HiPER laser: from capsule design to the laser reference design
B. Le Garreca, J. Collierb, C. Edwardsb, K. Ertelb, S. Atzenic, D. Batanid, L. Gizzie, X. Ribeyref,
G.Schurtzf, A. Schiavi, M. Perladog, B. Rush
a
CEA-CESTA, 15 av. Des Sablieres, 33114, Le Barp, France
b
STFC Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, United-Kingdom
c
Dip. SBAI, Università di Roma ‘La Sapienza’ and CNISM Italy
d
Dip. di Fisica, Univ. Milano-Bicocca and CNISM, Italy
e
ILIL at INO, CNR, Pisa, Italy
f
CELIA, Université Bordeaux 1, 33405 Talence, France
g
Instituto de Fusión Nuclear, Madrid, Spain
h
Institute of Physics / PALS Centre, Prague, Czech Republic
ABSTRACT
HiPER (High Power laser Energy Research) is the first European plan for international cooperation in
developing inertial fusion energy. ICF activities are ongoing in a number of nations and the first ignition
experiments are underway at the National Ignition Facility (NIF) in the USA. Although HiPER is still in the
preparatory phase, it is appropriate for Europe to commence planning for future inertial fusion activities that
leverage the demonstration of ignition. In this paper we shall detail some of the key points of the laser design
and the way this design is connected to the capsule requirements.
Keywords: to be completed
INTRODUCTION
The HiPER project intends to demonstrate the feasibility of inertial fusion schemes suitable to energy production (IFE:
inertial fusion energy). As presently envisaged, an IFE reactor will consist of a driver, delivering pulses of a few MJ of
energy at rate of 5–20 Hz, inducing compression, ignition and burn of targets containing a few mg of deuterium-tritium
mixture. Economic operation (see sec. 3) requires that the energy gain G of the target, i.e. the ratio of the released fusion
energy to the driver pulse energy satisfies G > 10/, where  is the efficiency of the driver. For 
G > 100
is needed. Such a high gain can potentially be achieved by inertial fusion schemes using direct laser compression and
advanced ignition schemes, such as fast ignition [1] and shock ignition [2]. Since most relevant issues can be studied by
using scaled down targets and lasers, the preparatory-phase HiPER studies focused on the targets for the demonstration
of advanced ignition with laser pulses of a few hundred kJ. Target scalability, robustness, rep-rate operation however
play a central role in the study.
In particular we have studied targets compressed by means of a multi-beam, multi-ns laser pulse of about 250-300 kJ
and either fast ignited by an ultra-intense, pulse of about 100 kJ delivered in 15 ps and focused onto a spot of diameter
about 30 m [3], or shock-ignited by a 300-500 ps multi-beam pulses of similar total energy, but irradiating a large
fraction of the target surface [4].
On the “laser” side, our objective is to identify the least expensive and most useful driver but not to preclude any
alternative laser design that can make the facility more flexible and help achieving fusion.

bruno.le-garrec@cea.fr; phone +33 557 044 847; fax +33 557 045 463; www.hiper-laser.org
Compression beams delivering 250 kJ and a peak power of 50-60 TW in a 10 ns shaped pulse at frequency 3
harmonic of the Nd:glass laser, i.e. wavelength of 0.351 
providing extremely uniform irradiation. Shock ignition requires a final 300 - 400 ps long spike at 3: 60-100 kJ and
200 TW; high symmetry is not required but focal spots smaller than those of the compression beam are required for
good laser absorption by the already partly compressed target [4,5]. Fast ignition is estimated to require 100 kJ of tightly
focused, 15 ps short pulses at 2. The scheme envisaged to allow for good energy coupling between laser beam and
forward propagating hot electrons with proper energy is based on a cone-inserted spherical capsule [6,3]. The ignition
beam propagates inside the empty hollow cone, interacts with the cone tip, releasing hot electrons at small distance from
the compressed fuel. At this stage, it is not clear whether the ignition beams should be coherently phased or not, and a
small angle set of 20 to 30 beams overlapping somewhere at the cone entrance is not easy to design.
The availability, operation and performance of large scale/aperture components and component technologies at high
average power are an unknown but essential entity. The level of industrial technological maturity with respect to the
laser technology needs of HiPER is still someway off, even if in specific areas the industrial potential is evident.
Although the laser system is made of a large number of sub-systems, we shall concentrate on some of the main topics of
the laser architecture, the final optics assembly and the way it is coupled to the target chamber.
1. TARGET DESIGN AND IRRADIATION SCHEME
A baseline target for HiPER was identified in 2007 [3] and was originally conceived for demonstrating fast ignition and
significant energy gain at a minimum total driver energy. The considered concept is a simple moderate-aspect ratio
cryogenic fuel shell, with an inserted cone. We have subsequently shown that this target (without the cone) can be shockignited by a laser with parameters achievable at the NIF and LMJ facilities [4,5].
Since then, we have performed a number of studies to assess the sensitivity and robustness of the concept. We have
analysed different aspects of irradiation, compression, symmetry, and ignition. These studies are summarized in Refs. [35;7-9], while studies on specific topics are reported in Refs, [10-15] However, other aspects, including key issues
concerning hot electron generation and transport in a low-intermediate density plasma and the interaction between cone
and spherical shell have not yet been addressed in detail.
The principles of the baseline are detailed in Ref. [3]. We have dimensioned a whole DT (cryogenic) shell, and a laser
pulse, in order to
 limit the energy of the ultra intense beam to 100 kJ,
 keep the energy of the compression laser as small as possible (but with some margin),
 reduce risks posed by Rayleigh-Taylor instability (RTI),
 reduce risks posed by plasma instabilities.
A design window then exists, provided the target is irradiated by a carefully tailored laser pulse, and appropriate
measures are kept to reduce RTI growth (adiabat shaping by intense picket, beam smoothing, very high target surface
quality, etc.). A crucial assumption is that at least 20-25% of the ultra-intense laser energy is delivered by hot electrons
in an approximately cylindrical region of high density plasma of radius of about 30 m and with (density*length) of less
than 1.2 g/cm2. This has to be demonstrated by detailed simulations and experiment referring to conditions (space- and
time-scales, plasma parameters) relevant to fast ignition. Indeed, simulations show that, given the unavoidable initial
divergence of the hot electron beam and hot electron scattering by the compressed plasma, at least 40-50 kJ of hot
electrons with average energy not exceeding 2 MeV are required for ignition [11,13]. This means that 50% of the 100 kJ
ultraintense laser pulse must be converted into a well focused hot electron beam with proper energy spectrum.
The resulting baseline capsule is illustrated in Fig. 1. As anticipated in the introduction, we have shown that this target
can also be shock-ignited. The laser pulse powers for fast and shock ignition are shown in Fig. 2.
Figure 1: baseline capsule used in simulation studies.
Figure 2. Laser pulses for fast ignition (a) and shock ignition (b). In both cases, the compression pulse is preceded by an adiabatshaping picket (of 100-200 ps duration). The picket pre-heats and the outer surface is decompressed. The shock driven by the picket
does not prevent compression, but helps to reduce the growth of Rayleigh-Taylor instability..
Of course, a realistic target must include structural materials. Furthermore, replacing the outer layers with a more
appropriate ablator material can increase laser light absorption (although additional means have to be used to limit
Rayligh-Taylor instability growth. We can consider different “families” of alternate designs
 designs based on the same concept as the baseline design and same global laser parameters (frequency, energy, peak
power), but different target parameters (aspect ratio, ablator materials),
 designs based on the same concept as the baseline design, but different laser frequency
 designs using a different ignition scheme, e.g. cone-less fast ignition [16], or proton fast ignition.
Studies on the above topics are in progress in the frame of the HiPER collaboration.
We are devoting a particular effort to shock ignition, which is particularly attractive because it does not require any
specific ignitor laser nor cone-in-shell targets. Moreover, the physics at work in the hot spot heating is laser driven
hydrodynamics, for which calibrated, predictive codes exist. (An outstanding remaining issue concerns ignition laser
absorption degradation due to laser-plasma instabilities) Also, the irradiation schemes, although not detailed in our
papers on shock ignition, are fully compatible with our 48 focal spot irradiation scheme.
Two important parameters characterizing the ignition shock are launching time and absorbed laser power. We have
studied their optimal values and tolerable variations by means of a series of 1D simulations. We have considered the
laser pulse shown in Fig. 2 (b), which consists of the HiPER compression pulse (without initial picket), followed,
towards the end of the implosion, by an intense spike of FWHM duration of 500 ps. The thermonuclear yields calculated
by CHIC are plotted in Fig. 3 as a function of spike launch time and absorbed laser power during the spike [4]. The
ignition threshold is found around 50 TW (absorbed power) for a spike launched at 10.1 ns. If we define as ``Ignition
Window'' (IW) the time interval ensuring a yield larger than 80% of the maximum yield at given power, we find that the
IW broadens as (absorbed) power increases from 50 TW up to 80 TW. At 80 TW a 250 ps window warrants a yield
larger than 16 MJ. The ignition window does not significantly widen at powers exceeding 80 TW, and one can
anticipate that the laser absorption saturates as will the target gain, hence there is no point in using greater powers. These
results have recently be confirmed by simulations with the code DUED, also for laser pulses with the initial picket [5]
Figure 3. Dependence of the target thermonuclear yield in MJ on the launch time and absorbed power of the ignition shocks, obtained
from a perfectly symmetric (1D spherical) simulation.
Using the same irradiation pattern as for the compression pulse (see, e.g., refs [4, 11]), the 3D ray-tracing package of
CHIC predicts an average absorption of 35% during the spike. However, by decreasing the focal spot diameter and
optimising the radial intensity distribution in the focal spot one may increase the absorption up to 50-60%. We have
found that a 160 TW, 80 kJ ignition pulse with 400 m radius, top-hat focal spot, delivered by specific beam lines ignites
the HiPER target [4,5]. A 200 TW pulse can than be assumed in order to have some margin [5]. In order to assess the
possibility to irradiate the target with a limited number of beamlines, we calculated the ignition of a spherical fuel
assembly driven by clusters of ignition beams placed at different polar angles. Preliminary simulations indicate that the
thermonuclear yield remains almost constant (20 MJ) whatever the angle is, this being mainly due to a very efficient
thermal smoothing in the conduction region [4]. However, these results need to be confirmed, since they were obtained
in simulations where the transport of (moderately hot) electrons in the corona was dealt by a flux-limited conduction.
Such a model may not be adequate under shock-ignition relevant conditions.
Another important issue for shock ignition concerns Rayleigh-Taylor instability (RTI) that may strongly perturb the
shell-hot spot interface during the shell deceleration and subsequent stagnation. As a first study of this important
problem, we performed 2D simulations of shock ignition of a non-uniformily compressed HiPER baseline target.
Compression was driven by a pulse with an l =12 Legendre perturbation, which resulted in a perturbed compressed core.
The perturbations seed RTI at deceleration and stagnation. A 150 TW SI laser spike was then delivered by beams
oriented at 54.7° with respect to the polar axis in order to produce a nearly spherical ignitor shock. The simulations [4]
show that despite the strong RTI occurring at stagnation, the target ignites and produces 20 MJ of thermonuclear energy,
i.e. just the same energy yield as obtained from a perfectly symmetric (1D spherical) simulation performed with the same
code. Other simulations [5] confirm that shock ignition is quite tolerant to intermediate mode (e.g. l =12) implosion
asymmetries, while sensitive to target mispositioning. According to some model simulations target misplacement must
be kept below 1.5% [5].
Irradiation geometries need to be flexible (easy switch between different configurations). The general requirement is rms
<< 1%, more stringent during the foot (drive of the first shock) than during the drive (acceleration). The effect on fuel
assembly strongly depends on spectrum and depends on the beam geometry, on the focal spots and on the affordable
random deviations. According to parametric scans using 1D-simulations, when most laser parameters are within 1%,
simulations show that the capsule achieves the <R> deemed for subsequent ignition [5,7]. Accuracy in the rising part of
the main pulse should be a few %. Stationary parts of the pulse can change by 5%. Compression is more sensitive to
changes of the target parameters that to laser parameters.
The number of beams is the number of different beam lines for achieving the highest irradiation symmetry on the target.
This number is equal to the number of focal spots, assuming that one beam is made of a bundle of beamlets (single
beams, quadruplet beams, etc). Several symmetric configurations have been considered: a procedure of optimisation on
the parameters of the super-Gaussian shape of the focal spot of the beams has led to the 48 configuration of illumination.
This 48 focal-spot configuration is shown in Fig. 4 and 5. The number of beams is equal to the number of the different
beam lines for achieving the highest irradiation symmetry on the target [17]. Work is now in progress to optimize the
irradiation scheme, also considering unavoidable random beam errors and target misplacement.
47°
8 beams
21°24
4 beams
N=48
m=1
a=0.6
Polar
angle
29.83
23°36
Azimut
s
Figure 4: 48 focal-spot irradiation scheme for compressing the capsule (for both fast ignition and shock ignition).
An important issue, concerning any ICF scheme is Rayleigh-Taylor instability (RTI) at the ablation front. Our
simulations indicate that the use of the initial picket significantly reduces RTI growth during the main compression pulse
[5], and damps the initial Richtmyer-Meshkov instability (RMI) that may amplify the seeds for RTI [5,14]. Notice that
RTI is seeded by target surface rugosity, target inhomogeneity, and laser imprint (i.e. target inhomogeneity induced by
laser short-scale non-uniformities). Imprint is reduced by making laser irradiation less coherent, i.e. by increasing laser
bandwidth. However we do not have yet determined bandwidth requirements for HiPER.
I need some explanation about the FI scheme and the maximum number of compression beams in the cone guide scheme
as illustrated in Fig.5. SORRY, BUT YOU HAVE TO ASK THIS TO CELIA OR TO MAURO TEMPORAL.
Figure 5: 48 focal-spot irradiation scheme in the cone guided fast ignition scheme.
2. LASER REFERENCE DESIGN
The primary HiPER facility will be operated on a “high” repetition rate basis (typically 10 Hz). Again, this repetition
rate is not known precisely because repetition rate, laser efficiency and target gain are related to the cost of electricity
that one would expect from the power plant design : see for example the “High Average Power Laser Program [18]”, and
the “Fusion cycle gain and cost of electricity [19]”.
This “high” repetition rate basis essentially means (in technological terms) that substantial new laser technology
development will be required. This stems from the simple fact that the existing “single shot” technology as used by the
National Ignition Facility or the Laser MégaJoule is, in general, not viable for high repetition rate requirements, although
certain component technologies or techniques could readily be adapted.
Current “high repetition rate” laser technology based on flashlamps could not be scaled in any feasible or credible
manner to the levels of efficiency required by HiPER. Our working assumption is that this beamline will be based on
Diode Pumped Solid State Laser (DPSSL) technology. This diode pumped technology is very promising technologically
but relatively immature in its development and certainly prohibitive in its cost at today’s prices when considering the
requirements of the HiPER facility. The availability, operation and performance of large scale/aperture components and
component technologies at high average power are an unknown but essential entity. The level of industrial technological
maturity with respect to the laser technology needs of HiPER is still someway off, even if in specific areas the industrial
potential is evident.
Central to the economics of any inertial fusion power plant is the fusion cycle gain. The fusion cycle gain is the product
of the driver efficiency  (the ratio of the energy delivered to the target and the energy supplied to the driver), the target
gain G (the ratio of the thermonuclear yield and the driver energy), the nuclear energy multiplier M (the energy change
due to neutron reactions, principally in the lithium-bearing blanket used to produce tritium), and the thermal-to-electric
energy conversion efficiency .
Net electricity Pn
Fusion
Target Gain = G
Blanket
Nuclear
Energy
Multiplier = g
Thermal to electric
Efficiency = 
Auxiliary equipments Pa
Driver efficiency = 
Figure 6: fusion cycle gain. Gain comes from the fusion of the target and the nuclear energy multiplication of the blanket. The gross
power that is delivered by the thermal to electric converter is divided into three parts: the net electricity, the auxiliary equipments and
the driver power.
In any inertial fusion power plant, the net electricity Pn is related to the gross electricity Pg through the power balance
equation:
Pn = Pg – Pa - Pd= Pg(1-fa-1/GM),
where Pa is the power used for auxiliary equipment and fa=Pa/Pg is typically a few percent of the gross electricity. Here
Pd is the driver power, and the driver’s re-circulating power fraction Pd/Pg is the reciprocal of the fusion cycle gain
GM
Since the nuclear energy multiplier M is typically 1.05 – 1.15, and the conversion efficiency  is typically 0.35 – 0.45,
the product G must be greater than about 10 to keep the re-circulating power fraction below 20% - 25%. If the recirculating power fraction much exceeds this fraction, the cost of electricity escalates rapidly.
A more recent study [20] taking into account new gain curves predicting high gain at low (< 2 MJ) laser energy
converges towards an optimum repetition rate around 20-25 Hz. Meier nevertheless mentions limitations on target
injection and tracking, chamber clearing, and laser cooling casting doubts on operating a plant at such high repetition
rates. Taking the 3ω DPSSL as an example, if the rep-rate is limited to 10 Hz, the cost of electricity is 4% higher; with a
5 Hz constraint, the impact becomes significant at 16% higher cost of electricity. Meier is also running a parametric
study aiming at identifying pertinent factors to reduce the cost of electricity. As a reference case he is using a 3ω DPSSL
with the following parameters: $400/Joule, 10% efficient laser, 45% power conversion efficiency and operation at 10 Hz.
Figure 7: cost of electricity (COE) versus repetition rate for KrF laser, 2ω and 3ω DPSSLs (from [19]). These curves were computed
for a fixed 1 GWe net output power from the IFE plant (i.e., power available after accounting for re-circulating power needs for the
lasers and other plant equipments).
Beams distribution at the target chamber centre is related to the target vacuum windows and ports location on the
chamber: laser experiments are configured for clear access of multiple diagnostic lines of sight.
The number of beams is equal to the number of the different beam lines for achieving the highest irradiation symmetry
on the target (single beams, quadruplet beams, etc). As explained above, this number is equal to the number of focal
spots on the target: 48.
The laser beam will be divided into parts or unit cells. Mechanical and electrical costs per cell scale favourably with
amplifier size up to a limit that is determined by the amplifier design: a high-gain diode-pumped solid-state amplifier
will quickly suffer from amplified spontaneous emission leading to a reasonable transverse size that cannot exceed 12-15
cm. This unit part or unit cell is called a single beam line (or beamlet) and 1 laser beam is a “bundle” of “n” single beam
lines. This bundle design has many advantages when considering focal spot conditioning, optical zooming and pulse
shaping; it has been described in details in [21].
There is a scientific requirement for HiPER to be able to produce temporally shaped optical pulses for successful
compression and ignition of the capsule. The compression beams will require a specific shape for driving this
compression. The current technology allows pulses to be shaped in time by using optical modulators in conjunction (also
called Arbitrary Waveform Generator, AWG). The temporal resolution is limited by the AWG.
A bundle of beamlets can be seeded from the same Front End. The pulse injected to each bundle to be amplified can be
designed to have a pulse shape with several shocks, the shock levels and times can then be adjusted at the front end by
the AWG that provides the different voltages to the optical modulators. The pulse should be designed to carefully send a
series of shocks to the capsule with the correct timings to achieve ignition. Some of the crucial parameters of the pulse
shape are the power of the first step, and the timing of the different steps.
A schematic of typical laser pulse used for compression beams is shown in Figure 2. The times of the initial shocks are
in nanosecond regime whilst the final rise of the pulse can be ~100ps. When there are multiple beams, it is possible to
shape the pulse by adding different pulse shapes. Moreover, our bundle principle allows building different complex pulse
shapes and overlapping different focal spots because it is based on time-delayed pulse shapes associated with different
beamlets and then leading to optical zooming [22] when reducing the focal spot step by step during the pulse.
40
50
30
20
100
10
0
150
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-20
200
-30
-40
40
250
50
100
150
200
250
50
30
20
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10
0
150
-10
-20
200
-30
40
-40
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30
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150
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250
20
100
10
0
150
-10
-20
200
-30
-40
250
50
100
150
200
250
P
0
t
Figure 8. Top left: each beamlet has a phase plate to create a speckle pattern inside the focal spot. Bottom left: many beamlets overlap
to smooth the focal spot. Right: introducing adequate timing between beamlets leads to optical zooming; the spot size is changing
during the pulse.
3. MAIN AMPLIFIER BASELINE
Achieving high average power means that the laser medium is able to sustain a very high thermal load. For a kJ level
amplifier at 10 Hz repetition rate, the average power will be 10 kW. Assuming a typical 15±5% pump to laser efficiency,
a 1 kJ amp will require from 5 to 10 KJ pump energy. This gives 10,000 to 20,000 diode bars (assuming one bar is 500W
peak power at 1ms pulse duration) per kJ amplifier. If the pump time is 1ms, a 10Hz repetition rate will require a 1%
duty cycle of the diode bars. In order to perform this task, four approaches are still being explored. Two are related to
using Yb:YAG gain medium, one is with Yb doped calcium fluoride and the last one is looking at Yb doped glass fibres
[24]. Although no down selection process has been possible during the HiPER preparatory phase, it is clear that the main
amplifier will be made of a set of at two amplifiers in a multiple pass configuration (as used in LMJ or NIF). One of the
possible solutions is that the gain medium will be split in many thin slabs allowing an efficient cooling through a gas
cooling technique like the one that has been tested during the Mercury program [25]. Moreover, we expect to run the
device at low temperature in order to increase both the laser efficiency and the thermal conductivity of the laser medium
[26]. Experiments are underway at the Central Laser Facility in the UK and the amplifier principle can be seen in Fig.10.
Amp 2
Amp 1
Extraction
Beam
Transport
Reverser 1
Reverser 2
Injection
Figure 10: multiple pass design of a set of two diode-pumped amplifiers.
Now the question is: how many beams do we need for HiPER full energy including compression, shock ignition and fast
ignition? Assuming the beamlet sub-aperture to be in the range = 12x12 cm2 to 14x14 cm2, 10 J/cm2 damage fluence that
scales as the square root of the pulse duration, near field modulation depth = 2 and THG efficiency = 50 %
Energy (kJ)
Duration (ns)
Energy range (J)
Number of beams
Compression 3
250
4
830 to 925
540 to 600
Shock ignition 3
60
0.4
260 to 360
335 to 456
Shock ignition CPA 3
60
2
588 to 800
150 to 204
Fast Ignition CPA 1
100
2
588 to 800
125 to 170
4. FOA AND TARGET CHAMBER
The Final optics Assembly must be designed according to the following requirements: convert the fundamental laser
frequency to the 2nd or the 3rd harmonic, separate wavelengths; focus each bundle of beam lines as a single spot at the
target location.
Moreover, the Final optics Assembly must be protected from the  particles and from the neutrons created at the
target chamber centre. In order to avoid or minimize back reflected light or any kind of radiation from the target, it is
necessary either to focus the beam with optical components far from the target (and so far a large focal length will be
required), or to tighten the beam with a small pinhole somewhere close to the chamber wall.
An example of the can be found with grazing incidence metallic mirrors (GIMM) from the High Average Power Laser
Program [27]. The real drawback of the metallic mirrors is the center distance from target: 24m to focal point. This is 3
times NIF/LMJ focal length (8m). We would like to take advantage of the metallic mirrors but with a short focal length
(to achieve small focal spots). In order to tighten the beam, a small pinhole can be put somewhere to separate the
chamber itself from the tubing section containing the optical components. We are currently thinking of using a pinhole
surrounded by a neutron shield made of concrete. One solution would be to use a cassette of cheap lenses with or without
debris shields. At the very beginning of NIF/LMJ designs, a rolling plastic film has been unsuccessfully tested as a
debris shield because the wave front distortion was too high. There are three critical parameters to deal with: 1) the size
of the optical components, 2) the target chamber diameter and 3) the focal length of the focusing optical component. In
fact, whatever the solution is, at least one optical component will be in the field of view of the radiation and the debris
from the target.
Our FOA design is as follows. A 4-m focal length gives a total distance between target chamber center and pinhole of 16
m because the lens is placed at 2f-2f position (magnification = -1). The size of this lens is 0.75 x 0.75 m2 and the clear
aperture for the beam is 0.6 x 0.6 m2. The size of the mirror is 0.75 x 1.06 m2 and the clear aperture for the beam is 0.6 x
0.85 m2. The chamber diameter is 10 m. The pinhole has a conical shape whose half angle is equal to that of the beam
(i.e 37.5 mrad or 2.15 °) and has a 2-mm diameter at its center.
Frequency
Conversion
Crystals
Phase
plate
Color
Separation
Device
Lens
Pinhole
Disposable
Lens
8m
5m
1m
Mirror
3.5 m
16 m
Figure 11: in this example a 4-m focal length is used together with a 5-m radius target chamber. The pinhole location will be 16 m
away from the chamber center assuming a -1 magnification of the “disposable” lens.
During the operation of the HiPER first engineering facility, up to 1.2·10 5 MJ per year of fusion neutrons yields are
foreseen. This irradiation level could be distributed in 100MJ detonations, accounting up to 100 detonations in a
single burst, with 10Hz repetition rate. A burst would take place every month. A first approach of chamber (but fully
developed in draft) for a burst mode repetitive operation is a spherical shell with a 5-m inner wall radius and a 10-cm
thick chamber made either of Al5083 or W+EUROFER97. It is an engineering system, without blanket, without
energy extraction and without Tritium breeding but conceived as a testing machine by itself that could also be used
for testing reactor components. The dose rates have been computed and different concrete shields have evaluated
within the target bay [28]. During the operation of the facility the stays inside the bioshield are exclusion areas.
Between bursts, manual maintenance might be performed inside the bioshield but outside the final optics assembly
(FOA) shield. Inside the FOA shield the residual dose rates are so high that only remote maintenance is allowed. The
FOA shield reduces the delivered dose rate in a factor of 30.3.
16-m radius concrete wall
with pinhole
Renewable lens
5-m radius Target Chamber
Figure 12: one possible scheme of the HiPER target chamber as used in Ref. 27 to simulate the radiation effects in burst mode
repetitive operation.
CONCLUSION
To be written
ACKNOWLEDGMENTS
The authors gratefully acknowledge the support of the Funding Agencies in undertaking this work (EC FP7 project
number 211737): EC, European Commission, MŠMT, Ministry of Education, Youth and Sports of the Czech Republic
and STFC, Science and Technology Facility Council of the United Kingdom.
REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
M. Tabak et al., Ignition and high gain with ultrapowerful lasers, Phys. Plasmas 1 (1994) 1626.
R. Betti et al., Phys. Rev. Lett. 98, 155001 (2007).
S. Atzeni, A. Schiavi and C. Bellei, Targets for direct-drive fast ignition at total laser energy of 200–400 kJ, Phys.
Plasmas, 14 (2007) 057202.
X. Ribeyre, G. Schurtz, M. Lafon, S. Galera and S. Weber, Shock igntion: an alternative scheme for HiPER,
Plasma Phys. Controlled Fusion 51, 015013 (2009).
S. Atzeni, A. Schiavi and A. Marocchino, “Studies on the robustness of shock ignited laser fusion targets”,
Plasma Phys. Controll. Fusion, 53 (2011), in press.
R. Kodama et al. Nature (London) 412, 798 (2001)
S. Atzeni, A. Schiavi, J. J. Honrubia, X. Ribeyre, G. Schurtz, Ph. Nicolaï, M. Olazabal-Loumé, C. Bellei, R. G.
Evans and J. R. Davies, Fast ignitor target studies for the HiPER project, Phys. Plasmas 15, 056311 (2008).
S. Atzeni, J. R. Davies, L. Hallo, J. J. Honrubia, P. H. Maire, M. Olazabal-Loumé, J. L. Fuegeas, X. Ribeyre,
A. Schiavi, G, Schurtz, J. Breil, Ph. Nicolaï, “Studies on targets for inertial fusion ignition demonstration at the
HiPER facility”, Nucl. Fusion, 49 (2009) 055008.
X. Ribeyre, Ph. Nicolaï, G. Schurtz, M. Olazabal-Loumé, J. Breil, P. H. Maire, J. L. Feugeas, L. Hallo and V.
Tikhoncuk, Compression phase study of the HiPER baseline target, Plasma Phys. Controll. Fusion, 50, 025007
(2008).
[10]
L. Hallo, M. Olazabal-Loumé, X. Ribeyre, V. Dréan, G. Schurtz, J-L. Feugeas, J. Breil, Ph. Nicolaï and P-H.
Maire, Hydrodynamic and symmetry safety factors of HiPER’s target, Plasma Phys. Controll. Fusion 51, 014001
(2009).
[11] S. Atzeni, A. Schiavi and J. R. Davies, Stopping and scattering of relativistic electron beams in dense plasmas and
requirements for fast ignition, Plasma Phys. Controll. Fusion, 51, 015016 (2009).
[12] J. Honrubia and J. Meyer-ter-Vehn, Fast ignition of fusion targets by laser-driven electrons, Plasma Phys.
Controlled Fusion 51, 014008 (2009).
[13] A. Debayle, J. J. Honrubia, E. d'Humières and V. T. Tikhonchuk, Characterization of laser-produced fast
electron sources for fast ignition, Plasma Phys. Control. Fusion 52, 124024 (2010)
[14] A. Marocchino, S. Atzeni and A. Schiavi, Numerical study of the ablative Richtmyer–Meshkov instability
of laser-irradiated deuterium and deuterium-tritium targets Phys. Plasmas 17, 112703 (2010).
[15] X Ribeyre, M Lafon, G Schurtz, M Olazabal-Loum´e, J Breil, S Galera and S Weber, Shock ignition: modelling
and target design robustness, Plasma Phys. Control. Fusion 51 (2009) 124030 (8pp)
[16] N. Naumova, T. Schlegel, V. Tikhonchuk, C. Labaune, I. V. Sokolov and G. Morou. “Hole boring in a DT pellet
and fast-ion ignition with ultraintense laser pulses, Phys. Rev. Lett. 102, 025002 (2009).
[17] M. Temporal, B. Canaud, S. Laffite, B. Le Garrec and M. Murakami, “Illumination uniformity of a capsule driven
by a laser facility with 32 or 48 directions of irradiation”, Physics of Plasmas 17 064504 (2010)
[18] High Average Power Laser Program, see web site at http://aries.ucsd.edu/HAPL/.
[19] J. Lindl, “Inertial Confinement Fusion”, (AIP Press, Springer) Chapter 13, page 184 (1994).
[20] W.R. Meier, "Economic Systems Analysis for Laser IFE and Potential Benefits of Fast Ignition," Proceedings
29th ECLIM (2006) ISBN:84-690-2624-0; LLNL report UCRL-CONF-221936 (2006).
[21] B. Le Garrec, C. Hernandez-Gomez, T. Winstone and J. Collier : « HiPER Laser Architecture Principles » , IFSA
2009, 6-11/9/09, San Francisco, USA, J. of Physics, Conf. Series 244 (2010) 032020.
[22] B. Canaud and F. Garaude, “Optimization of laser-target coupling efficiency for direct drive laser fusion”, Nucl.
Fusion 45 (2005) L43-L47.
[23] M. Temporal, B. Canaud and B. Le Garrec, “Irradiation uniformity and zooming performances for a capsule
directly driven by a 32x9 laser beams configuration”, Physics of Plasmas 17 022701 (2010)
[24] J.-C. Chanteloup, D. Albach, A. Lucianetti, K. Ertel, S. Banerjee, P. Mason, C. Hernandez-Gomez, J. Collier, J.
Hein, M. Wolf, J. Körner, B. Le Garrec : « Multi kJ level Laser Concepts for HiPER Facility » , IFSA 2009, 611/9/09, San Francisco, USA, J. of Physics, Conf. Series 244 (2010) 012010
[25] A.J. Bayramian et al, Fusion Science and Technology, 52, 383-387 (2007) & Fusion Science and Technology, 56,
295-300 (2009)
[26] B. Le Garrec, G. Bourdet and V. Cardinali, “Comparison of potential ceramic gain media”, Fusion Science and
technology, 56, 369-373 (2009)
[27] M.S. Tillack and J. E. Pulsifer: “Long-term survival of grazing-incidence metal mirrors for laser fusion”, Fusion
Science and technology 56, 446-451 (July 2009)
[28] R. Juarez, J. Sanz, J. Perlado, B. Le Garrec : « Neutronics and Activation Analysis of the HiPER Facility », 26th
Symposium On Fusion Technology, 27/9-1/10/10, Porto, Portugal.
[xx] B. Le Garrec : “Laser-diode and flash lamp pumped solid-state lasers”, Light at Extreme Intensities, AIP
Conference Proceedings, vol 1228, 111-116 (2010)