JPH0342617Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a mass spectrometer equipped with an electromagnetic device that generates a magnetic field for analysis, and in particular to a mass spectrometer that can eliminate relatively high-frequency magnetic field fluctuations caused by external magnetic lines of force coming from the outside. It is related to.

The analytical magnetic field of a mass spectrometer is desired to have smaller intensity fluctuations as the resolution of the device increases. Therefore, conventionally, a magnetic field strength detection element such as a Hall element is placed in the magnetic field, the detection signal from the element is compared with a reference signal, and the excitation current is controlled so that the difference becomes zero, so that the magnetic field strength is always I try to keep it constant.

However, in such conventional methods, the inductance of the excitation coil is large, so although it is possible to cancel out the relatively slow fluctuations in the magnetic field,
For example, it has been difficult to cancel small fluctuations at a relatively high frequency (for example, on the order of several tens of Hz) in the analytical magnetic field caused by external magnetic lines of force that jump into the yoke of the electromagnet that generates the magnetic field, the excitation coil, etc.

The present invention has been made in view of this point, and is a mass-mass device equipped with an electromagnetic device that generates a magnetic field for separating ions according to their mass-to-charge ratio, and a means for sweeping the strength of the magnetic field. In the analyzer, a detection coil disposed in the magnetic circuit of the electromagnet device, an auxiliary excitation coil disposed in the magnetic circuit of the electromagnet device, and a current based on the detection signal from the detection coil for the auxiliary excitation. Mass spectrometry that can cancel relatively high-frequency magnetic field fluctuations in the analytical magnetic field by providing a power supply for supplying the coil and a current limiting circuit that limits the current supplied from the power supply to the auxiliary excitation coil. The purpose is to provide equipment. Hereinafter, the present invention will be explained in detail using the drawings.

The drawing is a configuration diagram showing an embodiment of the present invention. In the figure, 1 is a yoke, 2 and 3 are pole pieces, 4 and 5 are excitation coils, and 6 is a magnetic field control power source. A magnetic field strength detection element 7 such as a Hall element is arranged in the magnetic field formed between the pole pieces 2 and 3, and a detection signal obtained from the element 7 is sent to an amplifier 8.
The signal is sent to the magnetic field control power source 6 via the magnetic field control power source 6. Since the control power source 6 controls the excitation current supplied to the excitation coils 4 and 5 based on the difference signal between the detection signal and the reference signal R, the magnetic field strength is maintained at a constant value corresponding to the reference signal. .

As mentioned above, such a control system cannot cancel magnetic field fluctuations caused by high-frequency external magnetic lines of force. Therefore, in the present invention, the following configuration is added. That is,
9 is a detection coil that is placed in the magnetic circuit of the electromagnet that generates the analysis magnetic field and detects relatively high-frequency magnetic field fluctuations; 10 is an auxiliary excitation coil that generates a magnetic field that cancels out the magnetic field fluctuations, and is wound directly on the yoke 1; In order to improve the frequency characteristics, the coil 10
For example, the inductance is set to 1 mH or less. The detection signal obtained from the detection coil 9 is
It is sent via an amplifier 11 and a phase shift circuit 12 to a power source 13 that supplies current to the auxiliary excitation coil.
A current limiting circuit 14 is inserted between the power source 13 and the detection coil 9.

In this configuration, a high-frequency disturbance magnetic flux change is detected as a voltage by the detection coil 9, and the obtained detection signal is sent to the power source 13 after the phase shift is adjusted via the phase shift circuit 12. The power source 13 is
A current corresponding to the detection signal is sent to the auxiliary excitation coil 10, but since the auxiliary excitation coil is wound in a direction that generates magnetic flux in a direction that cancels out the detected disturbance magnetic field change, the disturbance magnetic field is canceled. The magnetic field will be stabilized even against high frequency fluctuations.

The above is a case where the magnetic field is in a steady state, but in order to obtain a mass spectrometry spectrum, the reference signal R
For example, when sweeping in a sawtooth waveform, an excessive voltage is generated in the detection coil 9 due to changes in the magnetic field, and based on this excessive detection signal, the power supply 13 attempts to flow an excessive current to the auxiliary excitation coil 10, but the current limit circuit 1
4, the magnetic field does not become unstable even during sweeping.

As described in detail above, according to the present invention, an apparatus is realized that can stabilize the magnetic field strength against high frequency fluctuations both in a steady state and in a sweep state.

In the above embodiment, the current limiting circuit 14 is provided between the power source 13 and the auxiliary excitation coil 10, but even if a voltage limiting circuit is inserted between the amplifier 11 and the power source 13, the current is still supplied to the auxiliary excitation coil 10. It is possible to limit the current, and furthermore, the amplifier 11 may have a voltage limiting function.

[Brief explanation of the drawing]

The accompanying drawings are block diagrams showing one embodiment of the present invention. 1: Yoke, 2, 3: Pole piece, 9: Detection coil, 10: Auxiliary excitation coil, 12: Phase shift circuit, 13: Power supply, 14: Current limiting circuit.

Claims (1)

[Scope of utility model registration request] In a mass spectrometer equipped with an electromagnetic device that generates a magnetic field for separating ions according to their mass-to-charge ratio, and means for sweeping the intensity of the magnetic field, the method is arranged in a magnetic circuit of the electromagnetic device. a detection coil, an auxiliary excitation coil installed in the magnetic circuit of the electromagnet device, a power source for supplying a current to the auxiliary excitation coil based on a detection signal from the detection coil, and an auxiliary excitation coil from the power source. A mass spectrometer comprising: a current limiting circuit that limits the current supplied to the mass spectrometer.