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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Production of cold antihydrogen atoms in large quantities
Production of cold antihydrogen atoms in large quantities. C. Regenfus. University of Zürich. On behalf of the ATHENA collaboration. Sept. 02: > 50k cold antiatoms produced. Introduction The ATHENA experiment + New results Summary Outlook. H detector. - PowerPoint PPT Presentation
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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)
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 µm
Emission 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 MeV
50 cm
Antiproton Capture Trap
Solenoid (3 T)
Degrader
Degrading
Trapping
Cooling
Vacuume-
TrappingPotential
5 KV
Cold electron cloud(Cooled by Synchrotron Radiation,
τ=0.4 3 )s at T
. /Univ of Genova IT
(t=0)
(t=200 )ns
(t=20-30 )s
• 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 22Na
Solid 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 =mzp
2
5ω2
h( )
2−ω2( )
2
[ ] 3−ωp
2α2
2ω22
d2 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
22Na
T = 150 K
0
2000
4000
6000
8000
511 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(511 )keV
γ(511 )keV
• 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