X-ray High Resolution Imaging CCD Camera
Based On a Thin Scintillator Screen
J. Touš, K. Blažek, Crytur Ltd. Turnov, Czech Republic
L. Pína, Reflex Ltd. Prague, Czech Republic
B. Sopko, CVUT FME Prague, Czech Republic

Abstract

A high-resolution imaging X-ray CCD camera based on YAG:Ce or LuAG:Ce scintillating screens ispresented. The obtained spatial resolution of X-ray images is in order of micrometers. The high resolution
is proved on several objects and compared to the resolution of a standard P43 (Gd2O2S:Tb) powderscintillator screen.

The high resolution imaging system is a combination of a high sensitive digital CCD camera and an optical system with a thin
scintillator screen. The screen is the YAG:Ce (Y3Al5O12) or the LuAG:Ce (Lu3Al5O12) inorganic scintillator. These materials have theadvantages in the mechanical and chemical stability, non-hygroscopicity, and a high radiation hardness.

Experiment

Experimental setup

The experimental setup consists of a 40kV
X-ray microfocus source and a high resolution
CCD camera with an optical system.
Objects are in a very close position to thescintillation screen. It is then possible to takeX-ray images with the resolution better than
10 micrometers by combination of the thinscreen and the high resolution CCD detector.

High-resolution X-ray digital camera

Thin YAG:Ce screen

The high resolution imaging screen is the basic part of thehigh-resolution imaging system. The very thin imaging
screens are based on the YAG:Ce or the LuAG:Ce single
crystal scintillation material.

P43 phosphor screen

Phosphor powder

An optimal thickness of the screen is a compromise between the detection efficiency and the highresolution. The very thin screen on a precise optical substrate is imaged by an optical system with thePeltier cooled CCD detector. The P43 screen is made from powder of 2-4 micrometers particle size.Thethickness of the layer is about 20 micrometers.

Experiment results
The imaging system was tested on several objects. The high resolution of the system withYAG:Ce thin screen is compared to a standard P43 phosphor screen using the same conditions.
The objects are an edge of 100 micrometers thick iron plate and a gold grid with the wires 8microns wide. The images were taken by using the 20 micrometers thick YAG:Ce imagingscreen or 20 microns thick phosphor P43 (GADOX), both on quartz glass. An acquisition time forboth screens is different due to different detection efficiency of the materials.

The edge fitted by a distribution function,
image taken using P43 screen

The image of the edge taken
by using the P43 screen

The edge fitted by a distribution function,
image taken using YAG:Ce screen

The images of the edge were inspected by a line profile. The transverse cut of the image of the edge is fitted by an error
distribution function (erf). The sigma means the edge width. The resolution of the YAG:Ce screen is then about 4.4
micrometers and the resolution of P43 screen is about 16.2 micrometers in the low energy X-ray radiation.
The image of the testing golden grid taken by using the P43 screen shows that the wires cannot be resolved. The width of
the wires on the image taken by using the YAG:Ce screen is about 14 pixels. The effective pixel size is 0.74 micrometers.
The high resolution images of biological objects show a termite and a tick imaged by using the high resolution system.

The image of the edge taken byusing the thin YAG:Ce Screen

The tick a detail

SEM image of the meshConclusions

The image of the mesh taken by using thethin YAG:Ce Screen

The image of the mesh taken by using theP43 phosphor screen

A termite

A tick

The results

High resolution depends on

Advantages

Application- the resolution obtained by means ofthe thin single crystal imaging
screen is higher than the resolutionof the standard P43 screen- minimal thickness of the plate- excellent parallelism of faces- high optical quality- space homogeneity of luminescence- optical coating- long life operation- high resolution better
than 10 microns (up to 1 micron)- X-ray, electron and UV
detection- industry and science- defects inspection- biological imaging- technical imaging- X-rays, electrons and UVCrytur Ltd., Palackého 175,
511 01, Turnov
Czech Republic

Phone: +420 481 319 511
FAX: +420 481 322 323
E-mail: crytur@crytur.cz
http://www.crytur.com

Acknowledgement
This research has been supported by Czech Ministryof Industry and Trade Project No.: FT-TA/100