Patent
Method and device for accurately measuring the incident flux of ambient particles in a high or ultra-high vacuum environment
| العنوان: | Method and device for accurately measuring the incident flux of ambient particles in a high or ultra-high vacuum environment |
|---|---|
| Patent Number: | 8,803,072 |
| تاريخ النشر: | August 12, 2014 |
| Appl. No: | 13/116982 |
| Application Filed: | May 26, 2011 |
| مستخلص: | An apparatus and method that can measure flux density in-situ under high vacuum conditions includes a means for confining a collection of identical, elemental sensor particles to a volume of space by initial cooling by laser or another method, then confinement in a sensor volume using externally applied magnetic and/or optical fields. |
| Inventors: | Booth, James Lawrence (Burnaby, CA); Fagnan, David Erik (Kitchener, CA); Klappauf, Bruce George (Vancouver, CA); Madison, Kirk William (Vancouver, CA); Wang, Jicheng (Harbin, CN) |
| Assignees: | British Columbia Institute of Technology (Burnaby, British Columbia, CA) |
| Claim: | 1. An apparatus which comprises: a) a sensor vacuum envelope; b) a means to introduce at least one sensor particle; c) a means to introduce said at least one sensor particle into the vacuum envelope; d) a means to cool and localize said at least one sensor particle; e) a means to transfer said at least one sensor particle into a sensor volume; f) a means to introduce particles to be measured into said vacuum envelope such that said particles to be measured interact with said at least one sensor particle; g) a means to measure a loss rate of said at least one sensor particle from the sensor volume; h) a means to determine trap depths at which the loss rate of said at least one sensor particle is measured; i) a means to determine a loss rate constant of said at least one sensor particle at known trap depths; and j) a means to determine incident particle flux based on said loss rate of said at least one sensor particle and said loss rate constant of said at least one sensor particle. |
| Claim: | 2. Apparatus according to claim 1 , wherein said sensor vacuum envelope is integrated together with the vacuum envelope under test. |
| Claim: | 3. Apparatus according to claim 1 , wherein said at least one sensor particle is an alkali-metal atom selected from the group consisting of lithium, sodium, potassium, rubidium, or cesium atoms. |
| Claim: | 4. Apparatus according to claim 1 , wherein said at least one sensor particle is introduced into the sensor volume by the use of an alkali-metal vaporizer to provide an alkali-metal vapor inside said sensor volume. |
| Claim: | 5. Apparatus according to claim 1 , wherein said means to cool and localize said at least one sensor particle further comprises a magneto-optic trap (MOT), comprising: a) a laser system and associated optics capable of delivering cooling radiation sufficient to Doppler cool said at least one sensor particle; b) a set of magnetic coils or permanent magnets arranged to provide a magnetic field gradient sufficient to complete the operation of the MOT providing both cooling and spatial confinement of said at least one sensor particle. |
| Claim: | 6. Apparatus according to claim 1 arranged such that said at least one sensor particle is transferred into a spatially localized sensor volume determined by a magnetic, electric, or electro-magnetic field generated by either a) a set of magnetic coils or a permanent magnet system in a proper arrangement to provide a magnetic field gradient sufficiently large to localize said at least one sensor particle to the sensor volume; or b) a laser system capable of delivering radiation sufficient to localize said at least one sensor particle to the sensor volume. |
| Claim: | 7. Apparatus according to claim 1 arranged such that said particles to be measured are allowed, by means of a vacuum valve, to enter into and impinge upon the sensor volume such that said particles to be measured interact with said at least one sensor particle. |
| Claim: | 8. Apparatus according to claim 1 arranged such that a number of said at least one sensor particle inside the sensor volume is measured by a fluorescence detection device comprising; a) a photodiode, photodetector, CCD camera, or CMOS camera; and b) a laser system and associated optics capable of delivering excitation radiation and collecting resulting fluorescence of said at least one sensor particle. |
| Claim: | 9. Apparatus of claim 5 wherein said laser system is arranged to provide near resonant light sufficient to excite said at least one sensor particle so that fluorescence of said at least one sensor particle is detectable. |
| Claim: | 10. Apparatus according to claim 1 , including a computer or electronic system to control and monitor said at least one sensor particle in the sensor volume. |
| Claim: | 11. The apparatus according to claim 1 , wherein the particles to be measured comprise atoms or molecules. |
| Claim: | 12. The apparatus according to claim 1 , wherein the said at least one sensor particle is comprised of either atoms or molecules. |
| Claim: | 13. The apparatus according to claim 1 , further comprising a means to determine, from the determined incident particle flux, a corresponding ambient density and corresponding pressure of said particles to be measured. |
| Claim: | 14. The apparatus according to claim 6 , arranged to localize said at least one sensor particle in the sensor volume using any combination of the electric, magnetic, and electro-magnetic fields. |
| Claim: | 15. A method for measuring the incident flux of particles in a vacuum environment, comprising: a) introducing at least one sensor particle into the test vacuum environment and a sensor volume; b) collecting and confining said at least one sensor particle inside the sensor volume; c) introducing a particle flux to be measured into the sensor volume; d) monitoring characteristics of said at least one sensor particle selected from the group consisting of a number of said at least one sensor particle and an internal state of said at least one sensor particle, within the sensor volume during a measurement time; e) measuring a rate of change of said characteristics of said at least one sensor particle; f) determining a sensor volume environment in which the rate of change of said characteristics of said at least one sensor particle is measured, the sensor volume environment being selected from the group consisting of electric, magnetic or electromagnetic fields of the sensor volume and trap depth of said at least one sensor particle; g) determining a rate-of-change constant of said characteristics of said at least one sensor particle for a state of said at least one sensor particle state and for the sensor volume environment; h) determining the incident flux based on the measured rate of change of said characteristic of said at least one sensor particle, the determined sensor volume environment, and the determined rate-of-change constant of said characteristic of said at least one sensor particle. |
| Claim: | 16. A method according to claim 15 , further comprising introducing said at least one sensor particle is into said sensor volume at a controlled rate such that said at least one sensor particle can be collected, cooled, and confined in a magneto-optic trap and transferred to the sensor volume environment. |
| Claim: | 17. A method according to claim 15 , further comprising temporarily isolating said at least one sensor particle in the sensor volume from a source of said at least one sensor particle and allowing said at least one sensor particle to interact with the particles to be measured. |
| Claim: | 18. A method according to claim 15 , further comprising measuring the characteristics of said at least one sensor particle by detecting intensity of resonance fluorescence from said at least one sensor particle during the measurement time or measured at the beginning and at the end of the measurement time. |
| Claim: | 19. A method according to claim 15 , further comprising determining the particle flux through the sensor volume from the change in the number or the internal state of any sensor particle remaining in the sensor volume, comprising: a) measuring the loss rate of or rate of change of the internal state of said at least one sensor particle in the sensor volume under different confinement conditions comprising different sensor volume environments including the trap depth for said at least one sensor particle; b) dividing the measured loss rate of or the rate of change of the internal state of said at least one sensor particle by the rate-of-change constant for the corresponding sensor volume environment, a type of said at least one sensor particle, and a particle species being measured; and c) inverting a set of linear equations for an expected loss rate or a rate of internal state change under different sensor volume environmental conditions given an incident particle flux comprised of a collection of different particle species. |
| Claim: | 20. The apparatus according to claim 15 , wherein the internal state of said at least one sensor particle is a momentum or a velocity of the sensor particle. |
| Claim: | 21. The apparatus according to claim 15 , wherein the internal state of said at least one sensor particle is one or more of an electronic orbital, an electronic spin, and a nuclear spin angular momentum of said at least one sensor particle. |
| Current U.S. Class: | 250/251 |
| Patent References Cited: | 5274231 December 1993 Chu et al. 7915577 March 2011 Fatemi et al. |
| Other References: | Matherson et al., Absolute metastable atom-atom collision cross section measurements using a magneto-optical trap, Review of Scientific Instruments, 78, 073102 (2007). cited by examiner Stanford Research Systems, Gas Correction Factors for Bayard-Alpert Ionization Gauges, Stanford Research Systems Application Notes, http://www.thinksrs.com/downloads/PDFs/ApplicationNotes/IG1BAgasapp.pdfTest. cited by applicant C. Monroe et al., Very Cold Trapped Atoms in a Vapor Cell, Physical Review Letters, Sep. 24, 1990, 1571-75, 65(13). cited by applicant C. R. Tilford et al., Comments on the Stability of Bayard-Alpert Ionization Gages, J. Vac. Sci. Technol. A, Mar.-Apr. 1995, 485-87, 13(2). cited by applicant D. E. Fagnan et al., Observation of Quantum Diffractive Collisions Using Shallow Atomic Traps, Physical Review A, 2009, 1-8, 80. cited by applicant D. G. Bills, Causes of Nonstability and Nonreproducibility in Widely Used Bayard-Alpert Ionization Gauges, J. Vac. Sci. Technol. A, Mar.-Apr. 1994, 574-79, 12(2). cited by applicant K. Jousten et al., Comparison of the Standards for High and Ultrahigh Vacuum at Three National Standards Laboratories, J. Vac. Sci. Technol. A, Jul.-Aug. 1997, 2395-406, 15(4). cited by applicant K. Matherson et al., Measurement of Low-Energy Total Absolute Atomic Collision Cross Sections with the Metastable 3P2 State of Neon Using a Magneto Optical Trap, Physical Review A, 2008, 1-5, 78. cited by applicant M. Prentiss et al., Atomic-Density-Dependent Losses in an Optical Trap, Optical Letters, Jun. 1988, 452-54, 13(6). cited by applicant P. C. Arnold et al., Stable and Reproducible Bayard-Alpert Ionization Gauge, J. Vac. Sci. Technol. A, Mar.-Apr. 1994, 580-86, 12(2). cited by applicant P. C. Arnold et al., Nonstable Behavior of Widely Used Ionization Gauges, J. Vac. Sci. Technol. A, Mar.-Apr. 1994, 568-73, 12(2). cited by applicant B. R. F. Kendall, Ionization Gauge Errors at Low Pressures, J. Vac. Sci. Technol. A, Jul.-Aug. 1999, 2041-49, 17(4). cited by applicant |
| Primary Examiner: | Berman, Jack |
| Attorney, Agent or Firm: | Dupuis, Ryan W. Satlerthwa, Kyle R. Ade & Company Inc. |
| رقم الانضمام: | edspgr.08803072 |
| قاعدة البيانات: | USPTO Patent Grants |
| الوصف غير متاح. |