1. The AE g IS experiment at AD
Antimatter Experiment: Gravity, Interferometry, Spectroscopy
Gemma Testera (INFN- Genova) on behalf of the AEGIS collaboration
CERN SPSC meeting January 2009
New experiment at AD (Antiproton Decelerator)
Direct test of the validity of the Weak Equivalence Principle for antihydrogen
June : proposal submitted to SPSC
October : presentation to the SPSC
January : recommendation for approval from SPSC
2008 : CERN discussion about the long term future of AD
Dec : approval from the Research Board of the long term running of AD and of AEGIS

2. The AE g IS collaboration
LAPP, Annecy, France
D. Sillou
UCBL Lyon, France
P.Nedelec
Queen’s U Belfast, UK
G. Gribakin, H.R.J.Walters
CERN
M. Doser, A. Dudarev, D. Perini (+ support from T. Eisel, F. Haug, T. Niinikoski)
INFN Genova, Italy
C. Carraro, V. Lagomarsino, G. Manuzio, G. Testera, S. Zavatarelli
MPI-K Heidelberg
C. Canali, R. Heyne, A. Fisher,A. Kellerbauer, C. Morhard, U. Warring, C.
INFN Firenze, Italy
G. Ferrari, M. Prevedelli, G. Tino
INFN Milano, Italy
I. Boscolo, N. Brambilla,F. Castelli, S. Cialdi, L. Formaro, A. Gervasini, M. Giammarchi, F. Leveraro, A. Vairo
INR Moscow, Russia
A.S. Belov, S. N. Gninenko, V. A. Matveev, A. V. Turbabin
ITEP Moscow, Russia
W. M. Byakov, S. V. Stepanov, D.S. Zvezhinskij
Kirchhoff Inst. Of Phys.,
Heidelberg, Germany
M. Oberthaler
Politecnico Milano, Italy
G. Consolati, A. Dupasquier, R. Ferragut, P. Folegati, F. Quasso
New York Univ. USA
H.H. Stroke
Univ. Oslo, Norway
O. Rohne, S. Stapnes
INFN Pavia-Brescia, Italy
G.Bonomi, A. Fontana, A. Rotondi, A. Zenoni
IRNE Sofia, Bulgary
N. Djurelov
Czech Tech. Univ, Prague, Czech Republic
V. Petracek, D. Krasnicky, M. Spacek
INFN Padova-Trento, Italy
R.S. Brusa, D. Fabris, M. Lunardon, S. Mariazzi, S. Moretto, G. Nebbia, S. Pesente, G. Viesti
INP Minsk, Belarus
G. Drobychev
ETH Zurich, Switzerland
S.D. Hogan, F. Merkt
La. Aime’ Cotton, Orsay, France
L. Cabaret, D. Comparat
Qatar University
I. Y. Al-Qaradawi

3. The AE g IS physics goals
Primary goal: measurement of the Earth gravity acceleration g
on antihydrogen
first direct measure of WEP validity for antimatter
direct tests of the EEP only involve matter
high precision limit for WEP violation on matter system
validity for antimatter via (debatable) indirect arguments
no direct measurement on antimatter
WEP violations for antimatter possible in some quantum gravity model
Precision : first goal 1% with 105 antihydrogen atoms
higher accuracy in the future
Additional physics interest : - high precision antihydrogen spectroscopy (CPT tests)
- positronium physics (as by product)

4. The AE g IS experimental method
a) production of a cold beam of antihydrogen (T~100 mK)
• collect extremely cold antiprotons (T~0.1K) in a trap
Accumulate a cloud of positrons in a trap: (or more) in some minute
Produce ground state positronium sending the e+ into a nanoporous target :
produce Rydberg positronium via laser excitation
form cold (100 mK) antihydrogen atoms by the charge exchange process
accelerate the antihydrogen atoms to ~ few 100 m/s using electric fields
Demonstrated with Hydrogen by members of AEGIS (ETH group)
b) get g through a measurement of the beam deflection with
a Moiré deflectometer
AD: 5 MeV pbar
Hundreds KeV
after a foil
Positron beam
Catch the low energy fraction of the pbar
Cool inside the trap: 10-5 eV (100 mK) Ps Ps Ps Ps
Positronium emission

5. The AE g IS experimental method
Moire’ deflectometer and detector g
Cold antiprotons
Porous target
The distribution of the vertical coordinates in the detector position shows a spatial modulation
Extract g from this modulated distribution
Use a position sensitive antihydrogen detector e+
Time to prepare pbar and e+: few hundreds sec
Pulsed Antihydrogen production
antihydrogen/(AEGIS cycle)

6. The Moiré deflectometer : principle of operation
Counts vs vertical coordinate
x/a
Simulations of the experiment x x
L=40 cm
L=40 cm
a=80 mm
Grating period = 80 mm
Grating size = 20 cm (2500 slits)

7. From the AE g IS proposal to a technical design1
AD antiproton
beam 2 3 5 4 6
1 e+ accumulation : 300 K
2 e+ transfer : from 300 K to 4.2K
3 pbar, e+ catching : 4.2 K
4 instrumentation:
5 antihydrogen formation : 100 mK
6 measurement : 4 K -10 K 7

8. The overall design is well advanced
CERN group

9. The design of the cryostat
SINGLE cryostat housing both the magnets (5T- 1T) and the traps
(two cryostats in the proposal)
Interfaces toward room temperature in the instrument middle region
(laser access, particle diagnostic)
Dilution refrigerator able to reach < 100 mK in the Hbar formation region
(estimated cooling power >500
Not standard system: Design&Realization by members of the collaboration
(CERN group)

10. Cooling of trap electrodes in the antihydrogen formation region
CERN group
Development of a suitable Mixing Chamber (3He and 4He) as part of a Dilution Refrigerator to provide cooling at 100 mK of the cold trap region.
Challenges:
Design of cold region to minimize heat loads from thermal radiation and residual gases.
Minimize heat loads from instrumentation and measurement region.
Limited available space
Optimization of heat transfer from electrodes of UCT to the phase boundary (3He /4He) in the mixing chamber with very small temperature gradients (DT<50 mK)
Electrical insulation between the 5 electrodes and other parts and equipment (up to 1kV)
Currently 2 different approaches for efficient heat transfer are under investigation:
Rod electrically insulated using Al2O3 (Alumina)
Sandwich composed of Cu-In-Sapphire-In-Cu

11. The AE g IS superconducting magnet
CERN group
Key points about the magnet design
Long particle storage time requires high field homogeneity: (DB/B : )
High antiproton catching efficiency : high field (5T)
Rydberg atoms manipulation difficult in high B: 1 T in the Hbar formation region
B value in the transition region influences the particle transfer efficiency
Several correction coils to tune the field are included
Anti-coils to reduce the field in the measurement region
Design completed
SC wires identified
ready to place the order
Winding process can begin at CERN during summer 2009

12. More than 50 cm with about 10-4 homogeneity

13. The positron accumulator: “Surko type”
22Na source: > mC
Moderation through solid neon
Accumulation in trap
Buffer gas cooling
3 108 e+ in few minutes
B= T

14. 4 stages positron accumulator scheme : under study
INR Moscow group
Paper in preparation
INR-LAPP-UBL Groups
Basic goals
Longer e+ accumulation time
Better efficiency
Improve the vacuum interface with the main system

16. Positron accumulator
Deflectometer & cryostats
Racks
Laser hut
Laser table

17. Positron injection in the main magnet
Prague & INFN Genoa groups
e+ accumulator 2m
This region has to be free for the g measurement 5T 1T 1T
AD antiprotons
3D Magnetic field calculations with OPERA3D software
Magnetic transport line : 5 T fringe field + additional coils
Particle tracking
Design of the transfer line in advanced status
The delicate point : interference with antiprotons degrading foils
Discarded option

18. e+ e+

19. The AEGIS trap design : the traps in the high (5T) field
INFN Genoa group
B= 5 Tesla
Antiproton and e+ trap on the same axis (not parallel traps as in the proposal)
Antiproton main energy degrader: foil ..
has to be movable to allow the e+ injection
Pbar and e+ radial compression, preparation to transfer
AD-AEGIS vacuum
separation foil
Pbar catching &e- cooling
antiprotons AD
e+ from the accumulator

20. The traps and the particle manipulation in the interaction region (B=1T) : from a single trap to two parallel traps
Antiprotons on axis
“Standard” transfer from large to “small trap”
Ultracooling (electron cooling:tuned circuits
+radiation) in the 100 mK region e+
pbar
(J. R. Danielson and C. M. Surko
Physics of Plasmas 13 (2006), ) e+
pbar
positronium
Excitation of diocotron motion of e+
Controlled jump off axis
Off axis injection
TESTs in progress in Genoa (AEGIS member)

21. The detector of the antihydrogen formation
We will re-use the ex - ATHENA antihydrogen detector
Readout electronics ready
Tests of the detector already scheduled in the next months (Pavia-Brescia &Padova groups)
The mechanics has to be rebuilt (Padova group)
Works at K
Mount it around the ultracold 100 mK trap: a proper thermal shield is under study
Replace some CsI crystals with YAP scintillators
(fast light output, high yield at low T)
detection of the Ps formation : 142 ns decay time
Time to prepare pbar and e+: few hundreds sec
Pulsed Antihydrogen production
Antihydrogen produced within msec: AEGIS will directly measure the antihydrogen velocity by time of flight

22. Detector 80 K
Vacuum pipe 4.2 K
Solenoid 4.2 K
Mixing chamber zone 0.1 K

23. Charge exchange cross section (CTMC calculation)
INFN Genoa group
Cross section cm2
High cross section
Small effects due to 1 T magnetic field (new result, not included in the proposal: publication in preparation)
Ps velocity of some tens Km/sec : about 100 K

24. Positronium formation in nanoporous insulators
Implanted positrons with KeV energy scatter off atoms and electrons, slow to eV in few ns
Positronium formation by capture of electrons from collisions
Positronium energy: few eV
Accumulation of positronium in voids
If pores are interconnected orthoPs diffuses out of the film
Positronium loses its energy in collision with the pore walls
Positronium cooling and possible thermalization with the target
AEGIS requirements:
High yield from a cryogenic (100 mK) target
Velocity of Ps corresponding to about 100 K: NOT complete thermalization

25. Ps cooling in nanoporous materials at low temperature: model
AEGIS Trento group
Classical model for collisions : ultimate Ps temperature is set by the target temperature
Quantum model : Ps in a infinite potential well
phonon creation and destruction
T(K)
Minimum Ps temperature achievable through collisions: it can be higher than the ground state one.
Ground state Ps energy: it depends on the pore size:
higher than the target temperature
Ps cooling time: about 10ns < oPs lifetime
Ps emission direction : not isotropic !
this will be of help in AEGIS
Pore size (nm)
positronium
pbar

26. Realization of ordered nanochannels in silica
AEGIS Trento group
To obtain nanochannels in silica, silicon has been etched.
Pore diameter around 8 nm
Pore diameter around 10 nm
Pore diameter around 12 nm
Pore diameter around 14 nm
Si p-type
Ohm/cm
current 10mA/cm2
15 min
Changing these parameters, the pore diameter and density can be changed.
Scanning electron microscopy images

27. Experimental results about the oPs yield: SiO2 target
Aegis Tn group
Optimization of the target production
Yield from cryogenic tyargets
S. Mariazzi et al
Applied Surf. Science 255 (2008) 191
oPs fraction (%)
oPs fraction (%)
e+ implantation energy (KeV)
e+ implantation energy (KeV)
In progress: measurement of the positronium velocity distribution and direction

28. Experimental results about the yield: Al2O3 target
Ordered channels in Al203
Member of AEGIS &coworker LAPP,INP groups
Samples annealed at 850 0C:
22 % of the injected positrons forms Positronium escaping in vacuum
Samples annealed to 560 0C: no Ps formation

29. Ageing measurements of the Ps converter
AEGIS Poletecnico Milano
a) Electron beam facility goals:
Radiation damage measurements on the Ps converter with electrons in the same energy range of the impinging positrons;
Fast measurements due to (high flux of electrons)
b) Electron beam facility :
Electron source (Tungsten wire) 10 mA at 2.5 keV
magnetic guide
target support and detectors,
UHV system. 29

30. Ps excitation with 2 laser pulses
AEGIS Milano&Lab. Aime’ Cotton groups
n = 15 – 35 (1709 – 1656nm)
Dl = 4nm
5 ns
120 mJ n
205 nm
 = nm
5 ns
20mJ 3 1
R&D
Commercial Laser
1700nm
Il sistema laser per l’eccitazione del livello 3 al livello n consiste di due parti. Un OPG (optical parametri generator) che consiste in un cristallo di niobato di litio periodically poled il quale viene pompato con un impulso da 1064nm e genera la lungezza d’onda richiesta. L’impulso viene poi amplificato da un OPA (optica parametric amplifier) che consiste in un cirtsallo di noibato di litio pompato da un impulso a 1064nm.
1064 nm
OPG
1064 nm
3000nm
Nd:YAG
PPLN 4cm
OPA
LN 1cm

31. LASER
OPA
Spatial filter
OPG

32. Ps excitation model 93m J/cm2 1mJ/cm2
Member of AEGIS
Two pulses: 5 ns 1 3
Doppler broadening T=100 K
93m J/cm2
1mJ/cm2 3
20-30
Motional Stark effect
Energy distance between unperturbed n states
Stark broadening
Doppler broadening
Expected excitation efficiency: 30%
Ionization limit

33. OPG+OPA experimental results
Energy out vs Energy in
The PPLN crystal allows to cover
all the spectrum (fron n=12 up to the
ionization)
Damage effect of the crystal
Required energy
Dl ~ 4nm
Aegis Milano group

34. Toward ultracold (100 mK) antiprotons
Antiprotons in trap cannot be directly cooled to 100 mK
Cool antiprotons by collisions with a partner particle stored in the same trap
that can be cooled
Negative ions: Os-
electrons
Laser cooling of Os-
Ultimate temperature :240 nK
Resistive cooling with a resonant tuned circuit + radiation cooling
e- antiproton L C
A demonstration of laser cooling of negative ions is needed
Experiment in progress at MPI (members of AEGIS)

35. The MPI setup for negative Osmium ions trap and laser cooling
A. Kellerbauer et al.

36. Progress toward negative ions laser cooling
U. Warring et al, Accepted by Phy. Rev. Lett.
(Member of AEGIS)
Precise measurement of the transition frequency of Os-: two order of magnitude improvement
Superimpose a Os- beam and a laser beam
Apply an electric field to detach the electrons in the excited ion
Scan the frequency of the laser

37. AEGIS time schedule
Begin construction (magnet, cryostat, e+ accumulator, traps )
Installation in the zone
2011 and Run with and without antiprotons (e+ commissioning)
(catch, cool &transfer pbar , e+ accumulation and transfer)
Complete construction and installation
(antihydrogen detector, laser installation)
Rydberg positronium&Hbar formation
Cooling antiprotons to 100 mK
Optimization of the antihydrogen beam
2014, 2015 … Run with the grating system and the position sensitive detector
We expect to ask for the first beam time in 2011
Beam time request : 1/4 of the available AD time for commissioning and physics
Details of the schedule depend on the funding availability (pending requests)

38. AEGIS group expertise: summary
Positrons and positronium
LAPP, Queen's Univ., Polit. di Milano ,INR, ITEP, Univ.&INFN Trento, Univ. Qatar, UCBL, IRNE, INP
Phys. and technology of charged particles in traps
INFN-Genova, MPI
Physics of Rydberg atoms
Lab. Aime' Cotton, Lab. Chem Phys. (ETH)
Laser physics and technology
INFN -Milano, INFN-Firenze, Lab. Chem. Phys. (ETH), Lab. Aime' Cotton
Moire deflectometer
Kirchhoff Inst. of Physics (Heidelberg)
Acceleration-deceleration of Rydberg atoms
Lab. Chem Phys. (ETH)
Atom Interferometry
INFN-Firenze
Cryogenics
New York University, CERN
Simulation of antihydrogen detectors
INFN-Pavia
Montecarlo simulation of the AEGIS experiment
INFN-Genova
Particle detectors
INFN Padova- Czech Tech Univ.- Univ. Oslo
DAQ and control
INFN- Genova, INFN-Pavia
SC and normal magnets
CERN
e+ transport
Czech Tech Univ, INFN Genoa
Mechanics

39. Conclusions Full CERN approval : dec 2008 Activity in 2008
Technical design of the experiment
Continue or begin R&D on critical items
We are ready for construction
Already submitted funding requests :
Pulsed (quasi CW) Lyman alpha source : Lab. Aime’ Cotton
Development of the Antihydrogen Position Sensitive Detector : Oslo group
Grating development &Construction : Kirchhoff Inst. Heidelberg
Positron&Positronium : INR Moscow
AEGIS R&D experiment recognized by INFN
Funding discussion with INFN in progress

40. The Moiré deflectometer : principle of operation
Counts vs vertical coordinate
x/a
Simulations of the experiment
very high statistics x x
L=40 cm
L=40 cm
a=80 mm
Grating period = 80 mm
Grating size = 20 cm (2500 slits)

41. Moire’ deflectometer: simulation
Distribution of antihydrogen vertical position x modulo the grating unit a
1500 detected antihydrogen
Vz= 300 m/s
Ideal detector
Time of flight d
Grating period
x/a
Expected position of the minimum count if g=0

42. Data analysis: use of proper digital filter
D=0
F(D,x) 1
x/a
: measured vertical position of every Hbar
Total number of particle going thorough
a third grating vertically shifted by D
D/ a

43. We do not need a collimated or point like antihydrogen source…..
Ideal detector resolution
Antihydrogen position (before filtering)
Perfectly collimated source
x/a
Point like source
Transverse energy: 100 mK
x/a

44. …we do not need a point like antihydrogen source …
Extended source
Source size (cm) >> grating size
Transverse energy: mK
x/a
The gravity induced shift does not depend
Antihydrogen radial velocity (it determines the grating and detector size)
Source size
Source vertical position
Atom interferometer: it requires high beam collimation

45. We do not need a monochromatic beam
dN/dT2
Distribution of T2
D/ a
ms2
dN/dv
Monocromatic source 300 m/s
Particles with T2 ( and vz ) distributions shown in the plots
m/s

46. We do need a high resolution position sensitive detector
10 m resolution
17.5 m resolution N
2 p D
2 p D
2 p D3

47. Antihydrogen n
From n=20 Ps*
vPs* = 104 m/s
vPs* = m/s
vPs* = m/s

48. Ps