Quantitative detection of low energy positive and negative ions with a channel electron multiplier

Review of Scientific Instruments

Volumn 67, Issue 8, 1996, Pages 2760-2764

  Keller, C A ^a   Cooper, B H ^a  

^a Laboratory of Atomic and Solid State Physics and Cornell Center for Materials Research   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0042327529     PISSN: 00346748     EISSN: None     Source Type: Journal    
DOI: 10.1063/1.1147104     Document Type: Article

References (25)

1. For other references see P. Henkel and E. Kurtz, Bibliography of Detection Efficiency of CEMs, CEMAs, MEMs, and Other Electron Multipliers (Galileo Electro-Optics Corp., Sturbridge, MA).
2. E. A. Kurz, Amer. Lab (March 1979), Galileo Electro-Optics Corp., Sturbridge, MA.
3. J. A. Sawicki, B. D. Sawicka, and F. E. Wagner, Nucl. Instrum. Methods B 62, 253 (1991).
4. M. P. Seah, J. Electron. Spectrosc. Relat. Phenom. 50, 137 (1990), see references for more electron detection efficiencies.
5. M. P. Seah, J. Electron. Spectrosc. Relat. Phenom. 58, 345 (1992).
6. J. G. Timothy and R. L. Bybee, Rev. Sci. Instrum. 49, 1192 (1978).
7. Raimund Hibst and H. H. Bukow, Appl. Opt. 28, 1806 (1989).
8. C. N. Burrous, A. J. Lieber, and V. T. Zaviantseff, Rev. Sci. Instrum. 38, 1477 (1967).
9. S. A. Fields, J. L. Burch, and W. A. Oran, Rev. Sci. Instrum. 48, 1076 (1977).
10. J. N. Chen, M. Shi, S. Tachi, and J. W. Rabalais, Nucl. Instrum. Methods B 16, 91 (1986).
11. J. M. Goodings, J. M. Jones, and D. A. Parkes, Int. J. Mass Spectrom. Ion Phys. 9, 417 (1972).
12. M. P. Seah and M. W. Holbourn, J. Electron. Spectrosc. Relat. Phenom. 42, 255 (1987).
13. P. Henkel and J. Gray, Design Principles of Channeltrons: Response Uniformity (Galileo Electro-Optics Corp., Sturbridge, MA).
14. M. P. Seah and G. C. Smith, Rev. Sci. Instrum. 62, 62 (1991).
15. Instead of the much coarser screen supplied by Galileo, we spotwelded a very fine 90% transmission screen produced by Unique Wire Weaving Co. across the CEM entrance.
16. M. Menzinger and L. Wåhlin, Rev. Sci. Instrum. 40, 102 (1969).
17. Galileo Electro-Optics Corp. Channeltron model 4830.
18. D. L. Adler and B. H. Cooper, Rev. Sci. Instrum. 59, 137 (1988).
19. R. L. McEachern, D. L. Adler, D. M. Goodstein, G. A. Kimmel, B. R. Litt, D. R. Peale, and B. H. Cooper, Rev. Sci. Instrum. 59, 2560 (1988).
20. Here we neglect the variation in efficiency across the CEM entrance. The angular distribution of ions leaving the exit of the electrostatic analyzer is independent of the pass energy. The acceleration field in front of the CEM changes this angular distribution in an energy dependent fashion. For example, 100 eV ions leaving the analyzer and then accelerated to 1 keV will have a narrower angular distribution than 2 keV ions decelerated to 1 keV. The variation in efficiency across the CEM entrance will cause the detection efficiency to vary with the angular distribution. The efficiency variation across the entrance is minimized by both shielding the CEM entrance from external fields and terminating its internal fields with a grid across the entrance (Refs. 13 and 14). The matching of overlapping sections of the relative efficiency measurements made with different preacceleration ion energies indicates that any remaining variation is insignificant.
21. Electrometer operated at 3 Hz (the maximum) sample rate. Noise amplitude before further averaging: 5 fA p-p. To further reduce the noise, 100 consecutive samples were averaged together for each data point.
22. The measured count rates have been corrected for the detector dead time (30 ns), before being used in the efficiency calculation. This gives a 3.1% correction at 1 MHz.
23. Low Level Measurements (Keithley Instruments, Inc., Cleveland, OH, 1984).
24. B. Hird, P. Gauthier, J. Bulicz, and R. A. Armstrong, Phys. Rev. Lett. 67, 3575 (1991).
25. This does not rigorously hold at lower energies since the fixed biases on the electron rejection element and the shielding cone cause an asymmetry in the angular distributions of the positive and negative ions. See Ref. 20.