ASACUSA – Beamtime 2012
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ASACUSA – Beamtime 2012Stefan Ulmer
for the ASACUSA Collaboration
ADUC/ELENA Meeting 11/20/2012
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• Brescia Subgroup and collaborators– Nuclear Collisions with Low Energy Antiprotons
(April – End May)• CUSP subgroup (Including MUSASHI and SMI)
– Progress towards the production of a spin polarized antihydrogen beam
• pbar Helium subgroup– Further improvement of precision on pbar/He
laser spectroscopy
ASACUSA – 2012 Physics Program
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Brescia Collaboration
Investigation of Low Energy Antiproton Collision
Cross-Sections
pA A-1
p
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Nuclear collisions with antiprotons
p A A-1
p
Measurements of antiproton-nucleus annihilation cross section for:
- Nuclear Physics interest: saturation with target mass number
- Fundamental Cosmology interest: matter-antimatter asymmetry in the Universe
Energy range: 100 keV – 5 MeV
Light and heavy nuclear targets
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Low Energy Antiproton Scattering
?ASACUSA PLB 2011
Medium-heavy and heavy nuclear targets
Results consistent with theoretical expectations
2012
Bianconi et al. Phys. Lett.B 2011
- the number of stopped pbars in the target not negligible- Ultra-thin targets needed.- Targets less than 100 nm in thickness -> Carbon target - Other targets: Platinum and Palladium deposited on carbon film
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2012 - Annihilations cross-sections @ 130 keV
Aghai-Khozani et al. Eur. Phys. J. Plus 2012
Annihilations on the target
End-wall annihilations
Clear separation between signal and background
Cross-sections values to be extracted from data
First measurement at these very low energies
Beam monitor @ target position
dogleg to select the pbars with the required momentum
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CUSP Collaboration
PROGRESS TOWARDS THE PRODUCTION OF A POLARIZED
ANTIHYDROGEN BEAM
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Basic Spectroscopy
Physics Goal: precise spectroscopy of antihydrogen hyperfine structure using a polarized beam.
CUSP trap
MicrowaveCavity
SextupoleMagnet
Hdetector
p
H
e+
beam (LFS)H
1.420x10 Hz1 S
2 P
2 P2
2
1/2
3/2
1/2
1/2
F=1
F=0
F=0
F=0
F=1F=2
F=1
2 S
2
2
F=1
0.1 0.2
magnetic field [T]
LFS
HFS
2.466x10 Hz15
Pbar e+
Up Down
Down Down
Up Up
Down Up
Some indication of hbars at detector but 2011 signal was very weak
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• Improvement of antihydrogen yield– More positrons using a rare-gas moderator (accumulated earlier
4 million in 40 minutes, only)• More experiments• Higher particle density • Improved reaction cross section
– Direct compression of antiprotons
• Improve noise on apparatus– Lower plasma temperature– Improved reaction rate
2012 Strategy
Improved Electronics
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RGM: 10 times more moderated positrons
Positron Progress
60 million in 50 minutes
Compared to 2011:Improved by a factor of 12
Much more experiments conducted in 2012 beamtime at much higher positron densities
Worked out smooth potential procedures -> Particles remain compressed
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Direct Compression of Antiprotons
• Found pbar compression conditions (100k -> 220k in 200s)
• First direct compression of pbars
• Best compression achieved: 3mm diameter in CUSP trap
Improved interaction density of pbars before mixing
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• Prepare 40 million positrons in the nested• Inject directly from MUSASHI trap• Apply RF during interaction
RF Assisted Direct Injection
Produced encouraging results – further evaluation in progress
Frequency Scaling in Nested Well
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Pbar Helium Collaboration
Further improvement of laser spectroscopy of pbar/Helium and precise determination of the
antiproton to electron mass ratio
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Antiprotonic Helium Laser Spectroscopy
2 photon spectroscopy on antiprotonic Helium: (n,l) -> (n-2, l-2) typeAnti-collinear lasers: Doppler broadening cancels partly -> Narrow lines
long lived
short lived
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Experiment-Theory Comparisonof Spin-Averaged Transition Frequencies Published in 2011
Three transition frequencies agreed with QED calculations with a fractional precision of 2.3 - 5 ppb.
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Status so far
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1. Attempts to cool down atoms to lower temperatures by collisional gas buffer cooling -> Improved Precision
2. Systematic laser spectroscopy studies to evaluate experimental uncertainties.
3. Many instrumentation changes compared to results published in 2011:1. Developed cw semiconductor diode injection-seeded laser system. Easy to handle2. New long-pulse DPSS Nd:YAG laser and dye lasers. Narrower lines 3. Raman shifter to access mid-infrared regions. Access higher n-states4. Three new experimental targets. More cooling power, colder target5. …many more…
4. Added ability to carry out second parasitic spectroscopy experiment in parallel to main precision experiment, using residual undecelerated antiproton component near beam dump at the end of RFQD (very confined space 30 cm and large beam diameter 40 mm, only good for certain types of experiments).
1. Parasitic experiment to search for weak transitions at mid-infrared regions >1150 nm.
2. Parasitic experiment to search for transitions in atoms embedded in superfluid helium (condensed matter physics).
Physics program in 2012
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Electrostatic quadrupole triplet – ELENA prototype
Bore diameter 100 mmLength 700 mmTested for 70-130 keV antiprotons for several weeksstable operation
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More (burning) results will be presented at next SPSC meeting
! Thanks a lot for your attention !