# US 7,608,817 B2 · Adiabatically-tuned linear ion trap with fourier transform mass spectrometry with reduced packet coalescence

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- Number: US 7,608,817 B2
- Document ID: US7608817B2
- Status: Granted
- Kind: B2
- Application number: 11/780,667
- Filed: 2007-07-20
- Published: 2009-01-22
- Granted: 2009-10-27
- Earliest claimed: 2007-07-20
- Assignees: Agilent Technologies, Inc.
- Inventors: Curt Alan Flory
- Web page: https://patentgrep.com/patent/US7608817B2

## CPC

- H01J 49/4245: {Electrostatic ion traps (H01J49/422 takes precedence)}
- H01J 49/027: {detecting image current induced by the movement of charged particles (H01J49/38 takes precedence)}
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

A linear ion trap traps a plurality of charged particles in a charged particle trap including first and second electrode mirrors arranged along an axis at opposite ends of the particle trap, the electrode mirrors being capable, when voltage is applied thereto, of creating respective electric fields configured to reflect charged particles causing oscillation of the particles between the mirrors. The method includes: (a) introducing into the charged particle trap the plurality of charged particles, the particles having a spread in the oscillation time of the particles per oscillation; (b) applying voltage to the electrode mirrors during step (a) to induce a relatively weak self-bunching of the charged particles; and (c) after the plurality of charged particles has been introduced into the charged particle trap, waiting for a time period ΔT and then changing the voltage so as to induce a relatively stronger self-bunching among the charged particles.

## Claims

### Claim 1

A method of trapping a plurality of charged particles in a charged particle trap including first and second electrode mirrors arranged along an axis at opposite ends of the particle trap, the electrode mirrors being capable, when voltage is applied thereto, of creating respective electric fields configured to reflect charged particles causing oscillation of the particles between the mirrors, said method comprising the steps of:
(a) introducing into the charged particle trap the plurality of charged particles, the particles having a spread in the oscillation time of the particles per oscillation;
(b) applying voltage to the first and second electrode mirrors during step (a) to induce a relatively weak self-bunching of the charged particles; and
(c) after the plurality of charged particles has been introduced into the charged particle trap, waiting for a time period ΔT and then after the time period ΔT has expired, changing the voltage applied to the first and second electrode mirrors so as to induce a relatively stronger self-bunching among the charged particles.

### Claim 2 (depends on 1)

The method of claim 1, where ΔT corresponds to M cycles of oscillation of the slowest charged particles in the charged particle trap, where M>1.

### Claim 3 (depends on 1)

The method of claim 1, wherein the voltage is changed over a period corresponding to N cycles of oscillation of the slowest charged particles in the charged particle trap, where N>1.

### Claim 4 (depends on 3)

The method of claim 3, wherein M is about 100.

### Claim 5 (depends on 3)

The method of claim 3, wherein M is at least 10.

### Claim 6 (depends on 3)

The method of claim 3, wherein N≧100.

### Claim 7 (depends on 3)

The method of claim 3, wherein N is about 400.

### Claim 8 (depends on 1)

The method of claim 1, wherein the step of changing the voltage comprises continuously decreasing the voltage linearly over a period of time.

### Claim 9 (depends on 1)

The method of claim 1, wherein the voltage produces a potential distribution, V(z), along the axis at a distance z from a midpoint between the first and second electrode mirrors:
V
⁡
(
z
)
=
{
0
if
⁢
⁢

z

≤
L
/
2
⁢
(

z

-
L
/
2
)
if
⁢
⁢

z

>
L
/
2
where
=
K
⁡
(
1
-
α
)
(
1
+
α
)
,
and where K is a selected value, and wherein changing the voltage applied to the first and second electrode mirrors comprises changing a value of α.

### Claim 10 (depends on 9)

The method of claim 9, wherein α is set to 0 during steps (a) and (b) and during the a time period ΔT, and wherein changing the voltage applied to the first and second electrode mirrors so as to induce a relatively stronger self-bunching among the charged particles comprises increasing α to a value≦1.

### Claim 11

A device, comprising:
first and second electrode mirrors disposed along an axis to define a charged particle trap, the charged particle trap being adapted to have charged particles introduced therein;
a charge-sensing element disposed between the first and second electrode mirrors to output a signal based on a net charge from charged particles in a vicinity thereof, and
a voltage generator configured to apply voltage to the first and second electrode mirrors,
wherein the voltage generator is configured to apply voltage to the first and second electrode mirrors to induce a relatively weak self-bunching of the charged particles when the charged particles are initially introduced into the charged particle trap and for a time period ΔT thereafter, and then after the period ΔT to change the voltage applied to the first and second electrode mirrors so as to induce a relatively stronger self-bunching among the charged particles.

### Claim 12 (depends on 11)

The device of claim 11, where ΔT corresponds to M cycles of oscillation of the slowest charged particles in the charged particle trap, where M>1.

### Claim 13 (depends on 12)

The device of claim 12, wherein M is at least 10.

### Claim 14 (depends on 12)

The device of claim 12, wherein M is about 100.

### Claim 15 (depends on 11)

The device of claim 11, wherein the voltage generator is adapted to change the voltage applied to the first and second electrode mirrors over a period corresponding to N cycles of oscillation of the slowest charged particles in the charged particle trap, where N>1.

### Claim 16 (depends on 15)

The device of claim 15, wherein N≧100.

### Claim 17 (depends on 15)

The device of claim 15, wherein N is about 400.

### Claim 18 (depends on 11)

The device of claim 11, wherein the voltage generator is adapted to continuously decrease the voltage linearly over a period of time.

### Claim 19 (depends on 11)

The device of claim 11, wherein the voltage produces a potential distribution, V(z), along the axis at a distance z from a midpoint between the first and second electrode mirrors:
V
⁡
(
z
)
=
{
0
if
⁢
⁢

z

≤
L
/
2
⁢
(

z

-
L
/
2
)
if
⁢
⁢

z

>
L
/
2
where
=
K
⁡
(
1
-
α
)
(
1
+
α
)
,
and where K is a selected value.

### Claim 20 (depends on 19)

The device of claim 19, wherein α is set to 0 during steps (a) and (b) and during the a time period ΔT, and wherein changing the voltage applied to the first and second electrode mirrors so as to induce a relatively stronger self-bunching among the charged particles comprises increasing α to a value≦1.

### Claim 21 (depends on 11)

The device of claim 11, further comprising a controller adapted to control the voltage generator to change the voltage applied to the first and second electrode mirrors over a period corresponding to N cycles of oscillation of the slowest charged particles in the charged particle trap, where N>1.

### Claim 22 (depends on 21)

The device of claim 21, wherein the controller is further adapted to control the introduction of the charged particles into the charged particle trap.