Towards anions laser cooling * Giovanni Cerchiari ( Elena Jordan Alban Kellerbauer Max-Planck-Insitut für Kernphysik (Saupfercheckweg 1, Heidelberg, Germany) International Workshop on Antiproton Physics and Technology at FAIR - Nov FAIR workshop G.Cerchiari

Outline Motivations Negative ions and laser cooling Experimental technique Result and cooling scheme 2FAIR workshop G.Cerchiari

3 AEGIS antimatter gravity experiment Main goal: Measurement of g with 1% precision on antihydrogen – Production of a bunched cold beam of antihydrogen (100 mK) – Measurement of vertical beam deflection (10 μm drop over 1 m) FAIR workshop G.Cerchiari

Doppler laser cooling Negative atomic ions atom Spontaneous emission Detuned laser radiation Negative ion Neutral atom Energy Ground Excited 4FAIR workshop G.Cerchiari

Bound–bound transitions in La − [C. W. Walter & N. D. Gibson, private communication (2014)] Peak 8 EnergyE = (3) meV Wavelengthλ = (2) nm preliminary all peaks unambiguously assigned laser cooling transition identified: 20 [S.M. O’Malley and D.R. Beck, Phys.Rev. A 81, (2010)] 5FAIR workshop G.Cerchiari

Ion Source Cs La La target [R. Middleton, A Negative-Ion Cookbook, PA October 1989 (Revised February 1990)] 6FAIR workshop G.Cerchiari

7 Apparatus Overall schematic: – Production of anion beam – Mass separation – Spectroscopy FAIR workshop G.Cerchiari

Spectroscopy technique Continuous anions current and laser beam Collinear interaction between ions and laser beams Detachment of excited state Measurement of neutral particles flux 8 Energy Ground Excited Resonant transition High cross section Non resonant transition Low cross section Electron affinity Neutrals E Faraday-Cup Anions Ion beam Laser Electrostatic deflector MCP FAIR workshop G.Cerchiari

Spectroscopy technique Continuous anions current and laser beam Collinear interaction between ions and laser beams Detachment of excited states Measurement of neutral particles flux 9 Energy Ground Excited Resonant transition High cross section Non resonant transition Low cross section Electron affinity Neutrals E Faraday-Cup Anions Ion beam Laser Electrostatic deflector MCP FAIR workshop G.Cerchiari

Neutrals Spectroscopy technique E Channeltron Faraday-Cup Anions Ion beam Laser Electrostatic deflector 10 Energy Ground Excited Resonant transition High cross section Non resonant transition Low cross section Electron affinity Neutrals produce secondary electrons on a gold mirror Secondary electrons are collected and counted The mirror allows for a second laser Ions in motion perceive to different Doppler shifts FAIR workshop G.Cerchiari

Neutrals Spectroscopy technique Neutrals produce secondary electrons on a gold mirror Secondary electrons are collected and counted The mirror can reflect a second laser on the beam Ions in motion perceive to different Doppler shifts E Channeltron Faraday-Cup Anions Ion beam Laser Electrostatic deflector 11 Energy Ground Excited Resonant transition High cross section Non resonant transition Low cross section Electron affinity Laser FAIR workshop G.Cerchiari

La − spectroscopy E = 5 keV [E. Jordan et al.,PRL 115 (2015) ] 12FAIR workshop G.Cerchiari

La − spectroscopy measurements for every acceleration energy Frequency at rest extracted from Doppler shifts E = 5 keV 13FAIR workshop G.Cerchiari

La − spectroscopy Hyperfine spectrum /2 5/2 7/2 9/2 11/2 5/2 7/2 9/2 E = 10 keV A g = 146.8(3) MHzB g = 36(9) MHz A e = 110.6(7) MHzB e = 5(1) MHz where C, D are functions of quantum numbers I, J, F 14FAIR workshop G.Cerchiari

La − cooling Hyperfine spectrum /2 5/2 7/2 9/2 11/2 5/2 7/2 9/2 E = 10 keV 3/2 5/2 7/2 9/2 11/2 5/2 7/2 9/2 15FAIR workshop G.Cerchiari

Outlook La − seems to be excellent laser cooling candidate Next steps: – Paul trap to trap and laser-cool La − under construction – Development of sideband generation for existing laser system – Measurement of resonant cross-section 12 16FAIR workshop G.Cerchiari

Thanks 17FAIR workshop G.Cerchiari