# US 6,293,406 B1 · Multi-mass filter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,293,406 B1 - Document ID: US6293406B1 - Status: Granted - Kind: B1 - Application number: 09/643,204 - Filed: 2000-08-21 - Granted: 2001-09-25 - Earliest claimed: 2000-08-21 - Assignees: Archimedes Technology Group, Inc. - Inventors: Robert L. Miller; Tihiro Ohkawa; Richard L. Freeman - Web page: https://patentgrep.com/patent/US6293406B1 ## CPC - H01J 49/28: Static spectrometers - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract A multi-mass filter for separating particles according to their mass-charge ratio includes a chamber for receiving a multi-species plasma that includes particles therein having different mass-charge ratios (with M1Mc3) and only the intermediate particles M2 are ejected into the second region (M2>Mc2). In another embodiment, the radial electrical field is increased outwardly from the axis to a radial distance a2 (r2) at a first rate. The electrical field is then increased radially outward between a2 (r2) and a radial distance a3 (r3) at a lower rate. This electric field configuration defines the first region between the axis and a2 (r2), and the second region between a2 (r2) and a3 (r3). The third region is located radially beyond the second region. Accordingly, with Mc2=er22B2/(8*(Vctr−V2)) and Mc3=e(r32−r22)B2/(8*V2), particles M1 are confined in the first region, while both particles M3 and M2 are ejected from the first region into the second region. The particles M2 are, however, confined in the second region and only the particles M3 are ejected from the second region into the third region. ## Claims ### Claim 1 A multi-mass filter for separating particles according to mass which comprises: a chamber defining an axis and having a chamber wall; a means for providing a multi-species plasma in said chamber, said multi-species plasma including particles of relatively low mass-charge ratio (M1), particles of intermediate mass-charge ratio (M2), and particles of relatively high mass-charge ratio (M3), said multi-species plasma having a density in said chamber less than a predetermined collisional density; a means for generating an electrical field (E) wherein said electric field (E) increases radially from said axis and is generated with a positive voltage Vctr along said axis to extend said electric field (E) substantially radially therefrom, with “az” representing a radial distance from said axis at an axial “z” location, with “Bz” representing a magnetic field strength at an axial “z” location, and with “e” representing a positive ion charge; a first magnetic means and a second magnetic means for crossing said electric field with respective magnetic fields (E×B) in said chamber to establish respective first trajectories for each of said particles (M1), second trajectories for each of said particles (M2), said third trajectories for each of said particles (M3), and to respectively direct each said particle (M1) on its said first trajectory from said chamber into a first region, to direct each said particle (M2) on its said second trajectory from said chamber into a second region, and to direct each said particle (M3) on its said third trajectory from said chamber into a third region on said chamber wall to separate said particles (M1, M2 and M3) according to mass-charge ratio; and a control means for activating said first magnetic means and said second magnetic means to maintain az2Bz substantially constant along said axis with said first magnetic means establishing a cut-off mass Mc3=ea32B3/(8*Vctr), with M3 being greater than Mc3 to eject substantially only said particles M3 from said chamber into said third region and said second magnetic means establishing a cut-off mass Mc2=ea22B2/8*Vctr), with M2 being greater than Mc2 to eject substantially only said particles M2 from said chamber into said second region. ### Claim 2 (depends on 1) A filter as recited in claim 1 wherein said particles M1, M2 and M3, have a collision frequency, νcol, and respective cyclotron frequencies ωm1, ωm2 and ωm3, and wherein ωm1>ωm2>ωm3>νcol with said predetermined collisional density being defined when a ratio between ωm3 and said collision frequency is greater than one (ωm3/νcol>1). ### Claim 3 (depends on 1) A filter as recited in claim 1 wherein said chamber has a first end and a second end and wherein said multi-species plasma is initially provided in said chamber at a location substantially midway between said first end and said second end. ### Claim 4 (depends on 1) A multi-mass filter as recited in claim 1 wherein said first magnetic means comprises at least one magnetic coil mounted in a plane substantially perpendicular to said axis and said second magnetic means comprises at least one magnetic coil mounted in a plane substantially perpendicular to said axis. ### Claim 5 (depends on 4) A multi-mass filter as recited in claim 4 wherein a3 (r3) is less than a2 (r2) and B3 is greater than B2. ### Claim 6 A method of separating particles according to mass which comprises the steps of: providing a multi-species plasma in a chamber having a chamber wall, said multi-species plasma being below a predetermined collisional density and including particles of relatively low mass-charge ratio (M1), particles of intermediate mass-charge ratio (M2), and particles of relatively high mass-charge ratio (M3), wherein said particles M1, M2 and M3, have a collision frequency, νcol, and respective cyclotron frequencies ωm1, ωm2 and ωm3, and wherein ωm1>ωm2>ωm3>νcol with said predetermined collisional density being defined when a ratio between ωm3 and said collision frequency is greater than one (ωm3/νcol>1); generating an electric field wherein said chamber defines an axis, and wherein said electric field (E) increases radially from said axis and is generated with a positive voltage Vctr along said axis to extend said electric field (E) substantially radially therefrom, with “az” representing a radial distance from said axis at an axial “z” location, with “Bz” representing a magnetic field strength at an axial “z” location, and with “e” representing a positive ion charge; using a first magnetic means and a second magnetic means to configure said electric field crossed with respective magnetic fields (E×B) in said chamber to establish respective first trajectories for each of said particles (M1), second trajectories for each of said particles (M2), and third trajectories for each of said particles (M3), and to respectively direct each said particle (M1) on its said first trajectory from said chamber into a first region, to direct each said particle (M2) on its said second trajectory from said chamber into a second region, and to direct each said particle (M3) on its said third trajectory from said chamber into a third region on said chamber wall to separate said particles (M1, M2 and M3) according to mass; and activating said first magnetic means and said second magnetic means to maintain az2Bz substantially constant along said axis with said first magnetic means establishing a cut-off mass Mc3=ea32B3/(8*Vctr), with M3 being greater than Mc3 to eject substantially only said particles M3 from said chamber into said third region and said second magnetic means establishing a cut-off mass Mc2=ea22B2/(8*Vctr), with M2 being greater than Mc2 to eject substantially only said particles M2 from said chamber into said second region. ### Claim 7 A multi-mass filter for separating particles according to mass which comprises: a chamber having a chamber wall; a means for providing a multi-species plasma in said chamber, said multi-species plasma including particles of relatively low mass-charge ratio (M1), particles of intermediate mass-charge ratio (M2), and particles of relatively high mass-charge ratio (M3), said multi-species plasma having a density in said chamber less than a predetermined collisional density; a means for generating an electric field (E); and a first magnetic means and a second magnetic means for generating respective magnetic fields to cross with said electric field in said chamber to establish respective first trajectories for each of said particles (M1), second trajectories for each of said particles (M2), and third trajectories for each of said particles (M3), and to respectively direct each said particle (M1) on its said first trajectory from said chamber into a first region, to direct each said particle (M2) on its said second trajectory from said chamber into a second region on said chamber wall, and to direct each said particle (M3) on its said third trajectory from said chamber into a third region on said chamber wall to separate said particles (M1, M2 and M3) according to mass-charge ratio. ### Claim 8 (depends on 7) A multi-mass filter as recited in claim 7 wherein said chamber defines an axis and said electric field (E) increases radially from said axis and is generated with a positive voltage Vctr along said axis to extend said electric field (E) substantially radially therefrom, with “az” representing a radial distance from said axis at an axial “z” location, with “Bz” representing a magnetic field strength at an axial “z” location, and with “e” representing a positive ion charge. ### Claim 9 (depends on 8) A multi-mass filter as recited in claim 8 further comprises a control means for activating said first magnetic means and said second magnetic means to maintain az2Bz substantially constant along said axis with said first magnetic means establishing a cut-off mass Mc3=ea32B3/(8*Vctr), with M3 being greater than Mc3 to eject substantially only said particles M3 from said chamber into said third region and said second magnetic means establishing a cut-off mass Mc2=ea22B2/(8*Vctr), with M2 being greater than Mc2 to eject substantially only said particles M2 from said chamber into said second region. ### Claim 10 (depends on 7) A multi-mass filter as recited in claim 7 wherein said particles M1, M2 and M3, have a collision frequency, νcol, and respective cyclotron frequencies ωm1, ωm2 and ωm3, and wherein ωm1>ωm2>ωm3>νcol with said predetermined collisional density being defined when a ratio between ωm3 and said collision frequency is greater than one (ωm3/νcol>1). ### Claim 11 (depends on 7) A multi-mass filter as recited in claim 7 wherein said chamber has a first end and a second end and wherein said multi-species plasma is initially provided in said chamber at a location substantially midway between said first end and said second end. ### Claim 12 (depends on 7) A multi-mass filter as recited in claim 7 wherein said first magnetic means comprises at least one magnetic coil mounted in a plane substantially perpendicular to said axis and said second magnetic means comprises at least one magnetic coil mounted in a plane substantially perpendicular to said axis. ### Claim 13 (depends on 12) A multi-mass filter as recited in claim 12 wherein a3 (r3) is less than a2 (r2) and B3 is greater than B2.