Time-of-flight mass spectrometer

Abstract

Inside a chamber (10) evacuated by a vacuum pump, a flight tube (12) is held via a support member (11) that is of insulation. The outside of the chamber (10) is surrounded by a temperature control unit (16) including a heater. A body (10a) of the chamber (10) is made of aluminum, and a coating layer (10b) by a black nickel plating is formed on the inner wall surface of the body (10a) of the chamber (10). Due to this, the radiation factor of the chamber (10) becomes higher than that of a conventional apparatus using only aluminum, and the thermal resistance of the radiation heat transfer path between the chamber (10) and the flight tube (12) becomes low, thus improving the temperature stability of the flight tube (12). Furthermore, the time constant of the temperature change of the flight tube (12) becomes small, thus reducing the time for the flight tube (12) to stabilize to a constant temperature.

Claims

1. A time-of-flight mass spectrometer, comprising: a chamber whose inside is maintained in vacuum; a flight tube disposed inside of the chamber and separated from an inner wall of the chamber; and a temperature control unit configured to control temperature outside the chamber, wherein a radiation factor improvement treatment is done to a part of an inner wall surface of the chamber facing the flight tube, the radiation factor improvement treatment being to make the part of the inner wall surface black.

2. The time-of-flight mass spectrometer according to claim 1, wherein the radiation factor improvement treatment is a surface treatment for an inner wall surface of a material forming the chamber.

3. The time-of-flight mass spectrometer according to claim 2, wherein the surface treatment is a coating film formation treatment of forming a thin coating film on a surface of a material forming the chamber.

4. The time-of-flight mass spectrometer according to claim 3, wherein the chamber is made of aluminum, and the surface treatment is a black alumite forming treatment.

5. The time-of-flight mass spectrometer according to claim 3, wherein the surface treatment is a black nickel plating treatment.

6. The time-of-flight mass spectrometer according to claim 3, wherein the surface treatment is a carbon coating film formation treatment.

7. The time-of-flight mass spectrometer according to claim 2, wherein the surface treatment is a processing treatment of roughening a surface of a material forming the chamber by chemically or physically shaving the surface.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic configuration diagram of a main part of a TOFMS according to an embodiment of the present invention.

(2) FIG. 2 is a schematic cross-sectional view of a chamber in a TOFMS according to another embodiment.

DESCRIPTION OF EMBODIMENTS

(3) Hereinafter, a TOFMS according to an embodiment of the present invention will be described with reference to the accompanying drawings.

(4) FIG. 1 is a schematic configuration diagram of a main part of the TOFMS of the present embodiment.

(5) The TOFMS of the present embodiment is a quadrupole-time-of-flight mass spectrometer (Q-TOFMS) including an ion source (not shown), a quadrupole mass filter (not shown), a collision cell (not shown), and an orthogonal acceleration TOFMS 1 appearing in FIG. 1, and various product ions generated by dissociating precursor ions of a predetermined mass-to-charge ratio in the collision cell are introduced in the X direction from the left-hand side in FIG. 1.

(6) In FIG. 1, inside a chamber 10 evacuated by a vacuum pump such as a turbo-molecular pump (not shown), a substantially cylindrical or square tubular flight tube 12 is held via a support member 11 having high insulation quality and high vibration absorption quality. An orthogonal acceleration unit 14 and an ion detector 15 are each fixed to the flight tube 12 via a support member (not shown). A reflector 13 constituted by a plurality of annular or rectangular annular reflection electrodes is disposed inside the flight tube 12 on a lower side, and a reflectron-type flight space in which ions are turned back by a reflection electric field formed by the reflector 13 is provided inside the flight tube 12.

(7) The flight tube 12 is made of metal such as stainless steel, and a predetermined direct-current (DC) voltage is applied to the flight tube 12. Furthermore, different DC voltages are applied respectively to a plurality of reflection electrodes constituting the reflector 13 with reference to the voltage applied to the flight tube 12. Due to this, a reflection electric field is formed in the reflector 13, while the rest of the flight space is in a high-vacuum atmosphere free from an electric field or a magnetic field.

(8) As shown in FIG. 1, when a pulsed DC voltage is externally applied to an acceleration electrode in the orthogonal acceleration unit 14 in a state where ions are introduced into the orthogonal acceleration unit 14 in the X direction, the ions are given predetermined kinetic energy in the Z direction by the DC voltage. This causes the ions to be sent from the orthogonal acceleration unit 14 into the flight space in the flight tube 12. The ions fly in the flight space through a trajectory shown by a dotted line in FIG. 1 and reach the ion detector 15. The velocity of an ion in the flight space depends on the mass-to-charge ratio of the ion. Thus, ions having different mass-to-charge ratios introduced into the flight space at substantially the same time are separated in accordance with the mass-to-charge ratios during the flight, and reach the ion detector 15 with a time difference. A detection signal from the ion detector 15 is input to a signal processing unit (not shown), and a mass spectrum is generated by converting the flight time of each ion into a mass-to-charge ratio.

(9) When the flight tube 12 expands due to heat, the flight distance changes, which results in an error in the mass-to-charge ratio. Therefore, in order to enhance the temperature stability of the flight tube 12, the TOFMS of the present embodiment is configured as follows.

(10) The temperature of the chamber 10 is controlled to a predetermined temperature by a temperature control unit 16 including a heater and a temperature sensor disposed around the chamber. The flight tube 12 is heated so as to be maintained at a constant temperature mainly by radiation heat transfer from the temperature-controlled chamber 10, and the inner wall surface of the chamber 10 is provided with a surface treatment that enhances the radiation factor so as to increase the efficiency of radiation heat transfer. Specifically, in the present embodiment, the chamber 10 is made of aluminum, which is less expensive than stainless steel, and a coating layer 10b is formed by a black nickel plating treatment on the inner wall surface of a body 10a of the aluminum chamber 10 at least in a part facing the flight tube 12.

(11) As is well known, black nickel plating is one of the most commonly used plating for anti-reflection and decoration purposes, and its processing cost is relatively inexpensive. When the coating layer 10b by black nickel plating is formed, the surface becomes black and the radiation factor is enhanced. The present inventor has experimentally confirmed that the radiation factor can be increased by about 10 times by forming the coating layer 10b by black nickel plating on the inner wall surface of the body 10a of the chamber 10 made of aluminum. Due to this, in the TOFMS of the present embodiment, the thermal resistance in the path of radiation heat transfer between the chamber 10 and the flight tube 12 is significantly reduced as compared with the conventional TOFMS (in the case where the coating layer 10b by black nickel plating is not formed), and the temperature stability of the flight tube 12 can be improved.

(12) The present inventor has experimentally confirmed that in the TOFMS of the present embodiment, the amount of temperature change of the flight tube 12 with respect to the stepwise change in room temperature can be suppressed to about ½ as compared with the conventional TOFMS. On the other hand, it has been confirmed that it is possible to shorten the temperature stabilization time of the flight tube 12 by about 60% as compared with the conventional TOFMS.

(13) In the above embodiment, in order to improve the radiation factor of the inner wall surface of the chamber 10, a coating layer by black nickel plating is formed. However, in the present invention, the treatment that improves the radiation factor is not limited to this.

(14) For example, when the chamber 10 is made of aluminum as described above, normal nickel plating may be used instead of the black nickel plating, or a coating layer may be formed by an alumite forming treatment. Alternatively, a coating layer capable of improving the radiation factor may be formed on the surface of the chamber 10 by a carbon coating film formation treatment, a ceramic thermal spraying treatment, or another plating treatment, coating or a coating treatment, a thermal spraying treatment, or the like.

(15) Furthermore, instead of forming a coating layer made of material different from that of the chamber 10, the surface of the chamber 10 itself may be chemically or physically shaved to form irregularities. FIG. 2 shows an example of an irregular surface 10c formed by such a processing treatment. This also increases the radiation factor of the inner wall surface of the chamber 10, and thus the same effects as in the above embodiment can be achieved.

(16) Furthermore, instead of forming the coating layer by various types of processing treatments as described above, a thin plate or thin foil made of another material having a higher radiation factor than that of the material of the chamber 10 may be attached to the inner wall surface of the chamber 10. Specifically, a thin stainless steel plate may be attached to the inner wall surface of the chamber 10 made of aluminum as described above. This also increases the radiation factor of the inner wall surface of the chamber 10, and thus the same effects as in the above embodiment can be achieved.

(17) The above embodiment is merely an example of the present invention, and it is obvious that modifications, alterations, additions, and the like appropriately made within the scope of the present invention, in addition to the above-described variations, and are included in the scope of claims of the present invention.

(18) For example, although the above embodiment is a reflectron-type TOFMS of an orthogonal acceleration type, it is not necessary to be of an orthogonal acceleration type, and it may be a configuration in which ions emitted from an ion trap are introduced into the flight space or a configuration in which ions generated from a sample by a MALDI ion source or the like are accelerated and introduced into the flight space. A linear TOFMS may be used instead of the reflectron-type TOFMS.

REFERENCE SIGNS LIST

(19) 1 . . . Orthogonal Acceleration TOFMS 10 . . . Chamber 10a . . . Body 10b . . . Coating Layer 10c . . . Irregular Surface 11 . . . Support Member 12 . . . Flight Tube 13 . . . Reflector 14 . . . Orthogonal Acceleration Unit 15 . . . Ion Detector 16 . . . Temperature Control Unit