Page 1
1
Ultracolod Photoelectron Beamsfor ion storage rings
CSR E-Cooler
TSR (magnetic)
e-target
e-c
oole
r
CSR (electrostatic)
Elab: 100-4000 eV
Current - 2 mA Lifetime - 24 h kT < 1.0 meV kT|| = 0.02 meV
Electron-ion collision spectroscopy
D. A. Orlov, C. Krantz, A. Shornikov, A. Wolf
Elab : 10-1eV
• Low e-energies: => low current (100-1µA) => higher kT||
• e-transport by B => slow ions distorted
Cooling at eV-energies - it is a challenge!
Electron cooling
TSR E-target
Extremely high resolution is demonstrated!
DR of Sc18+
1 ve = vi
2 ve ≠ vi
6 meV
Max-Planck-Institut für Kernphysik, 69117, Heidelberg, Germany
Page 2
Dmitry Orlov, MPI-K, PESP-08 2
cold electrons
OUTLINE1
HOW TO: cold e-beams
2 E-cooling
Collision resolution
6Cooling of CF+ ions
at TSR by 53 eV photoelectrons
7Manipulation with
0.1-10 eV e-beams at TSR target
4Why?
ElectrostaticCryogenic Storage Ring
3electron collision
spectroscopy @ TSR (keV)
5e-beams of eV energies,
CSR cooler
Page 3
Dmitry Orlov, MPI-K, PESP-08 3
300 K 90 K
Energy distributions of photoelectrons“2D”-measurement
(E|| , E)
EF
E vac
ThermocathodevacuumT=1300-1500 K
kT=110-120 meV
Cold electrons. How to (A): Photocathode kTC = 10 meV
Fully activated cathode: QY= 15-35%
QYeff=1 %
Laser: 1W @ 800 nm9 (transmission) 2W @ 532 nm (reflection)E-current: 0.1- 2.5 mALifetime : >24 h
D.A. Orlov et al., APL, 78 (2001) 2721;
Suppression
Suppression
Strong energy and impulse relaxations Energy spreads of about kT
E vac
E F
E c
(CsO)
E v
GaAs vacuum
T= 80 K
Suppression
Suppression
kT=10 meV
Thermocathode kTC > 100 meV
Page 4
4
Cold electrons. How to make them colder (B):
1. Magnetic expansion
C
guide
kTkT
B
B
0B
0 (high field) B
guide(low field)
2. Acceleration
Reduction of kT
Reduction of kT||
heatingplasmaeU
TkkT C
2
22
||
= 20
Thermocathode kT = 5-6 meV
Photocathode kT = 0.5 meV
kT|| = 0.02-0.1 meV
Phase-space conservation
v║
E
ΔE
ΔE
Δv Δv'
U0
Page 5
5
Cold electrons. How o keep them cold (C):
4/12/1100015
12.6
U
V
d
mm
mA
IGBB
3/12/16/1
110
10001561
mA
I
meV
kT
U
V
d
mmGB c
g
High magnetic field is required
1. To avoid beam divergence
2. To suppress TLR
3. To provide adiabatic transport
2/1
1000
10067
V
U
B
GmmC
e
e
e
low current high currenthigh current +magnetic field
keeping dT|| / dZ < 5 μeV/m :e
e
B
rc
ne-1/3
rc << ne-1/3
B
e
R
λc << R
λc
Typical transition lengths R=100 mm
2/1
1000316
V
UGBg1.0
RC
Page 6
Dmitry Orlov, MPI-K, PESP-08 6
cold electrons1
HOW TO: cold e-beams
6Cooling of CF+ ions
at TSR by 53 eV photoelectrons
7Manipulation with
0.1-10 eV e-beams at TSR target
4Why?
ElectrostaticCryogenic Storage Ring
3electron collision
spectroscopy @ TSR (keV)
5e-beams of eV energies,
CSR cooler
2 E-cooling
Collision resolution
Page 7
Dmitry Orlov, MPI-K, PESP-08 7
Principle of Electron Cooling10-3
2
3
068
3
e
mcC
eion
2/3
220
cM
Tk
LZn
MC
e
eB
Ce
ion
TSR
e-cooling
Page 8
Dmitry Orlov, MPI-K, PESP-08 8
Electron-ion collision resolution
rEv
V║
V
Recombination velocity
Flattened electron distribution
kT║≪ kT
||2 2ln16)2ln( kTEkTE r
0
0.2
0.4
0.6
0.8
1
0.002 0 0.002 0.004 0.006 0.008 0.01
Rat
e, a
.u
C M en e rg y, eV
U -U , Vc o o l
0 2 4 6 5 3 1 -2 -1
U = 1 0 0 0 Vco o l
k T
k T ||
= 1 m eV
= 0 .0 1 m eV
Real resonance position
DR
rat
e co
effi
cien
t
ve = v
i
Tk
m
Tk
m
Tk
m
Tk
mf edeee
d 2exp
2exp
22),(
2
||
2||
2
||
3, df dd
For high energies Er:
Page 9
Dmitry Orlov, MPI-K, PESP-08 9
cold electrons1HOW TO:
cold e-beams
6Cooling of CF+ ions
at TSR by 53 eV photoelectrons
7Manipulation with
0.1-10 eV e-beams at TSR target
4Why?
ElectrostaticCryogenic Storage Ring
5e-beams of eV energies,
CSR cooler
2 E-cooling
Collision resolution
3electron collision
spectroscopy @ TSR (keV)
Page 10
Dmitry Orlov, MPI-K, PESP-08 10
~0.2 ... 8 MeV/uDetectors
(ions and neutrals)
e-target
Interaction section 1.5m
Electron gun withmagnetic expansion
≈10...90
Adiabaticacceleration
Collector
TSR dipole
Movable ion detector
Neutrals detector
Ion beam
e-
e-source
Electron collision spectroscopy.TSR electron target.
Page 11
Dmitry Orlov, MPI-K, PESP-08
-e
Aq +
Electron captureresonance
nℓ
(Aq +)* + nℓ
( A(q -1)+ )**= + e ( A(q -1)+ )*
nℓ
ProductdetectionE
res
Electron collision spectroscopyon multi-charged ions
Page 12
Dmitry Orlov, MPI-K, PESP-08
Core excitation energies ΔE (2s–2p)
(2p3/2
10d5/2
)J = 4
(2p3/2
10d3/2
)J = 2
(2p3/2
10d3/2
)J = 3
Electron target
PRL, 100, 033001 (2008)
Photocathode
~ 0.02 meV T||
T┴
= 1.0 meV
45Sc18+
TSR – 4 MeV/u
E
EnΔE
core
1s2 2p3/2
1s22s(1s2 2p
3/2 nℓ'
j )
J
Eres
= 44.30943(20) eV (±0.2 meV, 4.6 ppm)
n = 10
100 meV
(<1% few body QED)
Page 13
Dmitry Orlov, MPI-K, PESP-08 13
direct& indirectprocess
Dissociative recombination of HD+: rate spectrum
Electron collision energy (milli-eV)
Re
com
bin
atio
n r
ate
co
effi
cie
nt (
10
-9 c
m3
s-1)
kT ~ 2 meV(CRYRING data)
Model cross section withkT ~ 0.5 meV, kT
|| ~ 0.02 meV
TSR e-target with cryo-photocathode
HD+ (1sσ, v = 0, J ) + e → HD** (1sσ nℓλ , v'J' ) → H(n) + D(n' )
PRL 100, 193201 (2008)
Rotational resolution (DR rate)
-e
+ eAB + -
B*A +
(AB +)* + nℓ = AB **
Vibration v=0 -> 1 0.15 eVRotation j=0 -> 1 4.5 meV
Page 14
Dmitry Orlov, MPI-K, PESP-08 14
Dissociative recombination of HF+: 2D imaging
Electron - Target
~ 12 m
vbeam (~MeV)
~cm
detector surface
Pro
bab
ilit
y (n
orm
aliz
ed)
d2D [mm]
Rotational resolution
Particle distance, mm60 2 4 8 10
EKER – ECM-kT, milli-eV50 20 50 100
PRELIMINARY
HF+ (X 2, v=0 ,J ) + e- HF**(V 1+) H(n=2) + F(2P3/2,1/2)
HF**(V 1+)
v=0
J=0,1,2,….
H(n=2) + F(2P3/2)
Page 15
Dmitry Orlov, MPI-K, PESP-08 15
cold electrons1HOW TO:
cold e-beams
6Cooling of CF+ ions
at TSR by 53 eV photoelectrons
7Manipulation with
0.1-10 eV e-beams at TSR target
5e-beams of eV energies,
CSR cooler
2 E-cooling
Collision resolution
3electron collision
spectroscopy @ TSR (keV)
4Why?
ElectrostaticCryogenic Storage Ring
Page 16
Dmitry Orlov, MPI-K, PESP-08 16
Electrostatic Cryogenic Storage Ring at 2 K
Reaction microscope
Ion injection
E-target
Diagnostic section
neutrals CSR
Clusters, biomolecules
(M up to few 1000 amu)
ELECTROSTATIC
Storage Rings
(no mass limitation)
Ring Circumference
34 m
Straight Section Length
2.5 m
Energy Range 20 - 300
keV
Maximum Beta h/v
12/6 m
Maximum Dispersion
2.1 m
Tunes Qh/Qv 2.59/2.65
XHV (n<103 cm-3)
M= 1-100(1000) amu
Electrostatic Storage Ring
T=10 (2K)
Electron collision energy (milli-eV)
Re
com
bin
atio
n r
ate
co
effi
cie
nt (
10-9
cm
3 s
-1)
kT ~ 2 meV(CRYRING data)
Model cross section withkT ~ 0.5 meV, kT
|| ~ 0.02 meV
TSR e-target with cryo-photocathode
T< 10 K is required
after some second storage
after production in the ion source
Boltzmann distribution (300 K @ TSR)
rotational quantum state
vibrational quantum stateHD+ + e- H + D
Page 17
Dmitry Orlov, MPI-K, PESP-08 17
cold electrons1HOW TO:
cold e-beams
6Cooling of CF+ ions
at TSR by 53 eV photoelectrons
7Manipulation with
0.1-10 eV e-beams at TSR target
5e-beams of eV energies,
CSR cooler
2 E-cooling
Collision resolution
3electron collision
spectroscopy @ TSR (keV)
4Why?
ElectrostaticCryogenic Storage Ring
Page 18
Dmitry Orlov, MPI-K, PESP-08 18
Features of low-energy e-beams (A)
2/32/3
10011
V
U
Perv
PmAPUI
1. Low voltage Low current @ density
2/3
220
cM
Tk
LZn
MC
e
eB
Ce
ionCOOL
High-perveance?
28028
0.281.8
0.03
0.10.0021.63001000.30.015.1300323.20.45430030.70.0211201102.11653001
Electron density
[10 6 cm -3]
Electron current
[mA]
Electron energy
[eV]
Ion energy[keV]
Ion mass[amu]
Cooling time (cold beam)
[s]P=1 μPerv
kBTe=1.0 meV
Lc=3.3
C=0.028
Page 19
Dmitry Orlov, MPI-K, PESP-08 19
Features of low-energy e-beams (B)
Photoelectron source Low T║
2. Low voltage High kT||
3. High Bguid
Better for slow electrons Strong ion deflection
heatingplasmaeU
TkkT C
2
22
||
Electron energy W, eV
thermocathode
photocathode
1e-06
1e-05
1e-04
10 100
1e-03
{avoid beam divergence; suppress TLR; adiabatic transport}
2/1
100
1002.21
V
U
B
GmmC
Page 20
Dmitry Orlov, MPI-K, PESP-08 20
New Concept for the CSR Electron Cooler/Target
toroid merging Dipole merging
1-2 G 30 G
We need to cool 20 keV protons Bmin≈20 G
Page 21
Dmitry Orlov, MPI-K, PESP-08 21
Ion track
General view
New Concept for the CSR Electron Cooler/Target
Electron energy 160-1(or below) eV
Cooling solenoid length
1065 mm
Cooling solenoid radius
130 mm
Max. magnetic field 150 Gauss
Toroid bending radius
200 mm
Merging box solenoid
Racetrack 330x540 mm, length 350 mm
Merging box vertical dipoles
Racetrack 268x360
Merging Box
toroid merging Dipole merging
1-2 G
ZkeV
WAGB ion
C
1
20130
30 G
We need to cool 20 keV protons Bmin≈20 G
Page 22
Dmitry Orlov, MPI-K, PESP-08 22
Adiabatic electron transport
1
z
B
Bz
Z
L
T
Adiabatic criterion
2
3028
G
BeVBECScaling rule for critical energy
Finite element analysis with TOSCA code
Cross-sections of Heating of paraxial beam
EeB
meL
22 - Larmor length
1.0
z
B
Bz
Z
LHeating start at app.
Adiabatic motion
Transverse temperature
cathbb
TkTk
For modeled field geometry
15 20 25 30 35 40 45 50 55 60 65 120 150 180 210 240
1
10
EC
30 Gauss
kTT
R ,
me
V
Beam energy, eV
60 Gauss
EC
initial kTTR
= 0.5 meV
kTcath
= 10 meV
= 20
1234567
0
30
60
90
120
150
180
210
240
270
300
330
1234567
Etr, meV
Ra
diu
s, m
m
0.5416
0.5448
0.5480
0.5512
0.5545
0.5577
0.5609
0.5641
0.5673
Electron energy 20 eV, B = 30 G
Etr~0.02meV
Results of e-tracking calculation (TOSCA code)
kT┴0
Page 23
Dmitry Orlov, MPI-K, PESP-08 23
cold electrons1HOW TO:
cold e-beams
7Manipulation with
0.1-10 eV e-beams at TSR target
5e-beams of eV energies,
CSR cooler
2 E-cooling
Collision resolution
3electron collision
spectroscopy @ TSR (keV)
4Why?
ElectrostaticCryogenic Storage Ring
6Cooling of CF+ ions
at TSR by 53 eV photoelectrons
Page 24
Dmitry Orlov, MPI-K, PESP-08 24
Low-energy cooling of CF+ cooling by 53 eV electrons
vC,total
vF,total
vbeam
vC
d3D d2D
C
F
vbeam
CF +
Detectorsurface
ve
vC
vF
e-
vC,total
vF,total
vbeam
vC
d3D d2D
C
F
vbeam
CF +
Detectorsurface
vC,total
vF,total
vbeam
vC
d3D d2D
C
F
vbeam
CF +
Detectorsurface
ve
vC
vF
e-
Themocathode, September 2006, 0eV, 12-30 s
Photocathode, March 2007, 0eV, 12-30 s
CF
CF
Electron-target
Photocathode T~ 1.0 meV
I = 0.34 mA
ne=3∙106 cm-3
x [mm]-10 0 10 20 30 40 50 60 70
y [
mm
]
-10
0
10
20
30
40
50
hh3Entries 59917Integral 5.991e+004
hh3Entries 59917Integral 5.991e+004
0
10
20
30
40
50
60
70
80
Center of mass distribution
Photocathode
Themocathodecenter-of-mass
12-30 sEcm = 0 eV
center-of-mass12-30 s
Ecm = 0 eV
Page 25
Dmitry Orlov, MPI-K, PESP-08 25
CF+– cooling time
2
4
6
8
10
0
5
10
15
20
25
0 2 4 6 8 10 12
FWH
My,
mm
0
0 2 4 6 8 10 12 6 0 2 4 8 10 12
x=1.8 s
Cooling time, s
FWH
Mx,
mm
55
1 mm
1 mm
Cooling time, s
0
0
Y, m
mX
, mm
55
y=1.4 s
vC,total
vF,total
vbeam
vC
d3D d2D
C
F
vbeam
CF +
Detectorsurface
ve
vC
vF
e-
vC,total
vF,total
vbeam
vC
d3D d2D
C
F
vbeam
CF +
Detectorsurface
vC,total
vF,total
vbeam
vC
d3D d2D
C
F
vbeam
CF +
Detectorsurface
ve
vC
vF
e-
C F
Y, m
m
X, mm
TSR
Photocathode, March 2007
• Current: 0.34 mA• B-expansion: 20• ne=3∙106 cm-3
• T┴ =1.0 meV cool < 2 s
Detector (X/Y): σ 0.4 / 0.3 mm
Ion beam: X Y
ε 2.5∙10-3 0.9∙10-3 mm∙mrad
σ 200 37 μm ΔP/P 2.5∙10-5 2.5∙10-5
x=1.8 s
y=1.4 s
1 mm
1 mm
Page 26
Dmitry Orlov, MPI-K, PESP-08 26
cold electrons1HOW TO:
cold e-beams
5e-beams of eV energies,
CSR cooler
2 E-cooling
Collision resolution
3electron collision
spectroscopy @ TSR (keV)
4Why?
ElectrostaticCryogenic Storage Ring
6Cooling of CF+ ions
at TSR by 53 eV photoelectrons
7Manipulation with
0.1-10 eV e-beams at TSR target
Page 27
Dmitry Orlov, MPI-K, PESP-08 27
Manipulation with magnetized eV-electrons
Wcathode
Wemission
Wmetal
SC
Ekin
V0
V
Wmetal
SCEF
EDC, log. scale
Ekin
Cathode
Drift tubes
TSR target
Cathode
Collector
Page 28
Dmitry Orlov, MPI-K, PESP-08 28
Manipulation with magnetized eV-electrons
Ekin = q(V0V)(WmetalWemission)SC
1. Work function difference
2. Space charge at the cathode
3. Space charge SC(Ie, V) in the interaction region can be calculated independently.
Wcathode
Wemission
Wmetal
SC
Ekin
V0
V
Wmetal
SCEF
EDC, log. scale
Ekin
Cathode
Drift tubes
To collector
TSR target
Drift tubesCathode
Collector
Ekin ≠ q(V0V)
Page 29
29
Manipulation with magnetized eV-electrons
Ekin = q(V0V)(WmetalWemission)SC
EF
Wemission
V0
V
Wmetal
SC
Ekin
To collectorDrift tubesCathode
Cathode
Drift tubes
Collector
V0=20 V
Ie=3µA
Ie=40 pA
(WmetalWemission)SCEkin
A
B
A
B
Page 30
30
Manipulation with magnetized eV-electrons
Ekin = q(V0V)(WmetalWemission)SC
EF
Wemission
V0
V
Wmetal
SC
Ekin
To collectorDrift tubesCathode
Cathode
Drift tubes
Collector
V0=20 V
Ie=4.5 µA
Ie=40 pA
(WmetalWemission)SCEkin
A
A
Ekin, eV 2.3 1.4 1.0 0.48
I, μA 34.5 21.3 13.2 4.5P, μPerv 9.8 12.5 12.8 13.6
Page 31
Dmitry Orlov, MPI-K, PESP-08 31
1HOW TO:
cold e-beams
5e-beams of eV energies,
CSR cooler
2 E-cooling
Collision resolution
3electron collision
spectroscopy @ TSR (keV)
4Why?
ElectrostaticCryogenic Storage Ring
6Cooling of CF+ ions
at TSR by 53 eV photoelectrons
7Manipulation with
0.1-10 eV e-beams at TSR target
THANK YOU !
Questions?
Page 32
Dmitry Orlov, MPI-K, PESP-08 32
Page 33
Dmitry Orlov, MPI-K, PESP-08 33
Electron beam formation – adiabaticity
adiabaticity: dB/dz, dE/dz small against cyclotron length
2/1
100
1002.21
V
U
B
GmmC
Bg
Cathode, -100 V Extraction electrode, 0 V
80
50
φ=100
CathodeEntrance,
extraction electrode
80 G
320 G
40 G
Typical transition lengths 100 – 200 mm ζ=0.1-0.2 2/1
100100
V
UGBC
Higher adiabaticity Low energies
Page 34
Dmitry Orlov, MPI-K, PESP-08 34
Acceleration sectionAcceleration section
CollectorCollectorToroidToroid
TSR dipoleTSR dipole
Interaction Interaction sectionsection
electron beam
Ion beam
Correction dipolesCorrection dipoles
RailsRails
Electron target at TSR
PreparationPreparationchamberchamber
(photocathode)(photocathode)