CERN May 2014 Mike Charlton Physics Swansea University UK Antihydrogen Physics with ALPHA Antihydrogen Physics with ALPHA CERN May 2014 Summary of the Talk Introductory Remarks The Hydrogen ID: 794167
Download The PPT/PDF document "Antihydrogen Physics with ALPHA" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Antihydrogen Physics with ALPHA CERN – May 2014
Mike Charlton, Physics,
Swansea UniversityUK
Antihydrogen Physics with ALPHA
Slide2Antihydrogen Physics with ALPHA CERN – May 2014
Summary of the Talk
Introductory Remarks - The Hydrogen/
Antihydrogen Playground
Antihydrogen Production: Formation Processes
Antihydrogen
Production for Trapping
ALPHA
-
Antihydrogen
Trapping and Physics
ALPHA
-
What’s Next?
Slide3Antihydrogen Physics with ALPHA CERN – May 2014
The Hydrogen/
Antihydrogen Playground
From R.
Ley
, Appl. Surf. Sci.
194
(2002) 301
1S-2S transition in H;
Parthey
et al.
PRL 107 (2011) 203001
2 466 061 413 187 035(10) Hz, or 4.2 parts in 10
15
Ground State Hyperfine transition in H; Essen
et al.
Nature 229 (1971) 110
1 420 405 751.7667(9) Hz, or 6.4 parts in 10
13
Slide4Antihydrogen Physics with ALPHA CERN – May 2014
The Hydrogen/
Antihydrogen Playground
Gravity
… plus Charge Neutrality …
Slide5Antihydrogen Physics with ALPHA CERN – May 2014
Antihydrogen
Production: Formation Processes
Plasma self electric field
Plasma parameters
Tangential drift speed
low
high
> 10
3
s
-1
Slide6Antihydrogen Physics with ALPHA CERN – May 2014
Antihydrogen
Production: Formation Processes
The TBR is a quasi-elastic encounter of 2 positrons in the vicinity of an antiproton. Energy exchange ~ kBTe, which will be the same order of the binding energies.Thus, these are very weakly bound states which are strongly influenced by the ambient
fields. Many are field ionized.
Antihydrogen binding energies
as the atoms leave
the positron plasma
n
e
= 10
15
m
-3
(x);
n
e
= 5 x 10
13
m
-3
(+)
c.f.
Antihydrogen binding energies
on detection
n
e
= 10
15
m
-3
(+); 5 (○), 2 (
Δ
) and 1 (□) x 10
14
m
-3
and 5 x 10
13
m
-3
(x)
Results of simulations:
Jonsell
et al.
J.Phys
B. 42 (2009) 215002
Slide7Antihydrogen Physics with ALPHA CERN – May 2014
Antihydrogen
Production: Formation Processes
Radial distribution of antihydrogen formation positions at different time intervals
Te
= 15 K
n
e
=
10
15
m
-3
n
e
=
5 x10
13
m
-3
short (x), medium (
Δ
) and long (□) times
NB at 10
15
m
-3
a “long” time is > 1ms
Repeated antihydrogen formation and destruction cycles in the plasma transport the antiprotons to the outer edge of the plasma
Results of simulations:
Jonsell
et al.
J.Phys
B. 42 (2009) 215002
Slide8Antihydrogen Physics with ALPHA CERN – May 2014
Antihydrogen
Production: Formation ProcessesSo … want high positron density and low temperatures to drive 3-body reaction to form antihydrogen efficiently, but:-
Field ionization …Cross-field antiproton transport driven by the antihydrogen production mechanism …Higher tangential drift speeds at higher radius and density …To say nothing of plasma expansion effects, which are most deleterious at high densities …
Slide9Antihydrogen Physics with ALPHA CERN – May 2014
Antihydrogen
Production for TrappingWe have machines to manipulate and capture positrons and antiprotons using a raft of long-established techniques
These are then fed into a central apparatus where – eventually – they are mixed to form antihydrogen. A small fraction of the anti-atoms (to date at least) may then be trapped …The manipulations of the positrons and antiprotons before, and upon, mixing are crucial to this achievement
Slide10Antihydrogen Physics with ALPHA CERN – May 2014
Antihydrogen
Production for Trapping
Classic
Ioffe
-Pritchard Geometry
Solenoid field is the minimum in B
B
quadrupole
winding
mirror coils
N.B.
Well depth ~ 0.7 K/
T for the ground state
THE CHALLENGE
ALPHA’S
Octupolar
magnet for radial field minimum
Slide11Antihydrogen Physics with ALPHA CERN – May 2014
Antihydrogen
Production for Trapping
From the ADe+ from accumulator
3-layer silicon antiproton annihilation vertex detector surrounding the mixing region is not shown
Slide12Antihydrogen Physics with ALPHA CERN – May 2014
Antihydrogen
Production for Trapping
Slide13Antihydrogen Physics with ALPHA CERN – May 2014
Antihydrogen
Production for Trapping
Sympathetic compression of an antiproton cloud by electrons – uses rotating electric fields
Andresen
et
al., PRL, 101
(2008) 203401
To reduce tangential drift speeds at high radius and promote overlap with the positron plasma
Slide14Antihydrogen Physics with ALPHA CERN – May 2014
Antihydrogen
Production for Trapping
Andresen et al., PRL 105 (2010) 013003
1040 K
325 K
57 K
23 K
19 K
9 K
Typically (9
±
4) K is lowest achievable at the lowest well available at which (6
± 1) % of the initial antiprotons remain
Evaporative cooling of antiproton and positrons to lower temperatures prior to mixing
Slide15Antihydrogen Production for Trapping
Antihydrogen Physics with ALPHA CERN – May 2014
Andresen et al. PRL
106 025002 (2011)
Chirped driven harmonic oscillator
Autoresonant
injection of antiprotons in to the positron plasma to achieve robust mixing with minimum added kinetic energy
Slide16Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
30,000
pbars at 200K
2M positrons at 40 K (
evaporatively
cooled)
Auto-resonant injection and mix for 1 sec.
Clear the charge particles
Turn off the neutral trap (1/e time ~ 9 ms)
Search for
pbar
annihilations from
Hbar
(bias fields to eject any charged particles still trapped)
Neutral trap depth ~ 0.5 K
Slide17Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
Searching for trapped antihydrogen Shut off magnetic minimum trap (1/e time ~ 9 ms) Interrogate output of vertex detector in 30 ms time window after
the shut off Apply cuts to data to reject cosmic ray events
a) Antiproton annihilation
b
) Cosmic ray
Slide18Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
Initial success – just 38 events
Published in Nature 468 (2010) 673
Slide19Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
309 events – Nature Physics 7 (2011) 558
Slide20Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
Time release distribution and various fits
Slide21Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
Magnetic Field map of the antihydrogen trap
Note the small red box near the field minimum, close to 1 T
Slide22Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
Slide23Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
On resonance – 15 MHz scan width for 15 s
each – 6 repeats
Slide24Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
On resonance – 15 MHz scan width for 15
s
each – 6 repeats
Off resonance – B shift
Slide25Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
On resonance – 15 MHz scan width for 15
s
each – 6 repeats
Off resonance – B shift
On resonance – frequency shift
Slide26Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
Extra annihilations on resonance – the microwaves force the
antihydrogen
into the
untrapped
states
First observation of a resonant quantum transitions in an anti-atom: Nature 483 (2012) 439
Slide27Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
Microwave experiments (ALPHA-type) limited by:-
Statistics (no
lineshape
scan)
B-field and variation across “sample”
Magnetometry
(in-situ) issues …
Slide28Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
F = M
g
/M, ratio of
grav
. to inertial mass
F = 1
F = 100
Analysis of the up/down annihilation positions versus time (red dots, data: green dots, simulations)
during the magnet shutdown
Slide29Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
ALPHA’s
reverse cumulative average analysis
Data
Red:
y
-direction
Green:
x
-direction (for comparison)
Simulations
Dash: “antigravity” at given |F|
Line: gravity at given |F|
Grey bands: 90% confidence limits on simulations
Slide30Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
Possibilities with cooled
antihydrogen
atoms … reverse cumulative averages from simulation
Majenta
: F =-1
Red: F = 0
Green: F = 1
N.B. Field shut down slowed by a factor of 10
Thin black line is fraction escaped versus time
Dark yellow
s/n
(cosmic) > 5 for current trapping rate:
light yellow
for trapping rate x10
Grey bands – 90% conf. limits for F = +/- 1
Slide31Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
Limitations …
Statistics – signal-to-noise at long times
Systematics
regarding magnetic effects; trajectories are complicated – need simulations to extract F
Need cooled
antihydrogen
to get near F = 1; probably can’t get much further
Slide32Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
To be published
Electric fields used for “
Bias-Left
” and “
Bias-Right
” configurations
Experimental data for
Bias-Left
and
Bias-Right
Slide33Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
Simulation of
z
-annihilation points for an
antihydrogen
charge,
Q
Effective potential,
U
, used to derive
Q
for
E
to left and right
Experimental data
<
z
>’
s
are average annihilation positions with fields to left and right
Replace approximate result for
Q
with value of “sensitivity to charge” from simulation
s
= - (3.31 +\- 0.04)
x
10
-9
mm
-1
To be published
Slide34Antihydrogen Physics with ALPHA CERN – May 2014
ALPHA
Antihydrogen Trapping and Physics
Limitations and possibilities…
Statistic and
systematics
…
Laser cooling to 20
mK
will improve by a factor of about 10 (lower neutral trap, lower mirror coil fields)
Stochastic heating/acceleration … possible to achieve |
Q
| ~ 10
11
-10
-12
: see preprint:-
To be published
Slide35ALPHA – What’s Next?
Antihydrogen Physics with ALPHA CERN – May 2014
Layout of ALPHA-2
Working on new apparatus to allow laser access for 1S-2S 2-photon transition (ALPHA-2) and to incorporate antihydrogen laser cooling
Long term goals of the field
For a discussion of laser cooling in an ALPHA-like trap; see
Doonan
et al.
J. Phys. B, 46 (2013) 025302
Slide36ALPHA – What’s Next?
Antihydrogen Physics with ALPHA CERN – May 2014
Cha
llenges …More trapped antihydrogen! (
cooler positrons)Optics/cavities and cryogenics
Lasers for stringent spectroscopy/cooling requirements – challenging wavelengths
Slide37ALPHA – What’s Next?
Antihydrogen Physics with ALPHA CERN – May 2014
A possible new venture – ALPHA-g: a vertical ALPHA with a long-term vision of performing antimatter interferometry
For discussion of the concept see: Hamilton et al.
PRL 112 (2014) 121102
Slide38ALPHA – What’s Next?
Antihydrogen Physics with ALPHA CERN – May 2014
A very bright and busy future awaits …
CERN has started work on
ELENA
an extra ring to decelerate antiprotons to about 100
keV
– this will increase our capture efficiency for low energy antiprotons by a factor of around 100.
Slide39Antihydrogen Physics with ALPHA CERN – May 2014
Acknowledgements – ALPHA circa 2013-4
University of Aarhus:
J.S.
Hangst
, C. Rasmussen
Auburn
University/Purdue University
:
P.H.
Donnan
, F
.
Robicheaux
University of British Columbia:
N.
Evetts
, A. Gutierrez
, W.N.
Hardy,
T.Momose
University of Calgary:
T. Friesen,
R.I. Thompson
University of California, Berkeley:
M.
Baquero
-Ruiz, J.
Fajans
,
A. Little, H. Mueller, C
. So,
T. Tharp, J.S
.
Wurtele
CERN:
E.
Butler – now a JRF at Imperial College
University of Liverpool:
J.T.K. McKenna, P
. Nolan, P.
Pusa
University of Liverpool/Cockcroft:
S.
Chattopadhyay
University of Manchester/Cockcroft:
W.
Bertsche
NRCN
, Negev:
E.
Sarid
Federal
University of Rio de Janeiro:
C.L.
Cesar, D.M.
Silveira
Simon Fraser University :
M.D.
Ashkezari
, M.E. Hayden
York University, Toronto :
C. Amole, A. Capra, S
.
Menary
Swansea University:
M
. Charlton,
D. Edwards, S.J
. Eriksson,
C.A. Isaac, S. Jones, N
. Madsen,
M.
Sameed
, D.P
. van
der
Werf
Stockholm University :
S.
Jonsell
TRIUMF
:
M. C. Fujiwara
,
D.R. Gill, L.
Kurchaninov
, K.
Olchanski
, A. Olin,
S.
Straka