Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Antimatter Plasmas
Cliff Surko*
University of California
San Diego
* Supported by the NSF AMO program; previous support from
AT&T Bell Labs, ONR, the NSF/DoE Partnership and DTRA.
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
The Mirror World of Matter and
Antimatter
positron ↔ electron
antiproton ↔ proton
Positrons
e- + e+ => gamma rays
2γ* (S = 0) or 3γ (S = 1)
(2γ decay: εγ = mec2 = 511 keV)
Antiprotons
p + p => shower of pions (e.g., π+, π-)
Antihydrogen (pe+) : EB = 13.6 eV (stable)
Positronium atom (e+e-): EB = 6.8 eV
τs=0 = 0.12 ns; τs=1 = 140 ns
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Not-so-small Elephant in the Room
Quantum Field Theories are
symmetric: matter <=> antimatter
But gamma-ray observations =>
antimatter in our universe ~ zip!
We
live in a matter world and
we don’t know why
galactic center
Antimatter
in our world
of Matter
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
materials studies
medicine
PET scans
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Theme of This Talk -
The Plasma Connection
If you want to keep antimatter around, keep it away from matter
Neutral antimatter is hard to confine
So the natural solution is a single-component plasma
Accumulate antiparticles, tailor the plasmas, then tailor
the delivery for specific applications
The focus is on nonrelativistic antimatter - omits laser-produced
relativistic positron plasmas [e.g., Hui Chen, GI.2-3, Tuesday, PM]
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
p
e+
antihydrogen
e+- e- (pair) plasmas
positronium
physics (Ps, Ps2)
Antimatter
-  Exploiting
the Plama
Connection
positron binding
to matter
Ps-atom BEC
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Sources of e+and p
Positrons (energies ~ keV - MeV)
Radioisotopes (18F, 58Co, 22Na)
(portable, or reactor-based)
Electron accelerators (e.g., LINACs)
(ε ≥ 2mec2 = 1 MeV)
Antiprotons
(energies ~ GeV)
Particle accelerators (CERN, Fermilab)
(fast protons: εp ≥ 6 mpc2 ∼ 5.6 GeV)
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Want Low-Energy Positrons
Use “moderators” 100’s of keV → ~ 1 eV
solid neon
(~ 8 K)
copper
22Na
e+ source
fast e+
slow positron
beam (E ~ 1eV)
B
Neon efficiency ~ 1%
50 mCi 22Na ~ 1 pA slow e+
Metals are moderators too
W, Ta, Pt, but efficiency ≤ 0.1 %
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Intense Reactor-Based Positron Beam
FRM II reactor, Munich
γ
Reactor core
γ
γ
platinum moderator
Beam 7 mm FWHM, in 60 G
109 e+/s (~ 100 pA)
C. Hugenschmidt, U. Munich
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Low-energy Antiprotons
The CERN Antiproton Decelerator (AD)
From PS:
13
1.5x10 protons/bunch, 26 GeV/c
2 Injection at 3.5 GeV/c
1 Antiproton
Production
4 Extraction
7
2 - 4( 2x10
x 107 in
in 200
200 ns)
ns
3 Deceleration and
ASACUSA
ASACUSA
Sto
cha
stic
Cooling
(3.5 - 0.1 GeV/c)
Co
olin
g
ATRAP
ATRAP
0
10
20 m
Electron Cooling
ATHENA
ATHENA/
ALPHA
ALPHA
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Trapping Antimatter –
The Start of the Plasma Connection
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
History of Antimatter Trapping
Positrons in a magnetic mirror, Gibson, Jordan, Lauer, PRL 1960 B
Fill with the the radioisotope 19Ne, positrons deposited,
then pump out the radioactive gas.
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Positron Confinement in a Magnetic Mirror Trap
ε ~ 1 MeV
n ≤ 104 cm-3
escaping
-positron
count
rate τ > 10 s
time (s)
(a)  –> (c) increasing neutral gas pressure
(λD ≥ 100 m)
Gibson, Jordan, Lauer, PRL 1960
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
History of Antimatter Trapping
Positrons, magnetic mirror, Gibson, Jordan, Lauer, 1960 Positrons, Penning trap, Schwinberg, Van Dyck, Dehmelt, 1981 Antiprotons, Penning trap, Gabrielse, 1986
Positron plasma, Penning-Malmberg (PM) trap
Leventhal et al., 1989
Merged antiprotons & positrons, ATHENA, ATRAP, 2002
Positrons in magnetic dipole, Saitoh, 2013
A Near-Perfect “Antimatter Bottle”
the Penning-Malmberg Trap
fE
B
×
B
V
E
plasma rotates:
f E = cne /B
V(z)
V
single-component
plasma
z
Canonical angular momentum
No torques ⇒
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
is constant. No expansion!
(Malmberg & deGrassie ‘75; O’Neil ‘80)
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Buffer-Gas Positron Trap
CF4
♦
Trap using electronic
excitation of N2
♦
Positrons cool to 300K
on CF4 in ~ 0.1s
30% trapping
efficiency
Surko PRL ‘88; Murphy, PR ‘92
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Trap Electrodes (~ 1986)
Al Passner, Fred Wysocki & Marv Leventhal Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Al Passner and unidentified “kid”
with B-G Trap ~ 1987
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Commercial Buffer-gas Positron Traps
First Point Scientific, Inc. (R. G. Greaves)
2-stage
BG trap
Commercial & home-built
traps in the U. S.,Australia, China,
U. K., Russia & CERN (4)
source/moderator
two-stage trap
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Shuttle to UHV for Long Term Storage
UHV
high-field trap
plasma cools by cyclotron radiation
p < 10-9 torr
annihilation
negligible
τc ≈ 0.2 s
(positrons
or electrons)
Surko HI ‘97
50cm
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
So We’ve Trapped It, What’s Next?
- More of the Plasma Connection
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Antimatter-plasma Control and Manipulation
Good particle cooling achieved with various techniques
Plasma compression with rotating electric fields
Plasma manipulation using chirped-frequency autoresonance
Trap-based beams from tailored plasmas
narrow energy spreads, time-compression, or
finely focused beams
Merged plasmas (antiproton and positron)
for antihydrogen
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Antiparticle Cooling
Critical for Many Applications
Collisional cooling (positrons; excite rotations and vibrations
in molecules) e.g, CF4, SF6; but annihilation loss
Cyclotron radiation (positrons, or antiprotons sympathetically
cooled by cold electrons); need large B, not so fast
Laser cooling (cool Be+ ions to cool positrons sympathetically);
mK temperatures, but centrifugal separation
Evaporation (positrons or antiprotons); particle loss
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Evaporative Cooling of Antiprotons
9 K (but > 90 % loss)
ALPHA; Andresen et al., PRL 2010
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Increase Density by Radial Compression
with Rotating Electric Fields
“The Rotating Wall Technique”
Vconf
.
B
Vconf
segmented electrode
Apply a torque using a rotating
electric field =>
radial compression for f RW > f E
V = VRW cos[(2πfRW) t + φ]
(Huang, et al., Anderegg, et al., Hollmann, et al., Greaves et al., Danielson et al., 1997 - 2007)
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
central density (109 cm-3)
Density Control Using Rotating-wall Compression (buffer-gas cooling)
fRW = fE
n0 ≈ 17% of the
Brillouin limit, nB
B = 400 G
positron plasma
Glitches due to trap imperfections
nB = B2/2µ0mc2
frequency (MHz)
However, at 5 T, nmax ~ 3 x 1010 cm-3 ~ 10-3 nBrillouin
- This limit is not understood
(R. G. Greaves, in
Danielson et al., RMP, submitted.)
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Positron Plasma Parameters
Magnetic field
Number
Density
Space charge
Temperature
Plasma length
Plasma radius
Debye length
Confinement time
Trivelpiece-Gould modes*
10-3
– 5 tesla
104 - 109
105 - 1010 cm-3
10-3 – 103 eV
10-3 – 1 eV
1 – 30 cm
0.5 – 10 mm
10-2 – 1 cm
102 – 105 s
Diagnostics: modes to measure N, n, T, & aspect ratio
2D CCD images mz
mz
mz
frequency
Dubin PF‘93; Tinkle PP ‘94
Surko AIP ’99, Weber PP ‘08
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Delivery as
Trap-based Beams
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Trap-based Positron Beam
High Energy Resolution
Trap, cool and release:
300 K buffer gas
(kBT = 25 meV)
Retarding potential (V)
Expect Δεtot < 10 meV
with cryogenic (50 K) N2
Gilbert et al., APL (1997)
Δεtot ≈ 40 meV
M. Natisin, 2014
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Chirped-frequencyAutoresonance
For Energy Control
(antiprotons)
B
e+
- eV(z)
ωi!
ω0"
ω f!
locked$$
autoresonace$
!me$
p
E(t)
z
E = E0cos(ωit – αt2)
Use down-chirped frequency
to drive p cloud coherently
out of the well
Fajans, PP 1999
ALPHA PRL 2011
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Down-Chirp Autoresonance for Antiproton Beam Formation
E (eV)
Sweep
ω I → ω f
f(E)
chirp-frequency ω/ω0
ALPHA, Andresen, PRL 2011
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Trap-based Beams – Temporal Compression
“harmonic bunching” using a parabolic potential
0
0
0
-40
-2
Buncher on
Buncher off
-80
-4
-6
- 120
-120
-20
positrons
-10
0
10
time (ns)
20
30
40
time focus
15 ns pulse -> 1 ns pulse
Cassidy, RSI 2006
-8
50
PMT output (mV)
PMT output (mV)
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Trap-based Positronium Beams?
…… Not Yet!
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Physics with Antimatter
e+ - matter interactions
Positron studies of materials
Positron binding to molecules
stable neutral
antimatter
e+
e-
many body
system
Antihydrogen
Ps2 and Bose-condensed positronium
Electron-positron plasmas
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Materials Analysis Using Positron Beams
Positrons provide new techniques and new information
not available using e- beams.
Cliff Surko,
Maxwell Prize talk,
APS DPP,
Oct. 30, 2014
Materials Studies
(defects)
Positron lifetimes in the biopolymer chitosan
Positrons diffuse to defects and annihilate.
Provide information about the nature of the defects.
Inject pulse &
measure
annihilation vs. time
Sample
I
II
III
Chaudhary,
ML 2010
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Positron Defect Studies in the Polymer Chitosan
native polymer:
flexible, shape memory
hydrated:
less flexible, shape memory
SEM
images
cross-linked:
brittle, no shape memory
Chaudhary et al., ML 2010
Atomic Physics
Resonances in Positron Annihilation
on Molecules
a)  Positron approaches molecule with
energy ε – ωCH – εb
b)  Excites molecular vibration ωCH
and drops into well of depth εb
c)  Bound positron has greatly enhanced
chance of annihilation
(a) e+
V(r)
(b)
ωCH
ε
εb
annihilation
rate
Cliff Surko,
Maxwell
Prize talk,
APS DPP,
Oct. 30, 2014
C-H
stretch
mode
εb
ωCH
(c)
Have now measured
binding energies for ≥ 70 molecules
Gilbert PRL, 2002; Gribakin RMP, 2010
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Positron and Electron Binding to Acetonitrile (C2H3N)
p
+
-
N
C
p
p
-
measured: εb = 180 meV
predicted: εb = 135 meV
+
εb = 19 meV
εb = 13 meV
Efforts to better understand e+ - e- correlations and improve
binding energy calculations are in progress.
Positrons: Tachickawa, PCCP 2011
Electrons: Simons JCPA 2008
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Stable, Neutral Antimatter
Antihydrogen
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Why Study Antihydrogen
Some Tests of CPT
Would like to
test all particle
sectors
(e/m)
?
(H)
possible
Precision
Precision
Test gravity too force of matter on
antimatter
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Antihydrogen Experiments at CERN
ATRAP & ALPHA (2005 →)/ATHENA (≤ 2005)
Trapping for spectroscopy, gravity, magnetic moment
ASACUSA
Beam for magnetic moment studies
AEgIS
Beam for gravity test
GBAR
Free-fall for gravity test
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Antiproton Catching & Cooling*
a) Degrading
Solenoid - B = 3 Tesla
Antiprotons
e-
t=0s
Degrader
Cold electron cloud
[cooled by Synchtrotron Radiation, τ ~ 0.4s]
99.9% lost
b) Reflecting
0.1%
E<5kV
Potential
t = 200 ns
c) Trapping
Potential
t = 500 ns
c) Cooling
Potential
[through Coulomb interaction]
Gabrielse, PRL ‘86
t ~ 20 s
~ 10,000 antiprotons per AD pulse"
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Antihydrogen Production
(one scenario)
Nested Penning traps
-125
antiprotons
-100
-75
p, e+ plasmas
trapped, cooled,
RW-compresed
B
-50
0
2
4
6
8
Length (cm)
10
12
~ 108 positrons
Launch ~ 104 antiprotons into mixing region
Mixing time 190 sec
+
+
+
H formed by three-body collisions: p + e + e = H + e
ATHENA/ALPHA (pre-2007)
ATRAP similar
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Trapping Antihydrogen
Ioffe-Prichard Minimum-B OctopoleTrap
ΔB ~ 1 T
=> V ~ 0.6 K
Heroic quench time of superconducting windings ~ 9 ms.
ALPHA, Nature 2010
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Trapping Antihydrogen
(one scenario)
p; dynamically trap 105
Cool with e-; compress
p
3 x 107
Clear e-; evaporatively cool => 104
p @ 100 K
Start with 107 positrons; compress; evaporatively cool => 106 e+ @ 40 K Autoresonantly merge => 6 x 103 H in 1 s
Fast B shutdown (9 ms) to detect H
110 detected out of 200 trials => 0.5 H /trial
(numbers rounded)
ALPHA, Nature 2010
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Trapped Antihydrogen*
Accumulate H,
then quench Ioffe
trap to release.
Trapping rate per attempt
2.5
99% reach the ground state in < 1 s
2.0
1.5
1.0
0.5
0
0
500
1,000
1,500
Confinement time (s)
2,000
120 Quasi-trapped
* ALPHA, Nature 2010
Counts
100
80
ATRAP
similar, Gabrielse, PRL 2012
60
40
100 mK
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Antihydrogen Production and Trapping
Summary
•  ATRAP and ALPHA have trapped ground-state
H
•  gravity test: g mm ≤ 100g * •  magnetic moment µ consistent (± 1%) with that
of hydrogen*
•  charge neutral to q/e < 10-8*
•  optical, microwave, refined g and q/e, and beam
experiments
are in progress
* ALPHA
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Many-Electron
Many-Positron System
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Many Body Physics with Antimatter
The Electron-Positron Phase Diagram
n
e+ - e- liquid
normal /supercond.
density
nMott~ 3 x 1022 cm-3
T ~ 7 x 104 K
PsBEC
BEC
Ps
Ps
BEC
Ps
gas
e+ - e- plasma
Ps2 gas
temperature
(BEC ≡ Bose-Einstein condensate)
8 x 103 K
Yabu, NIMB ‘04
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Quantum Positronium (e+e-) Gas Experiment
spin polarized e+
B = 2.3 T
Pulses of ~ 107 e+ at ~ 1 keV focused to spot on sample; e+ pick up
an e- -> Ps
Porous Si
or Al(1,1,1)
target
D. Cassidy & A. Mills,
U. California, Riverside
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Spectroscopy of Ps2 and Ps
First optical spectrum
of the Ps2 molecule (e+e-e+e–); a many-electron
many-positron system
hν
Doppler shifts
Ps2: 1s – 2p
Ps2
Al(1,1,1)
Cassidy, PRL 2012
High-Rydberg-state Ps (very long lifetimes for materials
and gravity studies)
n = 31; τ ≥ 100 µs
Cassidy PRL 2012
Jones PRA 2014
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Electron-Positron
Plasmas
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Classical
Electron-Positron (“Pair”) Plasmas
Nonlinear
phenomena for T+= T- and n+ = n-
• Heavily damped acoustic mode • Faraday rotation absent
• Three-wave decay processes absent*
• Very strong nonlinear growth and damping processes*
* Tsytovich & Wharton, Comm. on Pl. Phys. (1978)
- - e+ plasmas
Relativistic
e
• Astrophysical relevance
Complementary work
on pair-ion plasmas (e.g.,C60±)
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Plans to Confine e+ - e- (pair) Plasma in
a Levitated Magnetic Dipole
e+
•  Advantages
•  300 s confinement for e-
• Can confine e+ & e-
• Status and plans Injection via E x B plates Use Munich reactor e+ beam
Need ~ 1011 - 1012 e+
- use a “multicell-trap”
(test experiment)
Other possible confinement schemes:
Stellerator
Penning/Paul trap
Magnetic mirror
H. Saitoh, JPCS 2014
T. Sunn Pedersen, NJP 2012
J. Stanja & E. Stenson, Posters BP8: 108 & 109, Monday Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Larger Collections
of Antimatter
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
For Single PM Traps, Space Charge Becomes Prohibitive
plasma space
charge
100 keV
10 keV
1 keV
100 eV
10 eV
1 eV
100 meV
10 meV
1 meV
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Solution: Shield Parallel Cells with Copper Electrodes
- a multicell trap for 1012 positrons
B
e+ in
1 m
3 banks of 7 cells with 5 x 1010 e+ each
1 kV confinement potentials
Move plasma across B using autoresonant diocotron mode*
Surko, JRCP ‘03
Danielson, PP ‘06
* Fajans, ‘99 - ‘01
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Multicell Trap Test Structure
3 off-axis cells
Beam in
diocotron autoresonance
•  ≥ 50% transfer efficiency
•  Need to demonstrate
confinement of kV space charge off axis
Baker, Danielson, et al., PP, sub. ‘14
×
B
-4.0
0.0
x(cm)
+4.0
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Antimatter in the Laboratory
- Plasma Physics is the Driver
Much Progress and Many Opportunities
Ÿ Materials and atomic physics
Ÿ Tests of fundamental physics
Ÿ Antimatter plasmas & BEC Ps
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Outstanding Challenges
•  Rotating Wall compression
–  Density limit at high B?
•  Electron-positron plasmas and Ps BEC
–  Need larger N; and larger n, lower T
•  More efficient sources?
–  Direct capture of MeV positrons?
•  Portable antimatter traps?
–  Likely await improved magnet technology?
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
Thanks
to my collaborators: L Barnes, J. Danielson, D. Dubin, S. Gilbert, R. Greaves, G. Gribakin, C.
Hugenschmidt, E. Jerzewski, M. Leventhal, J. Marler, T. O’Neil, A. Passner,
T. Pedersen, J. Sullivan, M. Tinkle, T. Weber, and J. Young
Thanks too for support from AT&T Bell Labs, ONR, NSF, DOE and DTRA
Cliff Surko, Maxwell Prize talk, APS DPP, Oct. 30, 2014
For references and links
to other work see:
positrons.ucsd.edu
e+
Forthcoming (hopefully) review article:
Plasma and Trap-Based Techniques for Science with Positrons
J. R. Danielson, D. H. E. Dubin, R. G. Greaves and C. M. Surko
Rev. Mod. Phys., submitted.