Development of laser stripping at the SNS · October 28, 2010. 2 Managed by UT-Battelle for the...
Transcript of Development of laser stripping at the SNS · October 28, 2010. 2 Managed by UT-Battelle for the...
Managed by UT-Battellefor the Department of Energy
Development of laser stripping at the SNS
Timofey Gorlov
On behalf of the SNS laser stripping team
October 28, 2010
2 Managed by UT-Battellefor the Department of Energy Presentation_name
Outline
History of laser stripping
Proof of principle experiment
Physical model
Proof of practicity experiment
Experimental studies
Future plans and ideas for SNS and other projects
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Liquid Hg
Target
SNS Accelerator Complex
945 ns
1 ms macropulse
Cu
rre
nt
mini-pulse
1 GeV
LINAC
Chopper system
makes gaps
2.5 MeV 1000 MeV87 MeV
CCL SCL, =0.61 SCL, =0.81
186 MeV 387 MeV
DTLMEBT
Accumulator Ring
RTBT
Target
HEBT
Injection Extraction
Collimators
Ion Source
+
RFQ
micro-pulses402.5 MHz
Injection point
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Goals
Replacement of stripping foil by laser assistant stripping
H- p + 2e-
H-
Foil
p + 2e- H- p + 2e-
Foil (Beam on)
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H- H0 H0*
Step 1: Lorentz Stripping
Step 2: Resonant laser Excitation
Step 3: Lorentz Stripping
High-field Dipole Magnet
High-field Dipole Magnet
H- H0 + e- H0 (n=1) + H0* (n=3) H0* p + e-
Three-step laser stripping scheme
p+
e
e
e
ee
e
V. Danilov (2003)
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Proof of principle experiment (2006)
mini-pulse
The maximal achieved efficiency: 0.85±0.1 (1st run) and 0.9±0.05 (2nd run)
Stripping time: about 10 ns
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Theory of the Laser Stripping
H- H0
Step 1: Lorentz Stripping
High-field Dipole Magnet
H- H0 + e-
e
e
e
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Two level atom (Schrodinger equation)
13h
)(ˆLEH
ti
n =3
n =2
n =1
The model is valid only for E=B=0 and linear polarized laser field
3p
1s
)(
)(
3113
1331
L
L
Escc
Escc
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H0
First way to compensate energy spread
e
Bad laser optics scheme
Good laser optics
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H0
Second way to compensate energy spread
H0
No angle-energy correlation
angle-energy correlation is not
zero
pz
x
z
Necessary correlation is given by dispersion
function
Dx’=2.6 for T=1 GeV beam
Perfect
correlation
x
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Proof of plasticity
experiment
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Liquid Hg
Target
SNS Accelerator Complex
945 ns
1 ms macropulse
Cu
rre
nt
mini-pulse
1 GeV
LINAC
Chopper system
makes gaps
2.5 MeV 1000 MeV87 MeV
CCL SCL, =0.61 SCL, =0.81
186 MeV 387 MeV
DTLMEBT
Accumulator Ring
RTBT
Target
HEBT
Injection Extraction
Collimators
Ion Source
+
RFQ
micro-pulses402.5 MHz
Location of the
experiment
Proof of principles
Stripping time appr. 10 ns
Proof of practicity
Stripping time appr. 1 us
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Advanced physical model
Ground
state
External field
H0
High-field Dipole Magnet
High-field Dipole Magnet
H-
Stark effect at the interaction point
Spontaneous decay losses
Lorentz stripping of H0 excited beam
Atom in electric fieldUnperturbed atom
Spontaneous decay losses
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Lorentz stripping of H0
excited beam in the fringe
magnetic field
eeeeeeee
N
S
Lorentz stripping
Perfect field
eeeeeeee
N
S
Lorentz stripping
Real field
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Emittance growth at the fringe field
Fringe field:
T=4 GeV
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Schrödinger equation approach
13h
1031)()()(),(ˆ 22
1
NtStctcEEHt
iN
n
mnnmL
n =3
n =2
n =1
Stark sublevels
Spontaneous decay can not be taken into account
continuum10 equations
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Density matrix approach
23h13h n =3
n =2
n =1
Stark sublevels
Everything can be taken into account
continuum
13h
12h
222 321,1,][)( NNnmDtnmMaster equation
196 equations
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Computer application for laser stripping
Python
wrapper
C++
ORBIT
user
PyORBIT
We can optimize parameters of laser beam and H- beam for better stripping
efficiencyx
z
y
H0
H0
Hydrogen Beam
Laser Beam
H0
H0
About 5 parameters for description of the
laser beam
Emittance parameters for description of the
H0 beam
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Location for the new experiment
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Experimental studies
RingParameter Value
The longitudinal energy of the ions 1 GeV
Relative spread of the longitudinal
energy σT/T
0.5·10-3
τFWHM micro-bunch duration 30 ps
x < 30 m
y 0.75 m
x 0
y 0
Dx dispersion derivative 2.6
Dx dispersion 0 m
εx 0.3 ·mm·mrad
εy 0.3 ·mm·mrad
Laser Stripping
locationQH24
QV23
QH22
QV21
QH20
QV19
QV
11
QH
10
QV
09
QH
08
QV
07
QH
06
QV
05
QH
04
QV
03
QH
02
QV
01
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Preliminary tune of dispersion function
Laser Stripping interaction point
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Laser stripping via a broad shape resonance
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Hydrogen atom in a strong electric field
H0 H0
Ee e
H0
eE
No field Weak field Strong field
splittingbroadening
Co
ntin
uo
us s
pectru
m
22
1
nE
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H0
Third way to compensate energy spread
e
High-field Dipole Magnet
e
e
hν1
n=1
n=2
Different particles will see the different frequencies of
laser
hν2
hν3
But they will all be excited because of the broad
shape resonance
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Advantages of the scheme
Recycler (cavity)
H0
e
High-field Dipole Magnet
e
e
Possibility to recycle laser beam
No spontaneous transition losses
Small emittance growth
Using just one stripping dipole magnet (the scheme is more compact)
Can be applied for energy 4 GeV and more (considered as disadvantage)
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Selected references for more details
I. Yamane, Phys. Rev. ST Accel. Beams 1, 053501 (1998).
V. Danilov, A. Aleksandrov, S. Assadi, S. Henderson, N. Holtkamp, T. Shea, A. Shishlo, Y. Braiman, Y. Liu, J. Barhen, and T. Zacharia, Phys. Rev. ST Accel. Beams 6, 053501 (2003).
V. Danilov, A. Aleksandrov, S. Assadi, J. Barhen, W. Blokland, Y. Braiman, D. Brown, C. Deibele, W. Griece, S. Henderson, J. Holmes, Y. Liu, A. Shishlo, A. Webster, and I. N. Nesterenko, Phys. Rev. ST Accel. Beams 10, 053501 (2007).
T. Gorlov, V. Danilov, and A. Shishlo, Phys. Rev. ST Accel. Beams 13, 050101 (2010).
T. Bergeman, C. Harvey, K. B. Butterfield, H. C. Bryant, D. A. Clark, P. A. M. Gram, D. MacArthur, M. Davis, J. B. Donahue, J. Dayton, and W.W. Smith, Phys. Rev. Lett. 53, 775 (1984).
T. Gorlov and V. Danilov, Phys. Rev. ST Accel. Beams 13, 074002 (2010).