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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….
APS Meeting, March 31st 2012 2
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
APS Meeting, March 31st 2012 3
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.
APS Meeting, March 31st 2012 4
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
APS Meeting, March 31st 2012 7
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.
APS Meeting, March 31st 2012 8
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
APS Meeting, March 31st 2012 10
Compact Cyclotron, 230
MeV, proton therapy
Superconducting
Cyclotron
Ring
Cyclotron
590 MeV,
>1.4 MWatt
APS Meeting, March 31st 2012 11
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!
APS Meeting, March 31st 2012 12
test run: stable operation at 2.3mA
courtesy of M. Seidel PSI
APS Meeting, March 31st 2012 13
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
APS Meeting, March 31st 2012 16
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
APS Meeting, March 31st 2012 17
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
APS Meeting, March 31st 2012 19
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
APS Meeting, March 31st 2012 20
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
APS Meeting, March 31st 2012 21
Bmax on the
coil 6.18T
Current density 34A/mm2
View of preliminary sector for
DAEDALUS Superconducting
Ring Cyclotron
APS Meeting, March 31st 2012 22
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)
APS Meeting, March 31st 2012 23
The radial size of the
beam depend mainly
by the energy
gain per turn
DE/E%
APS Meeting, March 31st 2012 24
Effect due crossing
Walkinshaw resonance
With courtesy of J.J. Yang & A. Adelman
APS Meeting, March 31st 2012 25
Steering
/focusing
Magnetic
Channel
Extraction trajectories
energy spread< ±0.6%
Stripper foils
2° proton
beam
2°
Stripper
APS Meeting, March 31st 2012 26
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
APS Meeting, March 31st 2012 27
The cyclotron complex , at the
far site, is designed to delyver
an average power of 3.2 MW
Maximum power 16 MW
APS Meeting, March 31st 2012 28
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
APS Meeting, March 31st 2012 29
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
APS Meeting, March 31st 2012 30
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]
APS Meeting, March 31st 2012 31
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
APS Meeting, March 31st 2012 32
BEAM LOSSES: Main source is the interaction of the
beam particles with the residual gases
H2+, I=8 mA, 12.8 MW
APS Meeting, March 31st 2012 33
BEAM LOSSES: a 10% of nitrogen contaminant is
acceptable if the working vacuum stay at 1 10-8 mbar
APS Meeting, March 31st 2012 34
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
APS Meeting, March 31st 2012 35
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!
APS Meeting, March 31st 2012 36
• 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
APS Meeting, March 31st 2012 37
Thanks for
your
attention!
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