GB1567151A - Deflection of ion beams by electrostatic mirror apparatus - Google Patents
Deflection of ion beams by electrostatic mirror apparatus Download PDFInfo
- Publication number
- GB1567151A GB1567151A GB3380575A GB3380575A GB1567151A GB 1567151 A GB1567151 A GB 1567151A GB 3380575 A GB3380575 A GB 3380575A GB 3380575 A GB3380575 A GB 3380575A GB 1567151 A GB1567151 A GB 1567151A
- Authority
- GB
- United Kingdom
- Prior art keywords
- electrode
- mirror
- electrodes
- ion beam
- electrostatic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000010884 ion-beam technique Methods 0.000 title claims description 38
- 239000002184 metal Substances 0.000 claims description 12
- 230000000694 effects Effects 0.000 claims description 7
- 150000002500 ions Chemical class 0.000 claims description 7
- 239000012212 insulator Substances 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 6
- 230000005686 electrostatic field Effects 0.000 claims description 5
- 229910052582 BN Inorganic materials 0.000 claims description 2
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims description 2
- 230000035515 penetration Effects 0.000 claims description 2
- 238000000605 extraction Methods 0.000 description 5
- 238000004364 calculation method Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 238000005421 electrostatic potential Methods 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000013507 mapping Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/02—Details
- H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
- H01J37/147—Arrangements for directing or deflecting the discharge along a desired path
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J3/00—Details of electron-optical or ion-optical arrangements or of ion traps common to two or more basic types of discharge tubes or lamps
- H01J3/14—Arrangements for focusing or reflecting ray or beam
- H01J3/16—Mirrors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/15—Means for deflecting or directing discharge
- H01J2237/151—Electrostatic means
Landscapes
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Physical Vapour Deposition (AREA)
Description
(54) IMPROVEMENTS IN OR RELATING TO
THE DEFLECTION OF ION BEAMS BY
ELECTROSTATIC MIRROR APPARATUS
(71) We UNITED KINGDOM ATOMIC
ENERGY ATHORITY, London, a British
Authority do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it ns to be performed, to be particularly described in and by the following statement:
The invention relates to the deflection of ion beams by electrostatic mirror apparatus.
The invention provides an electrostatic mirror apparatus for deflection of a positive ion beam, which apparatus comprises an evacuable enclosure through which the ion beam passes, front, intermediate and rear electrodes each formed of sheet or mesh material and spaced apart in a direction generally transverse to the electrode surfaces, the front and intermediate electrodes being relatively close together and apertured for passage therethrough of the ion beam into and out from the mirror space between the intermediate electrode and the rear electrode, means for holding the front electrode at substantially the same electrical potential as the said enclosure through which the ion beam passes, means for applying to the intermediate electrode an electrical potential which is negative with respect to the front electrode, and means for applying to the rear electrode an electrical potential which is positive with respect to the front electrode and effects the desired deflection of the ion beam as it passes through the mirror space.
In one arrangement according to the invention at least the rear electrode conforms to a curved surface to shape correspondingly the electrostatic field formed in the mirror space between the electrodes when, in operation of the system, the appropriate electrical potentials are applied to the electrodes.
The apertured electrodes may be in the form of a mesh to permit the ion beam to enter into and exit from the mirror space.
However, it is preferred that the electrodes are formed of sheet material and the apertures are slots provided at predetermined locations where the beam enters into and exits from the mirror space.
In a preferred arrangement according to the invention the front apertured electrode extends to the walls of said enclosure to avoid fringing penetration of electrostatic field from the mirror space side of the said front apertured electrode into the enclosure on the other side thereof.
The invention also provides a method of effecting a scanning deflection of a beam of ions which method comprises deflecting the beam by an electrostatic mirror apparatus as aforesaid and varying the relative electrical potential of the rear electrode with respect to the front electrode of the apparatus.
Specific constructions of electrostatic mirror apparatus and methods of operation embodying the invention will now be described by way of example and with reference to the drawings (Figures 1 to 10) filed with the Provisional Specification and the drawings (Figure 11) filed herewith, in which:
Figures 1 to 4 show electrodes in transverse section and ion beam trajectories derived from simulation of the electrode apparatus on a digital computer, using a field mapping and ray tracing programme;
Figures 5 to 7 show electrodes in transverse section of a three electrode apparatus and illustrate ion and electron trajectories in such an apparatus::
Figures 8, 9 and 10 illustrate the effect upon an ion beam of varying the electrostatic potential applied to the third electrode of a three electrode apparatus;
and Figure 11 is a cross-sectional view showing structural features of a three electrode apparatus.
Electrostatic mirror apparatus compris ing simply two spaced, parallel, planar electrodes for the deflection, focussing and energy analysis of both electron and ion beams are known. The front electrode is either a mesh or a plate with input and output apertures.
In Figures 1 to 4, two electrode mirror apparatus is shown in which at least one of the electrodes is curved. In Figures 1 to 4, the front electrode 11 is apertured at 12, 13 to permit passage of ion beam 14 into the mirror space between the electrodes. The front electrode 11 is held at earth potential and the rear electrode 15 is held at a potential sufficient to effect the desired reflection. In the examples shown in Figures 1 and 2 the beam energy is 30 kV. In the examples shown in Figures 3 and 4 the corresponding beam energy and rear electrode potential are 29 kV.
Shaping of the electrodes may be applied in either one or both planes, the Figures show analysis of curvature in only one plane. Figure 1 shows curved electrodes refocussing at 16 a beam which enters the mirror from a focus at 17.
In Figure 2, electrodes of different curvature bring a slightly converging beam to a sharp focus at 18, after deflection through the mirror.
In Figure 3, a parabolic rear electrode 15 with a plane mesh, front electrode 11 forms a converging beam into a parallel beam.
Figure 4 shows the deflection of a divergent beam to a parallel beam by a hyperbolic rear electrode 15, again with a plane mesh front electrode 11.
A disadvantage of a simple two electrode electrostatic mirror apparatus is that the earthed front electrode is not adequate to prevent extraction of electrons from a space charge neutralised ion beam, the electron extraction effect extending well beyond the front electrode. This stripping of electrons from an ion beam leads to beam defocussing, because of the repulsion between like positively charged ions. It is therefore very desirable to limit the length of beam over which the mirror system extracts electrons.
Figures 5 to 7 illustrate a three electrode apparatus in which electron extraction can be effectively limited to that part of the beam which is within the mirror space.
These Figures show a simple plane electrode configuration with a rear electrode 21, to which the mirror potential is applied positive for reflecting a positive ion beam an apertured front electrode 22, held at earth potential and an apertured intermediate electrode 23, By applying a negative potential to the intermediate electrode 23, extraction of electrons to the rear electrode 21 from the region outside the mirror can be reduced or prevented. This is illustrated by computed electron trajectories illustrated at 24 in Figure 5. In the example electron energy of 0.1 KeV is assumed and the electrode potentials are respectively 0, -2kV, and +30kV for front (22), intermediate (23) and rear (21) electrodes.
Figure 6 shows the importance of correct dimensions of the aperture in the intermediate electrode, in that a larger aperture, given the same electrode potentials and electron energy, is ineffective to prevent extraction of the electrons 24 to the positive rear electrode 21. Increase in aperture may be compensated, at least to some extent, by increasing the magnitude of the negative potential applied to the intermediate electrode 23.
Figure 7 illustrates an example of ion trajectories 25 for a simple parallel plane electrode configuration but with the intermediate negative electrode. The ion energy is 30kV and the potentials on the electrodes are respectively front 0V, intermediate -2kV, rear +30kV.
Figures 8 to 10 illustrate the capability for scanning an ion beam by varying the potential applied to the rear electrode of the mirror system. Figure 8 is a graph showing the displacement of the exit beam as a function of the ratio of the energy of the charged particle to the mirror potential.
Figure 9 and 10 illustrate the change in position of the exit beam as the above defined ratio is changed. The change in position is marked at 31 where the central exiting ray crosses the ordinate. For convenience in computing, the mirror potential in the calculations is maintained constant and the input ion beam energy is varied -from 29.6 kV in Figure 9 to 30.39 kV in Figure 10. This is equivalent to maintaining a constant ion energy and applying a small scanning voltage to the mirror potential.
It will be appreciated that the principles of curvature of electrodes illustrated in
Figures 1 to 4 may be applied to a three electrode apparatus according to the invention, thereby reducing the effects of stripping of electrons from the ion beam.
Figure 11 is a cross-sectional view showing details of the structure of a plane three electrode mirror apparatus 41 mounted for ready insertion into the beam tube of an electromagnetic separator, such as is described in Patent Specification No. 1 280 011.
The three electrodes comprise an earthed front electrode 42, an intermediate electrode 43 close to the front electrode 42 and a third, reflector electrode 44. In this example, the reflector electrode 44 is spaced 2.0 centimetres from the front electrode 42 and is mounted on a cylindrical, metal block 45. A leadthrough metal rod 46 provides both mechanical support and electrical connection for the reflector electrode. The rod 46 is received in a bore 47 in the block 45, which is adjustably clamped to the rod 46 by a nut 48 cooperating with an axially extending slot in the block 45. In this way, the position of the reflector electrode 44 can be adjusted.
The rod 46 is located in an insulator 49 which is clamped to flange plate 51, by which this part of the apparatus is mounted in the beam tube. Hollow cylindrical shields 52 and 53 overlap in the manner of a tele
scope but are spaced from one another, the inner shield 52 being an earthed shield attached to the flange plate 51. The outer shield 53 is attached to the reflector electrode 44 and thus takes the potential of this electrode.
The front electrode 42 and intermediate electrode 43 are supported together from a metal tube (not shown) clamped to another flange plate (not shown). The metal tube extends at right angles from the electrode support assembly 54 and provides access for electrical supply to the intermediate electrode 43 insulated from the earthed front electrode 42.
The intermediate electrode is mounted on an electrical socket member 55 which is a push fit onto an intermediate electrode voltage supply pin 56 forming part of a terminal mounting 57 in a boron nitride insulator 58. The insulator 58 is itself a push fit within a cylindrical metal sleeve 59 forming the exterior of the support assembly 54 and connected mechanically and electrically to the front electrode 42.
The intermediate electrode 43 is thus supported close to, but electrically insulated from, the front electrode 42. The voltage supply to the intermediate electrode is brought through the interior of the support assembly 54. The front electrode is earthed by the connection through the metal sleeve 59 and the metal tube (not shown) to the flange plate bolted to the side of the beam tube.
The front electrode 42 and intermediate electrode 43 are each provided with accurately positioned apertures; an entrance aperture 61 and an exit aperture 62 for passage of the ion beam into and out from the mirror space.
The foregoing references to the beam tube and the front electrode being "earthed" are based upon the usual arrangement in which the beam tube is indeed earthed according to the strict meaning of the word. However, it will be appreciated that it is possible for the whole system to be held at some specified potential relative to earth. The essential requirement so far as operation of the mirror apparatus of the foregoing example is concerned is that the front electrode should be at substantially the same potential as the beam tube.
The operation of the mirror apparatus is
then determined by the potentials of the other two electrodes relative to that of the front electrode.
With this apparatus, ion beams of intensity greater than 100 microamps in an
electromagnetic separator have been turned
through 90".
ln such apparatus it has been observed that high beam currents can cause the ion beam to "blow up" (i.e. expand) as it enters the mirror space and then be focused down on exit to a beam narrower than that incident upon the mirror apparatus.
The invention is not restricted to the details of the foregoing example. For instance, two mirror apparatus operating sequentially upon an ion beam and turning the beam through 90 can be arranged to displace the beam laterally, without changing the final direction of the beam.
WHAT WE CLAIM IS:
1. An electrostatic mirror apparatus for deflection of a positive ion beam, which apparatus comprises an evacuable enclosure through which the ion beam passes, front, intermediate and rear electrodes each formed of sheet or mesh material and spaced apart in a direction generally transverse to the electrode surfaces, the front and intermediate electrodes being relatively close together and apertured for passage therethrough of the ion beam into and out from the mirror space between the intermediate electrode and the rear electrode, means for holding the front electrode at substantially the same electrical potential as the said enclosure through which the ion beam passes, means for applying to the intermediate electrode an electrical potential which is negative with respect to the front electrode, and means for applying to the rear electrode an electrical potential which is positive with respect to the front electrode and effects the desired deflection of the ion beam as it passes through the mirror space.
2. An electrostatic mirror apparatus as claimed in Claim 1, wherein at least the rear electrode conforms to a curved surface to shape correspondingly the electrostatic field formed in the mirror space between the electrodes when, in operation of the system, the appropriate electrical potentials are applied to the electrodes.
3. An electrostatic mirror apparatus as claimed in Claim 1 or Claim 2, wherein the apertured electrodes are in the form of a mesh to permit the ion beam to enter into an exit from the mirror space.
4. An electrostatic mirror apparatus as claimed in Claim 1 or Claim 2, wherein the electrodes are formed of sheet material and
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (9)
- **WARNING** start of CLMS field may overlap end of DESC **.46 provides both mechanical support and electrical connection for the reflector electrode. The rod 46 is received in a bore 47 in the block 45, which is adjustably clamped to the rod 46 by a nut 48 cooperating with an axially extending slot in the block 45. In this way, the position of the reflector electrode 44 can be adjusted.The rod 46 is located in an insulator 49 which is clamped to flange plate 51, by which this part of the apparatus is mounted in the beam tube. Hollow cylindrical shields 52 and 53 overlap in the manner of a tele scope but are spaced from one another, the inner shield 52 being an earthed shield attached to the flange plate 51. The outer shield 53 is attached to the reflector electrode 44 and thus takes the potential of this electrode.The front electrode 42 and intermediate electrode 43 are supported together from a metal tube (not shown) clamped to another flange plate (not shown). The metal tube extends at right angles from the electrode support assembly 54 and provides access for electrical supply to the intermediate electrode 43 insulated from the earthed front electrode 42.The intermediate electrode is mounted on an electrical socket member 55 which is a push fit onto an intermediate electrode voltage supply pin 56 forming part of a terminal mounting 57 in a boron nitride insulator 58. The insulator 58 is itself a push fit within a cylindrical metal sleeve 59 forming the exterior of the support assembly 54 and connected mechanically and electrically to the front electrode 42.The intermediate electrode 43 is thus supported close to, but electrically insulated from, the front electrode 42. The voltage supply to the intermediate electrode is brought through the interior of the support assembly 54. The front electrode is earthed by the connection through the metal sleeve 59 and the metal tube (not shown) to the flange plate bolted to the side of the beam tube.The front electrode 42 and intermediate electrode 43 are each provided with accurately positioned apertures; an entrance aperture 61 and an exit aperture 62 for passage of the ion beam into and out from the mirror space.The foregoing references to the beam tube and the front electrode being "earthed" are based upon the usual arrangement in which the beam tube is indeed earthed according to the strict meaning of the word. However, it will be appreciated that it is possible for the whole system to be held at some specified potential relative to earth. The essential requirement so far as operation of the mirror apparatus of the foregoing example is concerned is that the front electrode should be at substantially the same potential as the beam tube.The operation of the mirror apparatus is then determined by the potentials of the other two electrodes relative to that of the front electrode.With this apparatus, ion beams of intensity greater than 100 microamps in an electromagnetic separator have been turned through 90".ln such apparatus it has been observed that high beam currents can cause the ion beam to "blow up" (i.e. expand) as it enters the mirror space and then be focused down on exit to a beam narrower than that incident upon the mirror apparatus.The invention is not restricted to the details of the foregoing example. For instance, two mirror apparatus operating sequentially upon an ion beam and turning the beam through 90 can be arranged to displace the beam laterally, without changing the final direction of the beam.WHAT WE CLAIM IS: 1. An electrostatic mirror apparatus for deflection of a positive ion beam, which apparatus comprises an evacuable enclosure through which the ion beam passes, front, intermediate and rear electrodes each formed of sheet or mesh material and spaced apart in a direction generally transverse to the electrode surfaces, the front and intermediate electrodes being relatively close together and apertured for passage therethrough of the ion beam into and out from the mirror space between the intermediate electrode and the rear electrode, means for holding the front electrode at substantially the same electrical potential as the said enclosure through which the ion beam passes, means for applying to the intermediate electrode an electrical potential which is negative with respect to the front electrode, and means for applying to the rear electrode an electrical potential which is positive with respect to the front electrode and effects the desired deflection of the ion beam as it passes through the mirror space.
- 2. An electrostatic mirror apparatus as claimed in Claim 1, wherein at least the rear electrode conforms to a curved surface to shape correspondingly the electrostatic field formed in the mirror space between the electrodes when, in operation of the system, the appropriate electrical potentials are applied to the electrodes.
- 3. An electrostatic mirror apparatus as claimed in Claim 1 or Claim 2, wherein the apertured electrodes are in the form of a mesh to permit the ion beam to enter into an exit from the mirror space.
- 4. An electrostatic mirror apparatus as claimed in Claim 1 or Claim 2, wherein the electrodes are formed of sheet material andthe apertures in the apertured electrodes are slots provided at predetermined locations where the beam enters into and exits from the mirror space.
- 5. An electrostatic mirror apparatus as claimed in any of the preceding claims, wherein the front apertured electrode extends to the walls of the said enclosure to avoid fringing penetration of electrostatic field from the mirror space side of the said front apertured electrode into the enclosure on the other side thereof.
- 6. A method of effecting a scanning deflection of a beam of positive ions, which method comprises deflecting the beam of an electrostatic mirror apparatus as claimed in any of the preceding claims and varying the relative electrical potential of the rear electrode with respect to the front electrode of the apparatus.
- 7. An electrostatic mirror apparatus substantially as hereinbefore described with reference to, and illustrated in, Figures 5, 6, 7, 9 and 10 of the drawings filed with the Provisional Specification.
- 8. An electrostatic mirror apparatus substantially as hereinbefore described with reference to, and illustrated in, the drawing (Figure 11) filed herewith.
- 9. An electrostatic mirror apparatus as claimed in Claim 7 or Claim 8, modified to provide curved electrodes as described with reference to and as illustrated in Figures 1 to 4 of the drawings filed with the Provisional Specification.o r T T ZTL TP
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB3380575A GB1567151A (en) | 1976-11-12 | 1976-11-12 | Deflection of ion beams by electrostatic mirror apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB3380575A GB1567151A (en) | 1976-11-12 | 1976-11-12 | Deflection of ion beams by electrostatic mirror apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1567151A true GB1567151A (en) | 1980-05-14 |
Family
ID=10357676
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB3380575A Expired GB1567151A (en) | 1976-11-12 | 1976-11-12 | Deflection of ion beams by electrostatic mirror apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB1567151A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5077472A (en) * | 1989-07-12 | 1991-12-31 | Kratos Analytical Limited | Ion mirror for a time-of-flight mass spectrometer |
| WO2014009028A1 (en) * | 2012-07-07 | 2014-01-16 | Limo Patentverwaltung Gmbh & Co. Kg | Device for producing an electron beam |
| JP2017033874A (en) * | 2015-08-05 | 2017-02-09 | 株式会社島津製作所 | Time-of-flight mass spectrometer |
-
1976
- 1976-11-12 GB GB3380575A patent/GB1567151A/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5077472A (en) * | 1989-07-12 | 1991-12-31 | Kratos Analytical Limited | Ion mirror for a time-of-flight mass spectrometer |
| WO2014009028A1 (en) * | 2012-07-07 | 2014-01-16 | Limo Patentverwaltung Gmbh & Co. Kg | Device for producing an electron beam |
| US9773635B2 (en) | 2012-07-07 | 2017-09-26 | Lilas Gmbh | Device for producing an electron beam |
| JP2017033874A (en) * | 2015-08-05 | 2017-02-09 | 株式会社島津製作所 | Time-of-flight mass spectrometer |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4818872A (en) | Integrated charge neutralization and imaging system | |
| US6384410B1 (en) | Time-of-flight mass spectrometer | |
| US6717132B2 (en) | Gridless time-of-flight mass spectrometer for orthogonal ion injection | |
| US6380666B1 (en) | Time-of-flight mass spectrometer | |
| JPH07101602B2 (en) | Device for scanning a high current ion beam with a constant incident angle | |
| US4013891A (en) | Method for varying the diameter of a beam of charged particles | |
| EP0838080B1 (en) | Sample analyzer | |
| GB1594431A (en) | Flat panel display with beam injection cleanup | |
| US5045705A (en) | Charged particle beam apparatus with charge-up compensation | |
| EP0537961B1 (en) | Charged particle energy analysers | |
| JPS63308854A (en) | Ion source device | |
| GB1567151A (en) | Deflection of ion beams by electrostatic mirror apparatus | |
| GB1533526A (en) | Electro-static charged particle analyzers | |
| US2060825A (en) | Control of electron streams | |
| GB1226886A (en) | ||
| GB1078832A (en) | Electrostatic electron optical system | |
| US5247263A (en) | Injection system for tandem accelerators | |
| Freeman | Improvements in or relating to the deflection of ion beams by electrostatic mirror apparatus | |
| US2861208A (en) | Combination focusing and converging lens for multiple beam tubes | |
| JPS6217349B2 (en) | ||
| US4486687A (en) | Electron gun for convergent beam, and a device, particularly a vidicon tube, equipped with such a gun | |
| WO1994007258A3 (en) | Electron energy spectrometer | |
| JPS6347226B2 (en) | ||
| US3979626A (en) | Electrostatic focusing arrangements | |
| GB1018504A (en) | An arrangement for the production of neutron pulses |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| 746 | Register noted 'licences of right' (sect. 46/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |