ASACUSA Experiment at CERN’sASACUSA Experiment at CERN’sAntiproton DeceleratorAntiproton Decelerator

Atomic Spectroscopy AndAtomic Spectroscopy AndCollisions Using SlowCollisions Using Slow

AntiprotonsAntiprotons

LEAP 2000 ConferenceLEAP 2000 ConferenceVenezia, ItalyVenezia, ItalyAugust 2000August 2000

M. Hori CERNM. Hori CERN

Institute of Applied Physics, Tsukuba University, Azuma, T

Institute of Physics, University of Tokyo, Franzén K Y Higaki, H Hyodo, T Ichioka, T Komaki, K,

Kuga, T Kuroda, N Kuroki, K Torii, H, A. Yamazaki, Y

Research Institute for Particle and Nuclear Physics, Bakos, J, S. Horváth, D Juhasz, B Ujvari, B

Institute of Physics and Astronomy, University of Aarhus, Bluhme, H Knudsen, H Merrison, J Uggerhöj, U

Thompson, R

Department of Physics, University of Wales Swansea, Charlton, M

Institut fur Kernphysik, Dörner, R Schmidt-Böcking, H

CERN, Eades, J Ketzer, B Hori, M

Department of Physics, University of Tokyo, Fujiwara, M Funakoshi, R Hayano, R, S. Ishikawa, T Sakaguchi, J Suzuki, K Yamaguchi, H Widmann, E

KVI, Hoekstra, R

Department of Physics, Tokyo Institute of Technology, Iwasaki, M

RIKEN, Kambara, T Kojima, T Nakai, Y Oshima, N Mohri, A Wada, M Yamazaki, T

Institute for Molecular Science, Kumakura, M Morita,M

Institute for Storage Ring Facilities, University of Aarhus, Möller, S P Uggerhöj, E

Ciril -Lab. Mixte CEA-CNRS, Rothard, H.

GSI, Scheidenberger, C

Universität Freiburg, Ullrich, J

Department of Experimental Physics, St. Patrick's College, Slevin, J. A.

Department of Physics, Tokyo Metropolitan University, Tanuma, H.

3

Physics GoalsPhysics Goals• High precision spectroscopy of metastable antiprotonic atoms.

– Bound-state QED– CPT theorem– high-precision 3-body theories– Atomic cascade– Chemical-physics

• Atomic collisions at very low energies– Stopping power– Ionization– Channeling– Antiprotonic atom formation

4

Metastable antiprotonic helium atomsMetastable antiprotonic helium atoms

HeHe2+2+

ee--

ee--

p

T < 25 eVT < 25 eV

HeHe2+2+pee--

ee--

• 3% metastable fraction3% metastable fraction• Large (n, l) states (=40) are Large (n, l) states (=40) are

metastable in even densemetastable in even dense hhelium,elium, 1 1 mms s lifetimes. lifetimes. – Auger decayAuger decay suppressed suppressed– Stark mixingStark mixing suppressed suppressed

38*

0 em

Mn

Cerenkov counterCerenkov counter

Laser pulse

Metastable atoms

Metastable atoms 3% with τ=3 ～ 4μ ｓ

Laser spikeLaser spike

Prompt annihilation

GatingGating

AD Antiproton pulse 2X107 particles T=5.3 MeV 300-600 ns long 4-5 mm diameter

Theory and experiment agree at the 1000 ppm level....

1993-19941993-1994Laser -induced Laser -induced

annihilationannihilationexperimentsexperiments

at LEARat LEAR

N. Morita et.al.N. Morita et.al.

Systematic studies of transition energiesSystematic studies of transition energies

RelativisticRelativistic(Korobov 1996)(Korobov 1996)

non-relativisticnon-relativistic(Korobov 1995)(Korobov 1995)

Theory and experiment agree at the ppm level....

T.Yamazaki, R.S.Hayano, N.Morita, T.Yamazaki, R.S.Hayano, N.Morita, E.Widmann, J.Eades et.al.E.Widmann, J.Eades et.al.

Experimental accuracy forExperimental accuracy forlaser spectroscopy 0.5 ppmlaser spectroscopy 0.5 ppm

After Lamb shift corrections,After Lamb shift corrections,experiment-theory agreement at 2 ppmexperiment-theory agreement at 2 ppm

M

Q

2QM

Cyclotron frequencyCyclotron frequency <10 <10-9 -9 precisionprecisionTRAP / ATRAPTRAP / ATRAP

Rydberg constantRydberg constant5X105X10-7 -7 precisionprecision

Antiprotonic heliumAntiprotonic helium

H.A. Torii et.al.H.A. Torii et.al.

9

• improved laser system• better absolute calibration

• pulse-amplified CW laser• collision-free environment

Proton mass in eV/c2

R.S.Hayano et.al.R.S.Hayano et.al.

10

Experiments continued at the AD….Experiments continued at the AD….

11

597-nm resonance reacquired at AD597-nm resonance reacquired at AD(Dec 2, 1999)(Dec 2, 1999)

High-precision measurement of the resonance linesHigh-precision measurement of the resonance lines

Target density (g/liters)

KorobovTorii

0 2 4 6 8

This work

Factor 2-3 improvement over LEAR Factor 2-3 improvement over LEAR experimentsexperimentsHigh precision achieved using High precision achieved using pulsed antiproton beamspulsed antiproton beams

Measurement of deeply-bound UV (372-nm) resonanceMeasurement of deeply-bound UV (372-nm) resonance

•(35,33)->(34,32) at 372-nm detected.(35,33)->(34,32) at 372-nm detected.

Shows atoms formed in narrow band Shows atoms formed in narrow band

between n=37-40….between n=37-40….

Annihilation timeAnnihilation time

(n,l)=(37,34)

(n,l)=(35,33)

Hyperfine structure of metastable antiprotonic helium atom resolved.

Fast extraction at LEAR...Fast extraction at LEAR...

and at AD…..and at AD…..

•Improved pulse-to-pulse intensity and position stability.

•Improved laser bandwidth and stability.

•(n,l)=(37,35)->(38,33) at 726 nm.

15

Measurement of hyperfine structureMeasurement of hyperfine structure

• Hyperfine structure (4-levels)Hyperfine structure (4-levels)– Antiproton orbital angular momentumAntiproton orbital angular momentum

– Electron spinElectron spin

– Antiproton spinAntiproton spin

• High precision using High precision using laser/microwave triple resonancelaser/microwave triple resonance– Determine antiproton magnetic Determine antiproton magnetic

momentmoment

Bakalov, V.I. Korobov, Bakalov, V.I. Korobov, E. WidmannE. Widmann

16

Microwave resonator systemMicrowave resonator system

f=13 GHz transition frequency.

Field strength 10 gauss

Input power 100 W.

E.Widmann, J.Sakaguchi, T.Ishikawa et.al.E.Widmann, J.Sakaguchi, T.Ishikawa et.al.

How to go to higher precision with transition energy?How to go to higher precision with transition energy?

Various factors that limit experimental accuracy to 0.5 ppmVarious factors that limit experimental accuracy to 0.5 ppm

• Bandwidth of the pulsed laser Bandwidth of the pulsed laser 1.2 GHz (0.6 GHz at AD, better diagnostics)1.2 GHz (0.6 GHz at AD, better diagnostics)

• Collision-induced shift Collision-induced shift ～～ 1 GHz1 GHz

• Collision-induced broadening Collision-induced broadening <0.5 GHz<0.5 GHz

• Doppler broadening Doppler broadening 0.5 GHz0.5 GHz

　　 Additional factors that will limit future high-precision experiments:Additional factors that will limit future high-precision experiments:

• AC Stark effect AC Stark effect <50 MHz<50 MHz

• Natural width Natural width 0.10.1 ～～ 50 MHz50 MHz

• Laser phase-modulation Laser phase-modulation <50 MHz<50 MHz

• Systematics of antiproton beam Systematics of antiproton beam large! -> but understood at AD (higher intensity)large! -> but understood at AD (higher intensity)

The goal is to measure the transitions withThe goal is to measure the transitions with an accuracy better thanan accuracy better than 50 ppb.50 ppb.

Ultimate-precision experiment

• Cancellation of first-order Doppler width with 392.42-nm laser• Natural linewidth of transition 0.3 MHz• Depletion of (n,l)=(34,33) and signal detection, using 457.65-nm dye-laser.• Ultimate measurement precision <10 MHz

IntermediateIntermediatevirtual statevirtual state

392.42 nm392.42 nm

392.42 nm392.42 nm

Auger decayAuger decay

(n,l)=(36,35)→(34,33)(n,l)=(36,35)→(34,33) (34,33)→(35,32)(34,33)→(35,32)

HeHe2+2+

p ee--392.42 nm392.42 nm 392.42 nm392.42 nm

19

Radio-frequency Post-deceleratorRadio-frequency Post-deceleratorDeveloped by CERN PS divisionDeveloped by CERN PS division

• Decelerate antiprotons from 5.3 MeV to~ 20 keVDecelerate antiprotons from 5.3 MeV to~ 20 keV– Buncher + HEBT + Energy corrector + 200 MHz RFQ + LEBTBuncher + HEBT + Energy corrector + 200 MHz RFQ + LEBT– Beam emittances essentially preservedBeam emittances essentially preserved– Transmission (deceleration efficiency) 50%Transmission (deceleration efficiency) 50%– Output energy variableOutput energy variable

W.Pirkl et.al.W.Pirkl et.al.

20

• RF power tests completed at CERNRF power tests completed at CERN• Tests using protons at Tests using protons at Aarhus tandemAarhus tandem• Installation at AD in October, first physiInstallation at AD in October, first physi

cs in Novembercs in November

5 MeV protons5 MeV protonsfrom Tandemfrom Tandem

21

~ 50 keV antiproton non-destructive detector~ 50 keV antiproton non-destructive detector

• 2-dimmensional readout2-dimmensional readout• Ultra-high vacuum compatible (no outgasing)Ultra-high vacuum compatible (no outgasing)• Tested with 20-50 keV protonsTested with 20-50 keV protons

22

Antiprotonic helium atoms at ultra-low densitiesAntiprotonic helium atoms at ultra-low densities

•Direct coupling to RFQ decelerator

•Differential pumping + ultra-thin beam window

•Very high efficiency of stopping antiprotons, in helium/hydrogen at ult

ra-low densities (P<1 mb, T=5 K)

•Non-destructive measurement of beam profile.

23

Ultra-narrow banded CW pulse-amplified laserUltra-narrow banded CW pulse-amplified laser

Littrow diode laser

Iodine cellEOMAOM

AOMIsolator

Tapered amplifier

Stabilized HeNe laser

Reference cavity Wavemeter

AOM

Isolator

Isolator

784 nm, 200 mW

629 nm

784 nm + 200 MHz

Etalon

2GHz photodiode

BBO

392 nm, 80 mJ

Ring Ti:Sapphirelaser

Q-sw itched NdYAG Coherent Infinity

629 nm

•<50 MHz bandwidth

•Very high output power (50-80 mJ at 392 nm)

•Random trigger capability (synchronization with AD beam)

24

Primordial states of antiprotonic heliumPrimordial states of antiprotonic helium

• First direct measurement of primary poFirst direct measurement of primary po

pulation (n,l) of exotic atom.pulation (n,l) of exotic atom.

• Some diabatic-state type theories predSome diabatic-state type theories pred

ict initial metastable population of 3ict initial metastable population of 3

0%, due to higher-lying states n>40.0%, due to higher-lying states n>40.

• Other theories predict populations only Other theories predict populations only

in n=38 vicinity (3% metastable fractioin n=38 vicinity (3% metastable fractio

n) at ANY density.n) at ANY density.

• Laser spectroscopy of n=50 states usiLaser spectroscopy of n=50 states usi

ng Optical Parametric Oscillator laser.ng Optical Parametric Oscillator laser. G.Ya.KorenmanG.Ya.Korenman

Experimental values for initial captureExperimental values for initial capture

26

Energy-lossEnergy-loss

• Antiproton dE/dX at T=0.1 ~ 50 keVAntiproton dE/dX at T=0.1 ~ 50 keV• Solid (100 Å) and gas(~ 10 mbar) Solid (100 Å) and gas(~ 10 mbar) • ESA ready at Aarhus, precision proton dataESA ready at Aarhus, precision proton data!!

S.P.Moller et.al.S.P.Moller et.al.

U.Mikkelsen et.al.U.Mikkelsen et.al.

27

Metastable antiprotonic atoMetastable antiprotonic atoms in vacuumms in vacuum

•Protonium atomsProtonium atoms in large in large (n,l)(n,l) states have 1-10 states have 1-10 mms lifetimes.s lifetimes.

•Antiprotonic heliumAntiprotonic helium in dense helium have 3 in dense helium have 3 mms lifetimess lifetimes– Auger decay is suppressed.Auger decay is suppressed.– n=35-41n=35-41 states are populated. states are populated.

•Extended to Extended to tt=10 =10 mms in vacuum?s in vacuum?– higher n higher n (up to 100?) are populated(up to 100?) are populated

•Antiprotonic lithiumAntiprotonic lithium in vacuum may also be metastable in vacuum may also be metastable– Auger process highly suppressed? Auger process highly suppressed?

K. OhtsukiK. Ohtsuki

28

Protonium production in single collisionsProtonium production in single collisions

What do you need?What do you need?•Ultra-low energy antiprotons at T<10 eVUltra-low energy antiprotons at T<10 eV•Collision-less environment Collision-less environment •High-density atomic hydrogen target at P=10High-density atomic hydrogen target at P=10-3-3 mb. mb.

J.CohenJ.Cohen

29

Primary populations of antiprotonic atoms Primary populations of antiprotonic atoms

•Primary population Primary population (n,l)(n,l) tuned by varying antiproton energy T. tuned by varying antiproton energy T.•Angular distribution of emitted Auger electron. Angular distribution of emitted Auger electron.

J.CohenJ.Cohen

30

Ionization of simple Ionization of simple atoms by antiprotonsatoms by antiprotons

•Extension of LEAR data to lower eExtension of LEAR data to lower energies (T<10 keV)nergies (T<10 keV)

•Double ionization measurementsDouble ionization measurements– may help us understand theory-expmay help us understand theory-exp

eriment discrepancy in eriment discrepancy in double-ionizdouble-ionization of heliumation of helium..

H. Knudsen et.al.H. Knudsen et.al.

31

Production of eV beamProduction of eV beam

Y.Yamazaki et.al.Y.Yamazaki et.al.

32

Beamline developed at UT-KomabaBeamline developed at UT-Komaba•B=5 Tesla superconducting solenoid, B=5 Tesla superconducting solenoid, with high-speed ramp of magnetic fielwith high-speed ramp of magnetic field.d.•Negative hydrogen ion source (to simuNegative hydrogen ion source (to simulate antiprotons)late antiprotons)Y.Yamazaki, N.Oshima, H.Higaki, T.Ichioka et.al.

33

Antiproton trapAntiproton trap•100-mm long harmonic region (to trap >1e7 antiprotons, and radially compr100-mm long harmonic region (to trap >1e7 antiprotons, and radially compress to < 1mm)ess to < 1mm)

•Segmented electrodes for applying rotating wallSegmented electrodes for applying rotating wall

•V=15 kV catching electrodeV=15 kV catching electrode

•Mechanical precision 10Mechanical precision 10mmm, to suppress diocotron instabilities and prolonm, to suppress diocotron instabilities and prolong trapping lifetime.g trapping lifetime.

T.Ichioka, H.Higaki, A.Mohri, M. Hori, Y.YaT.Ichioka, H.Higaki, A.Mohri, M. Hori, Y.Yamazaki et.al.mazaki et.al.

34

Radial compression of Radial compression of electron cloud via “rotating electron cloud via “rotating

wall” methodwall” method

T.Ichioka, H.Higaki et.al.T.Ichioka, H.Higaki et.al.

35

Electron-cooling of HElectron-cooling of H- - ionsions

Injection energy of H- at 100 eVInjection energy of H- at 100 eVElectron energy 0.1 eVElectron energy 0.1 eV

B=1 TeslaB=1 TeslaDemonstrated cooling of 10Demonstrated cooling of 1066 H- ions H- ions

to T<1 eV in 10 secondsto T<1 eV in 10 seconds

T.Ichioka, H.Higaki, A. Mohri et.al.T.Ichioka, H.Higaki, A. Mohri et.al.

36

Extraction of antiprotons from trapExtraction of antiprotons from trap•High-efficiency extraction of antiprotons from trap using Einzel lenses in “acceleration High-efficiency extraction of antiprotons from trap using Einzel lenses in “acceleration mode”mode”•Differential pumping from 10Differential pumping from 10-5-5 mb to 10 mb to 10-11-11 mb via adjustable slits mb via adjustable slits

K.Y.Franzen, N.Kuroda et.al.K.Y.Franzen, N.Kuroda et.al.

37

ConclusionConclusionUsing new experimental techniques….

– Very low energy beams (10 eV)Very low energy beams (10 eV)– Very high-precision spectroscopy systems (<10Very high-precision spectroscopy systems (<10-8-8))

We will measure antiprotonic atoms and interactionsbetween antiprotons and atoms in a completely new regime.

– Bound-state QEDBound-state QED– CPT theorem CPT theorem – high-precision 3-body theories high-precision 3-body theories – Atomic cascade Atomic cascade – Chemical-physics Chemical-physics – Stopping powerStopping power– IonizationIonization– ChannelingChanneling– Antiprotonic atom formationAntiprotonic atom formation