Francis Bitter Magnet Laboratory
The Francis Bitter Magnet Laboratory (FBML) has continued to make notable advances in several areas of science and engineering involving high magnetic fields. The research program in magnetic resonance—nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR)—has continued to grow and remains the largest effort at the FBML. The program is funded primarily by the National Institutes of Health and the Department of Energy, and involves 28 NMR and EPR magnets and spectrometers.
Highlights
Professor Robert G. Griffin and Professor Gerhard Wagner of Harvard University continue to operate the MIT/Harvard Center for Magnetic Resonance, a collaborative research effort of MIT and Harvard Medical School. The center is supported by an NIH Research Resource grant. This grant was reviewed very favorably in November 2003 and funded again for an additional five-year period (May 2004 through April 2009).
Dr. Chandrasekhar Ramanathan has been hired as a research scientist working with Professor Cory and Dr. Havel on experimental aspects of quantum information processing and quantum complexity. Sekhar is an expert in magnetic resonance along with its applications both in the solid state and to spatial studies.
Professor Cory, Doctors Havel and Ramanathan and their colleagues continue to make advances in the theory, practice, and implementation of quantum information processing. Over the past year they have developed an efficient means of generating pseudorandom quantum states. These have applications in cryptography and the verification of coherent control.
The journal Quantum Information Processing, published by Kluwer Academic with Professor Cory (editor in chief) and Dr. Havel (managing editor), has completed its first year of publication. QIP is an international forum for the publication of peer-reviewed papers on all aspects, theoretical and experimental, of quantum information processing.
The Magnet Technology Division successfully completed the first phase of a three-phase 1-GHz NMR magnet project. A 350 MHz/55 mm NMR magnet completed in phase one is the world's first NMR magnet comprised of a low-temperature superconducting (LTS) magnet and a high-temperature superconducting (HTS) insert. In June 2003 the MTD was awarded a grant from the NIH Center for Research Resources to proceed with the second phase of this three-phase project. Also successfully completed by the MTD is the world's first digital flux injector, a full-scale version of which may be coupled to a "slightly" dissipative NMR magnet and used to periodically inject a precisely metered amount of flux into the magnet. This will enable the magnet to operate effectively in persistent mode and maintain its required temporal stability requirements.
Dr. Jagadeesh Moodera has continued to strengthen his research efforts in condensed matter physics through collaboration with various universities and industries, as well as the ONR and NSF. In addition, he has continued his mentoring of graduate students, undergraduates, and high school students by providing research opportunities within his lab. Dr. Moodera is the cochairman of the Gordon Research Conference on Magnetic Nanostructures meeting for the coming year and chairman for the following one.
Research Activities
Professor David G. Cory
Quantum Information Processing
Professor Cory and his students continue to explore NMR approaches to quantum information processing through a set of collaborations with Dr. Timothy F. Havel (NED), Dr. C. Ramanathan (NED), Professor Seth Lloyd (Mechanical Engineering), Professor Eddie Farhi (Physics), Dr. Raymond Laflamme (University of Waterloo), Dr. E. Knill (LANL), Dr. J. Yepez (AFRL). Last year's work has resulted in an improved understanding of coherent control for incoherent systems, better models of decoherence for quantum information processors, and the introduction of statistical measures of control. We have initiated studies of coherent control in electron/nuclear spin systems and have proposed a program of coherent control between ensembles of nuclear spins and cavity modes of a coherent superconducting oscillator.
NMR of Heterogeneous Semisolids
In collaboration with Dr. S. Singer (Memorial Sloan-Kettering Cancer Center), Dr. Pabitra Sen (Schlumberger Doll Research Laboratory) and Dr. R. Walsworth (Harvard Smithsonian) we have continued to explore the structure and fluid dynamics of complex media. This work has applications from soft tissue sarcomas to enhanced oil recovery.
NMR Resource for Neuroscience
In collaboration with the McGovern Institute we have started to assemble a MRI resource for MIT faculty engaged in neuroscience (or more generally for small animal imaging). This builds on our development of an NMR microscope (with Dr. Alan Jasanoff, a Whitehead fellow) and includes the further development of animal imaging capabilities on a 4.7T 40 cm bore MRI. We plan to add a higher field (9.6T) imaging system optimized for mice.
Professor Robert G. Griffin
High Frequency Electron Paramagnetic Resonance
The 140 GHz pulsed electron paramagnetic resonance (EPR) spectrometer is routinely used for Echo Detected (ED) experiments as well as Electron Nuclear Double Resonance (ENDOR). In particular, the ENDOR experiment is used to measure protons and also low gamma nuclei such as deuterium. We recently demonstrated the high resolution of the ENDOR experiment by measuring the coupling arising from a hydrogen bond of an exchangeable proton to the tyrosyl radical in Ribonucleotide Reductase (RNR) from yeast. The analysis included an estimate of the bond length and orientation. All measurements were done at low temperature with a new flow cryostat, which operates in the range of 1.2 to 420K. In addition, over the past year we have enhanced the capabilities of the instrument with the addition of corrugated waveguide.
Structural Studies of Amyloid Peptides and Proteins
Amyloidoses are a group of disorders due to peptide or protein misfolding and characterized by the accumulation of insoluble fibrillar protein material in extracellular spaces. Sixteen different proteins are known to form amyloid-like aggregates involved in several diseases. ß-amyloid (Aß) in Alzheimer's disease, the prion protein PrPc converts to PrPsc leading to the transmissible spongiform encephalopathie, and the synuclein protein is responsible for Parkinson's disease.
During the last two years, we developed methods to obtain large amounts of fibrillar peptide material and to maintain this material in a state suitable for MAS NMR experiments. We have used these techniques in a collaborative study of the structure of 11 residue fibrillar peptides in collaboration with Professor Cait MacPhee and Professor Chris Dobson of Cambridge University. The peptides are derived from transthyretin and to date have yielded excellent spectra. The spectra were assigned and several structural measurements performed yielding 76 constraints, which led to a structure described in a recent paper in PNAS. We are currently extending these studies to larger systems with the intention of performing structures of three different proteins in the form of amyloid fibrils. Once these structures are known then it is possible to design drug-based therapies that might prevent fibril formation.
Dynamic Nuclear Polarization
The 140 and 250 GHz DNP spectrometers continue to operate reliably and routinely, allowing us to pursue new applications of DNP. Significant advances have been made in combining MAS with DNP and in the development of new polarizing agents. Specifically, we have improved many aspects of the 250 GHz system, so that it is now capable of recording spectra at low temperatures for extended periods. Results of these efforts are just beginning to be realized. The new polarizing agents that we have developed in collaboration with Tim Swager of the MIT Chemistry Department consist of biradicals—two TEMPO molecules tethered by a polyethylene glycol chain. Because of the increased dipole coupling and the favorable orientation of the g-tensors they yield signal enhancements that are larger by a factor of four over monomeric TEMPO. In collaboration with the MIT Plasma Science Fusion Center, we have constructed and are testing a 460 GHz gyrotron that will be used in conjunction with the 700 MHz widebore magnet
Dipolar Recoupling
Over the last decade we have been heavily involved in the development of techniques to measure distances and torsion angles in solids. The goal is to be able to determine the structure of membrane proteins, amyloid fibrils, etc. with solid state NMR. This past year we developed a method for simultaneously measuring multiple 13C-15C distances in uniformly labeled materials, and demonstrated the method successfully on a small peptide. This is a complementary approach to measuring distances 13C-15N distances used in our amyloid experiments. We anticipate that with increased sensitivity available from DNP experiments, these methods will be applicable to a large number of systems not accessible to solution NMR and X-ray crystallographic investigations.
Center for Magnetic Resonance
The Center for Magnetic Resonance has completed its 27th year of operation as a facility providing scientists with access to high field NMR equipment. During this year, 38 projects were worked on by 76 investigators, from departments within MIT including Chemistry, Physics and Nuclear Engineering, as well as users and collaborators from institutions outside of MIT, such as Harvard University, Brandeis University and Massachusetts General Hospital. Work resulted in 43 publications in print or in press.
Highlights of work conducted at the center include advances in high frequency dynamic nuclear polarization with magic angle spinning (MASDNP), structure determination of large proteins, and high frequency EPR and ENDOR.
The Center for Magnetic Resonance recently received approved funding from NIH for a 900 MHz spectrometer. The 900 will be operated as part of the CMR. In addition we anticipate applying for widebore 800 MHz NMR systems in the next year or two. The renewal of the CMR grant this past fall will also support the development of 330 GHz tunable gyrotrons and low temperature MAS probes for use with 500 MHz spectrometers.
Dr. Yukikazu Iwasa
Dr. Iwasa is involved in research and development of superconducting magnet technology, particularly of high-temperature superconductors (HTS). Specific HTS-related projects in which the Magnet Technology Division (MTD) is currently involved include: development of a digital flux injector (previously called a flux pump) for NMR superconducting magnets that incorporates HTS inserts; the first phase of a three-phase program to complete a 1-GHz NMR magnet that includes an HTS insert; study of stability/protection of HTS magnets used in electric power devices; and the development of a "noise-free" NMR magnet system. The "noise-free" magnet system applies solid nitrogen technology recently developed by the MTD. These projects are briefly summarized below.
Digital Flux Injector (Flux Pump) for NMR Superconducting Magnets
The digital flux injector (DFI) is considered a viable technology for achieving magnetic fields corresponding to 1-GHz 1H NMR operating frequency. By allowing precisely metered quantities of magnetic energy to be injected into a slightly dissipative superconducting coil, e.g., an HTS insert coil in a 1-GHz magnet system, a DFI can make the dissipative coil operate in an effectively persistent mode.
Since June 1, 2000, we have designed, built, and successfully operated a model flux pump to confirm its experimental results with analysis. In June 2003, our five-year continuation program on the development of DFI our continuation program received a priority score from the NIH Study Session that is considered fundable. We expect to start on this continuation program beginning in 2004.
HTS Insert Coil for 1-GHz NMR Magnet
After successfully completing the first NMR magnet comprised of a low-temperature superconducting (LTS) magnet and a high-temperature superconducting (HTS) insert coil that produced NMR signals at 350MHz, the MTS began, in June 2003, the second phase of a three-phase project to complete a high-resolution 1-GHz NMR magnet. In phase two, our goal is to complete a 675MHz NMR magnet comprised of a 600MHz all-LTS NMR magnet and a 75MHz HTS insert coil. We expect to complete phase two in March 2006.
Stability/Protection of HTS Magnets
The large heat capacity of solid nitrogen impregnating the winding of an HTS magnet in an electric power device limits the temperature rise in the HTS winding subjected to fault-mode overcurrent pulses. We are investigating quench/recovery processes of YBCO-coated tape. Each YBCO test sample, supplied by the American Superconductor Corporation of Westborough, Massachusetts, is subjected to transient heating applied to test sample in the form of an over-current pulse having an amplitude of two to six times the short current critical current of the YBCO test sample and a duration lasting about 100ms. At the present time, each test sample is immersed in a bath of liquid nitrogen. Also being investigated is an acoustic emission technique to detect a localized "hot spot" created in YBCO test samples. This work will continue at least through the middle of 2004.
"Noise-Free" MRI Magnets
In 2003, we submitted two research applications to build two types of MRI magnets, both cooled by solid cryogen. In the first application, we proposed to build a 500MHz/20cm room temperature bore MRI magnet. The magnet body contains a volume of solid neon. The nominal operation is at 4.2K with its cryocooler running; the solid neon enables the magnet to operate in the temperature range 4.2–6.0K with its cryocooler decoupled from the system, over a period of 12 hours, This solid neon operation provides a "noise-free" measurement environment and also protects against the loss of operating field in the event of a power outage. The second application is similar to the first, except here we proposed to build a prototype MRI magnet with MgB2, a high-temperature superconductor with a critical temperature of 39K. Solid nitrogen will be used in this system. The magnet's nominal operating temperature is 10K, with a provision to operate in the range 10–15K when decoupled from its cryocooler.
Dr. Jagadeesh S. Moodera
In condensed matter physics, in particular, magnetism as well as superconductivity, our research continues to make significant contributions to both fundamental science and industrial application.
Our basic investigation emphasizes spin transport in thin film structures. Using our molecular beam epitaxy (MBE) system, our research seeks to contribute to the understanding of the spin properties of conventional materials and to unraveling the spin properties of certain novel magnetic compounds that have a high potential for technological application. Our research in these materials is further developed by various industries such as IBM, HP, Motorola, Seagate, TDK and Fujitsu in this structure for application in digital storage. They have reached prototype devices: readhead sensors for over 100Gbits/sq storage as well as nonvolatile magnetic random access memory (MRAM) elements that will potentially have a large impact on memory technology which runs into hundreds of billions of dollars. In this context, we are continuing national and international collaborative research efforts with scientists and faculty from national laboratories, US universities, the University of Paris at Orsay, the University of Eindhoven, Tohoku University, Tata Institute of Fundamental Research, Korea Institute of Science and Technology as well as the Ukrainian Academy of Sciences. Exchange of scientists and graduate students is a part of this program.
We have successfully developed a research program in the new superconductor (MgB2) science and technology for Josephson junctions that have the potential for hybrid superconducting electronics in areas such as computers, logic elements, mixers switches and sensors. In the area of semiconductors, our continued collaboration with Hewlett-Packard Company has been valuable in searching for far future material for atomically resolved storage (>Terabytes/in2). We explored the materials with the appropriate properties and gave Hewlett-Packard the fundamental information necessary for their program. In this direction we have been successful in identifying a possible candidate material from among thousands of compounds. We have recently started out a similar program with another company. There is ongoing collaboration with other companies, such as NVE Inc., in the field of magnetism.
We have also started research programs in the fields of nanoscience for single spin transistors as well as the materials aspect for quantum computing. In a parallel approach, we are also investigating injecting spins into semiconductors. Another program we just embarked on is a new approach to read the Q-bit information using quantum dot structure and spin filter approach.
Four postdoctoral scholars, two graduate students, two undergraduates and ten high school students have taken part in Dr. Moodera's research. The high school students have won several science competitions, including a regional finalist in the Intel-Westinghouse Science Competition, as well as other regional and top state level awards. Several of the high school students have joined MIT undergraduate program. Research resulted in several publications and invited talks at various national and international conferences, universities and laboratories.
Dr. Moodera continues his collaboration with Eindhoven Technical University (Holland) as a visiting professor. He is the expert reviewer/advisor for a spin related nanotechnology program in Korea Institute of Science and Technology. He has taken part at the national level magnetism committee policies and meeting initiatives, as well as serving on the scientific board of international meetings. He is the cochairman for the upcoming Gordon Research Conference on Magnetic Nanostructures.
Facilities
Renovations are currently underway for the magnet cell accommodating the 700/89 system. Renovations are soon to begin for the 900MHz instrument.
Education and Personnel
The laboratory contributes to undergraduate education by participation in the Undergraduate Research Opportunities Program (UROP) a program that encourages and supports research-based intellectual collaborations of MIT undergraduates with Institute faculty and research staff. In addition, the laboratory has 20 full-time graduate and 20 postdoctoral fellows performing research.
Future Plans
We are discussing plans to place a 3-Tesla imaging system on the first floor of NW14. The system will be used by investigators from the Department of Brain and Cognitive Science and others interested in functional magnetic resonance imaging.
In the longer term we also plan to complete construction of the second floor magnet hall, and instruments currently housed on the fourth and fifth floors will be relocated in order to create a comprehensive center for magnetic resonance.