X-ray or gamma ray systems or devices – Specific application – Fluorescence
Reexamination Certificate
2000-09-29
2002-06-11
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Fluorescence
C378S044000, C378S045000, C378S070000, C378S071000
Reexamination Certificate
active
06404847
ABSTRACT:
BACKGROUND OF THE INVENTION
1. (Field of the Invention)
The present invention generally relates to an X-ray analysis apparatus whose detector part turns or shuttles to accomplish a continuous scanning.
2. (Description of the Prior Art)
In an X-ray fluorescence spectrometer of a wavelength dispersive type currently widely in use, a sample to be analyzed is irradiated by primary X-rays so that fluorescent X-rays are emitted from the sample. The fluorescent X-rays emitted from the sample are monochromated by a spectroscopic device such as an analyzing crystal, and the resultant, spectroscopically analyzed fluorescent X-rays are then detected by a detector which subsequently outputs pulses. Although the voltage of the pulses outputted from the detector, that is, the pulse height value is proportional to the fluorescent X-ray energy and the number of the output pulses per unitary time is proportional to the intensity of the fluorescent X-rays, of those output pulses the output pulses falling within a fixed range of pulse height values are selected by a pulse height analyzer and the number of those selected output pulses is counted by a scaler. In other words, the count of the selected output pulses is determined by a scaler.
In a scanning type of X-ray spectrometer, the spectroscopic device is scanned linked with the detector so that the wavelength of the monochromated X-rays change. One of the mechanism for the linkage is called as goniometer. Specifically where a qualitative analysis or a semi-quanfitative analysis is performed, the fist speed is required and, therefore, the spectroscopic device and the detector are continuously scanned. In other words, the scanning method is not step scan in which the goniometer is driven a predetermined angle and is then halted for a predetermined time during counting of the output pulses, but continuous scanning in which counting of the output pulses is carried out by continuously driving of the goniometer. At this time, for each fixed scanning interval, for example, {fraction (1/100)} degree of the rotation angle of the detector (so-called 2&thgr;) the scaler reads the count as an intensity for each scanning interval.
The relationship between the scanning range (2&thgr;) of the goniometer and the scanning speed thereof is shown in FIG.
2
. In order for the goniometer to be continuously driven at a desired high speed as shown by ‘b’ in
FIG. 2
, the goniometer has to be driven with accelerated speed as shown by ‘a’ in
FIG. 2
before it is driven to the desired high speed. Also, to halt the goniometer being then driven at the high speed, the goniometer has to be driven with decelerated speed as shown by ‘c’ in FIG.
2
. Accordingly, accurate intensity for each scanning interval can not be obtained in the ranges of accelerated and decelerated speed shown in ‘a’ and ‘c’, because the time required for each {fraction (1/100)} degree varies.
On the other hand, if a method which counting is not performed in the ranges of the accelerated or decelerated speed shown by ‘a’ or ‘c’ is taken for accurate measurement, the analyses at each end can not be done. Also, if as shown by the chain double-dashed line counting is performed while the driving speed of the goniometer is lowered to such an extent that neither acceleration or deceleration is not required, an accurate analysis would be possible at both ends of the scanning range, but at the sacrifice of the speed. Accordingly, rapid and accurate measurement of qualitative analysis or semi-quantitative analysis can not be done over a relatively wide range of wavelength.
In addition, in an X-ray diffractometer for analyzing the crystalline structure of sample, in which a sample support to place of the sample to be analyzed and a detector are linked by the goniometer so that the intensity of diffracted X-rays diffracted by the sample can be measured by varying the incident angle of X-rays irradiated upon the sample, a high precision measurement carried out by the step scan requires a relatively long time. On the other hand, the rapid measurement is possible by the continuous scan. However, accurate measurement is not possible because the counting time is not strictly constant for the fixed scanning interval.
While the foregoing description applies where the detector rotates on the spectroscopic device or the sample by the goniometer to accomplish the continuous scan, problems similar to those discussed above can be found even where a measurement unit including an X-ray source and a detector shuttles on a sample by the continuous scan. For example, in a production line in which while a strip of paper is transported in a direction lengthwise thereof a release agent such as silicone is coated on one surface of the strip of paper to form a strip of release coated paper which is subsequently cut longitudinally (in a direction conforming to the direction of transport) for each or sections divided equally in a widthwise direction thereof which is perpendicular to the longitudinal direction (or for each of continuous sections), to thereby provide a plurality of release coated papers, it is required for the purpose of a quality control of the products (i.e., release coated papers) that the amount of silicone coated is determined for each of the sections.
Accordingly, in the conventional X-ray fluorescence spectrometer designed to suit to the particular purpose discussed above, a measurement unit shuttles by a fixed speed on the sample, which is the strip of the release coated paper before being cut into the sections, in a direction widthwise of the strip of the release coated paper generates for unitary time a number of pulses proportional to the intensity of the fluorescent X-ray emitted from silicon as a result of the sample having been irradiated by a primary X-ray while being transported in the direction lengthwise thereof. Of the pulses generated from the measurement unit, the pulses falling within a predetermined pulse height range are selected by a pulse height analyzer and the number of the selected pulses is determined by a scaler. A calculating means for calculating the amount of silicone coated then determines the amount of silicone coated for each section, based on the measured intensity for each section which is obtained by dividing the number of the pulses generated by the measurement unit by the time required for the measurement unit to move a distance corresponding to one section at the fixed speed. It is here assumed that the moving speed of the measurement unit is constant and the time required for the measurement unit to move the distance corresponding to one section is also constant.
However, it has been found difficult to strictly maintain a constant value the speed at which the measurement unit is moved by the drive means, and the moving speed of the measurement unit varies to a certain extent. Consequently, association of the measured intensity with the particular section and, hence, association of the amount of silicon coated with the particular section tends to depart from each other and, therefore the amount of silicone coated cannot be accurately determined for each section.
SUMMARY OF THE INVENTION
Accordingly, the present invention is intended to provide an improved X-ray analyzing apparatus of a continuous scanning type in which a detector for detecting the intensity of X-rays is turned or shuttled, which apparatus is effective to achieve a rapid and accurate analysis.
To this end, the present invention provides an X-ray fluorescence spectrometer which includes a sample support of a sample to be analyzed; an X-ray source for irradiating the sample with a primary X-ray to excite the sample to emit a fluorescent X-ray thereform; a spectroscopic device for monocromating the fluorescent X-ray emitted from the sample; a detector adapted to receive the fluorescent X-ray, which has been monochromated by the spectroscopic device, and to generate pulses of a voltage proportional to an energy of the fluorescent X-ray in a number proportional to an intensity of the fluorescent X-ray; and a linkag
Fujimoto Hideaki
Kato Toshiyuki
Ueki Bunjiro
Kim Robert H.
Rigaku Industrial Corporation
Sughrue & Mion, PLLC
Thomas Courtney
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