Bridge12 Founders provide exclusive Questions and Answers to readers of Terahertz Technology, regarding Dynamic Nuclear Polarization, and about the company

(Co-Founders of Bridge12, Dr. Thorsten Maly, and Dr.Jagadishwar Sirigiri)

MY NOTE: The following are questions, I submitted to Dr. Thorsten Maly to consider answering to better explain to the lay community, precisely what Bridge12 does. Remarkably, he has been

generous enough to do, and here are the questions and answers. 







  Terahertz Technology Q&A

  Bridge12 Technologies, Inc. http://www.bridge12.com/  is a high-tech start-up formed by former scientists of the Massachusetts Institute of Technology (MIT). Its core expertise is in the area of high-frequency terahertz (THz) instrumentation for applications in Science, Medicine, Security and Defense, with its current focus on THz instrumentation for DNP-enhanced NMR spectroscopy. The company recently received a SBIR grant from the U.S. National Institutes of Health to develop a compact, cost-effective gyrotron system for DNP-enhanced solid-state NMR spectroscopy.

1. Why the name Bridge12?

  Many people ask us this question. Despite several valuable applications, the adoption of THz waves has been slow because of the limited output power of currently available THz sources. Today moderate size sources can only generate a few milliwatts of continuous wave (cw) power and therefore, systems employing such sources require sophisticated signal detection schemes. The lack of commercially available instrumentation (sources, detectors etc.) in the THz region led to the term “Terahertz Gap”.

  Bridge12 is committed to close this gap. Overcoming current technology barriers, we close the Terahertz Gap by providing compact, high-power, turn-key THz sources and instrumentation that are cost-effective, efficient and rapidly deployable.

2. What kind of products does Bridge12 offer?

  The gyrotron is our flagship product. Our unique, standardized tube design allows us to offer gyrotrons with a wide range of operating frequencies (100 GHz to 1 THz), large tuning bandwidth and high output-power (>10 W).

  Besides gyrotrons, we offer high-frequency, low-loss corrugated transmission lines and other THz components such as miterbends, waveguide adapters and extensions, power monitors and microwave windows. Furthermore, we offer a THz consulting services for customers that need advice for designing and developing THz systems for various applications.

3. What is a gyrotron and how does it work?

  A gyrotron is a vacuum electronic device (VED) capable to generate high-power, high-frequency THz radiation. Its operation is based on the stimulated cyclotron radiation of electrons oscillating in a strong magnetic field typically provided by a superconducting magnet.

  In a gyrotron, an electron beam is accelerated by a high voltage in a strong magnetic field of a superconducting magnet. While the electron beam travels through the intense magnetic field, the electrons follow a corkscrew trajectory (they gyrate) with a frequency given by the strength of the magnetic field. In the cavity, located at the position with the highest magnetic field strength, the THz radiation is generated and extracted by a waveguide. The spent electron beam is then dissipated in the collector.

4. What is so special about the Gyrotron?

  The gyrotron is a so-called fast-wave device because the dimension of its interaction structure is much larger compared to the wavelength of the radiation. This is in contrast to slow-wave device, which have interaction structures that are of the order of the wavelength of the generated radiation. However, especially at high frequencies, these interaction structures can be very small (sub millimeter) and therefore can easily burn out at the high power densities required to generate sufficient output power, significantly limiting the lifetime of the tube.

  Since gyrotrons are typically operated in a higher mode the interaction structure (cavity) can be much larger compared to the wavelength of the radiation. Furthermore, the cavity is typically a metal tube (copper) and can be effectively cooled, due to its simple structure. Therefore, the gyrotron can provide high output power, at high frequencies and guarantees a long lifetime.

5. What is the main application of your gyrotrons?

  In general, the gyrotron can be used in all scientific areas that require high-power, high-frequency THz radiation. At Bridge12 we are currently working on several applications in the area of science, medicine, security and defense. One application that currently gets a lot of attention is Dynamic Nuclear Polarization (DNP) for Structural Biology and herein the structure determination of bio-macromolecules by DNP-enhanced solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.

6. What is Dynamic Nuclear Polarization?

  Currently NMR and X-ray crystallography are the two methods to determine structures of bio-macromolecules such as proteins and enzymes. These structures for example play an important role in the drug development process of the pharmaceutical industry. Briefly, in a NMR experiment, a sample is placed in a strong magnetic field and irradiated with intense radio frequency fields. When placed in a magnetic field, nuclei such as protons (¹H) or carbon nuclei (¹³C) absorb at a characteristic frequency, proportional to the strength of the external magnetic field. For example, at a magnetic field of 14 Tesla (2,800,000 times stronger than the earth’s magnetic field) protons resonate at a frequency of 900 MHz. Since the local magnetic fields at the position of the studied nuclei are very sensitive to their environment, small deviations of the resonance frequency (ppm regime), can be used to extract structural information about the surrounding of the nuclei. Furthermore, distance measurements between individual nuclei can provide geometrical information, which can be used to calculate molecular structures.

  However, NMR has a major drawback; due to the very small nuclear magnetic moment of the nuclei studied by NMR, the method is inherently insensitive. Therefore, NMR experiments to determine structures of large bio-macromolecules require several days to weeks of signal averaging to achieve an acceptable signal-to-noise ratio. In contrast, the magnetic moment of electrons is much larger, due its lower mass. For example, while for protons the characteristic absorption frequency at 14 Tesla is 600 MHz, the electron resonance frequency is 396 GHz at the same magnetic field strength. For NMR spectroscopy, larger magnetic moments (and polarization) translate directly into larger signal intensities. Therefore, transferring polarization from electrons to nuclei can greatly enhance signal intensities in NMR spectroscopy and dramatically reduce acquisition times in NMR experiments.

  Dynamic Nuclear Polarization (DNP) can achieve such a polarization transfer by on-resonant microwave (terahertz) radiation. With DNP signal enhancements of factor 100 or larger can be achieved, resulting in factor 10,000 shorter acquisition times and experiments that typically require days to weeks of signal averaging periods can be performed in just minutes or hours.

7. Are there other applications for your gyrotron?

  Currently our main focus is on the development of compact and cost-effective gyrotrons for DNP-enhanced NMR spectroscopy. However, the same gyrotron can be used in several other applications that require high-frequency, high-power terahertz radiation. For example, it is known that certain cancer types have characteristic absorptions in the THz regime that can be used to distinguish cancer tissue from non-cancer tissue. Since current detection schemes rely on low-power THz sources only small areas can be scanned at a time. With much higher power levels available from a gyrotron source we envision whole-body scans that are currently not possible due to the lack of THz power. With sufficient power available, such whole-body scans could be performed in seconds. This is comparable to switching on a 500 W light bulb in the dark to inspect a room instead of relying on a small keychain flashlight. .

  This is just one application that we can imagine. In general we are providing the gyrotron sources for customers who require higher output power (several watts to several kW).

  A gyrotron does not need to be a large, bulky piece of equipment. The largest component of the system is the superconducting magnet. In most research labs, gyrotron-based applications have magnets that typically have large fringe fields, which is basically dead-space. Our gyrotron however, are based on actively shielded magnets, with a 5 Gauss line very close to the outer dimension of the cryostat of the magnet. This makes our gyrotrons very compact and easily deployable even in crowded NMR facilities or factory areas.

8. Are there any plans for taking the company public?

  Bridge12 is a young start-up. We are currently developing our first prototypes to demonstrate our vision of compact and cost-effective gyrotron devices. We started the venture with seed funding from private investors, but currently have no plans to take the company public.

9. Which private or governmental organizations do you work with?

  Bridge12 recently received SBIR phase I funding from the U.S. National Institutes of Health for developing a gyrotron device for high-field DNP-enhanced solid-state NMR spectroscopy. Furthermore, we are regularly submitting new research proposals to government agencies for additional funding.

MY COMMENTS: It is so very exciting that such cutting edge technology and thought is being shared with us, here! Thank you again!