JP2009276191A - X-ray analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain high energy resolution eliminating a need for monitoring known X-ray in an X-ray analyzer. <P>SOLUTION: This analyzer includes: a sensor circuit part 2 having a TES 1 which receives X-ray and detects its energy as the change in temperature to output it as current signal; a bias current source 3 applying constant voltage on the sensor circuit part 2 to carry bias current; a current detecting mechanism 4 detecting the current flowing in the TES 1; a wave height analyzer 5 connected with the current detecting mechanism 4 measuring the wave height value based on the detected current; a baseline monitoring mechanism 6 connected with the current detecting mechanism 4, detecting the baseline current flowing in the TES 1 with the bias current; and a bias current adjusting mechanism 7 adjusting the bias current to modify the baseline current according to the variation width even when the baseline current detected by the baseline monitor mechanism 6 shifts and varies from the predetermined value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is an X-ray analyzer used for an electron microscope, a fluorescent X-ray analyzer, etc., for identifying the element type of a generation source by discriminating the energy of generated X-rays, and particularly for X-ray analysis. The present invention relates to an X-ray analyzer using a superconducting transition edge sensor that converts energy into thermal energy as an X-ray detector.

As an X-ray analysis apparatus capable of discriminating X-ray energy, there are an energy dispersive X-ray detector (Energy Dispersive Spectroscopy, hereinafter referred to as EDS) and WDS (Wavelength Dispersive Spectroscopy, hereinafter referred to as WDS).
The EDS is a type of X-ray detector that converts X-ray energy taken into the detector into an electric signal in the detector and calculates the energy based on the magnitude of the electric signal. The WDS is a type of X-ray detector that monochromatizes X-rays with a spectrometer (energy discrimination) and detects the monochromated X-rays with a proportional counter.

  As EDS, a semiconductor detector such as a SiLi (silicon lithium) type detector is known. By using this semiconductor detector, a wide range of energy of about 0 to 20 keV can be detected, but the energy resolution is as narrow as about 130 eV, which is inferior to 10 times or more as compared with WDS.

  Thus, there is energy resolution as an index indicating the performance of the X-ray detector. For example, when the energy resolution is 130 eV, when the X-ray detector is irradiated with X-rays, it means that detection is possible with an uncertainty of about 130 eV. Here, high energy resolution means reducing this uncertainty. For example, consider the case of two spectra with adjacent characteristic X-rays. When the energy resolution is reduced, the uncertainty is reduced. When two adjacent peaks are, for example, about 20 eV, the two peaks can be separated in principle with an energy resolution of 20 eV to 30 eV.

  In recent years, superconducting X-ray detectors that are energy dispersive and have an energy resolution equivalent to that of WDS have attracted attention. Among these superconducting X-ray detectors, a detector called a superconducting transition sensor (hereinafter referred to as TES) is a rapid resistance change (ΔT to several It is a highly sensitive thermometer using ΔR to 0.1Ω at mK. This TES is also called a microcalorimeter.

  In this TES, radiation such as primary X-rays or primary electron beams from a radiation source is irradiated onto a sample, and fluorescent X-rays or characteristic X-rays generated from the sample are incident, thereby changing the temperature in the TES and changing the temperature. The peak value of the current signal generated by the above is monitored, and the sample value is analyzed by converting the peak value into energy and creating a histogram. At present, the energy resolution of TES can obtain an energy resolution of 10 eV or less in a characteristic X-ray of 5.9 keV, for example.

  When TES is attached to a thermal scanning electron microscope (such as a tungsten filament type) using an electron generation source, characteristic X-rays generated from a sample irradiated with an electron beam are acquired. TES can easily separate characteristic X-rays (Si-Ka, W-Ma, b) that cannot be separated.

  In an X-ray analysis apparatus employing this superconducting X-ray detector, a SQUID amplifier (Superducting Quantum Interference Device (superconducting quantum interference element) amplifier) is used to read out a very small change in TES current. In order to realize the high energy resolution of TES, it is important to make the current flowing through the SQUID amplifier constant. This point will be described in detail below.

  In TES, the superconducting transition of a superconductor is used, and the operating point is maintained in an intermediate state between normal and superconducting. For this reason, when one X-ray is absorbed by TES, a resistance change of several mW is obtained for a temperature fluctuation of 0.1 mK, for example, in a state where the operating point is maintained during the superconducting transition, and the microampere An order X-ray pulse signal can be obtained.

By obtaining the relationship between the peak value of the X-ray pulse signal and the energy of the X-ray in advance, the X-ray energy incident from the peak value can be detected even if the TES is irradiated with X-rays having unknown energy. it can.
In order to keep the TES at the operating point during the superconducting transition, the operating point of the TES is determined by the thermal balance between the current flowing in the TES (hereinafter referred to as the TES current) and the heat link to the heat bath provided in the TES. It is determined. Since the energy resolution of TES is a function of temperature, the temperature should be as low as possible. Generally, the heat bath temperature is about 50 mK to 400 mK. The TES current It is determined by the following equation (1).

Here, Rt is the operating resistance of the TES, G is the thermal conductivity of the thermal link for thermally connecting the thermometer and the thermal bath provided in the TES, T is the temperature of the thermometer, and Tb is the thermal bath Temperature.
Further, the relationship between the TES current It and the peak value is given by the following equation (2). Ideally, if the TES current is constant, a constant peak value ΔI is always obtained.

Here, α is the sensitivity of TES, C is the heat capacity, and E is the energy of the irradiated X-rays.
As can be seen from this equation (2), when the TES current is changed, the peak value is different even when the TES is irradiated with the X-rays having the same energy.

  Next, FIG. 6 shows the relationship between the output value after filtering and the current flowing through the SQUID amplifier (same as the TES current It) with respect to the peak value when the bias current applied to the TES is changed from 280 mA to 320 mA. As shown in this figure, the TES current increases as the peak value increases according to the above equation (2) (right axis). As the peak value, for example, a numerical value (hereinafter referred to as numerical value 1) convolved with a band filter is output to the personal computer.

At this time, the spectrum display screen on the display of the personal computer is displayed with the horizontal axis: numerical value 1 and the vertical axis: count. For example, when the numerical value 1 is 100, one is counted at 100 locations. By repeating this, an X-ray spectrum is formed.
This means that the numerical value 1 varies when the output value after filtering changes despite the same energy. This degree of variation corresponds to the energy resolution described above. That is, in order to realize high energy resolution, the variation of the numerical value 1 must be reduced for the same energy.

The variation of the numerical value 1 is caused by the variation of the crest value, that is, the change in the current flowing through the SQUID amplifier. That is, in order to realize high energy resolution, it is important to make the current flowing through the SQUID amplifier constant as described above.
As a method for making the output of the SQUID amplifier constant, for example, there is a technique described in Patent Document 1 conventionally. In this technique, since the TES current depends on the operating resistance of the TES, a heat adding device is provided as a recovery mechanism for recovering the resistance value of the TES. When the operating resistance of the TES changes, the resistance value Is restored, and the peak value is kept constant to achieve high energy resolution. That is, since the TES is driven with a constant voltage, keeping the resistance value of the TES constant is the same as keeping the current flowing through the SQUID constant.

JP 2008-14775 A

The following problems remain in the conventional technology.
In the conventional X-ray analyzer, X-rays with known energy are always monitored, and the TES resistance is recovered from the change in the peak value. However, it is sufficient to always irradiate the TES with constant X-rays, but there are the following disadvantages. For example, when an electron beam is used as an X-ray excitation source to irradiate a sample with an electron beam and composition analysis is performed using characteristic X-rays generated therefrom, the energy of the characteristic X-ray differs depending on the irradiation location of the electron beam. It is necessary to adjust the characteristic X-ray to be monitored for each irradiation place. For example, when a multipoint analysis is performed with an analysis time of 30 sec, the analysis slew rate is halved if an adjustment time of 30 sec is required at each location. In order to avoid this point, it is possible to provide an X-ray source and irradiate X-rays with a constant energy. However, a space for spatial arrangement in the system is required, and from the X-ray source. Since X-rays inherent to the X-ray source are always detected, there is a disadvantage that X-rays having the same energy as the X-ray source cannot be analyzed accurately.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an X-ray analyzer that can obtain high energy resolution without the need to monitor known X-rays.

  The present invention employs the following configuration in order to solve the above problems. That is, the X-ray analyzer of the present invention receives a X-ray, detects its energy as a temperature change, outputs a current signal, and applies a constant voltage to the sensor circuit unit. A bias current source for flowing a bias current, a current detection mechanism for detecting a current flowing in the superconducting transition edge sensor, and a pulse height analyzer for measuring a peak value based on the detected current connected to the current detection mechanism A baseline monitor mechanism connected to the current detection mechanism for detecting a baseline current flowing through the superconducting transition edge sensor by the bias current, and the baseline current detected by the baseline monitor mechanism deviates from a predetermined value. A bias that adjusts the bias current to correct the baseline current according to the fluctuation range Characterized in that it comprises a flow adjusting mechanism.

  In this X-ray analyzer, the bias current adjustment mechanism uses a bias to correct the baseline current according to the fluctuation range when the baseline current detected by the baseline monitor mechanism fluctuates from a predetermined value. Since the current is adjusted, by adjusting the bias current from the outside and making the TES current constant, a constant peak value can always be obtained for characteristic X-rays of the same energy, and the energy resolution is stable and stable over the long term. Can be obtained.

  In the X-ray analysis apparatus of the present invention, it is preferable that a sampling frequency of the baseline current by the baseline monitor mechanism is set to 50 Hz or less. That is, in this X-ray analyzer, since the fluctuation of the baseline current is slower than the response frequency of TES (100 Hz or more), the baseline current sampling frequency (detection frequency) by the baseline monitor mechanism is set to a power supply commercial frequency of 50 Hz or less. By doing so, it becomes possible to efficiently adjust the sampling frequency corresponding to the temporal change of the baseline current.

  In the X-ray analyzer of the present invention, the bias current adjustment mechanism performs the adjustment based on an average value of the baseline current detected a plurality of times by the baseline monitor mechanism. That is, in this X-ray analyzer, since the bias current adjustment mechanism performs adjustment based on the average value of the baseline current detected multiple times by the baseline monitor mechanism, the sampled TES current having statistical fluctuations can be obtained. Averaging and highly reliable adjustment is possible.

In the X-ray analyzer of the present invention, the sensor circuit unit includes a shunt resistor having a resistance value smaller than that of the superconducting transition end sensor and connected in parallel to the superconducting transition end sensor. the operation resistance of the transition edge sensor and R _t, the current flowing through the superconducting transition edge sensor and I _t, when the resistance value of the shunt resistor and R _s, and the amount of change in the bias current and .delta.I _b, .delta.I and setting a relationship of _{b <0.1R t I t / R} s. That is, in this X-ray analyzer, high energy resolution of 10 eV or less can be stably realized by satisfying the above relational expression.

The present invention has the following effects.
That is, according to the X-ray analyzer according to the present invention, when the baseline current detected by the baseline monitor mechanism fluctuates from a predetermined value, the baseline current is corrected according to the fluctuation range. Since a bias current adjustment mechanism for adjusting the bias current is provided, a constant peak value can be obtained for characteristic X-rays of the same energy by adjusting the bias current from the outside and making the TES current constant. Therefore, it is not necessary to monitor known X-rays, and high energy resolution can be obtained stably over a long period of time.

  Hereinafter, an embodiment of an X-ray analysis apparatus according to the present invention will be described with reference to FIGS. 1 to 5.

  The X-ray analyzer of the present embodiment is an apparatus that can be used as a composition analyzer such as an electron microscope, an ion microscope, an X-ray microscope, and a fluorescent X-ray analyzer, for example, as shown in FIG. A sensor circuit unit 2 having a TES (superconducting transition edge sensor) 1 that receives and detects the energy as a temperature change and outputs it as a current signal, and a bias current that applies a constant voltage to the sensor circuit unit 2 to cause a bias current to flow. A source 3, a current detection mechanism 4 that detects a current flowing through the TES 1, a pulse height analyzer 5 that is connected to the current detection mechanism 4 and measures a peak value based on the detected current, and is connected to the current detection mechanism 4 A baseline monitor mechanism 6 for detecting a baseline current (current when no X-ray input is input) flowing in the TES 1 by the bias current, and a level detected by the baseline monitor mechanism 6 Surain current includes a bias current adjustment mechanism 7 for adjusting the bias current in order to correct the baseline current in accordance with the fluctuation width when fluctuates deviate from the default value.

The sensor circuit unit 2 includes a shunt resistor 8 having a resistance value smaller than that of the TES 1 and connected in parallel to the TES 1, and an input coil 9 connected in series to the TES 1.
As shown in FIG. 2, the TES 1, the shunt resistor 8, and the SQUID amplifier 10 are provided at the tip of a cold head 11 that is cooled to 50 mK to 400 mK by a refrigerator. The TES 1 and the SQUID amplifier 10 are connected by a superconducting wiring 12. As another example, as shown in FIG. 3, the TES 1 may be provided at the tip of the cold head 11 and the SQUID amplifier 10 may be provided at the tip of the cold block 13 that is cooled to 9K or less. The shunt resistor 8 is not shown in FIGS.

  In the sensor circuit unit 2, when a bias current is supplied from the bias current source 3, the current is branched by a resistance ratio between the resistance value of the shunt resistor 8 and the resistance value of the TES 1. That is, the voltage value of TES 1 is determined by the current flowing through the shunt resistor 8 and the voltage determined by the resistance value of the shunt resistor 8.

  The current detection mechanism 4 includes a SQUID amplifier 10 that is a low-temperature first-stage amplifier that detects a TES current as an electrical signal via an input coil 9, and a room temperature for amplifying and shaping the electrical signal output from the SQUID amplifier 10. An amplifier 14 and a pulse height analyzer 5 that selects an output signal from the room temperature amplifier 14 in accordance with a voltage peak value are provided. Although the SQUID amplifier 10 and the room temperature amplifier 14 using the input coil 9 are used as the current detection mechanism 4, other configurations may be adopted as long as the displacement of the current flowing through the TES 1 can be detected. .

The room temperature amplifier 14 amplifies the X-ray pulse signal, which is a signal generated when X-rays are incident, out of the output from the SQUID amplifier 10 and the baseline signal based on the baseline current when no X-rays are incident.・ Has a function to output after shaping.
The wave height analyzer 5 is a multi-channel pulse height analyzer that obtains the voltage pulse wave height from the X-ray pulse signal sent from the room temperature amplifier 14 and generates an energy spectrum. This pulse height analyzer 5 monitors only the X-ray pulse signal, reads the peak value of the X-ray pulse signal, counts the peak value in the histogram graph with the vertical axis as the count and the horizontal axis as the peak value. Add one. The wave height analyzer 5 has a function of repeating the same operation for a plurality of X-ray pulse signals, creating a histogram, and displaying the histogram on a display device or the like.
Further, the wave height analyzer 5 may use a function such as a filter operation for smoothing the wave height value of the X-ray pulse signal.

  The baseline monitor mechanism 6 monitors only the baseline signal that does not include the X-ray pulse signal among the output signals from the room temperature amplifier 14. The baseline monitor mechanism 6 monitors the fluctuation of the baseline current and has a function of sending a command signal for changing the bias current to the bias current adjusting mechanism 7 when the fluctuation of the baseline current occurs. .

The bias current adjusting mechanism 7 is connected to the baseline monitor mechanism 6, receives a command signal for adjusting the bias current from the baseline monitor mechanism 6, and responds to the bias current source 3 according to the fluctuation range of the baseline current. To control the bias current.
Specific functions will be described later.

As shown in FIG. 4, the TES 1 includes an absorber 15 such as a metal body, a semimetal, a superconductor, etc. for absorbing X-rays, and a superconductor that detects heat generated in the absorber 15 as a temperature change. The thermometer 16 is composed of a body, and the membrane 17 is connected to the thermometer 16 and the cold head 11 so as to be loosely thermally connected to control a heat flow that escapes to a heat bath (not shown). For example, gold can be used as the absorber 15, a material composed of two layers of titanium and gold can be used as the thermometer 16, and a silicon nitride film can be used as the membrane 17 and the heat bath.
In order to maintain the resistance value of TES1 in an intermediate state between normal conduction and superconductivity, Joule heat generated in the thermometer 16 flows through the membrane 17 from the thermometer 16 (or the absorber 15) to the cold head 11. And be thermally balanced.

  The thermal balance between Joule heat and heat flow through the membrane is given by equation (1). However, in practice, the TES current is not determined by equation (1), and the TES current is affected by thermal fluctuations from the outside of TES1. When the heat fluctuation from the outside of the TES 1 is Pex, the equation (1) is rewritten by the equation (3).

Here, Rs is the resistance value of the shunt resistor 8.
The first term on the left side and the right side of Equation (3) are in thermal balance. Therefore, when Pex increases, δIt of the second term on the left side decreases so as to satisfy Equation (3). Examples of heat fluctuations from the outside include temperature fluctuations of the cold head 11 that cools the TES 1, fluctuations in heat radiation due to temperature fluctuations of the heat shield 18 that surrounds the cold head 11, or heat through residual gas present in the refrigerator. There are temperature fluctuations of the heat shield 18 due to heat conduction from the shield 18 to the TES 1.

  The temperature variation of the cold head 11 is controlled to be a constant temperature by a heater provided in the cold head 11 and a PID control system that is feedback control built in the thermometer 16. Since the temperature of the heat shield 18 surrounding the cold head 11 cannot be controlled, the heat shield 18 is cooled to the lowest temperature. Furthermore, temperature fluctuations due to heat conduction through the residual gas are devised to reduce Pex by exhausting the residual gas as much as possible before cooling. However, even if the above measures are taken, Pex varies, and the current flowing through TES1 varies according to equation (3).

  Normally, the bias current is constant, but the thermal equation when the bias current is variable is given by the following equation (4).

  When the heat fluctuation Pex enters the TES 1 from the outside, according to the equation (4), Pex may be canceled by the second term or the third term on the left side. In order not to cause a change in the TES current, δIt may be set to 0. Therefore, the bias current may be reduced by the following equation (5).

  The relationship among the bias current change δIb, the TES current change δIt, and the TES resistance change δRt is given by the following equation (6).

  Since there is no change in the TES current, a change in the bias current causes a change in the TES operating resistance by the following equation (7).

  The change in operating resistance of TES1 causes a change in sensitivity α expressed by the following equation (8).

  When the resistance changes by δRt, the sensitivity α ′ is expressed by the following formula (9).

  For example, when the sensitivity of TES1 is 100, consider a case where a pulse with a peak value of 10 uA is generated for 5900 eV characteristic X-rays. According to equation (2), when the sensitivity is 99.9, the energy for the peak value of 10 uA is 5894 eV, which is shifted by about 6 eV. In the case of a high energy resolution detector having an energy resolution of 10 eV or less, a shift of 6 eV may be considered as a practical limit of shift. Therefore, it is desirable that the amount of change in the bias current is expressed by the following formula (10).

  For example, when Rt = 32 mW, Rs = 4 mW, It = 50 μA, the change width of the bias current is 40 μA or less. As described above, the cause of the current change of the TES 1 is due to the external thermal fluctuation. In this case, the TES current can be kept constant by changing the bias current.

  In the present embodiment, the baseline monitor mechanism 6 monitors a change in the current flowing through the TES 1, and the baseline monitor mechanism 6 changes the bias current to the bias current adjustment mechanism 7 based on the above mechanism. The command is transmitted to 7. The bias current adjusting mechanism 7 changes the bias current value of the bias current source 3 in accordance with the command.

  At this time, it is necessary to determine the X-ray pulse signal and the baseline signal in the signal output from the room temperature amplifier 14. The pulse height analyzer 5 is provided with a trigger function, and recognizes as an X-ray pulse signal when a certain threshold value is exceeded. In the baseline monitor mechanism 6, an upper limit value and a lower limit value can be set for the signal from the room temperature amplifier 14, and a signal within the range is recognized as a baseline.

  For example, when the upper limit value and the lower limit value are set to +100 mV and −100 mV, the signal from the room temperature amplifier 14 within this range is always recognized as a baseline signal. Since the fluctuation of the baseline current is slower than the response frequency (100 Hz or more) of TES1, it is desirable that the current in the SQUID amplifier 10, that is, the sampling frequency of the TES current is 50 Hz or less of the commercial power frequency. Further, since the sampled TES current has a statistical fluctuation, for example, it is preferable to average N sampling data and monitor the averaged data.

As shown in FIG. 1, the bias current adjustment mechanism 7 includes an adjustment amount data storage unit 19, an adjustment amount calculation unit 20, and a bias current adjustment unit 21.
The adjustment amount data storage unit 19 is a storage unit such as a memory that stores in advance an adjustment value of the bias current necessary for making the fluctuation zero with respect to the fluctuation of the TES current as a database or an approximate expression. It is.

The adjustment amount calculation unit 20 is an arithmetic circuit that obtains a necessary adjustment amount from the adjustment amount data storage unit 19 based on a change in the TES current that is the output of the baseline monitor mechanism 6.
The bias current adjusting unit 21 has a function of adjusting and outputting the bias current so that the bias current is changed and a current reflecting the obtained adjustment amount is applied to the TES 1.

Next, a bias current adjusting method by the bias current adjusting mechanism 7 will be described with reference to a flowchart shown in FIG.
First, the baseline monitor mechanism 6 detects the variation of the TES current as described above (step S1), and the adjustment amount calculation unit 20 adjusts based on the variation of the TES current sent from the baseline monitor mechanism 6. A necessary adjustment amount is obtained from the amount data storage unit 19 (step S2).

Next, the bias current adjusting unit 21 changes the bias current based on the obtained adjustment amount, and adjusts and outputs the bias current so that the current reflecting the obtained adjustment amount is applied to the TES 1 (step S3). ).
By repeating the above cycle until the analysis is completed (step S4), the fluctuation of the peak value during the analysis is suppressed, and the analysis with high energy resolution is realized.

  As described above, in the X-ray analysis apparatus according to the present embodiment, the bias current adjusting mechanism 7 has a base current corresponding to the fluctuation range when the baseline current detected by the baseline monitor mechanism 6 fluctuates from a predetermined value. Since the bias current is adjusted to correct the line current, by adjusting the bias current from the outside and making the TES current constant, a constant peak value can always be obtained for characteristic X-rays of the same energy, High energy resolution can be obtained.

  In addition, since the fluctuation of the baseline current is slower than the response frequency of TES (100 Hz or more), the baseline current sampling frequency (detection frequency) by the baseline monitor mechanism 6 is set to a power supply commercial frequency of 50 Hz or less, thereby reducing the baseline. Adjustment can be efficiently performed at a sampling frequency corresponding to a temporal change in current.

Further, since the bias current adjustment mechanism 7 performs adjustment based on the average value of the baseline current detected a plurality of times by the baseline monitor mechanism 6, the sampled TES current having statistical fluctuations is averaged and reliability is improved. High adjustment is possible.
Furthermore, by satisfying the relational expression of the above expression (10), it is possible to stably realize a high energy resolution of 10 eV or less.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

1 is a schematic overall configuration diagram showing an embodiment of an X-ray analysis apparatus according to the present invention. In this embodiment, it is a rough expanded side view of the principal part which shows the example of mounting of TES and a SQUID amplifier. In this embodiment, it is a general | schematic expanded side view of the principal part which shows the other mounting example of TES and a SQUID amplifier. In this embodiment, it is explanatory drawing which shows the structure of TES roughly. In this embodiment, it is a flowchart which shows the adjustment method of the bias current by a bias current adjustment mechanism. In this embodiment, it is a graph which shows the relationship between the output value after a filter with respect to a crest value (vertical axis | shaft: a pulse crest value is displayed) and the electric current which flows into a SQUID amplifier (horizontal axis: the electric current which flows into TES).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... TES (superconducting transition edge sensor), 2 ... Sensor circuit part, 3 ... Bias current source, 4 ... Current detection mechanism, 5 ... Wave height analyzer, 6 ... Baseline monitor mechanism, 7 ... Bias current adjustment mechanism

Claims (4)

A sensor circuit unit having a superconducting transition edge sensor that receives X-rays and detects the energy as a temperature change and outputs it as a current signal;
A bias current source for applying a constant voltage to the sensor circuit section to flow a bias current;
A current detection mechanism for detecting a current flowing through the superconducting transition edge sensor;
A pulse height analyzer connected to the current detection mechanism and measuring a peak value based on the detected current;
A baseline monitor mechanism connected to the current detection mechanism for detecting a baseline current flowing through the superconducting transition edge sensor by the bias current;
A bias current adjusting mechanism that adjusts the bias current to correct the baseline current according to the fluctuation range when the baseline current detected by the baseline monitor mechanism fluctuates from a predetermined value; And an X-ray analyzer. The X-ray analyzer according to claim 1,
The X-ray analyzer according to claim 1, wherein a sampling frequency of the baseline current by the baseline monitor mechanism is set to 50 Hz or less. In the X-ray analyzer according to claim 1 or 2,
The X-ray analyzer according to claim 1, wherein the bias current adjustment mechanism performs the adjustment based on an average value of the baseline current detected a plurality of times by the baseline monitor mechanism. In the X-ray analyzer according to any one of claims 1 to 3,
The sensor circuit unit includes a shunt resistor having a resistance value smaller than that of the superconducting transition end sensor and connected in parallel to the superconducting transition end sensor;
The operating resistance of the superconducting transition edge sensor is R _t ,
A current flowing through the superconducting transition edge sensor and I _t,
The resistance value of the shunt resistor is R _s ,
When the amount of change in the bias current is δI _b ,
_{δI b <0.1R t I t /} R s
An X-ray analyzer characterized in that the relationship is set as follows.

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