Newsletter - September 2008
Projects With Sun
NMISA is responsible for the maintenance and dissemination of the National Standards. Part of this is the research and development of not only the National standards but also the secondary standards and measuring systems which is required for industry measurements. Universities were contacted in order to assist in these and build capacity not only at NMISA but also tertiary institutes.
Stellenbosch University (SUN) was contacted as they have extensive research experience in vision measuring and also coordinate metrology. Three projects were proposed and are currently in collaboration between NMISA and the university. These are: 1) laser tracker, 2) absolute gravity measuring system, 3) sieve calibration system. Between these projects there are a good split between development of a National Standard, industrial measuring system and high level research.
1) The CMM (coordinate measuring machine) market is the single largest dimensional metrology market in South Africa with more than 350 machines (not including articulated arms, laser scanners and photogrammetry systems which are also CMMs) in operation. These machines have a capital investment of each machine between R500k for a small unit to R10mil for the large CMMs use in automotive manufacturing process of the measuring of the body in white. The total calibration cost of these machines is more than R3,5mil a year and more than R50mil worth of measurements performed every year using CMMs . Bridge type CMMs, which are mostly used in industry, have 21 error parameters which must be calibrated. These errors are because a bridge type CMM does not measure according to Abbe principles. (This results in error results from the offset between the measurement beam and the axis of motion of the part under test). To reduce this, a CMM with none of the traditional errors must be design. A laser tracker does not have any of these errors as the measure axis and part under test axis are in line and are therefore chosen to replace bridge type CMM in the future. A project together with the university was embarked to design and develop such a laser tracker. The project started in the beginning of 2008 and will optimistically be completed in only 3-5 years.
2) Gravity is one of the fundamental units required for mass, pressure, force, torque, flow and volume measurements. A new system is under design which works by a free falling optical corner cube down a vacuum tube and by using a laser interferometer measures the acceleration(g) of this cube. The complete system consists of an optical laser system to perform the measurements and a mechanical system to navigate the laser optics. The mechanical design for the system has been completed, sees drawing 1, and was manufactured. The mechanical system will be tested during September when the student is at NMISA during vacation work.
Drawing 1: 3D drawing of mechanical layout for system.
3) The calibrations of sieves are becoming more important in South Africa. Sieves are used to separate beads which are critical in the glass, polymer, and pharmaceutical industries. There is a requirement for the calibration of sieves but there are no accredited facilities in South Africa. The university with it’s experience in vision measuring was approached to develop such a system. Some sieves under test have apertures of only 63µm and to be able to comply with ISO specification must be accurate to within only a few µm. The software been written and the first picture, figure 1, of the 63µm sieve was taken. An algorithm must be developed to best measure the openings as the form of all are not a perfect square, as can be seen in the picture.
Figure 1: Picture of 63µm sieve taken with software written by student.
Optical Frequency Standard Research Project: A New Start In 2008
Status of the long term project: The optical frequency standard research project at NMISA has restarted this year, and we are currently in a process of capital purchases to enable the experimental work. Before this a new driving philosophy had to be found. The end result on the new philosophy resolves around compact, portable optical frequency standards (let us call it clocks, although strictly speaking we are not necessarily interested in measuring time) utilizing fibre technology in some parts, augmented by cell-based atomic and molecular references.
Innovation of the NMISA design: This fills an important niche in worldwide clock research, and requires more realistic resources than cold atom and ion clocks (which will require decades more of research to be implemented as reliable workhorse clocks, mostly because of mature but mechanically unstable laser technology that is utilized). Therefore newer mode-hop free lasers (essentially frequency stable lasers, more or less unaffected by the environment) are increasingly been adopted to replace the older technology, and yield much better operational characteristics. These compact optical clocks should in the end well exceed the performance of caesium clocks on short time scales especially, and augment the measurement capabilities at NMISA in a few years either running as short term stabilizers for a caesium ensemble or as a separate system.
optical system designed with the unique requirements of Africa in mind: The interesting aspect of this architecture is that it can possibly be duplicated for use elsewhere in Africa, because of the potential low cost and robustness. The latter attributes comes from either making the system compact, and using as little bulk optics as possible; two approaches are silicon based mini-clocks (like at National Institute for Standards and Technology (NIST)) or the utilization of fibre elements like in our case (NIST and others are also starting to experiments with selected elements of this). The approach is therefore literally built around the needs and capabilities typically encountered in the developing world – as opposed to “super” experiments that can be pulled off by the large nations (even if it considered as “minor” work there). At the same time though we will be leading in certain niche areas, that are overlooked in the race to produce new science, while at the same time utilizing some concepts that has already been proven elsewhere.
Adding to our motivation for taking our local approach is that even large standards research institutes like the USA’s NIST and France’s LNE-SYRTE has appreciable activity in simplified optical clocks for real world application. This activity should be somewhat contrasted against proof-of-principle experiments that have been done in the USA, Germany, France and Japan to illustrate the potential of very narrow optical transitions (<1Hz) of atoms for the realization of frequency standards of the most exquisite accuracy, and which has pushed the forefront of physics. The accuracy of the best clocks is such is that they have the ability to loose less than one second of time in the whole age of universe since the Big Bang), and are sensitive to gravity to a degree that means even a < 10cm up/down shift of the apparatus with respect to centre of earth is detectable. These complex clocks, which typically need quite a few specialized lasers for operation are however still laboratory experiments, and will remain so for many years. The large infrastructure and apparatus costs (up to R30 million), makes these very monstrous projects in a South African context, and also needs a few highly trained experts to operate. The application of ultrahigh accuracy clocks approaching 10-17 fractional frequency stability) is also still unknown at this time, and the reasoning is that something like 10-13 to 10-15 in the optical domain will meet local metrology requirements for many decades to come. In fact the operability and transportability of the compact clock approach will in fact open quite a few exciting application areas.
Application across metrology areas: Even at this stage it can be said that our optical frequency standards research will enable measurements for optical communications (especially with emerging coherent communications), general optical frequency measurements, low phase noise microwave generation, timekeeping and local oscillator signals for large arrays of RF telescopes for astronomy. It can also serve as improved dimensional standards because of the low fractional uncertainty on the wavelength.
We also plan to work closely with our local chemical metrology group. The technically strong chemistry group produces world leading results in some areas, among them the realization of better gas standards, which are used extensively in the chemical industry. Our technology and expertise in optical frequency standards were pre-chosen so that with some adaptations and additions, we will be able to do precision measurements of trace amounts of gas (utilizing the so-called Cavity Ringdown Spectroscopy technique), in new wavelength bands that have not been explored before. This activity will also push us to the forefront in this area worldwide, and will also be of particular importance to the large South African chemical industry. The precision frequency measurements will also make possible other interesting applications like temperature measurement and accurate determination of Boltzmann’s constant. Finally we also plan to work on the dissemination of the standard; for example how to transport a signal to a client with high fidelity, and there are even long term opportunities of setting up a new worldwide optically linked satellite systems for linking the world’s timing and frequency nodes.
Interaction with international peers: This project has benefited greatly from the visit of the lead researcher recently to France and the USA, in order to survey some of the existing technology at the leading metrology labs. Talks about our proposed work were also given in France and were well received; there was comprehension and agreement on an approach suited to our needs and capabilities. The South African choice was more or less to participate on a new clock development at one of these larger labs (like a strontium lattice clock that are pursued in both France and the USA) versus a smaller high performance “niche” clock. In the end the latter won, because of the need of local photonics expertise and the associated infrastructure in a variety of metrology areas at NMISA and generation of standards specifically for the developing world (but that would have possible application even in developed nations). The benefit of the visits in the end was that important elements of clock construction and design could be assimilated, and now applied to our situation. In the words of the recently visiting Dr.Santoyo of the CIO in Mexico, technology implementation in countries of our scale, should be locally determined in the end, as externally driven ideas and projects sometimes have agendas that are rather built around external interests/understanding of local circumstances ( a concept very clear to any home-owner!).
Currently involved researchers are Johan Burger, Mikhail Sakharov and Chris Matthee, and we are also in the process of hiring two postdocs. There is quite an excitement as to where we are going, and acceptance that it will add value (as opposed to extravagantly spending money on research that has no clear benefit) within our local context.
Other unique aspects of the project: We will add new knowledge in form of actually also developing a new spectroscopy method, and signal processing that might for the first time in the world be able to remove light shift effect (the deviation of the standard due to the presence of light) in our measurement. Another unique element is the initial decision to integrate a system as far as possible into fibre, as opposed to using hard to align and unstable bulk elements. This will greatly facilitate our previously stated goals. Many pieces of hardware have now been ordered in order to bring our lab up to standard for this work. We are for example expecting our high power DBR fibre laser beginning October, and a fibre coupled waveguide doubler system shortly after. General diagnostics (power, pulse measurement etc) and assembly equipment (splicers etc.) are currently being ordered. A large part of the innovations will be on the electronics side, and principal decisions have been made, although calculations are ongoing. With our current line of work on the new frequency standard we also be able to finally fully utilize our large previous investment in the form of a Ti:Sapphire laser based comb spanning the visible up to 1100 nm (near infrared wavelengths). We will be using expertise gained with this system to also in-house extend our frequency measurement capability up to 2 micron and beyond.
It is great to be breaking new ground, and we hope to make South Africa proud with work with our technical accomplishments, and make contributions to capacity development and industrial applications aligned to local needs.
BIPM Metrology Summer School 2008 (29 June to 11 July 2008)
The BIPM’s Summer School is a prestigious event that brings together young metrologists from all over the world to present to them a broad review by world experts of the present state of metrology and to assist them to build their own networks with peers for future interactions and collaboration.
It was an honour for the NMISA that James Tshilongo and Mariesa Nel were selected to attend the second BIPM Metrology summer school 2008, at the BIPM (Bureau International des Poids et Mesures) in France. The school covered all fields of metrology over the 2 weeks, with focus on emerging metrology areas. James and Mariesa were exposed to new developments and thinking in nanotechnology and metrology in the medical fields, time and frequency, electricity, photometry and radiometry, mechanical and ionizing radiometry to name but a few.
The lectures also covered the history of the SI (the international system of units), what the first definitions were, how the SI system evolved into what it is now and current developments. The plans for the new definitions for some of the units were also discussed.
Current projects in the physical metrology field at BIPM and some of the other top NMIs are:
The lecturers included some Nobel laureates : Prof. Sir Harry Kroto, Prof. William Phillips, Prof. Klaus von Klitzing and special guest : Mrs Dava Sobel, author of "Longitude" and more than forty teachers, chosen among the metrology world experts. Other activities included workshops, laboratory visits, a poster session, picnic lunches at the BIPM and the Summer School party.
Prof Andrew Wallard (outgoing director of BIPM) shared his experiences of a life in metrology with the students:
Then, at the end of the school, Dr Mike Sargent (Chemistry, LGC, UK) summarised:
Visit to BIPM Chemistry section by James Tshilongo
Climate change or global warming is one of the most important global challenges facing the international community. It is a threat to all nations, and requires a coordinated, determined and united response. As growing populations and increasing industrialisation is putting more pressure on the environment, government and conscientious industries are forced to take responsibility to preserve the environment. In order to address these new challenges good measurement is required in the gas metrology laboratory especially at NMISA in order to support local industries which are active in air pollution monitoring. Fourier Transform Infrared (FTIR) spectroscopy has been identified as a measurement technique with the potential to analyse for trace and ultra trace levels of infrared active gases, such as nitric oxide (NO), nitrogen dioxide (NO2) and sulphur dioxide (SO2). FTIR spectroscopy has matured into a routine analytical technique. The need has increased for reference data of high quality. In particular, national and international pressure for reduced anthropogenic emissions including hazardous air pollutants, greenhouse gases, and ozone-destroying chemicals has pushed quantitative infrared analysis to a new level of importance. After attending the BIPM metrology summer School, James Tshilongo spent a week at the BIPM Chemistry section for Fourier Transform Infrared training with an expert, Dr Edgar Flores Jardines. Many suggestions and recommendations were discussed on how to obtain good measurements for purity analysis of gas mixtures using different software programs such as E-Trans, MALT and IMACC.
Afrimets Holds Its 2nd General Assembly
The Intra-Africa Metrology System (AFRIMETS) held its 2nd General Assembly hosted by the Ministry of Commerce and Industry of the Government of Tunisia in Tunis from 1-4 July 2008. The General Assembly was preceded by an AFRIMETS executive committee (EXCOM) meeting and a workshop on “Metrology Development in African Countries” held on the 1st and 2nd July respectively. The General Assembly was attended by more than 50 delegates from all of the five sub-Regional Metrology Organizations in Africa including Legal metrology and observers from PTB, BIPM, OIML, EURAMET, LNE, UNIDO, ECOWAS, UEMOA, the SADC secretariat, the African committee for metrology (CAFMET) and the Arab federation of metrology.
Mr. Chokri Mamoughli, Permanent Secretary: Ministry of Commerce and Industry
The General Assembly was officially opened by the Permanent Secretary of the Ministry of Commerce and Industry Mr. Chokri Mamoughli, who welcomed all the delegates to Tunisia. In his speech the Permanent Secretary reiterated the importance of metrology to the national economy and acknowledged the role that AFRIMETS would play in ensuring that accurate measurement are harmonized in Africa, establish new measurement facilities and gain international acceptance for all measurements critical to export, environmental monitoring and sanitary and phyto-sanitary issues.
Dr Wynand Louw, Chair of AFRIMETS informed the delegates of the progress made since the establishment of AFRIMETS and presented the AFRIMETS Technical Committee and Working Group Structure. He further informed the General Assembly that after consultation with SADCMET, AFRIMETS has made a presentation to the JCRB at its meeting in Wellington, New Zealand to take over the RMO role for Africa from SADCMET. The JCRB commented that since AFRIMETS is an expansion of SADCMET and will build on the already existing RMO structure and experience of SADCMET, AFRIMETS could directly apply to the CIPM for recognition as the official RMO representing Africa. The request from AFRIMETS as endorsed by SADCMET and the JCRB will be considered at the next meeting of the CIPM scheduled for October 2008. The General Assembly also discussed the draft document for the AFRIMETS Quality System for compliance to the CIPM MRA and agreed that AFRIMETS can follow the two routes as described in the CIPM MRA for the submission of CMCs, but the preferred route will be the support of capabilities through official third party accreditation.
Dr Wynand Louw (middle): AFRIMETS Chair with Mr Chokri Mamoughli (right): Permanent Secretary and Mr. Francois Magana (left): Director of OIML
during the workshop on Metrology Development in African Countries.
A number of organizations joined AFRIMETS as associate and observer members during the General Assembly and signed the MoU at a ceremony which was presided by the AFRIMETS Chair. The following members have now joined AFRIMETS:
Prof Ali Abu Elezz signed on behalf of NIS, Egypt (as an Ordinary member)
Mr. Stefan Wallerath signed on behalf of PTB (Associate member)
Dr. Luc Erard signed on behalf of LNE (Associate Member)
Dr. Luc Erard also signed on behalf of EURAMET (Observer member)
Mr Hassine signed on behalf of CAFMET (Observer member)
Prof Mahmoud Sherbiny signed on behalf of the Arab federation of metrology (Observer member)
MoU Signing Ceremony
Delegates to the General Assembly
The next General Assembly will be held in South Africa hosted by NMISA at Mabalingwe Game Reserve in July 2009.
New Appointments For July And August 2008
| Name | Position | Start date | Area |
|---|---|---|---|
| Patricia Mogwe | Project Coordinator | 7/7/2008 | Regional and Africa |
| Monica Peart | Quality Manager | 1/8/2008 | Operations Support |
| Pamela Silwana | Metrologist | 1/8/2008 | EM1: TF and RF |