OVERVIEW OF RECENT WORK ON LASER EXCITATION OF POSITRONIUM FOR THE FORMATION OF ANTIHYDROGEN Anti-Apple g? g? Pauline Yzombard (1), on behalf of the AEgIS (2) collaboration (1) Laboratoire Aimé Cotton, Bâtiment 505, Orsay, France (2) AD-6: AEgIS, C.E.R.N. Route de Meyrin 385, 1217 Meyrin, Switzerland Earth
OUTLINE I. AEgIS experiment II. Positron and laser systems III. Recent works Ps(n=3) laser excitation Ps Rydberg IV. Future works: toward a colder H beam 2 MARCH 9 - LEAP 2016 - PAULINE YZOMBARD
I. AE gis COLLABORATION Stefan Meyer Institute University of Genova University of Milano University of Padova University of Pavia CERN Institute of Nuclear Research of the Russian Academy of Science Max-Planck Institute Heidelbert Politecnico di Milano University College London Czech Technical University University of Bergen University of Bern University of Brescia Heidelberg University ETH Zurich University of Lyon 1 University of Oslo University of Paris Sud University of Trento INFN sections of: Genova, Milano, Padova, Pavia, Trento
I. AEGIS ANTIMATTER EXPERIMENT: GRAVITY, INTERFEROMETRY, SPECTROSCOPY Main goal: Measurement of g with 1% precision on antihydrogen. Challenges: - Production of a bunched cold beam of antihydrogen - Measurement of vertical beam deflection (10 μm drop over 1 m) via moiré deflectometer. p trap moiré deflectometer g? Anti- Apple Aghion, S. and al. Nat. Commun vol 5 4538 (2014) Earth e+ Ps convertor Cf. Talk of Daniel Krasnicky Overview of latest results from AEgIS 4 MARCH 9 - LEAP 2016 - PAULINE YZOMBARD
I. AEGIS - PRINCIPLE Anti-hydrogen formation via Charge exchange process with Ps* Principle demonstrated by ATRAP collaboration Ps* produced via Cs* collisions on positrons trapped plasma C. H. Storry et al., Phys. Rev. Lett. 93 (2004) 263401] 93 (2004) 263401 Interests: Pulsed H production (time of flight Stark acceleration) Narrow and well-defined H n-state distribution Colder production than via mixing process expected MARCH 9 - LEAP 2016 - PAULINE YZOMBARD Rydberg Ps* Long lifetime + large cross section σ a 0 n 4 5 H formation enhanced
II. POSITRON AND LASER SYSTEMS - POSITRON SYSTEM Positron system Efficient transfer of positrons into the main traps - cf Talk of Daniel Krasnicky Overview of latest results from AEgIS Studying positrons and Positronium physics in a dedicated test chamber AEgIS zone 6 MARCH 9 - LEAP 2016 - PAULINE YZOMBARD
II. POSITRON AND LASER SYSTEMS - POSITRONIUM FORMATION Sketch of the e + system - parameters given for 2015 PbWO 4 3 10 4 e+ / 0.15s 22 Na 11mCi 7 10 8 e+ / 3min 3.3keV e+ bunch implanted SEM image: Silica-based nano- porous target Mariazzi S et al., Phys. Rev. B 2010, 81, 235481 7
II. POSITRON AND LASER SYSTEMS - POSITRONIUM FORMATION Ps formation sketch 3.3keV Production of Ps in the test chamber τ = 142ns SSPALS (single shot positron annihilation lifetime spectroscopy) ( * ) measurements Average of 10 single shots. S. Aghion et al. Nucl. Instru. Meth. in Phy. Res Sect. B 362:86 92, 2015. (*)Cassidy D B et al., NIMB 2007, 580, 1338 8
II. POSITRON AND LASER SYSTEMS - LASER SYSTEM Ps Internal energy n Rydberg 15 20 n=3 n=2 n=1 continuum ~1700 nm In front of the test chamber: Energy 1.3mJ, pulse 4ns, waist 10mm 205 nm In front of the test chamber: Energy 60µJ, pulse 2ns, waists 6mmx8mm A dedicated laser system: conceived to be broadband σ ~ 110GHz - to cover Doppler broadening and magnetic mixing (Zeeman effect, at 1 T) inside the main trap 9 MARCH 9 - LEAP 2016 - PAULINE YZOMBARD
1064 nm III. RECENT WORKS- POSITRONIUM = 3 LASER EXCITATION n Ps Internal energy continuum Test chamber n=3 excitation + photoionization Aghion S et al., PRA, submitted Feb.2016 n=3 n=2 photoionization Si0 2 nanoporous target Gamma detector o-ps cloud e+ preliminary 205 nm n=1 MARCH 9 - LEAP 2016 - PAULINE YZOMBARD EM conditions: B = 250 Gauss E = - 600 V/cm (Area laser OFF Area laser ON) S(%)= Area laser OFF 10
III. RECENT WORKS- POSTRONIUM = 3 LASER EXCITATION n - e+ implantation energy 3.3keV - Target at room temperature - excitation-ionization S(%) laser at resonnace 15.5% Scan of the n=3 transition preliminary -3P excitation line centered at 205.05±0.02 nm Predicted: 205.0474 nm - From this measurement: We extrapolate an average temperature of the excited o-ps : T ~1300K ± 200 K (Doppler broadening) 11 MARCH 9 - LEAP 2016 - PAULINE YZOMBARD Aghion S et al., PRA, submitted Feb.2016
III. RECENT WORKS- POSITRONIUM RYDBERG EXCITATION (VIA =3 STATE) n Ps Internal energy continuum Rydberg excitation (n=1 n=3 n = 15 transition) Scan of the Rydberg transitions n Rydberg 15 20 n=3 1680 nm - 1710 nm preliminary n=17 n=16 n=15 n=2 205 nm preliminary n=1 12 MARCH 9 - LEAP 2016 - PAULINE YZOMBARD Aghion S et al., PRA, submitted Feb.2016
IV. FUTURE WORK TOWARD COLDER H - Sympathetic Cooling of p with laser cooled anions Atomic anions studied: Os -, La - An alternative project: laser cooling of molecular anions, as C 2 - P. Yzombard et al. Phys. Rev. Lett. 114, 213001 13 MARCH 9 - LEAP 2016 - PAULINE YZOMBARD
IV. FUTURE WORK - TOWARD A POSITRONIUM LASER COOLING? - Focusing Ps beam via Doppler cooling Improving the H formation = having a better solid angle Laser focusing MARCH 9 - LEAP 2016 - PAULINE YZOMBARD 14
IV. FUTURE WORK - TOWARD A POSITRONIUM LASER COOLING? - Focusing Ps beam via Doppler cooling Ps Internal energy n=3 n=2 n=1 continuum 2P 243 nm 1S Challenge: short Ps lifetime (~142ns) Interest: lightest atom (µ =2 m e ) implies a huge recoil energy for each scattered photon (~1500m/s or 0.3 K) Laser development: a long pulse 243nm has to be implemented (pulse ~30ns to 200ns) MARCH 9 - LEAP 2016 - PAULINE YZOMBARD 15
IV. FUTURE WORK - TOWARD A POSITRONIUM LASER COOLING? -1D Doppler cooling? Ps Internal energy n=3 continuum Probing time Probing time Simulations: Ps 1D velocities distributions, probed for different timing during laser cooling B = 0 T. n=2 2P Probing time n=1 1S 243 nm Simulation parameters Legend: Velocities range excited by laser Probing time Ps velocities distributions (m/s) 1D P L w L Γ L δ L T 3D (Ps cloud) 5000W 7mm 50GHz 2.5cm -1 1000 K MARCH 9 - LEAP 2016 - PAULINE YZOMBARD 16
CONCLUSION AND OUTLOOK Recent works in Ps physics: First measurements of n=3 Ps laser excitation Proof of Rydberg excitation with our dedicated laser system major step to form H via charge exchange process Future developments for laser works: getting a colder p plasma (sympathetic cooling via cold anions) or/and focusing Ps beam (Doppler cooling) MARCH 9 - LEAP 2016 - PAULINE YZOMBARD 17
THANK YOU FOR YOUR ATTENTION MARCH 9 - LEAP 2016 - PAULINE YZOMBARD 18
APPENDIX Simulation code Anions laser cooling MARCH 9 - LEAP 2016 - PAULINE YZOMBARD 19
Algorithm - simulations Absorption-emission processes calculated using rate equations -> taking account : Laser detuning d, linewidth G laser, saturation and Doppler effects. L e e G e G f f d W Rabi L f G= 1/lifetime = natural linewidth G laser (FWMH) Total linewidth G tot = G+ G laser +G f +G e Einstein Rate equations r (h/2p)w Rabi =-<e q e r f>e laser I = e 0 c E laser2 /2=2 Power/(p waist 2 ) PHYSICAL REVIEW A 69, 063806 (2004) Rate Absorption
Algorithm - simulations -All levels and transitions needed (n=1->n=2) -gravity, magnetic field and recoil photons -Dipole moment aligned on local field local laser polarization. => Kinetic Monte Carlo + Verlet Internal state (population) KMC Solve exactly the rate equations. Better than standard (Metropolis) Monte Carlo P(t+dt)~P(t)+G dt External state (position) Verlet Verlet algorithm to drive the particles motion
Anions cooling? 22 Cooling Os -? Cooling La -? => Heidelberg, Ger. A. Kellerbauer C 2 - Cooling C 2 -?
electrons Studied Molecules: Candidate?
C 2 - Sisyphus cooling 24 Cooling C 2- - several simulations in Penning traps. P. Yzombard et al. Phys. Rev. Lett. 114, 213001 Penning-like trap configuration