CBM Silicon Tracking System.First results of the detector module pre-prototype test.

V.M. Pugatch Kiev Institute for Nuclear Research

11th CBM Collaboration Meeting, GSI, Darmstadt, February 27th ‘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

4 cm

2 cm

8 cm

principle of "long-ladder" design

thickness: 200 µm Si + 3100 µm Kapton + 3 20 µm Al : ~ 400-500 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

• 1st 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 - 0.7 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

Autonomous cooling (traditional) where a metal hybrid is used. The heat-producing readout chips are placed upon the hybrid which is

cooled by the water.

Support frames with internal circulation of water inside (proposed by “Aeroplast”). More

complicated but has its own advantages. No need to use metal hybrids: less mechanical strain and better cooling of silicon sensor which will also

produce heat due to increase of reverse current.

A solid rectangular plate of carbon fiber, light foams

(density 0.1-0.2 g/cm3) with small empty glass spheres,

other materials with density 0.7-0.8 g/cm3.

Size:  ≈(60x200)  mm2. Thickness: 1.65 mm

A hollow plate with channels for cooling agent

inside and a “fork” at its end.

Size: (60x160) mm2, relatively large thickness (3 mm).

2 versions of supporting frames:

• Supportting frames produced in Kiev by “Aeroplast”

• (see also next slides for sizes etc.,)

Mass minimization Cooling problemWe should use support frames of light materials, thin micro-cables (40 um

thick, up to 0.5 meter long)

Due to large number of read-out chips (8x2 in case of CBM01 sensor type)

12

Alternative approach (commercial)

www.swiss-composite.ch/

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

0 10 20 30 40 50 60 700

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Voltage, V

Cu

rre

nt,

A

VA - characteristic

Vitya (16.02.08 am)Sasha (21.02.08)V.O. (16.02.08 pm)

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 mounting2. Electrical connections 3. Cooling flow, temperature

What has to be tested/measured(quality assurance):

1. Operating channels 2. Full depletion voltage 3. Leakage currents4. Signal/Noise 5. Long tem stabilityOUTCOME: 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.

Cha

rge,

Str

ip ”

k”

Charge, Strip “k+1”

CBM01-B1

226 Ra from

n-side,

n-strips 7@8

HV = 10 V HV = 30 V

E7

E8

E7

E8E8

E8

No.events

Two-dimensional distributions for n-side stripsEn7 vs En8

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 Ep5 vs Ep6

for alpha-events: Irradiation from p-side.HV from 0 to 70 V

CBM01-B1

226 Ra from

p-side,

p-strips 5@6

CBM01-B1

226 Ra from

p-side,

n-strips 9@10

Two-dimensional distributions for n-side strips

En9 vs En10

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 5@6

at HV = 50 V

HV = 30 V HV = 70 V

2-D spectra for

n-strips 7@8

2-D spectrum for

p-strips 7@8

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

PCPentium1200 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 …