| ppt |

Contents

• Introduction• Technological highlights in superconducting low- linacs • Superconducting linacs for RIB acceleration• Example of multicharge transport in EURISOL SRL• Conclusions

Alberto Facco

INFN-Laboratori Nazionali di Legnaro

Acceleration of RIB using linacs

Moriond Meeting 17-21/3/2003

Ideal RIB accelerator requirements

• Acceleration of all possible radioactive beams

• All possible final energies up to ~ 100 MeV/u, finely tuneable

• Capability of acceleration of singly charged ions

• Very good beam quality up to at least 10 MeV/u

• Affordable construction and operation cost

• reliability, easy maintenance, easy beam set-up and operation, etc.


RIB accelerators special constraints

• Variable q/A beams

– Efficiency in a wide range of q/A

– Wide acceptance in : acceleration with variable velocity profiles is

desirable

• Very low current beams

– negligible beam loading: Rf power efficiency

– Stability and large acceptance

– Very high transmission efficiency, aiming to 100%


Independently-phased Superconducting Cavity Linacs virtues

•Wide velocity and q/A acceptance

•Modularity: all final energies can be reached, with fine tunability

•Excellent beam quality

•Transmission efficiency limited only by charge selection after stripping

Recent achievements in the field:

Multicharge beam transport

High acceleration gradient

high transmission efficiency after stripping

Competitive construction and operation cost


Technological highlights in superconducting low- linacs


Superconducting QWR’s(optimum range 0.03<<0.3 and 50<f<200 MHz)

LNL PIAVE 80 MHz, =0.047 QWR

LNL 80 MHz, =0.055 cryostatMechanical damper

1.00E+07

1.00E+08

1.00E+09

1.00E+10

0 1 2 3 4 5 6 7 8 9 10 11 12

Ea (MV/m)

Q

Z16 PIAVEZ4 ALPIQ @ 7WQ @ 14WQ @ 21W

new requirements

old requirements

next requirements?


Best ALPI and PIAVE

low beta cavities results

Superconducting QWR family

TRIUMF ISAC-II 106 MHz, =0.072 prototype


4.2 k test results

• Design gradient: 6 MV/m @7W• reached 7 MV/m with <10W

ISAC-II =0.072 cavity

Superconducting Spoke resonators (optimum range 0.2<<0.5 and f350

MHz)


ANL =0.3 and = 0.4prototypes

LANL =0.2 prototypes

Superconducting RFQ’s

1.E+07

1.E+08

1.E+09

0 5 10 15 20 25 30

0

5

10

15

20

25

30

35

40

45

Peak surface field [MV/m]

Q Pdiss [W]

design specs

•Compactness•CW operation•High efficiency

LNL Superconducting SRFQ2A/q=8.5, 0.0255<<0.0355


6 MV/m already achieved in existing linacs

7 MV/m seems very realistic for future accelerators


Low - SC linacs design gradient

EM steering in QWR’s

-3.00E+06

0.00E+00

3.00E+06

-120 -60 0 60 120z, mm

E,

V/m

-5.00E-03

-2.50E-03

0.00E+00

2.50E-03

5.00E-03

Bx,

TEzEy (x10)

Bx

•The steering is proportional to the energy gain

•The magnetic contribution is dominant

Eurisol Town Meeting, Abano 24-25/1/2002

0.1 0.2 0.3 0.40

0.05

0.1

0.15

0.2

0.25

Energy gain (MeV/u)beam deflection (mrad)

beta

Me

v/U

, mra

d

Quarter Wave Resonatorswith dipole correction

A. Facco - SPES meeting –LNL 11-3-2003

•MSU QWR 161 MHz for RIA(MSU-LNLcollaboration)

QWR steering : 161 MHz standard shape (top)161 MHz corrected

•ANL QWR 115 MHz for RIA


•Proposed and demonstrated at ANL (in ATLAS)

•Studied at

•ANL and MSU for RIA (driver and reaccelerator linacs)

•TRIUMF for the ISAC-II reaccelerator

• LNL for the Eurisol reaccelerator

Important tool to achieve high efficiency in both

transmission and acceleration


00 coscos A

q

A

qn

n


q1q2

q3

q4

W

•Ions with different charge state receive the same acceleration if their synchronous phase is properly chosen

•Many different charge states can be transported simultaneously

•Most of the beam particles can be captured after stripping

W=qEaLT()cos




=-150 =-1000 =-200=-150

beam

Phase synchronization after the first stripper, at the beginning of the SRL ME section. Top: first cryostat (see fig 3) and the reference acceleration phase at each of the cavities. Bottom: longitudinal phase space, in energy spread (%) as function of phase (deg) in different position along the cryostat. The cavities frequency is 160 MHz. The 5 charge states of the beam particles are represented by different colors.


Examples of superconducting

linacs for RIB acceleration

ISAC post-accelerator at TRIUMF (operating, under completion)

ISAC-I, in operation•NC Linac up to 1.5 MeV/u

ISAC-II, under construction•SC linac ~43 MV•Rib energy up to ~6 MeV/u

•A150•1 or 2 carbon foil strippers•Multicharge transport•Charge breeder for A>30


ISAC post-accelerator special components•35.3 MHz RFQ A/q 30 (8m long)•106 MHz Separate function DTL

•SC QWRs•70.7 MHz =0.042 •106 MHz, =0.072 (under construction)•106 MHz =0.105

ANL-RIA type SC solenoidsInside cryostats


The RIA RIB facility


RIA (MSU version)

RIA driver superconducting cavities under development at ANL

RIA Driver SC linac:•Ion beams of all masses•400 MeV/u Uranium

The ANL-RIA post-accelerator (proposed as injector of the existing ATLAS SC linac)


• No charge breeder, accepting q=1+

• Masses 66<A< 240 need He gas stripper at ~10 keV/u to reach A/q66

• Carbon foil stripper at 600 keV/u to reach A/q8.3

• 3 NC RFQs (2 on a 400 kV platform)

• 62 SC cavities + SC solenoids

• Output energy 1.4 MeV/u

• Very efficient in transmission, >30% up to the 2nd stripper

• Good emittance

• Very conservative design gradient

• Beam injected into ATLAS ( ~50 MV)

RIA post-accelerator special components

12 MHz Hybrid rfq

• R&D in an advanced stage for RFQ and SC solenoids • 4-gap SC cavity technology well established• ATLAS working since 20 years


4 gap superconducting QWR

15 T superconducting solenoid with steerers

EURISOL SRL (preliminary project)

• 2 intermediate stripping stations to increase linac efficiency and reduce linac length

• 3 main extraction lines for low, medium and high energy experiments

• Multicharge beam transport to maximize transmission up to 100 MeV/u

• Acceleration with no stripping and full intensity up to 60 MeV/u


Cavity type QWR QWR QWR QWR HWR units

f 80 80 160 240 320 MHz

0 0.047 0.055 0.11 0.17 0.28

Ep/ Ea 4.89 4.81 4.93 5.17 3.7

Hp/Ea 103 101 108 110 106 Gauss/(MV/m)

Rs Q 14.9 14.9 28.3 38.4 61.7

Rsh / Q 1640 1660 1480 1470 1200 /m

U/ Ea2 0.121 0.120 0.0670 0.0452 0.093 J/(MV/m)2

Eff. length 0.18 0.18 0.18 0.18 0.223 m

Design Ea 7 7 7 7 7 MV/m

Cryo power allowed 10 10 10 10 10 W

n. required 3 15 24 37 160

SRL cavity parameters

QWR HWR

* Calculated by means of the code HFSS


SRL modulesSRFQ section

– 3 LNL type superconducting RFQ’s in 2 cryostats

– Design A/q 10 (up to 132Sn13+)

– Ein =2.3 keV/u, Eout =670 keV/u

QWR-HWR modules– Cryostat

• 4 QWR’s (section I and II) at 7 MV/m

• 8 HWR’s (section III) at 7 MV/m

• 1 superconducting solenoids at B<15 T

– Diagnostics box


Diagnostic box 200 mm

Bellows 100 mm Valve

70 mm QWR 232 mm

Solenoid 300 mm

Medium energy section

cryostats


Bellows 100 mm

Valve 70 mm HWR

280 mm Solenoid 450 mm

High energy section

cryostats

Figure 3: The most common cryostat modules, top view; layout used in the beam dynamics simulation for the three energy sections. The components length along the beam axis is given in the figure (NOT to scale).


Bellows 100 mm Valve

70 mm QWR 232 mm

Solenoid 300 mm

Medium energy section

cryostats


Bellows 100 mm

Valve 70 mm HWR

280 mm Solenoid 450 mm

High energy section

cryostats

Figure 3: The most common cryostat modules, top view; layout used in the beam dynamics simulation for the three energy sections. The components length along the beam axis is given in the figure (NOT to scale).

Schematic of RFQ section and first QWR module


Example of multicharge beam transport in EURISOL SRL

Beam dynamics simulations in SRL*

Simulation of the accelerating sections using realistic EM fields of QWR’s

Aims:

1. Check multiple charge beam transport at high gradient

2. Check the effect of QWR steering in MCBT

3. Evaluate SRL performance in different operation modes• No stripper up to 60 MeV/u• 1 stripper 93 • 2 strippers 100

* performed using the code LANA (courtesy of D. Gorelov, MSU-NSCL)


132Sn

Win= 670 keV/u

Wout= 59.6 MeV/u

= -20 deg

Eacc= 7 MV/m

q Eff. (%)

Cav./prd.

I 25 100 4

II 25 100 4

III 25 100 8

Simulated using the LANA code

0

0.5

1

0 25 50 75 100 125

Position (m)

y e

nv

elo

pe

(c

m)

reference q maxall q maxreference q rms

0

0.5

1

0 25 50 75 100 125

Position (m)

x e

nv

elo

pe

(c

m)


0

0.2

0.4

0.6

0 25 50 75 100 125

Position (m)

Bu

nc

h le

ng

th

(n

s)


Linac Beam Envelopes with no strippers

N.B. simulation performed with an input transverse emittance 2 times larger than the nominal value


132Sn

Win= 16.3 MeV/u

Wout= 92.9 MeV/u

= -20 deg

q=45,46,47,48,49

Eacc= 7 MV/m

Eff.= 94%

INITIAL* FINALSimulated using the LANA code

* After stripping in a 2 mg/cm2 carbon foil

-6

-3

0

3

6

-0.50 -0.25 0.00 0.25 0.50

x (cm)

x' (

mra

d)

4546474849all

all charge states rms =0.059 ( cm mrad)

-6

-3

0

3

6

-0.50 -0.25 0.00 0.25 0.50

x (cm)

x' (

mra

d)

4546474849all


-200

-100

0

100

200

-0.20 -0.10 0.00 0.10 0.20

t (ns)

E (

ke

V/u

)

4546474849all

all charge states rms =0.56 ( keV/u ns)

-200

-100

0

100

200

-0.20 -0.10 0.00 0.10 0.20

t (ns)

E (

ke

V/u

)

4546474849all


-6

-3

0

3

6

-0.50 -0.25 0.00 0.25 0.50

y (cm)

y' (

mra

d)

4546474849all


-6

-3

0

3

6

-0.50 -0.25 0.00 0.25 0.50

y (cm)

y' (

mra

d)

4546474849all


-200

-100

0

100

200

-0.20 -0.10 0.00 0.10 0.20

t (ns)

E (

ke

V/u

)

4546474849all


BUNCHED

High Energy Section-160 HWR’s (1 stripper mode)

N.B. simulation performed with an input transverse emittance 2 times larger than the nominal value


Linac Beam Envelopes with 2 strippers

132Sn

Win= 670 keV/u

Wout= 100 MeV/u

= -20 deg

Eacc= 7 MV/m

q Eff. (%)

Cav./

prd.

I 25 100 4

II 36,37,38,39,40 78 4

III 46,47,48,49 95 8

0

0.2

0.4

0.6

0 25 50 75 100 125

Position (m)

Bu

nc

h le

ng

th

(n

s)


0

0.5

1

0 25 50 75 100 125

Position (m)

y e

nv

elo

pe

(c

m)


0

0.5

1

0 25 50 75 100 125

Position (m)

x e

nv

elo

pe

(c

m)


Simulated using the LANA code

N.B. simulation performed with an input transverse and longitudinal emittance 2 and 5 times larger than the nominal value, respectively


High Energy Section-160 HWR’s (2 stripper mode)

132Sn

Win= 21.6 MeV/u

Wout= 100 MeV/u

= -20 deg

q=46,47,48,49

Eacc= 7 MV/m

INITIAL* FINALSimulated using the LANA code

* After one more stripping in a 3 mg/cm2 carbon foil

-200

-100

0

100

200

-0.20 -0.10 0.00 0.10 0.20

t (ns)

E (

ke

V/u

)

46474849all


-6

-3

0

3

6

-0.50 -0.25 0.00 0.25 0.50

x (cm)

x' (m

rad

)

46474849all

all charge states rms =0.094 ( cm mrad)-6

-3

0

3

6

-0.50 -0.25 0.00 0.25 0.50

x (cm)

x' (

mra

d)

46474849all


-6

-3

0

3

6

-0.50 -0.25 0.00 0.25 0.50

y (cm)

y' (

mra

d)

46474849all


-6

-3

0

3

6

-0.50 -0.25 0.00 0.25 0.50

y (cm)

y' (m

rad

)

46474849all


-200

-100

0

100

200

-0.20 -0.10 0.00 0.10 0.20

t (ns)

E (

ke

V/u

)

46474849all

all charge states rms =3.13 ( keV/u ns) -200

-100

0

100

200

-0.20 -0.10 0.00 0.10 0.20

t (ns)

E (

ke

V/u

)

46474849all


BUNCHED


SRL simulations results for different modes of operation

1. No stripping (prob. most experiments)• E max 60 MeV/u • Transmission 100% Single charge beam• x y 0.5(0.25) mm mrad, z 0.7 keV/u ns (5 rms)

2. Stripper 2 only• E max 93 MeV/u • transmission 94% Multiple charge beam• x y 0.6(0.3) mm mrad, z 1.4 keV/u ns (5 rms)

3. Strippers 1 and 2• E max 100 MeV/u• Transmission 74% Multiple charge beam• x y 1(0.5) mm mrad, z 10(2) keV/u ns (5 rms)

N.B: 2 Strippers make the linac relatively insensitive to the charge breeder performance: with initial charge of 13+ instead of 25+, the final energy would be 95 MeV/u


0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250

cavity number

TT

F

0

20,000

40,000

60,000

80,000

100,000

E (

Me

V/u

)TTF

Energy (MeV/u)

0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250

cavity number

TT

F

0

25,000

50,000

75,000

100,000

125,000

150,000

E (

Me

V/u

)

TTF

Energy (MeV/u)

Virtually all RIB’s that allow charge breeding can be accelerated by SRL with similar results.

Examples:

• 33Ar(8+)E=127 MeV/u

• 210Fr(25+)E=100 MeV/u

33Ar(8+)

210Fr(25+)


Acceleration of different q/A beamswith 2-gap cavities

• Recent developments in SC linac technologymultiple charge beam transport beam stripping and high transmission

Superconducting cavites high gradients, wide acceptance

• High charge breeding is not strictly necessary – (but some charge breeding saves a lot of money)

• SC linacs can provide– RIB acceleration with finely tuneable energy and good beam quality

– High acceleration and transmission efficiency

– Large acceptance in q/A low mass selectivity, but also

low sensitivity to charge breeder performance

– flexibility in the modes of operation

– competitive construction and operation cost

SC linacs can be excellent RIB accelerators

Conclusions


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