Nov-14-2003 SLAC EPAC
P. Pérez & A. Rosowsky 1
Intense Slow Positron Source
•Introduction•Science & Frontier Technology •Production of e+
•Competition•Proposal•Request to EPAC
10 MeVrhodotron
target - collector
moderator - buffer gas - trap e+
~ 14 m
Nov-14-2003 SLAC EPAC
P. Pérez & A. Rosowsky 2
Introduction
• Our motivation: detect deviation from gravity inPs or Hbar free-fall
– make a beam of anti-atoms (≠CERN expts.)– use few pbar (expensive)– use many e+ EC ~ eV , D EC ~ 1.5 meV
• e+ factory : today’s proposal
• New applications outside this field for Ne+ > 109 s-1
Nov-14-2003 SLAC EPAC
P. Pérez & A. Rosowsky 3
Making anti atoms• Radiative Recombination (RR) ne ≤ 10 8 cm –3
p + + e – H p – + e + Hbar
• Laser Induced Radiative Recombination (LIRR)p + + e – + hν H + 2hν p – + e + + hν Hbar + 2hν
• 3 Body reactions (3BDY) ne ≥ 10 9 cm –3
p + + e – + e ± H * + e ± p – + e + + e ± Hbar * + e ±
e + + e – + e ± Ps * + e ±
• Charge exchange with Positronium (CXPS)p + + Ps H + e + p – + Ps Hbar + e –
H + Ps H – + e + Hbar + Ps Hbar+ + e –
Matter Anti-matter
SLA
CC
ER
N
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p+ + Ps H + e+
C.M.
20 KeV p– (lab) 10 –15 cm2
H + Ps H − + e+
20 KeV p (lab) 10−17 cm2
1014 Ps at/cm3 10– 4 Hbar +
per incident antiproton
N.Yamanaka & Y. Kino, Phys. Rev. A 65, 062709 P.K. Biswas, J.Phys. B: At. Mol. Opt. Phys. 34 (2001) 4831
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Transform all e+ into Ps in less than 1 ns via 3 body reaction: e + + e – + e ± Ps * + e ±
1014 Ps at/cm3
10– 4 Hbar +
per incident antiproton
20 KeV p ± + Ps target
H/p = Hbar/p– = 0.1
In same Ps target
H + Ps H – + e +
Hbar + Ps Hbar++ e–
H–/H = Hbar+/Hbar =10-3
density (cm-3)
Lif
etim
e (s
)
1 meV
direct annihilation
5 meV20 meV
10-14
10-13
10-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
1
10
10 2
10 3
1010
1011
1012
1013
1014
1015
0.1 ns
1 ns
Plasma temperature
we will be here !
ATHENA 2.5 108 cm-3
e+lif
etim
e in
pla
sma
(s)
1012 1014
plasma density (cm-3)
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Layout scheme
Positronium target :
Few 1012 e ± inside 10-2 cm3
=> Ps density ~ 1014 cm-3
Greaves-Surko traps Target :
aerogel / Si cristal
H, H – or Hbar, Hbar+ ï Free fall expt.
L = 1 cmS = 1 mm2
« = 1200 mm
e– trap
( ~ eV )
e+ trap
( ~ eV )
p+ or p– trap
( ~20 keV )
several minutes to fill e+ trap
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Greaves-Surko trap
Ne moderator: Ec < 1 MeV eV
N2 buffer gas : eV meV
Penning Malmberg trap
Rotating wall
ATHENA : 108 e+
UC San Diego
(7K)
Project to store 1015
within 3 years 1012 1013 e+
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Fundamental Physics expts
• Gravity experiment possible with Ps only– High Rydberg states of Ps can live ~ 1ms – produce thermal Ps atoms (3 km/s max speed) then excited
with Doppler-free two photon techniques – Ps atoms focused by mirror and converge on 1 mm spot– deflection expected from gravity is 50 mm on a 10 m scale – rate of slow positrons needed in order to achieve a 5 s
measurement in a week of run is ~ 109 s-1
• BEC Ps• 511 KeV g ray laser• 3D imaging of molecules
A. P. Mills & P.M. Platzman publications
Nov-14-2003 SLAC EPAC
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Other research & Applications
• e+ e – plasmas Astrophysics– Feed stellarator for low energy neutral plasma study– Relativistic plasmas study on ms to s time scales
• Cold & bright e+ beams materials study– High speed electronics and chips (PALS)– Positron microscopy
• Filling of portable trap with 1012 e+ commercial use (UCSD design)
• « advanced futuristic » projects : energy storage, USAF shuttle propulsion…
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e+ Production and Collection
• Beam energy/intensity : 10 MeV 2~10 mA
• Target geometry : thin foil at grazing incidence ( 3 degrees)
• Probability of first interaction (e+ & Xrays)
• Thermal effects : Xrays leak + IR slab effect
• Large angle collection and selection < 1 MeV
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Target (2)Y
Z
X
e−
LINAC 10 MeV
Tungsten target
20 mm x 20 mm x 50 µm
e− beam section
1 mm x 20 mm
3 degree
e+
e+e+
e+
Study energy deposit as a function of incidence angle
Thickness = D
equivalent thickness: D’ = D / sin 30
30
D’
D
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Kinetic energy at target exit
positrons electrons
Energy (GeV) Energy (GeV)
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Energy versus angle
Production point
Kinetic energy (GeV)
At target exit
Kinetic energy (GeV)
angl
e
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x
dump
e+
e- B B
B
e+
e+
target
target
Magnetic Bulb
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Collection Setup
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TARGET
QUADRUPOLE
DUMP
MAGNET H2
WALL SHIELD
MAGNET H1
20 cm 50 cm 40 cm 1 m
count e+ here
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Simulation and engineering
x
z
10 cm
x
z
10 cm
10 cm
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e+ position in (y , z) planes
X = 3 cm X = 200 cm
Before 4-poles
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energy versus radius at x = 200 cm
Rad
ius
(cm
)
Energy (GeV)
positrons
Energy (GeV)
electrons
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Positrons radius at x = 200 cm
Radius (cm)
Kinetic energy < 1 MeV
Radius (cm)
All kinetic energies
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Target
e- soldering test on
Tungsten 50 mm
40 kV / 20 mA on 20 mm2
not perforated at 15 mA
Working hypothesis: 1 k W / cm2 3100 K
Test with high intensity beam from IBA foreseen T rise, evaporation…
Nov-14-2003 SLAC EPAC
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Target (2)Y
Z
X
e−
LINAC 10 MeV
Tungsten target
20 mm x 20 mm x 50 µm
e− beam section
1 mm x 20 mm
3 degree
e+
e+e+
e+
Study energy deposit as a function of incidence angle
Thickness = D
equivalent thickness: D’ = D / sin 30
30
D’
D
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Target (3)
track length (cm)
1
10
10 2
10 3
10 4
-0.5 0 0.5 1 1.5 2 2.5 3
30
900
e- track length inside targets of 1mm equivalent thickness
0.480.53900
0.110.1130
rms<L> ( cm) ( cm)
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Energy Deposit in 1cm2 Target
E=10MeV puissance deposee pour 1mA de e-
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 1000 2000 3000 4000 5000
Simulation with GEANT/EGS
E=10MeV courant d e- pour 1kW de puissance deposee
10-1
1
10
10 2
0 1000 2000 3000 4000 5000
D’(mm) D’(mm)
E(e-) = 10 MeV
Pow
er (W
)
30
900
Deposited power for 1 mA
900
30
IMAX for 1 kW deposited
Cur
rent
(mA
)
4.5 kW/mA
1.7 kW/mA
0.59 mA
0.22 mA
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30
E=10MeV nombre de e+ de moins de 1 MeV a l avant pour 107 e- sur la cible
0
1000
2000
3000
4000
5000
6000
7000
8000
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
E=10MeV nombre de e+ a l avant pour 107 e- sur la cible
0
2500
5000
7500
10000
12500
15000
17500
20000
22500
25000
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
30
Production Rate (1)
D’(mm) D’(mm)
107 electrons on 1 cm2 target
900
900
Ne+
Ee+<1 MeVe+ forward
Ne+
~ 15000 / 107 = 1.5 10-3
~ 3500 / 107 = 3.5 10-4
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Production Rate (2)
E=10MeV taux de e+ a l avant pour 1kW depose dans la cible
0
1000
2000
3000
4000
5000
6000
7000
8000
x 10 9
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
E=10MeV taux de e+ de moins de 1 MeV a l avant pour 1kW depose dans la cible
0
200
400
600
800
1000
1200
1400
1600
1800
2000
x 10 9
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
D’(mm) D’(mm)
Ne+
(s-1
)
X 109
Power deposited in 1 cm2 target = 1 kW
900 900
X 109
Ne+
(s-1
)
30 30
Ee+<1 MeVe+ forward
1.4 1012
0.6 1012
Nov-14-2003 SLAC EPAC
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Production
0
10
20
30
40
50
60
70
80
90
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5x 10
-2
0.552.50.25 mA900
1.14.60.58 mA30
Ne+(<1MeV)Ne+Imax
in units of 1012 s-1
For 1 cm2 of target
D’ = 1mm
Limit 1 kW / cm2
Ee+ (MeV)1 2 3 4 5
Normalization to same number of e- generated
900
30
0.58 mA 2.3 mA for 4 cm2
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Collection efficiency
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.2 0.4 0.6 0.8 1 1.2 1.40
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Fraction of e+ at exit plane inside circle of radius 5 or 2 cm centered on axis
r = 5 cm r = 2 cm
E < 600 KeV
E < 1 MeV
transverse radius of e+ source at target level (cm)
e 5 e2
slit shaped beam
2 x 2 cm
1 x 4 cm
with quad
no quad
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Collected Positron Rates (2m from target)
e+ produced as much as possible near axis is best for production and collection
1.360%E < 600 KeV
2.752%E <1 MeV
4.220%forward
e+ ratee5Rcoll= 5 cm
0.630%E < 600 KeV
1.120%E <1 MeV1.68%forward
e+ ratee2Rcoll= 2 cm
(e+ rates in units of 1012 s-1)
0
10
20
30
40
50
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
all e+ at exit plane
R < 5 cm
R < 2 cm
E (MeV)
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Electron and photon fluxes
• Beam and coils on same axis
• Target and downstream coils on same axis
e-
e-
Two possible setups with same e+ output
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Fluxes of electrons and photons
0
1
2
3
4
5
6
7
8
9
10
0 50 100 150 200 250 300
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
200 210 220 230 240 250 260 270 280
0
1
2
3
4
5
6
7
8
9
10
0 50 100 150 200 250 300
0
0.025
0.05
0.075
0.1
0.125
0.15
0.175
0.2
0.225
0.25
200 210 220 230 240 250 260 270 280
X (along coils axis) (cm) X (along coils axis) (cm)
Pow
er (k
W)
Pow
er (k
W)
Setup 1 Setup 2
110 W80 W45 W10 WSetup 21.5 kW450 W140 W5 WSetup 1
R = 4 cmR = 3 cmR = 2 cmR = 1 cmI = 2.3 mA
plot
s fo
r 1 m
A
at exit plane
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-.01 -.005 0.0 0.005 0.01
-.01
-.005
0.0
0.005
0.01
Postprocessor/Zgoubi NoDate... Z (m) vs. Y
A very first design of a 2D expander/uniformizer
b(m
)
x (m)
F. Meot and T. Daniel,
NIM, A 379 (1996) 196-205.
Z (m
)
Y (m)
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Design differences (1)
1.5 eV e+
Proposed design
e-
converter
MeV e+
trap
Ne moderator
e-dump
converter moderator
E (2-5 kV)
extraction lenses
MeV e+
trap
EPOS design + trap
E(decel.)
1.5 eV e+
W
7K10- 2Neonroom10- 4Tungsten
temperatureefficiency
Rossendorf / Aarhus
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Original EPOS design:40 MeV, 0.25 mA, ~CW LinacPt or W moderator, 3.5 mm Pt targetNeutron activationCollection efficiency before trap 20%Expected Rate before trap 1.6 108 s-1
0.8 1082m3mnoW2.510
RatewallLActiv.Mod.I(mA)E (MeV)
10102m3mnoNe2.510
1.6 1083m30myesPt0.2540
Proposed design:
10 MeV, 2.5 mA, CW
Ne Moderator, thin W target
Collection efficiency before trap 20%
Expected rate before trap 1.1 1010 s-1At 10 MeV, 2.5 mA1mm target = 0.8 108 s-1
Design differences (2)
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Other designsThermal neutron capture: 113Cd(n,g)114Cd s = 26000 barn !!By nuclear research reactor FRM2 in Munich (Germany) can reach 1010s-1
Building size:
40 m x 40 m x 30 m
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• Gravity and spectroscopy with Ps H Hbar
• Astrophysics “in vitro”
• 3D molecule imaging
• Ps BEC and 511 KeV Laser
• Applied technology : positron microscope
Scientific Goals
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P. Pérez & A. Rosowsky 39
Proposal: best ingredients ..
• e+ facility : Ne+ > 109 s-1
• fundamental interaction physics : HEP lab
• e – beam expertise and beam research
• SR radiation control infrastructure
• Interdisciplinary lab
• Location near trap development
10 MeVrhodotron
target - collector
moderator - buffer gas - trap e+
~ 14 m
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Ressource Impacts
• Building :– new ~ 2.5 M$ – refurbished ~ x00 k$
• e- machine :– Rhodotron ~ 2.5 M$ – Linac ~ 300 k$
• Infrastructure :– 250 kW – Water cooling – Radiation control, safety …
• Target-collection• Injection
~ 400 k$
• Parallel project UC San Diego
– Moderator
– Buffer gas
– trap ~ 500 k$