High intensity superconducting linac studies for SPES ... · High intensity superconducting linac studies for ... •Beam dynamics of the high power p transport line to BNCT ... conducting

High intensity superconducting linac studies for SPES project at LNL

A. Pisent, M. Comunian, E. Fagotti , A. Palmieri, P.A. Posocco

INFN-Laboratori Nazionali di Legnaro

contents•Introduction: SPES project at LNL•Beam dynamics of the high power p transport line to BNCT (Boron Neutron Capture) facility•Beam dynamics in the superconducting linac

Laboratori Nazionali di Legnaro (Italy)

COULOMB-05: HIGH INTENSITY BEAM DYNAMICSSenigallia (Italy) September 2005

A. Pisent " High intensity linac for SPES " Senigallia Sep. 05Laboratori Nazionali di Legnaro (Italy)

ALPI

Exp. Halls

SPES(Study and Production of Exotic Species)

Driver linacBNCTTarget area

Legnaro National Laboratory aerial view

Production of n-reach isotopes by fission of 238U

238U(UCx)

Primary beam Fissionfragments

converter

nExperiments

1 mA *100 MeV = 100 kW1013 f/s300 W

108 132Sn/s

0.02 pnA, 16 MeV/uprotons

SPES 1 mA *100 MeV = 100 kWdeuterons 1014 f/sPhase 2 12C

12C, 13C or 9Be

Fissionfragments238U

(UCx)

ExperimentsProton beam

protons 0.1 mA *40 MeV = 4 kW


1013 f/s


TRIPS

Ladder section

8 cavities β=0.12

6 cavities β=0.17

TRASCO RFQ

to BNCT neutron source

20 MeV/q

0.08 MeV/A

100 MeV/q

56 m

β=0.31 HWR section

52 cavities 352 MHzβ=0.25 HWR section

16 cavities 352 MHz

43 m

36 MeV/q

SPES-1

SPES driver linac

• 5 mA protons at full energy• Superconducting CW linac from 5 MeV• High current (30 mA) normal

conducting injector used for BNCT• Design corresponding to the first part

of EURISOL driver• Possible upgrade to deuterons

5 MeV/q


Ladder section

8 cavities β=0.12

6 cavities β=0.17

42 MeV/q

100 MeV/q

72 m

β=0.31 HWR section

52 cavities 352 MHzβ=0.25 HWR section

16 cavities 352 MHz

β=0.09 HWR section

14 cavities 176 MHz

CW 176 MHz

RFQ

6.5 MeV/A

20 keV/A

1.7 MeV/ATRASCO RFQ

to neutron source

• 5 mA protons at full energy• Superconducting CW linac from 5 MeV• High current (30 mA) normal

conducting injector used for BNCT• Design corresponding to the first part

of EURISOL driver• Possible upgrade to deuterons (5 mA)

SPES driver linac

SPES-1 approved at LNL:1. Realization of the 5 MeV 30 mA p injector (based on TRASCO technology)2. Development and construction of the thermal neutron facility (109 cm-2 s-1 using 30 mA 5 MeV) for BNCT

(Boron Neutron Capture Therapy)3. Development and construction of the superconducting p linac, for a maximum current of 10 mA, up to 20

MeV4. Further development of the R&D program on RIB production targets Since Jan Since Jan ’’04 SPES04 SPES--1 is a funded INFN Special Project 1 is a funded INFN Special Project (18.6M(18.6M€€, five years, five years))

5 MeV 30 mA

RFQ

MEBT

Superconducting main linacTRIPS

20 MeV 10 mA


BNCT n-source

150kWBe target


The SPES-BNCT project

• INFN-LNL, Legnaro (Padua) • ENEA, Casaccia, Rome, • ENEA, Bologna• Nuclear Engineering Dept, Milan Polytechnic• The D. V. Efremov Institute, S. Petersburg • Biology Dept, Padua University•Clinic surgery, Padua University•Regional Center for skin melanoma Padua University and A.O.• Molteni Pharmaceuticals, Florence• Rad. & Oncology Dept, IRCSS Padua Univ. Hospital

A collaborative R&D effort in different research areas among the following institutions

A multidisciplinary group (medical doctors, biologists, physicists, nuclear engineers…) is working on advanced radiotherapy methods.

First goal is the use of thermal neutrons for the application of BNCT to the treatment of skin melanoma

The SPES-BNCT irradiation facility conceptthermal neutrons for skin melanoma


beam particle:beam particle: protonprotonbeam energy: beam energy: 5 MeV5 MeVbeam current: beam current: 30 mA30 mAbbeam power: eam power: 150 kW150 kW

accelerator specifications

φn th (≤ 0.4 eV) ≥ 109 [cm-2 s-1]φ n th / φ n total ≥ 0.9Dn epi+fast / φn th ≤ 2· 10-13[Gy cm-2]Dγ / φn th ≤ 2· 10-13[Gy cm-2]

neutron beam requirements

•

•

150 kW converter

4.5 m to the target1.8 m1.4 m0.8 m

1.7 m

6 cm

6 cmRFQ

Schielding wall

BNCT transport line elements

700 W/cm2

Be p/n converter


BNCT line simulations(PARMILA, 100 000 particles)



54 cm

In the meter before the collimator0.3 kW

On the collimator8 kW

Total5.6% of the 150 kW beam

Beam losses

10.9 cm

BNCT converter design

• Beam distribution is parabolic in good approximation

• The power distribution on the converter surface is below 700 W/cm2

• This line design is tolerant to misalignments (0.5 mm) of the quads


Power distribution on

converter surface

The superconducting linac

• Advantages of a superconducting CW linac– lower operating cost

• DTL and ISCL options seem to have similar costs, but with an importantdifference in AC power (8.8 MW compared with less than 1.5 MW) and itmakes a big difference in the operating cost – of the order of 2 M€per year

– lower capital cost respect to a pulsed superconducting linac• Easier target management of the incident power, lower RF installed power,

simpler field stabilization

– Heavy ion capability: • changing the independent phases it is possible to accelerate (with full

gradient) ions with different q/A


Linac simulations

• The beam power, in various configurations, is of the order of 100 kW• To investigate 1 W/m effects at least 105 macroparticles are needed• Los Alamos codes Trace 3D, PARMILA and PARMELA codes are

used for beam dynamics simulations.• Many tests with 106 particles have been done (on PC cluster) with

Halodyn, developed at Uni. Bologna.• The simulations to specify construction tolerances are being done with

PARMELA since it allows– realistic cavity field– Easy systematic error studies


Beam dynamics issues: high quality beams

• In a ISCL the focusing structure is the key choice, capable of allowing the efficient use of high performance cavities (Typical values for ∆W, energy gain par cavity, go from the 0.6 MeV of re-entrant cavities, to 1-1.5 MeV for multi gap structures).

• Low order resonances and envelope instability are avoided if

• This limits the period length L, n cavity per period and ∆W , since (in non rel approx):

Therefore high performance cavities need a compact lattice!

200 πσσ ≤≤ TL 3323320)sin(2)sin(2

γβφπ

λλγβφπσ

mcWLn

mceEL ss

L−∆

≈−

=

5.1)sin(4≈

−<

∆

s

LW

Wnφ

πβλ

with


Beam dynamics non ideal: transitions

SPES 5-20 MeV section (12 m)Superconducting quadrupole (MSU-LNL)

0.69 m=8βλ


Few fundamental rules are followed

• Zero current phase advances is less than 90 degrees per period in the entire structure in order to avoid instabilities for every current regime.

• Transverse phase advances is everywhere greater than longitudinal ones except in the matching section where match has precedence.

• Structure is as compact as possible to increase real estate gradient.

• The bore to rms ratio is the greatest as possible to guarantee full transmission. 0.1

0.3

0.5

0.7

0.9

1.1

1.3

1.5

0 1 2 3 4 5 6 7 8 9 10 11Longitudinal Length (m)

Effe

ctiv

e G

ap V

olta

ge (M

V)

0

10

20

30

40

50

60

70

80

90

100

110

Sigm

a/L

(deg

ree/

m)

Effettive gap voltageZ-Phase advance per meter

1.5

2

2.5

3

3.5

4

4.5

0 1 2 3 4 5 6 7 8 9 10 11Longitudinal Length (m)

Qua

drup

ole

Stre

ngth

(T)

0

10

20

30

40

50

60

70

80

90

100

110

Sigm

a/L

(deg

ree/

m)

F-QUAD strengthD-QUAD strengthX-Phase advance per meterY-Phase advance per meter


Beam dynamics non ideal: the MEBT

Dipole

Buncher

Quadrupole

4.5m to BNCT target

RFQ

Linac


The MEBT

Linac RFQ

BNCT Figure 3: 10 mA in and output phase space distributions, x-x’ plane in blue and y-y’ in red.



Beam dynamics in

TRASCO RFQ (10 mA)Phase space output

2 Peaks in the longitudinal plane

Beam dynamics non ideal: the RFQ distr.


5 mA

30 mA 50 mA

10 mA

95.0

95.5

96.0

96.5

97.0

97.5

98.0

98.5

99.0

99.5

100.0

0 5 10 15 20 25 30 35 40 45 50Current (mA)

Tran

smis

sion

(%)

0.15

0.17

0.19

0.21

0.23

0.25

0.27

0.29

0.31

0.33

0.35

El.rm

s-Et

.n.rm

s

Trans. (%)El.rms (deg-MeV)Ex.n.rms (mm-mrad)Ey.n.rms (mm-mrad)

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

0 5 10 15 20 25 30 35 40 45 50Current (mA)

Hal

o x-

y-z

Halo-xHalo-yHalo-z

Beam Parameters vs. input currentBeam Parameters vs. input current

Halo Limit Halo Limit ~ 1 for ~ 1 for gaussiangaussian beamsbeams

Transversal phaseTransversal phase--space may be space may be considered halo freeconsidered halo free for all currentsfor all currents


Longitudinal phaseLongitudinal phase--space presents a halo space presents a halo structure increasing with currentstructure increasing with current

E. Fagotti et al TUP19

II22 = <q= <q22>< p>< p22> > -- <<qpqp>>22

II44 = <q= <q44>< p>< p44> + 3 <q> + 3 <q22 pp22>>22 ––4 <q p4 <q p33><q><q33 p>p>H =[(3 I44) / 2 I22] – 2H =[(3 I ) 1/21/2 / 2 I ] – 2


0

50

100

150

200

250

300

350

400

450

500

550

-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1Energy spread (MeV)

Parti

cles

Num

ber

0

50

100

150

200

250

300

350

400

450

500

550

-40 -30 -20 -10 0 10 20 30 40Phase spread (deg)

Parti

cles

Num

ber

0

50

100

150

200

250

300

350

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5Spa tia l spre a d (m m )

Parti

cles

Num

ber

x (mm)y (mm)

0

50

100

150

200

250

300

350

-20 -15 -10 -5 0 5 10 15 20Divergence spread (mrad)

Par

ticle

s Nu

mbe

r

x' (mrad)y' (mrad)

XX YY ZZ

hh 0.350.35 0.360.36 0.350.35

HH 0.390.39 0.350.35 1.061.06

Halo parameters for a 10 Halo parameters for a 10 mAmA beambeam

HaloHalo

Beam distribution at RFQ out for 10 Beam distribution at RFQ out for 10 mAmA input currentinput current


EXTRACTION AND NEUTRALIZATIONMultispecies Parmela simulationsH+,H++,e-

Negative electrode suppresses the electron current flowing towards extractor electrode at 80 kV.

23 ns

Head effect in beam generation. Cause to this effect, only central part of the beam enters the calculation.

http://http://trasco.lnl.infn.ittrasco.lnl.infn.it


Beam distribution

5 MeV 20 MeV

Ngood=99’621/100’000


Beam dynamics with construction errors (20 MeV)

0123456789

101112131415161718192021

0 1 2 3 4 5 6 7 8 9 10 11Longitudinal Distance (m)

Max

imum

Dis

plac

emen

t (m

m)

xmax (mm)ymax (mm)Bore (mm)

-5-4-3-2-10123456789

1011121314151617181920

0 1 2 3 4 5 6 7 8 9 10 11Longitudinal Distance (m)

Emitt

ance

incr

ease

(nor

m.rm

s) %

Exrms.n.Eyrms.n.Ezrms.n.

Maximum rms emittances increase versus longitudinal length for 200 independent with about 100 000 macroparticles(2W/particle at 20 MeV).

Input conditions (actual RFQ distribution)

Current 10 mA

Energy 5 MeV

x 0.208 mm-mrad

y 0.204 mm-mrad

z 0.240 deg-MeV

Emit. norm. rms

errors

3.5 mradQuadrupole roll

3.5 mradQuadrupole tilt

0.2 mmQuadrupole transverse displacements

+10%

The 20 MeV 10 mA linac (alternatives)

RFQ MEBT

Transition with ext.doublet

22 m

1)

2)

Straight linac with dipole for BNCT line(38 reentrant or 13 ladder)• Full transmission (100K) • <5% emittance increase


Few hardware pictures to conclude

Laboratori Nazionali di Legnaro (Italy)

The LNL-BNCT projectneutron converter prototype assembling and first full beam power test

1. Be tile brazed cooling pipes


3. Final target assembling

4. Visual inspections after e-beam full power test

700 Wcm-2 pick power density60 kW total power

2. collector plates welding & EDM manufacturing process

TRIPS (TRASCO source developed at LNS)

high current RF off resonance p-source

40 mA protons

•Nominal current (40 mA) and lowemittance (approx 0.1 mm mrad rms) have been measured

Water cooledPlasma chamber

solenoids

Extraction electrodes(80 kV)

r

r’


TRIPS source will be moved to Legnaro next October

6 m

11 m



5 MeV30 mA CW352 MHz7.2 meters long800 kW RF power (1 Klystron)8 Couplers4500 Liter/min water cooling33 MV/m Surface field

RFQRFQ(Radio Frequency (Radio Frequency QuadrupoleQuadrupole))

beam

Construction Procedure (1) CINEL, Vigonza (PD)

2Vacuum grids machining

1Raw machining & deep-hole drilling of the cooling channels


3Brazing cave machining

4Electrode modulation machining

5Electrode assembly pre 1st

braze6 assembly after 1st braze (before machining)


Second brazing verticalFirst brazing horizontal

8 assembly after 2nd braze

TRASCO RFQ construction– The first two modules are built – RFQs: the last four modules of the RFQ are under construction– The contract foresees two years of construction.– Some subsystems specific to the BNCT application are being developed

5 MeV30 mA CW352 MHz7.2 meters long800 kW RF power (1 Klystron)8 Couplers4500 Liter/min water cooling33 MV/m Surface field



Superconducting Reentrant cavity

•Developed for high intensity beams •352 MHz, single gap, aperture 30 mm•Wide velocity acceptance:5÷100 A MeV

Successfully tested at 4.2K:•Free from high field multipacting•Ea= 7.5 MV/m @7W

1.E+07

1.E+08

1.E+09

1.E+10

0 1 2 3 4 5 6 7 8 9 10Ea, MV/m

Qo

7W1. after CP2. after vacuum failure3. after HPR

Alberto Facco Capri 2003


LNL 352 MHz, β=0.3 HWR

•Side tuner insensitive to He pressure changes

•Real estate length: 286 mm; active length: 224 mm, βλ=256 mm )

1.00E+07

1.00E+08

1.00E+09

1.00E+10

0 2 4 6 8 10

Q

1st test, no HPR, overcoupledQ 10 W

Ea*L*T= 1.2 MV @ 10W (preliminary)

12.85.1 7.7 10.2Ea (MV/m) Ea (MV/m) iris-to-iris 2.6

HeF D

20-100 MeVcryomodule

Conclusions40 MeV

20 MeV

5 MeV

BNCT

• The approved project for the development of LNL, SPES-1, is in the following status

– The RFQ (5 MeV 30 mA) is under construction.– The neutron BNCT source is defined, and a

prototype of the high power converter has been tested with e-beam of nominal power density.

– For the superconducting linac• the nominal design has been tested with

simulations end to end.• Cavity prototypes have been successfully built


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High intensity superconducting linac studies for SPES ... · High intensity superconducting linac studies for ... •Beam dynamics of the high power p transport line to BNCT ... conducting