Development of laser stripping at the SNS · October 28, 2010. 2 Managed by UT-Battelle for the Department of Energy Presentation_name Outline History of laser stripping Proof of

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


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


Goals

Replacement of stripping foil by laser assistant stripping

H- p + 2e-

H-

Foil

p + 2e- H- p + 2e-

Foil (Beam on)


H- H0 H0*

Step 1: Lorentz Stripping

Step 2: Resonant laser Excitation


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)


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


Theory of the Laser Stripping

H- H0



H- H0 + e-

e

e

e


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


H0

First way to compensate energy spread

e

Bad laser optics scheme

Good laser optics


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


Proof of plasticity

experiment


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


Advanced physical model

Ground

state

External field

H0



H-

Stark effect at the interaction point

Spontaneous decay losses

Lorentz stripping of H0 excited beam

Atom in electric fieldUnperturbed atom

Spontaneous decay losses


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


Emittance growth at the fringe field

Fringe field:

T=4 GeV


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


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


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


Location for the new experiment


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


Preliminary tune of dispersion function

Laser Stripping interaction point


Laser stripping via a broad shape resonance


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


H0

Third way to compensate energy spread

e


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


Advantages of the scheme

Recycler (cavity)

H0

e


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)


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).

Documents

Development of laser stripping at the SNS · October 28, 2010. 2 Managed by UT-Battelle for the Department of Energy Presentation_name Outline History of laser stripping Proof of