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 NIH and DOE, and involves ~20 NMR and EPR magnets and spectrometers.
A few of this year's highlights:
- Professor Robert G. Griffin, together with Professor Gerhard Wagner of Harvard University, continue to operate The MIT/Harvard Center for Magnetic Resonance, a collaborative research effort between MIT and Harvard Medical School. The center is supported by a NIH research resource grant that was renewed for five years.
- Professor Cory, Dr. Havel and their colleagues continue to make advances in the theory, practice and implementation of quantum information processing. In particular they have implemented a solid state version of an NMR quantum information processor that promises to provide more precise control over larger Hilbert spaces than is available in the liquid state.
- Professor Cory (editor in chief) and Dr. Havel (managing editor) have formed a new journal, Quantum Information Processing, published by Kluwer Academic. QIP is an international forum for the publication of peer-reviewed papers on all aspects, theory and experimental, of quantum information processing.
- Dr. Yukikazu Iwasa has successfully operated the first flux pump—a digitally flux injector—for use in slightly dissipative NMR magnets. Dr. Iwasa has also completed the first low- and high-temperature superconducting NMR magnet.
- 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, undergraduate and high school students by providing research opportunities within his lab. Dr Moodera has been elected as the co-chairman of the Gordon Research Conference on Magnetic Nanostructures meeting for the next four years.
Professor David G. Cory
Quantum Information Processing (QIP)
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), Professor Seth Lloyd (Mechanical Engineering), Professor Eddie Farhi (Physics), Dr. Raymond Laflamme (University of Waterloo), Dr. E. Knill (LANL), and Dr. J. Yepez (AFRL). We have developed new means of coherent control (in the presence of decoherence and incoherent interactions) that achieve experimental fidelities of 0.99.
We have constructed a new scheme for extending the success of NMR approaches to QIP to larger systems via a solid state device capable of coherently controlling 10–30 qubits. We are using this scheme to explore quantum complexity and the transition from quantum to classical dynamics.
We have investigated quantum chaos with the aims of developing experimental signatures which differentiate regular from chaotic dynamics, and showing the connection of chaotic couplings to an environment with decoherence.
We have defined and experimentally implemented a new model of quantum decoherence that requires a minimum number of quantum resources. This system is coupled to a simulated quantum environment that is periodically and randomly re-dressed to introduce user-defined decoherence.
NMR of Heterogeneous Semi-Solids
In collaboration with Dr. S. Singer, and Dr. Pabitra Sen of Schlumberger Doll Research Laboratory, we have continued to explore the structure and fluid dynamics of complex media. The heterogeneity of the sample itself sets up a signature of the local geometry which provides a simple and direct means of characterizing micron scale structures. Knowledge of this provides insight into cellular differentiation and fluid transport through complex structures.
NMR Imaging of Neuron Structure and Function
Dr. Alan Jasanoff (a Whitehead fellow at MIT) has developed the tools to enable the neuron structure and response of blow flies to be explored at high resolution via NMR microscopy. The use of blow flies provides a stable and well characterized test bed, while simultaneously permitting near cellular resolution in the NMR. This in turn enables the observation of neuron activity in living/functioning tissue with the markers being directly traceable to neuron biochemistry. Dr. Jasanoff is developing a series of exodenous markers of biochemical response for neuroscience.
Professor Robert G. Griffin
A web site describing some of our research can be found online at http://web.mit.edu/fbml/cmr/griffin-group/.
High Frequency Electron Paramagnetic Resonance (EPR)
The 140 GHz pulsed 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.
Structural Studies of Alzheimer's Disease Amyloid
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 peptides are known to form amyloid-like aggregates, and are involved in several diseases. ß-amyloid (Aß) in Alzheimer's disease; the prion protein PrPc, converting to PrPsc and leading to the transmissible spongiform encephalopathie; and the synuclein protein, 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-mer fibrillar peptides in collaboration with Professor Chris Dobson of Cambridge University. The peptides are derived from transthyretin and to date have yielded excellent spectra. We are presently in the process of assigning these spectra and plan by next year to have a structure of a fibrillar system.
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. In the past year, one- and two-dimensional MAS/DNP spectra have been measured at both field strengths on a variety of samples ranging from amino acids to membrane protein systems. Sensitivity enhancement factors in the range of 50 to 60 have been achieved at ~90K, and we are developing a MAS system for lower temperatures to bring further sensitivity gains. A new project is underway, with promising results even at this early stage, in the application of DNP sensitivity enhancement to solution-state NMR. Signal enhancements of ~150 have been obtained for 31P in a solution of triphenyl phosphine at 5T. At present these represent the highest frequency DNP experiments ever performed, and more importantly suggest that even higher frequency operation will be successful. In collaboration with the PSFC we have designed and are constructing a 460 GHz gyrotron that will be used in conjunction with the 700MHz widebore magnet
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-15N distances in uniformly labeled materials, and demonstrated the method successfully on a small peptide. We are also developing methods for measuring 13C-13C distances in uniformly labeled materials. 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 26th year of operation as a facility open to scientists needing access to high field NMR equipment. During this year, 38 projects were worked on by 81 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 Brigham and Women's Hospital. Work resulted in 46 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, studies of long range order in unfolded proteins and high frequency EPR and ENDOR.
The Center for Magnetic Resonance recently received approved funding from NIH for 900 MHz spectrometers. The 900s will be operated as part of the CMR. In addition we anticipate applying for widebore 800 NHz NMR systems in the next year or two.
Dr. Yukikazu Iwasa
We are involved in research and development of superconducting magnet technology, particularly of high-temperature superconductor (HTS). Specific HTS-related projects with which the Magnet Technology Division (MTD) is currently involved include development of a flux pump for NMR superconducting magnets that incorporates HTS inserts; phase 1 project of a three-phase, six-year 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; development of a "noise free" NMR magnet system. Topics 4 and 5 apply solid nitrogen technology recently developed by the MTD. These projects are briefly summarized below.
Flux Pump for NMR Superconducting Magnets
Flux pump is considered a viable technology for achieving the 1-GHz milestone. 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 flux pump 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. Presently, we are designing a prototype flux pump that will be coupled to a Phase 1 LTS/HTS NMR magnet presently under construction in the MTD, described below.
HTS Insert Coil for 1-GHz NMR Magnet
The MTD is presently undertaking phase 1 of a six-year, three-phase project to complete a high-resolution 1-GHz NMR magnet. In each phase, an HTS insert coil will be designed, built, and operated in a background LTS magnet. Since October 1, 2000, we have nearly completed the phase 1 system and are ready to begin the phase 2 system in early 2003.
Solid Nitrogen Technology
The large heat capacity of solid nitrogen in the temperature range 10–60K is considered beneficial for operation of HTS magnets in some applications.
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 subject to transient heating in the presence and absence of a minute amount of solid nitrogen in the HTS winding.
"Noise Free" NMR Magnet
A "noise free" magnet/cryocooler NMR system incorporates solid nitrogen in the system. The large heat capacity of the solid nitrogen permits "noise free" operation of an NMR system with its cryocooler idled over a period long enough for measurement. (Microphonics from the running cryocooler precludes microscopic scattering measurements.) Starting June 1, 2001, we began development of a commercially viable compact NMR magnet system based on this concept as an NIH STTR phase I project in collaboration with American Magnetics, Inc., Oak Ridge, Tennessee.
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 companies 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 and 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 are exploring the materials with the appropriate properties and giving HP 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. There is ongoing collaboration with other companies such as NVE Inc., in the field of magnetism.
A new superconductor (Al/Ga) has been synthesized that is found to be highly useful as a spin detector for spin polarized tunneling. This we achieved by carefully tuning the interface structure down to a monolayer level in a bilayer thin film structure.
We have also started research programs in the fields of nanoscience for single spin transistors as well as the materials aspect for quantum computing.
Four postdoctoral scholars, two undergraduates and ten high school students have taken part in Dr. Moodera's research. One of the undergraduates did her BS thesis (won the best thesis award in DMSE) and another one has carried out a project for his BS degree under the PI's supervision. The high school students have won several science competitions, including a regional finalist in Intel-Westinghouse Science Competition, as well as other regional and top state level awards. (One HS student is continuing her project now at Trinity College in Ireland.)
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 has taken part at the national level magnetism committee policies and meeting initiatives, as well as serving in the scientific board of international meetings. He was elected as the cochairman for the upcoming Gordon Research Conference on Magnetic Nanostructures. An Electronics Journal reporter from Korea extensively interviewed the PI for a series of articles on nano electronics and molecular level electronics. A reporter from Wire Technology about digital storage and communication technology based on magnetic memory also interviewed him.
During the past year, we have started the renovation process for the magnet cell to accommodate the 700/89 system. We are also beginning to discuss the renovations for the 900 MHz instruments.
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.
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.