V.N. Litvinenko, 30 th FEL Conference, Gyeongju, Korea, August 28, 2008 PROGRESS WITH FEL-BASED...

V.N. Litvinenko, 30th FEL Conference, Gyeongju, Korea, August 28, 2008

PROGRESS WITH FEL-BASED COHERENT ELECTRON COOLING

Vladimir N. Litvinenko, Ilan Ben Zvi, Michael Blaskiewicz, Yue Hao, Dmitry Kayran, Eduard Pozdeyev, Gang Wang

Brookhaven National Laboratory, Upton, NY 11973, USA

Oleg A. Shevchenko, Nikolay A. VinokurovBudker Institute of Nuclear Physics, Novosibirsk, Russia

George I. Bell, David L. Bruhwiler, Andrey SobolTech-X Corp., Boulder, CO 80303, USA

Yaroslav S. Derbenev, TJNAF, Newport News, VA, USA

Sven Reiche, UCLA, Los Angelis, CA, USA


Content* What is Coherent electron Cooling? * Why it is needed?* Our plan of the comprehensive studies* Progress with Modulator, FEL, Kicker, PoP* Conclusions

Cooling intense high-energy hadron beams remains a major challenge for accelerator physics. Synchrotron radiation is too feeble, while efficiency of two other cooling methods falls rapidly either at high bunch intensities (i.e. stochastic cooling of protons) or at high energies (i.e. e-cooling). Possibility of coherent electron cooling based on high-gain FEL and ERL was presented at last FEL conference [1]. This scheme promises significant increases in luminosities of modern high-energy hadron and electron-hadron colliders, such as LHC and eRHIC. In this talk we present progress in development of this concept, results of analytical and numerical evaluation of the concept as well our prediction for LHC and RHIC. We also present layout for proof-of-principle experiment at RHIC using existing R&D ERL. In this paper we report on the progress in the development of the scheme of coherent electron cooling (CeC) since a specific scheme and its theoretical evaluation were proposed about an year ago [1].

[1] V.N. Litvinenko, Y.S. Derbenev, Proc. of FEL’07 Conference, Novosibirsk, Russia, August 27-31, 2007, p.268 http://accelconf.web.cern.ch/accelconf/f07

http://accelconf.web.cern.ch/accelconf/f07


Coherent Electron Cooling

Modulator

Kicker

Dispersion section ( for hadrons)

Electrons

Hadrons

l2l1 High gain FEL (for electrons)

Eh

E < Eh

E > Eh

Eh

E < Eh

E > Eh

Modulator Kicker

Electrons

Hadrons

l2

l1

High gain FEL (for electrons) / Dispersion section ( for hadrons)


Decrements for hadron beamswith coherent electron cooling

Machine SpeciesEnergy GeV/n

Trad.StochasticCooling,

hrs

Synchrotron radiation, hrs

Trad.Electron cooling

hrs

CoherentElectron

Cooling, hrs 1D/3D

RHIC PoP

Au 40 - - - 0.02/0.06

eRHIC Au 130 ~1 20,961 ~ 1 0.015/0.05

eRHIC p 325 ~100 40,246 > 30 0.1/0.3

LHC p 7,000 ~ 1,000 13/26 0.3/<1


Comprehensive studies Analytical, Numerical and Computer Tools to:1. find reaction (distortion of the distribution function of

electrons) on a presence of moving hadron inside an electron beam

2a. Find how an arbitrary f is amplified in high-gain FEL

2b. Design cost effective lattice for hadrons + coupling3. Find how the amplified reaction of the e-beam acts on the hadron (including coupling to transverse motion)

fe

t fe

v eE m fe

r v 0;

r h (t)

r o

v ht;

E 4ene

Zne

r r h (t) fed

v 3

.

f fo f

fexit (r ,p ,t) fo exit (

r ,p ) K

r ,p ,r 1,p 1,t t1 f (

r 1,p 1, t1)d

r 1 dp 1dt1


Modulator Dimensionless equations of motion

f e

t f e

v eE

m f e

r v 0;

r h (t)

r o

v h t;

E 4ene

Z

ne

r r h (t) fed

v 3

.

R v

vz

; Tvhx

vz

; Lvhz

vz

; Z

4neR2s3

;

Aa

s; X

xho

a;Y

yho

a.

t /p; v =vz

; r

vz/p; p

2 4e2ne

m

Parameters of the problem

fe

fe

g fe

0;

g

eE

mp2s

;

n

g Z

s3ne

i(t) fed3 ;

n .

s rDzvz

/p

+Ze


Perturbation caused by a hadron (co-moving frame)Analytical: for Lorentzian electron plasma, G. Wang and M. Blaskiewicz, Phys Rev E 78, 026413 (2008)

Numerical (VORPAL @ TechX)

Ion at rest

vhz 10 vz

˜ n r ,t Znop

3

2vxvyvz

sin 2 x - vhx /p

rDx

2

y - vhy /p

rDy

2

z - vhz /p

rDz

2

2

0

pt

d


QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

VORPAL @ TechX






Modulator KickerDispersion section ( for hadrons)

Electrons

Hadrons

l2

l1 High gain FEL (for electrons)

Eh

E < Eh

E > Eh

Eh

E < Eh

E > Eh

CeC: FEL response

f input(r ,p ,t) fo input(

r ,p )f (

r ,p ,t)

fexit (r ,p ,t) fo exit (

r ,p ) K

r ,p ,r 1,p 1, t t1 f (

r 1,p 1, t1)d

r 1 dp 1dt1

1D FEL response

exit (t;z) = o G ;z (t ;0)d

G ;z Re ˜ G z e io

0 2c

o

;


FEL’s Green Function 1D - analytical approach3D - 3D FEL codes RON and Genesis 1.3

FEL parameters for Genesis 1.3 and RON simulations

FEL gain length: 1 m (power), 2m (amplitude)

Main FEL parameters for eRHIC with 250 GeV protons

Energy, MeV 136.2 266.45

Peak current, A 100 o, nm 700

Bunchlength, psec 50 w, cm 5

Emittance, norm 5 mm mrad aw 0.994

Energy spread 0.03% Wiggler Helical0

0.2

0.4

0.6

0.8

1

0 50 100 150 200 250 300 350 400

RON

Genesis

0

0.2

0.4

0.6

0.8

1

Mod

ulat

ion,

nor

mal

ized

Slice number, in unit of 0

Modulation after 20m of FEL

G ;z Re ˜ G z e io


Response - 1D FEL

E.L.Saldin, E.A.Schneidmiller, M.V.Yurkov, The Physics of Free Electron Lasers, Springer, 1999


Response - 1D FEL after 10 gain lengths

-500

0

500

1000

1500

2000

2500

3000

3500

-2 0 2 4 6 8 10 12

Re ImAmplitude

Gre

en F

unct

ion

In units of slippage per gain lenght

Green-functionenvelope (Abs, Re and Im)

Maximum located at 3.744 slippage units,(i.e. just a bit further that expected 3 and 1/3)

The Green function (with oscillations) had effective RMS length of 1.48 slippage units.

vg c 2 vz

3c 1

1 aw2

3o2


Genesis: 3D FEL

Evolution of the maximum bunching in the e-beam and the FEL power simulated by Genesis. The location of the maxima, both for the optical power and the bunching progresses with a lower speed compared with prediction by 1D theory, i.e. electrons carry ~75% for the “information”

Evolution of the maxima locations in the e-beam bunching and the FEL power simulated by Genesis.Gain length for the optical power is 1 m (20 periods) and for the amplitude/modulation is 2m (40 periods)

vg c 3 vz

4c 1

3

8

1 aw2

o2

©Y.Hao, V.Litvinenko


3D FEL, RON codeRHIC 250 GeV, FEL @ 0.7 m,

gain length - 40 periods (amplitude). 20 (power)

©O.Shevchenko

20 GL

18 GL

16 GL

-300

-200

-100

0

100

200

300

400

500

-100 0 100 200 300 400

Data J10c4Re(

mod)

Im(mod

)

E

mod

, a.u

.

Slice


Genesis: 3D FEL

Evolution of the normalized bunching envelope

The Green function (with oscillations) after 10 gain-lengths had also smaller effective RMS length [1] of 0.96 slippage units (i.e. about 38 optical wavelengths, or 27 microns

0

0.2

0.4

0.6

0.8

1

0 50 100 150 200 250 300

bunch_norm

Value, 0mValue, 2mValue, 4mValue, 6mValue, 8mValue, 10mValue, 12mValue, 14mValue, 16mValue, 18mValue, 20mValue, 22mValue, 24m

m

ax

Slippage, in units of 0

©Y.Hao, V.Litvinenko, S.Reiche

10-8

10-7

10-6

10-5

0.0001

0.001

0.01

0.1

1

0 100 200 300 400 500

Bunching, normalized amplitudeValue, 0mValue, 2mValue, 4mValue, 6mValue, 8mValue, 10mValue, 12mValue, 14mValue, 16mValue, 18mValue, 20mValue, 22mValue, 24m


0.0001

0.01

1

100

104

106

0 100 200 300 400 500

Optical powerValue, 0mValue, 2mValue, 4mValue, 6mValue, 8mValue, 10mValue, 12mValue, 14mValue, 16mValue, 18mValue, 20mValue, 22mValue, 24mP

ower


Evolution of the bunching and optical power envelopes(vertical scale is logarithmic)


Kicker: output from Genesis propagated for 25 m

0m 5m 10m

25m

©I.Ben Zvi0

0.1

0.2

0.3

0.4

0.5

0.6

0 5 10 15 20 25

Bunching in the Kicker, 700 nm

Bunching

Bu

nch

ing

Distance, m

QuickTime™ and aTIFF (LZW) decompressor


15m

QuickTime™ and aTIFF (LZW) decompressor


20m


IR-2 layout for Coherent Electron Cooling proof-of-principle experiment


Conclusions• These initial studies did not find any phenomena,

which challenges the concept of CeC• Our initial CeC estimations passed the test• At the same time, we found a number of new and

interesting details to pursue further• Future studies will refine the model and improve the

quality of predictions• We plan to test validity of the concept

experimentally in Proof-of-Principle experiment using BNL’s R&D ERL installed in one of available IPs at RHIC

• Supported by office on Nuclear Physics, US DoE

V.N. Litvinenko, 30 th FEL Conference, Gyeongju, Korea, August 28, 2008 PROGRESS WITH FEL-BASED...

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Transcript of V.N. Litvinenko, 30 th FEL Conference, Gyeongju, Korea, August 28, 2008 PROGRESS WITH FEL-BASED...