Time of flight mass spectrometer comprising a reflecting means which equalizes time of flight of ions having same mass to charge ratio

Claim 2

In a time of flight mass spectrometer, the combination comprising: a. ion producing means for producing ions and accelerating said ions in a predetermined direction; b. detecting means for detecting impinging ions; c. means defining a linear drift region providing an ion time dispersion according to the mass to charge ratio; and d. reflecting means including a plurality of grids for reflecting ions toward the detecting means after passing through at least one of said grids, said grids providing an ion reflecting and decelerating field the direction and magnitude of which lengthens the time of flight of ions of relatively high velocity more than ions of relatively low velocity, whereby ions of the same mass to charge ratio but different velocities have the same total time of flight from the instant of injection to detection.

Claim 3

Apparatus as in claim 1 wherein said reflecting means precedes said linear drift region.

Claim 4

Apparatus as in claim 1 wherein said linear drift region precedes said reflecting means.

Claim 5

Apparatus as in claim 1 wherein said linear drift region is divided into first and second portions, said first portion preceding said reflecting means and said second portion following said reflecting means.

Claim 6

Apparatus as in claim 3 wherein the ions move through the drift region toward the reflecting means at substantially constant velocity.

Claim 7

Apparatus as in claim 5 wherein the time of flight for an ion is substantially the total time of drift betweeN injection and detection plus the total time of deceleration in the reflecting means.

Claim 8

Apparatus as in claim 4 wherein the time of flight of ions is substantially the total drift time through both said drift region portions from injection to collection plus total time of deceleration in the reflecting means.

Claim 9

Apparatus as in claim 4 wherein the drift path of the ions through the second drift region portion is substantially equal in length to the drift path through the first mentioned drift region portion thereby shortening the overall dimension of said spectrometer.

Claim 10

Apparatus as in claim 1 wherein said grids are planar and positioned substantially transverse to the direction of drift whereby the path of each ion in said reflecting field is parabolic.

Claim 11

Apparatus as in claim 9 wherein the path of the ions entering the reflecting means is at an angle to the grids of said reflecting means.

Claim 12

Apparatus as in claim 1 wherein said ion producing means includes further means for producing a beam of energy for evaporation and ionization of a test specimen.

Claim 13

Apparatus as in claim 6 wherein the detecting means is immediately adjacent the reflecting means whereby the drift time is substantially the drift time from injection to the reflecting means plus total time of deceleration in the reflecting means.

Claim 14

Apparatus as in claim 12 wherein ions drift through the drift region along a substantially straight line and the reflecting means decelerating field is defined by two parallel grids which are inclined at a skew angle to the ion drift path whereby the ions enter the deceleration field at an acute angle of incidence.

Claim 15

Apparatus as in claim 13 wherein the angle of reflection of the ions from the reflecting means is equal to said angle of incidence, all ions enter the reflecting means at substantially the same point and all ions leave the reflecting means at substantially the same point, and said detecting means is located at said point of exit of said ions.

Claim 16

Apparatus as in claim 1 wherein said reflecting means comprises first, second, and third parallel grids adapted to be coupled to a source of voltage, said first and second grids providing a first electric field and said second and third grids providing a second electric field, said first electric field being insufficient to reflect said ions and said second electric field being sufficient to reflect said ions, said first and second electric fields providing a transit time of ions therein whereby the total transit time of ions from said ion producing means to said ion detecting means is invarient in both first and second order variations in the initial kinetic energy of ions produced by said ion producing means.

Claim 17

Apparatus as in claim 15 wherein the spacing between first and second grids being less than the spacing between said second and third grids.

Claim 18

Apparatus as in claim 15 and additionally including a source of voltage coupled to said third grid for preventing ions having energy greater than a predetermined amount from re-entering said first electric field.

Claim 19

Apparatus as in claim 1 wherein said detecting means includes fourth planar grid means coupled to a source of voltage for providing a voltage on said fourth grid means for preventing ions reflected from the reflecting means and having energy less than a predetermined amount from being detected.

Claim 20

In a method for determining the mass to charge ratio of ions by measuring the time of flight of said ions the steps comprising: a. accelerating bunches of said ions at intervals through a controlled first electric field; b. causing said bunches of accelerated ions to sequentially pass through a field free region wherein said ions travel at a constant velocity; c. providing a second electric field having a direction and magnitude for receiving and reflecting said accelerated ions; d. causing said accelerated ions to enter said second field at an acute angle of incidence measured between the direCtion of motion of said ions and the direction of said second electric field; e. providing a direction and magnitude of said second electric field causing said ions to be reflected back out at an acute angle of reflection substantially equal to the said angle of incidence and to travel a distance within said field substantially proportional to ion velocity upon entering said second field whereby said ions of the same charge to mass ratio but of different velocities have the same total time of flight; and f. collecting and detecting said ions reflected by said second field, whereby the total time of flight of an ion is substantially the time of drift plus the time of reflection.

Claim 21

In a method for determining the mass to charge ratio of ions by measuring the time of flight of said ions the steps comprising: a. accelerating bunches of said ions at intervals through a controlled first electric field; b. causing said bunches of accelerated ions to sequentially pass through a field free region wherein said ions travel at a constant velocity; c. providing a second electric field having a direction and magnitude for receiving and reflecting said accelerated ions; d. causing said accelerated ions to enter said second field at an acute angle of incidence measured between the direCtion of motion of said ions and the direction of said second electric field; e. providing a direction and magnitude of said second electric field causing said ions to be reflected back out at an acute angle of reflection substantially equal to the said angle of incidence and to travel a distance within said field substantially proportional to ion velocity upon entering said second field whereby said ions of the same charge to mass ratio but of different velocities have the same total time of flight; and f. collecting and detecting said ions reflected by said second field, whereby the total time of flight of an ion is substantially the time of drift plus the time of reflection.

Claim 22

A method as in claim 19 in which said accelerated ions pass through said field free drift region prior to entering said second electric field.

Claim 23

A method as in claim 19 in which said accelerated ions pass through said second electric field prior to entering said field free drift region.

Claim 24

A method as in claim 20 in which said accelerated ions pass through a second field free drift region after passing through said second electric field and prior to said collection and detection whereby the total time of flight of an ion is substantially the total time of drift before and after reflection plus the time of reflection.

Claim 25

A method as in claim 22 and in which the drift times before and after reflection are substantially equal.

Claim 26

A method as in claim 19 and additionally including the step of passing said accelerated ions through a third electric field for absorbing ions having energy greater than a predetermined amount.

Claim 27

A method as in claim 24 and additionally including the step of passing said reflected ions through a fourth electric field rejecting ions having energy less than a predetermined amount.

Claim 28

A method as in claim 19 wherein said second electric field is adjusted to absorb ions having energy greater than a predetermined amount whereby only ions of less than a predetermined energy level are reflected, collected, and detected.

Claim 29

A method as in claim 19 wherein said collector is adjusted to absorb ions having energy less than a predetermined amount whereby only ions of greater than a predetermined energy level are detected.