MICROSCOPE TAKES IMAGES USING PROTONS

FROM:  LOS ALAMOS NATIONAL LABORATORY 

Taking pictures with protons

U.S., German, Russian collaboration conducts first experiments in Germany

LOS ALAMOS, N.M., June 17, 2014—A new facility for using protons to take microscopic images has been commissioned at the ring accelerator of the GSI Helmholtzzentrum für Schwerionenforschung GmbH (Helmholtz Centre for Heavy Ion Research) in Darmstadt, Germany.

The proton microscope was developed by an international collaboration consisting of Los Alamos National Laboratory, GSI, the Technical University Darmstadt, and the Institute for Theoretical and Experimental Physics, Russia.

Protons, like neutrons, are the building blocks of atomic nuclei. Similar to x-rays, they can be used to radiograph objects, generating images of them. Protons are able to penetrate hot dense matter that can't be examined with light or x-rays. This technology, also known as "proton radiography," was originally invented at Los Alamos National Laboratory in the 1990s, but has been adopted around the world. In the future, the technique will be used at an accelerator currently under construction in Darmstadt called the Facility for Antiproton and Ion Research (FAIR) and at the proposed Matter and Radiation In Extremes (MaRIE) facility at Los Alamos.

In their first experiments, researchers used a proton beam accelerated to an energy of 4.5 gigaelectronvolts (more than 98 percent of the speed of light) by the GSI accelerator facility. A special setup of four quadrupole magnets served as optics to magnify objects with the beam. Initially, they radiographed different items like sets of wires with varying sizes and a wristwatch.

Scientists have succeeded in resolving objects and structures down to a size of 30 micrometers or one thousandth of an inch. The GSI facility, called the Proton Microscope for FAIR, or PRIOR, achieved resolutions comparable to existing facilities in the U.S. or Russia. Scientists plan to improve this to a value of up to 10 micrometers in experiments this year. Another goal is the recording of image sequences of moving objects. In experiments scheduled for July 2014 thin wires will be explosively evaporated by a strong electrical discharge, and this "plasma explosion" will be examined with the proton beam.

The study of plasma is of particular interest to scientists because plasma is found in stars or gas planets like Jupiter. This state of matter can be generated in the laboratory with lasers or strong electrical discharges for short intervals of time. Because protons can penetrate plasmas, they offer unique possibilities to measure the properties of plasma with instruments like PRIOR.

"Combining the experience of this international collaboration has proven to be very productive," said Frank Merrill of the Laboratory's Neutron Science and Technology group and a collaborator on the project. "By joining the enhancements gained from increased proton energy with the gains from proton microscope imaging lenses, a new and remarkable proton radiography capability has been developed."

"Next to the research on events in space, the technique also has very practical applications", said Dmitry Varentsov from GSI's department Plasma Physics and Detectors. "For example one could radiograph running engines or diagnose and treat tumors with it. We want to explore all these opportunities."

The proton microscope will also play an important role at the FAIR accelerator facility. GSI will serve as injector for FAIR. The new FAIR accelerators will provide protons with even higher energies improving the possibilities for experiments. After the completion of FAIR the PRIOR setup will be moved to the new facility. The development of this technique is being extended to the use of electrons and will be utilized for applications at MaRIE.

LARGEST EVER NEUTRON BEAM CREATED AT LOS ALAMOS

FROM LOS ALAMOS NATIONAL LABORATORY

Trident Target caption: Tom Hurry of Plasma Physics adjusts the target positioner and particle beam diagnostics prior to an experiment at Trident.

World Record Neutron Beam at Los Alamos National Laboratory
New Method Has Potential to Advance Materials Measurement
LOS ALAMOS, NEW MEXICO, July 10, 2012— Using a one-of-a-kind laser system at Los Alamos National Laboratory, scientists have created the largest neutron beam ever made by a short-pulse laser, breaking a world record. Neutron beams are usually made with particle accelerators or nuclear reactors and are commonly used in a wide variety of scientific research, particularly in advanced materials science.

Using the TRIDENT laser, a unique and powerful 200 trillion-watt short-pulse laser, scientists from Los Alamos, the Technical University of Darmstadt, Germany, and Sandia National Laboratories focus high-intensity light on an ultra-thin plastic sheet infused with an isotope of hydrogen called deuterium.

The laser light — 200 quintillion watts per square centimeter, equivalent to focusing all of the light coming from the sun to the earth (120,000 terawatts) onto the tip of a pencil — interacts with the plastic sheet, creating a plasma, an electrically charged gas. A quintillion is a one with 18 zeros after it.

The plasma then accelerates large numbers of deuterons — the nucleus of the deuterium atom — into a sealed beryllium target, converting the deuterons into a neutron beam. Using a unique property of plasmas called relativistic transparency, the deuterons are accelerated in just one millimeter rather than the many meters required by standard accelerator technologies.

"So far only at TRIDENT has this new plasma acceleration mechanism been successfully implemented," said Markus Roth from the Technical University of Darmstadt, who serves as the 2012 Rosen Scholar at Los Alamos. "This result is the world’s record for short-pulse laser generated neutron flux, four quintillion neutrons per square centimeter for an object one centimeter from the source. In this generation scheme, the neutrons are emitted along the direction of the initial laser beam and can reach very high energies, in excess of 50 million electron volts."

According to Roth, the new record is five times larger than the previous record and required less than a quarter of the laser energy.

"Neutrons are a unique probe with many scientific applications," said Frank Merrill of LANL’s neutron science and technology group. "Neutrons are used to study fundamental properties of the universe, advanced materials, and have potential applications such as active interrogation of cargo containers, monitoring for clandestine nuclear explosives at border crossings, and as a test bed for fusion-relevant neutron diagnostics, the initial impetus for this study."

This record neutron beam has the speed and energy range that makes it an ideal candidate for radiography and a wide variety of high-energy-density physics studies.

"An object placed one centimeter behind the source would be exposed to more than 40 neutrons per square micrometer (one millionth of a meter) in less than a nanosecond (one billionth of a second) making it an impressive probe for radiography applications," said Merrill.

"Also, for the first time, in these experiments a neutron image driven by a short-pulse laser was realized and showed excellent agreement with numerical calculations," said Roth. Using short-pulse lasers for the production of neutrons can open the field of neutron research to universities, and a broader research community in general.

This project combined the expertise of LANL‘s Los Alamos Neutron Science Center (LANSCE) neutron science group with Physics division’s plasma physicists, TRIDENT laser scientists, and scientists developing neutron detection diagnostics to be fielded at the National Ignition Facility. Scientists from Sandia provided neutron yield and nuclear activation measurements.