Manufacturing Bits: July 11

China’s storage ring for EUV; world’s largest X-ray laser.


China’s storage ring for EUV
A group of researchers are banding together to propel the development of a storage ring technology that may one day be used as a power source for extreme ultraviolet (EUV) lithography.

The collaboration includes five institutions. Researchers have organized an informal collaboration or study group with plans to develop a storage ring for EUV based on a technology called steady-state microbunching (SSMB). The informal organization, called the SSMB Study Group, is currently based in the Department of Engineering Physics at Tsinghua University in Beijing.

The ultimate goal is to develop an EUV source using an SSMB-based storage ring. “We are making progress, aiming for a design in a year or so,” said Alex Chao, a professor of physics at SLAC at Stanford University, who is a member of the SSMB Study group.

As before, the big issue with EUV is the standalone power source. The industry is making progress with the EUV source. But so far, the source can’t generate enough power to enable the required throughput for EUV lithography in mass production.

To solve the problem, ASML continues to boost the power with its current EUV power source. Others have proposed the idea to develop next-generation EUV power sources using giant storage rings within a linear accelerator.

For some time, researchers at the SLAC National Accelerator Laboratory and others have proposed SSMB technology. Others have proposed a similar idea based on free electron lasers (FEL). “The basic idea (of SSMB) is to manipulate the beam’s dynamics in a storage ring so that its distribution is not the conventional Gaussian, but microbunched,” Chao said in an interview in 2014. “The whole concept of SSMB lies in the invention of a way to make the beam microbunched and stay microbunched in the turn-by-turn environment of a storage ring.”

In theory, an SSMB storage ring for EUV would be 50 meters in circumference and operate at 400-MeV. A ring could consist of two to six EUV scanners as needed. Each EUV tool could produce 1-kW of power.

The problem? Lack of funding. It would cost the industry millions or more dollars to develop an SSMB facility. The same is true for an FEL.

It appears SSMB is making progress, however. The SSMB Study Group has been hatched with plans to hold their first meeting at Tsinghua University in Beijing on July 21. “The group is informal,” Chao said in an e-mail. “Its core members are a few university professors.”

The first goal is to establish a conceptual design, including a proof-of-principle test at an existing storage ring in about one year. A facility site has been located in the outskirts of Beijing, according to Chao, who said a building already under construction that will house the storage ring. “When the conceptual design is ready, the University promises to provide or seek additional funds as needed for the actual construction of the first SSMB storage ring,” he said.

The SSMB group, in collaboration with the Metrology Light Source (MLS) in Berlin, is jointly studying the possibility of using the MLS to carry out a first proof-of-principle experiment. The MLS is located near the BESSY II storage ring facility in Berlin-Adlershof, Germany. It is run by the Physikalisch-Technische Bundesanstalt (PTB), Germany’s national metrology institute.

The SSMB group involves other institutions. All participants of the informal collaboration are on a voluntary, part-time basis. They have a strong interest in the technology, but do not have contractual agreements. The members are part of the following institutions–Department of Physics at Tsinghua University; SLAC; Shanghai Synchrotron Radiation Facility; Taiwan Photon Source; Tsinghua University, Taiwan; Metrology Light Source; and Pohang Light Source, Korea.

For more information, contact Alex Chao, a professor of physics at SLAC at Stanford University, at this e-mail:
[email protected]

World’s largest laser
The European XFEL, the world’s largest X-ray laser, is entering into the operation phase.

When the system is completed, the European XFEL will generate ultrashort X-ray flashes at 27,000 times per second, a billion times higher than that of conventional X-ray radiation sources. In the facility, researchers can use various instruments and equipment to map out the atomic details of viruses, cells, materials and chemical reactions. It can also be used to study the processes in the interior of planets.

The German-based system is located in underground tunnels, which can be accessed from three different sites. The 3.4-kilometer-long facility will run from German R&D organization DESY in Hamburg to the town of Schenefeld.

The completed accelerator tunnel (Source: European XFEL)

The first part of the facility is a 1.7-kilometer-long particle accelerator. In operation, the unit brings electrons to high energies at nearly the speed of light. Then, the electrons are accelerated in cavities or resonators.

In the resonators, an oscillating microwave transfers energy to the electrons. The resonators are made of the metal niobium and are superconducting.

Before moving into the operational phase, the facility had to meet a number of requirements. The pulses of the X-ray laser had to reach a wavelength of maximally two Ångströms (0.2nm) and remain stable.

The official opening of the international facility will take place on Sept. 1. The first scientific users are expected to use the facility shortly after the grand opening.