DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich 1 A ATHENA - Cold antihydrogen production Production of cold antihydrogen atoms in large quantities • Introduction • The ATHENA experiment + • New results • Summary • Outlook On behalf of the ATHENA collaboration C. Regenfus University of Zürich H detector Antihydrogen candidate (real data, 4- prong event) Sept. 02: > 50k cold antiatoms produced
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A DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich 1 ATHENA - Cold antihydrogen production Production of cold antihydrogen atoms in large quantities.
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DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
1A
ATHENA - Cold antihydrogen production
Production of cold antihydrogen atoms in large quantities
• Introduction• The ATHENA experiment +• New results• Summary • Outlook
On behalf of the ATHENA collaboration
C. Regenfus
University of Zürich
H detector
Antihydrogen candidate (real data, 4-prong event)
Sept. 02: > 50k cold antiatoms produced
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
2A
ATHENA - Cold antihydrogen production
Motivation
Antihydrogen: The simplest antimatter counterpart to matter
for testing fundamental physic principles
• CPT symmetry (Theoretical underpinning of field theories)• Gravitational acceleration (Equivalence principle)
A very high precision can be achieved by comparing antihydrogen to hydrogen
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
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ATHENA - Cold antihydrogen production
Future: high resolution laser spectroscopy
Atomic 1S - 2S transition by two-photon excitation (first order Doppler-free)
Lyman E = 10.2 eV = 2.5 x 1015 Hz = 122 nm UV 2 x 243 nm photons (mW)Lifetime of 2S state: 122 ms => precision ~10-16
Cesar et al. (1996)(Laser 3kHz, 150µK)
Need: Cold antihydrogen ( T < mK )Capture in neutral trapHydrogen reference cell
243 nm LASER
Mirror
H
H spectroscopy
Gravitation: atomic fountain / interferometry
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
4A
ATHENA - Cold antihydrogen production
Present physics menu
Plasma studies: new kind of plasma imaging
• Particle losses in trap• (Re)combination mechanism• Production of cold antihydrogen in larger quantities
Investigations
• Antihydrogen energy distribution (+ inner states)• Laser spectroscopy on non trapped atoms• Trapping H and/or creation of a H beam
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
5A
ATHENA - Cold antihydrogen production
The ATHENA collaboration
Particle traps + control:INFN, Sez. di Genova, and Dipartimento di Fisica, Università di Genova, Italy
EP Division, CERN, Geneva, SwitzerlandDepartment of Physics, University of Tokyo, Japan
Precision lasers:Department of Physics and Astronomy, University of Aarhus, Denmark
Instituto de Fisica, Rio de Janeiro, Centro de Educação Tecnologica do Ceara, Brazil
Positron plasma:Department of Physics, University of Wales Swansea, UK
INFN, Sez. di Pavia, and Dipartimento di Fisica Nucleare e Teorica, Università di Pavia, ItalyDipartimento di Chimica e Fisica per l'Ingegneria e per iMateriali, Università di Brescia, Italy
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
6A
ATHENA - Cold antihydrogen production
Experimental overview
Positron Accumulator
AntihydrogenDetector(T= 140 K)
0 1 m
0 10 cm
Na-22Source
AntiprotonCapture Trap Mixing Trap
CsI crystals
Si stripdetectors
Cryostat
e+3 T superconducting solenoid
15 K , 10-11 mbar
Main ATHENA features: Open access system (no sealed vacuum)Powerful e+ accumulation Plasma diagnosis and control High granularity imaging detector
Scint. Scint.Scint.
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
7A
ATHENA - Cold antihydrogen production
ATHENA Photo
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
8A
ATHENA - Cold antihydrogen production
Penning traps
Trapped electron at B = 3 T, E = 1 eV, U ~ 10 V
• Cyclotron motion (perpendicular to B)f = 84 GHz, r ~ 1 µmEmission of synchrotron radiation (cooling)t cool ~ 0.3 s
• Axial motion (along B)f ~ 7 MHz, d ~µm … cm
• E x B drift (‘magnetron’) (cooling over coupling)f ~ kHz, r ~ mm
Single particle <=> Plasma Coulomb coupling parameter: Ecoul/Etherm
Electrical screening distance: Debye length
ATHENA:Multi-ring Penning trap (choose Vz as you like )
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
9A
ATHENA - Cold antihydrogen production
Antiproton decelerator (CERN)
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
10A
ATHENA - Cold antihydrogen production
Antiproton capture and cooling with electrons
p
5 MeV50 cm
Antiproton Capture Trap
Solenoid (3 T)Degrader
Degrading
Trapping
Cooling
Vacuume-
TrappingPotential
5 KV
Cold electron cloud(Cooled by Synchrotron Radiation,
τ=0.4sτ3T)
Univ.ofGenov/IT
(τ=0)
(τ=200ns)
(τ=20-30s)
• Capture dynamics
• Capture trap (50 cm)
10 000 p / AD shot
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
11A
ATHENA - Cold antihydrogen production
Positron accumulation
Coldhead
300 Gauss guiding fields
T = 6 K50 mCi 22NaSolid neon moderator
Segmented electrodefor Rotating Wall
Beam strength:6 million e+ per second
e+Energy loss through collisions
e+
Accumulation rate: 106 e+/s
150 million e+ / 5 min
After transfer: 75 x 106 in mixing trap
Positron plasma : r~2mm, l~32mm, n~2.5 x 108 / cm3
Lifetime: ~hours
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
12A
ATHENA - Cold antihydrogen production
Non destructive positron plasma diagnostics
read
heat
drive
Complete model of plasma mode excitation
(based on ‘Cold Fluid Theory’ * )
PLASMA SHAPE, LENGTH, DENSITY
Plasma temperature change* D. Dubin, PRL 66, 2076 (1991)
kΔT =mzp2
5 ω2h( )2 −ω2( )2
[ ] 3−ωp2α2
2ω22d2 f(α)dα2
⎡ ⎣ ⎢
⎤ ⎦ ⎥
−1
~ 30 MHz
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
13A
ATHENA - Cold antihydrogen production
Detection principle of antihydrogen annihilations
• H atom dissociates to p and e+
by contact with the trap wall or rest gas atoms• pN -> charged and neutral pions
• e+ e- -> 511keV photons (back to back)
Good spatial resolution (< 1 cm ) of chargedvertex ( at least 2 prong events)Time coincidence (~ 1 µs)High rate capability (self triggering)
511 keV opening angle
Monte Carlo
Measure 1MeV on background of 2GeV
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
14A
ATHENA - Cold antihydrogen production
Detector development
Much effort into R&D
• Low temperature (~ 140 K)
• High magnetic field (3 T)
• Low power consumption
• Light yield of pure-CsI crystals ?
• CTE matching (Kapton, silicon, ceramics)
• Electronic components
Full detector installed: August 2001
All photodiodes replaced with APDs: Spring 2002
• Compact design (radial thickness 3 cm)
• High granularity (8K strips, 192 crystals)
• Large solid angle (>75 %)
Workshop Zürich , J. Rochet
Silicon micro strip layer
Mechanics for 77K
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich
15A
ATHENA - Cold antihydrogen production
Pure-CsI crystals + Avalanche Photo Diodes
22NaT = 150 K
0
2000
4000
6000
8000511 keV
back scatter
1275 keV
10000
FWHM = 18%
12000
Pulse height [keV] cos()
4000
3000
2000
1000
-1.0 -0.5 00 60 500 1000 1500 0.5 1.0
e+e−
γ(511keV)
γ(511keV)
• Read out close up • Crystal APD unit
• Crystal detector performance
~16 times higher light yield @ 80K
C. Amsler, et al. :Temperature dependence of pure-CsI, scintillation light yield and decay time. NIM A 480, 494–500 (2002).
Pure-CsI
DPG Frühjahrstagung Aachen 13.03.03 C. Regenfus Uni-Zürich