Gabrielse

Setting a Trap for Antimatter

Gerald Gabrielse, ATRAP Spokesperson (CERN)Leverett Professor of Physics, Harvard

2006

Science and science fiction

Warning: This Talk is Not About Science Fiction.

Gabrielse

Matter and Antimatter? Particle and Atoms of Matter and AntimatterAnnihilation ChallengesTraps: Containers Without WallsMaking Antimatter Atoms?Why Should We Do This?

Setting a Trap for Antimatter

Support fromNSF, AFOSR

Gabrielse

Where Did You Learn About Antimatter?

Antimatter annihilation powered Star Trek space ship “Enterprise”“going boldly where no one had gone before”

Dr. Spock “knew”

GabrielseGenerations of Trekies

We study antimatter. How close are we to the Star Trek imagination?

hardware: android software: hologram

GabrielseThe Science Reality

Behind the Science Fiction Imagination

What is Matter?

What is Antimatter?

GabrielseWe Are Made of Matter

GabrielseParticles of Matter and Antimatter:

Opposite and Identicalcharge mass

Only measurements tell how identical

Gabrielse

Matter and Antimatter Atoms

Particle and antiparticle charges are opposite

Both atoms are uncharged same charge

unchargedatom

unchargedanti-atom

Gabrielse

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According to Physics as We Understand ItLooks Like the Whole Universe

Could Have Been Made of Antimatter

How would an antimatter universe be different?

Why is our universe made of matter rather than antimatter?

Gabrielse

What Would I Look LikeIf I Were Made of Antimatter?

• protons antiprotons• neutrons antineutrons• electrons anti-electrons (positrons)

?Less mass?

Handsome?

More intelligent?

Gabrielse

Big disappointment:• Antimatter Gabrielse looks the same!• Antimatter Gabrielse has the same mass!• Antimatter Gabrielse has the same limited brain power!

AntimatterGabrielse

What Would I Look LikeIf I Were Made of Antimatter?

• protons antiprotons• neutron antineutrons• electrons anti-electrons (positrons)

Gabrielse

Universe Made of Antimatter

• Essentially the same as a universe made of matter

• We only know two ways for inhabitants to know whether theylive in a universe made of matter or antimatter

(Need a large accelerator complex and sophisticated techniques)

Why is our universemade of matter?

(seems like antimatter would work just as well)

Gabrielse

Gabrielse

Why Are Science Fiction Writersso Fascinated?

GabrielseAntimatter and Matter ParticlesAnnihilate Each Other

Gabrielse

What Happens When

Anti-Gabrielse Gabrielse

Antimatter and Matter Gabrielse Meet?

About to shake hands

GabrielseHuge Energy Release!

2E mc=

energyreleased

mass thatdisappears 200 kg

Einstein’s famous formula

100 kgAnti-Gabrielse

100 kgGabrielse

5,000,000,000,000 kilowatt-hoursYearly output of 500 nuclear power plantsEnergy from 4200 Megatons of TNT

Gabrielse

Efficiency

Annihilation 100 %

Nuclear fission 0.1 %Nuclear fusion 0.1 % (or a bit higher)

Chemical fuel 0.000 000 3 %

Annihilation• 1000 times more bang for the gram

compared to nuclear fuel

Energy Released= Mass of Fuel Used

Energy Source of the Future? No, certainly notAntimatter Weapons? No, certainly notAntimatter Rockets? Doubtful, … maybe in

distant future

GabrielseAntiproton Trapping and Annihilation Makes its Way Into Popular Culture

Serious Play: HapgoodAuthor: Tom Stoppard

Fiction best seller

Star Trek – antimatter powers the space ship Enterprise

Gabrielse

Should the Pope Have Worried?

Missing detail: if all the antiprotons we have madein the history of the world were annihilatedat the same time

Not enough energy to boil a pot of tea

Clearly the pope should havestudied more science

Gabrielse

Gabrielse

Embarrassing, Unsolved Mystery:How did our Matter Universe

Survive Cooling After the Big Bang?

Big bang equal amounts of matter and antimattercreated during hot time

As universe cools antimatter and matter annihilate

Big Questions:

• How did any matter survive?

• How is it that we exist?

Our experiments are looking for evidence of any way that antiparticles and particles may differ

Gabrielse

Our “Explanations” are Not so Satisfactory (My opinion)

Baryon-Antibaryon Asymmetry in Universe is Not UnderstoodStandard Explanation• CP violation• Violation of baryon number• Thermodynamic non-equilibrium

Alternate• CPT violation• Violation of baryon number• Thermo. equilib.Bertolami, Colladay, Kostelecky, PottingPhys. Lett. B 395, 178 (1997)

Why did a universe made of matter survive the big bang?Makes sense look for answers to such fundamental questions

in the few places that we can hope to do so very precisely.

Bigger problem: don’t understand dark energy within 120 orders of magnitude

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Gabrielse

Low Energy Studies of Antimatter

CERN Laboratory (Geneva) makes it

We slow it, catch it, cool it, study it

Need a container without walls to avoid annihilation

trap

Starthere

Gabrielse

Particle Trap – A “Container Without Walls”

Horseshoe Magnet

- - -

- - -

negativeantiproton

Need two truths to understand particle trap1. Charged particles go in circles near a magnet2. Same sign charges repel

Gabrielse

ATRAP – Trap and Detectors

fibers77 K

BGO77 K

antiprotons

positronsource

positron traps

antiproton traps

rotating electrode

5.3 Teslamagnetic

field

4.2 K

Harvard: Trap, vacuum, rf electronicsJuelich: Scintillation detectors Garching, York, Mainz: Lasers

Small View

Gabrielse

(Harvard)

Approx.100 leads(Photo by P. Horowitz)

Penning Trap

Rotating• 4 K, 6 Tesla• electrode• single crystal• field emissionpoint

1 cm

Gabrielse

Gabrielse

One Charged Particle in a TrapOne electron more than 10 months One antiproton several months

Can study the particle properties with extremely high precision

Antiproton and proton have the same charge-to-mass ratioto better than 1 part in 1010 = 10000000000Measure the electron magnetic moment to better than 1 part in 1012 = 1000000000000

Gives a new value for the fine structure constant αthat is much more accurate

Gabrielse

One-Antiproton Radio

Tuning

FM Radio

Speaker

Antenna

frequency tuning

“volume”

So far, the most stringent CPT test with baryons comes from

GabrielseSpecial Relativity Is Crucial year of EinsteinPlan: Compare cyclotron frequency for antiproton and proton

compares Q/M for antiproton and proton (if B stays same)test of CPT invariance for baryon/antibaryon system

Problem: Antiproton cyclotron frequency shifts in time

cQ BM

ω =

cQ BM

ωγ

=

21

111

1.000000001

KMceVGeV

γ = +

= +

=

Highly non-relativistic antiproton

Actually, highly “relativistic” at 1 eV due to high resolution

Extrapolate Einstein awayK 0 eV

Gabrielse

Polarization Effect Discovered with Molecular IonsJ.K. Thompson, S. Rainville and D.E. Pritchard, Nature Lett. 430, 58 (2004)

Motional radial electric field: E = vBpolarizes the ion radially: d = αE = -αvB

Ion experiences • magnetic force on its charge: -evB• additional force on it dipole moment: -dωΒ

The additional polarization force could be expected to vanishas we take the v 0 limit in our experiment

But, it does not. Instead2

70 pptc

c

BM

ω αω∆

= − =

not really statistically significant(an excuse to measure more accurately?)

corrected

Gabrielse

year

1960 1970 1980 1990 2000

fracti

onal

accu

racy

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

CERNBNL

ppb

0

1

2

TRAP I

(a) (b)Bevatron (p discovery)

TRAP II

Trap II

TRAP III

TRAP III

(exoticatoms)

TRAP Improved the Comparison of Antiproton and Proton by ~106

G. Gabrielse, A. Khabbaz, D.S. Hall, C. Heimann, H. Kalinowsky, W. Jhe;Phys. Rev. Lett. 82, 3198 (1999).

100antiprotonsand protons

/ (antiproton) 0.99999999991(9)/ (proton)

q mq m

= −119 10 90ppt−× =

56 10×

best CPT test with baryons

Gabrielse

Last TRAP Measurement of Antiproton Q/M

improvedapparatus

and technique

Low Energy Antiproton Ring(LEAR) shut down

Could do significantly better!

Gabrielse

could q and m change to keep q/m constant?

TRAP: Directly compare q/m for antiproton and protonASACUSA: Indirect measure of q2m for antiproton

- antiprotonic He spectroscopy - and detailed structure calculations- measured Rydberg constant, etc.

Comparisons of Antiproton and ProtonTRAP: q/m same to fractional accuracy 0.000 000 000 09

ASACUSA: q2m same to fractional accuracy 0.000 000 06Together: q and m same to fractional accuracy 0.000 000 06

q/m comparison is 700 times more accurate

Q/M much more accurate than Q and M separately

Given that q/m magnitudes are the same,

Gabrielse

GabrielseDigression: Quantum Limit

of a Particle in a Trap

0.1 µm

2ψ

Student award symposium: Brian Odom, Thursday, 2 pm

One ElectronQuantum Cyclotron

GabrielseQuantum Cyclotron

1 5 0 G H zcυ ≈

Tesla6B ≈

one electron quantum

average quantum number < 1, etc. quantum

n = 0n = 1n = 2n = 3n = 4

7.2 kelvincω =

To realize a quantum cyclotron: • need cyclotron temperature << 7.2 kelvin• need sensitivity to detect a one quantum excitation

Gabrielse

Cylindrical Penning Trap

Electrostatic quadrupole potential good enough near trap center

Gabrielse

Quantum Jumps as a Function of Temperature• one electron• Fock states of a cyclotron oscillators• due to blackbody photons

0.23

0.11

0.03

9 x 10-39

On a short time scalein one Fock state or another

Averaged over hoursin a thermal state

average numberof blackbody

photons in the cavity

Gabrielse

Quantum Jump Spectroscopy

• lowest cyclotron and spin states• one electron in a Penning trap

GabrielseA New Measurement

of the Electron Magnetic Moment

BSgµ µ=magnetic

momentspin

Bohr magneton2em

• First improved measurement since 1987• Nearly six times improved accuracy• Likely more accuracy coming

13

/ 2 1.001 159 652 180 850.000 000 000 000 76 7.6 10

g−

=

± ×

Gabrielse

New Determination of the Fine Structure Constant

2

0

14

ec

απε

=• Strength of the electromagnetic interaction• Important component of our system of

fundamental constants

1

10

137.035 999 7100.000 000 096 7.0 10

α −

−

=

± ×

• First improved measurementsince 1987

• Ten times more accurate thanatom-recoil methods

• Component of new mass standard

Gabrielse

Digressionto Illustrate Quantum Limit

of One Particle in a Trap

is over

Gabrielse

Gabrielse

Antihydrogen Offers a More Stringent Probethan Q/M of Antiproton and Proton

CPT Testby comparing

Q/M of antiproton and proton

CPT Testby comparing

laser spectroscopy of antihydrogen and hydrogen

9 x 10-11 much more accurate

Old Long Term Goal New Long Term Goal

Gabrielse

Motivations and Goals

Clear, Stable, Long Term

• Clear before the AD was built• Clear while the AD rested for 1.5 years• Clear now• Clear in the future

Highly accurate spectroscopic comparisons of antihydrogen atoms and hydrogen atoms

Extremely accurate CPT testsGravitational studies

Gabrielse

Comparing the CPT TestsWarning – without CPT violation models it is hard to compare

19 x 10-119 x 10-11P Pbaryons

1032 x 10-92 x 10-12e+ e-

Leptons

10152 x 10-32 x 10-18K0 K0

Mesons

FreeGift

MeasurementAccuracy

CPT TestAccuracy

_

_

improve withantihydrogen

3 fu

ndam

enta

lly d

iffer

ent t

ypes

of p

artic

les

Gabrielse

Seek to Improve Lepton and Baryon CPT Tests

ATRAP members

2 2[ ] [[H] 1 /[ ] [ ] [

[H]]

[ ] [ ] []

] [1[ /] ]qm e q e m ep M pq p Mm e q e m pe

RR

+ + −

∞− +

∞−

+= +

Gabrielse

Why Cold Antihydrogen?

Goal: Highly Accurate Comparison – Antihydrogen and Hydrogen

No Hope with Hot Antihydrogen • too fast v ~ c• little measurement time• too few atoms

1995 – CERN1997 -- Fermilab

GabrielseHydrogen 1s – 2s Spectroscopy

(Haensch, et al., Max Planck Soc., Garching)http://www.mpq.mpg.de/~haensch/hydrogen/h.html

Many fewer antihydrogen atoms will likely be available

Gabrielse

Not as Accurate Yet, but Similar Environment

Still uses a lot more hydrogen atoms than we expect to have antihydrogen atoms

Gabrielse

Spectroscopy on 1000 or Fewer AtomsSeems Possible 1 part in 1012 estimated

T. Haensch and C. Zimmerman,Laser Spectroscopy of Hydrogen and Antihydrogen,Hyper. Int. 76, 47 (1993).

Gabrielse

Gravity and Antihydrogen

Gabrielse

Gabrielse

Accumulating Many Antiprotons in a Trap

• Slow antiprotons in matter• Capture antiprotons in flight• Electron cooling 4.2 K• 5 x 10-17 Torr

Basic Ideas and TechniquesDeveloped by Our TRAP Collaboration

at CERN’s LEAR: 1986 - 2000)

Used by 3 collaborations at the CERN ADATRAP, ATHENA and ASACUSA

Gabrielse

We Go to CERN

France

Switzerland (Geneva)

Makes matter and antimatter particles

skiing

Gabrielse

Harvard UniversityProf. G. Gabrielse Dr. T. Roach J. Estrada A. Speck(Spokesperson) Dr. J.N. Tan P. Yesley D. Lesage

Dr. C. Storry P. Oxley P. LarochelleDr. J. Tan N. BowdenDr. B. Levitt M. Wessels

Juelich LaboratoryDr. W. Oelert Dr. T. Sefzick Z. Zhang

Dr. G. SchepersDr. D. Grzonka

Max Planck Institute for Quantum OpticsProf. T. Haensch Dr. J. Walz H. Pittner

M. Herrmann

York UniversityProf. E. Hessels D. ComeauProf. C. Storry

University of MainzProf. J. Walz

ATRAP

Earlier contributions from Bonn and Vienna

GabrielseFor a low energy, laboratory physicistgoing to a particle physics lab was an adventure

1981 ventured to Fermilab as a postdoconly one person was interested “Tev or bust”

1986 go to CERN (still essentially a postdoc)get thrown out of first officeget 24 hours of antiproton beam to demonstrate slowingget 24 hours to demonstrate trapping

Amazingly, this worked CERN extended more hospitality(postdoc professor)

Continuing challenge: the way that we must invent our way throughour experiments is very different from the highlyscheduled modern particle experiments

still not well understood by committees, etc.

Gabrielse

Antiproton Capture – the Movie

z position

Axia

l Ene

rgy

z position

r pos

ition

p

p

pp

"First Capture of Antiprotons in a Penning Trap: A KeV Source",G. Gabrielse, X. Fei, K. Helmerson, S.L. Rolston, R. Tjoelker, T.A. Trainor, H. Kalinowsky, J. Haas, and W. Kells; Phys. Rev. Lett. 57, 2504 (1986).

Gabrielse

z position

Axia

l Ene

rgy

Electron-Cooling of Antiprotons – in a Trap

p

p

e-

• Antiprotons cool via collisions with electrons • Electrons radiate away excess energy

"Cooling and Slowing of Trapped Antiprotons Below 100 meV",G. Gabrielse, X. Fei, L.A. Orozco, R. Tjoelker, J. Haas, H. Kalinowsky, T.A. Trainor, W. Kells; Phys. Rev. Lett. 63, 1360 (1989).

Gabrielse

1981 – 1985 Proposals- Fermilab- CERN

1986 Slow antiprotons in matter21 MeV 3 keV

1986 First trapping of antiprotons< 300 < 3 keV ~10 minutes

1989 Hold 105 antiprotons for 2 monthslifetime > 3.4 monthspressure < 5 x 10-17 Torr

1989 First electron cooling in trap3 keV 0.3 meV (4.2 K)

1990 First antiproton stacking in trap

1990 q/m of antiproton and proton same to 4 x 10-8

1992 First observation of one trapped antiproton

1995 q/m of antiproton and proton same to 1 x 10-9

1999 q/m of antiproton and proton same to 9 x 10-11

106-fold improvement overall other techniques

First antiproton trap

Antiproton Years: TRAP at CERN’s LEAR

antiprotons

Gabrielse

• Phys. Rev. Lett. 57, 2504 (1986).

• Phys. Lett. A 129, 38 (1988)

• Phys. Rev. Lett. 63, 1360 (1989).

• Phys. Rev. A (Rapid Comm.) 40, 481 (1989).

• Phys. Rev. Lett. 65, 1317 (1990).

• Sci. Am., Dec. , pp. 78 – 89 (1992).

• Phys. Rev. Lett. 75, 806 (1995).

• Phys. Rev. Lett. 74, 3544 (1995).

• Phys. Rev. Lett. 77, 806 (1996).

• Phys. Rev. Lett. 82, 3198 (1999).

• Phys. Lett. B 455, 311 (1999).

• Phys. Rev. Lett. (14 Feb. 2000).

Key TRAP Publications

First trapping of antiprotons

4.2 K antiprotons and positronsinteracting (preparing for antihydrogen)

Gabrielse

LEAR – Low Energy Antiproton Ring (at CERN)

Built to slowly spill antiprotonsmeson spectroscopy and CP studies

we persuaded CERN to give us antiprotonpulses instead

GabrielseLEAR – Low Energy Antiproton Ring

AC – catch antiprotonsAA – stack antiprotons, coolLEAR – decelerate antiprotons

We got 109 antiprotons in a pulse every 5 minutes(maximum, need refill time)

Gabrielse

CERN – the Largest and Smallest Accelerators

70 mK, lowest storage energyfor any charged particles

2p2M c

LEAR and AD

TRAP

1010

4.2 K0.3 meV

Gabrielse

Accumulating Antiprotons – just a matter of time

ATRAP’s good vacuum < 5 x 10-17 Torrallows such stacking

(ATHENA and ASACUSAuse stacking but with lessbunches)

“Stacking”

Can stack this numberin a single well, for moreneed multiple wells

First Demonstration – Antiprotons Stacked in a TrapG. Gabrielse, X. Fei, L.A. Orozco, R. Tjoelker, J. Haas, H. Kalinowsky, T.A. Trainor, W. KellsPhys. Rev. Lett. 63, 1360 (1989)

“Stacking of Cold Antiprotons”ATRAPPhys. Lett. B 548, 140 (2002)

Gabrielse

Gabrielse

Making Atoms Entirely of Antimatter

Antihydrogen atoms

Gabrielse

Cold Antihydrogen Aspirations Announced Long Ago

“For me, the most attractive way ... would be to capture the antihydrogen in a neutral particle trap ... The objective would be to then study the properties of a small number of [antihydrogen] atoms confined in the neutral trap for a long time.”

Gerald Gabrielse, 1986 Erice Lecture (shortly after first pbartrapping) In Fundamental Symmetries, (P.Bloch, P. Paulopoulos, and

R. Klapisch, Eds.) p. 59, Plenum, New York (1987).

Goals• Produce cold antihydrogen• Trap cold antihydrogen• Use accurate laser spectroscopy to compare

antihydrogen and hydrogen

4.2K

Gabrielse

Meanwhile: Very Fast Antihydrogen Atoms

First at CERN in Geneva, Switzerland"Production of Antihydrogen" G.Baur et al. (team led by W. Oelert) Phys.Lett. B 368 (1996) 251-258.

Then at Fermilab in the USA"Observation of Antihydrogen" G. Blanford, et al. Phys. Rev. Lett. 80, 3037 (1998).

Demonstrated the existence of antihydrogen atoms.

Need slow antihydrogen for precise study

too few atoms

atoms go too fastcannot make accurate comparisonsof antihydrogen and hydrogen

Gabrielse

1. In a nested Penning trap, during positron cooling of antiprotons

Device and technique – TRAP and ATRAP (1986 – 2001) Used to produce slow antihydrogen – ATHENA and ATRAP

(2002)

2. Laser-controlled resonant charge exchange

Developed the technique – Harvard and York (2001-2003)ATRAP (2004)Only a few atoms made so far – proof-of-principle

Now: Two Ways to Produce Slow Antihydrogen

Two Ways That Do Not (Yet) Produce Slow Antihydrogen1. Field-assisted formation – ATRAP (2002)2. Laser stimulated formation with CO2 laser – ATHENA (2004)

GabrielseMethod 1: Nested Penning Trap3-Body “Recombination”

Nested Penning Trap 3-Body “Recombination”

Gabrielse

e+

p

Method 1: Positron Cooling of Antiprotonsin a Nested Penning Trap

TRAP/ATRAP Develops the Nested Penning TrapProposed nested trap as a way to make antihydrogen"Antihydrogen Production Using Trapped Plasmas"G. Gabrielse, L. Haarsma, S. Rolston and W. KellsPhysics Letters A 129, 38 (1988)

"Electron-Cooling of Protons in a Nested Penning Trap"D.S. Hall, G. GabrielsePhys. Rev. Lett. 77, 1962 (1996)

"First Positron Cooling of Antiprotons"ATRAPPhys. Lett. B 507, 1 (2001)

Cold antihydrogen wasmade in 2001 not cleanly detected

Gabrielse

One Production Method– Two Detection Techniques

2001: ATRAP, "First Positron Cooling of Antiprotons"Phys. Lett. B 507, 1 (2001)

Crucial Device: Nested Penning TrapCrucial Technique: Positron Cooling of Antiprotons

Cold trapped positrons cool antiprotons to a low relativevelocity with the positrons produces slow antihydrogen

2002: ATHENA and ATRAP demonstrated that antihydrogenwas produced by this device and techniqueATHENA, Nature 419, 456 (2002)

ATRAP, Phys. Rev. Lett. 89, 213401 (2002)ATRAP, Phys. Rev. Lett. 89, 233401 (2002)

same productiondifferent detection

Gabrielse

Comparing the Two Detection MethodsAthena – detects positron and antiproton annihilations within

5 microseconds and +/- 8 mm of each other(now using mostly antiproton annihilations, 4 mm resolution)

Good: Detects antihydrogen whatever is velocity and stateNot as good: Insensitive to antihydrogen velocity and state

ATRAP – field ionization detection

Good: No backgroundProbes internal state of the antihydrogenCan measure antihydrogen velocity

Not as good: Can only detect states that can be field ionized(Hope to use lasers to excite lower states to statesthat can be field ionized)

GabrielseATRAP’s Field Ionization Method

• Use Field-Ionization – strip positron and store antiproton

p

e+H

p

e+

• Dump stripping well after experiment– Dump other particles before looking in stripping well– Ramp quickly compared to cosmic background count rate (ramp

in 20ms, get one cosmic/second)– Essentially no background for this measurement!

GabrielseOnly Detect Ionized Antihydrogen

• Field-Ionization is very robust – only antihydrogen can get antiprotons into the stripping well

p

e+

p

• Antiprotons knocked out of well leave to the left

• Even if an antiproton has enough energy to get to the ionization well, it can not get into the well

Gabrielse

pe+

Driven Antihydrogen Production Higher Rate• Recall that antiprotons cool below the positrons –

interaction stops• Drive axial motion of antiprotons repeatedly to “drive”

interaction

• Antihydrogen production rate is increased by more than an order of magnitude using this method

Gabrielse

No Useful Antihydrogen Yet,But We Have Methods to Measure and Optimize

ATRAP’s field ionization method is only probe so farHow close to the ground state?

How cold?Vary ionization field F in time to find out.

• Fast atoms make it through while field is at a low value.• Slow atoms never avoid ionization

F ~ Cos(ωt)

Gabrielse

Observed Antihydrogen Atoms are Very Weakly Bound

Breakdown of the GCA picture chaotic motion?

GabrielseSimulation of Field Ionization Spectrum

GCA, beforecharge exchange

GCA, after charge exchange

GCA

ATRAP Measurement

Full simulation

T. Pohl, H. R. Sadeghpour and G. GabrielseTalk here: Pohl

Gabrielse

First Measurement of an Antihydrogen Velocity

200 meV

• This is for the most weakly bound antihydrogen states• More deeply bound states may be going more slowly

20thermal

vv

∼

ATRAP, "First Measurement of the Velocity of Slow Antihydrogen Atoms", Phys. Rev. Lett. 93, 073401 (2004).

Gabrielse

More Favorable InterpretationCharge exchange of antihydrogen with faster protons

T. Pohl, H. R. Sadeghpour and G. GabrielseTalk here: Pohl

Gabrielse

Great Features of Method I

• High antihydrogen production rate• Easy and robust

Not-so-Great (so Far)

• Highly excited antihydrogen is produced• Detected antihydrogen has velocity much higher

average for 4.2 K• Variations from production attempt to production attempt is

larger than we understand (something not under control)

Conclusion: Need larger trap and more positronsMore collisional deexcitationMore collisional coolingMore stability in the production process (away from trap walls)

(big mystery!)

Gabrielse

Observe Rydberg Cs and Rydberg Positronium (at Harvard)

Observe Antihydrogen n~37 (at CERN)State-selected antihydrogen, should be very coldhope to de-excite with a laser (not easy) or collisions

First Laser-Controlled Antihydrogen ProductionUse positronium – Deutch, …Use Rydberg positronium – Charlton, …Use charge exchange to produce the positronium – Hessels, …

Calculation (no B field): E.A. Hessels, D.M. Homan, M.J. Cavagnero, Phys. Rev. A 57, 1668 (1998).

Very Different Method II to Produce Slow Antihydrogen

Gabrielse

Antihydrogen Via Laser-Controlled Resonant Charge Exchange

852 nm

510.6 nm

Gabrielse

Great Features of Method II

• Lasers control the state of the antihydrogen produced• Likely the first truly cold antihydrogen

Not-so-Great (so Far)

• Highly excited antihydrogen is produced• Detection rate is very low (production rate is much better)

Conclusion: Need larger trap and more positronsMore detectable antihydrogen to work with

Gabrielse

Current “Do or Die” Challenges(no change since Villars)

1. Deexcite the highly excited antihydrogen that is produced.2. Need slower antihydrogen produced (in method I)3. Add field gradients of a magnet trap for antihydrogen

without destroying the antihydrogen production rate

Larger traps with more positrons and antiprotonsRoom for magnetic gradient trapsRoom for laser access

We believe that a solution requires

Gabrielse

Gabrielse

ATRAP II – Completely New

Much Bigger room for bigger trap, more particles, more coolingroom for magnetic traproom for more laser accessroom for annihilation imaging

New Beam Steering, New Soleniod, New Dewars, New Detectors, New Electronics, New Positron Source, …

What to do when CERN shuts us down for a year and one half, and delivers less antiproton beam during the first year back?

Build a completely new apparatus based upon what we have learned at the AD

Will we be ready? We still hope so, but this will be a verybusy beam run.

Gabrielse

Harvard UniversityProf. G. Gabrielse Dr. B. Levitt D. Le Sage(Spokesperson) Dr. I. Kuljanishvili P. Larochelle

Dr. J. Wrubel W. Kolthamme

Juelich LaboratoryDr. W. Oelert Dr. D. Grzonka Z. Zhang

Dr. F. GoldenbaumDr. T. Sefzick

York UniversityProf. E. Hessels M. George D. ComeauProf. C. Storry M. Weel A. Carew

University of MainzProf.. J. Walz F. Markert

Rowland Institute at HarvardDr. A. Speck

Free Univesity of AmsterdamProf. E. Eikema

Max Planck Institute for Quantum OpticsProf. T. Haensch

ATRAP 2006

GabrielseComparing ATRAP I to ATRAP II

Gabrielse

Some ATRAP Members at a Recent MeetingHarvard, 13 January 2006

Missing: Some ATRAP members from Juelich, Rowland, Mainz, Amsterdam

Gabrielse

Different Configurations Envisioned for ATRAP II

Gabrielse

Connection to the AD

AD antiprotons

ATRAP IISolenoid

AD Team is correcting for the fringing field

Gabrielse

Location of Positron Source for ATRAP II

ATRAP IISolenoidand Traps

positron source(locally shielded)

low energylow flux

positron guide

ATRAP I

could be a fence, if this is more convenient than concrete

rear entrance A new sodiumsource shouldarrive soon.

Will it???

Gabrielse

Coming

Gabrielse

A Trap for Antimatter Atoms

Atom with a properly alligned magnetic momentwill be trapped in a minimum of magnetic field

Gabrielse

Conclusions

Gabrielse

Where We Are, and Where We are Going

A lot has been accomplished• We can regularly cool antimatter particles to extremely

low energies• We can readily make many antihydrogen atoms

Much remains to be done• Need to make antihydrogen atoms in their ground state• Need to slow the antihydrogen atoms even more to trap them(some may be cold enough)

Goal• Use lasers to probe for any tiny differences between

atoms of antimatter and matter

Gabrielse

Why Study Antimatter?Solve energy shortage problem, make weapons, make rockets

Look closely for any tiny differences between antimatter and matter• Test basic theories that suggest that matter and antimatter

are opposite in charge, but identical in mass, …• Probing reality at its most fundamental level

Such fundamental experiments typically lead to new technologiese.g. Transistor, Laser, World Wide Web (CERN)e.g. From our experiments so far

• new cell designs for ion cyclotron resonance imaging of pharmaceuticals

• self-shielding solenoid used for NMR and MRI imaging• first continuous Lyman alpha radiation

Gabrielse

If Antimatter Atoms Interest You

Gabrielse

Antihydrogen Review Paper"Atoms Made Entirely of Antimatter: Two Methods Produce Slow Antihydrogen"G. GabrielseAdvances in Atomic, Molecular and Optical Physics 50 (2004).

Simpler Discussions“Extremely Cold Antiprotons"G. GabrielseScientific American 50 (1986)

“Making Cold Antimatter”G.P. CollinsScientific American (June, 2005)