Diagnostics of Laser-Plasma Interactions

Abstract

The field of laser-plasma diagnostics is large, and is certainly too big to be covered fully in a short article. Here, we concentrate on a number of diagnostics which are of relevance to two areas of significant current interest, namely (1) relativistic laser-plasma interactions, and (2) hohlraum-driven inertial confinement fusion.

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1 Diagnostics of Relativistic Intensity Interactions

In the high intensity region of laser plasma interactions, significant numbers of ions with energies > 10 MeV/nucleon can be produced if the conditions are correct. The fraction of energy carried away can readily approach 10 % of the initial incident laser energy and there are predictions of significantly higher efficiencies being possible as the interaction intensity is increased. The diagnosis of these particles ofion beams is an important development in laser plasma interactions field which has made significant advances over the last decade and the remainder of this section will examine some of the main techniques currently being employed. Descriptions and reviews of the wider field of plasma diagnostics may be found in references [1,  2,  3,  4,  5,  6,  7].

1.1 The Thomson Parabola Ion Spectrometer

The classicalThomson parabola spectrometer used in laser plasma experiments as shown in Fig. 16.1 consists of parallel electric E and magnetic B fields through which ions are deflected according to their velocity v and charge Ze to mass m ratio. These instruments can be readily operated for ions with energies from keV to GeV with a suitable selection of field strength, geometry and detector. A pin hole placed before the plates samples a small fraction of the ions escaping from the target. The resolution of the instrument is primarily determined by the ratio of the geometrical projection of the ions through the entrance pin-hole to the dispersion due to the electric and magnetic fields and is typically in the region $\Delta E/E \sim 1{0}^{2} - 1{0}^{3}$. Although mutual space charge effects, where, the ions travelling together self repel and the beam effectively blows-up within the instrument can be important for lower energy lighter ions, it is typically not a significant issue even for sub ps bunches of MeV energy protons. The spatialresolution of the detector can also be important if it is inadequate to resolve the geometrical projection of the entrance pin-hole. Many variants of the basicThomson parabola spectrometer design exist. In Fig. 16.2 a wedged electric field plate configuration is employed to generate a greater deflection for a given applied voltage  [8]. In this instrument, a scintillator screen is coupled to an EMCCD to provide instantaneous readout of theion spectra. To enable a greater dynamic range of operation, which in this case was limited by the dynamic range of the EMCCD, a double pin-hole is used at the entrance slit which generates two tracks for each charge to mass ratio track. With a ratio of ∼  ×1, 000 in area between the two pin-holes this extends the dynamic range of the instrument. For high charge to mass ions (i.e. protons), the tracks from the two pin holes can be easily separated. However, for heavier ions where the change in charge to mass between adjacent ions is much less the tracks can merge and be difficult to separate.

Fig. 16.1

Schematic plan view of aThomson parabola spectrometer showing how the deflection due to the electric and magnetic fields can be used to separate the distribution of ions with different velocities and charge to mass ratios

Fig. 16.2

A modified Thomson parabola spectrometer schematic where the electric field plates are wedged to provide greater dispersion for a given applied voltage

1.2 Particle Detectors

Particle detectors such asCR-39 have been extensively used for charged particle detection from laser produced plasmas  [9] as they are simple to use and are virtually immune to radiation and electrons. As incident particles pass through theCR-39 (allyl diglycol carbonate plastic), polymer bonds are damaged due to the high rate of energy deposition (dE ∕ dx), in the long chains of the CR-39. When the plastic is then processed in hot NaOH, the shorter polymers are preferentially dissolved and a pit forms at the surface of the plastic which grows in size with etching/development time. The CR-39 is then scanned, typically using an optical microscope (with ∼ 0. 5 μmresolution) and the size and location of the pits are then identified. For individual protons in the 0.1–4 MeV region the CR-39 has a QE of 1 and every proton which is incident can be detected. An issue arises, when multiple particles are incident very close together. If the distance between the locations where the particles hit the CR-39 is smaller than the diameter of the pit, it becomes difficult to separate the individual pits. In this case, the optimal pit size after development is just resolvable by the optical microscope ( > 0. 25 μm). As the pit size depends on the development time and the deposited energy at the surface dE ∕ dx then conducting multiple development and scanning cycles enables a much higher density of particles to be identified. In Fig. 16.3 an example is given of the particle spectrum recovered using aThomson Parabola ion spectrometer with CR-39 as the detecting media. For the shortest development time used of 30 min, the particles where theBragg peak is within the layer dissolved are readily detected. However, clearly, particles with E > 2 MeV energy are not measurable. During two subsequent developments the detection of protons with energies up to 5 MeV is possible. However, for the 180-min development, the pit sizes for the lower energy protons now overlaps significantly and their number appears to artificially drop. The final particle spectrum is therefore the combination of the maximum particle densities detected for the multiple developments. As well as detecting ions where the Bragg peak is close to the front surface, if the ions are sufficiently energetic, pits are also observed when the Bragg peak coincides with the rear surface, typically ∼ 10 MeV for protons when the CR-39 is 1 mm thick.

Fig. 16.3

Proton spectrum detected using CR-39 in a Thomson parabola spectrometer using different development times for the CR-39

To measure the flux within a laser drivenion beam, detection usingCR-39 and direct counting of the individual ions is only practical when the total number of ions is < 10⁶. For experiments using drive lasers of > 0. 1 J energy, which can readily generate > 10⁹ ions per shot, sampling using multiple spectrometers to characterise the distribution and then integrating under the profile is routinely used. If the CR-39 is combined with a filter pack it can be used to measure where the edge of the ion beam is, as a function of energy and this can be combined with at least two spectrometer measurements to characterise the distribution. Numerical integration under the interpolated spectral and angular profiles can then be carried out to give a good estimate the total energy contained within the beam  [10].

In many experimentsRadio Chromic Film (RCF) stacks as shown in Fig. 16.4 are now routinely used to characterise theion beam distribution  [11]. The ion beam is incident upon a stack of films, with the peak sensitivity of each layer corresponding to the Bragg stopping distance of the ions. The angular and spectral profile of the beam can then be deconvolved from the deposited dose. The emission area of the ions can also be diagnosed by imposing structure on the rear surface of the target foil which can be observed on the RCF stack as shown in Fig. 16.4(b).

Fig. 16.4

(a) Example of a the exposures obtained on an RCF stack in the 4–30 MeV region. (b) Enlarged view showing target structure mapped onto the beam which can be used to characterise source size

Typical responses of Radio Chromic Films are in the 5–20 kGy region before saturation effects begin to set-in. The films are normally optically scanned to give a grey-scale image which can be converted todose using a measured calibration curve  [11]. It has been found that scanning at red wavelengths increases the sensitivity at lower doses  [12]. In many flat-bed scanners, theoptical densityresolution is limited by the noise in the optical sensor and scanner electronics. By combining the information from the red, green and blue channels the dynamic range can be routinely increased by ∼  ×10. The available dynamic range of RCF can also be increased up to doses of 200 kGy using UV scanning, as illustrated in Fig. 16.5.

Fig. 16.5

Radio Chromic Film calibration curve at 1,000, 450 and 320 nm wavelengths showing good response up to doses on 200 KGy at 320 nm

Nuclear activation techniques can also be used to measure theion beam angular and energy distribution  [13,  14,  15]. In an analogous method to RCF stacks, foils can be used in place of the film and the induced activity measured to characterise the beam. Ion induced reactions with different cross-sections within a single element or foils with multiple elements present can be used. The activity is usually measured after extracting the activated foil/s and typically involves significant post processing although methods to reduce the time needed are underway  [16]. An advantage of using activation over RCF is the much higher doses which can be measured  [17] without saturation issues arising and the very high spatial resolution achievable.

Two methods employing active detection of ions are to use either micro-channel plates or scintillators to convert the ion signal into an optical emission and then to use a camera or photodiode to measure the light. In ‘Time of flight’ techniques, a time resolved detector is situated at a distance from the interaction point and the arrival time after the interaction has taken place, is used to calculate the ion velocity.

1.3 Soft X-ray Spectroscopy

Spectroscopy of the soft x-ray region (1–50 nm) has played an important part in the analysis and understanding of coronal plasma physics and radiation transport in laser driven plasmas. There are many significant sources of broadening for line emission coming from a given atomic transition in a laser generated plasma. The primary mechanisms are Doppler broadening, opacity, Zeeman and Stark/pressure broadening. The Doppler broadened width Δλ _D for an ion of temperature T _i is given by:

$$\Delta \lambda _{D} = 2\lambda \left (\frac{2kT_{i}\ln 2} {m{c}^{2}} \right ) = 7.7 \times 1{0}^{-5}\lambda {\left ( \frac{T_{i}\left (eV \right )} {A\left (\mathit{amu}\right )}\right )}^{0.5}$$

where k is the Boltzmann constant, mc ² the rest mass of the ion and A the atomic weight. The Doppler width for a Ge emission line at 10 nm where the for ions are at a temperature in the range 200 < T _i  < 1, 000 eV is $\Delta \lambda _{D} = 1.5 - 2.7 \times 1{0}^{-3}$ nm. The other mechanisms will tend to add to the width of the line or reshape it. However, Doppler broadening is generally the dominant broadening mechanism for typical coronal plasma conditions and to resolve it requires an instrument with a resolving power of at least λ ∕ Δλ ∼ 5, 000.

As well as being used for understanding the physical mechanisms at play in a plasma, recent work has also examined laser driven plasmas as secondary sources for a wide variety of applications such aslithography, biological imaging and applications and materials science studies. Plasma based softx-ray lasers have relied on spectroscopic techniques in their development. From the demonstration of the first saturated soft x-ray laser  [18], through beam divergence control  [19], to identification of transitions with inner shell holes, medium resolution survey instruments have been the primary instrument of choice. In the field of high harmonic emission from laser driven gaseous targets  [20] and solids  [21] and in the detection of new generation mechanism, medium resolution instruments have played a pivotal role.

Each physical measurement or application has different requirements and in general, three types of spectrometer have been developed, (i) high resolution instruments capable of resolving the emission line profile (δλ ∕ λ > 10⁴), (ii) survey instruments capable of identifying individual lines and measuring the emission across a large fraction of the soft x-ray range few (δλ ∕ λ ∼ few ×10²) and low resolution broad band instruments giving the total energy or power emitted. As the real part of the refractive index for soft x-rays does not deviate significantly from unity, diffraction from gratings or transmission through binary gratings is normally used to disperse the radiation rather than refraction.

Many of the early softx-ray spectrometers were based on glancing angle diffraction from a curved grating in a Roland circle geometry. The resolving power of an ideal instrument is given by δλ ∕ λ ∼ ρl where ρ is the grating line density and l the illuminated length of grating. TheRoland Circle geometry can deliver near diffraction limited performance giving high resolution. However, in this geometry, the soft x-rays are focused onto a curved focal plane where the rays come at a small glancing angle onto the detector. This requires very high accuracy in initial setting up. Coupling over a large wavelength range onto the flat plane, typical of mostCCD’s and MCP’s is difficult and results in a limited in-focus spectral range. An alternative geometry adopted by many laboratories is to use a ‘flat-field’ spectrometer. In this instrument, the line density of the grating ρ is changed along the length of the grating in a precisely controlled manner to cause additional focusing which effectively rotates the focal plane to be nearly parallel to the grating normal.

In Fig. 16.6, the focal planes for a for a 1,200 l/mm flat-field grating with a point x-ray source located along the x axis at − 820 mm and the grating centred at the origin are shown for five different grating glancing angles. The ‘flat’ focal region of the spectrum can be seen across the 5–25 nm spectral region for the case of 4^∘ glancing angle in this situation.

Fig. 16.6

Focal planes for a 1,200 l/mm flat-field spectrometer at different glancing angles with a source at 0.82 m

As the total distance that x-rays travel from the entrance slit to the detector is almost constant, curved mirrors in the plane orthogonal to the dispersion have also been coupled to this grating. If the geometry is arranged as shown in Fig. 16.7 so that the source is effectively focused in the orthogonal plane onto the detector plane, then a significant enhancement of sensitivity can be obtained. In this imaging geometry, the spectrometer can be used to provide 1D spatial (in the Z direction as shown in Fig. 16.7) as well as spectral information. If the spectrometer is used in this ‘slitless’ mode, the size of the source in the y direction is imaged onto the detector by the grating and for mm scale or larger plasmas can significantly reduce the spectral resolving power. However, this effect can be utilised in some cases to create a quasi image of larger plasmas where the spectral and spatial information are both convolved. By careful analysis of the detected signal in multiple orders, deconvolution can be performed in cases where the spectral features are well separated as is usually the case from lower Z emitters in this spectral region.

Fig. 16.7

Schematic layout for a softx-ray flat-field spectrometer

If a streak camera is used as the detector  [22] it is possible to readily obtain ps resolution of the duration of soft x-ray emission. However, the dynamic range of current streak cameras operating with ps resolution is typically ∼  ×10. 

Fig. 16.8

The key implosion parameters which must be controlled ifignition is to be achieved (Figure courtesy of National Ignition Facility, LLNL)

2 Inertial Confinement Fusion Diagnostics

Inertial confinement fusion is achieved by the compression of capsules of DT ice and gas to ultra-high pressures and temperatures by illuminating them with multiple laser-beams (‘direct drive’) or the x-rays produced inside a hohlraum when that is heated by laser light (‘indirect drive’). The latter approach is viewed as likely to be more successful, and is the approach adopted at the National Ignition Facility at LLNL, USA. Target design involves an optimisation of maximising the fuel compression whilst minimising the internal energy imparted to the fuel (i.e. the fuel must be kept on a lowadiabat). The usual approach is to approximate isentropic compression by employing a sequence of three shock-waves of increasing strength, followed by a fourth, stronger, shock that drives the compression. In order to achieve indirect-drive ignition with the relatively small amount of laser energy available on the NIF, a number of criteria must be met (see Fig. 16.8). The implosion must be sufficiently fast (i.e. the shell must reach a high-enough velocity) and symmetric, the fuel must remain on a low adiabat during the compression, and the amount of hydrodynamic mix must be small. Further details may be found elsewhere (e.g.  [23,  24] and references therein).

The diagnostics used to measure each of these parameters are now discussed.

2.1 Shell Velocity

The shell velocity is governed by thehohlraum performance, and in particular by the shape and timing of the shocks driven into the ablator by x-rays arising from the interaction of the incoming laser light with the hohlraum wall and – to some extent – with the capsule. Figure 16.9 shows the concept. As the hohlraum is approximately a black-body, it is the temperature reached by the hohlraum which is usually quoted (flux ∝ T ⁴), even though the diagnostic (Dante) which is usually employed to measure the temperature actually measures the radiated flux. A description of some early work on the Nation Ignition Facility is given by Meezan et al.  [25].

Fig. 16.9

(a) shock strengths and timings are adjusted so that they converge on the inner surface of the DT ice layer. (b) Temporal history of laser intensity and resulting radiation temperature for an ignition target on the NIF. A shock-timing tuning campaign will iteratively adjust (arrows) the laser pulse shape to optimise shock timing (Adapted from Lawrence Livermore National Laboratory  [26])

2.2 Dante – A Hohlraum Temperature Diagnostic

Dante is an absolutely-calibrated, multi-channel, time-resolved x-ray spectrometer  [27]. In France it is known as theDMX  [28]. Each channel comprises an x-ray sensitive vacuum photo-diode, with a filter and perhaps an x-ray mirror to define the channel response. Figure 16.10 shows the concept  [27].

Fig. 16.10

Dante concept. Multiple filtered x-ray diodes (some with mirrors) record time-resolved measurements of x-ray flux in different regions of the x-ray spectrum (Hohlraum image courtesy National Ignition Facility, LLNL)

There are two Dantes on NIF; the one nearest the equatorial plane is shown in Fig. 16.11. The equator is in the horizontal plane at the NIF because the hohlraum axis is vertical and so the beams enter the hohlraum from above and below.

Fig. 16.11

The equatorial NIF Dante (Image courtesy National Ignition Facility, LLNL)

The x-ray diode used on ORION is shown in Fig. 16.12. Photons enter the detector from the right and pass through the grid anode, which is an etched nickel grid (transmission ∼ 80), and strike the photocathode, liberating photo-electrons. The outer connector is a 50 Ω bias cable that maintains a positive bias voltage (typically 1 keV) on the anode grid; the photo-electrons are thus attracted to the anode, inducing an image charge on the anode as they move across the gap. A positive pulse is transmitted along the cathode stalk and propagates to the output cable.

Fig. 16.12

ORION Dante photo-diode

In the ORION Dante there are ten channels, each designed to cover part of the x-ray spectrum through the use of different photo-cathodes, filters and mirrors (Table 16.1).

Table 16.1 ORION Dante channel details

Spectral coverage is shown in Fig. 16.13 where it can be seen that the device is sensitive only up to around 5 keV. This is appropriate, given that the peak of the black-body spectrum is at around three-times its temperature (around 1 keV for a 300 eV hohlraum, which is the highest temperature that ORIONis likely to produce), and that the gold M-band lines are around 2.5 keV.

Fig. 16.13

The spectral coverage of the ORION Dante

2.3 VISAR – A Shock-Breakout Timing Diagnostic

A VISAR Velocity Interferometer System for Any Reflector (Velocity Interferometer System for Any Reflector) enables changes in velocities to be measured by using theDoppler shift of a laser beam diffusely reflected from a moving target. Figure 16.14 shows the principle.

Fig. 16.14

Principle of VISAR. Coherent light illuminates the object of interest. An optical relay directs light toward the object and collects the reflected radiation. Reflected light is sent to an interferometer, producing an output containing the input signal and a time delayed version of the input signal. The output is sensed with fast optical detectors and analysed to infer the object’s motion (Figure from Dolan   [29])

Figure 16.15 shows how this can be employed inside a capsule to measure the arrival time of the shocks on the inside wall of the DT ice layer and the velocity imparted to it.

Fig. 16.15

Shock-timing tuning experiments use ignition-style targets that have a re-entrant cone in the capsule. The capsule and cone are filled with liquid deuterium. Optical diagnostics probe the inside of the capsule through the window and aperture in the cone (Adapted from Lawrence Livermore National Laboratory [26])

Figure 16.16 shows typical VISAR data, showing (a) fringes and (b) the inferred velocities. This information is useful also in determining how much the capsule has been heated by the passage of the shocks.

Fig. 16.16

(a) Typical VISAR trace showing fringes measured on inside surface of NIF capsule, and (b) the inferred velocities (Images courtesy of National Ignition Facility, LLNL)

The ORION laser at AWE will be equipped with a VISAR system, but this is not yet operational.

2.4 Hohlraum Performance

It might be thought that decreasing the volume of the hohlraum would increase its temperature for a given amount of laser energy shone into the hohlraum. This is true for ‘large’ hohlraums, but as the size is reduced the plasma ablated from the inside walls of the hohlraum can move into the laser path, leading to plasma instability growth and the generation of energetic electrons and back-scattered light through the two-plasmon decay and stimulated Brillouin and Raman backscatter. To characterise the energetic electron numbers and energies so generated it is usual to use x-ray spectrometers which operate at higher photon energy than the Dante, and which are usually time-integrating. ORION employs the ‘filter-fluorescer’ for this. Backscattered light is usually measured in terms of that which falls within the laser’s focusing lens(es), and that which falls just outside the lens(es), the latter being known as near-backscatter imaging (NBI). Each of these diagnostics is now discussed.

2.5 The Filter-Fluorescer (FFLEX)

The filter-fluorescer (FFLEX) is used to record absolute, time-integrated hard x-ray spectra, from around 20 keV to around 100 keV, using a number of separate channels (eight on ORION and NIF) each of which contains a pre-filter, a fluorescer, and a post-filter. A block diagram of the ORION FFLEX is shown in Fig. 16.17.

Fig. 16.17

Block diagram of one of the eight channels of the FFLEX used on ORION

By appropriate selection of pre- and post-filters and fluorescers varying channel responses can be defined, as shown in Fig. 16.18. It is usually used to characterise the x-rays generated by so-called hot-electrons generated inside hohlraums.

Fig. 16.18

Channel responses for ORION FFLEX

A CAD drawing of the FFLEX as deployed on ORION is shown in Fig. 16.19.

Fig. 16.19

FFLEX as deployed on ORION

2.6 The Apache High-Energy Spectrometer

The Apache high-energy spectrometer is another absolute, time-integrated x-ray spectrometer, but sensitive to ∼ 100 to ∼ 2 MeV x-rays. The ORION device has eight channels. It is typically used for hot electron temperature measurements for short-pulse laser-target interactions at $1{0}^{18} - 1{0}^{21}\,\mathrm{Wc{m}^{-2}}$ intensities. The ORION device has 1.6 or 17 ns temporal resolution (i.e. two scintillator types) to allow discrimination against charged particles and neutrons. It is shown in Fig. 16.20.

Fig. 16.20

The ORION Apache-like diagnostic has eight channels, each consisting of a filter and ascintillator /photomultiplier

Channel responses are defined in a similar way to those of the FFLEX by choice of filter and scintillator. By differencing channels a degree of spectral sensitivity can be obtained (Fig. 16.21).

Fig. 16.21

Channel responses (a) and spectral definitions achieved by differencing channels (b)

2.7 Backscattered Light Diagnostics

2.7.1 Full-Aperture Backscatter Diagnostics

The back-scatter signal can generally be attributed to two main processes, namelyStimulated Brillouin Scattering (SBS), where the laser interacts with ion acoustic waves, and which typically occupies a narrow wavelength band in the region of thelaser wavelength (351 nm), andStimulated Raman Scattering (SRS), where the laser interacts with electron plasma waves, and which occupies a broad wavelength band in the range 350–700 nm. On ORION one beam from each of the two five-beam clusters is equipped with a full-aperture back-scatter (FABS) diagnostic station (beam-lines LP5 and LP6): back-scattered light from the plasma is re-collimated by the main focussing lens, back through the final turning mirror, and in to the back-scatter station. The diagnostic records SBS and SRS signals independently. It is shown in Fig. 16.22. Each of the two short-pulse ( ∼ 0. 5 ps) beams onORION is also equipped with a FABS capability, though only for SRS as the growth-rate for SBS is expected to be significantly longer than the pulse-length on these beams. On these short-pulse arms the SRS light detected is that which has leaked through the final focusing parabolae.

Fig. 16.22

The full-aperture backscatter diagnostics on ORION

2.7.2 Near-Backscatter Imaging

Near-backscatter imaging (NBI) provides information on the light back-scattered just outside the main focussing optics. On ORION it is used to measures the amount of near-backscattered light in the SBS and SRS spectral bands. Spectralon plates placed around (some of) the focusing optics are viewed by cameras on the opposite side of the target chamber wall to give time-integrated 2D profiles (Fig. 16.23). The diagnostics are on the same long-pulse beams as the FABS.

Fig. 16.23

The near-backscatter imaging stations on ORION.Spectralon plates placed around (some of) the focusing optics are viewed by cameras on the opposite side of the target chamber wall to give time-integrated 2D profiles

Time-resolved (timeresolution ∼ 150 ps) measurements are made in certain locations by fibres inserted into the NBI plates (Fig. 16.24).

Fig. 16.24

For time-resolved near-backscatter measurements on ORION, light is sampled at the surface of the scatter plate and transported tophotodiodes and a fibre spectrometer viaoptical fibres (SRS 460HP single-mode fibres; SBS Graded-index fibres; multi-mode fibres for time-integrated signal transportation)

2.8 Shape: The Gated X-ray Imager

TheGated X-ray Imager, or GXI, is a work-horse diagnostic. It typically consists of a number of separately gated strip-lines which have been deposited on the front of a microchannel plate. The x-ray signal is imaged onto the MCP by a series of pinholes. Fig. 16.25 shows the concept.

Fig. 16.25

A composite example of the MCP image surrounded by an image plate image and an overlay of the pinhole pattern (From Kyrala et al.  [30])

As the gate pulse propagates across the surface of the MCP the gain of the MCP increases and then decreases, allowing a short-duration image to be recorded from each pinhole. Fig. 16.26 shows an example from reference  [30]. More detail may be found in references  [31,  30].

Fig. 16.26

A typical image from the NIF GXD (From Kyrala et al.  [30])

2.9 Mix

Spectroscopy is a powerful diagnostic tool  [32] which may be used to diagnose mix, a phenomenon which is likely to be a significant influence on the performance of ignition capsules  [33]. In recent experiments reported by Regan et al.  [34] the ablator was doped with germanium to minimise pre-heat of the ablator closest to the DT ice caused by Au M-band emission from the hohlraum x-ray drive. The K-shell line emission (Fig. 16.27) from the ionised germanium that has penetrated into the hot spot provides an experimental signature of hot-spot mix. Analysis of such spectra is often undertaken with the aids of codes such as FLY  [35],FLYCHK  [36] orSPECT3D  [37].

Fig. 16.27

Time-integrated spectrum showing the presence ofgermanium in the hot-spot (From Regan et al.  [34])

3 Summary

The field of laser-plasma diagnostics is a large one, and is certainly too big to be covered comprehensively in a short article such as this. We chose therefore to highlight diagnostics relevant to two areas of significant current interest, namely the interaction of ultra-short laser pulses with matter andhohlraum-driven ICF. In both areas development is rapid, as the number of short-pulse experimental facilities around the world continues to increase, and the significant technical difficulties associated with ICF continue to drive the development of novel diagnostics with high spatial, temporal and spectral resolution. It is hoped that this chapter has whetted the appetite of the reader to explore further some of the recent exciting developments made in this field.