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i r f u
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i r f u
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i r f u
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i r f u
yalcas GBAR Gravitational Behavior of Antihydrogen at Rest
27/04/2011 Pascal Debu - CEA/DSM/IRFU 1
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Motivation
2
A direct test of the Equivalence Principle with antimatter
The acceleration imparted to a body by a gravitational
field is independent of the nature of the body :
Inertial mass = gravitational mass
27/04/2011 Pascal Debu - CEA/DSM/IRFU
13
Be/Ti
13
Earth/Moon
Weak Equivalence Principle (torsion pendulum)
S.Schlamminger et al, Phys Rev Lett 100 (2008) 041101
Strong Equivalence Principle (Lunar Laser Ranging)
a / a 0.3 1.8 x10
a / a 1.0 1.4 x10
J.G.Williams et al, Phys Rev Lett 93 (2004) 261101
Tested to a very high precision with many materials
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Theory and Experiments:
J. Scherk, Phys. Lett. B (1979) 265
Discussion and experimental constraints : M. Nieto and T. Goldman, Phys. Rep. 205 (1991) 221
Motivation for antigravity in General Relativity: G. Chardin, Hyperfine Interactions 109 (1997) 83
.
Supergravity : one componentof repulsive gravity
Newton
Indirect Tests Antimattercontent of matter K0 - K0 system ν from SN1987a Cyclotron frequency
p/p
Direct Tests Charged
antimatter
e+
p
Pb : e.m. shielding
F. Witteborn and W.
Fairbank, Phys Rev Lett 19
(1967) 1049
PS200 Los Alamos Report
LA-UR 86-260
Neutral
antimatter
n hard to slow down T. Brando et al, NucI.
Instrum. Methods 180
(1981) 461
Ps short lifetime
polarisability…
A.P. Mills, M. Leventhal,
NucI. Instrum. Meth. .
B192 (2002) 102
No direct measurement available yet
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Next simplest system: H
-L = 1 m & vh = 1000 m/s → h = 5 µm (T(H) ~ 4 K ~ 0.3 meV)AGE : LOI FNAL suspended
-L = 1 m & vh = 500 m/s → h = 20 µm (T(H) ~ 100 mK ~ 7 μeV) AEGIS : approved CERN experiment
- L = 0.1 m & vh = 0.5 m/s → h = 20 cm (T(H) ~ 20 μK ~ 1 neV)
GBAR : cooled H+ → slow H
P. Pérez et al, LOI CERN –SPSCI-038 (2007) Irfu, Riken, Tokyo U.
L
HPrinciple :
parabolic flightInterferometer
deflectometer
free fall
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Gbar : g experiment using H+ to get H atoms
• Produce ion H+
• Capture ion H+
• Sympathetic cooling 20 µK
• Photodetachment of e+
• Time of flight
Error dominated by
temperature of H+
Relative Precision on g:
H+in ion trap g/g
5 105 0.001
104 0.006
103 0.02
h = 10 cm ∆t = 143 ms
J.Walz & T. Hänsch,
General Relativity and Gravitation, 36 (2004) 561.
h = 1/2 g (t1-t0)2
H+
gravity
detector (t1)
detector
Laser (t0)
cooling 20 µK
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Gra
vity m
easure
ment
e+ Production
& Accumulation fast H & H + slow H + slow H
1- 6 KeV
Photo
detach
12
137
8
Ps dense6
Ps → Ps*Target2
LINAC1
Moderator/
Collector
e+ ~ MeV→eV
3
Penning Trap
e+ ~meV
4
5
p
Penning Trap ELENA
H+ Trap
Paul Trap
Be+
laser cooling
9
10
11
ε=10-4
ε=10-2-10-4
ε=0.5
ε=10 ?
ε=0.35
Synoptic Scheme
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High intensity slow positrons source
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LINAC
e-
5.5 MeV
targ
et
e+
0-3 MeV
e- and γ0-5 MeV
Moderator
e+ “slow” : 3 eV
Tungsten target
εe+/e- prod = 2 10-4
200 Hz / 4 μs
0.1-0.2 mA
Tungsten near primary target
εmoderation = 10-4
Solid neon after e+/e- selector
εmoderation = 3 10-3
e+/e-
selection
~ 3 1011 fast e+/s
107 –108 slow e+/s
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Installation at Saclay
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Concrete
shielding X
rays
Demonstrator e- Linac
Ec ≈ 4.5 MeV
Imeasured = 0.14 mA
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Fast e+ detection35 Faraday cups
927/04/2011 Pascal Debu - CEA/DSM/IRFU
expected positron yield from 1 mm W target at 5.5 MeV
~ 1 x10-4 per electron
Linac peak current ~ .14 mA during 4 μs
charge seen on pads 11-12 ~ 4 pC per burst as expected
from Linac effective energy
First positrons measured end of 2009
e+ e-
E = (5.5 - 8.7 x 10-4 x I)
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Slow e+ Beam line in construction
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RIKEN Multi Ring Trap
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• Cooling by e- plasma, 106 e+ stored, trapping efficiency εtrapping~ 1%
• Trap now at Saclay: start test accumulation with pulsed e+ beam end 2011
εtrapping ≈ 50% expected, few 1010 e+ needed
N. Oshima et al., Phys. Rev. Lett. 93 19 (2004)
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Gra
vity m
easure
ment
e+ Production
& Accumulation fast H & H + slow H + slow H
1- 6 KeV
Photo
detach
12
137
8
Ps dense6
Ps → Ps*Target2
LINAC1
Moderator/
Collector
e+ ~ MeV→eV
3
Penning Trap
e+ ~meV
4
5
p
Penning Trap ELENA
H+ Trap
Paul Trap
Be+
laser cooling
9
10
11
ε=10-4
ε=10-2-10-4
ε=0.5
ε=10 ?
ε=0.35
Synoptic Scheme
27/04/2011 13Pascal Debu - CEA/DSM/IRFU
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Production of 1012 Ps/cm2
14
Positronium target is produced with a porous SiO2 converter:
dump few 1010 e++in less than ~ 140 ns onto converter
e+ converter → Ps
Experiments at CERN: Irfu/ETHZ (e+ beam)
and at UCR Cassidy et al. (trap)
• Ps in fundamental state
• Ec ~40 meV
• Efficiency of Ps production in vacuum > 30%
27/04/2011 Pascal Debu - CEA/DSM/IRFU
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Energy of o-Ps : comparison CERN/UCR
EΤ
E//
P. Crivelli et al., Phys. Rev. A 81, 052703 (2010)
D. B.. Cassidy et al., Phys. Rev. A 81, 012715
(2010).
Measurement
at CERN
Measurement
at UCR
27/04/2011 15Pascal Debu - CEA/DSM/IRFU
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Yield of o-Ps : comparison CERN/UCR
16
Measurement
at CERN
Measurement
at UCR~ 5.6 x 1016 e+ cm-2s-1
~ 3.5 x 105 e+ cm-2s-1
No loss in conversion efficiency in spite of the 1011 intensity factor
e+ flux
x
~1011
0 1 2 3 4 5 60
10
20
30
40
Inte
nsity o
f th
e 1
42 n
s
com
ponent (%
)
Positron energy (keV)
Cb 44
CTACl-0.22 Saclay
1000 rpm
27/04/2011 Pascal Debu - CEA/DSM/IRFU
L.Liszkay et al., Appl. Phys. Lett. 92 (2008) 063114
D. B. Cassidy et al.,Phys. Rev. A 81 012715 (2011)
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H+ production
27/04/2011 Pascal Debu - CEA/DSM/IRFU 17
p + Ps → H + e –
H + Ps* → H+ + e –
SiO2
coating
fast extraction from trap
tube geometry to keep density
(SiO2 reflects Ps)
Dump 1011 e+ in
Ps converter
in < τPs=142 ns
e+ trap
accumulate few 1010 e+
during p filling ~ 20’
Linac
108 slow e+/s
RIKEN test :
1.3 1010 e- / 75 ns
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Cross-sections on PS
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p + Ps H + e+
σ ~10-15 cm2
J. P. Merrison et al., Phys. Rev. Lett. 78, 2728
(1997)
2 5 10 20 50 100
Ep [keV]
H + Ps H- + e+
EH = 6 keV in Ps frame
σ ~10-16 cm2
H.R.J. Walters and C. Starett, Phys. Stat. Sol. C, 1-8
(2007)
EPs [eV]
if fraction of Ps
excited to n=3
expect × ~ 10
107 p
1012 Ps/cm2}
8 104 H
8 H+2.5 x1010 e+
from trap
AD FacilityCERN
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Gra
vity m
easure
ment
e+ Production
& Accumulation fast H & H + slow H + slow H
1- 6 KeV
Photo
detach
12
137
8
Ps dense6
Ps → Ps*Target2
LINAC1
Moderator/
Collector
e+ ~ MeV→eV
3
Penning Trap
e+ ~meV
4
5
p
Penning Trap ELENA
H+ Trap
Paul Trap
Be+
laser cooling
9
10
11
ε=10-4
ε=10-2-10-4
ε=0.5
ε=10 ?
ε=0.35
Synoptic Scheme
27/04/2011 19Pascal Debu - CEA/DSM/IRFU
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H+ cooling
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• Segmented RF Paul Trap, well depth ~1 eV
• Sympathetic cooling using Be+ ions
Laser cooled Be+ ions
Coulomb interaction of H+ and Be+
H+ capture
trapBe+ trap
Cooling laser
• Be+ Doppler cooling
Temperature ~ 1 mK
• Be+ sub-Doppler cooling
Temperature 4.5 or 9 μK
NIST group
M. D. Barrett, …, D. Wineland, PRA 68, 042302 (2003)
Sympathetic cooling of 9Be+ and 24Mg+ for quantum logic
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Photo detachment
H+ binding energy 0.76 eV => pγ ~ 0.76 eV/c
Recoil due to absorption: vrecoil = pγ / mH = 0.2 m/s =>
4 cm for 0.2 s fall
Recoil due to e+ emission: γ very close to threshold
Ec = Eγ – 0.76 => ~ 1 m/s for Ec = 10 μeV
vrecoil 2meE c
mH
27/04/2011 21Pascal Debu - CEA/DSM/IRFU
H free fall detection
-ejected e+ direction => sign(vz)
-arrival position x,y (mm) => vx, vy
-TOF (140 ms)
=> cross-check of initial temperature
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Efficiencies
2208/04/2010 P. Debu - CS P2I
Rate could be improved a lot with:
-Higher energy Linac (close to 10 MeV)
-ELENA upgrade of AD at CERN
Electrons
Linac frequency (Hz) Ie- (mA) Ie- /pulse (mA) pulse length (s) Ne- / pulse Ne
-(s
-1)
200 1.40E-01 1.75E+02 4.00E-06 4.38E+12 8.75E+14
Positrons
ε (e- e+) ε (transport) ε (moderation) Ne+fast / pulse Ne+ fast (s-1
) Ne+ slow / pulse Ne+ slow (s-1
)
1.50E-04 0.8 1.00E-03 5.25E+08 1.05E+11 5.25E+05 1.05E+08
Positron Storage
ε (trapping) accum. time (s) Ne+ stored
0.2 1200 2.52E+10
Positronium
ε (e+ Ps) volume tube (cm3) Ps density (cm
-2) ε (excitation)
0.35 0.01 8.82E+11 10
H
Np / pulse σ(p+Ps H) σ(H+Ps H+) NH NH
+
1.00E+07 1.00E-15 1.00E-16 8.82E+04 7.78E+00
every ~ 20 minutes
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Perspective:
towards a higher precision on g ?
23
Gravitational quantum states of Antihydrogen
A. Yu. Voronin, P. Froelich, and V. V. Nesvizhevsky,
Phys. Rev. A 83, 032903 (2011)
• H Source:
• very low temperature
• high phase-space density
• compact system
• Improve the precision on g with the spectroscopy of
gravitational levels of H : similar method as for UCN
neutrons (GRANIT spectrometer)
only few events needed to reach ~10-3 precision !
27/04/2011 Pascal Debu - CEA/DSM/IRFU
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