM coincidences). PM-1 PM-2 Ru-106 РС – interface PC Pentium 1200 MHz Si-det. Test Setup built and running at the KINR for (8 x n) channels

Conclusions. Outlook Pre-Prototype Supporting Frames for Detector Modules assembling by CBM01, -B1, -B2 sensors were built and studied. Test setup (Laser and r/a sources) at KINR based on the discrete readout electronics has been built and used for the CBM01-B1 sensor characterization. Functionality of the B1-sensor has been demonstrated at the expected bias voltage. B2 sensors connected by microcables to the read-out board will be characterized next month. Next studies: sensor/support-infrastructure/flat-cable performance, S/N for MIPs, long term stability etc.,

KINR – in CBM …