Field axis deceleration method for improving ion transmission rate

Abstract

The invention relates to a field axis deceleration method for improving ion transmission rate, and belongs to the technical field of ion source extraction ion control of mass spectrum detection. The kinetic energy generated when ions leave the ion source is increased, so that the ions rapidly pass through the fringe field of the analyzer, the retention time is shortened, and the scattering loss of the ions in the fringe field is reduced. The ion source has the characteristics that the emitting speed of ions of the ion source is improved, the ions can pass through a fringe field of an analyzer at a high speed, more ions can enter the analyzer, meanwhile, the difference of influences of the fringe field on ions with different mass-to-charge ratios is reduced, and the quality discrimination effect is improved. The method can be used for designing various mass spectrometry instruments. The positive bias voltage is increased for the ion source, so that the ion movement speed is increased, and the ion can quickly pass through a fringe field; certain bias voltage is added to the analyzer, so that kinetic energy is reduced to required kinetic energy when ions enter the analyzer, and the ion separation requirement of the analyzer is met.

Description

Technical Field

[0001] The invention relates to a field axis deceleration method for improving ion transmission rate, belonging to the technical field of ion source extraction control of mass spectrometry detection. Background Art

[0002] Mass spectrometry is an important method for measuring and analyzing the composition of materials. It is a universal method with rapid response, high sensitivity and wide application.

[0003] There is a fringe field between the ion source and the analyzer. The kinetic energy of ions leaving the ion source is generally 10eV. The fringe field will cause ion scattering losses, resulting in a decrease in ion transmission rate, which directly affects the sensitivity and resolution of the mass spectrometer. The longer the ions are in the fringe field, the greater the impact of the fringe field and the more serious the instrument performance degradation. Therefore, measures need to be taken to reduce the impact of the fringe field on the ions. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and to propose a field axis deceleration method for improving ion transmission rate, which can greatly shorten the time of ions in the edge field and improve the sensitivity of the mass spectrometer.

[0005] The technical solution of the present invention is:

[0006] A field axis deceleration method for improving ion transmission rate, the method increases the ion movement speed by adding a positive bias voltage to the ion source, and can quickly pass through the edge field; the method also increases the bias voltage to the analyzer, so that the kinetic energy of the ions when entering the analyzer is reduced to the required kinetic energy, thereby meeting the ion separation requirements of the analyzer.

[0007] The method is applied to ion sources and analyzers in mass spectrometry instruments;

[0008] The field axis deceleration method comprises:

[0009] A positive bias voltage U1 is set in the ion source so that the ions have a large kinetic energy eU1 when leaving the ion source, wherein the ions are generated by ionization of the sample molecules to be measured in the ion source;

[0010] The analyzer has a metal shell, which is at ground potential to form a shield to prevent the electric field of the analyzer from interfering with the ion source;

[0011] A positive bias voltage U2 is set on the analyzer to reduce the kinetic energy of ions emitted by the ion source to e(U1-U2) when entering the analyzer, thereby facilitating the analyzer to separate the ions;

[0012] The ion source bias voltage U1 is generally between (100 and 200) V. A bias voltage that is too low has little effect on improving the ion transmission rate, while a bias voltage that is too high will make the ion velocity too fast, resulting in other adverse effects such as secondary electron emission.

[0013] The reduced kinetic energy of the ions, e(U1-U2), is generally between (5 and 10) eV, which is an energy suitable for ion separation by an analyzer;

[0014] The kinetic energy of the ions when they leave the ion source directly affects the ion movement rate. The time for the ions to move in the edge field is

[0015]

[0016] Where L is the length of the edge field, v is the ion movement velocity, E is the ion kinetic energy, m is the ion mass, e is the unit charge carried by the ion, and U is the potential difference between the ion and the ground when it leaves the ion source;

[0017] Before the field axis deceleration method is adopted, E is generally 10 eV, which is E1;

[0018] After using the field axis deceleration method, E increases to (100-200) eV, and E2 = 100 eV. For ions with the same mass-to-charge ratio,

[0019]

[0020] From the above formula, we can see that after using the field axis deceleration method, the time that ions spend in the edge field is shortened to the original Below, thereby reducing the scattering loss of ions in the fringe field.

[0021] The beneficial effects of the present invention compared with the prior art are:

[0022] The present invention discloses a field axis deceleration method for improving ion transmission rate, which increases the kinetic energy of ions when they leave the ion source, enables them to quickly pass through the edge field of the analyzer, shortens the residence time, and thus reduces the scattering loss of ions in the edge field. The present invention is characterized in that the exit speed of ions from the ion source is increased, so that the ions can pass through the edge field of the analyzer at a high speed, allowing more ions to enter the analyzer, while also reducing the difference in the influence of the edge field on ions with different mass-to-charge ratios, thereby improving the mass discrimination effect. The present invention can be used in the design of various mass spectrometry instruments. By adding a positive bias voltage to the ion source, the ion movement speed is increased, and the ions can quickly pass through the edge field; by adding a certain bias voltage to the analyzer, the kinetic energy of the ions is reduced to the required kinetic energy when they enter the analyzer, meeting the ion separation requirements of the analyzer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a schematic diagram of field axis deceleration for improving ion transmission rate according to the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0025] Example

[0026] A field axis deceleration method for improving ion transmission rate, the method increases the ion movement speed by adding a positive bias voltage to the ion source, and can quickly pass through the edge field; the method also increases the bias voltage to the analyzer, so that the kinetic energy of the ions when entering the analyzer is reduced to the required kinetic energy, thereby meeting the ion separation requirements of the analyzer.

[0027] This method is applied to ion sources and analyzers in mass spectrometry instruments, such as Figure 1 As shown;

[0028] The field axis deceleration method comprises:

[0029] A positive bias voltage U1 is set in the ion source so that the ions have a large kinetic energy eU1 when leaving the ion source, wherein the ions are generated by ionization of the sample molecules to be measured in the ion source;

[0030] The analyzer has a metal shell, which is at ground potential to form a shield to prevent the electric field of the analyzer from interfering with the ion source;

[0031] A positive bias voltage U2 is set on the analyzer to reduce the kinetic energy of ions emitted by the ion source to e(U1-U2) when entering the analyzer, thereby facilitating the analyzer to separate the ions;

[0032] The ion source bias voltage U1 is generally between (100 and 200) V. A bias voltage that is too low has little effect on improving the ion transmission rate, while a bias voltage that is too high will make the ion velocity too fast, resulting in other adverse effects such as secondary electron emission.

[0033] The reduced kinetic energy of the ions, e(U1-U2), is generally between (5 and 10) eV, which is an energy suitable for ion separation by an analyzer;

[0034] The kinetic energy of the ions when they leave the ion source directly affects the ion movement rate. The time for the ions to move in the edge field is

[0035]

[0036] Where L is the length of the edge field, v is the ion movement velocity, E is the ion kinetic energy, m is the ion mass, e is the unit charge carried by the ion, and U is the potential difference between the ion and the ground when it leaves the ion source;

[0037] Before the field axis deceleration method is adopted, E is generally 10 eV, which is E1;

[0038] After using the field axis deceleration method, E increases to (100-200) eV, and E2 = 100 eV. For ions with the same mass-to-charge ratio,

[0039]

[0040] From the above formula, we can see that after using the field axis deceleration method, the time that ions spend in the edge field is shortened to the original Below, thereby reducing the scattering loss of ions in the fringe field.

[0041] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A field axis deceleration method for improving ion transmission rate, characterized in that: The method is applied to ion sources and analyzers in mass spectrometry instruments; The method comprises setting a positive bias voltage U1 in the ion source so that the ions have a large kinetic energy eU1 when leaving the ion source, wherein the ions are generated by ionization of the sample molecules to be measured in the ion source; A positive bias voltage U2 is set on the analyzer, so that the kinetic energy of ions emitted by the ion source is reduced to e(U1-U2) when entering the analyzer, thereby facilitating the analyzer to separate the ions.

2. A field axis deceleration method for improving ion transmission rate according to claim 1, characterized in that: The analyzer has a metal shell which is at ground potential to form a shield to prevent the electric field of the analyzer from interfering with the ion source.

3. A field axis deceleration method for improving ion transmission rate according to claim 1, characterized in that: The ion source bias voltage U1 is between (100 and 200) V. A bias voltage that is too low has little effect on improving the ion transmission rate, while a bias voltage that is too high will make the ion velocity too fast, causing adverse effects on secondary electron emission.

4. A field axis deceleration method for improving ion transmission rate according to claim 1, characterized in that: The reduced kinetic energy e(U1-U2) of the ions is between (5 and 10) eV.

5. A field axis deceleration method for improving ion transmission rate according to claim 1, characterized in that: The kinetic energy of the ions when they leave the ion source directly affects the ion movement rate. The time for the ions to move in the edge field is: Where L is the length of the edge field, v is the ion movement velocity, E is the ion kinetic energy, m is the ion mass, e is the unit charge carried by the ion, and U is the potential difference between the ion and the ground when it leaves the ion source.

6. A field axis deceleration method for improving ion transmission rate according to claim 5, characterized in that: Before the field axis deceleration method was adopted, E was 10 eV, marked as E1; After using the field axis deceleration method, E increases to (100-200) eV, marked as E2 = 100 eV. For ions with the same mass-to-charge ratio, After adopting the field axis deceleration method, the time that ions spend in the edge field is shortened to less than 1 / 3 of the original time, thereby reducing the scattering loss of ions in the edge field.

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