ction Point

Plasma Focusing of a Positron Beam - First EverTHE PLASMA LENS COLLABORATION has achievedsomething that's never been done before. It recently(April 2000) accomplished the focusing of a positronbeam (antimatter of electron) by means of a plasmalens. This is the first time this process has been observedanywhere, and it is an example of focusing an antimatterbeam with matter. It creates a potentially importantapplication for future linear colliders. For example, aplasma lens located at the interaction point inside adetector could focus both the electron and positronbeam, thereby reducing the beam spot size and thusincreasing the luminosity, perhaps by an order ofmagnitude or more. These may be importantconsiderations in the design of the NLC. Experiment E-150 Plasma Lens Collaboration contains members fromfour laboratories and three universities (see completelist at end of article).

The process started with a positron beam from thePEP-II positron source in Sector 19. The beam wastransported back toward the injector, sent through thedamping ring and then accelerated to an energy of 28.5GeV with 1 to 2 x 1010 e /bunch. This beam was deliveredthrough the beam switchyard to the Final Focus Test

Beam Facility (FFTB) at a rate of 1 to 10 Hz.At the focal point of the FFTB transport, a special

plasma chamber was installed. It contains a 3 mmdiameter pulsed gas nozzle through which eitherhydrogen or nitrogen gas is "puffed" into the vacuumsystem at high pressures (250 to 1100 pounds per squareinch).

The gas is removed from the plasma chamber bya vacuum pump. On either side of the central chamberare sections semi-isolated from each other by thintitanium windows that have small (2 to 5 mm diameter)openings for the positron beam to pass through. Thisarrangement allows operation of the plasma lens withultra-high vacuum systems on either side. The plasmalens was then generated by ionizing the gas with aninfrared laser.

"The theory of plasma lens focusing was firstproposed by Pisin Chen in 1987," said project managerDieter Walz, "so we have an accelerator theorist who isalso a co-spokesman for the experiment."

The relativistic positron beam carries both chargeand current. In a vacuum the electric repulsion of thepositrons is nearly neutralized by the magnetic

.. .. .1 . 1 "rT r

attraction among the particles. Itthis beam enters into a plasma, thecharge is neutralized primarily bythe fast motion of the plasmaelectrons. The current isneutralized due to thedevelopment of the "returncurrent" in the plasma. Adds Walz,"In typical high-energy beams,we've found that such currentneutralizations tend to be noteffective." This results in largeelectromagnetic fields that can self-focus the beam. The reduction inbeam spot size was measured usinga wire scanner with 4 micron and 7micron thick carbon fibers.

A second, independentmethod to measure the strength ofthe plasma lens is a segmented

(Continued on Page 5)

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Director's Cornerby Jonathan Dorfan

As you may have heard bynow, SLAC was honored bythe community recently forbeing a good neighbor. Wereceived the Golden Acornaward for community servicefrom the Menlo Park Chamber

..... I . -d l

of Commerce at an awards dinner on May 11. theaward recognized the efforts of many of you in theareas of education, charity and public service.

In recognition of the award we received a Letterof Congratulations from Senator Diane Feinstein, aCertificate of Appreciation from Senator BarbaraBoxer, a Certificate of Special CongressionalRecognition from Congresswoman Eshoo, a Letter ofCongratulations from California Governor GrayDavis, a Certificate of Recognition from State SenatorByron Sher, a Certificate of Recognition fromAssemblyman Ted Lempert, and a Commendationfrom the San Mateo County Board of Supervisors.We're delighted that our award garnered so muchattention.

Education has been a prime target for many ofour community activities. One-third of the 10,000visitors who tour SLAC each year are school-agedchildren. SLAC donates surplus equipment to publicschools for reuse and recycling. Scientists, engineersand others routinely donate time to schools as guestspeakers. The Task Force on communicationsrecognizes that these are all extremely valuablecontributions to the community and they will belooking for ways to increase and improve on ouroutreach efforts.

SLAC staff members are also very charitable.Throughout the year, many of you contribute to theStanford Blood Bank, which is of great benefit to thecommunity. Nina Stolar and the Public Affairs staffkeep those drives running smoothly. The food andtoy drive each holiday season nets close to 1000pounds of food and several boxes of toys for theneedy, and we can thank Mary Parish for her manyyears of service in that arena. Frequent travelershave collected hotel-size shampoos and soaps thatare then donated to Menlo Park organizations suchas Haven House, a transitional shelter for thehomeless, and the Boys and Girls Club. Last year theBoys and Girls Club used these supplies for theirannual summer camping trip. Our thanks to the TravelOffice staff for their help in this effort.

Our Housing Office has been an important part

of our community relations. Ute Hayes, Joan Parkerand Toni Campos work closely with our neighbors, tofind the right match between the type of rooms offeredfor rent and the many different types of users we havevisiting SLAC from all over the world. At the awardsdinner, I met several people in the community whocomplimented our Housing Office for their courtesyand our users for their consideration. The job of theHousing Office has become more difficult in the pastfew years and we are appreciative of their skill andexpertise under such competitive circumstances.

I know that many of you contribute an enormousamount of time and effort in your local areas inreligious organizations, environmental groups andprofessional societies. I am proud that our communityhas acknowledged us for our work and I look forwardto implementing new activities in the communitywith your help.

Thirty Year Award toGene Alvarado

IN A SPECIAL CEREMONY in the Director's Office,Gene Alvarado was presented with a beam tree inrecognition of his 30 years of service. Alvarado joinedthe SLAC Facilities Department in 1990, afterpreviously serving on Stanford Campus for 20 years asa custodian at Tressider. Alvarado was promoted in1995 to a supervisor role where he directs, schedulesand oversees a team of eight custodians at the Lab. Hehas also been selected for special recognition forextraordinary job performance while at SLAC.Congratulations, Gene!

The Interaction Point© 2000, is published by Stanford Linear Accelerator Center. Editor-in-chief, P.A. Moore; Production Editor, Vickee Flynn. Deadline forarticles is the fifteenth of every month. Items are published on a space-available basis and are subject to edit. Submissions may be sent electronically totip@slac.stanford.edu or by SLAC ID mail to TIP, MS 20. Phone (650) 926-4208.

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I =

SLAC Honored for Community Service

The Menlo Park Chamber of Commerce awardedSLAC the Golden Acorn Award for communityservice(http: //www. slac. stanford. edu/slac/

award/acorn2000 .html).

Jan LIolan, Ivlenlo rarK

City Manager, won theaward for OutstandingProfessional of the year.

Ron Oerenzi, Vice fresident oJBank of the West, introducesscholarship winner Elliott Baer,a senior at Menlo-Atherton HighSchool.

You can't see Ueora zumwalt benina me nair, out sne isentertaining her audience with stories about her neighbor(Joe Montana). (l-r) Edward Moore, Patricia Muhlestein,John Muhlestein (DOE Site Office). Zumwalt is GeneralCounsel at Stanford.

Community Relations for Stanford University, Mary JoBorak, Mayor of Menlo Park, and SLAC Director JonathanDorfan.

Jonathan and Renee Dorfan listened attentivelyto the accomplishments of the other awardwinners.

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SLAC Garden News and ViewsTHE SLAC GARDEN CLUB has been around since the1960s, although nobody seems to recall the exact dateit started. According to Finn Halbo, the first gardensite was where SCS (Building 50) now stands. Thegarden then relocated to a former steel storage yard ina valley below the location of the current TrainingCenter (Building 272). Georgia Row recalls how Halbohelped label and organize about 70 20x20 feet gardenplots. "Some profit from soda vending machines wasused to start the garden," recalled Halbo.

The third garden site was between SLAC Storesand Addison Wesley. This was by far the largest site,spanning about 150 10x20 foot plots. "I estimate thatthe garden moved there in 1979," says Adele Panofsky.

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Columbinm

In 1994, the garden was again displaced whenAddison Wesley developed the site for new buildings.After lengthy negotiations, the club was able to securethe land behind the Training Center. A clause in theBargaining Unit contract entitled each employee to agarden plot upon which to grow crops. Even withfinancial support from Addison Wesley and SLAC, thegarden could not have been created without the tirelesshelp of Rudy Malimban (currently retired), who spentmany hours clearing the dense shrubbery and installingplumbing. Club members also spent a number ofweekends reconditioning the soil at this former land-fill.

Throughout the years, garden club organizersincluded Herb Weidner, Walt Inman, Roxanne Jones,Adele Panofsky, and now the self-named "default clubpresident," Ruth McDunn. "I've been trying for years

Grapes

to find someone else to do the job," says McDunn. "I'llhandle the recordkeeping, if someone else will managethe plot assignments, annual compost purchase anddelivery," she added.

One reason gardeners enjoy tending their plots isthat they reap what they sow. "I like the idea of havingfreshly grown vegetables," says Yo Wackerman. "Somefruits and vegetables taste really different from store-bought, such as tomatoes and swiss chard."

Others like Ramona Theobald, who has a plotfilled with multi-colored flowers, take advantage ofSLAC's warm climate and spaciousness. "My gardenat home is shaded, so at SLAC I can get differentvarieties," Theobald adds.

The health benefits of gardening are also anotherdraw. "I notice that I am healthier during the summerwhen I'm out working in the garden," says RaffaMiranda, adding that "eating fresh strawberries andraspberries fortifies my immune system." Peggy Tankalso states, "(Gardening) is the best medicine for stress."

Many gardeners try to be organic, preferring notto use pesticides or other chemicals on their plots.When asked why she is an organic gardener, Tankreplied, "The greatest grower is nature."

SLAC gardeners also use their harvest in a numberof valuable ways. "I give (extra produce) to my elderlyneighbors or donate to Second Harvest Food Bank,which provides frozen and fresh food to soup kitchens,elderly, and other communities," says Dennis Norris.

For more information on the SLAC Garden andgeneral gardening tips, check out the Garden website.(http://www-project.slac.stanford.edu/garden)

-Lily Wong

4

Work Safe, Work SmartThere have been no new injuries involving daysaway from work reported since 1/24/00. Thenumber of calendar days between then and thisupdate of 5/16/00 is 113 days. SLAC's recordnumber of days between claims remains at 150days.

SLAC Health FairThe SLAC Medical Department is excited to presentthe SLAC Health, Safety and Ergonomics Fair onJune 14, 2000 from 10:00am to 2:00pm. We needvolunteers to assist vendors from 9:30am to 2:30pm.No heavy lifting is required. Please contact DebbieAlwyn at Ext. 4588.

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Plasma Focusing (Continued)

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Plas Focusing of Pitron Beams

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synchrotron radiation monitor that is located about 35meters down beam of the lens. The harder the beam isfocused the higher the critical energy of thesynchrotron radiation. As the plasma focusing effectis transient, the monitoring of such synchrotronradiation provides an "on-line" measurement of theplasma-focusing gradient. It was about 10 Gauss/cmfor this experiment.

The plasma lens concept also works if there is nopre-ionization by the laser. This process is called selfor impact ionization. In this case, the head of thepositron bunch ionizes the gas and the remainder ofthe bunch is then focused. Since the head of the bunchis not focused, the efficiency in spot size reduction isnot as high as for the laser pre-ionization. The twographs depict plasma focusing for a hydrogen and anitrogen lens, for laser and self ionizations. Thedecrease in beam size was approximately a factor of 2for nitrogen. The reduction in the orthogonaldimension was comparable, i.e., the reduction in spot

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Plasma Focusing of Positron Beam

-10 --5 0 5 10 15 20 25Z(mm)

size was approximately a factor of 4 for this case. Themaximum possible spot size decrease is much higher,but the beam current had to be lowered and theincoming beam size enlarged in order not to melt thefragile carbon fibers in the wire scanner on account ofthe very high energy density of the focused beam.

"The collaboration is excited about potentialfuture applications of this concept and is also planningon repeating this experiment, using electron beamsfocused by a laser ionized plasma," said Walz.

The members of the collaboration, by institution,are as follows: FNAL (C. Crawford, R. Noble), KEK-Japan (K. Nakajima), LLNL (H. Baldis, P. Bolton), SLAC(P. Chen, W. Craddock, F.-J. Decker, C. Field, R. Iverson,F. King, R. Kirby, J. Ng, P. Raimondi, D. Walz),Hiroshima University--Japan (A. Ogata), UCLA (D.Cline, Y. Fukui, V. Kumar), University of Tennessee(A. Weidemann). Co-spokesmen are Baldis, Chen andCline.

Talk, Walk, and Clean A Big Success"WE REALLY WANT TO thank those folks who thoughtahead and ordered pallets. That made the job easier,"said Leslie Normandin in Property Control. This year'sTalk, Walk and Clean was a big success given the greatparticipation, the positive morale and the volume ofstuff collected. Salvage picked up equipment, furniture,and materials, some of it quite ancient. In addition toall the stuff collected, trashed or recycled, there were agood number of lessons learned and success stories.

"We still have to sort the recycles," saidNormandin. "Unfortunately, there was trash mixed inwith recyclable materials. In one box we even foundopen exacto knives," she said. Such situations meantextra time and effort in sorting.

In other cases there were unidentified liquids,lead and batteries. A reminder to staff members thatthese types of items need to be disposed of through the

Waste Management Department. Salvage continues towork with some departments by picking up, sortingand disposing remaining discarded material.

One thing to keep in mind for the future: youdon't have to wait for annual cleanups. Turn inequipment and computers as soon as they are identifiedas excess. Then SLAC has a higher success rate donatingthem to public schools or other non-profit groups.

Enthusiasm was the story of the day. Hats off tothe energetic group led by Perry Anthony in EFD. Theyfound 57 items in their walk, many of which they fixedon the spot. Nina Stolar reports that her groupcontained Emeritus Directors Panofsky and Richterand current Director Dorfan, "And they all participatedenthusiastically," said Stolar, "which is a great examplefor the rest of the lab. I can't wait until next year."

5

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Take Our Daughters To Work DayCommittee Members:Ann TrautweinBarbara JohnsonBrenda WarrenCherrill SpencerDana MillicanJoli SteiberLesley WolfLily WongPauline WethingtonSharon BurnsSusan HoergerVern SmithVictoria Sha

From Tech Pubs--Banners,Open House Poster: the girls for this group photo.Chip Dalby

Open House Leaders:Jim Allan-Radiation DemonstrationJohn Weisskopt-Computer Building TourGloria Labrador, Medical TourPat Kreitz-Library TourRuth McDunn-Technical Publications Q&ADon Loquiao-Fire Station TourDenise Larsen-Machine Shop DemonstrationsHoward Rogers-Shark Key Chain and CuttingMetal with Wire

Security Staff, who produced 50+ picturebadges within 30 minutes:Dave MaciasKim GasperNatalie AyelsworthCarry Cross

What's my line panelists:Carol Morris, Health Physics TechnicianDana Millican, Mechanical TechnicianRuth McDunn, Web Information ManagerNancy Yu, EngineerJulia Thom, PhysicistHelen Nuckolls, Geologist

Workshop Leaders:Magnetic Measurements-Zachary WolfVacuum Science-Dave BosticComputer-Aided Drafting-Kurt VallencourtSSRL Electronics-Ramona TheoboldSSRL Electronics-Teresa Troxel Dave Jensen, MET, explaining the use of magnetometers.Radiation-Jim AllanMCC-Sibylle Petrak Parents who volunteered to be tour guides:Electroplating Shop-Ali Farvid Boni GrimaldiMachine Shop-Denise Larsen Ron Pacheo

6

Gerry Nelson RetiresIT WAS A DAY blessed by the gods: subreeze blowing through the oak trees, <

Family and friends gathered to say good-Accelerator Department's Safety Officer, c

Retired friends came from far and near to ,along with co-workers, family and othventured up from Palm Springs and Hal SrCalifornia. Ken Crook, from his residencewas present to wish Gerry as muchretirement happiness as he isexperiencing. Vern Price, who incidentlyclaims to have been the one to hire Gerryas an operator, came out of retirementmode to share with the group what Gerrywas like before he became Mr. Safety. Itwas particularly good to see RogerAnderson (Tiny) and Al Neubieser(Neuby), our very own Main ControlCenter guys who have remained in thearea. Clenaenin.

Gerry admits to being a real Stanfordcommunity family member. His professional career began in

1962. He met his wife Ruth Thor Nelson at Stanford, and they

were married at Memorial Church. His son Erik is a Stanfordgraduate and his daughter Kristina is head of a division at the

Medical School. Gerry's first job was, naturally, on the Stanford

Campus. He came to SLAC as an operator under Vern Price andlater on in his career he worked in Safety under Ken Crook.

Gerry promises that when he finishes one of those vintagecars he's working on, he'll drop by and show it off. His wife,

Ruth, will certainly thank him for freeing up the garage.

-Glena Stewart (1-r) Rust)Bob Fulle

y Humphrey, Kuth i nor ielson, Hlat 3mitn,er, Cliff Rogers.

SLAC Document Wins Achievement Award

SLAC HISTORY IS EXCITINGnews! In April 1999 wepublished a brochure calledEnvironment, Safety, and Healthat SLAC. In December 1999 itwon an Achievement Awardin the Northern CaliforniaTechnical CommunicationCompetition, sponsored by theSociety for Technical

Communication (STC). On February 26, 2000, RoxanneJones went to the STC Awards Banquet in Sacramentoto accept the Touchstone 99 achievement award.

Roxanne Jones, formerly lead technical writer ofES&H, now a production editor in TechnicalPublications, prepared the document with the help oftechnical writer Hillary Russak and several membersof the ES&H Division. For their efforts, Russak and the

ES&H staff members were recognized as contributors,sharing the award with Jones.

Comments from the judges about the brochureincluded: "Well put together report." "Having seenseveral similar from both public and private sources,this is certainly one of the more approachable.""Binding and cover are public-friendly within a limitedbudget." "Clearly laid out and with a more readablestyle than many."

Environment, Safety, and Health at SLAC, SLAC-I-720-0A86N-001, is an historical document describingthe progress of environment, safety, and health issuesat the laboratory since the establishment of the ES&HDivision in 1990. It can be viewed on the ES&H websiteunder Publications, ES&H brochure. While the 1999brochure won the award, an updated version for 2000is also available.http://www.slac.stanford.edu/esh/esh.html

-Larissa Williams7

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L

te\ 5 from the

^ Xs\V/eb Information Manager&VJ5 RZuth McPunn. mcdunn@sLac

Safety Never Takes a Rest!SINCE I'M HELPING TO edit thismonth's Interaction Point, Ithought I might take a break fromwriting my Operating SafetyCommittee column. After all,everyone already knows how tobe safe, don't we?

In fact, our personal safety_

comes up against many challenges each day. Some ofthese challenges are caused by our own complacency,but others are directly linked to the behavior of others.Here's an example of a note I received recently. "Bicyclesafety is still an issue. A co-worker was almost run overon the Central Lab loading dock. The signs are toosmall and are ignored. Yesterday afternoon I sawsomeone riding a bike on the loading dock whilewearing headphones."The author of the noteacknowledged that Security cannot be everywhere andthat they do have other concerns to deal with throughthe day. He suggested that "enforcement of these lowlevel rules could fall to other people, even if it is onlythe official ability to notify a supervisor of unsafebehavior." That's what I like-someone who points outnot only the problem, but also presents a workablesolution.

So my column this month exists because we can'treally take a break from safety, can we? And, forwhatever power the written word gives, I hereby

Nelson, Gerald, AD, 5/31/00Noyes, Pierre, Theory, 4/28/00Robertson, Ralph, PCD, 6/30/00

Do you have a milestone you would like published in TIP?Email tip@slac.stanford.edu to have it included.

deputize you as readers to assist Security and thedesignated safety professionals on site to keep SLAC ahealthy environment for all.

If you see an action that jeopardizes the safety ofanyone (including yourself), tell the person performingthe unsafe act. Or at least notify a supervisor (or UTRfor contractors), so everyone can work towardpreventing repeated violations. And also rememberthat help from the ES&H Division (via the ResourceList pointers) and Security (x2551) is only a phone callaway. We'll all benefit from the fact that there are novacations from safety!

-Janice DabneyChair

Operating Safety Committee

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Useful Web Pages

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