Vol.2 No.4 2010

25/68

Research paper : Portable national length standards designed and constructed using commercially available parts (J. Ishikawa)−255−Synthesiology - English edition Vol.2 No.4 (2010) 6 Performance of the developed national standard and its utilizationThe new iodine stabilized He-Ne laser is used as the national standard of Japan at AIST and as the standard of the calibration service providers that provide the wavelength standard. This laser has new, original mechanisms as explained above. Its greatest characteristic is that it is supplied as a do-it-yourself assembly kit rather than a whole product. As mentioned earlier, what is important for a standard using the quantum mechanical property of iodine molecule absorption line is the technology of extracting the standard (wavelength) from that property. To put this thinking to practice, the author published Monograph of Metrology[6] that explains the details and plans of the new iodine stabilized He-Ne laser. Based on this monograph, one can create lasers that will satisfy the recommendations of CIPM. However, although the parts are generally available, it is hard work to procure all of the necessary parts to fabricate the laser. Therefore, we gathered all the necessary parts and distributed them for a charge to companies as a do-it-yourself kit. Since it is a kit, it is guaranteed that each member satisfies the specification, but the final performance as a standard (absolute wavelength and uncertainty) depends on the owner’s technology. Technological instruction for assembly is provided by request. By distributing this kit, we realized a “bargain” price as a national standard at 2,000,000 yen a set including the laserhead and the controller (control part is provided in almost completed form). The attempt to transfer the technology of wavelength standard is also done internationally. AIST has been working on the project to assist the establishment of the National Institute of Metrology Thailand (NIMT). The first kit of the iodine stabilized He-Ne laser was delivered to NIMT through this project. Current, similar technological transfer is planned for the national standard labs in the ASEAN countries.This laser was used for international comparison, and was found to have excellent feature unseen in other lasers, as a standard that follows the recommendation of CIPM. One of the recommended parameter of CIPM states that the temperature of the wall of the tube of the iodine cell must be maintained at 25 ± 5 ºC. This temperature is almost the same as the environmental temperature, and the iodine stabilized He-Ne laser should function in the temperature range of 25 ± 5 ºC. The new laser fulfills this condition. It is capable of maintaining wavelength stability in the range of 25 ± 5 ºC, and the wavelength change showed good results where uncertainty stayed at half or less of the recommended by CIPM (5 kHz or less converted to optical frequency). On the other hand, many lasers including the conventional laser require strict stabilization of environmental temperature to fulfill the uncertainty recommended by CIPM. The change in tilt angle of the laser mirror due to the expansion and contraction of the ring-form piezo stack actuator used in many lasers may become a factor of change in laser wavelength. To prevent the change in the tilt angle, it is necessary to conduct strict environmental temperature stabilization to minimize the expansion and contraction of the actuator, in addition to the use of ultra low expansion material for the laser main body. Once, we conducted the international comparison by gathering the iodine stabilized He-Ne lasers of various nations that were used as national standards in one place. During that session, the temperature of the room where the lasers were set up changed about 2 ºC due to the malfunction of the air conditioner. Many lasers became unlocked and stopped functioning while the new laser continued to perform without unlocking, and demonstrated its high performance.7 ConclusionThe author became involved with iodine stabilized He-Ne laser as a user. In “developing the precision interferometer,” my initial topic of research, my latent desire was to improve the usability and reliability of the iodine stabilized He-Ne laser that was the standard light source for wavelength. When I saw the portable laser from New Zealand, the desire became manifest and I started the research as explained earlier. However, if I was not a user but a developer of the conventional laser, I am likely to have said, “This is the national standard and I don’t care about the usability. Rather, it is more important to develop the next-generation standard with higher precision.”I think the greatest factor that made me set the direction of the research - to achieve special function by using the universal parts in unconventional, special ways - was the fact that the improvement of the iodine stabilized He-Ne laser was not my official topic. In the early phase of the research, I had extremely low budget and I had no time schedule or obligation to come up with a result. This allowed me to try bold experiments and that set the direction of research. If a research plan was written as an official project with formal budget request, I am certain I would have made safe choices of using special parts and special materials in a conventional manner.I mentioned in the previous chapter that a “bargain” price was achieved by providing the iodine stabilized He-Ne laser as a do-it-yourself kit. However, the true significance of DIY is the increased motivation of the users. The assembly of the laser is done as a training session, where many participants work on it with enthusiasm and become totally absorbed in it. The author tells the participants who finish the session and are taking the assembled and adjusted iodine stabilized He-Ne laser home, “This laser is not a standard but just a thing. Standard is the technology you have learned and your will to maintain this standard.”

※このページを正しく表示するにはFlashPlayer9以上が必要です