One of the most exciting and challenging projects in nuclear physics is the Facility for Rare Isotope Beams, a user facility being built at Michigan State University. Berkeley Lab brought one of its world-leading capabilities to FRIB: the design, construction, and (as of December 12) delivery of a superconducting magnet for the electron cyclotron resonance ion source.
Meanwhile, our contributions to Berkeley Lab’s Advanced Light Source continued; ATAP played key roles in the COSMIC beamline, which is completing the commissioning process and on the verge of user experiments, as well as providing an enabling technology for a private-sector research project.
As 2017 comes to a close, I wish everyone a happy and safe holiday season, and look forward to another year of innovation and discovery by ATAP researchers in 2018.
DELIVERY OF BERKELEY LAB ECR MAGNET TO FRIB BRINGS FUTURE OF NUCLEAR SCIENCE ONE STEP CLOSER
At one of the flagship facilities being constructed by the DOE Office of Nuclear Physics — the Facility for Rare Isotope Beams (FRIB) at Michigan State University — everything begins with a high-performance source of heavy ions, the electron cyclotron resonance (ECR) source. The Berkeley Center for Magnet Technology has designed, built, and now delivered, a key component of the ECR source: an advanced superconducting magnet configured to produce a sextupole field embedded within three solenoids.
The ECR source will provide beams of ions as heavy as uranium. It must be capable of high current and high charge states (13.5 particle microamperes (pµA) and 33+, respectively, for uranium). This difficult task was a natural for LBNL, where the ECR source VENUS (Versatile ECR Ion Source for Nuclear Science) had already been built for the LBNL Nuclear Science Division’s 88-Inch Cyclotron. The performance of VENUS in producing intense high charge state beams was crucial in demonstrating the feasibility of the FRIB design concept.
The FRIB ECR magnet provides the combination of strong magnetic fields needed for plasma confinement: a 2-tesla sextupole field in the plasma chamber with a superimposed solenoidal field profile (4 T – 0.8 T – 3 T) produced by three solenoids. The project serves as an example of advanced magnet system design and construction that the Berkeley Center for Magnet Technology (BCMT) provides for the DOE Office of Science. BCMT brings together the Accelerator Technology and Applied Physics Division (ATAP) and the Engineering Division as a center for magnetics expertise.
The design phase was led by Dr. Helene Felice, then a scientist in the ATAP division at LBNL, leveraging in-depth expertise in advanced magnet structures from the HEP-funded high-field magnet program. Construction got underway after a successful design review in September 2014. BCMT staff, led by Dr. Diego Arbelaez of the Engineering Division, worked closely with the FRIB Front End team, led by Dr. Eduard Pozdeyev, and the FRIB ion source group, led by Dr. Guillaume Machicoane, to bring the project to fruition and ensure proper integration of the ECR magnet in its environment.
The design and realization of the magnetic fields is crucial because the performance of an ECR ion source relies primarily on the plasma density and confinement time. The plasma is produced within the magnet bore by heating of the electrons through the ECR phenomenon, driven by radiofrequency (RF) power. To build up the plasma density, strong confinement with a magnetic field is required. The strength of the confinement field has to increase with the ECR heating frequency. High intensity sources require correspondingly high frequencies (28 GHz in this case) and thus high magnetic fields. The combination of the solenoidal and sextupolar fields will provide a closed isomagnetic surface of at least 1.75 T in the magnet aperture.
“This magnet was a natural match for BCMT,” observed ATAP Division Director Wim Leemans, adding, “They bring depth and breadth of experience in the science and technology of magnets relevant to accelerators, and are especially well known for their know-how and leadership in the development and deployment of advanced superconducting magnets.”
The program offers expertise “from mesoscale to magnet” (that is, at all stages from the metallurgy of superconducting wire to the construction and testing of magnets) and an unequalled degree of integration of computerized design tools.
“This was an interesting challenge from both a magnetic-design and an engineering standpoint,” notes BCMT Director Soren Prestemon. The coils are made from niobium-titanium (NbTi), a familiar product used widely in accelerator applications.
The structure incorporates an innovation that has been extensively demonstrated since the days of the VENUS design: “key and bladder” assembly, which uses water-inflatable metal bladders (removed after assembly) and load keys inside the structure to provide compression to the sextupole structure at room temperature. This allows tunable pre-loading of the magnet to minimize conductor motion during magnet excitation. Such motion could result in quenches (sudden losses of superconductivity, which would trigger shutdowns). Differential thermal contraction of the support structure components during cool-down to the operating temperature (4.2 K) completes the preload. Thanks to this concept, the assembly of the sextupole magnet is fully reversible, allowing repair or replacement of a sextupole coil if necessary.
“Soren’s team has designed it not only to perform, but to be reliable and easily sustainable in a user facility,” says Henrik von der Lippe, Director of Berkeley Lab’s Engineering Division. “A product like this sums up what we’ve learned from everything else we’ve done.”
“I am delighted that LBNL has built, successfully tested, and delivered the superconducting cold mass magnet for the FRIB ECR,” adds Thomas Glasmacher, FRIB Project Director. “It has been a very good experience for us to work with the LBNL team on this magnet. I particularly appreciate the transparency with which the LBNL team has communicated with the FRIB team, and LBNL’s commitment to a high-quality product that was delivered within cost.”
A vision many years in the making
“FRIB has been a generation in the making for nuclear physics and nuclear astrophysics,” says James Symons, LBNL’s associate laboratory director for the Physical Sciences Area, which encompasses the ATAP, Engineering, Nuclear Science, and Physics Divisions. While the field is now firmly established at MSU, many of its roots can be traced through Berkeley Lab.
While chairing the joint DOE and National Science Foundation Nuclear Science Advisory Committee, Symons played a key role in the genesis of FRIB, which was given top priority for new construction in the committee’s 2001 Long Range Plan. Symons also chaired the committee that laid out the science case for the final design chosen for the facility design in 2006. The idea of a dedicated user facility can be traced three decades earlier, when the principal technique for producing the rare isotopes — fragmentation of heavier ones — was pioneered at LBNL’s Bevalac. Subsequently, the late LBNL nuclear scientist Mike Nitschke and Yale physicist Rick Casten championed the construction of a Rare Isotope Accelerator with which intense beams of short-lived nuclides not normally found in nature could be studied.
When it comes online in 2022, FRIB will bring capability to these experiments that was undreamed-of in the late 1970s when the Bevalac experiments were performed. “The secondary beams of the rare isotopes will be more powerful than the primary beams we had in those days,” says Symons.
Besides the ECR ion source concept and the magnets for it, LBNL is also leading one of the principal efforts at the other end of the facility: a detector called GRETA, the Gamma Ray Energy Tracking Array. The GRETA concept was prototyped as GRETINA, which was initially commissioned at LBNL’s 88-Inch Cyclotron, after which it was used at MSU’s National Superconducting Cyclotron Laboratory, and later at Argonne National Laboratory.
To learn more…
- Visit the FRIB website.
- View video materials posted by NSCL Media, including this 2011 talk by Dr. Symons at MSU that explains what users will study at FRIB and why this knowledge is important to our understanding of the world around us.
ATAP MAKES A “COSMIC” CONTRIBUTION AT ALS
The COherent Scattering and MICroscopy (COSMIC) Beamline at the Advanced Light Source is near the end of beamline commissioning, and the first science experiments will soon begin.
COSMIC, which saw “first light” in March, uses an elliptically polarizing undulator (EPU) that has a minimum gap of only 9.5 mm. This is the smallest gap of any out-of-vacuum insertion device at the ALS, and puts the magnets in the undulator very close to the electron beam in the storage ring. The vacuum chamber has a vertical aperture of only 7 mm.
Such a narrow chamber presents a number of engineering and technology challenges. The COSMIC vacuum chamber is the first NEG-coated chamber at the ALS. A NEG coating is a “non-evaporable getter” — a coating of alloys that adsorb gas molecules at their surface. It is a key enabling technology not only for small-gap undulators, but also throughout light sources such as the future ALS Upgrade (ALS-U). The small aperture allows both undulators and focusing magnets to be placed closer to the beam, but poses challenges in pumping the chamber down to the ultrahigh vacuum needed by a light source, hence the NEG coating.
|Counterclockwise from top left: The area during installation shows the small-gap NEG-coated vacuum chamber, which is a thin flat metal structure with a 7-mm vertical aperture inside; the vacuum chamber with the photon beamline from an upstream source in the background; and the COSMIC EPU on the blue-painted strongback structure to which the magnets are mounted.|
“The COSMIC project is exciting in that it not only enables vastly improved experimental capabilities, but also provides a significant step forward in accelerator technology at the ALS. The deployment of the first small gap NEG-coated vacuum chamber, as well as an EPU with much smaller gap, is a bridge to key technologies needed for ALS-U,” said Christoph Steier, deputy group leader of the ALS accelerator physics group and accelerator systems lead for ALS-U.
Beam commissioning of the undulator, as well as the vacuum system and protection systems, went quickly, confirming that the undulator and vacuum design work very well and the magnetic measurements and corrections met all requirements.
The result: new horizons for user science
The COSMIC beamline has two branches, one for scattering and one for microscopy, dramatically improving the capability of the ALS in two experimental techniques that will be critical for the science case for ALS-U.
The scattering branch’s primary scientific technique, x-ray photon correlation spectroscopy (XPCS), provides a method to study nanoscale fluctuations in materials as a way to better understand ordered phenomena, such as ferromagnetism and superconductivity.
The microscopy branch is designed for a type of microscopy called ptychography in which an image is calculated from coherent scattering data. This removes the resolution restriction placed on the imaging system by the x-ray optics, so that resolution is dependent only on the coherent flux. “Under the ideal situation, where we have very high-contrast samples, we’ll be able to image at the x-ray wavelength, which nobody else can do,” said David Shapiro, the lead scientist of the microscopy branch. “I think COSMIC is going to bring x-ray microscopy much closer to the capabilities of electron microscopy, but with the added benefit of x-rays, which is that you can penetrate lots of material.”
Team science takes a team
Members of the COSMIC team include Tony Warwick, Simon Morton, and Rich Celestre, under the leadership of Howard Padmore (beamline design); Jeff Takakuwa, Adrian Spucces, Troy Stevens, and Ken Chow (beamline engineering); and Sujoy Roy and David Shapiro (beamline scientists). The undulator work was led by Chuck Swenson, of the ATAP and Engineering Division’s Berkeley Center for Magnet Technology (BCMT), and the magnetic measurement work, as well as the design of the shims needed to minimize the negative effect the undulator would otherwise have on the dynamic aperture, was led by Erik Wallén, also of BCMT. The vacuum work, including this first installation of a NEG coated chamber in the ALS, was led by Swenson and Sol Omolayo. Accelerator and undulator commissioning was led by Tom Scarvie and Steier. Many of these scientists and engineers are also on the ALS-U team.
CRUNCH TIME WHEN THE CHIPS ARE DOWN FOR BACI PROGRAM’S MICROWAVE EXPERTISE
Creating snack foods requires science. PepsiCo recently teamed with Berkeley Lab to map the internal structural changes of starch pellets as they expand under microwave heating, to understand how to design the perfect crispy or crunchy bite. ATAP’s RF-technology expertise was key to these studies.
Microwave technology, vital to both particle acceleration and beam diagnostics, has long been a core area of expertise of ATAP. Yet (except in the breakrooms) we had never used them for their most common purpose worldwide—the very reason most people have heard the term “microwave” — namely, making food hot.
Last year PepsiCo financed a Chemical Sciences Division study of the structure of microwave-heated starch pellets during the cooking process, part of the company’s quest to understand cooking at the physics, chemistry, and materials-science level. This could ultimately serve as a basis for new snacks that are cooked with microwaves (possibly even in consumers’ homes) instead of with energy-intensive frying or baking processes. One of the capabilities Berkeley Lab brought to the table was ALS Beamline 8.3.2, capable of 3-D X-ray microtomography with few-micron resolution.
|Images reconstructed from continuous tomography data show the evolution of pores as a starch granule is microwaved—one of the properties that researchers need to understand when developing new products.|
Dr. David Shuh, the project’s principal investigator, asked Dr. Stefano De Santis of ATAP’s Berkeley Accelerator Controls and Instrumentation (BACI) Program to design, test, and operate a fixture that could be placed in a Beamline 8.3.2 end station. The fixture allowed researchers to study the expansion of the pellets and measure the power they absorbed while being microwaved for 30 seconds or so.
The frequency of microwave ovens, 2.45 GHz, is not routinely used in accelerators. Dr. Qing Ji of ATAP’s Ion Beam Technology Program helped get the experiment off the ground by loaning the team a magnetron for development and the initial runs at the ALS. Later, PepsiCo provided an easier-to-use solid-state amplifier with more-precise stability in its power and frequency.
Since the fixture had to allow easy insertion and replacement of the samples and their rotating support during measurements, it could not be completely enclosed in metal, and of course microwaves have to be contained for safety reasons. Therefore the ports used for sample insertion, X-ray passage, and visual inspection were designed with RF chokes to keep microwaves confined inside the fixture. Experts on non-ionizing radiation from Berkeley Lab’s Environment, Safety, and Health Division confirmed that the fixture was safe to use.
Based on initial experiences and the availability of a more stable microwave generator, de Santis and the team designed a second fixture. The first provided a traveling microwave field; the second, a standing-wave mode, which simulated the power density of a microwave oven at the sample location when using just a fraction of the full power.
|Original (left) and improved versions of the fixture.|
Both fixtures were machined from a solid aluminum billet by Tyler Sipla, an Engineering Division technician matrixed to ATAP. His expertise with a computerized numerical control (CNC) machine tool was key to staying on the strict schedule dictated by the availability of the highly subscribed beamline. The second fixture was instrumented with a power probe with the help of another Engineering technician who works in ATAP, Kerri Campbell.
“It’s a great example of how team science works,” said ATAP Director Wim Leemans. “Several people from around ATAP and Engineering pulled together to support another division’s research at one of the Lab’s user facilities.”
Alas, the experiment resulted in R&D data, not snacks for hungry scientists — at least for now. But perhaps someday, much as the taste of a madeleine brought back a flood of memories for Marcel Proust, the crunch of a chip will inspire recollections of a job well done.
To learn more…
Visit the Beamline 8.3.2 web page.
NEWS IN BRIEF
FS&IBT Technology is a First-Pitch Hit
Dr. Thomas Schenkel has won the inaugural LBNL Pitch Competition, held Nov. 3 by LBNL’s Innovation and Partnerships Office (IPO).
Schenkel, ATAP’s Division Deputy for Technology and head of the Fusion Science and Ion Beam Technology Program, won with his pitch for MEMS-ACCEL. A miniaturized ion acccelerator developed in collaboration with Cornell University, MEMS-ACCEL is also a finalist in this year’s R&D 100 competition.
|On pitch: From left, ATAP researchers Thomas Schenkel (representing the team in the competition), Arun Persaud, Peter Seidl, and Qing Ji.|
In the Pitch Competition, nine research teams with entrepreneurial prospects from across the Laboratory put forth their business case in front of a panel of experts — a process familiar on the road to the marketplace, and for which they have been trained through opportunities like IPO’s I-Corps program.
Schenkel went on to represent Berkeley Lab in a 9-entrant DOE-level I-Corps pitch competition on Nov. 29.
“Communication skills play a big part in bridging the gap between R&D and industry,” says ATAP Director Wim Leemans,” adding, “I’m looking forward to seeing Thomas represent us at the DOE level — and to the problems that the technology itself can solve. Efforts like this make the private sector more aware of it, and that’s a win for everyone.”
AMPing Up the Cover Story of CERN Courier
ATAP’s Accelerator Modeling Program (AMP) provided the cover image for the December 2017 issue of the CERN Courier. The accompanying article describes the first in a series of workshops for developing an Advanced and Novel Accelerators for High Energy Physics Roadmap (ANAR). The workshop, held at CERN in April, focused on high-energy physics applications of advanced and novel accelerators. One such accelerator concept, the laser wakefield accelerator, is being developed at our Berkeley Lab Laser Accelerator Center (BELLA).
The cover shows excitation of a wakefield behind a laser driver, simulated using the particle-in-cell code WARPX. The laser pulse is indicated by alternating dark-blue and dark-red spheroids. Yellow/white areas have more plasma electrons; blue/green, more plasma ions.
BELLA Center’s Daniels, Mittelberger Are ATAP’s Latest PhDs
Two BELLA Center graduate students, Joost Daniels and Danny Mittelberger, are graduate students no more after receiving their doctorates in physics.
|Daniels (far left) earned his degree from Technical University Eindhoven, where his faculty advisor was Professor Jom Luiten. Dr. Wim Leemans was his research advisor at LBNL. Daniels’s dissertation was on “Measuring and modifying plasma density profiles to confine high power lasers.”
Mittelberger (near left) is graduating from the University of California, Berkeley. His dissertation was on “Optimization of a Laser Plasma Accelerator through Pulse Characterization and Controlled Spatiotemporal Coupling,” under faculty advisor Prof. Marjorie Shapiro and research advisor Dr. Wim Leemans.
DIVERSITY, EQUITY, AND INCLUSION
Considering Access When Choosing a Meeting Room
|When arranging a meeting, it’s important to make sure that all attendees find the room physically accessible. A Labwide effort is underway to help.
The Facilities Department has teamed up with All Access, the Laboratory’s Disability Inclusion Employee Resource Group, to assess the overall accessibility of all conference rooms across the site. Heading the project is Misha Gonzalez, co-chair of All Access and an architect in the Facilities Division. She is tasked with architectural system oversight and Americans with Disabilities Act compliance across the Laboratory.
Information collected by the project will be added to the Lab’s online database of conference rooms so that meeting organizers can select an appropriate venue. Both big-picture aspects and details can be important in accessibility; important data include accessible parking spaces and to shuttle bus stops, intervening stairs, the widths of doors, and even the type of door handle. (The database also includes other useful and practical information, such as the type of projector available, whether there is a whiteboard, etc.) The conference rooms in building 71 were recently assessed by Gonzales, together with ATAP’s Outreach and Diversity Coordinator, Ina Reichel.
“Our goal is to survey each room, systematically assess the various mobility factors and then assign an “ease of access” rating to the room,” Gonzalez said. “This will help meeting organizers better decide if a space meets the needs of all attendees. And we hope it will get more people thinking about obstacles that can prevent everyone from participating in meetings and events.”
To learn more…
If you would like to help, please contact Misha Gonzales ([email protected]). The goal is to complete the assessment of all rooms by the end of February.
Visit the Berkeley Lab Diversity, Equity, and Inclusion Office website to explore the Laboratory’s full range of efforts in this area.
SAFETY: THE BOTTOM LINE
Cylinder Securement: The Chain of Safety
Compressed gas is very useful in our research, but gas cylinders contain a lot of stored energy that can be hazardous when released suddenly — say, if a cylinder falls and its regulator breaks off. A high-pressure cylinder can fly like a rocket, smashing whatever (and whoever) it hits and distributing its contents (which might be hazardous in their own right) into the air. It is important to protect our safety by securing gas cylinders.
The right ways to secure cylinders
|Chains. For standard-sized cylinders, use two chains, one across the top third and another across the bottom third. For small cylinders (less than 1 m tall) a single chain across the middle will suffice. The chains must be snug across the bottle and well secured at their ends to the wall or something else suitable.|
|Racks of the correct size are another good way to securely store cylinders.|
|Fully enclosed cages may be used if the cylinder and contents are meant for horizontal storage (acetylene tanks, for instance, must be kept vertical.)
For in-use cylinders, a cart designed for the purpose, with safety chains to secure the cylinder to the cart and to secure the cart itself, is a safe home for all that potential energy (right).
Cylinders that are not in use should be stored with the protective cap over the valve.
Finally, full-sized, gas cylinders are heavy — move them with a cylinder cart (to which they are secured with chains) and stay within your physical limits. Additional tips and important LBNL rules for cylinder handling are available through the online course EHS 0171, Pressure and Compressed Gas Safety.
Test your knowledge: what’s wrong with this picture?
(Scroll down for answers)
A. The small gray cylinder is unrestrained on an open shelf. It could easily roll off.
B. The green cylinder is restrained with a flammable strap. The cylinder would fall in the event of a fire.
C. The red and green cylinders are restrained at the neck and could slide out. Securement should be done around the girth of the cylinder (one chain halfway up for small cylinders, less than 1 m tall; two chains, one each across the top and bottom thirds, for standard-height cylinders).
D. The cart is not attached to any solid structure. It could fall over.