CBM Silicon Tracking System. R esults of the pre- prototype detector module test .

CBM Silicon Tracking System.Results of the pre-prototype

detector module test.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, V. Militsiya 1, O. Okhrimenko 1, A. Chaus1, B. D. Storozhik1, V. Zhora 4, V. Perevertailo 4,

C. 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)

V. Pugatch CBM Collaboration Meeting, Dubna, Oct. 13-17 2008

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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.


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Prototype for evaluations: 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 …

Negotiations are in progress wrt involvement into the Detector Module Cooling activity of joint German-Ukrainian venture Labor-Technik LTD www.labor-technik.com.ua

http://www.labor-technik.com.ua/


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ASSEMBLY of the Module prototype

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


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Prototype Module assembly scheme

Separated heat flow by making different supporting frames : - for hybrids with readout chips - for Si-sensor (to prevent heating of the sensor)


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Supporting frame A low mass module- to minimize multiple Coulomb-scattering of charged particles in the

detector and support materials. • AEROPLAST(Kiev) – design and production:

Three-layer frames composed by two flat plates (0.25 mm thick) with foam layer (1 mm thick, density - 0.7 g/cm3) in between three types to match the sizes of prototype silicon sensors CBM01, CBM01-B1, CBM01-B2 .


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Microcables for the discrete electronics readout

Side A:Connecting by ultrasonic bondingto sensors

Side B: Connecting by soldering to preamplifiers

4 Different cables were neededfor every type of the sensors:In total, 16 types cables were designed and produced


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Microcables for the discrete electronics readout

CBM01-B2-sensor

50,7 μm – pitch

Double-sided

Sensor is glued to the AEROPLASTCarbon fiber supporting frame

Microcables are bonded to sensor pads:Even strips – to one side; odd strips to the opposite side

LEMO connectors are soldered by wires to large pads on microcables


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Micro-cables suitable for connecting sensors and n-XYTER microchip

A double-layer micro cable

• 25 µm wide, 20 µm thick Al strips• 101.4 µm pitch • on 24 µm thick polyimide film

has been designed and produced at the Institute of Microdevices (IMD, Kiev).

Different cables of that type have been tested using them for the CBM01 (50 x 50 mm2 ) sensor readout by a discrete electronics


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Cooling infrastructureThermo-isolating box shielded against r/f

pick-up has been designed and built.

Thermo sensors (two types) • Pt-100 • Institute of Microdevices (Kiev) production (based on microcable technology)

were installed to monitor temperature at different areas of the detector module


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Cooling infrastructure

Cooling studies


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Cooling infrastructureThermo-mechanical tests with dummy silicon samples glued by silicon glue onto

the supporting frames:

• perfect mechanical rigidity for all supporting frames but one • 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 ).

• Negotiations with joint German-Ukrainian venture Labor-Technik LTD

www.labor-technik.com.ua

http://www.labor-technik.com.ua/


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Sensors characterization

• The first detector module prototypes equipped with 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.


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Sensors characterization

•Mounting sensors on Supporting AEROPLAST frame•Connecting p-, and n-stripsby microcables to LEMO connectors – inputs to PA


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Ra-226, 4 lines – alpha-source.

Cha

rge,

Str

ip ”

k”

Charge, Strip “k+1”

Measurements with radioactive sources

Interstrip gap datastrips functionalitycharge sharing full depletion voltage

Test setup at KINR: coincident energy spectra for pairs of adjacent strips

Irradiation in two steps: 1. from p-side (4-lines structure should be clearly pronounced at any allowed depletion voltage)2. from n-side (4-lines structure should appear at full depletion

voltage)


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Measurements with radioactive sourcesCBM01-B1-sensor 80 μm – pitch,

226 Ra from p-side, p-strips read-out, HV 0 – 50 V

Unexpected performance !Illustrates problem with electric field in the interstrip gap


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CBM01-B1-sensor 80 μm - pitch

226 Ra from n-side,

HV = 10 V HV = 30 V

Approaching full depletion voltage …Yet! There was never clear separationof events belonging to 4 alpha-lines :Thick (10 -15 μm) dead layer from n-side ?

Non-depleted sensor,N-strips are shortened(events along the diagonal)



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Interstrip gap – charge collection efficiency low ?

• Depletion Voltage

0 V 4 V 4 V

Coincident spectra of adjacent strips Single strip spectrum

Sr-90 – β-source (selecting its MIP part). MIP – trigger (high energy tail in PM-2)Measuring PM – Si-strip coincidences.

PM-1

PM-2

Sr - 90

РС –interface

PCPentium1200 MHz

Si-det.

Test Setup at KINR


Measure Landau MIP peak (for p- as well as n-strips)as a function of depletion voltage:Determine full depletion voltage


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Measurements with radioactive sources 90Sr – β-source (CBM01-B2 sensor)

• p-strip MIP-spectra

0 10 20 30 40 50 60 70 800

200

400

600

800

1000

1200

1400

1600

Channel Number

Ev

en

ts

d00.126: Si-strip Component, 10 V

Threshold = 0Threshold = 10Threshold = 30

MIP peak - 10th channel

0 10 20 30 40 50 60 70 800

50

100

150

200

250

300

350

400

450

Channel Number

Ev

en

ts



MIP peak - 16th channel

10 20 30 40 50 60 70 80

10

15

20

25

MIP

Po

sit

ion

, C

ha

nn

el

Voltage, V

MIP-spectra have nice Landau-shape at low depletion voltage, while at higher than 30 V the noise makes it gaussian-like one.


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90Sr – β-source (CBM01-B2 sensor)

• n-strip MIP-spectra – non Landau shape – noise from high leakage current smears spectrum

0 10 20 30 40 50 60 70 800

50

100

150

200

250

300

350

400

Channel Number

Ev

en

ts



MIP peak - 21st channel


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Laser test setup

LHCb Laser setup at Zurich University –Measuring in atmosphere


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Laser test setup at KINR


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Laser test setup CBM01 sensors test results

Interstrip gap is irradiated by focused laser beam. Coincident spectra at different depletion voltage from n –side allow determination of full depletion voltage.

Notice: linear response exists at very narrow central part of the interstrip gap – -close to 5 μm, only - Necessity to measure precisely η-function – for improving hit position resolution


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4th year students from Kiev University – Measuring η-function For the CBM-01 sensor


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Laser test setup at KINRLaser spot moving from onestrip to another onealso changing a spot brightness


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Analog signals from adjacent strips –Laser spot appr.at the middle of the interstrip gap


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Analog signals From adjacent strips-Laser spot is close to one ofthe strips (large amplitude)

-Negative pulse at anotherstrip – reason unknown

Plan to check whether thishappens also for particles


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Summary. Outlook• Test setup (r/a sources, laser, cooling infrastructure) was designed and

built at KINR

• Pre-Prototype Detector Module components (supporting frames, sensors, microcables, cooling) and their connections were tested.

• Results:– B1, B2 - 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).

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CBM Silicon Tracking System. R esults of the pre- prototype detector module test .

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