The ALPHA Collaboration

The ALPHA Refresher Initial goal: trapped antihydrogen Transverse multipole for trapping antihydrogen Higher order (octupole) to minimize plasma perturbations Longitudinal trapping by mirror coils Well depth of about 1 K at r=23 mm Silicon vertex detector, no 511 keV gamma detector Special magnet construction to minimize scattering of pions Three layers of silicon - reconstruct track curvature ATHENA positron source - new 75 mCi source All lasers from ATHENA

Apparatus Cross Section

External Solenoid

Axial Field Configuration 3 T in catching region, 1 T in mixing for larger neutral well depth Outer solenoid Inner solenoid Mirror coils

Trap Magnet Prototype Magnet exceeds design goals, proceeding with final version (8 layers, 2 mirrors, inner solenoid), article in preparation Initial tests with electrons Open now for modification Continue plasma studies until May Two layer multipole plus one mirror coil Installed in 8 T solenoid at Berkeley Internal Penning trap for electrons Study magnet performance, quench protection, plasma behavior, etc.

Berkeley Set-up

TYPICAL QUENCH In brief Berkeley system: Magnet very robust against quenching Meets or exceeds magnetic design First results with particles: straight-through, encouraging - agree with simulations Clear superiority over quadrupole First electrons trapped - no important results yet Continue operation until May Study trapping Study magnetic coupling between coils Gain important operating experience Test thin-walled trap The top graph shows to the voltage applied to the heater. The second graph shows the current through the octupole. The third graph shows the resistivity of the heater segment, and the fourth shows the temperature of this segment. The fifth graph shows the potential across the heater segment and the two nearest segments, while the last graph zooms in on the times just after the quench. The geometry is shown in the schematic. We calculate the quench velocity by measuring the time the quench takes to cross the “propagation” segment; namely, the time between when the quench first appears in propagation segment, and when it first appears in the “detection” segment. The quench velocity is this time divided into 2.0cm; in this case, about 29m/s.

Final Magnet Fabrication I

Final Magnet Fabrication II

Trap Electrode Configuration quadrupole Pbar direction multipole s=6

Trap Electrode Design

Detector Conceptual Drawing 3 layers 8, 10, 12 azimuthal segments Split axially into two half-detectors Basic sensor 60x115 mm, 300 m thick Two sensors butted axially per “ladder” Total length 460 mm 0.234 mm pitch in r- (256 channels/ladder) 0.898 mm pitch in z (256 channels/ladder) 4 readout chips per ladder - IDEAS VA1TA with self-trigger Carbon fiber support structure

Sensor Schematic 256 horizontal strips on front Not to scale

Vertex Resolution

Monte Carlo Simulations Annihilations on Penning trap wall Uniform distribution “Hot spots”

Detector DAQ Schematic 128 ch x 4 x 60  30720 ch 6 ADC modules VF48 1 ADC for 1 layer half-detector 14 repeater cards No analog multiplexing  less dead time for Trigger

ALPHA Status and Milestones Design of apparatus complete, critical components being fabricated Active theory involvement in all aspects of experiment Active parallel, prototype program at Berkeley for SC magnets and trap physics Final magnets being produced at BNL, ready for June start-up New trap construction techniques developed, control system Si vertex detector delayed by funding considerations, now fully funded Start up with 1/2 detector axial length and reduced azimuthal coverage Continue detector fabrication during the run, install 2nd half when complete Approved 2006 physics goals achievable with scintillators and field ionization Experiment fully funded; two successful peer review grants (UK, Canada) in 2005

ALPHA RUN PLAN/ BEAM REQUEST SCINTILLATORS SCINTILLATORS NEW MCP DETECTOR SCINTILLATORS SCINTILLATORS, SILICON NEW! NEW! SCINTILLATORS and Field ionization, or SILICON NEW! NEW! NEW!

Longer Term

“SELENA” Comparable to existing Liquid helium Capacity in experiments Use BNL technique to make SC Combined-function magnets, electron cooler and compensation solenoids Cold bore vacuum system: lifetime problem at low energy solved No iron in construction: hysteresis concerns for repeated deceleration eliminated FYI: ALPHA prototype $20,000 Comparable to existing Liquid helium Capacity in experiments

People University of Aarhus: P.D. Bowe, J.S. Hangst Auburn University; F. Robicheaux University of Calgary: R.I. Thompson University of California, Berkeley: A. Deutsch, K. Gomberoff, W. Bertsche, E. Sarid†, J. Wurtele, J. Fajans University of Liverpool: A. Boston, M. Chartier, R.D. Page, P. Nolan University of Manitoba: G. Gwinner RIKEN: Y. Yamazaki Federal University of Rio de Janeiro: D. Miranda, C. Cesar University of Tokyo: R. Funakoshi, L.G.C. Posada, R. Hayano TRIUMF: J. Dilling, K. Ochanski, D. Gill, A. Olin, L. Kurchaninov, M.C. Fujiwara University of Wales, Swansea: M. Jenkins, L.V. Jørgensen, N. Madsen, H.H. Telle, D.P. van der Werf, M. Charlton † Permanent address: Physics Department, NRCN, Beer-Sheva, Israel