Vol.2 No.4 2010

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Research paper : Portable national length standards designed and constructed using commercially available parts (J. Ishikawa)−247−Synthesiology - English edition Vol.2 No.4 (2010) situation when I started the research, the policy for elemental technology development taken under that condition, what kind of elemental technologies were developed, and what national standard was achieved by combining the elemental technologies.2 Objective of research2.1 Universalized national standardThe specifications and performances required for any standard, including the iodine stabilized He-Ne laser, and its member parts may be special compared to general products. In the basic development phase, because the priority is to realize the required performance, special and expensive materials, parts, and processing methods are used generously.In the beginning, the author was not in the position to develop the standard, but was involved in the iodine stabilized He-Ne laser as a user, and came across the opportunity of seeing the New Zealand laser. From that experience, I was convinced that the basic development phase was only half of the entire course of development of the standard, and universalization was essential to accomplish the development completely. As mentioned earlier, universalization is to carefully study and to clarify the performances and properties required and to establish the design and technology that achieve those performances and properties using universally available parts. I consider universalization as an attempt at conversion from special parts (hardware) to design and technology (software).The operating principle of the iodine stabilized He-Ne laser is based on the quantum mechanical property of the iodine molecule. Since the quantum mechanical property of the iodine molecule is consistent, there is no difference in principle among the iodines used, unlike the International Prototype of metre that uses artifacts. However, flaws arise in the mechanism, which are artificial, for extracting the stable laser wavelength based on the quantum mechanical property of the iodine molecule, and this manifests as differences and uncertainties in laser wavelengths by different devices. The author thinks that possession and maintenance of the standard is not merely possessing the iodine stabilized He-Ne laser (hardware), but is the possession of the technology to extract the laser wavelength from the iodine molecule. For universalization, careful investigation and deep understanding of the laser wavelength extraction are necessary. The possession of technology gained through universalization is none other than the possession and maintenance of the standard.It is expected that there will be many advantages in universalizing the national standard. The main advantages are the increased mutual reliability of the length standard among countries, and dramatic improvement of the precision of fine measurement of length in Japan.2.2 Increased international mutual reliabilityExcept for some of the advanced nations, most national standard labs purchase commercially available iodine stabilized He-Ne laser as their national standard. In such cases, they must depend on the laser manufacturer for repairs other than simple adjustments. In other words, the national standard labs simply possess the hardware, and the maintenance of the standard is entirely dependent on the manufacturer. There will be no major problem as long as the product has a high degree of perfection and there are no delays in supply and maintenance services. However, because a national standard device like the iodine stabilized He-Ne laser requires high technology and its demand is extremely limited, it is not easy to develop, manufacture, and maintain it as profitable business. In fact, the business is fraught with difficulties.The author considers the universalization of iodine stabilized He-Ne laser to be the realization of a laser with excellent performance, operability, economy, and ease of maintenance as a standard, and at the same time to disclose the detailed technological information to the laser users. The essence of wavelength standard is the technology to obtain stable laser wavelength from the unchanging quantum mechanical property of the iodine molecule. If the technology can be shared among the countries through universalization, it can become the foundation for establishing the mutual reliability to confirm the equivalencies of the national standards among the nations.2.3 Advancement of mid-tier traceability in JapanThere are several companies that provide calibration service for wavelength standard as business in the middle tier of traceability in Japan, and their technological level is almost par to the national standard labs except for some advanced nations. The employment of the universalized iodine Fig. 1 Traceability system of the length measurement using the iodine stabilized He-Ne laser as the national standard.SI base unit of length: meterSpeed of light in vacuum: cSI base unit of time: secondNational standard of length in Japan: iodine stabilized He-Ne laserLength standard in industry : gauge block, step gaugeMeasurement devices in industry: micrometer, caliperLength standard in calibration laboratories: wavelength stabilized laser, interferometer

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