25th. February 2011 CERN Detector Seminar P.D.Bowe ALPHA ANTIHYDROGEN TRAPPED Paul D. Bowe University of rhus, Denmark ON BEHALF OF THE ALPHA COLLABORATION Detector Seminar, CERN, Geneva 25th February 2011. 25th. February 2011 CERN Detector Seminar P.D.Bowe The ALPHA Collaboration University of Aarhus, Denmark Auburn University, USA University of British Columbia, Canada University of California Berkeley, USA Simon Fraser University, Canada University of Liverpool, UK NRCN - Nucl. Res. Center Negev, Israel Federal University of Rio de Janeiro, Brazil RIKEN, Japan University of Tokyo, Japan TRIUMF, Canada University of Wales Swansea, UK 25th. February 2011 CERN Detector Seminar P.D.Bowe Hydrogen atom in 2S state Decay to 2P ~100 years. Lamb shift ~ 1 GHz. Decay to 1S E dipole disallowed. Same parity. E quadrupole disallowed. Both states J=1/2. M dipole very weakly allowed ~ days. Two photon decay ~ 1/7 second Eliminate Doppler broadening: excite with two photons coming from opposite directions 25th. February 2011 CERN Detector Seminar P.D.Bowe Experimental precision with hydrogen beam, f(1S-2S) = (34) Hz - Hnsch et al. But systematics are murder Trapping and cooling antihydrogen reduces this to a simple comparison experiment..systematics avoided 25th. February 2011 CERN Detector Seminar P.D.Bowe CPT tests These atoms should behave exactly the same way. Do they? Once trapped, one can contemplate asking many other questions; hyperfine structure, Lamb shift, gravity etc. Have to make antiatoms first!! 25th. February 2011 CERN Detector Seminar P.D.Bowe CPT tests Development sincenow threatening 4 X 10 7 in 100 ns pulse 25th. February 2011 CERN Detector Seminar P.D.Bowe p _ e + Na 22 source Open system Easy access, mods, diagnostics. Not absolutely sure what is needed. Lots of positrons and easy lasering, But.. attain very good vacuum. Fancy HEP type detector. Simultaneous spatial and temporal detection of antiatom constituents. Irresistible proof of formation 25th. February 2011 CERN Detector Seminar P.D.Bowe Pbar trapping and cooling..10,000 pbars per shot _ + Improved since then now cool about 40,000 pbars in ~10s seconds 25th. February 2011 CERN Detector Seminar P.D.Bowe _ + Amoretti et al., Nature 419 (2002) 456 Retain vertex reconstruction ability 25th. February 2011 CERN Detector Seminar P.D.Bowe Trapping Neutral Anti-atoms? Quadrupole winding Mirror coils Solenoid field is the minimum in B Can these coexist? Well depth ~ 0.7 K/T Atom trapped through its magnetic moment Well depth whatever you like. Pbars trapped at keV. Charged particle cooling rate is proportional to square of solenoid strength. 25th. February 2011 CERN Detector Seminar P.D.Bowe The ALPHA Approach: higher-order multipole Can we hold onto ingredients long enough to make antihydrogen and cold enough so that antihydrogen is trapped Atom atom trap ~ 1 K. Penning trap ~10s eV Solenoid cools charged particles AND is bottom of atom trap quadrupole octupole 25th. February 2011 CERN Detector Seminar P.D.Bowe Trap Magnet Prototype Magnet technology developed by BNL. Magnet mechanical supports just glass and hydrocarbons. Almost all material is superconductor (very low copper ratio). Maximum trap depth for minimum pion scattering Low inductance high ramp rate. No unintended quenches. Quench protection with twist. Planned quenches essential to proof of trapping. 25th. February 2011 CERN Detector Seminar P.D.Bowe Detector Conceptual Drawing 3 layers to deal with curvature and extra material ATHENA had 2 but less material in the way. 8, 10, 12 azimuthal segments Split axially into two half-detectors Silicon unit 60x115 mm, 300 m thick Total length 460 mm mm pitch in r- (256 channels/ladder) mm pitch in z (256 channels/ladder) Readout chip IDEAS VA1TA with self-trigger 25th. February 2011 CERN Detector Seminar P.D.Bowe REPEAT ATHENA and ADD Flexible magnet design: catch antiprotons at 3 T; mix with positrons at 1 T. Allows deeper neutral trap. Octupole transverse field reduces perturbation of trapped charged plasmas (antiprotons and positrons). Silicon vertex detector a la ATHENA (2007). Faster positron accumulation~100 million in 200 seconds. Switch atom trap off quickly to give prompt time for looking for trapped antihydrogen. Diagnostics so that you know about something about what is going on other than the result of making anithydrogen. Learn how to measure and optimize important plasma parameters plasma size and temperature 25th. February 2011 CERN Detector Seminar P.D.Bowe Apparatus Cross Section 25th. February 2011 CERN Detector Seminar P.D.Bowe Positrons in ALPHA Octupole Fields at design maximum. Octupole 1.2 T, Solenoid 1 T. Mixing in ATHENA over 10s seconds > 1000s antihydrogen. Also showed could make antihydrogen at 1 T. ATHENA 3 T. J.Phys.B 41 (2008) FIRST PUBLICATION Phys. Rev. Lett. 98, (2007) Not dead yet! 25th. February 2011 CERN Detector Seminar P.D.Bowe Positrons in ALPHA Octupole Plasma compression by rotating wall well established. First time used to cool sympathetically 25th. February 2011 CERN Detector Seminar P.D.Bowe Positrons in ALPHA Octupole 25th. February 2011 CERN Detector Seminar P.D.Bowe Positrons in ALPHA Octupole First few per cent of particles leaving give tail of distribution before space charge and rearrangement interfere. This requires lepton sensitivity a few charges. Easier for pbars. Open system and low noise read out of MCP. MCP which also images both kinds of plasmas Pbar temperature ~300 K!!! Leptons higher especially in octupole Need to carry electrons pbars dont self cool. 25th. February 2011 CERN Detector Seminar P.D.Bowe Positrons in ALPHA Octupole Evaporative cooling pbars to then lowest measured temp ~10 K 25th. February 2011 CERN Detector Seminar P.D.Bowe Positrons in ALPHA Octupole antiprotons at 360 K 2 M positrons at 90 K Inject antiprotons autoresonantly Mix for 1 s Eject trapped charged particles Pulsed fields to clear any mirror- trapped pbars Fast shutdown of trap magnets (9 ms) Look for annihilating pbar from hbar Was it really a neutral? Compare to simulations Trap antihydrogen in magnetic minimum trap Trap depth ~ 0.5 K 6 candidates in 212 attempts. 25th. February 2011 CERN Detector Seminar P.D.Bowe Positrons in ALPHA Octupole antiprotons at 200 K smaller rad 2 M positrons at 40 K evaporatively cooled! Control experiment a la ATHENA heat positrons formation stops. Mix for 1 s Eject trapped charged particles Pulsed fields to clear any mirror- trapped pbars Fast shutdown of trap magnets (9 ms) Look for annihilating pbar from hbar Was it really a neutral? Apply bias electric fields during shutdown. Trap antihydrogen in magnetic minimum trap. Trap depth ~ 0.5 K 38 antiatoms trapped in 335 trails. 25th. February 2011 CERN Detector Seminar P.D.Bowe Positrons in ALPHA Octupole Close to an antiatom every try. Hold for 1000s seconds. Up from 1 every 35 hold for ~200 ms not so long ago. More to do. 25th. February 2011 CERN Detector Seminar P.D.Bowe Positrons in ALPHA Octupole Thank you for your interest! 25th. February 2011 CERN Detector Seminar P.D.Bowe People University of Aarhus: G.Andresen, P.D. Bowe, J.S. Hangst. Auburn University; F. Robicheaux. University of Calgary: R.I. Thompson,R.Hydomako. University of California, Berkeley: S.Chapman. A.Povilus, W. Bertsche, J. Wurtele, J. Fajans. University of Liverpool: P. Nolan, P. Pusa. Physics Department, NRCN, Beer-Sheva, Israel, E. Sarid, University of Manitoba: RIKEN: : D. Miranda, Y. Yamazaki. Federal University of Rio de Janeiro C. Cesar. University of Tokyo: R. Hayano. TRIUMF: M.C. Fujiwara, D. Gill, W.Hardy, L. Kurchaninov, K. Ochanski, A. Olin, J.Storey. University of Wales, Swansea: M. Jenkins, L.V. Jrgensen, N. Madsen, H.H. Telle, D.P. van der Werf, M. Charlton.