Introduction of primary standard of length into a national metrology laboratory

Project Description

National length metrology laboratories of Croatia and Slovenia decided to upgrade the metrology infrastructures with laser frequency standards. While the Croatian laboratory has the standard and an appropriate room already available, the Slovenian laboratory is in a phase of purchasing a standard.

However, both laboratories need to get advanced technical knowledge and practical experiences in applying the standard for metrological tasks. Therefore, BEV was asked to participate in a research project in order to share its reach technical knowledge and experiences.

The basic project activities will be:

• courses on laser frequency standards and measurements
• workshops on necessary measurement conditions
• performance of measurements
• definition of technical parameters for the measurement room in Slovenian laboratory

Final Report 2011-09-25

The project was concluded in June 2010. The following activities were executed during the project:

• Exchange of experts and training
• Purchase and activation of standards at MIRS/UM-FS/LTM (SI) and HMI/FSB-LPMD (HR)
• Evaluation of standards and preparations for taking part in a CCL intercomparison

Performed actions:

1. Exchange of exprets and training

• first visit of 2 experts from MIRS/UM-FS/LTM  to BEV was performed in October 2006. Frequency standards were totally new field of research at MIRS/UM-FS/LTM at that time. A new expert was appointed by the head of the institute. The purpose of the first visit at BEV was to collect basic data, literature and information about possible suppliers of frequency stabilised lasers
• second visit of MIRS/UM-FS/LTM to BEV was performed in the first quarter of 2007. In the same period, one visit of 1 MIRS/UM-FS/LTM expert to HMI/FSB-LPMD was performed. At that time, HMI/FSB-LMPD alredy had a primary standard (from 2003) and MIRS/UM-FS/LTM was still in the phase of assuring resources and searching a supplier. Important information about the environmental conditions and necessary equipment for frequency measurement was gained by MIRS/UM-FS/LTM at these twio visits.
• two more visits of MIRS/UM-FS/LTM to BEV and 1 to HMI/FSB-LPMD was performed in the third quarter of 2007. In this period MIRS/UM-FS/LTM took a decission on the frequency standard supplier based on information gained at BEV. It was decided to buy a Polish Lasertex standard.
• in the second quarter of 2008, 2 experts of HMI/FSB-LPMD visited MIRS/UM-FS/LTM in order to share their experiences with applying their standard and about possible evironmental influences
• after puchasing their frequency standard in the third quarter of 2008, MIRS/UM-FS/LTM visited BEV again. Experts studied together the characteristics and it was proposed by a BEV expert to take part in a CCL comparison as soon as MIRS/UM-FS/LTM experts would have enough experiences in frequency calibrations and after they would be able to characterise their standard.
• one more visit of MIRS/UM-FS/LTM experts to BEV was performed in February 2009. In that time,  MIRS/UM-FS/LTM already applied for CCL-K11 comparison. Specific expert questions on evaluation of the frequency standard characterisation were answered by the BEV experts at this time.
• in the thirs quarter of 2009, MIRS/UM-FS/LTM experts visited HMI/FSB-LPMD in order to exchange their experiences in laser frequency calibration.

All visits and exchange of experiences were of a great value for both NMIs (MIRS and HMI) in the process of introducing primry frequency standards into their calibration service and research.

2. Purchase and activation of standards at MIRS/UM-FS/LTM and HMI/FSB-LPMD

HMI/FSB-LPMD purhased their standard (NPL 633nm iodine stabilized He-Ne Laser S.N. LL0601/R19) already before the start of the project (October 2003). They already had some experiences in the work with the laser. In February 2009 they changed a laser tube and made some adjustments to the laser source.

MIRS/UM-FS/LTM have got their laser in September 2010 (Lasertex LJSC-3-11). Based on the knowledge gained thorug expert visits, intensive work and characterisation of the laser was started in the same month. In siy months, MIRS/UM-FS/LTM was ready to take part in the CCL-K11 intercomparison.

3. Evaluation of the standards and preparation for taking part in a CLL intercomparison

• MIRS/UM-FS/LTM standard was evaluated on hand of the producer data and measurments in a femtosecond comb at BEV.
• HMI/FSB-LPMD laser was characterised in a co-operation with NPL.
• Measurements within CCL-K11 intercomparison were performed by MIRS/UM-FS/LTM in March 2009 at BEV
• Measurements within CCL-K11 intercomparison were performed by HMI/FSB-LPMD in December 2009 at BEV

Conclusion:

Both NMIs (MIRS/UM-FS/LTM nad HMI/FSB-LPMD) got a lot of precious new knowledge and experience in frequency calibration and laser characterisation during the project. The results are reflected in their CMCs in KCDB database (both CMCS approved in April 2010).