Possibility and current status of absolute XHV measurement by laser ionization

Shingo Ichimura, K. Kokubun, H. Shimizu, S. Sekine

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The current status and possibility of XHV measurement by laser ionization using second harmonics of a picosecond YAG laser are discussed. Under the condition that incident laser energy was 30 mJ/pulse and the laser beam was focused with a spherical lens (focal length f= 250mm) to a power density sufficient for the saturation Of H2 ionization at the focal point, the minimum pressure in an XHV chamber was measured. From the minimum pressure estimated by extrapolation (5 × 10-11 Pa) and the ion counting rate at that pressure (one count during 500 laser shots), the volume of the ionization region was expected to be 1.7 × 10-4 mm3. The ionization region was then measured experimentally under the same laser beam conditions. It was found that the ionization region has a spindle shape with maximum diameter of 45 μm and the length of 1.2mm. The estimated volume is larger than the expected volume by a factor between 4 and 12. The ion detection efficiency of the electron multiplier is one of the major factors affecting the difference, and it can be reduced to within a factor of 3. On the basis of the results, the possibility of absolute measurement of XHV pressure by laser ionization is discussed.

Original languageEnglish
Pages (from-to)545-552
Number of pages8
JournalVacuum
Volume47
Issue number6-8
Publication statusPublished - 1996 Jun 1
Externally publishedYes

Fingerprint

Ionization
ionization
Lasers
lasers
Laser beams
laser beams
Ions
Electron multipliers
spindles
photomultiplier tubes
Extrapolation
shot
YAG lasers
radiant flux density
extrapolation
Laser pulses
Lenses
counting
ions
chambers

Keywords

  • Ionization volume
  • Laser ionization
  • Molecular density imaging
  • XHV

ASJC Scopus subject areas

  • Instrumentation
  • Condensed Matter Physics
  • Surfaces, Coatings and Films

Cite this

Ichimura, S., Kokubun, K., Shimizu, H., & Sekine, S. (1996). Possibility and current status of absolute XHV measurement by laser ionization. Vacuum, 47(6-8), 545-552.

Possibility and current status of absolute XHV measurement by laser ionization. / Ichimura, Shingo; Kokubun, K.; Shimizu, H.; Sekine, S.

In: Vacuum, Vol. 47, No. 6-8, 01.06.1996, p. 545-552.

Research output: Contribution to journalArticle

Ichimura, S, Kokubun, K, Shimizu, H & Sekine, S 1996, 'Possibility and current status of absolute XHV measurement by laser ionization', Vacuum, vol. 47, no. 6-8, pp. 545-552.
Ichimura S, Kokubun K, Shimizu H, Sekine S. Possibility and current status of absolute XHV measurement by laser ionization. Vacuum. 1996 Jun 1;47(6-8):545-552.
Ichimura, Shingo ; Kokubun, K. ; Shimizu, H. ; Sekine, S. / Possibility and current status of absolute XHV measurement by laser ionization. In: Vacuum. 1996 ; Vol. 47, No. 6-8. pp. 545-552.
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