# US 2019/0244801 A1 · Time-of-flight mass spectrometer

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- Number: US 2019/0244801 A1
- Document ID: US20190244801A1
- Status: Published application
- Kind: A1
- Application number: 15/891,445
- Filed: 2018-02-08
- Published: 2019-08-08
- Earliest claimed: 2018-02-08
- Assignees: Shimadzu Corporation
- Applicants: Shimadzu Corporation
- Inventors: Ryo FUJITA
- Web page: https://patentgrep.com/patent/US20190244801A1

## CPC

- H01J 49/067: {Ion lenses, apertures, skimmers}
- H01J 49/403: {characterised by the acceleration optics and/or the extraction fields}
- H01J 49/0086: {Accelerator mass spectrometers}
- H01J 49/405: {characterised by the reflectron, e.g. curved field, electrode shapes}
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

A shielding plate 6 having a forward-side slit opening 61 and return-side slit opening 62 is placed in a free flight space 3 with no electric field. Ions which significantly deviate from a reference path are removed by the shielding plate 6 on both the forward-side and return-side paths. The opening width of the forward-side slit opening 61 is smaller than that of the return-side slit opening 62. Those opening widths and the placement position of the shielding plate 6 are determined based on the result of an ion trajectory calculation by accurate simulation. As compared to a conventional device with a shielding plate placed only on the return side, the present configuration allows for an increase in the opening width of the return-side slit opening while achieving the same level of resolving power. The ion transmission ratio is thereby improved, and the analytical sensitivity is enhanced.

## Claims

### Claim 1

A reflectron time-of-flight mass spectrometer including: a time-of-flight mass separator including a free flight space with no electric field and an ion reflector for reflecting an ion; an ion accelerator for accelerating an ion into the free flight space; and a detector for detecting an ion returning from a round trip in which the ion initially flies through the free flight space and once more flies through the free flight space after being reflected by the ion reflector, wherein:
a shielding plate is placed in the free flight space, the shielding plate having a forward-side opening located on a forward-side ion path directed from the ion accelerator to the ion reflector and a return-side opening located on a return-side ion path directed from the ion reflector and the detector; and
a width of the forward-side opening of the shielding plate in an extending direction of a plane on which both a central axis of the forward-side ion path and a central axis of the return-side ion path lie is smaller than a width of the return-side opening in the same direction.

### Claim 2 (depends on 1)

The reflectron time-of-flight mass spectrometer according to claim 1, further comprising an ion-converging lens for converging a packet of ions.

### Claim 3 (depends on 1)

The reflectron time-of-flight mass spectrometer according to claim 1, wherein the ion reflector comprises a plurality of reflecting electrodes arrayed along a central line at predetermined intervals.

### Claim 4 (depends on 3)

The reflectron time-of-flight mass spectrometer according to claim 3, wherein the shielding plate is placed so that a center axis of the shielding plate aligns with the central line.

### Claim 5

A reflectron time-of-flight mass spectrometer including: a time-of-flight mass separator including a free flight space with no electric field and an ion reflector for reflecting an ion; an ion accelerator for accelerating an ion into the free flight space; and a detector for detecting an ion returning from a round trip in which the ion initially flies through the free flight space and once more flies through the free flight space after being reflected by the ion reflector, wherein:
a shielding plate is placed in the free flight space, the shielding plate having a single asymmetrical opening through which ions received from a forward-side ion path directed from the ion accelerator to the ion reflector pass and through which ions returning from the reflector to a return-side ion path directed from the ion reflector and the detector pass,
the single asymmetrical opening being asymmetrical with respect to a central line axis of reflecting electrodes of the ion reflector.