JP5467293B2 - X-ray analyzer - Google Patents

Description

  The present invention relates to an X-ray analyzer having a semiconductor detector for detecting X-rays.

  As detectors for detecting X-rays, semiconductor detectors are used in X-ray analyzers for analyzing samples and radiation CT, X-ray CT, which are radiological medical devices.

  In semiconductor detectors used for radiation CT, X-ray CT, and the like, a change with time in which an output signal decreases during detection occurs, and detection efficiency and resolution decrease. For this reason, there is radiation (X-ray) CT having means for intermittently supplying the bias voltage to the semiconductor detector (see Patent Document 1). In addition, there is a radiation detection apparatus that makes the bias voltage to the semiconductor detector zero or supplies a bias voltage having the opposite sign to the bias voltage at the time of detection (see Patent Document 2).

  In the radiation CT described in Patent Document 1 as a conventional technique, supply of a bias voltage to a semiconductor detector is intermittently synchronized with X-ray irradiation. In the radiation detection apparatus described in Patent Document 2, the bias voltage to the semiconductor detector is set to zero in synchronization with X-ray irradiation, or the bias voltage having the opposite sign to the bias voltage at the time of detection is supplied. The supply of bias voltage is intermittent.

  The semiconductor detector collects the charge generated by the X-rays incident on the p-pole or n-pole of the element of the semiconductor detector by the supplied bias voltage, and amplifies the charge with an amplifier to measure the electric quantity. Yes. However, if a bias voltage is supplied to the element of the semiconductor detector for a long time, ions adhere to the surface of the i layer (intrinsic semiconductor layer) of the element of the semiconductor detector. The charge generated by the X-rays incident on the semiconductor detector is constrained (trapped) in the middle by the adhering ions, and it is considered that there is a difference in charge collection to the p-pole or n-pole due to the electric field by the supplied bias voltage It is done.

For this reason, in a semiconductor detector used in an X-ray analyzer, tailing occurs in which the bottom of a spectrum profile obtained by measurement has a long tail when used for a long period of six months or more. Especially tailing to the low energy side. In addition, the background of the output signal is increased. In particular, a large background appears on the low energy side. For this reason, the sensitivity of analysis may be reduced, or incorrect identification may be made in qualitative analysis.
JP-A-6-121793 JP 2004-125524 A

  In the radiation CT described in Patent Document 1 and the radiation detection apparatus described in Patent Document 2, in order to solve the problem of the temporal degradation of the output signal in a short time during X-ray detection, it is synchronized with X-ray irradiation. Thus, the supply of the bias voltage to the semiconductor detector is made zero, or the supply of the bias voltage is interrupted by supplying a bias voltage having the opposite sign to the bias voltage at the time of detection. However, in the X-ray analyzer, a tailing phenomenon that occurs after a long period of use is a problem, and a cutting time is required to sufficiently discharge ions attached to the i layer surface of the element of the semiconductor detector from the i layer. Further, immediately after supplying a bias voltage to the semiconductor detector, the dead rate (dead time ratio) of the semiconductor detector is high, the peak position of the spectrum profile becomes unstable, and measurement cannot be started immediately. Therefore, the X-ray analyzer cannot perform measurement by intermittently supplying the bias voltage.

  The present invention has been made in view of the above-described conventional problems. By cutting the bias voltage supplied to the semiconductor detector according to a predetermined schedule, the tailing of the spectrum profile is suppressed, the background is reduced, An object is to provide an X-ray analyzer capable of analyzing with high sensitivity and high accuracy.

  In order to achieve the above object, an X-ray analyzer of the present invention includes a semiconductor detector for detecting the intensity of secondary X-rays generated from a sample irradiated with primary X-rays by an X-ray tube, and the semiconductor detection device. A bias power source for supplying a bias voltage to the detector, and a control device for controlling the bias power source and cutting the bias voltage supplied to the semiconductor detector according to a predetermined schedule.

  According to the X-ray analyzer of the present invention, since the bias voltage supplied to the semiconductor detector is cut according to a predetermined schedule without being interrupted, the tailing of the spectrum profile is suppressed, the background is reduced, and the sensitivity is high. Can be analyzed with high accuracy. In addition, the life of the semiconductor detector can be extended.

  The X-ray analyzer of the present invention preferably warms up the semiconductor detector by making X-rays incident before the first measurement after the bias voltage is cut off. In this case, after the bias voltage is cut off and before the first measurement, X-rays are incident to warm up and then the measurement of the sample is started, so that the semiconductor detector can be measured in a stable state. It is possible to analyze with high sensitivity and high accuracy.

  Hereinafter, a total reflection X-ray fluorescence analyzer which is an embodiment of the present invention will be described. As shown in FIG. 1, the total reflection X-ray fluorescence spectrometer 1 of the present embodiment is generated from an X-ray source 10 that irradiates a sample S with primary X-rays 14 and a sample S that is irradiated by the X-ray source 10. A semiconductor detector 16 that detects fluorescent X-rays 15 that are secondary X-rays, a bias power source 17 that supplies a bias voltage to the SSD, and a bias voltage that is supplied to the semiconductor detector 16 by controlling the bias power source 17. And a control device 20 for cutting according to a predetermined schedule. The control device 20 manages the operation date and time of the total reflection X-ray fluorescence spectrometer 1, controls the X-ray source 10, the semiconductor detector 16, and the bias power supply 17, and warms up the semiconductor detector 16.

  The X-ray source 10 is composed of an X-ray tube 11 and a spectroscopic element 13, and the X-ray 12 emitted from the X-ray tube 11 is monochromatized by the spectroscopic element 13 and irradiated to the sample S as primary X-rays 14. . The angle at which the primary X-ray 14 irradiated by the X-ray source 10 onto the sample S is totally reflected on the upper surface of the sample S, for example, 0.05 to 0.2 ° is set. The semiconductor detector 16 that detects the fluorescent X-rays 15 from the sample S is, for example, an SSD. The bias power supply 17 supplies a bias voltage to the semiconductor detector 16. The control device 20 cuts or supplies the bias voltage supplied to the semiconductor detector according to a predetermined schedule. Further, the X-ray source 10 and the semiconductor detector 16 are controlled so that the fluorescent X-rays 15 from the sample S are incident on the semiconductor detector 16 to warm up the semiconductor detector 16. The time for which X-rays are incident on the semiconductor detector 16 for warming up is preferably about several seconds to 10 seconds. The control device 20 is configured by a computer.

  The cutting schedule of the bias voltage supplied to the semiconductor detector 16 is preferably set at a time when the total reflection X-ray fluorescence spectrometer 1 does not perform measurement. For example, a schedule is set in which the bias voltage is continuously disconnected for a predetermined time every day at 4 am on the day of the week, the supply of the bias voltage is resumed, and a standby state in which measurement is not started is continued for a predetermined time.

  By continuing to cut the bias voltage for a predetermined time, ions attached to the surface of the i layer of the semiconductor detector element are discharged from the surface of the i layer, and the charges generated by the incident X-rays are not trapped. The charge collection returns to a good state. Thereby, tailing of the spectrum profile measured by the total reflection X-ray fluorescence analyzer 1 is suppressed, and the background is reduced. The cutting duration of the bias voltage is preferably 5 to 20 minutes, and more preferably 10 to 15 minutes.

  Immediately after the supply of the bias voltage, the dead rate of the semiconductor detector 16 is high and the peak position of the spectrum profile is unstable. Therefore, after the supply of the bias voltage is resumed, the measurement device waits for a predetermined time without starting measurement. That is, by measuring after the dead time of the semiconductor detector 16 elapses, accurate and accurate measurement can be performed. The waiting time before measurement after resumption of supply of the bias voltage is preferably 2 to 15 minutes, and more preferably 3 to 10 minutes.

  The control device 20 controls the X-ray source 10 and the semiconductor detector 16 and warms up the X-ray 15 from the sample S on the semiconductor detector 16 before the first measurement after the bias voltage is cut off. To do. By warming up, the sample S can be measured while the semiconductor detector 16 is stable.

  The operation of the total reflection X-ray fluorescence spectrometer 1 according to the embodiment of the present invention will be described with reference to the operation flowchart of FIG. Normally, the main power supply of the total reflection X-ray fluorescence spectrometer 1 is always turned on, the measurement can be started at any time, and the operation date and time is managed by the control device 20. Further, the X-ray source 10, the semiconductor detector 16, and the bias power source 17 are controlled by the control device 20 so as to operate as follows.

  In step S1, it is determined whether or not the date and time when bias voltage disconnection is set. If it is not the date and time, the process returns to step S1.

  If it is, the process proceeds to step S2, and it is determined whether or not the total reflection X-ray fluorescence spectrometer 1 is measuring.

  If the measurement is being performed in step S2, the process proceeds to step S2A, and it is determined whether or not standby during measurement has been executed. If the waiting during measurement is not executed, in step S1A, for example, 4 hours is waited. When the standby for 4 hours is completed, it is determined in step S2 whether the measurement is in progress.

  If standby during measurement is executed in step S2A, the current bias voltage disconnection setting is canceled in step S3.

  If the measurement is not being performed in step S2, the process proceeds to step S4, where the bias power source 17 is controlled to cut the bias voltage, for example, for 15 minutes. At this time, the control device 20 stores the execution of the cutting of the bias voltage. When the cutting of the bias voltage for 15 minutes is completed, the process proceeds to step S5.

  In step S5, the bias power supply 17 is controlled to start supplying the bias voltage.

  In step S6, the pre-measurement standby without starting the measurement is performed, for example, for 10 minutes.

  In step S7, the reserved measurement already set from the control device 20 is read, or new analysis conditions are set in the control device 20. New analysis conditions may be set in steps S4-6. Note that the measurement step after step S7 may proceed immediately after the end of step S6, or once the operation of the total reflection X-ray fluorescence spectrometer 1 is finished once in step S6, and then, for example, several hours later, It may proceed after days.

  When measurement is started in step S8, the process proceeds to step S9.

  In step S9, the control device 20 determines whether or not this measurement is the first measurement after execution of the cutting of the bias voltage stored in step S4. In the case of the first measurement, the process proceeds to step S10. At this time, the memory for cutting the bias voltage stored in step S4 is erased from the controller 20. If it is not the first measurement, the process proceeds to step S11.

  In step S10, the X-ray source 10 and the semiconductor detector 16 are controlled to irradiate the sample S with the primary X-rays 14, and the fluorescent X-rays 15 generated from the sample S are incident for 5 seconds, for example, to detect the semiconductor detector 16. To warm up. When the warm-up of the semiconductor detector 16 is completed, the process proceeds to step S11. If the measurement is started in steps S4 to S10, the measurement is in a standby state until the warm-up of the semiconductor detector 16 in step S10 is completed, and the process proceeds to step S11 after the completion of step S10.

  In step S11, the sample X is irradiated with the primary X-ray 14 and the intensity of the fluorescent X-ray 15 generated from the sample S is measured by the semiconductor detector 16 to determine the quantitative value of the measurement element.

  When the measurement of all the samples is completed in step S12, the process ends.

  According to the total reflection X-ray fluorescence spectrometer 1 of the present embodiment, the bias voltage is cut according to a predetermined schedule, so that tailing of the spectrum profile is suppressed, the background is reduced, and analysis is performed with high sensitivity and high accuracy. be able to. Thereby, the semiconductor detector 16 can be used stably for a long time.

  In the present embodiment, the total reflection X-ray fluorescence analyzer 1 has been described, but an X-ray analyzer such as a fluorescent X-ray analyzer or an X-ray diffractometer having another semiconductor detector 16 may be used. The bias voltage disconnection schedule is set to the day of the week, but may be set as necessary, such as daily or monthly. Although the fluorescent X-rays 15 are used for warming up the semiconductor detector 16, X-rays such as primary X-rays from the X-ray tube 10 and scattered X-rays from the sample S may be used.

1 is a schematic view of a total reflection X-ray fluorescence spectrometer that is an embodiment of the present invention. It is an operation | movement flowchart of the same apparatus.

Explanation of symbols

1 X-ray analyzer (total reflection X-ray fluorescence analyzer)
11 X-ray tube 12 X-ray 13 Spectroscopic element 14 Primary X-ray 15 Secondary X-ray (fluorescent X-ray)
16 Semiconductor detector 17 Bias power supply 20 Control device S Sample

Claims (2)

A semiconductor detector for detecting the intensity of secondary X-rays generated from a sample irradiated with primary X-rays by an X-ray tube;
A bias power supply for supplying a bias voltage to the semiconductor detector;
A control device for controlling the bias power source and cutting the bias voltage supplied to the semiconductor detector according to a set date and time ;
X-ray analyzer equipped with. In claim 1,
The controller controls the X-ray tube and the semiconductor detector to warm up the semiconductor detector by injecting fluorescent X-rays from a sample before the first measurement after the bias voltage is cut off. X-ray analyzer.

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