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RHIC ERHIC E--cooling Collaboration Workshop, May 24cooling Collaboration Workshop, May 24--26, 200626, 2006

Electron beam transport and performance in Electron beam transport and performance in ERL for RHIC electron coolingERL for RHIC electron cooling

Dmitry Kayran, Xiangyun Chang

Brookhaven National Laboratory

RHIC e-Cooling Workshop May 24, 2006


OutlineOutline

• Layout of e-cooling facility• High energy beam dynamics (emittances ≈ constant)• Low energy beam dynamics • Start to end tracking• Summary


Part 1Part 1

• Layout of e-cooling facility• High energy beam dynamic (emittances ≈ constant)• Low Energy Beam Dynamics • Start to end tracking• Summary


Layout of RHIC with electron cooler at IP2Layout of RHIC with electron cooler at IP2

Linac

EBIS Booster

AGS

RHIC II

Electroncooling

IP2

*) V.N.Litvinenko et al. High Current Energy Recovery Linac at BNL. Proceedings of the FEL 2004 Conference, 570-573.


A 3D site view of the RHIC electron cooler at IP2. A 3D site view of the RHIC electron cooler at IP2.

ERL

RHIC triplet

Cooling region

100 m

RHIC triplet

100 m at IP2 between triplets is sufficient for cooling

ERL


EE--cooler ERL matched to RHICcooler ERL matched to RHIC

RHIC triplet

ERL


from RHIC

30 MeV

54.5 MeV

4.7 MeVLaser

54.5 MeV

1

2 3

44’

5

7

8

to RHIC

EE--cooler: 2 passes ERL layoutcooler: 2 passes ERL layout

1. SRF Gun,

2. Injection merger line

3. SRF Linac two 5-cell cavities

and 3rd harmonic cavity

4, 4’. 180° achromatic turns

6

5, 6. Transport lines to and from

RHIC,

7. Ejection line and beam dump

8. Short-cut for independent run of

the ERL.


Part 2Part 2



Loop lattice functions (MAD8 output)Loop lattice functions (MAD8 output)

First pass

KEnergy=30MeV

Second pass

KEnergy=54.3 MeV


EE--cooling ERL attached to the RHIC at 2 o’clock IPcooling ERL attached to the RHIC at 2 o’clock IP

`100 m

IP2

ER

L

undulator undulator

e-

e-

e-

RHIC triplet RHIC triplet

Each electron beam cools ion beam in yellow ring then in blue ring.

The flight time between centers of the cooling sections is integral number of ion beam time sequence (1/9.383MHz=106.6 nsec)


Cooling region: Cooling region: undulatorundulator is needed to suppress effects of is needed to suppress effects of recombination .recombination .

`100 m

IP2

ER

L

undulator undulator

e-

e-

e-


βions βelectronns

β ele

ctro

nns

β ion

s

Helical Undulator

Undulator parameters:

B=10 Gs

β0=260 m, at Ee=55 MeV

Beta functions

Ions: black 400 m∆βions=+/-2m

Electrons: red 500 m∆βelectrons=+/-6m


Matching two ringsMatching two rings

`100 m

IP2

ER

L

undulator undulator

e-

e-

e-


In cooling section

βx=βy=500 m

Dx=Dy=0

5 m


Part 3Part 3



Vertical injector layoutVertical injector layout

10º

-10º-20º

20º

1.5 CELL GUN 1st 5 CELLS CAVITY

48 cm

81.6 cm40 cm

40 cm

e-, 4.7 MeV

490 cm

e-, 18 MeV

e-, 30 MeV54.3 MeV

SRF Gun MERGER


SRF Gun SRF Gun

Z (cm)

R (c

m) Frequancy: 703.75 MHz

Maximum field on axis: 29.5 MV/m

Maximum field on surface: 49.3(MV/m)

Electric field profile: results of SUPERISH simulation


Mergers used in operational Mergers used in operational ERLsERLs

Budker Institute of Nuclear Physics (BINP), Novosibirsk, Russia

Tomas Jefferson National Accelerator Facility (TJNAF) Newport News, VA, USA

Japan Atomic Energy Research Institute (JAERI), Tokai-mura, Ibaraki, Japan

Beam parameters after the mergers in operation ERLs

35/26 µ10/10 µ30/30 µεN_x/εN_x

ThermionicPhotocathodeThermionicGun type

2.5 MeV9.1 MeV2 MeVInj.energy

0.5 nC0.135 nC1.5 nCQbunch

9.4 psec2 psec150 psec∆Tbunch,

Dog-leg, with quads strong focusing

Three dipole strong focusing

Chicane with quad sstrongfocusing

Merger type

JAERITJNAFBINP


Evolution of horizontal and vertical normalized emittances in the four systems: the axially symmetric system (straight line), the Zigzag, the Chicane and the Dog-leg.*)

*) Vladimir N. Litvinenko, Ryoichi Hajima, Dmitry Kayran. Merger design for ERLs. Nuclear Instruments and Methods in Physics Research A 557 (2006), pp. 165 - 175.

Compare of different merger systemsCompare of different merger systems

10º

-10º

-20º

20º

1.5 CELL GUNSC 5 CELLS CAVITY

63 cm

81.6 cm40 cm

40 cm

e-, 3.7 MeV

490 cm

e-, 18 MeV

e-, 18 MeV

12.4º 12.4º-11.4º -11.4º

1.5 CELL GUNSC 5 CELLS CAVITY

63 cm 96.6 cm 47.5 cm47.5 cm

e-, 3.7 MeV

490 cme-, 18 MeV

12.4º -12.4º-11.4º 11.4º

1.5 CELL GUN

SC 5 CELLS CAVITY

63 cm 96.6 cm

47.5 cm

e-, 3.7 MeV

490 cm

47.5 cm

0

5

10

15

20

25

0 100 200 300 400 500 600 700 800

εx, straight

εy, straight

εx, Zigzag

εy, Zigzag

εx, Chicane

εy, Chicane

εx, Dog-leg

εy, Dog-leg

ε norm

, µm

. rad

z, cm

Q=1 nc

KEinj=3.5 MeV


Acceleration gain for different passing Acceleration gain for different passing linaclinac phase with and without phase with and without 33--rd harmonic cavityrd harmonic cavity..

-1

-0.5

0

0.5

1

-90 0 90

Phase, deg

E/Em

ax

Fundamental frequency3rd hormonicCombine function

Our beam is sitting here length:

+/- 10 degrees

Without 3rd harmonic

∆E/E≈ 1.7x10-3

Requirement is 3x10-4

3rd harmonic cavity is needed!


TestTest--bed systembed system

30 MEVLinac

3rd harmonic cavitiesRecovered beams

1.5 cell Gun

Solenoid Linac 54.3 MEV

0

5

10

15

20

25

30

35

0 500 1000 1500 2000Z, cm

Nor

milize

d em

ittan

ces, m

m m

rad

exeyBeer-can distribution

R=5.5 mm

L=92 psec

εth =1.6 mm mrad

εx/εy=3.0/2.7 mm mrad


Longitudinal phase space at working energy 54.3 Longitudinal phase space at working energy 54.3 MeVMeV

rms(∆E/E)<2 10-4

dE, k

eV

dPhi, deg


Summary for testSummary for test--bed studiesbed studies

2.9x10-4

5.3/4.9

54.3

5

Gaussian EllipticalBeer-can

1.8x10-42.5x10-43x10-4RMS Energy spread, δE/E

2.5/2.03.0/2.7<4Transverse emittances, εx/εy mm*mrad

54.354.354.3Energy, MeV

555Charge per bunch, nC

Parmela simulation results*)Required for cooling

*) More details of test-bed studies will be discussed by Xiangyun Chang tomorrow.

The parameters of the electron beams for different initial distribution at the exit of the test-bed system at required kinetic energy 54.3 MeV


Part 4Part 4



30 MeV

54.5 MeV

4.7 MeVLaser

1

2 3

44’

5

7

8

Layout of system for startLayout of system for start--toto--end trackingend tracking6


Result of startResult of start--toto--end trackingend tracking

0

5

10

15

20

25

30

35

40

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000Z, cm

Emitt

ance

, mm

mra

d

exey

ex=2.9 mm mradey=3.2 mm mrad

Transverse normalized Transverse normalized emittancesemittances evolution from cathode to the dumpevolution from cathode to the dump

Beer-can

R=5.5 mm

L=92 psec

εth =1.6 mm mrad E-c

oolin

g re

gion


Result of startResult of start--toto--end tracking (cont.)end tracking (cont.)

0

0.02

0.04

0.06

0.08

0.1

0.12

-1000 1000 3000 5000 7000 9000 11000

Z, cm

RM

S En

ergy

spr

ead

0

10

20

30

40

50

60

KE,

MeV

DKE/KE KE

Energy spread and avrage energy evaluationEnergy spread and avrage energy evaluation

E-c

oolin

g re

gion

KE = 54.3 MeV∆E/E = 3.8 E-04


Transverse Beam Break Up studies of two loops ERLTransverse Beam Break Up studies of two loops ERL

From Eduard Pozdeyev (Jefferson Lab) studies of the two loops ERL with two 5 Cell cavities :

The threshold average current is always more than 1.5 A.

Which is sufficiently for e-cooling operation: average current 0.05 A.


OutlineOutline



0.78>1RMS Bunch length, cm

Beer-can (Teff=0.4eV)

3.8x10-43x10-4RMS Energy spread, δE/E

3.2/2.7<4Transverse emittances, εx/εymm*mrad

1500>50Threshold average current, mA54.354.3Energy, MeV


Parmela simulation results*)Required for cooling

SummarySummary

The parameters of the electron beams for different initial distribution at the exit of the test-bed system at required kinetic energy 54.3 MeV

The results of the beam dynamics studies according of start-to-end PARMELA simulation are very promising and provide the needed parameters for RHIC e-cooling project.


Things to doThings to do

Start to End simulation has to be done using magnets (solenoids, dipoles, quads) with real edges in real boundary conditionsWake field effects has to be well understood. Start to end simulation should include ions-electrons interaction impactLongitudinal instability

Many R&D should be done

A List of R&D items should be developed by this workshop


Thank you!


20 20 MeVMeV High Current High Brightness R&D ERL : High Current High Brightness R&D ERL : layout in 912layout in 912


R&D ERL and ER&D ERL and E--Cooler beam parametersCooler beam parameters

0.260.151.0Injected/ejected beam power, MW

211Numbers of passes

High charge per bunch

High averagecurrent

Required for cooling

R&D prototype ERL

3x10-3

<5

500

20/2.5

1.4

5x10-3

<10

50

20/3.0

5

10-3Energy spread, δE/E

<5Transverse emittances, mm*mrad

50Average current, mA

54.3/5.2Energy maximum/injection, MeV


•The prototype ERL will demonstrate the main parameters of the e-beam required for e-cooling• The prototype will also serve as a test bed for studying issues relevant for very high current ERLs

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