John Schmidt

Continued on page 2

PPPL Researchers Study 

Plasma Sterilization

I

TER, a major international magnetic fusion research 

project, tops the list of priorities for the Department 

of Energy’s (DOE’s) Office of Science 20-year science 

facility plan. The project is an international collaboration 

to build a magnetic fusion device capable of producing a self-heated or burning plasma. The fusion power 

produced by ITER will be 10 times greater than the 

external power added to the plasma. The U.S. is one of 

the international partners.

 During a November 10 speech at the National Press 

Club, U.S. Energy Secretary Spencer Abraham outlined 

the plan, a roadmap for future scientific facilities to support the Department’s basic science and research missions. 

The plan prioritizes new, major scientific facilities and 

upgrades to current facilities. Secretary Abraham listed 

28 facilities, which cover the range of science supported 

by the DOE’s Office of Science, including fusion energy, 

materials science, biological and environmental science, 

high energy physics, nuclear physics, and advanced scientific computation.

 “This plan will be the cornerstone for the future of 

critical fields of science in America. These facilities will 

revolutionize science — and society,” said Abraham. 

“With this plan our goal is to keep the United States at 

the scientific forefront.”

 PPPL Director Rob Goldston described the DOE’s 

plan for future facilities as “visionary,” noting that the 

Department is the primary steward for many areas of 

science, in particular, plasma physics and fusion energy 

research, which is conducted at PPPL.

 “The recently completed DOE strategic plan, and 

this 20-year facilities plan, together define an exciting 

future path for the fusion research community to perform 

International Fusion Project Tops List

Continued on page 4

Hundreds of billions of plastic food and beverage containers are manufactured each year in the U.S. 

All of these packages must undergo sterilization, which 

at present is done using high temperatures or chemicals. 

Both of these methods have drawbacks. Chemicals often 

leave a residue that can affect the safety and taste of the 

product, and produce undesirable waste. Heat is effective 

Twenty-Year DOE 

Plan Announced

VOL. 8, NO. 1 • FALL 2003, WINTER 2004
PPPL NEWS • Fall 2003/Winter 2004 Page 2

The PPPL NEWS is issued by the Princeton Plasma Physics Laboratory, a research facility supported by the United 

States Department of Energy and managed by Princeton University. Correspondence and requests to reprint material 

should be directed to: Information Services, Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, NJ 08543; 

telephone 609-243-2750; fax 609-243-2751; e-mail pppl_info@pppl.gov .

PPPL NEWS

Information Services Head: Anthony R. DeMeo

Editor/Writer: Patti Wieser

Photographer: Elle Starkman

Layout and Graphics: Gregory J. Czechowicz 

and Patti Wieser

Continued from page 1

Sterilization

Continued on page 3

and sufficiently rapid, but necessitates the use of costly 

heat-resistant plastics that can withstand sterilization 

temperatures. What if a new method could be found 

that eliminated the need for chemicals or heat-resistant 

plastics?

 Plasma just might be the answer. At PPPL, a team is 

conducting a small-scale research project studying plasma 

sterilization. This method, if successful, could be used 

to sterilize food and beverage containers, leading to an 

enormous savings — potentially hundreds of millions of 

dollars annually for a large soft drink manufacturer.

New Plasma Approach

 “We have experiments indicating it is possible to 

kill microbes using a new plasma approach,” noted John 

Schmidt, lead scientist of PPPL’s Plasma Sterilization 

project. Schmidt cautioned, however, that the research is 

preliminary. “These experiments need to be published, 

peer reviewed, and repeated by other researchers to assure 

reliability. Physics research will be followed by considerable development work to arrive at a practical system for 

assembly line use,” said Schmidt, who has been awarded 

a patent for a plasma sterilization system [see apparatus 

shown in sketch at left]. Working with Schmidt are PPPL 

Technology Transfer Head Lewis Meixler, physicist Doug 

Darrow, engineer Nevell Greenough, and technicians Gary 

D’Amico and Jim Taylor.

The PPPL Experiment

 To get started, PPPL researchers modified old equipment that had once been used to study radio-frequency 

(RF) waves for fusion applications. It consisted of a 

vacuum chamber equipped with an RF source. A metal 

sphere measuring one inch in diameter was mounted at 

the center of the chamber. In preparation for experiments, 

the sphere is removed and sent to a commercial biological 

testing laboratory in Hightstown where a known number 

Above at the plasma sterilization experiment are, from left, Gary D’Amico, 

Nevell Greenough (kneeling and looking into sterilization apparatus) and 

Lewis Meixler. The experiment is on the first floor of the L-wing. Below is a 

sketch of the Plasma Sterilization apparatus. 
Page 3 PPPL NEWS • Fall 2003/Winter 2004

of spores of bacillus subtilis, a non-toxic microbe commonly used as a standard in lab testing, are placed on its 

surface. Following an experiment, the sphere is returned 

to Hightstown where technicians determine the number 

of spores killed in the process.

 Fusion experiments at PPPL have generated plasmas 

with temperatures in the hundreds of millions of degrees 

centigrade. For killing spores, the PPPL researchers start 

with “low-temperature” hydrogen plasmas in the range of 

50,000 degrees centigrade. At that temperature, the hydrogen ions are moving much too slowly to kill spores quickly. 

Rapidly pulsing a 50-kilovolt potential between the sphere 

and the vacuum chamber solves the problem. The sphere 

is charged negatively and the vessel is at ground. Under 

these circumstances, the positively charged hydrogen ions 

accelerate toward the sphere in pulses energetic enough 

for the ions to pierce the hard outer shell and soft inner 

core of the spore. Recent experiments employed 4,000 

10-microsecond pulses, which reduced the population of 

live spores by a factor of 100-1000 — the kill ratio.

In the Real World

 In the real world, equipment and processes suitable for 

the assembly line of a packaging plant would be needed. 

In such a situation, sterilization time is precious. RF 

generates a low-temperature hydrogen plasma inside 

the evacuated container, which is held in place by a 

surrounding conducting shell. An electrode is inserted 

into the container. The plasma is then subjected to a 

pulsed differential of 50 kilovolts, with the electrode 

pulsed positively and the conducting shell grounded. 

This causes energetic pulses of hydrogen ions to accelerate away from the electrode toward the conducting 

shell. On the way, they collide with spores present on 

the inner surface of the container. The hydrogen ions are 

energetic enough to penetrate the durable proteinaceous 

outer cover of the spores.

 “These high-energy hydrogen ions stop very quickly 

and consequently deposit all their energy over a very 

small distance, a few microns, which, as it turns out, is 

the size of the spores. So relatively modest currents of 

energetic hydrogen ions can do a large amount of damage inside the spores by messing up their DNA,” said 

Schmidt. He estimates that a sufficient kill ratio could 

be attained by 10-microsecond pulses every millisecond 

for a few seconds. Further experimentation is needed to 

confirm the number of 10-microsecond pulses necessary 

to reach the required kill ratio. A few seconds’ processing time per container would make the system feasible 

for the assembly line.

 The effectiveness of the hydrogen ions can be compared with that of gamma rays or X-rays used to sterilize 

bulk materials. Gamma and X-rays have long penetration 

depths, so they don’t do as much damage per unit length 

as the hydrogen ions. “Textbooks contain the radiation 

damage coefficients that are required to kill the relevant 

microbes. I am confident that we will be able to attain 

these,” said Schmidt.

 A small business has been started to do the development work leading to a potential commercial application.

●

Shown is a scanning electron microscope image of a small group of bacillus 

subtilis var Niger spores magnified approximately 13,500 times. The image 

shows that the spores are approximately 1 μM long and approximately 

0.5 μm in diameter.

Shown is an example of the spores used in the plasma sterilization experiment. The image, made by a scanning electron microscope, is of bacillus 

subtilis var Niger spores magnified approximately 1,700 times. It illustrates 

the typical spore density on the surface of the brass sphere that is inserted 

into the sterilization apparatus, and shows that the spores are fairly evenly 

distributed over the surface to be sterilized. 

— By Anthony DeMeo
PPPL NEWS • Fall 2003/Winter 2004 Page 4

Plan

Continued from page 1

the scientific research needed to bring a new, clean, and 

abundant energy source to humankind,” said Goldston.

 Negotiations are ongoing for the location of ITER, 

which will be either in France or Japan. PPPL is among 

the contenders to host the U.S. ITER Home Office.

 The Office of Science priority list for new facilities 

will help the Department plan its potential future scientific 

investments. Twelve facilities are identified as near-term 

priorities. Behind the first priority (ITER) is an UltraScale 

Scientific Computing Capability that would increase by 

a factor of 100 the computing capability available to 

support open scientific research. It would be located at 

multiple sites. The plan further identifies eight facilities 

as midterm priorities and eight as far-term priorities.

 DOE’s Office of Science prepared the list over the 

last year with input from the scientific community, DOE 

laboratories, and advisory committees.

 A document describing all 28 facilities and the prioritization process, Facilities for the Future of Science: A 

Twenty-Year Outlook, is available at www.sc.doe.gov

DOE's Orbach Attends PPPL On-site Review

I

n September, Department of Energy Office of Science Director Ray Orbach 

attended the PPPL On-site Review, which focused on the Laboratory’s vision 

for the next decade. This vision encompasses the National Compact Stellarator 

Experiment completing construction and coming into operation at PPPL in 2007; 

the National Spherical Torus Experiment completing its mission 

by this time, with the Lab possibly moving on to a Next Step 

Spherical Torus in the former 

Tokamak Fusion Test Reactor 

Test Cell; and the construction 

in the next few years of a West 

Wing Addition to the Lyman 

Spitzer Building. The addition 

would be proposed to house both 

the U.S. ITER Project Office and 

a joint PPPL-Geophysical Fluid 

Dynamics Laboratory-Princeton 

University computer center.

Facing the camera, from left, 

are Orbach, Toni Joseph, Director, Office of Laboratory Policy 

for the DOE Office of Science, 

and PPPL Director Rob Goldston 

(standing). At far right with his 

back to the camera is PPPL Chief 

Scientist Bill Tang. ●

Anderson Chairs 

National Council

PPPL’s Jack Anderson is the new Chair of the 

Department of Energy’s 

(DOE’s) National Laboratories Improvement Council. 

Anderson, head of PPPL’s 

ES&H and Infrastructure 

Support Department, assumed the one-year post 

during the summer.

 The Council’s goal is to 

hold meetings regularly for 

members to address com- Jack Anderson

mon issues and share lessons learned, as well as to act 

on opportunities for improvement in administration and 

operations.

 The Council includes senior representatives from 

DOE laboratories and programs. ●
Page 5 PPPL NEWS • Fall 2003/Winter 2004

PPPL — On Course with Top Crew

Director Goldston Delivers State-of-the-Lab Address

Dressed in a Hawaiian shirt and surrounded by staff and friends wearing leis, PPPL Director Rob Goldston 

delivered his annual State-of-the-Lab talk on November 

24. His message to the overflow crowd in the Melvin B. 

Gottlieb Auditorium: PPPL has a “top crew” and is “on 

course.”

 “We have great people, an exciting program, and 

remarkable prospects,” said Goldston.

 Under the “great people” category, the Director talked 

about the Lab’s “top crew,” safety on the job, and risk 

management. While giving details about the Lab’s “exciting program,” he discussed the National Spherical Torus 

Experiment, National Compact Stellarator Experiment, 

Off-site Research, Plasma Science and Technology, and 

Theory. Under “remarkable prospects,” Goldston focused 

on the community fusion development path, as well as 

the support of Congress and the U.S. Administration for 

fusion. He also discussed the possibility of locating the 

PPPL Director Rob Goldston (large photo) delivers the State-of-the-Lab talk. At top left are (from left), Steve Sabbagh, Adriana Popescu, and 

Charles Skinner in the Lobby; at top right (from left) are John Schmidt, Greg Schmidt, and Rich Hawryluk, and at bottom right is Alex Ilic.

The U.S. Department of Energy’s (DOE’s) National Laboratories house world-class facilities where more than 30,000 

scientists and engineers perform cutting-edge research 

spanning DOE’s science, energy, national security, and 

environmental quality missions. Interested in the latest 

achievements of the National Laboratories? Then visit the 

DOE Pulse at: http://www.ornl.gov/news/pulse/.

U.S. ITER Project Office at PPPL and of building the 

West Wing addition to the Lyman Spitzer Building.

 The event had an island theme and concluded with the 

presentation of awards in the Auditorium and a reception 

in the Lobby. ●
PPPL NEWS • Fall 2003/Winter 2004 Page 6

Successful Liquid Lithium 

Experiments Continue on CDX-U

Potential for Fusion Reactors Looks Promising

At left at CDX-U are members of the team. From left are Project Co-heads Bob Kaita and Dick Majeski, PPPL engineer John Timberlake, Princeton 

University graduate student Jef Spaleta (kneeling), PPPL technician James Taylor (back in hat), Drexel University student Douglas Rodgers, and 

Princeton University graduate student Timothy Gray. At right, the pool of liquid lithium is shown in the toroidal tray that encircles the bottom 

of the CDX-U vacuum vessel. The tip of the liquid-lithium injector, which is removed before plasma operations, is reflected on the shiny surface 

of the liquid lithium.

Recent experiments on PPPL’s Current Drive Experiment-Upgrade (CDX-U) have demonstrated the effectiveness of liquid-lithium limiters for plasma particle 

and impurity control. Results are a key step toward the 

use of free-flowing liquid-lithium walls in a fusion power 

plant, according to Bob Kaita, who co-heads the project 

with Dick Majeski.

 In May, PPPL staff and their collaborators at the 

University of California-San Diego (UCSD) achieved 

a near complete fill of CDX-U’s toroidal-tray limiter by 

injecting liquid lithium onto the two halves of the tray 

under an argon atmosphere.

 “All of the elements were brought together successfully. This is not trivial, because we needed to prepare 

the tray surface correctly and prepare the injectors so the 

lithium would remain liquefied and flowing. If the surface of the tray is not clean enough, and not at the right 

temperature, the lithium will bead up,” noted Kaita. The 

argon atmosphere acts as a buffer to prevent the lithium 

from evaporating rapidly and coating surfaces inside the 

vacuum vessel. Plasma discharges were initiated within 

hours after the tray was filled.

 Limiters are metal surfaces that are specially designed 

to protrude from the vacuum vessel wall toward the edge of 

the plasma. Their job is to prevent the plasma from striking 

the vacuum chamber and sputtering impurities, especially 

heavy metals, into the plasma. Metal atoms soak up energy 

and radiate it away, causing the plasma temperature to drop. 

Plasma particles (deuterium ions) striking the limiter plates 

are neutralized and return to the plasma where they again 

become ionized. This process, called “recycling,” tends to 

cool the plasma edge, and it limits the ability to achieve 

beneficial plasma confinement modes that require a hot 

plasma edge. Liquid lithium may be the solution because 

of its capability for absorbing plasma particles, thereby 

reducing recycling.
Page 7 PPPL NEWS • Fall 2003/Winter 2004

 Initial experiments on CDX-U in FY00-01 employed a 

rail limiter consisting of a cylindrical stainless-steel mesh 

soaked with liquid lithium. Only 20 cm2 of the lithium was 

actually in contact with the plasma. With the toroidal-tray 

limiter, a 360-degree annular metal belt running below 

the entire plasma, the area of interaction increases to as 

much as 1900 cm.2 

New Results Are Dramatic

 Following pump down in any magnetic fusion device, 

it is necessary to run a series of conditioning plasma 

shots, until all of the loosely bound water, oxygen, and 

carbon in the vacuum vessel walls is removed from the 

chamber. These materials pollute the plasma, preventing 

the required energy confinement time needed for experiments. In CDX-U, plasma currents are limited to 20 or 30 

kA, until vessel surfaces are cleaned. This can take up to 

a day of conditioning. However, when CDX-U plasmas 

are started in the presence of lithium, full plasma currents 

of 70 to 80 kA can be produced after only a few shots 

— a dramatic demonstration of the ability of lithium to 

absorb impurities.

 Physicists are never satisfied unless they can measure things, and the CDX-U team is no exception. “It’s 

difficult to quantify these (edge) effects. However, we 

do have an optical diagnostic that can look for oxygen 

emission lines typically found at the plasma edge. This 

spectrometer looks directly at the tray through a port in 

the vacuum chamber. With no lithium, oxygen emission 

lines are quite measurable. With lithium in the tray, the 

measurable level of oxygen goes to zero — a dramatic 

effect,” said Kaita.

 Experiments such as Princeton’s Tokamak Fusion Test 

Reactor (TFTR) and the DIII-D at General Atomics, Inc., 

have demonstrated that even modest recycling reductions 

can significantly improve plasma performance. These results, and recent experiments with liquid lithium at PPPL, 

UCSD, and other laboratories, suggest it is time to assemble 

an experiment in which the entire plasma is surrounded 

with liquid lithium. Consequently, the CDX-U folks have 

submitted a proposal for the reincarnation of CDX-U as 

the Lithium Tokamak Experiment (LTX) in FY06.

 The LTX would incorporate a shell, just inside the 

vacuum chamber walls, onto which a thin layer of liquid 

lithium, about 1000 Angstroms, would be coated evaporatively. The shell would be maintained at a temperature 

that would keep the lithium in the liquid state. The coating will be sufficiently thick to absorb and retain plasma 

particles, preventing recycling, and trapping impurities 

so that they do not re-enter the plasma from the vacuum 

vessel walls.

 “The idea is to put in a fresh coating of lithium after 

each shot. Conceptually the process is similar to the gettering done between shots on earlier tokamaks, where 

titanium was sublimated onto vacuum vessel components 

to reduce impurities. The difference is that we would 

make a thin liquid coating instead of a solid one,” Kaita 

said. He envisions that such a system is an important step 

toward a fast flowing, thin liquid-lithium wall in a fusion 

reactor.

 In parallel with the proposed operation of LTX will 

be a series of prototype studies on the National Spherical 

Torus Experiment (NSTX) beginning in FY04. The first 

experiments will involve a small area coated with liquid 

lithium. The longer-term goal for NSTX would be the 

design, installation, and operation of a flowing liquidlithium divertor in FY08. In FY05-06, CDX-U would be 

used for preliminary tests of lithium coating technology 

in preparation for its conversion to LTX.

 Divertor coils, located inside the vacuum chamber, 

modify the magnetic field at the plasma edge to divert 

plasma particles and impurities to a region within the 

vacuum chamber, where they collide with a specially 

coated surface, are absorbed, and are prevented from entering the plasma. Divertors eliminate the need for limiters, 

greatly reducing recycling, resulting in a hotter plasma 

edge and better confinement. Kaita asked, “If divertors 

are more effective than limiters for particle control, why 

not go ahead and use lithium-coated surfaces in them as 

well?” The divertor envisaged for NSTX would employ 

a static thin film of liquid lithium first, and then a flowing 

lithium system.

 The jury is still out on the role of divertors and/or 

limiters in a commercial fusion reactor. This depends on 

the practicality and effectiveness of the flowing liquidlithium wall in controlling recycling and impurities. If 

successful, can such a wall also be used to remove the 

excess tritium that gets embedded in a fusion reactor 

wall? 

 Deuterium and tritium, both isotopes of hydrogen, will 

be used as fuel in a fusion power plant. During its operation, a substantial quantity of tritium, which is radioactive, 

can accumulate in the power plant walls. Depending on 

how long the tritium is retained in the lithium, a flowing 

liquid-lithium wall could avoid this by moving the tritium 

out of the vacuum vessel — a major advantage over solid 

reactor walls.

 With the exciting, innovative liquid-lithium experiments planned for the next several years on CDX-U, NSTX 

and LTX, Princeton is positioned to make vital contributions to technological developments that are essential for 

practical fusion power in the 21st Century. ●
Page 8 PPPL NEWS • Fall 2003/Winter 2004

Awards • Awards • Awards • Awards

Nathaniel Fisch, PPPL Associate Director for Academic 

Affairs, recently received the outstanding Mentor award 

from the DOE Office of Science. The plaque, signed by 

Energy Secretary Spencer Abraham, recognizes Fisch 

for his “dedication as a mentor and for his willingness to 

share knowledge and to inspire and instill solutions, and 

immersing inquisitive minds in the world of science.” The 

award, issued this year, honors Fisch for his mentoring 

efforts in 2002.

In November, PPPL and Princeton University officials presented the PPPL Distinguished Engineering Fellow Award to Arthur Brooks and the Kaul Prize for Excellence in Plasma Physics Research and Technology Development to Masaaki Yamada 

and Hantao Ji. From left are Princeton University’s Will Happer with PPPL’s 

Masaaki Yamada, Hantao Ji, Art Brooks, and PPPL Director Rob Goldston.

PPPL physicists Robert Kaita (above, left) and Neil 

Pomphrey (above, right), were elected Fellows of the 

American Physical Society in October. Kaita and Pomphrey received the lifetime appointments in recognition 

of their contributions to the field of plasma physics.

PPPL’s Marc Cohen recently received the Outstanding 

Co-operative Education Partner Award from the Drexel 

University Alumni Association. Cohen was recognized 

for being an outstanding student in his role as a co-op. He 

was a Drexel University co-op student at PPPL last year 

and now is a Help Desk technician at PPPL.

In October, PPPL physicist Dennis Mueller received 

the MacMurray College “Distinguished Career Award 

2003” from the college’s Alumni Association. The award 

recognizes Mueller for the impact he has made scientifically, academically, and professionally since he received 

a bachelor’s degree in physics from MacMurray in 1968. 

The college is in Jacksonville, Ill.

PPPL’s Alex Nagy, coordinator of the Scientist-in-theClassroom Program at General Atomics (GA) in San 

Diego, recently received a “Community Science Educator 

of the Year” award for 2003 from the San Diego Science 

Education Association. The association specifically honored Nagy, who is on long-term assignment at GA, for his 

high-quality presentations on plasma science to students 

in classrooms throughout San Diego County. 

PPPL honored its inventors in June at the twenty-first 

annual Patent Awareness Program Recognition Dinner 

at Princeton University’s Prospect House. The event honored 

those who received patents and 

disclosed inventions during Fiscal Year 2002. Those recognized 

include George Ascione, Jun 

Gyo Bak, Manfred L. Bitter, 

Andrew Carpe, Lloyd Ciebiera, John D. Desandro, Ilya 

Y. Dodin, Philip Efthimion, 

Eliot Feibush, Nathaniel J. 

Fisch, Charles A. Gentile, 

Geoff Gettelfinger, Kenneth 

W. Hill, Stephen C. Jardin, 

Scott Klasky, Stephen Langish, 

Sang Gon Lee, Dennis Mansfield, Michael Miller, Hideo 

Okuda, John Parker, Robert 

F. Parsells, Erik Perry, Steve 

Raftopoulos, Yevgeny Raitses, 

Keith Rule, Gennady Shvets, 

John Schmidt, Charles H. 

Skinner, David Staack, Brentley Stratton, Robert Woolley, 

and Irving Zatz.