x-rays see allcalypso 2 –preparation measurement program 3 –use of specific calypso algorithms...

X-rays see allX-ray computed microtomography (µCT) – a novel technique available at CERN for material and metrological inspection

Mariusz Jedrychowski EN/MME-MM

Introduction of new technique at CERN

16/05/2018

Article on CERN Bulletin

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12/12/2017

Shipment of Zeiss Metrotom CT 1500 to Bdg. 100.The lead-shielded closed-cabinet system came assembled in a 8100

kg truck pallet.

Open Day – 6th June 2018

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What we can see with X-rays?

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An x-ray radiograph of A Misereuse Accroupie

Photography by Craig Boyko/Art Gallery of Ontario

Wilhelm Roentgen

What we can see with X-rays?

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Molibden-Graphite prototype collimation

material for HL-LHC

(WP5-Collimation – ARIES)

Brazing inspectionHigh X-ray

absorption

inclusions

Voids / filling

imperfections

Electric circuit

µCT – outstanding possibility to see and analyse in 3D

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Inclusion analysis for Mo-Gr samples

µCT – outstanding possibility to see in 3D

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Superconducting cable for ITER project

Voltage: 225 kV,

Distance: 160 mm

Voxel size: 50 µm,

Projections: 2000,

Integration time: 2 s,

Measurement time:

2.5 h

Top

ViewFront View

µCT – outstanding possibility to see in 3D

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Superconducting cable for ITER project

µCT – outstanding possibility to see in 3D

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Superconducting cable for ITER project

µCT – outstanding possibility to see in 3D

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CLIC Spiral Load – 3D

printed titanium object

Voltage: 220 kV,

Distance: 750 mm,

Voxel size: 111 µm,

Projections: 2050,

Integration time:

1000 ms,

Measurement time:

1.5 h

Overview

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1. X-ray computed tomography

• Short introduction

• Possibilities: NDT, metrology

2. Zeiss Metrotom CT – specification

3. Software

4. Applications gallery

5. “X-rays see all”. How far we can see with µCT in practice ?

6. Image processing techniques developed at CERN

X-ray computed (micro)tomography - µCT

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Rotary table

Flat image detector

high-resolution: 2048 x 2048 pixels

X-ray tube determines

the range of applications:

• a smaller focal spot is used

for high resolution,

• a higher voltage is used for

more absorbent

(denser/thicker) pieces

Tube/detector distance

determines the available measuring range:

Piece

Regions with different

X-ray absorption

Projections

2D radiography

Precision axes

The workpiece can be moved on four axes with

extreme precision provided by coordinate measuring

technology which, in result, allows metrology

measurements.

X-ray computed (micro)tomography - µCT

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30 cm

X-ray computed (micro)tomography - µCT

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3D reconstruction3D set of grey level voxels

Projections

2D radiography

22.5º

Zeiss Metrotom CT

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Detector

Sample holder

– Rotary table

X-ray generator

Zeiss Metrotom CT

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Specification

• Microfocus X-ray tube:

Max. voltage 225 kV

Max. current 3000 µA

Max power 500 W

Min. focal spot size 7 µm

• High resolution flat panel imager:

40 x 40 cm

2048 x 2048 pixels, 16 bit

• Tube-detector distance: 1375 mm

• Max. spatial resolution: 4 μm

Inoptimum conditions: small piece

and contrasting materials.

Typically voxel size is 10 to 100 μm

• Length measurement error [µm]:

9 μm + L/50

Max through thickness

Material Max. through

thickness [mm]

Polymer > 300

Aluminium 300

Titanium 200

Steel 50

Copper 20 - 30

Sample size vs voxel size – extended field of view

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Carbon piece for ALICE detector

Horizontal and vertical

extensions used,

5 scans merged, Voltage: 190 kV,

Distance: 437 mm,

Voxel size: 65 µm,

time: 6.5 h

CT data size: 112 GB

Projection: 80° Surface mesh

70 cm

Analysis possibilities provided by CT data

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Obtained CT data are stored in form of 3D lattice of voxels that allows a wide

range of analyses to be performed:

1. 2D Cross-sections

2. 3D Qualitative visualization

3. Separation of different parts in a sample - grey level value segmentation

4. Particle analysis (size, position and shape descriptors)

5. Weld assessment

6. Surface mesh extraction

7. Wall thickness

8. Advanced applications: classification, quality control, corrections for

additive manufacturing settings, metrology measurements, FEM

simulations based on CT data

Software

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NDT Applications – qualitative observations

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Copper micro Nozzle

Voltage: 220 kV,

Distance: 165 mm,

Voxel size: 26 µm,

Projections: 1750

Image avg.: 3 images

Measurement time: 3 h

3D volume with clipping plane

3 cm

Beam hardening

NDT Applications – qualitative observations

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Voltage: 225 kV,

Distance: 470 mm,

Voxel size: 70 µm,

Projections: 3000,

Measurement time: 2 h 3D volume – side view

11 T magnet coil

80 cm

NDT Applications – qualitative observations

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Connector in cryogenic instrumentation for LHC

Voltage: 220 kV, Distance: 90 mm, Voxel size: 15 µm, Projections: 2050, Measurement time: 2.5h

1.5 cm

NDT Applications – electronics

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Electronic component for ATLAS Forward Proton Detector

Shorts ground-high voltage cable due to air bubbles found inside ATLAS ChipAim: to understand issues related with IC

packaging problem

Voltage: 215 kV, Distance: 55 mm , Voxel size: 9.64 µm,

Projections: 2050, Integration time: 2 s, Measurement

time: 2.5 h

3D volume and Top View cross-section

Voltage: 220 kV, Scan time: 1 h 10 min, Voxel size: 23 µm

1 cm

2.5 cm

NDT Applications – Porosity/Inclusion analysis

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Inclusion analysis for Mo-Gr samples

Porosity in brazed layers

of NA62 connector

1.5 cm

NDT Applications – Porosity analysis

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Copper brazed with steel

Test piece

identification

Filling

%

Conformity with

EN ISO 18279

quality level C

Unrolled brazing surface

1 >90% YES

2 >95% YES

3 >90% YES

4 >90% YES

5 >85% YES

6 90% YES

brazed connections for R2E-LHC2.5 cm

NDT Applications – Wall thickness analysis

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90 cm

Analysis of wall

thickness of ALICE

aluminium tubular

segments

NDT Applications – quantitative observations

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Voltage: 220 kV, Distance: 150 mm, Voxel size: 23 µm,

Projections: 2050, Integration time: 2000 ms, Measurement time: 2.5 h

PCB with socket

Aim: to understand issues

related with loosen connection

between socket and plug

Comparison: bad vs good socket

NDT Applications – quantitative observations

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CLIC Spiral Load

Surface rendering

Voltage: 220 kV,

Distance: 750 mm,

Voxel size: 111 µm,

Projections: 2050,

Integration time:

1000 ms,

Measurement time:

1.5 h

Metrology Applications

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1 – Importation of tomographic data on

Calypso

2 – Preparation measurement program

3 – Use of specific Calypso algorithms such as

Curve, Freeform for surface measurements of

Freeform shapes (impossible on VG Studio)

4 – Same program than CMM: possibility to

pass from CT to CMM for the same part

Metrology Applications

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CLIC Spiral Load Nominal-Actual Comparison

Applications - metrology

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Voltage: 215 kV, Distance: 55 mm, Voxel size: 9.64 µm, Projections: 1600

Image avg.: off, Integration time: 2000 ms, Measurement time: 1 h

Projection: 90° 3D volume with

clipping plane

2D cross-section

Titanium printed spring with Zirconia sphereAim: Metrology measurements in order to quantify sphericity and roundness of the interface between

sphere and spring

0.5 cm

Applications - metrology

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Aim: Metrology measurements for machining purpose – estimation of thickness to be removed

Titanium printed serpentine

3 scans merged

Voltage: 215 kV,

Distance: 186 mm,

Voxel size: 28.64 µm,

Measurement time: 4 h

3D volume with clipping plane

12 cm

Voxel size (Resolution)

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What is the voxel size for my sample ?

It depends on:

1. magnification (x position) / sample size

2. beam intensity / Image Contrast / Image Quality

focal spot size (micro focus – nano focus X-ray tube)

beam filtration

3. sample orientation

acquisition time and data size

resolution vs detectability

1. Magnification / voxel size

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Tube/piece/detector distances

magnification M = D/x

X - ray

tubeDetector

Object

D = 1375 mm

x

voxel_size [µm] = 410/1375 * x [µm] /2048 = 0.145 * x [mm]

410

Top View

W

A cube defined by W x W x W is considered

W = 2048 * voxel_size

W / x = 410 mm / D (from Thales relation)

(assuming that detector area is fully filled in by object projection)

1. Magnification – voxel size vs sample size

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Distance [mm]

50 70 140 280 550 700

Voxel size [µm] 7 10 20 40 80 100

W [mm]

(“Sample size”)14 20 40 80 160 200

Magnification 28 20 10 5 2.5 2

But this is the best case. In practice sample is not perfectly aligned with detector center/plane. Also, because of

maximum thickness to be passed through by X-rays (tilted orientation).

Hence, it has to be placed further away from the X-ray tube in order to decrease magnification (fit inside

projection frame)

2. Influence of focal spot size

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Point

Source

Small

Focal Spot

Large

Focal Spot

Object

Image

Detector

penumbra

Focal spot size has to be adjusted in respect to object size in order to avoid blurred projections

2. Effect of focal spot size – blurred projections

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2. Spot size – blurred projections

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Spot size = 90 µm

Current = 500 µA

Voltage = 180 kV

Magnification = 65

2. Spot size – blurred projections

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Spot size = 36 µm

Current = 200 µA

Voltage = 180 kV

Magnification = 65

2. Spot size – sharp projections

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Spot size = 7 µm

Current = 50 µA

Voltage = 180 kV

Magnification = 65

2. Spot size – reconstructed thin tungsten wire

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Spot size = 7 µm Spot size = 46 µm

voxel size

9.3 µm

3. Beam intensity – why beam has to be filtered?

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Beam hardening (BH) artefact Main reason of BH

Uncorrected BH

Corrected BH

3. Beam intensity – why beam has to be filtered?

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Theoretical energy spectra for 420-kV X-ray source with

tungsten target, calculated combining 5-keV intervals.

Spectra consist of continuous Bremsstrahlung and

characteristic K-series peaks at 57–59 and 67–69 keV.

R.A. Ketcham, W.D. Carlson / Computers & Geosciences

27 (2001) 381–400

3. Beam intensity – Filtering of Energy distribution

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No filter, 220 kV, 400 µA, spot size = 88 µm

Cu = 2 mm, 220 kV, 400 µA, spot size = 88 µm

No filter, 180 kV, 490 µA, spot size = 88 µm

Cu = 2 mm, 180 kV, 490 µA, spot size = 88 µm

3. Beam intensity – how it can be increased

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We take advantage of detector capabilities in order to increase signal registered

Solution Consequence

• Longer integration time => Longer acquisition

• Higher gain (signal amplification) => increased noise

• Binning 2 x 2 => reduced CT voxel size

(increased detector pixel size, 1024 x 1024 px instead of 2048 x 2048 px)

3. Beam intensity – [Gain = 16, Integration time = 2 s]

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Cu = 2.5 mm, 220 kV, 488 µA, spot size = 70 µA

Cu = 2.5 mm, 220 kV, 45 µA, spot size = 7 µA

Contrast = Max Intensity – Min Intensity

4. Sample orientation – Feldkamp reconstruction artefact

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electronic components in power amplifiers

for LIU-SPS project

Sample orientation – Feldkamp reconstruction artefact

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Sample orientation – Feldkamp reconstruction artefact

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4. Sample orientation – Feldkamp reconstruction artefact

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Developed Applications – Pore segmentation algorithms

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Several image

processing methods

were developed in

order to estimate

porosity of brazing

Developed

algorithm

Standard

approach

Final result

Developed Applications – CT vs Ultrasound inspection

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A method was developed in order to compare porosity estimation obtained

from µCT measurements and ultrasound inspection

Voltage: 215 kV,

Distance: 90 mm,

Voxel size: 15 µm,

Projections: 1600,

Measurement time: 2 h

Defects found by UT (red areas on the left) and CT (dark areas on the right)

Developed Applications – X-ray radioscopy

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Chip0FF - 1840

Chip1FF - 1840

Chip2FF - 1840

Chip3FF - 1840

Chip4FF - 1840

Chip5FF - 1840

Chip6FF - 1840

Chip7FF - 1840

Chip8FF - 1840

Chip9FF - 1840

Sphere diameter < 20 µm !

Developed Applications – X-ray radioscopy

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A Flat Field algorithm was developed at CERN in order to perform manual X-ray

radioscopy using Zeiss Metrotom CT

– standard scan mode imposes sample rotation which limits resolution in the case of a flat sample.

Corrected Image = (Raw_Projection – Dark_Frame)/(Bright_Frame – Dark_Frame)

RAW projection Bright Frame (Gain) Dark Frame (no beam) Corrected projection

Developed Applications – X-ray radioscopy

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Width = 15 cm

Summary

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1. NDT

New possibilities to analyse quantitatively and qualitatively internal structure of materials

2. METROLOGY

• Complementary to CMM and other measurement means

• Good accuracy for many parts

3. Custom Algorithms and image processing methods were developed. One of them will be presented at the iCT Conference 2019 in Padova

Thank you for your attention!

Developed Applications – Pore segmentation algorithms

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Several image processing methods were developed in order to estimate porosity of brazing

Binary

cleaningAuto local

threshold

Noise

reductionCLAHEStandard

threshold Final result

Applications - metrology

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Aim: 1. Comparison of 3D printed sample with CAD model used for printing.

2. Estimation of surface thickness removed during following polishing

Titanium sample 3D printed and polished (designed for crab cavity)

Voltage: 220 kV

Distance: 755 mm

Voxel size: 112 µm

Projections: 2200

Image avg.: 3 images

Integration time: 1 s

Measurement time: 2 h

Projection: 90°Nominal/actual comparison

with CAD model

3D volume with

clipping plane