The Single Stage Cyclotron Driver (S2CDTM) for the CYCLADS Project

M.Conjat and P. Mandrillon

AIMA-DEVELOPPEMENT

Brussels – ThEC 2018

A brief history of Cyclotron Drivers for ADS

1- The Collaboration with the Energy Amplifier Group of Pr. Rubbia

Carlo Rubbia, Nobel 1984 CERN Honorary DG

The September 1995 historical CERN Report

Design of a 1 GeV multi-stages driver

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2- TRADE, single-stage driver for a TRIGA reactor (ENEA)

Stripping Extraction of 240 MeV-H2+ providing a 120 MeV-2*3 mA Proton Beam

AIMA 115N

Core Reactor

Cyclotron (section)

Beam Pipe

Shielded Beam Pipe Tunnel

Control Room Window

Stripping extraction of H2+ => 2H+ => Intensity doubling !

A brief history of Cyclotron Drivers for ADS

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The requirements for an industrial ADS Demo

- Beam Energy: 600 - 800 MeV protons to produce neutrons via spallation.

- Beam Power: Pbeam 5-10 MWatt.

- Optimized Power efficiency: h=Pbeam/Pgrid

- Minimized beam losses: internal losses < 200 Watt.

- Reliability: reduced down time compared to alternative designs; fewer beam trips

- Beam stability: choice of Ion source with multiple injection systems (to reduce beam trips)

- Low investment and running costs

- Facilitated maintenance

Low number of components

Easy access to components (RF cavities, RF amplifiers, injection and extraction devices, ion sources…)

>> Single stage cyclotron is an attractive solution

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How to keep the simplicity of a Single Stage Cyclotron Driver to cope with the challenge of the industrial ADS requirements?

Cyclotron Drivers: 1995 > 2013

The future of ADS drivers

The concept of S2CDTM

The CYCLADS Consortium

CERN

AIMA Developpement (AD)

ASG

ENEA

HNE

iThEC

N-21

PSI

INFN

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The issues of a multi-stage system: the example of PSI

The PSI 2 stages geometry : a 72 MeV Injector and the 590 MeV Booster ring. various injection and extraction channels

PSI has reached the Highest extracted beam intensity performance!

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The issue of the extraction

PSI single turn extraction with septum > High yield, low activation

Lower number of turns to get high intensity

The Werner Joho Law

The large mono-gap cavity

PSI: Single turn extraction

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The main causes of beam trips in the PSI multi-stages cyclotron

From M.Seidel PSI in 2009

1+2+3+4 = 64% 26000 beam trips per year in 1999

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2

3 4

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The solution: The 600MeV 10mA proton Single Stage Cyclotron Driver S2CDTM

• 20-30 % power efficiency

• Multiple injection systems for increased reliability and

reduced beam trips

• Small footprint and weight for investment cost reduction

• Easy maintenance thanks to fewer parts, swappable

cavities

Reverse valley field concept for compacity and ease of extraction

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Single stage Cyclotrons Magnetic Fields

B on the valley axis

TRIUMF-520 MeV H- S2CD-600 MeV H+ with reverse B field

10m 15m

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Challenges of Single Stage design

1- Large superconducting coils (ASG partner in the CYCLADS Proposal):

- Mechanical design of a complex shape with bends

- Possibility to use MgB2 for a cryo-free cooling system ?

=> Tests and prototypes are needed

2- High power double gap RF cavity design to handle 1.4(H+) - 1.6(H2+) Mwatt (CERN collaboration) :

- 2 RF Windows + 1 Amplifier/window

- relation between cavity & extraction system

- a full scale model of a prototype cavity is needed

3- Multi Injection :

- an experimental program is planned by AD to validate this concept

4- High intensity beam dynamics

- Non linear beam dynamics models for halo characterization are in development in AD

- cross check tests foreseen with PSI (partner in the CYCLADS Proposal)

5- Costs: Low number of elements – small footprint

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400 m

Comparison of 600 MeV designs - MYRRHA – S2CD

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Triple injection central region

40° of phase acceptance

major advantage: low B-field in the central region > 3 axial injections – 3 separated beams

An injector cyclotron is not needed anymore !

If 2 ions sources are used simultaneously: 2*3 mA H2+ > 12 mA Proton after stripping

Easy way to adjust intensity

Simulations with AGORA-SCE

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Ion source experimental programme

Test magnet (40 cm)

Multicusp Ion source – 40 mA /cm² 14

Stripping Extraction (H2+)

1200 MeV H2+ acceleration

H2+ acceleration

Proton extraction -600 MeV

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• Single stage accelerator

– Compact system - low construction budget and Low operational cost

– Less components than traditional solutions high reliability

– No transport / no matching issues between stages

• 3 sources + axial injection lines : 2 sources On + 1 source in Stand-by

– redundancy

– Reliability

– Intensity Flexibility

• Simplified Extraction system : No Septum required

– Increasing reliability

– less activation => easier maintenance

• Time Line

- 5 years

• Costs Estimates

- 130/140 M€ including beam lines and ancillary equipments

The single stage cyclotron is the industrial solution for an ADS

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The S2CD is an efficient Driver: Yield 20%

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6 MWatt

30 Mwatt

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Thank you for

your attention

The reverse valley bends Cyclotron

isochronism:

> positive radial gradient of <B>

> strong vertical defocusing:

Dnz2 = -(g2-1) = - (d<B>/dr)r/<B>

> edge and spiral focusing

nz2 =-(g2-1)+F2(1+2 tan2z)

F2= Field Flutter = (<B2>-<B>2)/<B>2

z= spiral angle of the sector

2-A separated sector with reverse valley B:

Stronger Flutter No Spiral needed

Proton Extraction is simple by a bump, i.e. « Septum free extraction »

The cavities Classical half-wave resonator with a delta shaped resonant line