ILC Vertex Tracker Ladder StudiesAt LBNL

M Battaglia, D Contarato, L Greiner, D ShumanLBNL, Berkeley

Mechanical Test Facilities at LBNLMechanical Test Facilities at LBNL

Lucite wind tunnel Thin silicon ladder,

tension support

Laser light source

Camera

● Environmental chamber (down to -70ºC) for characterization of temperature cycling and humidity effects on prototype ladders

● High resolution IR camera for studying temperature gradient of prototype ladders

● Facility for studies of cooling and mechanical stability with nitrogen and air flow, equipped with a laser holography system for real time measurement of distortions in prototype structures with sub-µm resolution

● Capacitive probe system with sub-µm resolution; study displacements and vibrations induced by air cooling or other forces

● Composite materials lab for fabrication of light structures

VTX Ladder Design & TestingVTX Ladder Design & Testing

• LCRD funding supports new program of engineering design, construction and characterization of full ladder equipped with back-thinned CMOS pixel sensors in collaboration with STAR HFT project

0.282% X0

• STAR low mass carrier: 50m CFC+3.2mm RVC+50m CFC (=0.11%X0)

0.282Total

0.11CF / RVC carrier

0.0143Adhesive

0.090Cable assembly

0.0143Adhesive

0.0534MIMOSA detector

% radiation lengthComponent

VTX Ladder Design & TestingVTX Ladder Design & Testing

X

Y

Z

2-15 2-20 2-26 2-29 2-30 2-32 2-27 2-1

X

Y

Z

2-15 2-20 2-26 2-29 2-30 2-32 2-27 2-1

STAR study of accuracy of chip positioning on carrier:50 m back-thinned MIMOSA5 are positioned using a vacuum chuck with alignment bump edge and individual vacuum chuck valves

20.32

20.33

20.34

20.35

20.36

20.37

20.38

0 50 100 150

MIMOSA5 corner locationson prototype ladder

bottom corner Ytop corner Y

Y

X

Profile of Chip Elevation on CarrierChip Corner Locations

Flat to ~ 30 m

Accurate to~ 20 m

Measurementsusing OpticalSurvey Machinewith ~ 1 m accuracy.

VTX Ladder Design & TestingVTX Ladder Design & Testing

IR Camera ImageAir Cooling Test

Thin Chips Heating cable

(80mW/cm2)

T(0C)

0

2000

4000

6000

8000

1 104

1.2 104

1.4 104

27 27.5 28 28.5 29

10 deg air = 0 m/s

Cou

nt

microns

Std Deviation = 0.15662692

0

1000

2000

3000

4000

5000

6000

7000

13 15 17 19 21 23 25 27

10 deg air = 1.0 m/s

Cou

nt

microns

Std Deviation = 1.575661SD=0.16 µm SD=1.6 µm

Air=0 m/s Air=1 m/s

• Vibration from air cooling measured with capacitive probe; location distribution with SD~1 m at 1.0 m/s airflow on unsupported end of ladder

• Mechanical and thermal characterization of STAR prototype, study of heat removal using low-speed airflow

Thin CMOS Pixel StudiesThin CMOS Pixel Studies

• Back-thinning of diced chips using grinding process by Aptek Industries• Thinned over 15 MIMOSA5 chips, process reliable down to 40 m, yield of functional chips~90%• Measured chips thickness:

FEA stress analysis offlattened 50 m chip

Surface map of 50 m chip(measured)

“40 m”

“50 m”

Before (550±0.5) m

(50±7) m

(41±6) m

VTX Ladder Design & TestingVTX Ladder Design & Testing

• FEA of prototype structures (core-cooled Si/CF/RVC sandwich, Si/Al/RVC sandwich, CVD coated CF) in progress using data from surveys of 40 and 50 m thin chips, first results promising, test of prototype in 2008

Low density (0.2-0.6g/cc)High thermal conductivity (40-180W/m K) carbon foam

Concept forSymmetric LadderSandwich Support with Air Coolingthrough Core

Ladder side view