ASACUSA Experiment at ASACUSA Experiment at CERN’s CERN’s Antiproton Decelerator Antiproton Decelerator Atomic Spectroscopy And Atomic Spectroscopy And Collisions Using Slow Collisions Using Slow Antiprotons Antiprotons LEAP 2000 Conference LEAP 2000 Conference Venezia, Italy Venezia, Italy August 2000 August 2000 M. Hori CERN M. Hori CERN
37
Embed
ASACUSA Experiment at CERN’s Antiproton Decelerator
ASACUSA Experiment at CERN’s Antiproton Decelerator. Atomic Spectroscopy And Collisions Using Slow Antiprotons. M. Hori CERN. LEAP 2000 Conference Venezia, Italy August 2000. Institute of Applied Physics, Tsukuba University, Azuma, T - PowerPoint PPT Presentation
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
ASACUSA Experiment at CERN’sASACUSA Experiment at CERN’sAntiproton DeceleratorAntiproton Decelerator
Atomic Spectroscopy AndAtomic Spectroscopy AndCollisions Using SlowCollisions Using Slow
• 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
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
• 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
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
• 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
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
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.