David Nygren’s powerful particle-detection instruments are enabling breakthrough discoveries in physics and have improved practical applications such as medical imaging. Nygren developed the time projection chamber (TPC) to identify and track charged particles in complex high-energy collisions. Incorporating an intrinsically three-dimensional capability, the TPC has been implemented in particle colliders at major national research laboratories, has provided evidence of the gluon plasma state, and is playing a key role in searching for weakly interacting massive particles, in learning more about the elusive neutrino, and for many other applications. His proposal for fully depleted charge-coupled device imagers for optical astronomy are enabling a deeper view into space. Nygren’s quantum-counting mammography system enables improved image quality while greatly reducing radiation exposure.
An IEEE member, Nygren is a Presidential Distinguished Professor of Physics at the University of Texas at Arlington in Arlington, TX, USA
Chandrashekhar Joshi is overcoming the challenges of providing smaller, more cost-effective versions of arguably the most important instrument of scientific discovery—the high-energy particle accelerator. Acknowledged as the undisputed leader in the drive to make plasma accelerators a reality, Joshi has demonstrated that charged particles can be accelerated thousands of times more rapidly using plasma compared to traditional radio-frequency-wave technology. To reduce the massive size of current machines, Joshi uses powerful laser pulses or charged particle bunches to create charged-density waves in ionized gas. The results achieved by Joshi’s plasma accelerator group have led to major national experimental facilities working toward building terra-volt-scale plasma-based particle colliders needed at the frontier of particle physics while reducing their cost.
An IEEE Fellow, Joshi is a Distinguished Chancellor’s Professor of Electrical Engineering at the University of California, Los Angeles (UCLA), Los Angeles, CA, USA
Simon R. Cherry’s expertise in developing molecular imaging systems incorporating positron emission tomography (PET) is driving advances in biomedicine and healthcare. Cherry created the first microPET scanner to evaluate radiopharmaceuticals and drugs in small animals. Overcoming the challenges of imaging small animals has been instrumental in allowing researchers and clinicians to gain a better understanding of diseases and potential human therapies. He also developed the first hybrid PET/magnetic resonance imaging (MRI) scanners for even more powerful preclinical imaging applications. His discovery that many radionuclides used in biomedical research produce Cerenkov luminescence and can be imaged using optical cameras has created one of the fastest-growing areas in molecular imaging. Cherry is currently working on developing the first total-body human PET scanner.
An IEEE Fellow, Cherry is a professor with the Departments of Biomedical Engineering and Radiology at the University of California, Davis, CA, USA.
For over 40 years, Noah Hershkowitz’s research has broadened the understanding of the fundamental properties of plasma. His work has covered a wide range of plasma phenomena including low-temperature plasmas, semiconductor fabricating plasmas, fusion plasmas, and space plasmas. His groundbreaking contributions to understanding solitons, sheaths, and presheaths have impacted semiconductor etching, as the plasma sheath plays a major role in the linear acceleration of ions that results in the small features of modern microelectronic circuits. His pioneering work on emissive probes resulted in the development of a new technique for determining plasma potential by analyzing emissive probe emitted current. In 2002 he was the first to measure plasma potential throughout the presheath and sheath at a boundary in a weakly collisional plasma. He has supervised 56 Ph.D.'s.
An IEEE Life Fellow, Dr. Hershkowitz is the Irving Languir Professor Emeritus at the University of Wisconsin, Madison, WI, USA.
The collective work of H. Malcolm Hudson, Brian F. Hutton, and Lawrence A. Shepp and their collaborators has resulted in reconstruction algorithms that propelled the success of emission tomography as a clinically feasible method for medical imaging. Dr. Shepp developed the maximum-likelihood expectation-maximization (ML-EM) algorithm (published in 1982 by Shepp and Y. Vardi), which provided improved image quality compared to the Fourier-based algorithms of the time. However, its heavy computational burden was a barrier to clinical use. Profs. Hudson and Hutton were motivated to overcome the computational workload with faster image reconstruction solutions. This led to the development of the ordered-subsets expectation-maximization (OS-EM) algorithm (published as an abstract in 1992 by Hudson, Hutton, and R.S. Larkin, and as a paper in 1994 by Hudson and Larkin), which applied the ML-EM algorithm successively to well-chosen data blocks. This was key to bringing ML estimation into daily practice for emission tomography. The combined work paved the way for techniques that improve image accuracy and precision, while potentially shortening scan duration or helping to reduce the activity of tracer administered to the patient.
Dr. Hudson is an Emeritus Professor with the Department of Statistics at Macquarie University, New South Wales, Australia. An IEEE Senior sember, Dr. Hutton is Professor of Medical Physics in Nuclear Medicine and Molecular Imaging Science at the Institute of Nuclear Medicine at the University College London, U.K. and a Professor in the Department of Medical Radiation Physics at the University of Wollongong, NSW, Australia. Dr. Shepp, who passed away in April of 2013, was the Patrick T. Harker Professor of Statistics at the Wharton School of the University of Pennsylvania, Philadelphia, PA, USA, and a Professor with the Department of Statistics at Rutgers University, Piscataway, NJ, USA
Veljko Radeka has shaped the field of radiation measurement for over 50 years with innovative detector technology that has benefited applications ranging from nuclear science to medical instrumentation. His cutting-edge detector instrumentation pushes the limits of radiation detection and has opened the path to new discoveries in many scientific disciplines. Dr. Radeka developed circuits to detect extremely rare radiation signals from background radiation for solar neutrino experiments. This work helped Ray Davis win the 1972 Nobel Prize in Physics and changed the foundations of particle physics. Dr. Radeka has also enabled new methods of real-time imaging for determining composition of chemical elements. He is collaborating on the development of an advanced ground-based telescope for investigating dark matter/energy in the universe. And his research group has developed a medical scanner that combines positron emission tomography and nuclear magnetic resonance imaging in one instrument.
An IEEE Life Fellow, Dr. Radeka has been division head for 40 years and is presently a senior scientist with Brookhaven National Laboratory, Upton, NY, USA.
Considered one of the world’s leading researchers on pulsed power, vacuum, and gas discharges, Gennady Mesyats’ pioneering work in Russia helped establish nanosecond pulsed power technology as a new engineering discipline. His contributions began in 1957 when he constructed a nanosecond rise-time high-voltage pulse generator. Dr. Mesyats discovered the phenomenon of explosive electron emission (EEE) in 1967. Important in explaining and predicting current switching in a vacuum discharge, this phenomenon makes it possible to produce pulsed electron currents of almost infinite magnitude. His research group then developed the first high-current nanosecond pulsed electron accelerator using an EEE diode. Dr. Mesyats’ work on volumetric gas discharges led to new types of high-power pulsed gas lasers. Dr. Mesyats also discovered the phenomenon of current cut-off in semiconductor switches at high current densities within nanoseconds. This enabled fully solid-state nanosecond pulse generators that could produce pulsed voltages in the megavolt range at a high repetition rate.
Dr. Mesyats is currently the director of the Lebedev Physics Institute within the Russian Academy of Sciences, Moscow and serves as the Academy’s vice president
Charles K. (Ned) Birdsall’s discoveries have built the foundations of plasma science. His lifelong dedication to plasma physics began during the 1950s with work on resistive-wall amplification. He showed that electron streams could be amplified by the presence of a resistive wall and proved the existence of negative energy waves. He pioneered the concept of coupling between positive and negative energy waves. Dr. Birdsall’s ring-bar travelling wave tube (TWT), a high-power amplifying device, is still in use today for broadband military communications. During the 1960s he discovered virtual cathode oscillations, the most important theoretical development in diode physics. He is best known for establishing particle-in-cell simulation, which provides first principle solutions of a wide range of plasma phenomena. Dr. Birdsall’s free dissemination of plasma simulation codes has facilitated thousands of engineers in conducting research. An IEEE Life Fellow, Dr. Birdsall is Professor Emeritus in the Electrical Engineering and Computer Science Department at the University of California, Berkeley.