High Power Cyclotrons for Accelerator Driven Systemcompact injector cyclotron. We could use two...

APS Meeting, March 31st 2012 1

High Power Cyclotrons for

Accelerator Driven System

Luciano Calabretta, Mario Maggiore, Leandro Piazza, Danilo Rifuggiato

LNS & LNL- Istituto Nazionale di Fisica Nucleare, Italy

Alessandra Calanna, Daniela Campo, MIT, Boston,USA

J. Alonso, W. Barletta, J. Conrad, M. Shaevitz, DAEdALUS collaboration

A. Adelman, J.Yang, PSI, Villigen, CH, et Al….


ADS for Thorium Reactor

Advantages: Fast neutron flux destroy long lived actinides

ADS core can use spent

nuclear fuel as starting turn a liability into an asset

inventory

ADS fast neutronics is not deep burnup of fuel

poisoned by fission product

The molten salt core is total loss of power and

a walkway safe coolant cannot melt the core

*Thorium Energy Conference 2011

http://www.itheo.org

ADS allows the use of non The thorium abundancy is

fissile fuels (e.g. Th) without estimated to be at least

U or Pu into fresh fuel 10 times the Uranium


Do the advances that have been made in Accelerator Technology in the

last 10-15 years change the practicality of ADS for processing waste

and generating electricity?

Is the technology to the point where a demonstration program is

warranted?

Once Again the USA Physics Research can drive the development

and test of accelerators with specifications very near to

accelerators for ADS.

DAEdALUS experiment offer this opportunity!

DAEALUS, is a Decay-At-rest Experiment for CP studies At the Laboratory for

Underground Science, proposed by J. Conrad (MIT) & M. Shaevitz (Columbia

Univ.). The design utilizes high-power proton beam to produce neutrino beams

with energy up to 52 MeV from pion and muon decay-at-rest.

The experiment searches nm ne for at short baselines corresponding to the

atmospheric Dm2 region. The ne will be detected in the 300 kton fiducial volume

Gd-doped water Cerenkov neutrino detector proposed for the Deep Underground

Science and Engineering Laboratory (DUSEL), via inverse beta decay.


Lay-out of DAEdALUS experiment. Three proton sources are used to send neutrino beams at a 300 kton water Cerenkov

detector placed at 1.5 km underground

Cost < 150 M$ each ?

5

Neutrino spectrum from Decay-at-Rest of stopped π+

Spectrum is devoid of ne

APS Meeting, March 31st 2012

6 APS Meeting, March 31st 2012


2

ms

2

ms

2

ms

2

ms

2

ms

2

ms

2

ms

2

ms

2

ms

8 ms

8 ms 8 ms

8 ms

8 ms 8 ms

To identify the source that

produced the detected

neutrino, the accelerators are

driven with a 20% duty cycle:

<2 MW> peak power 10 MW

or higher

- Superconducting linacs provide the most conservative technology option but

they are expensive

- Space and cost constraints suggest that high-power cyclotrons could be a less

expensive option.


DAEdALUS needs 1 3 MW proton beam @ 800 MeV

The beam time structure being 2 msec beam on, 8 msec beam off

duty cycle= 20% peak power 515 MW Peak current 618 mA

We propose a Multi-Megawatt Cyclotron Ring (MMC), to accelerates H2+ for two

main reasons:

-Vantages of stripper extraction vs. the Electrostatic Deflectors extraction

-Space charge effects reduced by a factor vs. proton beam

2

Comparison of perveance values for protons and H2+ beams :

332

m

qIK

o

Ep=30 keV, EH2=30 keV

p= 1.414H2

Ep=30 keV, EH2=70 keV

p= 0.926H2

Proton 10 mA Kp =1.245 10-3 Proton 2 mA Kp= 0.249 10-3

H2+ 5 mA KH2+= 0.881 10-3 H2

+ 5 mA KH2+ = 0.247 10-3

KH2/Kp=0.707 KH2/Kp=0.992


Compact Cyclotron, 230

MeV, proton therapy

Superconducting

Cyclotron

Ring

Cyclotron

590 MeV,

>1.4 MWatt


Summary/Outlook (courtesy M. Seidel PSI, IPAC2010 )

• the PSI accelerator delivers 1.3MW beam power; loss: 10-4; average reliability is 90%; 25-50 trips per day; grid-to-beam power conversion efficiency is 32% considering RF systems only; 15% including everything

• upgrade to 1.8MW is under work; new resonators Inj II; new 10’th harmonic buncher; completion planned for 2013

• cyclotron concept presents an effective option to generate high power beams, for example for ADS applications [e.g. 1GeV/10MW]

2011 1.42 MW!

First Beam

1974!


test run: stable operation at 2.3mA

courtesy of M. Seidel PSI


Main Downtime Causes - electrostatic elements - controls problems - cooling/site power - RF not prominent!

Performance 2009 Reliability: 89.5% Beam trips: 25..50 d-1

13

PSI-HIPA operational data 2009, courtesy of M. Seidel PSI

APS Meeting, March 31st 2012 14 S. Henderson, Thorium

Energy Conference 2011

Range of Accelerators Parameters for ADS

PSI Ring cyclotron: beam trips (1 sec<) <18000/year

PSI Ring cyclotron: beam trips (5 min<) < 1800/year

PSI Ring cyclotron: Availability > 89%

ADS System Level Requirements

APS Meeting, March 31st 2012 15 S. Henderson, Thorium

Energy Conference 2011

• High proton beam power with low beam

loss to allow hands-on maintenance of the

accelerator

• High wall-plug to beam power efficiency

High System Availability is required for a commercial system

• Beam Trip Frequency: thermal

stress and fatigue in reactor

structural elements and fuel

assembly sets stringent

requirements on accelerator

reliability

12 MW K 0.97

K0.97


The base cyclotron module

for DAEDALUS is

designed to deliver proton

beam 10 mA @ 800 MeV

duty cycle 20%, average

power <1.6 MW>

Stripper extraction

< 1 mA> H2+ 60 MeV/n

<120 kW>/600 kW peak

Stripper foil

Extracted beam

< 1 mA> H2+

800 MeV/n

20%<1.6 MW>

8 MW peak

Space Charge effects,

Electrostatic Deflectors

Superconducting Coils,

Losses due to residual gas


60 KV -3.5 KV

Ground

180 200 220 240 260-10

0

10

20

30

40

Tw

iss P

ara

mete

rs

Solenoid Current [A]

180 200 220 240 2600

0.05

0.1

0.15

0.2

0.25

r [.m

m.m

rad]

[mm/mrad]

400 600 800 1000 1200 14000

0.2

0.4

0.6

0.8

1

Pro

ton F

raction

Power [W]

400 600 800 1000 1200 14000

10

20

30

40

50E

xtr

acte

d c

urr

ent

[mA

]

H1

+

H2

+

Versatile Ion Source (VIS)

Developed at LNS-Catania

by Gammino, Ciavola, Celona et Al.

VIS could deliver

more than 30 mA of

H2+ adjusting some

parameters like:

RF Power, Vacuum

Pressure, Position

of the permanent

magnets, increasing

the extraction hole

Good

emittance

18

The beam current limit is posed by the source and by the

compact injector cyclotron. We could use two injector

cyclotrons and one Ring Cyclotron to increase the average

beam power up to 3.2 MW Maximum Power 16 MW!

Interesting solution

proposed by H. Owen

APS Meeting, March 31st 2012

<1mA> H2+

delivered by each

injector cyclotron

<2mA> H2+ <4 mA> of proton <3.2 MW>

beam delivered by each Ring Cyclotron


To inject an average beam current

higher than 2 mA of H2+, we could

use a separate sectors cyclotron as

injector. In this case the beam is

injected with energy of 1-2 MeV/n and

the pre-injector could be an RFQ.

<I> > 2 mA H2+

average current

Maximum Current > 10 mA H2+

Preinjection

by RFQ

RFQ should be able to accelerate

more than 50% of the 20 mA

beam current delivered by the

H2+ Ion source Proton Maximum

current 20 mA

Stripper foil

Last

accelerated

orbit


DAEdALUS Superconducting Ring Cyclotron Parameters

Einj 60 MeV/n Emax 800 MeV/n

<Rinj> 2.0 m Rext 4.9 m

<B> at Rinj 1.06 T <B> at Rext 1.88 T

Pole Gap 80 mm Bmax < 6 T

Hill width 20° Sector height < 6 m

Outer radius 7.5 m Sector weight < 500 Tons

Flutter 1.4 1.97 Sectors N. 8

4 Cavities type Pill Box 2 Cavities type Double gap

RF 49.2 MHz Harmonic 6th

V-peak 1000 kV DE/turn 2.64.5 MeV

DR at Rinj > 20 mm DR at Rext 2.8 mm


Bmax on the

coil 6.18T

Current density 34A/mm2

View of preliminary sector for

DAEDALUS Superconducting

Ring Cyclotron


Vertical beam size along the acceleration in the radial range from 4 to 4.9 m,

snapshot at 0° azimuth. The left figure has no charge space effects, 0 mA. The

right figure is evaluated with a 5 mA beam H2+ current

Simulation made by J. Yang and A. Adelman, using OPAL code

Space charge

effects have

negligible

effects during

acceleration in

the ring

cyclotron

Histogram of 5 mA H2+ beam at the stripper foil position,

simulation include space charge effects (OPAL code)


The radial size of the

beam depend mainly

by the energy

gain per turn

DE/E%


Effect due crossing

Walkinshaw resonance

With courtesy of J.J. Yang & A. Adelman


Steering

/focusing

Magnetic

Channel

Extraction trajectories

energy spread< ±0.6%

Stripper foils

2° proton

beam

2°

Stripper


The radial (blue lines) and axial (red line) envelope for the proton beam with

zero energy spread vs. distance from the stripper position along the

extraction trajectory are shown. The green show the radial beam envelope for

the cases with energy spread of 1.%.

Steerer/focusing


The cyclotron complex , at the

far site, is designed to delyver

an average power of 3.2 MW

Maximum power 16 MW


2.5 MW

2.5 MW

Layout of a

production

plant

5 cyclotrons

drive 4 ADS

Each ADS is

driven by 3

accelerators.

Beam stability

increases

and

decreases the

number of

beam trips

5 MW 5 MW

5 MW 5 MW

5 MW 5 MW

5 MW 5 MW

5 MW 5 MW 2.5 MW

2.5 MW

12.5

MW

12.5

MW 12.5

MW

12.5

MW


In case of

failure or beam

trips in a

cyclotron, it is

possible to

increase the

beam current

delivered by

each cyclotron

to maintain the

beam power at

12.5 MW!

6.25 MW 6.25 MW

6.25 MW 6.25 MW

6.25 MW 6.25 MW

6.25 MW 6.25 MW

12.5

MW

12.5

MW 12.5

MW

12.5

MW

Cyclotron OFF


Bunch separation 20 nsec, Bunch length < 1 nsec

The voltage to chop the beam is some kV and is applied

using fast switch with rise time <100 nsec

Beam intensity modulation is achieved by chopping the beam

injected into the injector cyclotron

Expected current control feedback time < 100 msec

Injector

10 msec

Beam on

Injector

2.5 msec

Beam off SRC Transit time 50 msec

t [msc]


Cyclotron for

therapy allow for a

Fast beam intensity

Control

the beam current

of each injection

cyclotron can be

fast modulated to

control the beam

power


BEAM LOSSES: Main source is the interaction of the

beam particles with the residual gases

H2+, I=8 mA, 12.8 MW


BEAM LOSSES: a 10% of nitrogen contaminant is

acceptable if the working vacuum stay at 1 10-8 mbar


Stripper foil: 5 MW beam @ 800 MeV Xing a stripper foil 1

mg/cm2 thick release 45 W due to nuclear interaction!

The electrons removed by the strippers have a full power of

5 MW*Me/MH2=5/(2*1826)=1370 W !

Electrons are the main source of stripper damage

But, electrons can be stopped before strike the stripper

Stripper Thickness can be also

thinner, because:

H- =(p+e+e) p, e, e is a two steps

process (p+e+e) H + e p, e, e

H2+ =(p+p+e)p, p, e is a single step

process, lower probability for

H2+H + p

The neutral H can be removed by an

additional stripper foil, 10 cm later

Stripper foil

emerging protons

H2+ beam

electrons catcher

If B=0.4 T

Re=4.5 mm


5 MW Proton beam on stripper foil of 1 mg/cm2, release 45W, the

beam spot size should be 16 mm2 3 W/mm2 , this energy

density can be decreased using thinner stripper foils

Stripper

Stripper position is chosen to

achieve:

- Good extraction trajectory

- Good beam envelope along

extraction

- No interference with injection

devices

- Stripper is placed in the

boundary of the hill where

magnetic field is <0.4 T

The SNS facility works with an average power of 1 MW and

peak power of 17 MW, and the mean life of the CVD stripper

foil have lifetime of several months!


• The cyclotrons are today a reliable solution, mainly if the

stripper extraction is used

• The number of beam trips is already acceptable and will be

improuved by solution without Electrostatic Deflectors and

using three Cyclotrons to feed one ADS

• The amount of beam losses can be maintained below the

acceptable value of 200 W per accelerator vault

• And last but not the least the plug wall conversion

efficiency will stay at 4655%

CONCLUSIONS


Thanks for

your

attention!

High Power Cyclotrons for Accelerator Driven Systemcompact injector cyclotron. We could use two...

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