the search for cosmic transients

U . S . D E P A R T M E N T O F E N E R G Y

U N I V E R S I T Y O F C A L I F O R N I A

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A M O N T H L Y P U B L I C A T I O N O F LOS ALAMOS NATIONAL LABORATORY

THE SEARCHFOR COSMICTRANSIENTS

SEE PAGE 2

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A M O N T H L Y P U B L I C A T I O N O F 2 LOS ALAMOS NATIONAL LABORATORY

EDITORMeredith Coonley

SENIOR SCIENCE WRITERTodd Hanson

EDITORIAL COORDINATORJudith Goldie

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CONTRIBUTING EDITORJohn A. Webster

CONTRIBUTING ILLUSTRATOREdwin Vigil

CONTRIBUTING PHOTOGRAPHERJohn Bass

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T here is something almost mystical about winter nights in northern New Mexico. The cold, clear skies seem to let the stars

shine brighter, the snow-laden land and trees make the world a muchquieter place. During this season, as we hurry through the chillednights that carry us toward the next millennium, some of us may stop and gaze upward to ponder the beguiling constancy of theuniverse. Yet even then, in the cold and the dark, as we consider theuniverse to be permanent and unchanging, nothing could be furtherfrom the truth. Scattered amid the stars that have kept their places inour skies for millions of years are the astrophysical phenomenascientists call cosmic transients — short-duration, one-timeastrophysical events lasting anywhere from less than a second to aslong as a few years. They include such diverse phenomena asquasars, comets, asteroids and supernovae. These heavenly eventsoften come and go completely unseen, but leave behind a changedand changing universe. As part of the Lab’s high-energy and spacescience programs, Los Alamos researchers have studied cosmictransients for decades. Today, this work is the focus of research at theLaboratory’s Fenton Hill Observatory.

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Cosmic transients exist in numerous forms. Some of the most activeknown transients are galactic nuclei and quasars. These mysteriousphenomena are observable for periods lasting anywhere from seconds toyears and emit massive amounts of radiation at nearly every wavelengthof the electromagnetic spectrum. This wide range of radiation meansscientists can study them using a number of different types of instru-ments — from optical and radio telescopes to gamma ray detectors.

Supernovae, the sudden,unpredictable explosions ofstars that produce inseconds as much energy asour sun will release in itslifetime, are often onlyvisible for a short time andare best discovered througha program of continuoussky monitoring. Othervisitors to our region ofspace, such as comets andasteroids, are somewhatbetter known transients

of great interest to science. Thetelescopes and instruments at FentonHill Observatory are used to studymany types of cosmic transients.

Once home to the Department ofEnergy’s innovative Hot Dry RockProject, Fenton Hill is located 35 mileswest of the Laboratory in the pine-forested Jemez Mountains of northernNew Mexico. The Fenton HillObservatory, which sits at an elevationof 8,680 feet and is without a direct

line of sight to any city lights, has several unique telescopes.

The largest and perhaps the best-known telescope at Fenton Hill isMilagro. Not a typical telescope, Milagro is actually a gamma raydetector constructed of more than 700 light-sensitive photomultiplierdevices submerged in a six-million-gallon pool of highly purified water.

Milagro detects bursts of cosmic gamma rays by the tiny flashes of blueCherenkov light that occur when the high-energy particles strike andinteract with the water. Acting somewhat like a camera whose shutter isalways open, Milagro stares continuously at the sky, day and night, from

ÕSc ient istsnav igate theMi lagro pool atFenton Hi l lObservatory ina raft to checkand repairphotomult ip l iertubes.

ÕThe

photomult ip l iertubes f loat

tethered to aframework of

PVC tubingvis ib le in the

depths.

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horizon to horizon, waiting for the high-energy particles produced bygamma ray bursts that continually bombard our planet from outer space.

Last year, during one of the nearly 50 gamma ray bursts detected byMilagrito, Milagro’s prototype predecessor at Fenton Hill, a cone-shapedshower of particles appeared from the direction of a gamma ray burst.This discovery was seen by many researchers as a step toward provingthe existence of what astrophysicists refer to as TeV, or trillion electronvolt, radiation. This was the most energetic radiation ever recorded froma gamma ray burst, and Milagro will no doubt record more such burstsin the coming years.

Discoveries like this, along with the original find of cosmic gamma raybursts by Los Alamos scientists in the 1960s, has the international scien-tific community turning to Los Alamos for leadership in this area oftransient research.

Like Milagro, ROTSE-I, the Robotic Optical Transient SearchExperiment, is crucial in the continuing quest to broaden science’soverall understanding of gamma ray bursts.

In January 1999 the visible light component of a gamma ray burst fromspace was observed by ROTSE-I coming from a galaxy nine billion lightyears away in a part of the sky near the constellation Corona Borealis.

Awakened by a detection signal provided byNASA’s Compton Gamma Ray Observatory,ROTSE-I responded in less than 22 seconds tocapture the visible light from the burst while thegamma rays were still arriving on Earth. This wasthe first time in history that such an observationhad ever been made.

Before that, the optical counterparts of gamma raybursts had only been caught as the faint, fadingafterglow of the event. At its peak, the brightnessof the object now known as GRB 990123 was anestimated six million times brighter than a typical

supernova with an estimated energy release almost 10 million billiontimes that of our sun.

This ROTSE-I observation represents the most luminous optical objectever detected in the universe. If you had been gazing at that spot withbinoculars, you would have seen a ‘star’ appear suddenly, brighten andthen fade away within minutes — a true transient event.

ROTSE-I has four wide-field 200 millimeter lenses mounted onelectronic cameras that can respond automatically to a transient eventsignal. The four-inch-diameter lenses are each connected to charge-


History wasmade in

January 1999when ROTSE- Icaptured th isimage of the

opt ica lcounterpart of

gamma rayburst

GRB990123.

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coupled imaging devices — basically the same technology found indigital cameras on the consumer market. The four lenses, strapped to asingle mount, point to slightly different, but overlapping, sections of thesky and together they capture 250square degrees of the sky at once. Thatfield is about what would be covered bya dinner plate held out at arm’s length.

In addition to responding to transientevents, ROTSE-I automatically scans thesky each night from horizon to horizon,taking a series of digital snapshots thatjointly cover the entire visible night sky.In clear weather ROTSE can compile acomplete photographic record of the skytwice each night.

Presently located at the Los Alamos Neutron Science Center, ROTSE-Isoon will be relocated to become a part of the Fenton Hill Observatory.A second ROTSE device currently is being debugged. Located alongsideROTSE-I, ROTSE-II uses a set of twin 0.45-meter aperture telescopesthat will be operated in stereo mode to perform similar sky-watchingfunctions. The next-generation ROTSE telescope is being built. It willhave characteristics similar to the ROTSE-II instrument, but is beingdesigned so it can be easily replicated and shipped to distant locations.

After the Laboratory receives and debugs the first of these units,probably in the summer of 2000, the ROTSE team will order six to eightmore of them to be stationed at various sites around the world to givemore complete coverage of the sky. The ROTSE team has already begunnegotiations for locating the telescopes at sites in Australia, the CanaryIslands and Israel. ROTSE telescopes are operated through a collabora-tion of astrophysicists from Los Alamos and Lawrence Livermorenational laboratories and the University of Michigan.

REACT, Research and Education Automatically Controlled Telescope, is arobotic telescope with a one-half-degree field of view. When running inevent alert mode, REACT will automatically respond to a signal byswinging around to take a series of one-minute, high-resolution photosthat might capture any optical signals that coincide with gamma raytransients detected by other sky-watching instruments. REACT, however,will soon have another important use as an educational outreach tool.

If plans go as expected, REACT could someday provide northern NewMexico middle- and high-school-level teachers and students the oppor-tunity to strengthen their knowledge of fundamental astronomy andbuild skills in collecting science information. With Laboratory and

ÕThe fast-movingcameras onROTSE- I arecapable ofreact ing totrans ienta lerts inseconds.

university researchers acting as subject-matter experts, students will usethe Internet to remotely control the REACT telescope for scientificresearch. REACT will allow teachers and students to participate in avariety of science experiences that permit hands-on discovery such asthe search for undiscovered asteroids and other Near Earth Objects.

The future of Fenton HillObservatory for astronomicaltransient research continues toshine. The Radio InterferometerTransient Experiment, or RITE, willeventually place 16 to 20 surplussatellite television dishes at FentonHill. These stationary dishes will beaimed at the heavens and use therotation of Earth to repeatedlymonitor a narrow region of the sky.

By combining the radio wave signalsreceived from all the dishes, an

image of radio sources coming from space will be created. Comparingeach day’s image with the previous day’s image will allow the detectionof transient radio sources. Private citizens are donating the satellite dishantennas, making this an extremely low-cost scientific research project.

Funding for work at Fenton Hill Observatory comes from a variety ofsources, including NASA, the National Science Foundation and severalmajor universities. Los Alamos Laboratory-Directed Research andDevelopment funds and the University of California’s Institute for Nuclearand Particle Astrophysics and Cosmology have also provided support.

As the facilities and capabilities ofFenton Hill Observatory grow in theyears to come, so too will our knowl-edge of cosmic transients. In themeantime, the instruments andtelescopes at Fenton Hill will bewaiting and watching to capturethose celestial events that eyes mightotherwise miss.

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ÕA Laboratory

studentemployee

makesadjustments to

the REACTte lescope.

Two of thesevera l smal lte lescopeslocated atFenton Hi l l . Thedome on theleft houses theREACTte lescope.

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SHIFTING THE THEORYOF PLATE TECTONICS

OR: DIAMONDS AREN’T ALWAYS

A GEOPHYSICIST’S BEST FRIEND

You won’t find these diamonds adorning a piece of jewelry. They’re too tiny — ranging in size from a

mere micron (0.000039 of an inch) to 100 microns —and can’t be seen with the naked eye. But researchersfrom Los Alamos and the University of California atRiverside have studied them and come up with evidencethat could force a revision of the theory of platetectonics, which explains how continents were formed.

Known as microdiamonds, the tinygems first were discovered — albeit invery small quantities — in the mid-1970s by Anton Zayachkovsky, chiefof geology for the KokchetavGeological Survey, within crustalmetamorphic rocks in an area ofnorthern Kazakhstan calledKokchetav Massif.

However, because most geophysiciststhought at that time that diamondscould not form in these types of rocks,they disputed and ultimatelydismissed the discovery.

Years later, another team of geophysicists not only confirmed theoriginal finding, but discovered that the microdiamonds werequite abundant. Now microdiamonds also have been discoveredwhere plates collide in Norway, China and Germany.

The problem is, based on geophysicists’ current understanding ofplate tectonics, these microdiamonds aren’t supposed to be there.

The theory of plate tectonics states that Earth’s outer shell, thelithosphere, consists of about a dozen large plates and severalsmaller ones that move relative to each other and either diverge,converge or slip past each other. These interactions explain the


ÓAn imperfectcube-octahedra ld iamond crysta lfrom theKokchetavMass i f inKazakhstanmagnif ied2,859 t imes.The natura l s izeof the crysta l i sabout 28microns.ResearcherLar issaDobrzhinetskayatook the imagewith a scanningelectronmicroscope atthe Univers i tyof Ca l i fornia atR ivers ide.

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present-day positions of Earth’s continents, as well as the forma-tion of mountains and volcanoes.

Until recently, geophysicists thought that diamonds coulddevelop only in Earth’s mantle at depths of 60 to 186 miles ordeeper, where pressures and temperatures are high enough tostabilize carbon into the ultracompact crystalline structure of adiamond. The diamonds reach Earth’s surface when volcaniceruptions force them through the mantle and crust up narrowconduits called kimberlitic pipes.

However, microdiamonds were discovered within ultrahigh-pressure, sedimentary crustal rocks in the continental collisionzones. Crustal rock is considered too buoyant, or light, to beforced under the mantle during a continental plate collision. It isinstead the heavier mantle rock that is subducted under themantle during these collisions.

So how could microdia-monds have formedwithin crustal rocks?

Larissa Dobrzhinetskaya,a visiting scientist fromUC Riverside, and ateam of Los Alamosresearchers have studiedthe mineral inclusionsfound inside the micro-diamonds. These inclusionsserve as environmentalrecords of the conditionsunder which the micro-diamonds formed.

Using a variety of analytical tools, including scanning, optical andtunneling electron microscopes and neutron diffraction at LosAlamos’ Neutron Science Center, the Los Alamos-UC Riversideteam discovered that microdiamonds have imperfect, skeletalcrystalline structures, much like the shape of a form of gypsumcalled desert rose, which is commonly found in the Southwest.Conversely, typical diamonds have perfect crystalline structures.

The microdiamonds’ imperfect structure suggests that they mostlikely formed in an oversaturated, impure environment. In other

ÈThe "house of

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formed frommedia

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and dur ing veryshort per iodsof geologica l

t ime.

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words, drops of fluid oversaturated with carbon and watereventually turned into diamonds in an environment laden withother minerals.

Those mineral inclusions included several types of silicates,carbonates and oxides, some of which are associated only withcrustal rock. Therefore, continental collisions may have forced atleast some of Earth’s crustal rock down a subduction zone, whereit “mixed” with mantle rock, then slowly rose back to the surfaceover tens of millions of years.

Researchers now are investigating the chemical compositions andcrystalline structures of the mineral inclusions to learn thepressures and temperature stability fields of such structures andmore precisely determine the depth at which the micro-diamonds formed.

In addition, Dobrzhinetskaya is performing high-pressureexperiments at UC Riverside to confirm the pressures andtemperature conditions in which the mineral inclusions mayhave been formed.

Dobrzhinetskaya and her colleagues postulate that the mineralinclusions were formed very deep inside the mantle. If they arecorrect, then the theory of plate tectonics must be reworked toaccount for how some crustal rocks managed to make a roundtrip from Earth’s surface down into the mantle and back, andunder what circumstances.

A paper detailing the team’s work has been submitted to thescience magazine

Nature and was presented last month at theAmerican Geophysical Union’s annual meeting in San Francisco.

Los Alamos’ Center for Materials Science, Institute of Geophysicsand Planetary Physics and Neutron Science Center and UCRiverside collaborated on this project, with support from LosAlamos’ Science and Technology Base Programs Office.

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DARHT ON TARGETHYDRODYNAMICS FACILITY

ACES FIRST TEST

The Dual-Axis Radiographic Hydrodynamic Test facility, a massive X-ray machine built to provide valuable

freeze-frame photos of materials imploding at speeds ofmore than 10,000 miles an hour, has successfully performedits first hydrodynamic test.DARHT, located at Los Alamos National Laboratory, is the newest andlargest experimental facility to come on line in the U.S. stockpilestewardship program, which ensures the safety and reliabilityof the U.S. nuclear arsenal without nuclear testing.

“The recent test proves DARHT’s technical capabilities and is amilestone we have been working toward for a decade,” said MikeBurns, DARHT project director. “The facility and the equipmentperformed magnificently.”

DARHT’s experiments are called hydrodynamic tests because metalsand other materials flow like liquids when driven by the high pressuresand temperatures generated by the detonation of high explosives.

“We got a very high-resolution picture,” said Todd Kauppila of LosAlamos’ Dynamic Experimentation Division, who was the lead experi-mentalist for the hydrotest. “DARHT gives us an excellent new tool touse in investigating the dynamics of implosions.”

The recent DARHT test marks the operational readiness of the first axisof the facility. When the second axis is completed in 2002, DARHT willhave two giant X-ray machines set at right angles, providing a morecomplete picture of what materials are doing as they implode.

DARHT does not lead to a nuclear reaction. It only provides a nonnuclearreplication of what occurs in a real nuclear weapon when the primarystage implodes. In a complete weapon, the primary stage acts as thetrigger for the nuclear explosion.

“The DARHT project has served as an outstanding example of what wecan achieve technologically,” said John Browne, Los Alamos director.

“DARHT represents excellence in science, engineering and projectmanagement. It sets a standard that others will have to work hard to

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equal,” Browne said. “It also gives us a tool that we need whenevery year we certify the safety and reliability of the nuclear stock-pile to the secretary of energy and secretary of defense, who then certifyto the president.”

DARHT’s team comprises about 150 Laboratory employees and subcon-tractors and includes staff from Lawrence Livermore and LawrenceBerkeley national laboratories.

“Simply put, DARHT’s X-rays are as key to the U.S. nuclear stockpilestewardship program as hospital X-rays are to helping to assess thehealth of the human body,” said Energy Secretary Bill Richardson.

“DARHT and the other tools of stockpile stewardship, includingmaterial science, and computer modeling and simulation, help toensure the safety and reliability of our current weapons systems,”Richardson said.

“I am tremendously proud of these men and women,” said Richardson,who met with the DARHT team last summer. “They are among the bestand the brightest from the U.S. science and engineering field.”

DARHT is capable of generating a beam of power equivalent to 20,000chest X-rays. The facility’s walls, built of specially reinforced concrete,are more than five feet thick in the area facing the high-explosives test.DARHT is capable of handling explosive loads up to the equivalent of150 pounds of TNT.

“Besides offering advanced optical and electronic diagnostics necessaryfor full-size hydrodynamic tests that are essential experimental confir-mation of weapons computer codes, DARHT also will providecapabilities for experiments investigating shock physics, high-velocityimpacts, and materials and high-explosives science,” said StephenYounger, Los Alamos’ associate Laboratory director for nuclear weapons.

“These data will benchmark computer calculations that will serve as thebasis for future nuclear stockpile decisions,” Younger said.

The budget for the recently completed first phase of DARHT is about$105.7 million. The second phase, when completed in 2002, isestimated to cost $154 million.

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LOS ALAMOS SHOOTSFIRST EVER ‘MOTION PICTURE’

OF IMPLOSION

The world’s first “motion picture” of the dynamics of an implosion has provided a new tool to see what occurs during the inward

burst of energy that triggers a nuclear weapon. Los Alamos researcherssay that a recent test of a revolutionary new technical applicationcalled proton radiography was highly successful. The technologyprovides the image of an object’s interior using high-energy protons,rather than the more traditional X-rays.The experiment was conducted at the Los Alamos Neutron Science Center using anexperimental device made of high explosives and aluminum. During the experi-ment, the implosion was triggered by a signal generated from a pulse of protons thatwas fired down the half-mile long, 800-million electron-volt LANSCE accelerator.

The accelerator fired multiple bursts of protons in an almost steady stream as specialcameras designed at Los Alamos caught and separated the image made by each burstin the sequence, producing a “motion picture.”

The experiment’s multi-image picture lasted about one ten-thousandth of a second,but a time sequence of 11 photographic images was shot, constituting a “motionpicture” of the implosion.

“This kind of tool will give us great insight into benchmarking computer codes thatare being developed in the weapons program as part of the Accelerated StrategicComputing Initiative,” said Mary Hockaday, leader of Los Alamos’ Neutron Scienceand Technology Group.

The British Atomic Weapons Establishment collaborated on the project, which wasone of a series of hydrodynamic experiments driven by high explosives that allowresearchers to study how materials behave. Solids and metals flow like liquids whendriven by the detonation of high explosives.

“This experiment was another important step in developing proton radiographyinto a crucial diagnostic tool for ensuring the safety and reliability of our nuclearstockpile in the absence of nuclear testing,” said Phil Goldstone, director of experi-mental programs at Los Alamos.

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PRESERVING THE PASTLOS ALAMOS ANALYZES NEW ENCLOSURES

FOR DOCUMENTS AT THE NATIONAL ARCHIVES

“We the People of the United States,in Order to form a more perfect Union ...”

T hose are perhaps the most important words in the Constitution of the United States, which along with the

Bill of Rights and the Declaration of Independence, is ondisplay at the National Archives in the nation’s capital. Morethan one million visitors every year file past the historicdocuments, which are housed in airtight enclosures topreserve the delicate parchment they were written on morethan 200 years ago. But as this century ends, officials from the National Institute ofStandards and Technology have concerns about the enclosures and haveembarked on a three-year project to design and build new ones. LosAlamos is assisting NIST by providing a scientific assessment of theproposed new encasements.

Last spring, Lance Hill of Engineering Analysis analyzed a model of theenclosure that was developed for NIST. Dick Rhorer at NIST, who is aformer Laboratory employee, found some deficiencies in the prototypeand asked the Laboratory to provide engineering structural analysissupport to aid in the final design of the encasements. Rhorer overseesthe mechanical design of the new encasements for NIST.

The current enclosures were built in 1952 and designed to have a100-year life span. However, when conservators at NIST examinedthem recently, they observed changes that could affect the documents.Hazy areas near where the Bill of Rights made contact with an innerpane of glass revealed possible sites of unwanted chemical reactions.Similar reactions were observed with the Declaration of Independence.They are caused by humidity inside the enclosures, among other things.

While some humidity is needed to keep the parchment from becomingtoo brittle, too much humidity can make the parchment swell andcontract, which can promote the growth of organisms.

The effect of the environment on the structural integrity of the encase-ment has been a central theme of Hill’s work. Weather systems can

change the barometric pressure, thereby changing the differencebetween pressure inside and outside the encasements. Once the inertatmosphere is set, a seal must be created and maintained for varyingweather conditions.

Hill also examined the C-seal that will bind the glass panes to thetitanium encasements and the 72 bolts that will bind the C-seal tothe encasements.

Hill’s group leader, Steve Girrens, said Los Alamos benefits fromcollaborations like this. “For our effort, we get a chance to validate ouranalysis methodologies in an unclassified environment,” he said. “Wehave the very best engineering analysis talent, along with the very bestanalysis tools and computing power in the world, right here atLos Alamos.”

NIST plans to unveil a new prototype encasement next year. Therotunda of the National Archives Building is closing for two yearsbeginning in July 2001. When it reopens in the summer of 2003, newencasements will hold and display all seven pages of the historicaldocuments.

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ÈMore than a

mi l l ion peoplev iew thehistor ic

documents atthe Nat ional

Archives everyyear .

Cade Mart in, Nat iona l

Archives and Records

Administrat ion

STUDENT RECEIVES AWARD FROM MEXICAN PRESIDENT

An former astrophysics student at Los Alamos has been awarded the highestacademic youth honor in the nation of Mexico for his studies of cosmic gamma raybursts. Enrico Ramirez-Ruiz traveled to the home of President Ernesto Zedillo toreceive the Premio Nacional de la Juventud - Rama Academica from the president.

“Los Alamos prides itself on its population of world-class scientists in a variety of fields,” said LaboratoryDirector John Browne. “And in the case of EnricoRamirez-Ruiz, that description applies even before hestarts on his first graduate degree.”

A student of astrophysicist and Los Alamos FellowEdward Fenimore, Ramirez-Ruiz has authored severalscholarly papers, specifically in the study of gamma raybursts, the largest cosmic explosions since the Big Bang.These titanic explosions flood the entire universe withgamma rays, and they are the brightest objects in the

universe — many of them gleaming 1,000 times brighter than a supernova.

Among the conclusions Ramirez-Ruiz has reached is that the random flickeringcharacteristic of gamma ray bursts is the same at the end of the burst as at the begin-ning, despite the fact that the burst’s source should have used up much of its energyby the end of the event.

Another of his papers analyzed how the bulk-motion energy dissipates. As Ramirez-Ruiz explains, a substantial energy reservoir must power gamma ray bursts, andseveral theories suggest merging massive objects such as neutron stars and blackholes are the source of the energy.

Observing very high-energy photons produced during the brief bursts givesresearchers information about the interior structure of the bursts. Ramirez-Ruiz’sinterpretation is that the bursts of energy are carried on a set of thin spherical layers(rather like the layers of an onion); and these layers are moving at a speed very closeto the speed of light. Current models don’t explain where all this relativistic energygoes, and the Los Alamos student and his mentor have come up with a model thataccounts for almost all this energy.

Ramirez-Ruiz presented a paper on “Filling Factors: A Hubble Relationship forGamma Ray Bursts” at the Gamma Ray Burst Symposium conference in Huntsville,Ala., where he was among the few undergraduates ever invited to present a paper.

Ramirez-Ruiz has begun his graduate work at Cambridge University, England,where he studies with the renowned astrophysicist Sir Martin Rees, RoyalAstronomer to Queen Elizabeth II.

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Enr ico Ramirez-Ruiz ( left )and Mexican Pres identErnesto Zedi l lo .

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SEEING EYE TO EYE

Researchers at Los Alamos havedeveloped a novel device for deter-mining the optical properties of thehuman eye. The instrument, whichassesses the optical characteristics ofthe eye lens, uses fiber optics torapidly and noninvasively determinethe overall optical quality of the lens.The process directs modest levels of

light into the eye for a few seconds and then measures the resultingbackscatter and fluorescence spectra. The data is collected andcompared to results in a database containing a reference set of data fornormal human lenses. The measurements can serve to document accel-erated optical aging or as indicators of cataracts or other diseaseprocesses. An industrial partner is sought to commercially develop thetechnology. C O N T A C T : I R V I N G B I G I O , ( 5 0 5 ) 6 6 7 - 7 7 4 8 , E - M A I L :

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MAKING SANS OF IT ALL

Using small-angle neutron scattering, researchers have gained a betterunderstanding of the microstructural properties of the high-explosivematerial used inside nuclear weapons. Small-angle neutron scattering,or SANS, has been around since the 1960s for studying the microstruc-tural properties of complex fluids,polymers and other materials, butonly over the past few years has itbeen used for studying the propertiesof HE systems. As the neutronsstrike the HE sample, they scatter atvery small angles. By measuring theangles of scatter, researchers candetect defects such as pits or crackswithin HE materials, and determine the material’s porosity and surfacearea. This information can then be fed into a computer for modelingpurposes to better predict weapon performance. Because neutrons arehighly penetrating, researchers don’t need to rely on special samplepreparation techniques. Microstructural characterization of HE systemsplays an important role in the Department of Energy’s Science-basedStockpile Stewardship Program from both a safety and performancestandpoint since cracks or pores in HEs caused by aging or damage canaffect weapon reliability and performance. C O N T A C T : J O S E P H

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WHEN BEAM MEETS TUMOR

Scientists recently discovered it is feasible to use the Monte Carlo trans-port method and powerful computers to calculate energy deposition andparticle transport caused by radiotherapy beams in the human body. TheMonte Carlo transport method is a process for obtaining an approximatesolution to certain physics and mathematics problems by using statis-tical sampling techniques. The calculation facilitates the optimumradiation dose delivered to the tumorwhile minimizing the dose given tonearby organs. The knowledge isuseful in reducing the risk inherentwith radiotherapy. The processrequires an accurate understandingof neutron, proton and photonbehavior in biological materials. Theknowledge came as a result ofnuclear model calculations and experimental programs run at theWeapons Neutron Research Facility at the Los Alamos Neutron ScienceCenter. C O N T A C T : M A R K C H A D W I C K , ( 5 0 5 ) 6 6 7 - 9 8 7 7 , E - M A I L :

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A WORLD OF WASTE

Radioactive wastes in the foothills of Peru, the outskirts of Mexico City,the Romanian countryside and even the Nile Delta are coming under thescrutiny of Los Alamos scientists. As part of a DOE effort to providetechnical cooperation in peaceful uses of nuclear energy, Los Alamos isproviding expert advice to effectively control and dispose of low-levelnuclear wastes around the world. Laboratory geologist Dennis Newell isconsulting with nuclear authorities to enable nations to develop respon-sible disposal practices and safety analyses for low-level radioactivewaste — typically those generated by medical therapies, industrial appli-cations and research, but not power reactors. Los Alamos nuclearphysicist Kenneth Apt, coordinating the effort, says his team has logged

trips to Cairo, Lima, Mexico Cityand Bucharest to help facilitymanagers and government officialsunderstand the comprehensive effortneeded to develop and use low-levelradioactive waste facilities in asocially responsible and economi-cally sustainable fashion. CONTACT :

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DO NEUTRINOSHAVE MASS?

RESEARCH PROBES THE MYSTERIOUS,

SUBATOMIC WORLD OF MINISCULE PARTICLES

L earning more about neutrinos could have an enormous impact on our understanding of the

composition and evolution of the universe.Although the sun and other stars generate and emit neutrinosconstantly by fusing hydrogen into helium, Earth and othercosmic bodies are virtually transparent to a neutrino.

Scientists calculate that three trillion neutrinos pass throughevery square centimeter of Earth’s surface every second, but onlyone in 10 billion ever interact with other matter. These weak andrare interactions with other particles make neutrinos difficult todetect and study.

In 1955, Los Alamos scientistsFrederick Reines and ClydeCowan Jr. used a detector called“Herr Auge,” or Mr. Eye, togather the first tangibleevidence of the existence ofneutrinos, which previously hadbeen known only in theory. Thisdiscovery earned Reines the1995 Nobel Prize in physics.

In 1996 a team of scientists atLos Alamos used the LiquidScintillator Neutrino Detector— a chamber filled with about60,000 gallons of pure mineral oil and 1,220 detectors — todemonstrate with a beam of neutrinos created by a linear acceler-ator that the tiny particles might indeed have mass.

At about the same time, Los Alamos researchers were leadingSAGE, a joint Russian-American experiment using 55 tons ofliquid gallium metal as a solar neutrino detector located deepunderground at the Baksan Neutrino Observatory in theCaucasus Mountains of Russia.

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ÕA researcherand the ear lyneutr inodetector “Herr Auge.”

Today, Los Alamos scientists arepursuing neutrino research inlocations around the world. TheLiquid Scintillator NeutrinoDetector experiment is moving toFermi National AcceleratorLaboratory. The Fermi version ofthe Los Alamos experiment,called Boone, will provide furtherevidence to validate or refute theneutrino mass discovery.

In another project, Los Alamosscientists are among hundreds ofinternational collaboratorsworking together in Japan’sKamioka mine on Super-Kamiokande, or Super-K — a

huge cylindrical tank of purified water surrounded by eleventhousand detectors called photomultiplier tubes.

Deep in the heart of Canada’s Creighton mine lies the SudburyNeutrino Observatory, another multinational collaborationinvolving researchers from Los Alamos. Located 6,800 feet belowthe surface, the Sudbury Neutrino Observatory contains 1,000tons of heavy water in an acrylic vessel 12 meters in diameter.Interactions between incoming neutrinos and the heavy water aredetected by the geodesic array of 9,600 photomultiplier tubessurrounding the vessel.

Neutrino research has come a long way since Reines' andCowan's first measurements and the ongoing work demonstratesthe neutrino's cosmological importance. The Standard Model, amodel that has ruled particle physics for nearly three decades,has as its cornerstone massless neutrinos. Since neutrino oscilla-tions can only occur if neutrinos are massive, any detectedoscillations constitute the first definite evidence of new physicsbeyond the Standard Model.

The neutrino's mass could eventually enable cosmologists todetermine the origins and ultimate fate of the universe, as thecombined mass of the wispy neutrinos may surpass the mass ofall other material in the universe.

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The ins ide ofthe L iquid

Sc int i l latorNeutr ino

Detector .

A MONTHLY PUBLICATION OF THEPUBLIC AFFAIRS OFFICE OF


Nonprofit Organization U.S. Postage Paid Albuquerque, NM

Permit No.532

IN THIS ISSUE:THE SEARCH

FOR COSMIC TRANSIENTSP A G E 1

SHIFTING THE THEORY

OF PLATE TECTONICSP A G E 7

DARHT ON TARGETP A G E 1 0

LOS ALAMOS SHOOTS

FIRST EVER ‘MOTION

PICTURE’ OF IMPLOSIONP A G E 1 2

PRESERVING THE PASTP A G E 1 3

PEOPLE IN THE NEWSP A G E 1 5

SCIENCE DIGESTP A G E 1 6

SCIENCE FOR THE

21ST CENTURYP A G E 1 8

LALP 00-1-1

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BRIEFLY …

Beginning with this issue, we’re adding a new feature to Dateline: LosAlamos: a monthly series titled Science for the 21st Century. Thearticles will be culled from Los Alamos National Laboratory PublicAffairs Office’s new weekly information series by the same name. TheScience for the 21st Century series highlights some of the extraordi-nary and groundbreaking science the Laboratory will be exploring inthe next century. This month we’ll unravel Los Alamos’ Nobel Prize-winning past, as well as its present role in the hunt for elusive neutrinoparticles. See pages 18 and 19 for the first installment. You can readthe weekly releases at the following address on the World Wide Web:http://www.lanl.gov/orgs/pa/science21.

Dateline: Los Alamos is availableon the World Wide Web:

http://www.lanl.gov/worldview/news/dateline/.


the search for cosmic transients

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