Berkeley Lab

ATAP Newsletter, Special Issue, June 2015

Back issues of the ATAP Newsletter and its AFRD (Accelerator & Fusion Research Division) predecessor are available.


BCMT Bringing Capabilities
in Magnets Together

High-performance magnets have been vital to so many DOE-supported science priorities for so long, it makes sense that Lawrence Berkeley National Lab has developed multiple areas of magnetics expertise. Now they are being brought together under the aegis of the Berkeley Center for Magnet Technology (BCMT), a joint venture of ATAP and the Engineering Division.

“Advances in magnetics can come from a variety of disciplines,” says ATAP Director Wim Leemans. He and Kem Robinson, Engineering Division Director, saw the opportunity and worked to develop the Center. “By bringing various skills and approaches to magnetic technologies together under the BCMT, we’re accelerating innovation that will ripple out to a variety of applications in research and industry.”

Led by Stephen Gourlay, who heads ATAP’s Superconducting Magnet Program, BCMT will unite that program with others, notably in the Engineering Division, that are focused on the needs of specific customers such as Berkeley Lab’s Advanced Light Source and SLAC’s Linac Coherent Light Source. The result will be integration of expertise in all kinds of magnets — permanent magnet arrays, normal- and superconducting electromagnets, pulsed specialty magnets, and hybrid designs. The Center will offer “mesoscale to magnet” capabilities that are vertically integrated from the underlying materials science up through magnet design, fabrication, and testing.

“We want to be recognized as a go-to laboratory for state-of-the-art magnetic systems throughout the DOE Office of Science,” says Gourlay. That means meeting the needs of accelerator-based high-energy physics, nuclear science, and synchrotron-light sources, as well as new customers.

Advanced magnets: essential parts of the infrastructure of discovery

One of the most obviously magnet-dependent fields is collider-based high-energy physics, which probes the fundamental nature of matter and energy with machines like CERN’s Large Hadron Collider. Nature does not give up such deep secrets cheaply, and magnets play a key role in the price as well as the physics of colliders. Magnet R&D will help lay the foundations for the future of this field.

A recently released Particle Physics Project Prioritization Panel (P5) report recommends a very-high-energy proton-proton collider as “the most powerful future tool for direct discovery of new particles and interactions under any scenario of physics results that can be acquired in the P5 time window.” It goes on to state, “The U.S. is the world leader in R&D on high-field superconducting magnet technology, which will be a critical enabling technology for such a collider.”

“We’re accelerating innovation that will ripple out to a variety of applications in research and industry.”

— ATAP Director Wim Leemans

The exact nature of this next hadron collider is still the subject of investigation and lively debate worldwide. Regardless of details, however, the design will almost certainly require extraordinarily strong dipole magnets to bend an extremely “rigid” beam into a circular course within an underground tunnel of cost-effective length. These magnets must combine unprecedented field strength, operational dependability, and low cost.

This is where ATAP’s Superconducting Magnet Program (SMP) comes in. “For years, the SMP has excelled at developing magnet technologies,” says James Symons, Associate Laboratory Director for Physical Sciences at Berkeley Lab. “This is an area where traditionally we have been very strong.”

SMP holds a series of records for the field strength of accelerator-style dipoles, and is home to what Gourlay, who has twice headed the program, describes as “an unrivaled level of integration of design and analysis tools.” The program is now turning its attention to new ways of building these magnets. The ultimate goal is an easier-to-manufacture dipole that routinely achieves, in service, what is now the experimental record for field strength. (See Can Do on Canted Cosine-Theta” in the April 2015 issue of the ATAP Newsletter.) It is an ambitious target, but as Gourlay puts it, “Taking on the toughest problems is how we learn the most.”

“The BCMT will help foster communication channels and coordination that are key to collaboration,” adds Soren Prestemon, a superconducting-magnet engineer who also serves as ATAP’s Division Deputy for Technology. “This approach is truly the best way to integrate design and construction into applications with our partners.”

Precision magnets for exquisite light

Synchrotron light has come to be vital throughout the physical and life sciences. In the facilities that provide it, magnets are doubly important: not only do they guide the electron beam, but magnetic arrays called “insertion devices” (because they are inserted into the accelerator’s magnetic lattice) extract photon beams that have the coherence, brightness and spectral qualities needed by the users. Insertion devices are often known as “undulators” or “wigglers,” depending on their characteristics.

Designing and building insertion devices is a longtime strength of Berkeley Lab. In the 1980s, under the pioneering leadership of the late Klaus Halbach, fundamental progress was made in understanding the physics and engineering of permanent-magnet insertion devices. The results helped make possible the Advanced Light Source (ALS) — a major user facility at Berkeley Lab, and among the first of a generation of light sources designed to exploit the scientific advantages of numerous insertion devices.

As synchrotron radiation sources progress, the need for insertion devices using a wide range of technologies has been dramatically increasing. “Superconducting, electromagnet, permanent magnet and hybrid structures all have important roles to play,” says Ross Schlueter, head of the Magnetics Department in the Engineering Division.

A generation after the commissioning of the ALS, storage-ring-based light sources have been joined by free-electron lasers, which have insertion devices at their heart, in the quest for photon beams with ever-more-exquisite characteristics. BCMT physicists and engineers are designing the insertion devices that will be needed by future light sources of both these kinds. Examples include the recently proposed ALS Upgrade and the FEL-based Linac Coherent Light Source II, which is being built at SLAC National Accelerator Laboratory and for which LBNL is designing and building the insertion devices.

LCLS-II_undulator_prototype A prototype LCLS-II undulator is shown here in the magnetic measurement facility at Berkeley Lab. The challenges of building such a device are not limited to magnetic design and characterization. Another prominent feature is a strongback structure to keep the magnet arrays in the desired position — opening or closing the gap on command — with micron accuracy in the face of tens of thousands of kg of magnetic repulsion. Each LCLS-II undulator array will consist of several individual sections like this.

The insertion-device efforts have also resulted in novel measurement and engineering diagnostic techniques, complementing those that originated in magnet development for high-energy physics. “The Center will foster and cultivate synergies in magnetic measurement and testing as well as innovation in the magnets themselves,” says Robinson.

SCU_combo_image Left: Conceptual layout of an FEL line based on superconducting undulators (SCUs).
Below left: the machined 1.5 m core that will be used for half of the LBNL Nb3Sn SCU prototype.

SCUs could combine significantly lower overall-system cost and better performance in FELs as well as storage rings, compared to traditional permanent-magnet undulators. Described by Symons as “the next generation of insertion devices,” SCUs offer tantalizing advantages, but are challenging to implement with the exacting standards required by FELs.

In an R&D project that hopes to benefit current and future FELs, we are working with Argonne National Laboratory and SLAC National Accelerator Laboratory on prototype SCUs. The Berkeley Lab unit takes advantage of our deep expertise in undulator technology, as well as leadership in the design and fabrication of superconducting magnets and in working with high-field Nb3Sn superconductor. Fabrication is underway and testing is expected this summer.

Magnets: seemingly everywhere in the sciences

The BCMT’s integration of expertise should prove useful in spinoff applications as well. An example is a longstanding LBNL interest: particle accelerators for cancer treatment. Recently DOE and the National Cancer Institute announced several research grants, one of which aims to reduce the size and weight of particle-beam delivery systems by an order of magnitude. Supported by a DOE Accelerator Stewardship grant, an international team, led by Berkeley Lab, will develop improved treatment delivery systems with magnet technologies that originated in high-energy physics.

Another example is an innovative superconducting magnet for an advanced electron cyclotron resonance ion source at the Facility for Rare Isotope Beams (see “Rare Isotopes Start with a Remarkable Magnet” in the February 2015 issue of the ATAP Newsletter).

FRIB_fields At one of the flagship facilities of the DOE Office of Nuclear Physics — the Facility for Rare Isotope Beams (FRIB) that is being built at Michigan State University — everything begins with a high-performance source of heavy ions. Leveraging experience with Berkeley Lab’s VENUS ion source, the FRIB team is developing a 28-GHz electron cyclotron resonance (ECR) source.
ATAP’s Superconducting Magnet Program designed and is building a key component: an advanced magnet with a sextupole field within three solenoids. Above, left: Profile of solenoidal field needed to operate at 28 GHz. Above, right: Iso-B surface at 1.85 T inside the magnet aperture that provides plasma confinement. Source fabrication is underway, and SMP staff led by Helene Felice and Soren Prestemon are working to ensure successful integration of the ECR magnet in this application.

“Having an integrated center like this,” says Robinson, “anybody coming in to the magnet center will be plugged into all available technologies.”

Non-DOE agencies and industrial partners who approach Berkeley Lab for advice and R&D on magnets will have one-stop shopping for all the likely solutions, including advanced permanent-magnet arrays as well as superconducting magnets and hybrids of superconducting and normal-conducting technologies. Biomedical and energy applications are among the possibilities. As Leemans and Robinson point out, there is a convergence of long-term requirements and needs for light sources and high-field applications of magnets; meanwhile, the prospects for addressing these needs include a number of technology crossovers like superferric magnets. The Center has a timely ability to combine existing strengths for new applications.

The new Center will coordinate the efforts of Berkeley Lab scientists and engineers who will remain in their current organizations and continue serving their present customers, and will combine intellectual and infrastructure resources to a degree not previously seen. Having all our magnetics capabilities and projects on the same page, Symons points out, is expected to lead to synergy and new ideas as well as efficiency. Systems engineering, quality assurance, and formal project management commensurate with the needs of the particular project are other strengths that the BCMT can bring to bear.

From a foundation of strong collaboration between ATAP and Engineering, the goal of BCMT is close coordination and leveraging for all parts of magnet science at Berkeley Lab. The planned result: magnet innovation combined with better service to both traditional and new customers in the DOE Office of Science and beyond.