GBAR Project Gravitational Behavior of Antihydrogen at Rest

Transcription

1 GBAR Project Gravitational Behavior of Antihydrogen at Rest Pierre Dupré CEA Saclay, FRANCE 1

2 Contents Motivation Scheme Schedule 2

3 Motivation A direct test of the Equivalence Principle with antimatter The acceleration imparted to a body by a gravitational field is independent of the nature of the body : Inertial mass = gravitational mass No direct measurement exists 3

4 Principle of the experiment Free fall of H v z ~ 1 m/s h = 10 cm Gbar using H + to produce slow H H + = [ p e + e +] H = [ p e + ] 4

5 Gbar : g experiment using H + to get H atoms Produce ions H + Capture ions H + Sympathetic cooling 20 µk Photodetachment of e + Time of flight gravity detector H + detector (t 1 ) cooling 20 µk Laser (t 0 ) h = 1/2 g (t 1 -t 0 ) 2 Eof H + Relative Precision on g: H + in ion trap Δg/g J.Walz & T. Hänsch, General Relativity and Gravitation, 36 (2004) 561. H + Formation p + Ps H + e H + Ps H + + e Ps = [ e + e ] 5

6 Cross-sections on PS J. P. Merrison et al., Phys. Rev. Lett. 78, 2728 (1997) σ ~10-15 cm 2 H.R.J. Walters and C. Starett, Phys. Stat. Sol. C, 1-8 (2007) σ ~10-16 cm 2 AD Facility CERN e + from Trap p + Ps H + e E p [kev] 10 7 p } Ps/cm H 8 H + H + Ps H - + e + E Ps [ev] E H = 6 kev in Ps frame if all Ps excited to n=3, expect 80 6

7 GBAR scheme e + Production e + Collection fast H & H + slow H + 1 LINAC 10 2 Target 3 Moderator/ Trap 4 Collector e + ~ MeV ev e + ~ mev 5 Ps Ps* Ps dense 6 p Ion Trap & Neutralize Laser Gravity measurement ~ 5 KeV 7

8 High intensity slow positrons source SOPHI project : ~ fast e + /s slow e + /s e + /e - selection LINAC 200 Hz / 4 µs e MeV target e MeV e - and γ 0-5 MeV Moderator e + slow : 3 ev ma Tungsten target ε e+/e- prod = Tungsten near primary target ε moderation = 10-4 Solid neon after e + /e - selector ε moderation =

9 Installation at Saclay Concrete shielding X rays Demonstrator e- Linac Ec = 5.5 MeV Imeasured = 0.14 ma 9

10 GBAR scheme e + Production e + Collection fast H & H + slow H + 1 LINAC 10 2 Target 3 Moderator/ Trap 4 Collector e + ~ MeV ev e + ~ mev 5 Ps Ps* Ps dense 6 p/p Ion Trap & Neutralize Laser Gravity measurement ~ 5 KeV 10

11 RIKEN Multi Ring Trap High magnetic Field radial confinement Potential well longitudinal confinement Cooling by e - plasma, 10 6 e + stored, trapping efficiency ε trapping ~ 1% At Saclay, accumulation with pulsed e + beam ε trapping = 50% expected, e + needed N. Oshima et al., Phys. Rev. Lett (2004) 11

12 GBAR scheme e + Production e + Collection fast H & H + slow H + 1 LINAC 10 2 Target 3 Moderator/ Trap 4 Collector e + ~ MeV ev e + ~ mev 5 Ps Ps* Ps dense 6 p/p Ion Trap & Neutralize Laser Gravity measurement ~ 5 KeV 12

13 Production of Ps/cm 2 Positronium target is produced with a porous SiO 2 converter e + + converter Ps Efficiency of Ps production in vacuum > 30% Ps in fundamental state Ec ~40 mev Experiments with ETHZ (e + beam) L.Liszkay et al., Appl. Phys. Lett. 92 (2008) Experiments at UCR (trap) D. B. Cassidy et al., Phys. Rev. A (2011) 13

14 Yield of o-ps : comparison CERN/UCR Measurement at CERN ~ 3.5 x 10 5 e + cm -2 s -1 e + flux x ~10 11 Measurement at UCR ~ 5.6 x e + cm -2 s -1 No loss in conversion efficiency in spite of the intensity factor 14

15 Linac 10 8 slow e + /s H + production e + trap accumulate e + during p filling ~ 30 Dump e + in Ps converter in < τ Ps =142 ns RIKEN test : e - / 75 ns p + Ps H + e H + Ps H + + e tube geometry to keep density (SiO 2 reflects Ps 100%) SiO 2 coating fast extraction from trap 15

16 GBAR scheme e + Production e + Collection fast H & H + slow H + 1 LINAC 10 2 Target 3 Moderator/ Trap 4 Collector e + ~ MeV ev e + ~ mev 5 Ps Ps* Ps dense 6 p/p Ion Trap & Neutralize Laser Gravity measurement ~ 5 KeV 16

17 H + cooling Segmented RF Paul Trap, well depth ~1 ev Sympathetic cooling using Be + ions Coulomb interaction of H + and Be + Laser cooled Be + ions Cooling laser H + capture trap Be + trap Be + Doppler cooling Temperature ~1 mk Be + sub-doppler cooling Temperature ~20 µk 17

18 H + cooling Segmented RF Paul Trap, well depth ~1 ev Sympathetic cooling using Be + ions Coulomb interaction of H + and Be + Laser cooled Be + ions Photodetachment Cooling laser H + capture trap Be + trap 18

19 Prospects Gravitational quantum states of Antihydrogen A. Yu. Voronin, P. Froelich, and V. V. Nesvizhevsky, Phys. Rev. A 83, (2011) H Source: very low temperature high phase-space density compact system Improve the precision on g with the spectroscopy of gravitational levels of H 19

20 GBAR Schedule 2007: P. Pérez et al, LOI CERN SPSCI-038, CEA/IRFU, RIKEN, Tokyo U. 2011: CERN Proposal 2014: Installation at CERN 2015: First measures 20

21 Backup theories J. Scherk, Phys. Lett. B (1979) 265. Newton Supergravity: has component of repulsive gravity Constraints K 0 - K 0 SN1987a Cyclotron frequency p/p G. Chardin, J.-M. Rax, Phy. Let. B 282 (1992) M.M. Nieto and T. Goldman, Phys. Rep. 205 (1991) 221. Direct Tests Charged antimatter Neutral antimatter e + or p (e.m. shielding) n hard to slow down H cooling limit mk AEGIS(CERN) Ps short lifetime H + cooling limit µk This Project 21

22 RIKEN accumulation e + scheme N. Oshima and al., Phys. Rev. Lett. 93, (2004) e - plasma n ~10 11 cm -3 as energy absorber (few ev/round trip) large energy spread compressed by injecting e+ beam in the remoderator Trapping efficiency ~ 1% (~ 10 6 /10 7 accumulated e + ) e - well: depth = 1kV length ~40 cm 2x10 10 e- e + well: depth = 50 ev length ~12 cm Remoderator ε RM ~ 0.1 Accumulation de positrons 22