SESAME stands for Synchrotron-light for Experimental Science and Applications in the Middle East. This unique facility is an international center of excellence in the truest sense of the word: developed in a multi-national collaboration under the auspices of UNESCO, modelled after CERN, and supported by various governments worldwide. The active members of SESAME are currently Cyprus, Egypt, Iran, Israel, Jordan, Pakistan, Palestine, and Turkey – a wonderful example for how countries can, despite severe political and cultural discrepancies, cooperate peacefully to bring science ahead!

A synchrotron radiation (SR) source produces intense X-ray pulses, with wavelengths and intensities that allow extremely precise studies of, e.g., material surfaces, human cells, or even atoms. In recent decades, the extraordinary power of synchrotron light has had an immense impact in almost all fields of science, including archaeology, biology, chemistry, environmental science, geology, medicine, and physics.

SESAME machine used BESSY I injector

The SESAME design is based on a 2.5 GeV hard X-ray storage ring as requested by the research community in the Middle East region. The SESAME machine is an energy ramping machine using the 800 MeV injector of the old German BESSY I facility (donated by the German government), which went through a comprehensive upgrade that increased its reliability and improved its performance. SESAME has another unique feature: It is the first SR source in the world that is powered solely by renewable energy!

Today, five beamlines are in operation at SESAME, and more are being planned. All of SESAME’s vacuum systems are based on VAT valve technology. Here, the VAT products can prove their durability and reliability once again. The long-term cooperation between VAT and SESAME has been very productive, and VAT is looking forward to bringing in more of their vacuum skills into this exciting science project!

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The rich cultural heritage of the Middle East, so often the cause for wars and conflicts, turned out to be the glue to bond the SESAME members together. As Mohammad Al-Najdawi, head of the vacuum group at SESAME, puts it: "Since synchrotron radiation plays a fundamental role in material, archaeological and cultural heritage studies, all countries in the region were eager to have their own SR-light source." Today, SESAME serves as a hub for experts from several countries, who can share their knowledge on similar research problems. Mohammad Al-Najdawi proudly adds: "Our institution is a brilliant example for how countries with more funding opportunities help cover the costs for research in areas that are not so wealthy, but have a rich cultural heritage."

BESSY I partly reborn in Jordan

The need for an international synchrotron light source in the Middle East had long been recognized in the science community. In 1997, a great opportunity finally came up: the BESSY I facility in Berlin was to be decommissioned, and Gustav-Adolf Voss, the head of DESY back then, had the idea that the components could be re-used for a SR-light source in the Middle East. The proposal fell on fertile ground, and the German government agreed to donate the components to the to-be-founded SESAME project. Jordan was selected to host SESAME, and the government of Jordan provided the land and funds for the construction of the buildings.

Like most other SR-light sources, the SESAME design was divided several parts. As a pre-injector, a classical 22-MeV microtron that emits and accelerates the electrons up to 20 MeV. After approximately 40 turns in the microtron, the electrons are transferred to the 800-MeV booster and then to the storage ring for further acceleration, until they have reached an energy of 2.5 GeV. SESAME's 2.5-GeV storage ring with a design current value of 400 mA is a 133.2 m wide ring of normal conducting magnets that keep the high-energy electrons on a circular orbit, thus emitting the synchrotron light needed for the experiments. To this end, constantly constant UHV-vacuum conditions must prevail inside the ring tunnel (approx. 10-9 mbar). The synchrotron light emitted by the electrons is then directed towards the beamlines which surround the storage ring.

Five beamlines in action

When the center was formally opened in May 2017, only the microtron and the booster contained old BESSY parts (which have been highly refurbished later on), while the storage ring was a completely new construction, with straight sections that can accommodate insertion devices to make SESAME a 3rd generation SR-light source. In April 2017, the beam circulating in the storage ring had been ramped up to its design energy of 2.5 GeV – and the experimental work could truly begin in July 2018.

These days, the SESAME researchers can dispose of five beamlines. Mohammad Al-Najdawi was involved in setting up all of them: "In 2018, we started with an IR beamline, which had been designed in collaboration with SOLIEL in France, and an XAFS/XRF beamline, which is based on a beamline donated by the Helmholtz Zentrum Dresden-Rossendorf. In 2020, we added a material science beamline that had been donated by the Swiss Paul Scherrer Institute. Since then, another two new beamlines have been built."

New soft X-ray beamline

One of the most recent beamlines that the SESAME developers installed is called HESEB, short for HElmholtz-SEsame Beamline, , the first soft X-ray beamline at SESAME. Mohammad Al-Najdawi explains: "With these soft X-rays, we can investigate a great variety of scientific questions, e.g., in solid state physics, biology, or environmental sciences. Typical applications are the development of new semiconductor materials, magnetic films, or in-situ investigations in homogeneous catalytic systems."

Once again, HESEB turned out to be a great example for how various SR-facilities bundled up their skills in order to get the best results for the science community: from 2019 on, a consortium of five German research centers (DESY, FZJ, HZB, HZDR and KIT) funded and took care of the design and construction of the beamline. As if the amount of players was not enough, Mohammad Al-Najdawi smilingly adds another one: "The HESEB layout allows for the operation of two separate experimental end stations, and the second one, with a strong focus on photoemission spectroscopy, is funded by Turkey. So it will be the first beamline branch funded and built by a SESAME member!"

BEATS beats them all!

The other new beamline is called BEATS, short for BEAmline for Tomography at SESAME. The cost of 6 million euros for this hard X-ray full-field tomography beamline comes from the European Union. Not surprisingly, BEATS is also the result of a successful international collaboration: besides SESAME and the Cyprus Institute from the Middle East, the renowned European SR-light facilities ALBA-CELLS (Spain), DESY (Germany), ESRF (France), Elettra (Italy), INFN (Italy), PSI (Switzerland), and SOLARIS (Poland) bundled their skills to create the optimal version of a tomography beamline. "It was so exciting to see how all these scientist's experiences were multiplied in this international team!", Mohammad Al-Najdawi vividly remembers.

A typical application of the BEATS beamline is the 3D reconstruction of sensible cultural heritage or regional archaeological findings that cannot just be dismantled to see what's going on inside – the perfect representation for SESAME's own heritage, so to say. But not only that: BEATS also provides great new opportunities regarding the characterization of geological samples. As Mohammad Al-Najdawi says: "Groundwater management in the Middle East is a critical issue due to the region's arid climate, increasing water demand, and the potential for over-extraction. The study of the subsurface water distribution and dynamics is thus crucial in this geographical area. Visualizing and modeling multiphase flow in water reservoirs thanks to computed tomography is a key step for planning aquifer preservation."

Reliable vacuum systems

All the vacuum systems at SESAME – be it in the machine, in the beamlines, or on the test benches – have been based on VAT valve technology from the early beginning. "Our facility comprises many UHV and all-metal gate valves of the VAT series 01.0, 10.8 and 48.1/48.2, and we use VAT valves of the series 54.1 to connect mobile pumping units", Mohammad Al-Najdawi summarizes. "Inside the storage ring, we use special RF-shielded gate valves of the VAT series 47.1/47.2, which had to be customized in order to match the tunnel's key shape. Also, we use fast shutters of the VAT series 77.1/77.3 in the front-ends of all the beamlines, in order to get the best possible protection for the ring itself and the other beamlines."

At SESAME, the durability and reliability of VAT products is beautifully demonstrated, as Mohammad Al-Najdawi explains: "Remember that the microtron and the booster were dismantled from BESSY I? In some places, we are thus using VAT valves that have been built in the 1980s. And guess what: they are still running perfectly fine!"

Trusting long-term cooperation

Mohammad Al-Najdawi is very happy about the productive, long-term cooperation between VAT and SESAME: "In my position, I have to deal with many vacuum suppliers. But dealing with VAT has been one of the smoothest and most effective cooperations, both in terms of ordering and after-sale services."

Mohammad's good impression was further improved when he visited the VAT headquarters in Switzerland in 2016. "When we had asked VAT to refurbish some of our gate valves, they told us to ship the gates over and then come ourselves to see how the refurbishing is done. It was so interesting to learn how such gate valves are produced! And we even refurbished one of our gate valves together!"

Energy from the sun

The most beautiful thing about SESAME is that, after having benefitted so much from the international funds and knowledge of other SR-light facilities, they have managed to acquire a special skill that all other facilities worldwide will increasingly be fond of. Namely, SESAME is the first accelerator in the world powered solely by renewable energy! Mohammad Al-Najdawi remembers how it all started: "Accelerators are big consumers of electricity that is expensive in Jordan. For a better sustainability of the facility, it was foreseen to find an alternative source of electric power. That's why we sought funding for a solar power plant."

In 2016, the Government of Jordan generously agreed to allocate the equivalent of US$ 7.05 million from funds provided by the European Union to support SESAME's plans, and the solar power plant came into operation in February 2019."This makes SESAME both economically and environmentally sustainable – and makes us a true pioneer in science!", Mohammad Al-Najdawi happily relates.

Promising plans

The two new beamlines are commissioned and only need to be verified before they can be released for the users. With these projects completed, what are SESAME's next plans? Mohammad Al-Najdawi is optimistic: "We have already worked out the technologies for further beamlines, but at the end of the day, it all depends on the funding we can get for our ideas." Hopefully, the worldwide science community will continue to support SESAME, so that this truly inspiring project can blossom further.

Banner image by Caraban Gonzalez, Noemi photographer, CERN-PHOTO-201811-345-3 on CERN.