Characterization of a digital radiography

system

Marine Torrollion

Tutor: J-M DALINDUT Physics measures internship to 04/04/11 from

17/06/11

EN/MME/MM departement

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1. The radiographic non-destructive tests at CERN1.1. The radiography laboratory1.2. The material used

2. Description of the digital radiography system2.1. Steps of the radiography acquisition2.2. List of the parameters2.3. Quality of the picture

3. System characterization3.1. Study of the X-Ray beam3.2. Creation of control graphics

Conclusion 2

1. The radiographic non destructive tests at CERN

3Photography of the radiography lab

1.1. The radiography laboratory

A control area : the bunker

Radiography instruments are stored in a closed room with concrete and lead walls and roof:- two X-ray tubes- the X-ray tomograph

Its role at CERN• Perform the control of metallic

pieces

• Material defects, scattered porosity, cracks…

• Accept or reject with respect to reference quality levels

4Photography of the big door of the bunker Examples of weld defects

1.2. Materials usedOrdinary films Phosphor platesSilver films

-single use, price : €8.30 each

-non linear response

-have to be developed with a complex and heavy process which needs chemical products

Cover of phosphor crystals

-can be used 1000 times, possibility to delete the picture in memory, price : €300/unit

-linear response

- can be read directly with a scanner, easy to stock and to be networkaccessible

- are easier to recycle

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Phosphor plates

Silver films

Phosphor plates

Scanner DURR

X-ray Tube PhillipsComputer

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2.1. Steps for the radiography acquisition

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Connection with a USB cable

2.2. List of the parameters

Plate in leadPhosphor plate

Piece containing weld

xX-Ray tubeX-Ray tube

Collimator

ADJUSTABLE PARAMETERSAnode

x * F : distance piece- source

F

* b : distance piece - plate

b * e : piece thickness

e

Potential difference ddp

I

cathode

* ddp : potential difference

* I : size of the source

* T : Time of exposureT

FIX PARAMETRERS

* µ : linear coefficient of attenuation (cm-1) 8

2.3. Quality of the picture

Homogeneity of the radiations

Resolution

Linearity of the absorption

1 mm

IQIs classicals Target with convergent lines

Homogenous plate of aluminum

Graduates wedges

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X-ray

Low intensity High intensity

3. System characterization

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3.1. Study of the X-ray beamObjective : To measure the influence of the piece-source distance on the beam diameter and the radiation intensity.

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The influence of the piece-source distance on the beam diameter

Incertitudes of repetability = corrected standard deviation of the measures

- Function is a straight line: diameter = f(f)

- The diameter grows proportionally with the piece-source distance

- Possibility to check the angle of irradiation with trigonometric calculations12

Comparison of slopes for irradiations angles of 35 and 40 degrees

- The three experimental measures are on the theoretical straight line of

α = 40°

- The provider announces an irradiation angle of 35°

- The outline of the beam is blur13

3.1. Study of the X-ray beamObjective : Measure the influence of the piece-source distance on the beam diameter and the radiation intensity.

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Intensity reading on the beam diameter

- Homogeneous radiations on the beam center- Perturbations of the measures by an important noise- The intensity decreases progressively from the center to the periphery of the beam 15

Intensity handreading on beam’s diameters

- Radiation distribution is similar in the three cases

- Only the intensity changes with the piece-source distance

- 40 % of the beam is homogeneous

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3.2. Creation of control graphics

Radiography series

N° radio

T (s) ddp (kV)

f (mm) pictures

1 45 60 450

2 70 60 450

3 45 70 450

4 45 70 600

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Objective : To allow the operator to achieve a good result at the first manipulation and gain time

Example of a graphic obtained with a copper wedge , f = 450 mm :

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Final presentation of the controls graphic

Controls graphic for copper piece and a piece-source distance of 450 mm at 10 mA

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Conclusion

• Scientific assessment: This work allowed me to check the distribution of the beam radiation, and to create the control graphics for a source of 10 mAThe control graphics allow the operators to obtain a good radiography at a first manipulation.

• Follow-up actions: The creation of control graphics for 4 mA source and a study of the image quality (resolution, contrast, brightness, ...).

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Thanks

Many thanks to Jean-Michel Dalin, my tutor, for his attention and his explanations, As well as to Mr. Sgobba, in charge of the section EN/MME/MM.

Thanks to Aline Piguiet for her assistance during the manipulations.

And finally, a huge thanks to all the section members.

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End of the presentation

Thanks for your attention,

Any questions ?

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