Coherent Synchrotron Radiation Studies at the Advanced Light Source and the IKNO proposal

Coherent Synchrotron RadiationCoherent Synchrotron Radiation Studies at the Advanced Light Source Studies at the Advanced Light Source

and the IKNO proposaland the IKNO proposal

Fernando SannibaleFernando Sannibale

INFN - LNF, Frascati, Italy, July 10, 2008

AFRD (AFRD (ALS Acc. Physics and CBP)ALS Acc. Physics and CBP) :: J. M. Byrd, D. S. Robin, J. M. Byrd, D. S. Robin, F. Sannibale, A. Zholents, M. Zolotorev. F. Sannibale, A. Zholents, M. Zolotorev.

Collaborations:Collaborations: BESSY, DLR (Berlin), SLACBESSY, DLR (Berlin), SLAC

Important contributions:Important contributions:M. Abo-Bakr, J. Feikes, E. Forest, S. Heifets, K. Holldack, H. M. Abo-Bakr, J. Feikes, E. Forest, S. Heifets, K. Holldack, H.

W. Hubers, P. Kuske, W. Leemans, A. Loftsdottir, B. W. Hubers, P. Kuske, W. Leemans, A. Loftsdottir, B. Marcelis, J. Murphy, T. Scarvie, C. Steier, G. Stupakov, M. Marcelis, J. Murphy, T. Scarvie, C. Steier, G. Stupakov, M.

Venturini, R. Warnock, G. Wustefeld, ...Venturini, R. Warnock, G. Wustefeld, ...


A Team WorkA Team WorkCSR Studies

at the ALS and IKNO.F.Sannibale

ALS:ALS: Z. Hao, M. C. Martin.Z. Hao, M. C. Martin.

MSD:MSD: R. W. Schoenlein. R. W. Schoenlein.

Present IKNO Collaboration:Present IKNO Collaboration: P. Innocenzi, A. Marcelli, F. P. Innocenzi, A. Marcelli, F. Sannibale.Sannibale.

Coherent Synchrotron Radiation (CSR) has been matter Coherent Synchrotron Radiation (CSR) has been matter of great interest and study in the last years:of great interest and study in the last years:

• As a powerful diagnostic for bunch compressors in free As a powerful diagnostic for bunch compressors in free electron lasers (FEL) (FLASH, LCLS, FERMI, …);electron lasers (FEL) (FLASH, LCLS, FERMI, …);

• As something to carefully avoid or at least control in every As something to carefully avoid or at least control in every short bunch high charge accelerator where CSR can short bunch high charge accelerator where CSR can

jeopardize the performances (linear colliders, short pulses jeopardize the performances (linear colliders, short pulses synchrotron radiation sources, damping rings, ...);synchrotron radiation sources, damping rings, ...);

• But also as a ‘dream’ for potential revolutionary But also as a ‘dream’ for potential revolutionary synchrotron radiation (SR) source in the THz frequency synchrotron radiation (SR) source in the THz frequency

range.range.INFN - LNF, Frascati, Italy, July 10, 2008

Why Studying CSR?Why Studying CSR?CSR Studies


Scarcity of broadband powerful source in such a region of the spectrumScarcity of broadband powerful source in such a region of the spectrum


The “Terahertz Gap”The “Terahertz Gap”CSR Studies


THz Science: THz Science: collective excitations, protein motions collective excitations, protein motions & dynamics, superconductor gaps, magnetic & dynamics, superconductor gaps, magnetic

resonances, terabit wireless, medical imaging, resonances, terabit wireless, medical imaging, security screening, detecting explosives & bio agents security screening, detecting explosives & bio agents

……

Hz

1 THz 1 THz = 4.1 meV = 4.1 meV = 33 cm= 33 cm-1-1

= 300 = 300 mm

““DOE-NSF-NIH Workshop on Opportunities in THz Science” DOE-NSF-NIH Workshop on Opportunities in THz Science” February 12-14, 2004February 12-14, 2004

http://www.science.doe.gov/bes/reports/abstracts.html#THzhttp://www.science.doe.gov/bes/reports/abstracts.html#THz

• High StabilityHigh Stability

• Non interceptive radiation processes are required.Non interceptive radiation processes are required.Synchrotron and edge radiation most efficientSynchrotron and edge radiation most efficient

• Many users capabilityMany users capability

• Multicolor experiments capabilityMulticolor experiments capability

• Capability of "exotic" experiments (femtoslicing, Capability of "exotic" experiments (femtoslicing, stacking, ...)stacking, ...)


Why CSR from Storage RingsWhy CSR from Storage RingsCSR Studies



A Multi-Year EffortA Multi-Year EffortCSR Studies


2002: The microbunching instability (MBI):2002: The microbunching instability (MBI): First First experimental proof. experimental proof. (J.M.Byrd (J.M.Byrd et alet al., PRL ., PRL 8989, 224801, 2002.), 224801, 2002.)

2003-2004: Stable CSR in storage rings:2003-2004: Stable CSR in storage rings: Development of Development of a model accounting for experimental observations. a model accounting for experimental observations. (F. Sannibale (F. Sannibale et alet al., PRL ., PRL 9393, 094801, 2004.), 094801, 2004.)

2004-2005: CSR from “femtoslicing” experiment:2004-2005: CSR from “femtoslicing” experiment: First First experimental data and characterization. experimental data and characterization. (J.M.Byrd (J.M.Byrd et alet al., PRL ., PRL 9696, 164801, 2006.), 164801, 2006.)

2004-2006: Laser seeding of the MBI:2004-2006: Laser seeding of the MBI: First experimental First experimental observation and model for the phenomenon.observation and model for the phenomenon.(J.M.Byrd (J.M.Byrd et alet al, PRL , PRL 9797, 074802, 2006.), 074802, 2006.)

Synchrotron radiation from a bend

2

cos

cziezSdzg

Normalized Bunch Longitudinal Distribution

gNgNd

dp

d

dP 21

The CSR factor The CSR factor gg(()) determines the high frequency cutoff for CSR, while the determines the high frequency cutoff for CSR, while the vacuum chamber (shielding) defines the low frequency one.vacuum chamber (shielding) defines the low frequency one.

10 g

Single particle power spectrum for the radiating

process under consideration(including shielding effects)

angle

nobservatio

incoherent

NPSR coherent

NPCSR2

Ng 1CSR for:CSR for:

The power spectrum of the radiation from a bunch The power spectrum of the radiation from a bunch with with NN particles is given by: particles is given by:


CSR BasicCSR BasicCSR Studies


2

cziezSdzg 1.0 ps - Gaussian Distribution1.5 ps - Gaussian Distribution2.0 ps - Gaussian Distribution

To extend the CSR spectrum towards higher frequenciesTo extend the CSR spectrum towards higher frequencies

the bunches must be shortened. the bunches must be shortened.

Very sensitive knob!Very sensitive knob!

22

2

2

2

1

c

z

ec

zS

22 eg


CSR Form FactorCSR Form Factorvs. Bunch Lengthvs. Bunch Length

CSR Studies at the ALS and IKNO.

F.Sannibale

2

cos

cziezSdzg

To extend the CSR spectrum towards higher frequencies: To extend the CSR spectrum towards higher frequencies: the ‘saw-tooth’ distribution is the "best".the ‘saw-tooth’ distribution is the "best".


CSR Form Factor vs.CSR Form Factor vs.Longitudinal Bunch DistributionLongitudinal Bunch Distribution


F.Sannibale

Shorten the bunches as Shorten the bunches as much as possible.much as possible.

Find a mechanism for generating sharp edged distributions at Find a mechanism for generating sharp edged distributions at equilibrium (saw-tooth like possibly).equilibrium (saw-tooth like possibly).

And of course, put as much particles as possible in the bunch.And of course, put as much particles as possible in the bunch.

Extend the vacuum chamber Extend the vacuum chamber cutoff towards wavelengths cutoff towards wavelengths

as long as possible.as long as possible.

<

<

2hh

1/2

<

<

2hh

1/2


The “Cocktail” for aThe “Cocktail” for aGood THz SourceGood THz Source


F.Sannibale

21

2~

hhCutoff

2

13

RFRF

C

fV

E

Unfortunately, in this description a major player is missing.Unfortunately, in this description a major player is missing.

We will see that for short bunches (~ ps) the situation becomes a little We will see that for short bunches (~ ps) the situation becomes a little bit more complicate...bit more complicate...

1wavenumberw

FrontBack

bunchdistribution

SR wake accelerates bunch front

re-

Ef

SR Emission Cone

Because of the curved trajectory of the Because of the curved trajectory of the beam, the photons radiated from beam, the photons radiated from

particles in the tail of the bunch catch up particles in the tail of the bunch catch up with the particles in the head.with the particles in the head.


The SynchrotronThe SynchrotronRadiation WakeRadiation Wake

CSR Studiesat the ALS and IKNO.

F.Sannibale

The curved trajectory also allows for the The curved trajectory also allows for the electric field of these photons to have a electric field of these photons to have a

component parallel to the direction of the component parallel to the direction of the motion of the particles in the head, and motion of the particles in the head, and

therefore to change their energy.therefore to change their energy.

J.B. Murphy, S. Krinsky, R. Gluckstern , Particle Accelerators 57, 9 (1997)

23

21

2223

21

1323

2

4

2220

2

2

1

8

1

216

1

23

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1

2sin

2cos1

16

1

][112

h

sG

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sG

h

sw

s

sceZE

UnitsSIhhs

if

s

Coulomb Free Space Infinite parallel plate shield

Tail Head Tail HeadTypical region

of interest

34320

3

11

2 s

ceZE

impedancevacuumZ 3770

00


The Analytical Expression The Analytical Expression for the SR Wakefieldfor the SR Wakefield


F.Sannibale

Simulated instability showing the Simulated instability showing the microbunching. microbunching.

Venturini, WarnocK SLACVenturini, WarnocK SLAC

The bunch distribution in a real ring is never completely smooth and shows a The bunch distribution in a real ring is never completely smooth and shows a modulated profile that changes randomly with time (noise).modulated profile that changes randomly with time (noise).

These micro-structures have characteristic length << than the bunch length and These micro-structures have characteristic length << than the bunch length and radiate CSR. The CSR wakefield modulates the energy of the neighbor particles radiate CSR. The CSR wakefield modulates the energy of the neighbor particles

that start to move inside the bunch due to the accelerator longitudinal dispersion. that start to move inside the bunch due to the accelerator longitudinal dispersion. Some particles move in the direction that increases the radiating micro-structure, Some particles move in the direction that increases the radiating micro-structure,

and thus increasing the CSR intensity and creating a gain mechanism. and thus increasing the CSR intensity and creating a gain mechanism.

Above a current threshold, this gain becomes large enough to sustain the micro-Above a current threshold, this gain becomes large enough to sustain the micro-bunching process against the decoherence effect due to the energy spread, and bunching process against the decoherence effect due to the energy spread, and

to generate an exponential growth of the micro-structure amplitude to generate an exponential growth of the micro-structure amplitude (up to saturation in the non linear regime of the instability).(up to saturation in the non linear regime of the instability).

Such an instability, often referred as the Such an instability, often referred as the micro-micro-bunching instability (MBI)bunching instability (MBI), is nothing else that a , is nothing else that a

SASE process in the THz regime.SASE process in the THz regime.

The MBI, for the case of storage rings, was The MBI, for the case of storage rings, was predicted by Sam Heifets and Gennady predicted by Sam Heifets and Gennady

Stupakov (Stupakov (PRST-AB 5, 054402, 2002PRST-AB 5, 054402, 2002) and ) and simulated by Marco Venturini and Bob Warnocksimulated by Marco Venturini and Bob Warnock

((PRL 89, 224802, 2002PRL 89, 224802, 2002))INFN - LNF, Frascati, Italy, July 10, 2008

Increasing theIncreasing theCurrent per Bunch.Current per Bunch.


F.Sannibale

In many electron storage rings In many electron storage rings around the world, strong random around the world, strong random

pulses (“bursts”) of CSR in the THz pulses (“bursts”) of CSR in the THz frequency range were observed for frequency range were observed for

high single bunch current.high single bunch current.

10.5mA

28.8mA

100ms806040200

Time (msec)

40.0mA

10 mA10 mA

29 mA29 mA

40 mA40 mA

Time (msec)Time (msec)

Bo

lom

eter

sig

nal

(V

)B

olo

met

er s

ign

al (

V)

ALS DataALS Data

G.L. Carr et al.:, NIMA 463, 387, (2001).

A. Anderson et al.:, Opt. Eng. 39, 3099, (2000).

M. Abo-Bakr et al.:, EPAC2000 Proceedings.

...

According to what said before, the According to what said before, the presence of the micro-bunching presence of the micro-bunching instability should be associated instability should be associated

with the emission of random with the emission of random "burst" of CSR."burst" of CSR.


Terahertz CSR Bursts Terahertz CSR Bursts CSR Studies


20

15

10

5

0

Burs

ting t

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(m

A)

2.01.81.61.41.2

Energy (GeV)

2.0 mm threshold 3.2 mm threshold

Model predictions

B

urst

th

resh

old

(mA

)

Energy (GeV)

J. Byrd, et. al. PRL 89, 224801, (2002).

wavelengthwavelength

The instability thresholds The instability thresholds predicted by the Heifets-Stupakov predicted by the Heifets-Stupakov

model for the instability were in model for the instability were in agreement with the measured agreement with the measured

thresholdsthresholds

Experiments at the ALS provided the experimental confirmation that the THz CSR Experiments at the ALS provided the experimental confirmation that the THz CSR bursts were associated with the MBI.bursts were associated with the MBI.

phasesyncmCmradiuselectronclassicalrfrequencyrevolutionf

numberpartitionlongJspreadenergynaturalmasselectronmUnitsSIr

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The beam becomes unstable if the single bunch current is larger than (SI Units):The beam becomes unstable if the single bunch current is larger than (SI Units):

The MBI dramatically limits the The MBI dramatically limits the maximum stable single bunch maximum stable single bunch

current in the short bunch regime!current in the short bunch regime!

32

3

31

20

03

0

2672

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rcm

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29

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23

21

021 cos

1

s

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K


CSR Instability ExperimentalCSR Instability ExperimentalVerification Verification


F.Sannibale

sdsEec

sS

eKsIs

s

sdsSssIVf

cs

zRFRFz

2

20

20

2

22

where S(s) is the Step Function Wakeand zo is the natural bunch length.

The current distribution The current distribution II((ss)) can be can becalculated by the Haissinski Equation:calculated by the Haissinski Equation:

Below the MBI threshold, the strongly Below the MBI threshold, the strongly nonlinear SR wake generates a nonlinear SR wake generates a

distortion of the parabolic potential well distortion of the parabolic potential well due to the RF cavity, and the bunch due to the RF cavity, and the bunch assumes non-Gaussian equilibrium assumes non-Gaussian equilibrium

distributions. distributions.

Tail Head

Free Space SR Wake

The free space SR wake generates the saw-tooth like distributions we were The free space SR wake generates the saw-tooth like distributions we were looking for!looking for!

(Bane, Krinsky and Murphy AIP Proc. 367, 1995)


Below the MBI ThresholdBelow the MBI ThresholdCSR Studies


Tail Head

Free SpaceSR Wake

Tail Head

ShieldedSR Wake

The vacuum chamber shielding reduces The vacuum chamber shielding reduces the CSR emitted powerthe CSR emitted power

In a CSR optimized source the shielding In a CSR optimized source the shielding effects must be minimized:effects must be minimized:


Vacuum Chamber ShieldingVacuum Chamber ShieldingCSR Studies


2.02 2

1

hhZ

J.B. Murphy, S. Krinsky, R. Gluckstern , Particle Accel. 57, 9 (1997)

Other wakes can be added to the CSR one in the calculation of the Other wakes can be added to the CSR one in the calculation of the equilibrium distribution by the Haissinski equation. From the distribution the equilibrium distribution by the Haissinski equation. From the distribution the

CSR factor and spectrum are then readily evaluated.CSR factor and spectrum are then readily evaluated.

Long range resistive wallLong range resistive wall: if : if not controlled it can reduce not controlled it can reduce the CSR intensity. In general the CSR intensity. In general larger gap (once more) and larger gap (once more) and

high conductivity chambers high conductivity chambers are preferred.are preferred.


Other WakefieldsOther WakefieldsCSR Studies


The wake fields due to the vacuum chamber of an accelerator can be modeled The wake fields due to the vacuum chamber of an accelerator can be modeled by using the by using the a generic impedance model:a generic impedance model:

In the short bunch regime (~ 1 ps), one finds that the effect of these wakes is In the short bunch regime (~ 1 ps), one finds that the effect of these wakes is usually negligible. usually negligible.

iXRZ

In 2002, The BESSY-II group In 2002, The BESSY-II group provided the first demonstration of provided the first demonstration of

stable CSR in a storage ring.stable CSR in a storage ring.Abo-Bakr Abo-Bakr et al.et al., PRL 88, 254801 (2002), , PRL 88, 254801 (2002),

and and M. Abo-Bakr M. Abo-Bakr et alet al., Phys. Rev. Lett. 90, 094801 (2003)., Phys. Rev. Lett. 90, 094801 (2003)


The BESSY II ResultsThe BESSY II ResultsCSR Studies


Very interesting characteristics of the BESSY results were:Very interesting characteristics of the BESSY results were:

- a very stable CSR flux (no presence of bursts), a very stable CSR flux (no presence of bursts),

- an impressive power radiated in the THz region,an impressive power radiated in the THz region,

- and a spectrum significantly broader than the one expected for a and a spectrum significantly broader than the one expected for a Gaussian distribution their bunch length.Gaussian distribution their bunch length.

We started a collaboration with them…We started a collaboration with them…

The understanding of the physics The understanding of the physics behind the BESSY results showed behind the BESSY results showed

the dominant role played in the short the dominant role played in the short bunch regime by the SR wake and bunch regime by the SR wake and

allowed to develop a model for allowed to develop a model for optimizing a storage ring as a optimizing a storage ring as a stablestable

source of THz CSR.source of THz CSR.

(F. Sannibale (F. Sannibale et alet al., PRL ., PRL 9393, 094801, 2004.), 094801, 2004.)(F.Sannibale (F.Sannibale et alet al., ICFA BD-Newsletter ., ICFA BD-Newsletter 3535, 2004), 2004)


UnderstandingUnderstandingthe BESSY Resultsthe BESSY Results


F.Sannibale

Such a model has been used for calculating the CSR performance of a number of Such a model has been used for calculating the CSR performance of a number of existing storage rings (DAexisting storage rings (DANE, Bates, SPEAR, …) and also for designing storage NE, Bates, SPEAR, …) and also for designing storage rings completely optimized for the generation of stable CSR in the THz frequency rings completely optimized for the generation of stable CSR in the THz frequency

range (CIRCE, IKNO).range (CIRCE, IKNO).

gG

EL

VfBNC

d

dP zRFRFb

237

3140

31

2231

G = 7.463C = 2.642 10-21 [SI units]

g()

In operation at the ALS since 1999, and in the last few years also at In operation at the ALS since 1999, and in the last few years also at BESSY II, SLS and UVSOR, …BESSY II, SLS and UVSOR, …

• A. A. Zholents, M. S. Zolotorev, Phys. Rev. Lett. A. A. Zholents, M. S. Zolotorev, Phys. Rev. Lett. 7676, 912, (1996), 912, (1996)

Beamline optimized for the generation of femtosecond x-ray pulsesBeamline optimized for the generation of femtosecond x-ray pulses


The `Femtoslicing’ ExperimentThe `Femtoslicing’ ExperimentCSR Studies

at the ALS and IKNO. F.Sannibale

Right beforeRight beforemodulationmodulation

Right afterRight aftermodulationmodulation

22

0

22

0

2exp

2exp 222

2

0

22

2321

~exp

2~

exp~

2

1,

LLM

LLM

zzE

E

zzE

E

LLM zz

E

Edzf

W

LLLM K

KEE

21

24

2

22

bandwidthradiationwiggler

bandwidthlaser

frequencylaser

parameterwigglerK

modulationenergyE

energypulselaserE

energybeamE

W

L

L

M

L

2

0

positionallongitudinarticlepz

ce

energybeamEEE

13714 02

00

For a few GeV electron beam, laser pulses with several mJ per pulse For a few GeV electron beam, laser pulses with several mJ per pulse are required. This limits the max rep-rate to the order of few KHzare required. This limits the max rep-rate to the order of few KHz


Energy ModulationEnergy ModulationCSR Studies


BL 5.3BL 5.3

BL 1.4BL 1.4Such density modulation Such density modulation

radiate intense CSR in the THz radiate intense CSR in the THz frequency rangefrequency range

gNgNd

dp

d

dP 21

2

cziezSdzg

Because of the ring longitudinal Because of the ring longitudinal dispersion, when the beam propagates dispersion, when the beam propagates

the energy modulation induces a density the energy modulation induces a density modulation.modulation.

The characteristic length of these The characteristic length of these modulations is ~ the laser pulse length modulations is ~ the laser pulse length (~100 fs) after the energy modulation, (~100 fs) after the energy modulation,

of the order of the ps after ~ a turn, of the order of the ps after ~ a turn, and it is completely absorbed by the and it is completely absorbed by the

bunch in the next few turns. bunch in the next few turns.


From Energy ModulationFrom Energy Modulationto CSR Emissionto CSR Emission


F.Sannibale

Our group at the ALS did the first experimental observation and Our group at the ALS did the first experimental observation and characterization of the CSR from the femtoslicing experiment:characterization of the CSR from the femtoslicing experiment:


THz CSR From Femtoslicing THz CSR From Femtoslicing CSR Studies


The CSR signal is now one of the main diagnostics for the tune-up for the The CSR signal is now one of the main diagnostics for the tune-up for the slicing experiment.slicing experiment.

The femtoslicing scheme, if optimized, could be used as a source of high The femtoslicing scheme, if optimized, could be used as a source of high energy per pulse THz radiation (~ 10 energy per pulse THz radiation (~ 10 J) for pump and probe experiments.J) for pump and probe experiments.

(J.M.Byrd (J.M.Byrd et alet al., PRL ., PRL 9696, 164801, 2006.), 164801, 2006.)

K. Holldack et al., PRL 96, 054801 (2006) and K. Holldack et al., PRST-AB 8, 040704 (2005).

Similar results have been obtained also at BESSY II:Similar results have been obtained also at BESSY II:

Wavefront for photons with wavenumberof 50 cm-1 at the window position

Window Position

Qualitative agreement.

Actual geometry difficult to simulate.


The ‘Waveguide’ EffectThe ‘Waveguide’ EffectCSR Studies


Physics Retreat, Sept. 22, 04

• Laser Modulation: 6 times the Laser Modulation: 6 times the energy spread energy spread

• Laser pulse width: 50 fs FWHMLaser pulse width: 50 fs FWHM• Distance modulator-radiator: 2.5 mDistance modulator-radiator: 2.5 m• Current per bunch: 10 mACurrent per bunch: 10 mA• Horizontal Acceptance 100 mrad Horizontal Acceptance 100 mrad

(single mode) (single mode)

[ps]

Longitudinal Distribution Modulation at Radiator

• Energy per pulse: 8.5 Energy per pulse: 8.5 J J • Electric field ~ 1 MV/cmElectric field ~ 1 MV/cm• Rep. rate: 10 - 100 kHzRep. rate: 10 - 100 kHz• Pulse shaping capabilityPulse shaping capability


Optimized CSR byOptimized CSR bySlicing (CIRCE)Slicing (CIRCE)


F.Sannibale

Physics Retreat, Sept. 22, 04

In the described femtoslicing experiment, severalIn the described femtoslicing experiment, several mutually synchronousmutually synchronous photon beams with very different wavelengths are simultaneously photon beams with very different wavelengths are simultaneously

available:available:

• THz CSR synchrotron radiation pulse with transform limited lengthTHz CSR synchrotron radiation pulse with transform limited length

This opens the possibility for many interesting combinations ofThis opens the possibility for many interesting combinations of ""pump pump and probeand probe" experiments where one of the beams is used for exciting the " experiments where one of the beams is used for exciting the sample while another is used for measuring its characteristics during the sample while another is used for measuring its characteristics during the

excitation transient.excitation transient.By varying the delay between the pulses, one can reconstruct the whole By varying the delay between the pulses, one can reconstruct the whole

sample response with resolution of the order of ~ 100 fs.sample response with resolution of the order of ~ 100 fs.

• x-ray pulses with ~ 100 fs lengthx-ray pulses with ~ 100 fs length

• Near-IR or visible ~ 100 fs pulse from the slicing laserNear-IR or visible ~ 100 fs pulse from the slicing laser


"Multicolor" Experiments"Multicolor" ExperimentsCapability Capability


F.Sannibale

Charge distribution at the “source” point

Laser Intensity

Spectrum at the“source” point

The example shows how by using a train of The example shows how by using a train of laser pulses instead of one single pulse one laser pulses instead of one single pulse one

can concentrate the CSR power within a can concentrate the CSR power within a narrow bandwidth.narrow bandwidth.

The number of pulses defines the bandwidth The number of pulses defines the bandwidth while the distance between pulses defines while the distance between pulses defines

the central frequency of the peak.the central frequency of the peak.

One additional interesting possibility of this One additional interesting possibility of this scheme is the ability of tailoring the electric scheme is the ability of tailoring the electric field of a terahertz pulse by an appropriate field of a terahertz pulse by an appropriate

shaping of the slicing laser pulse.shaping of the slicing laser pulse.

(J.M.Byrd (J.M.Byrd et alet al., PRL ., PRL 9696, 164801, 2006.), 164801, 2006.)

An example of application that could benefit An example of application that could benefit from this capability is the control of complex from this capability is the control of complex

chemical reactions where the shape of the chemical reactions where the shape of the exciting radiation is dynamically adjusted for exciting radiation is dynamically adjusted for

optimizing the reaction.optimizing the reaction.

In principle by this technique, arbitrary In principle by this technique, arbitrary spectrum shapes can be obtained spectrum shapes can be obtained


Tailoring the ShapeTailoring the Shapeof the THz Pulseof the THz Pulse


F.Sannibale

A. Mochihashi et al., UVSOR Workshop on THz CSR (September 2007) INFN - LNF, Frascati, Italy, July 10, 2008

Tailoring the THz PulseTailoring the THz Pulseis Really Possible!is Really Possible!


F.Sannibale

During the experiments for characterizing the CSR from femtoslicing, we During the experiments for characterizing the CSR from femtoslicing, we discovered that if the beam is sliced discovered that if the beam is sliced aboveabove the MBI threshold the the MBI threshold the

instability can be seeded.instability can be seeded.


Laser Seeding of the MBI Laser Seeding of the MBI CSR Studies


The MBI CSR bursts become The MBI CSR bursts become synchronous with the slicing laser and synchronous with the slicing laser and

the radiated THz power increases the radiated THz power increases exponentially with the current per exponentially with the current per

bunch.bunch.

In the framework of the Heifets-Stupakov MBI theory the In the framework of the Heifets-Stupakov MBI theory the micro-bunching can be represented by the combination of micro-bunching can be represented by the combination of

“modes” with shape:“modes” with shape:


A Model for the Seeded MBIA Model for the Seeded MBICSR Studies


kztie ˆ

In the “cold beam” approximation, the In the “cold beam” approximation, the authors derived an analytical expression authors derived an analytical expression

for the dispersion function between for the dispersion function between and and kk=2=2//. From that, the growth rate and the . From that, the growth rate and the

velocity for the mode can be calculated:velocity for the mode can be calculated:

I

IT

I

IT

I

IT

I

IT

I

IT

I

IT

I

IT

If one assumes, that the dynamic of the If one assumes, that the dynamic of the micro-bunch is dominated by the mode with micro-bunch is dominated by the mode with

larger growth rate then the for the CSR larger growth rate then the for the CSR power radiated by the micro-bunch will be:power radiated by the micro-bunch will be:

The comparison of this The comparison of this simple model predictions simple model predictions with the experimental data with the experimental data

showed a good agreement up showed a good agreement up to a certain current (~19 mA).to a certain current (~19 mA).


Comparing with DataComparing with DataCSR Studies


Above this value, the experimental points show a saturation effect that we Above this value, the experimental points show a saturation effect that we think is due to the fact that at high currents, the MBI goes in the nonlinear think is due to the fact that at high currents, the MBI goes in the nonlinear

regime before the perturbation arrives at the threshold point.regime before the perturbation arrives at the threshold point.

J.M.Byrd J.M.Byrd et alet al, PRL , PRL 9797, 074802, 2006, 074802, 2006

Heifets and Stupakov studied the case by considering the combination of Heifets and Stupakov studied the case by considering the combination of all unstable modes (SLAC-PUB-11815, 2006).all unstable modes (SLAC-PUB-11815, 2006).


Possible ApplicationsPossible ApplicationsCSR Studies


At saturation, the average power of At saturation, the average power of the seeded CSR burst is about two the seeded CSR burst is about two orders of magnitude larger than for orders of magnitude larger than for the “conventional” slicing case, but the “conventional” slicing case, but shows very large power fluctuations.shows very large power fluctuations.

Pump and probe and other Pump and probe and other experiments not requiring shot to experiments not requiring shot to

shot intensity stability could benefit shot intensity stability could benefit from this several orders of magnitude from this several orders of magnitude

increase in power.increase in power.

In a speculative scenario, part of the THz signal can be brought back into the In a speculative scenario, part of the THz signal can be brought back into the ring to co-propagate the bending magnet with a subsequent electron bunch, ring to co-propagate the bending magnet with a subsequent electron bunch, modulating its energy and seeding the MBI that generates a new burst that is modulating its energy and seeding the MBI that generates a new burst that is

then used in the loop for seeding a new fresh bunch. By this process, that then used in the loop for seeding a new fresh bunch. By this process, that continues involving all the bunches, one can in principle bring the CSR continues involving all the bunches, one can in principle bring the CSR

emission to a stable high power saturation regime where all the bunches emission to a stable high power saturation regime where all the bunches radiate coherently.radiate coherently.

Other FEL-like schemes exploiting the MBI gain are possible as well.Other FEL-like schemes exploiting the MBI gain are possible as well.

The graph shows how the 1 kHz power The graph shows how the 1 kHz power (synchronous with the laser) loses the (synchronous with the laser) loses the

quadratic dependence for currents quadratic dependence for currents above the MBI threshold at ~13 mA.above the MBI threshold at ~13 mA.


The IKNOThe IKNOInfrastructure ProposalInfrastructure Proposal


F.Sannibale

• IKNO is a multi-user facility IKNO is a multi-user facility completely completely optimized for the THz optimized for the THz

CSR productionCSR production and exploits all the and exploits all the described techniques for generating described techniques for generating

extremely powerful radiation on a extremely powerful radiation on a very broad spectrum.very broad spectrum.

• IKNO also produces an IKNO also produces an incoherent incoherent photon flux extending up to the VUV photon flux extending up to the VUV frequenciesfrequencies comparable with the one comparable with the one

of existing 3rd generation light of existing 3rd generation light sourcessources

Present IKNO Collaboration:Present IKNO Collaboration: P. Innocenzi, A. Marcelli, F. Sannibale.P. Innocenzi, A. Marcelli, F. Sannibale.

IKNOIKNO (Innovation and KNOwledge) is also the ancient name of Sardinia and in (Innovation and KNOwledge) is also the ancient name of Sardinia and in our proposal to the our proposal to the Italian Roadmap of the Research InfrastructureItalian Roadmap of the Research Infrastructure, is the , is the

name of the Italian infrastructure, proposed in Sardinia to host this new high name of the Italian infrastructure, proposed in Sardinia to host this new high performance electron storage ring. performance electron storage ring.

Physics Retreat, Sept. 22, 04Fernando Sannibale

More CIRCE STORYMore CIRCE STORY


The IKNO Storage RingThe IKNO Storage RingCSR Studies


The IKNO storage ring is a more compact version of CIRCE (the LBNL The IKNO storage ring is a more compact version of CIRCE (the LBNL proposal).proposal).

It includes six periods (DBA cells) It includes six periods (DBA cells) with six 3.1 m straight sections.with six 3.1 m straight sections.

Sextupole and octupole magnets Sextupole and octupole magnets allow full control of the ring allow full control of the ring

nonlinear dynamics.nonlinear dynamics.


IKNO: The OptimizedIKNO: The OptimizedCSR SourceCSR Source


F.Sannibale

In the In the ultra-stable modeultra-stable mode, IKNO generates a photon flux of CSR many order , IKNO generates a photon flux of CSR many order of magnitude higher than in existing 3rd generation light sources.of magnitude higher than in existing 3rd generation light sources.

The 3.1 m straight sections, allow for The 3.1 m straight sections, allow for CSR for femtoslicingCSR for femtoslicing systems, systems, extending the spectrum to few tens of THz, allowing for pulse shaping extending the spectrum to few tens of THz, allowing for pulse shaping

and opening to multicolor pump and probe experimentsand opening to multicolor pump and probe experiments

Physics Retreat, Sept. 22, 04Fernando Sannibale

More CIRCE STORYMore CIRCE STORY


The IKNO As a Source ofThe IKNO As a Source ofIncoherent UV SR Incoherent UV SR


F.Sannibale

The bending magnet ports and the 3.1 m straight sections, can also be The bending magnet ports and the 3.1 m straight sections, can also be used for generating a powerful flux of incoherent synchrotron radiation used for generating a powerful flux of incoherent synchrotron radiation

in the UV-VUV frequency in the UV-VUV frequency rangerange..

Coherent Synchrotron Radiation Studies at the Advanced Light Source and the IKNO proposal

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Transcript of Coherent Synchrotron Radiation Studies at the Advanced Light Source and the IKNO proposal