We have demonstrated production of antihydrogen in a 1$,$T solenoidal
magnetic field. This field strength is significantly smaller than that used in
the first generation experiments ATHENA (3$,$T) and ATRAP (5$,$T). The
motivation for using a smaller magnetic field is to facilitate trapping of
antihydrogen atoms in a neutral atom trap surrounding the production region. We
report the results of measurements with the ALPHA (Antihydrogen Laser PHysics
Apparatus) device, which can capture and cool antiprotons at 3$,$T, and then
mix the antiprotons with positrons at 1$,$T. We infer antihydrogen production
from the time structure of antiproton annihilations during mixing, using mixing
with heated positrons as the null experiment, as demonstrated in ATHENA.
Implications for antihydrogen trapping are discussed

A Boston

A Deutsch

A Olin

A Povilus

Andresen G

C L Cesar

D M Silveira

D P van der Werf

D R Gill

E Sarid

F Robicheaux

Fajans J

G B Andresen

J Fajans

J S Hangst

J S Wurtele

J W Storey

K Gomberoff

K Olchanski

L Kurchaninov

L V Jørgensen

M C Fujiwara

M Charlton

M Chartier

M J Jenkins

N Madsen

P D Bowe

P Nolan

R D Page

R Funakoshi

R Hydomako

R I Thompson

R S Hayano

S Chapman

W Bertsche

Y Yamazaki

English

arXiv

Michael Charlton

Dirk van der Werf

Niels Madsen

Cronfa at Swansea University

Production of antihydrogen at reduced magnetic field for anti-atom trapping

We have demonstrated production of antihydrogen in a 1$,$T solenoidal magnetic field. This field strength is significantly smaller than that used in the first generation experiments ATHENA (3$,$T) and ATRAP (5$,$T). The motivation for using a smaller magnetic field is to facilitate trapping of antihydrogen atoms in a neutral atom trap surrounding the production region. We report the results of measurements with the ALPHA (Antihydrogen Laser PHysics Apparatus) device, which can capture and cool antiprotons at 3$,$T, and then mix the antiprotons with positrons at 1$,$T. We infer antihydrogen production from the time structure of antiproton annihilations during mixing, using mixing with heated positrons as the null experiment, as demonstrated in ATHENA. Implications for antihydrogen trapping are discussed.We have demonstrated production of antihydrogen in a 1$,$T solenoidal magnetic field. This field strength is significantly smaller than that used in the first generation experiments ATHENA (3$,$T) and ATRAP (5$,$T). The motivation for using a smaller magnetic field is to facilitate trapping of antihydrogen atoms in a neutral atom trap surrounding the production region. We report the results of measurements with the ALPHA (Antihydrogen Laser PHysics Apparatus) device, which can capture and cool antiprotons at 3$,$T, and then mix the antiprotons with positrons at 1$,$T. We infer antihydrogen production from the time structure of antiproton annihilations during mixing, using mixing with heated positrons as the null experiment, as demonstrated in ATHENA. Implications for antihydrogen trapping are discussed

Andresen, G.B.

Bertsche, W.

Boston, A.

Bowe, P.D.

Cesar, C.L.

Chapman, S.

Charlton, M.

Chartier, M.

Deutsch, A.

Fajans, J.

Fujiwara, M.C.

Funakoshi, R.

Gill, D.R.

Gomberoff, K.

Hangst, J.S.

Hayano, R.S.

Hydomako, R.

Jenkins, M.J.

Jorgensen, L.V.

Kurchaninov, L.

Madsen, N.

Nolan, P.

Olchanski, K.

Olin, A.

Page, R.D.

Povilus, A.

Robicheaux, F.

Sarid, E.

Silveira, D.M.

Storey, J.W.

Thompson, R.I.

van der Werf, D.P.

Wurtele, J.S.

Yamazaki, Y.

CERN Document Server

arXiv:0807.0220v1  [nucl-ex]  1 Jul 2008Production ofA ntihydrogen at R educed M agnetic Field for A nti-atom TrappingG .B.Andresen,1 W .Bertsche,2 A.Boston,3 P.D.Bowe,1 C.L.Cesar,4 S.Chapm an,5 M .Charlton,2M .Chartier,3 A.Deutsch,5 J.Fajans,5 M .C.Fujiwara,6 R.Funakoshi,7 D.R.G ill,6 K .G om bero,5J.S.Hangst,1 R.S.Hayano,7 R.Hydom ako,8 M .J.Jenkins,2 L.V.Jrgensen,2 L.K urchaninov,6 N.M adsen,2 P.Nolan,3 K .O lchanski,6 A.O lin,6 R.D.Page,3 A.Povilus,5 F.Robicheaux,9 E.Sarid,10D.M .Silveira,4 J.W .Storey,6 R.I.Thom pson,8 D.P.van derW erf,2 J.S.W urtele,5 and Y.Yam azaki11(ALPHA Collaboration)1Departm ent ofPhysics and Astronom y, Aarhus University, DK -8000 Aarhus C,Denm ark2Departm ent ofPhysics, Swansea University, Swansea SA2 8PP,United K ingdom3Departm ent ofPhysics, University ofLiverpool, LiverpoolL69 7ZE,United K ingdom4Instituto de Fsica,Universidade Federaldo Rio de Janeiro,Rio de Janeiro 21941-972, Brazil5Departm ent ofPhysics,University ofCalifornia atBerkeley,Berkeley,CA 94720-7300, USA6TRIUM F, 4004 W esbrook M all, Vancouver BC, Canada V6T 2A37Departm ent of Physics, University of Tokyo, Tokyo 113-0033, Japan8Departm ent ofPhysics and Astronom y,University ofCalgary,Calgary AB,Canada T2N 1N49Departm ent ofPhysics, Auburn University, Auburn, AL 36849-5311, USA10Departm ent ofPhysics,NRCN-Nuclear Research Center Negev,Beer Sheva,IL-84190,Israel11Atom ic Physics Laboratory, RIK EN, Saitam a 351-0198, Japan(D ated:April20,2013)W e have dem onstrated production ofantihydrogen in a 1T solenoidalm agnetic eld. This eldstrength issignicantly sm allerthan thatused in the rstgeneration experim entsATHENA (3T)and ATRAP (5T).The m otivation for using a sm aller m agnetic eld is to facilitate trapping ofantihydrogen atom s in a neutralatom trap surrounding the production region. W e report theresultsofm easurem entswith the ALPHA (Antihydrogen LaserPHysicsApparatus)device,whichcan captureand coolantiprotonsat3T,and then m ix theantiprotonswith positronsat1T.W einferantihydrogen production from the tim e structure ofantiproton annihilations during m ixing,usingm ixing with heated positrons as the nullexperim ent,as dem onstrated in ATHENA.Im plicationsforantihydrogen trapping are discussed.Cold antihydrogenatom swererstsynthesized and de-tected in 2002 [1]by the ATHENA collaboration attheCERN Antiproton Decelerator(AD)[2].Theneutralan-tihydrogen atom s were not conned;in fact,ATHENAdetected the annihilation ofthe antiproton and positronin spatialand tem poralcoincidence to dem onstrate an-tihydrogen production. The ATRAP collaboration re-ported a sim ilarresult,using an indirectdetection tech-nique based on eld ionization [3],shortly thereafter.Inboth ofthe initialexperim ents,antihydrogen was pro-duced bym ergingplasm asofantiprotonsandpositronsinliquid helium cooled Penning traps.ATHENA observedpeakantihydrogenproductionratesofup toabout400Hz[4],im m ediately suggesting that an experim ent to traptheneutralanti-atom scould befeasible.Trapping ofan-tihydrogen is probably necessary,ifthe long-term goalofperform ing precision spectroscopy ofantihydrogen isto be realized.G ravitationalstudiesusing antihydrogenwillalm ostcertainly requiretrapped anti-atom s.W e have constructed the rst apparatus designed toproduce and trap antihydrogen. The ALPHA (Antihy-drogen Laser PHysics Apparatus) device com bines an-tihydrogen synthesis Penning traps with a superposedm agnetic gradient trap for neutrals. This device fea-tures a transverse octupole winding and a unique lon-gitudinalm agneticeld conguration involving m ultiplesolenoidalwindings[5],designed to optim ize antiprotoncapture, antihydrogen production rate, and antihydro-gen trapping probability.In thisLetter,wedem onstrateantihydrogen production at1T in thism ultiple solenoidconguration.Neutralatom s,or anti-atom s,can be trapped by ex-ploitingtheinteraction oftheirm agneticdipolem om entswith an inhom ogeneousm agnetic eld.A potentialwellcan beform ed using a m inim um -B conguration,asrstdescribed by Pritchard [6]. The Ioe-Pritchard cong-uration utilizes a cylindricalquadrupole for transverseconnem entand solenoidalm irrorcoilsforcreating thelongitudinalwell.The ALPHA apparatus,illustrated inFigure 1,replaces the quadrupole with an octupole,inorderto m inim ize perturbations that could lead to lossofthe charged particle plasm asused to form antihydro-gen. M ost laboratory Penning trap plasm as are storedin solenoidaleldshavinghigh uniform ity and rotationalsym m etry,since the plasm as depend on this sym m etryfor their long-term stability [7]. The deleterious eectsofa quadrupoleeld and theadvantagesoftheoctupoleconguration are described elsewhere [8,9,10,11]. Anearlierexperim entin theALPHA apparatus[12]showedthatpositronsand antiprotonscan be stored in a strongoctupole eld for tim es com parable to those needed toproduceantihydrogen in ATHENA.Thesolenoidaleld needed toconnecharged antim at-terparticlesrepresentsa m ajorchallenge forthe designofan eective antihydrogen trap. The trap depth ofa2ext. scintillators scintillators (1 of 4 shown)pbar catching mixing positrons positron transfermain solenoid(length indication)inner solenoidfaraday cup/final degraderleft mirroroctupoleright mirrorhelium volumecryostat0.00.51.01.52.02.53.0-600 -400 -200 0 200 400 600 800 1000Axial Position [mm]axial field [T]pe+/e-FIG .1: Schem atic diagram ofthe ALPHA apparatus. Thegraph showstheon-axislongitudinalm agneticeld duetothesolenoids and m irror coils. The blue (red) curve is the eldwith (without)the innersolenoid energized.neutraltrap isgiven byU = (B m ax   B m in); (1)where  isthe anti-atom ’sm agnetic dipole m om entandB m ax and B m in are the m axim um and m inim um m ag-netic eld strengths in the device. In a com bined Pen-ning/neutralatom trap,the solenoidaleld forthe Pen-ning trap isB m in.Longitudinally,B m ax isgiven byB m ax = B s + B m ; (2)where B s is the solenoid eld and B m is the peak elddue to the m irrorcoil.Transversely,wehaveB m ax =qB s2+ B w2; (3)whereB w isthetransverseeld strength ofthem ultipoleatthe innerwallofthe Penning trap.The m axim um trapping elds obtainable are funda-m entally determ ined by thecriticalcurrentin thesuper-conductor used to generate the eld. The criticalcur-rentisin turn largerforsm allerexternaleld strength.Thusthesolenoidaleld should beassm allaspossibletom axim izethetrap depth.Q uantitatively,atrap depth of1T providesabout0.7K oftrappingpotentialforgroundstate antihydrogen. (Note that the highly excited anti-hydrogen statesobserved in ATRAP and ATHENA m ayhave signicantly largerm agnetic m om entsand thusbem ore trappable. Cold rubidium atom sin highly excitedRydberg stateshave recently been trapped [13]in a su-perconducting Ioe-Pritchard trap.) Assum ing thatthem axim um eld strength in the superconductoris 4-5T,a background solenoidaleld of3 or 5T represents anundesirably largebiaseld forthetrap.Thesituation isexacerbated by the factthat the inner wallofthe Pen-ning trap is radially separated by a few m m from theinnerm ost superconducting windings,due to the thick-nessofthem agnetsupportstructureand ofthePenningtrap itself. The loss ofusefuleld strength in this dis-tanceisparticularlysignicantforhigherorderm ultipolem agnets.In theabsenceofaneutraltrap,alargesolenoidaleldisdesirableform ostaspectsoftheantihydrogen produc-tion cycle. The antiprotons from the AD are slowed ina foil(naldegraderin Figure 1)from 5.3M eV to 5keVorlessbeforetrapping.The beam ,which ispartially fo-cused by traversing the fringe eld ofthe solenoid,hasa transverse size of a few m m at the foil. Scatteringin the foiladdsdivergence to the beam . The solenoidaleld strength and thetransversesizeofthePenning trapelectrodes (33.6m m diam eter for the ALPHA catchingtrap)thus determ ine what fraction ofthe slowed parti-cles can be transversely conned. High m agnetic eldis also favored by considerations ofcyclotron radiationcooling tim es for electrons and positrons,positron andantiproton plasm a density (and thus antihydrogen pro-duction rate),and plasm a storagelifetim es.In thefollowingweconcentrateon m anipulationswith-outthe transverse octupole eld energized. A m easure-m entofthe relative antiproton capture eciency versussolenoid eld strength in ALPHA isshown in Figure 2.For this m easurem ent, the antiproton bunch from theAD,containing typically 2 107 particles in 200ns,wasslowed and trapped by pulsingthe5kV antiproton catch-ing trap;see Figure 1.The "hot" antiprotonswere thenheld for500m s,before being released onto the nalde-grader(see Figure 1),where they annihilate. The anni-hilation products(charged pions)werecounted using theexternalscintillation detectors(Figure1).Them agneticeld was provided by the ALPHA double solenoid sys-tem . The m ain (external)solenoid washeld at1T,andthe internalsolenoid was varied from zero to 2T.The3T eld isabouta factorofeightm ore eective than a1T eld for capturing antiprotons,so the use ofa sin-glesolenoid atlow eld fora com bined apparatusseem silladvised. The ALPHA double solenoid is designed tocatch antiprotonsat3T and to produceantihydrogen at1T in thecom bined neutral/Penningtrap.In thefollow-ing we dem onstrate that the anticipated reductions inpositron and antiproton density in the 1T eld are notprohibitiveforantihydrogen production.Foreach m ixing cycle with positronsto produce anti-hydrogen,threebunchesofantiprotonsfrom theAD werecaptured,cooled through interactionswith a previouslyloaded plasm a of cold electrons, and then transferred(without electrons) to a potentialwelladjacent to them ixing region in the 1T eld region;see Figure 1. Theleftm irrorcoil(adjacentto theinnersolenoid)wasener-gized to providea sm ooth transition from the3T regionto the 1T region. This transfer wasaccom plished withtypically lessthan 10% lossin antiprotons.Theantipro-tons were then injected into the m ixing region, whichhasthe potentialconguration ofa nested Penning trap[14](Figure 3a),containing positronsfrom the ALPHApositronaccum ulator[15].Typicalparticlenum berswere7000 antiprotonsinjected into 30 m illion positrons.Theentiretrappingapparatusiscooled to4K by thecryostatforthe innersuperconducting m agnets.The antiprotons,which are injected into the positron300.20.40.60.811.20 0.5 1 1.5 2 2.5 3 3.5Fraction of Antiprotons CaughtMagnetic Field Strength (T)FIG .2: Relative antiproton capture eciency versus m ag-neticeld strength.Them easurem entsarerelativeto there-sultfor3T.The uncertaintiesreectcounting statisticsonly(1 standard deviation.)plasm a with a relative energy ofabout 12 eV,slow byCoulom b interactionwith thepositrons,aspreviouslyob-served in ATHENA [16]and ATRAP [17].The resultofslowing can be observed by ram ping down the trappingpotentialto determ ine at what energy the antiprotonsare released. Figure 3 dem onstratespositron cooling ofantiprotons at 1T in ALPHA.W ith no positrons,theantiprotons rem ain at the injection energy (Figure 3b).W ith positronspresent,theantiprotonscooltoan energyapproxim ately corresponding to the potentialat whichthe positron plasm a is held (Figure 3c). In ATHENA,cooling to thislevelwascorrelated with the onsetofan-tihydrogen production [16],as m easured by the rise inevent rate in an antiproton annihilation detector. Theneutralantihydrogen escapes the Penning trap and an-nihilateson the electrodewalls.For the following m easurem ents, the apparatus wasequipped with four scintillation detectors read out byavalanche photodiodes. The detectors were placed in-side the outersolenoid and adjacentto the m ixing trap(Figure1).An eventwasregistered iftwo orm oreofthedetectorsred in coincidence(100nswindow).Thesolidanglesubtended by the detectorswasabout35% of4.Figure 4 illustratesthe tim e developm entofthe anni-hilation eventrate afterthe startofm ixing. Two casesare shown; "norm al" m ixing and m ixing in which thepositronsareheated to suppressantihydrogen form ation[1]. The heating isachieved by exciting the axialdipolem odeofthepositron plasm a,again following establishedpractice from ATHENA [18]. In norm alm ixing we ob-servetheinitialrisein eventrate,asseen in theATHENAapparatus, but with a considerably slower rise tim e -about1shereasopposed toafew tensofm s.Thislongercoolingtim eisprobablyduetothelowerpositron plasm a020406080100120 30  25  20  15  10  5 0020406080100120energy in well (eV)annihilation counts (arbitrary units)020406080100120b)c)d)-60-40-200204060Axial Position [mm]e+a)left wellright wellFIG .3:a)Theon-axispotentialin thenested trap.Theblueshaded region istheportion ofthecenterwellthatisattenedby the positron space charge potential. b-d)Antiproton en-ergy distributions in the nested trap potentialm easured byram ping down the left potentialwall. The relative num berof released antiprotons is plotted versus energy for b) an-tiprotonsonly,c)norm alm ixing with cold positrons,and d)m ixing with heated positrons.In allthree cases,theantipro-tonswerereleased in 200m safter50sofstoragein them ixingtrap.The horizontalaxisscale iscom m on to allfourgures.The uncertaintiesreectcounting statisticsonly (1 standarddeviation.)density in the 1T eld,although we have notm easuredthe density directly. The positron num ber here is alsolower,by a factorof2 to 3,than in [16].The ATHENA experim entused position sensitive de-tection ofantiproton and positron annihilation productstoobtain theveryrstevidenceforantihydrogen produc-tion at the AD.In subsequent experim ents,experience40 5 10 15 20 25 30 35 40 45 5010203040500 1 2 3 4 502468101214Time since start of mixing (s) Annnihilation counts (arbitrary units)FIG .4: Scintillation events as a function oftim e after thestart ofm ixing,for norm alm ixing (black) and m ixing withheated positrons(red).The tim e binsare 1slong.The dataarefor10 m ixing cycles,norm alized to onecycle.Theinsetisa plotofthe rst5softhe sam e data,re-binned into 200m sbinstoillustratetherisetim eoftheantihydrogen production.The uncertaintiesreectcounting statisticsonly (1 standarddeviation.)with the device dem onstrated thatitwasnotnecessaryto rely on the position-sensitive detection to distinguishantihydrogen production from antiproton loss [4,19,20].Thetriggerratesignalfrom theannihilation detectorex-hibitsa tim e structure that,in concertwith evidence ofantiproton cooling,can be interpreted asa signatureforantihydrogen production. M ixing with heated positronsleadsto inecientslowingand coolingoftheantiprotonsand inhibitsantihydrogen production,and thuscan serveasthe nullexperim ent. In ALPHA,asin ATHENA,noevidence for signicantantihydrogen production or sig-nicantantiproton lossisseen with heated positrons,al-though both speciesofparticlearepresentand spatiallyoverlapping during the cycle. (The events in the veryrst tim e bin,for both cases,include "hot" antiprotonlossescaused by the rapid potentialm anipulationsusedto injectthe particlesinto the nested trap.) W e thusin-terpret the annihilation signalfor cold m ixing as beingdueto a tim e-varying antihydrogen production superim -posed on a largely at background due to cosm ic raysand slow and sm allantiproton losses. (There m ay be asm alladm ixture ofantihydrogen production even withheated positrons,at tim es greater than about 12s,butwehavenotyetinvestigated thisin detail.)Based on a knowledge ofthe num ber ofantiprotonstypically injected into the m ixing trap, and the num -ber rem aining when the trap is dum ped at the end ofthe cycle,we estim ate that up to 15% ofthe antipro-tons could have produced antihydrogen. This num beris consistent with the totalnum ber ofevents observed,given theestim ated scintillatordetectoreciency,and itiscom parable to thatobserved undertypicalconditionsin ATHENA [4].Theobservationofantihydrogenproduced in a1T eldisasignicantdevelopm entforthefutureofantihydrogentrappingexperim ents.Forexam ple,thedesignoftheAL-PHA apparatusisfora m axim um of1.91T oftransverseeld from theoctupolein a1T solenoid,correspondingtoawelldepth of1.16T.Thewelldepth fora3T solenoidaleld and thesam esuperconducting m agnetconstructiontechnique [5]would be lessthan 0.5T,when the reduc-tion in criticalcurrentistaken intoaccount.Therelativeeasewith which antihydrogenwasproduced heresuggeststhatattem ptsateven lowersolenoid eldsm ay succeed,leading to even largerneutralwelldepths. For possibleworkatlowereld,theALPHA devicefeaturesthecapa-bility ofapplying rotating wallelectric elds [21,22]tocom pressthe antiproton and positron cloud radiibeforem ixing,ifnecessary.In sum m ary,we have shown that antiprotons can becaptured athigh m agneticeld,transferred tolowereldwithout signicant loss and then used to m ake antihy-drogen,without further m anipulation ofthe antiprotoncloud.Thism ethod issuperiorto perform ing the wholeprocess atthe lowereld,and allowsfor a signicantlyhigherneutralwelldepth forfuture attem ptsatantihy-drogen trapping.This work was supported by CNPq,FINEP (Brazil),ISF (Israel),M EXT (Japan),FNU (Denm ark),NSERC,NRC (Canada),DO E,NSF (USA)and EPSRC (UK ).[1]Am orettiM ,etal.2002 Nature 419 456[2]M aury S 1997 Hyperne Interactions 109 43[3]G abrielse G ,etal.2002 Phys.Rev.Lett.89 213401[4]Am orettiM ,etal.2004 Phys.Lett.B 578 23[5]Bertsche W ,etal.2006 Nucl.Instr.M eth.Phys.Res.A566 746[6]Pritchard D E 1983 Phys.Rev.Lett.51 1336[7]O ’NeilT M 1980 Phys.Fluids 23 2216[8]FajansJ and Schm idtA 2004 NIM A 521 318[9]Fajans J, Bertsche W , Burke K , Chapm an S F andvan derW erfD P 2005 Phys.Rev.Lett.95 155001[10]Fajans J,Bertsche W ,Burke K ,D eutsch A,Chapm anS F,G om bero K ,van der W erfD P and W urtele J S2006Non-NeutralPlasm a PhysicsVI:W orkshop on Non-NeutralPlasm as vol862 ed D rewsen M ,UggerhojU andK nudsen H (M elville,N.Y.:AIP)p 176[11]G om bero K ,FajansJ,Friedm an A,G rote D P,CohenR H,Vay J L and W urteleJ 2007 Sim ulationsofplasm aconnem entin an antihydrogen trap,to be published inPhys.Plasm as[12]Andresen G ,etal.2007 Phys.Rev.Lett.98 023402[13]ChoiJ H,G uestJ R,PovilusA P,HansisE and RaithelG 2005 Phys.Rev.Lett.95 243001[14]G abrielse G ,Haarsm a L,Rolston S and K ells W 19885Phys.Lett.A 129 38[15]Jrgensen L V,etal.2005 Phys.Rev.Lett.95 025002[16]Am orettiM ,etal.2004 Phys.Lett.B 590 133[17]G abrielse G ,etal.2001 Phys.Lett.B 507 1[18]Am orettiM ,etal.2003 Phys.Rev.Lett.91 055001[19]Am orettiM ,etal.2004 Phys.Lett.B 583 59[20]Am orettiM ,etal.2006 Phys.Rev.Lett.97 213401[21]Huang X P,Anderegg F,Hollm ann E M ,D riscollC Fand O ’NeilT M 1997 Phys.Rev.Lett.78 875[22]Andresen G ,etal.2007 Sym patheticcom pression ofan-tiproton cloudsforantihydrogen trapping,subm itted toPhys.Rev.Lett.

Abstract We have demonstrated production of antihydrogen in a 1 T solenoidal magnetic field. This field strength is significantly smaller than that used in the first generation experiments ATHENA (3 T) and ATRAP (5 T). The motivation for using a smaller magnetic field is to facilitate trapping of antihydrogen atoms in a neutral atom trap surrounding the production region. We report the results of measurements with the Antihydrogen Laser PHysics Apparatus (ALPHA) device, which can capture and cool antiprotons at 3 T, and then mix the antiprotons with positrons at 1 T. We infer antihydrogen production from the time structure of antiproton annihilations during mixing, using mixing with heated positrons as the null experiment, as demonstrated in ATHENA. Implications for antihydrogen trapping are discussed. atoms were not confined; in fact, ATHENA detected the annihilation of the antiproton and positron in spatial and temporal coincidence to demonstrate antihydrogen production. The ATRAP collaboration reported a similar result, using an indirect detection technique based on field ionization [3], shortly thereafter. In both of the initial experiments, antihydrogen was produced by merging plasmas of antiprotons and positrons in liquid helium cooled Pennin

D P Van Der Werf

CiteSeerX

Production of antihydrogen at reduced magnetic field for anti-atom trapping.

Crossref

We have demonstrated production of antihydrogen in a 1 T solenoidal magnetic field. This field strength is significantly smaller than that used in the first generation experiments ATHENA (3 T) and ATRAP (5 T). The motivation for using a smaller magnetic field is to facilitate trapping of antihydrogen atoms in a neutral atom trap surrounding the production region. We report the results of measurements with the Antihydrogen Laser PHysics Apparatus (ALPHA) device, which can capture and cool antiprotons at 3 T, and then mix the antiprotons with positrons at 1 T. We infer antihydrogen production from the time structure of antiproton annihilations during mixing, using mixing with heated positrons as the null experiment, as demonstrated in ATHENA. Implications for antihydrogen trapping are discussed. © 2008 IOP Publishing Ltd

Andresen, G. B.

Bowe, P. D.

Cesar, C. L.

Fujiwara, M. C.

Gill, D. R.

Hangst, J. S.

Hayano, R. S.

Jenkins, M. J.

Jørgensen, L. V.

Page, R. D.

Silveira, D. M.

Storey, J. W.

Thompson, R. I.

Van Der Werf, D. P.

Wurtele, J. S.

The University of Manchester - Institutional Repository

http://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=502FB5E8D3368A7E549930B5B7CF37CA?doi=10.1.1.1052.7363&rep=rep1&type=pdf

Production of antihydrogen at reduced magnetic field for anti-atom
  trapping

Production of antihydrogen at reduced magnetic field for anti-atom trapping

Abstract

Similar works

Full text

Available Versions

Cronfa at Swansea University

CERN Document Server

CiteSeerX

Crossref

The University of Manchester - Institutional Repository

The University of Manchester - Institutional Repository