Changeset 741 in ETALON for papers/2016_HDR_ND/Advanced_diags/smithpurcell.tex

Timestamp:

Sep 25, 2017, 10:58:10 PM (7 years ago)

Author:

delerue

Message:

More work on HDR

File:

• papers/2016_HDR_ND/Advanced_diags/smithpurcell.tex (modified) (5 diffs)

papers/2016_HDR_ND/Advanced_diags/smithpurcell.tex

@@ -316 +316 @@
 This relation is purely a consequence of the fact that waves emitted by a grating will interfere and in each direction constructive interferences correspond to specific wavelengths.
 
-The  intensity of radiation emitted by a single electron (single electron yield), per unit solid angle ($\Omega$) and per frequency ($\omega$) is given by 
+The  intensity of radiation emitted by a single electron (single electron yield), per unit solid angle ($\Omega$) is given by 
 \begin{eqnarray}
-\frac{d^2I_1}{d\omega d\Omega} & = & \frac{e^2 \omega^2 l^2}{4 \pi^2 c^3} R^2 \exp{\frac{-2 x_0 }{\lambda_e}}
+\frac{dI_1}{d\Omega} & = & \frac{L}{l^2}\frac{2 \pi e^2 n^2 \beta^2}{\left(1 - \beta \cos \theta\right)^3}R^2 \exp{\frac{-2 x_0 }{\lambda_e}}
 \end{eqnarray}
-where $e$ is the electron charge, $x_0$ is the beam grating separation, $\lambda_e$ is the evanescent wavelength of the virtual radiation emitted by the beam and $R^2$ is a factor reflecting the coupling of the beam with the grating.
+where $e$ is the electron charge, $L$ the grating length, $x_0$ is the beam grating separation, $\lambda_e$ is the evanescent wavelength of the virtual radiation emitted by the beam and $R^2$ is a factor reflecting the coupling of the beam with the grating.
+
+
 
 The evanescent wavelength is given by 
@@ -329 +331 @@
 where $\gamma$ is the Lorentz factor, $\phi$ is the azimuthal angle (the ascension above or below the plane perpendicular to the grating surface and passing by the beam).
 
+An example of values of single electron yield taken from~\cite{delerue:in2p3-01322166} is shown on figure~\ref{fig:sey2d}.
+
+\begin{figure}[htbp]
+  \centering
+  \includegraphics[width=80mm]{Advanced_diags/MOPMB003f2.pdf}
+  \caption{Single electron yield of Smith-Purcell radiation for a  $40\times180$ \si{mm^2}   grating  with a 8~mm pitch and  a$30^o$ blaze angle. Image taken from~\cite{delerue:in2p3-01322166}. }
+  \label{fig:sey2d}
+\end{figure}
+
+
 
 As discussed above, equation~\ref{eq:coherent} applies to Smith-Purcell Radiation and the total radiation intensity emitted from a charged particle bunch of multiplicity $N$ is given by:
 \begin{eqnarray}
-\frac{d^2I}{d\omega d\Omega} & = & \frac{d^2I_1}{d\omega d\Omega} \left[ N + N(N-1) \mathcal{F}(\omega) \right]
+\frac{dI}{ d\Omega} & = & \frac{dI_1}{ d\Omega} \left[ N + N(N-1) \mathcal{F}(\omega) \right]
 \label{eq:SP_coherent}
 \end{eqnarray}
 where $\mathcal{F}(\omega)$ is the form factor introduced in equation~\ref{eq:form_factor}.
 
+On figure~\ref{fig:compare_profiles} one can see a comparison of different profiles with the same FWHM (\SI{5}{ps}) but with different shapes and how this changes the expected CSPR signal.
+ 
+\begin{figure}[htbp]
+ \centering
+  \includegraphics*[width=70mm]{Advanced_diags/shape_profile.eps}
+  \includegraphics*[width=70mm]{Advanced_diags/shape_comparison.eps}
+  \caption{Comparison of several bunch profiles with the same FWHM (\SI{5}{ps}) but with different shapes (left) and predicted CSPR signal for each of these profiles (right). The capability to distinguish internal features of the beam and in particular substructures appears clearly.  The parameters used for these simulations are based on the experiment done at CLIO (see section~\ref{sec:CLIO}).}
+   \label{fig:compare_profiles}
+\end{figure}
+
+
+
+
 One important difference between CSPR and other radiative methods is that the choice of the grating will change the radiation intensity observed at different frequencies. On figure~\ref{fig:grating_effect} one can see the radiation intensities observed for the same bunch profile but with different gratings pitches.
 
@@ -342 +367 @@
 \center
 \includegraphics[width=7.5cm]{Advanced_diags/SP_signal_different_gratings.eps} 
-\caption{Radiation profiles observed for the same pulse but for different grating pitches.}
+\caption{Radiation profiles observed for the same pulse but for different grating pitches. The parameters used for these simulations are based on the experiment done at CLIO (see section~\ref{sec:CLIO}).}
 \label{fig:grating_effect}
 \end{figure} 
@@ -360 +385 @@
 \end{eqnarray}
 
-This has led me to study with a student~\cite{rapport_duval} whether it would be possible to benefit from the advanced work done in the field of grating theory~\cite{diffraction_gratings_Loewen} to estimate $R^2$. We produced some predictions but these are rather close to what has been obtained with simulation codes based on~\cite{Brownell:2005my} and therefore we have not yet been able to distinguish the two approaches. This may become possible at the experiment described in~\ref{sec:CLIO}.
+This has led me to study with two students~\cite{rapport_solene,rapport_duval} whether it would be possible to benefit from the advanced work done in the field of grating theory~\cite{diffraction_gratings_Loewen} to estimate $R^2$. We produced some predictions but these are rather close to what has been obtained with simulation codes based on~\cite{Brownell:2005my} and therefore we have not yet been able to distinguish the two approaches. This may become possible at the experiment described in~\ref{sec:CLIO}.
 
 
@@ -456 +481 @@
 
 
+\subsubsection{Near field, far field and pre-wave effects}
+
+As the Smith-Purcell radiation is formed by a grating, there is a formation length and the number of teeth of the grating, the distance between the grating and the detector have to be taken into account. 
+The line width of the radiation is given by the formula:
+\begin{equation}
+\frac{\delta \lambda}{ \lambda} = \frac{l}{nL}
+\end{equation}
+
+The effect of the grating-detector distance has been discussed in details in~\cite{E203prstab}.
+
+With a student I also studied the predictions for the pre-wave effect~\cite{malovystia-2015} and this work shows that corrections might have to be applied, especially at very high energy. However owing to the non observation of this effect in~\cite{1748-0221-6-07-P07004} as discussed in section \ref{sec:OTR_interference}, experimental verification of the effect of pre-wave interferences and accurate calculation are needed. Experimental attempts will be discussed in section~\ref{sec:SPESO}.
+
 
 \section{Experimental study of Coherent Smith-Purcell radiation}
 
-One of the remaining difficulties preventing the adoption of Smith-Purcell radiation as a longitudinal profile is that 
-
-
-\subsection{Smith-Purcell radiation measurement at FACET}
-\subsection{Smith-Purcell radiation measurement at SOLEIL}
-\subsection{Smith-Purcell radiation measurement at CLIO}
-\label{sec:CLIO}.
-
-
-
-
-Image CLIO 3 diff profiles
+When I joined the effort at the University of Oxford on CSPR our main goal was to demonstrate that CSPR could be used as a longitudinal profile diagnostic in the sub-picosecond regime. The work would lead to the E-203 collaboration that took data at SLAC. Later, after I moved to Orsay, I decided to extend this effort to  better understand the properties of CSPR using a test setup installed at SOLEIL and called SPESO and to also study how to make CSPR a tool available in accelerators control room, by making experiments on the CLIO accelerator.
+
+\subsection{Smith-Purcell radiation measurement at FACET: E-203}
+
+FACET (Facility for Advanced Accelerator Experimental Tests) was a \SI{20}{GeV} electron accelerator installed on the SLAC campus in Stanford, California~\cite{Seryi:2009zzc}. It had the advantage of being the only test facility offering easy access to sub-picosecond bunches.
+
+In 2010 we proposed to re-use the hardware from a previous experiment~\cite{Doucas_ESB} to use it at FACET to measure sub-picosecond bunches. This led to the formation of the E-203 collaboration.
+
+The experiment has been described in details in~\cite{SP_E203_first_paper}. It consists of a carousel on which 3 different gratings and a blank (a flat grating without teeth are mounted). This carousel can be moved inside the accelerator vacuum to bring the grating close from the beam. Opposite to the carousel there are 11 silicon windows located every \ang{10} in $\theta$ from \ang{40} to \ang{140}. Outside the movable windows waveguide array plates (WAP) filters are used to filter only the radiation at the wavelength expected from the selected grating. After the filters Winston cones concentrate the radiation within  their acceptance onto pyroelectric detectors. Several pictures of the E-203 experiment are shown on figure~\ref{fig:E_203_setup} and the optical elements are shown on figure~\ref{fig:E_203_setup_optics}.
+
+
+%\vspace*{1cm}
+\begin{figure}[htbp]
+   \centering
+    \begin{tabular}{cc}
+   \vspace*{-0.5cm} & \multirow{3}{*}{\includegraphics*[width=68mm,angle=90]{Advanced_diags/E203_motor_side.JPG}} \\
+   \includegraphics*[width=50mm,angle=0]{Advanced_diags/E203_filters_side.JPG} \\
+   \includegraphics*[width=50mm]{Advanced_diags/E203_carousel.JPG}    
+       \end{tabular}
+   \caption{The E-203 experiment (during pre-installation tests) seen from the detectors side (top left), from the motors side (right) and the grating's carousel (bottom left). Images taken from~\cite{andrews:in2p3-00830708}.}
+   \label{fig:E_203_setup}
+\end{figure}
+
+\begin{figure}[htbp]
+   \centering
+   \hspace*{-.0cm} \begin{tabular}{ccc}
+\includegraphics*[height=60mm]{Advanced_diags/E203_filters.png} \hspace*{-2cm}&
+\includegraphics*[height=60mm]{Advanced_diags/E203_Winston_cone.png} &
+\includegraphics*[height=60mm]{Advanced_diags/E203_optics.png} 
+       \end{tabular}
+   \caption{The optical parts of the E-203 experiment: (from left to right) the filters, the optical concentrators (winston cones) and the optical assembly (image taken from~\cite{E203prstab}).}
+   \label{fig:E_203_setup_optics}
+\end{figure}
+
+The experiment was successful in measuring sub-picosecond bunches~\cite{SP_E203_first_paper,E203prstab,andrews:in2p3-00830708}. and examples of the profiles measured are shown on figure~\ref{fig:E_203_profiles}.
+
+
+
+%\vspace*{1cm}
+\begin{figure}[htbp]
+   \centering
+    \begin{tabular}{cc}
+   \includegraphics*[width=75mm]{Advanced_diags/E203_high_comp_rho.png}  & 
+   \includegraphics*[width=75mm]{Advanced_diags/E203_high_comp_profile.png} \\   
+   \includegraphics*[width=75mm]{Advanced_diags/E203_med_comp_profile.png}  & 
+   \includegraphics*[width=75mm]{Advanced_diags/E203_low_comp_profile.png} \\   
+       \end{tabular}
+   \caption{ Top left: The magnitude of the Fourrier Transform of the time profile of the bunch for a ?high compression? run on the 9 April 2013 (see text in~\cite{E203prstab}). Other plots: bunch profile reconstructed from measurements at different times and with different bunch compression settings (top right: 9 April 2013, high compression; bottom left: 9 April 2013, medium compression; bottom right: 25 june 2013). Plots taken from~\cite{E203prstab} where more explanations can be found.}
+   \label{fig:E_203_profiles}
+\end{figure}
+
+Background rejection is an important problem for radiative measurements. Because CSPR uses the dispersion induced by the grating it is less sensitive than other methods but still not immune. One method to measure the background is to expose a "blank" grating, that is a grating without teeth, to the beam and measure the signal produced. This signal is then considered to be the background.
+
+Another solution could be to measure the two polarisation components of the signal: CSPR is known to be polarized whereas most backgrounds aren't.  We verified this with the E-203 apparatus~\cite{E203prstab} (see figure~\ref{fig:E203_polar}). and I worked further on that topic with a student who had taken part in the experiment~\cite{rapport_solene}.
+
+
+\begin{figure}[htbp]
+   \centering
+\includegraphics*[height=60mm]{Advanced_diags/E203_polar.png} 
+   \caption{The measured degree of polarisation of the grating signal as a function of observation angle. The solid line is the theoretically predicted polarisation of CSPR, as a function of wavelength (see text in~\cite{E203prstab} for details; plot taken from~\cite{E203prstab}).}
+   \label{fig:E203_polar}
+\end{figure}
+
+
+
+Additional measurements of the polarization and the azimuthal distribution of CSPR have been done by the E-203 experiment and are being analyzed.
+
+
+\subsection{Smith-Purcell radiation measurement at SOLEIL: SPESO}
+\label{sec:SPESO}
+
+Many questions about Smith-Purcell arose when we formed the E-203 collaboration and FACET being far from Europe, it was not the best suited place to make detailed comparison between theory and experimental results.
+
+With colleagues from Synchrotron SOLEIL I therefore started another experiment called SPESO (Smith-Purcell Experiment at SOLEIL). SPESO is installed at the end the Helios, the SOLEIL linac. For simplicity reasons SPESO uses a fixed grating on a movable arm. Opposite to this window is a z-cut quartz window (transparent at the wavelengths at which the radiation is expected). In front of that window a set of 3 translation stages and 4 rotation stages allow to move detectors in 3D and mesure the intensity of Smith-Purcell radiation at different locations. 
+The layout of the experiment is shown on figure~\ref{fig:SPESOlayout} and a photo is shown on figure~\ref{fig:SPESOphoto}. The experiment has been described in details at~\cite{delerue:in2p3-00862652}.
+
+%\vspace*{2cm}
+\begin{figure*}[tbp]
+   \centering
+\includegraphics*[width=85mm]{Advanced_diags/test_stand_step1_v5_cleaned.pdf} 
+   \caption{The experimental setup of SPESO at the end of the SOLEIL Linac (image taken from~\cite{delerue:in2p3-00862652}).}
+   \label{fig:SPESOlayout}
+\end{figure*}
+
+%\vspace*{2cm}
+\begin{figure}[htbp]
+   \centering
+          \hspace*{-0.5cm}\begin{tabular}{cc}
+ \includegraphics*[width=90mm,angle=90]{Advanced_diags/SPESO_layout.jpg} &
+    \includegraphics*[width=0.45\textwidth]{Advanced_diags/MOPAB025f1.jpg}
+       \end{tabular}
+   \caption{The experimental setup of SPESO at the end of the SOLEIL Linac: left, as it was in 2015 (image taken from~\cite{delerue:in2p3-00862652}) and right with the polarizer installed in 2016 (image taken from~\cite{Delerue:IPAC17-SOLEIL}). On both images the electrons travels from left to right.
+   }
+   \label{fig:SPESOphoto}
+\end{figure}
+
+The first SPESO signal was difficult to obtain because the pulse length had been underestimated. After some searching we finally found some signal at wavelength much longer than expected (see figure~\ref{fig:SPESO_first_data}). These data allowed us to reconstruct the spectrum emitted by the bunch and its profile (see figure~\ref{fig:SPESO_signal_spectrum}). These results were reported in~\cite{Delerue:2016zgr} where detailed explanations of these figures are available. Discussion with persons who contributed to the commissioning of the linac showed that our measurement is in agreement with the measurements done during the linac commissioning.
+
+
+
+
+\begin{figure}[htbp]
+%   \vspace*{-.5\baselineskip}
+   \centering
+       \hspace*{-0.5cm}\begin{tabular}{cc}
+   \includegraphics*[width=75mm]{Advanced_diags/MOPMB002f2_negated.png} &    \includegraphics*[width=75mm]{MOPMB002f5a.png}
+       \end{tabular}
+   \caption{Left: Example adapted from~\cite{Delerue:2016zgr} of the initial data recorded with the two SPESO detectors (Pink is the Q-band detector and blue is the Ka-band detector, see explanation in~\cite{Delerue:2016zgr}).  Right:  Example taken from~\cite{Delerue:2016zgr}  of raw signal collected with the the  Ka-band  detector while the detectors were moving vertically. The red line corresponds to the grating in the inserted position and the blue line to the grating in the retracted position (background). }
+   \label{fig:SPESO_first_data}
+%   \vspace*{-\baselineskip}
+\end{figure}
+
+
+
+
+\begin{figure}[htbp]
+%   \vspace*{-.5\baselineskip}
+   \centering
+       \hspace*{-1.5cm}\begin{tabular}{cc}
+   \includegraphics[height=45mm]{Advanced_diags/MOPMB002f6.eps} &
+   \includegraphics[height=45mm]{Advanced_diags/MOPMB002f7.eps}
+\end{tabular}   
+   \caption{Images taken from~\cite{Delerue:2016zgr}. Left: Distribution of the signal measured as function of the observation angle. The red dots correspond to the Ka band detector and the blue dots to the Q-band detector. The solid lines correspond to data points at frequencies within the sensitivity range of the detector and the dashed lines to data points at frequencies outside that range. These data are compared to simulations for 4 different bunch FWHM. Right: Bunch profile recovered from the data presented on the left using the method described in~\cite{reco_paper}.}
+   \label{fig:SPESO_signal_spectrum}
+%   \vspace*{-\baselineskip}
+\end{figure}
+
+The SPESO experiment has been upgraded in 2016 to study the polarisation of the Smith-Purcell radiation. The result has been presented in~\cite{Delerue:IPAC17-SOLEIL} and is shown in figure~\ref{fig:SPRESO_polarization_2017}. This result is a surprise to us as we expected almost 100\% polarization but it could be compatible with what was observed at FACET (see figure~\ref{fig:E203_polar}). The measurement campaign on SPESO is continuing to increase the range of the measurement.
+
+
+\begin{figure*}[!htb]
+%   \vspace*{-.5\baselineskip}
+   \centering
+   \includegraphics*[width=70mm]{Advanced_diags/MOPAB025f6.pdf}
+   \caption{Degree of polarisation as function of the longitudinal displacement (along the beam propagation axis). Image taken from~\cite{Delerue:IPAC17-SOLEIL}. }
+   \label{fig:SPRESO_polarization_2017}
+%   \vspace*{-\baselineskip}
+\end{figure*}
+
+
+\subsection{Coherent Smith-Purcell radiation measurement at CLIO.}
+\label{sec:CLIO}
+
+SPESO is meant to be a test bench to study the properties of Coherent Smith-Purcell Radiation. However to have this diagnostic accepted in control rooms, it is necessary to demonstrate that it can work as a control room tool and produce results quickly. This is the aim of the Smith-Purcell experiment at CLIO. CLIO (Acronym in french for Infrared Laser Center at Orsay - {\em Centre Laser Infrarouge à Orsay}) is a Free Electron Laser installed in Orsay. It has been described in~\cite{Ageron:1989eq,bourdon:in2p3-00020744,Glotin:1992aj}.
+
+Before installing the experiment we studied the  dynamics of the beam and the predicted signal~\cite{delerue:in2p3-01322166}. Example of expected signal are shown on figure~\ref{fig:CLIO_sp-normalised}. To avoid searching the signal for too long in case the pulse length was very different from the expectations we decided to first measure CTR and made a comparison of expected signal level for CTR and CSPR~\cite{delerue:in2p3-01322182}. On figure~\ref{fig:CLIO_CTR_CSPRr} the single electron yield and the predicted spectrum at CLIO are compared.
+Our conclusion was that using the CLIO parameters and with a beam-grating separation of \SI{3}{mm} we expect a signal (in the range 0.03-3 THz [ 0.1 - 10 mm]) of \SI{8.37e-7}{J} for CSPR and \SI{7.35e-08}{J} for CTR. This result was questioned by a few colleagues but finally accepted and confirmed by independent experimental verifications made at another facility by another group~\cite{PhysRevAccelBeams.20.024701}.
+
+
+\begin{figure}[!htb]
+  \centering
+       \hspace*{-0.05cm}\begin{tabular}{cc}
+    \includegraphics[width=0.45\linewidth]{Advanced_diags/MOPMB005f6.pdf} &
+  \includegraphics[width=0.45\linewidth]{Advanced_diags/MOPMB005f7.pdf}
+\end{tabular}   
+  
+  \caption{  Coherent Smith-Purcell spectrum as a function of the observation angle for different bunch profiles in CLIO. The grating used for these simulations has a pitch of 8~mm and a blaze angle of $30^o$. The left figure gives the energy distribution, the right figure is normalized so that the maximum amplitude of each line is 1. Image taken from~\cite{delerue:in2p3-01322166}.
+}
+  \label{fig:CLIO_sp-normalised}
+  \end{figure}
+
+\begin{figure}[htb]
+  \centering
+  \label{sey}
+\end{figure}
+
+\begin{figure}[!tbp]
+  \centering
+       \hspace*{-0.05cm}\begin{tabular}{cc}
+  \includegraphics[height=55mm]{Advanced_diags/MOPMB003f1.pdf} &
+  \includegraphics[height=55mm]{Advanced_diags/MOPMB003f9.pdf}
+  \end{tabular}   
+
+  \caption{Left: Single electron yield for transition radiation (TR) and Smith-Purcell radiation (SP). The screen diameter for transition radiation is \SI{40}{mm}. The SP  single electron yield is presented for different beam-grating separation (\SIlist{3;6;9}{mm}). The grating used here is   $40\times180$ \si{mm^2} with 8 mm pitch and $30^o$ blaze angle. The signal is measured as integrated with a \SI{50}{mm} diameter parabolic mirror located \SI{300}{mm} from the beam axis. Right:  CSPR and CTR energy density as function of wavelength with the same parameters than on the left figure. Both images are taken from~\cite{delerue:in2p3-01322166}.}
+  \label{fig:CLIO_CTR_CSPRr}
+\end{figure}
+
+After a first phase during which we measured CTR to validate the detection chain the experiment has quickly been upgraded with a grating instead of the CTR screen. Unlike the E-203 experiment we use single quartz window to let the radiation out. We also decided to use Off Axis Parabolic mirrors (OAP) instead of Winston cones to focus the radiation of the detectors. Photos of the experiment are shown on figure~\ref{fig:CLIO_expstp} and the experiment has been described in details in~\cite{Delerue:IPAC17-CLIO}.
+
+\begin{figure}
+  \centering
+       \hspace*{-0.05cm}\begin{tabular}{cc}
+  \includegraphics[height=55mm]{Advanced_diags/20170203_193939_resized.jpg} &
+  \includegraphics[height=55mm]{Advanced_diags/MOPAB026f1.jpg}
+    \end{tabular}   
+
+  \caption{The experimental setup for CSPR measurements at CLIO: a set of pyrodectors with off axis parabolic mirrors is placed equidistantly with \ang{7} separation around the window and the experimental chamber with the grating inside (right image taken from~\cite{Delerue:IPAC17-CLIO}). The two images have been taken at different dates and have a different number of detectors.}
+  \label{fig:CLIO_expstp}
+\end{figure}
+
+\begin{figure}[!htb]
+  \centering
+       \hspace*{-0.05cm}\begin{tabular}{cc}
+  \includegraphics[height=55mm]{Advanced_diags/MOPAB026f3.pdf} &
+  \includegraphics[height=55mm]{Advanced_diags/MOPAB026f6.pdf} 
+     \end{tabular}
+  \caption{Signal amplitude as function of the grating position with respect to the center of the beam for three different detectors angles for a long range (left) and a short range near the beam (right). On the right the data (circles) is compared to a fit (solid line). Images taken form~\cite{Delerue:IPAC17-CLIO}. On the left image the peak between \SI{20}{mm} and \SI{30}{mm} is still under investigations.}
+  \label{fig:CLIO_gscan}
+\end{figure}
+
+
+After the publication of~\cite{Delerue:IPAC17-CLIO} further work was done and has been reported in~\cite{rapport_vitalii_CLIO_2017}. The figure~\ref{fig:CLIO_form_factor} shows form factors that were measured on CLIO and figure~\ref{fig:CLIO_profile} shows the reconstructed profile.
+
+\begin{figure}[!htb]
+  \centering
+       \hspace*{-0.05cm}\begin{tabular}{cc}
+  \includegraphics[height=55mm]{Advanced_diags/FF.eps} &
+  \includegraphics[height=55mm]{Advanced_diags/FF6.eps} 
+     \end{tabular}
+  \caption{Form factor measured at CLIO as reported in~\cite{rapport_vitalii_CLIO_2017}. Left: Variation of the form factor when the beam grating separation varies. Right: Variation of the form factor when the buncher phase varies.
+    }
+  \label{fig:CLIO_form_factor}
+\end{figure}
+
+\begin{figure}[!htb]
+  \centering
+  \includegraphics[width=\linewidth]{Profile1.eps}
+  \caption{Bunche profile reconstructed on CLIO for different buncher phase as reported in~\cite{rapport_vitalii_CLIO_2017}.
+    }
+  \label{fig:CLIO_profile}
+\end{figure}
+
+We 
+
+
+
+Future plans
+
 
 
 \subsection{Outlook: Application to laser-driven plasma accelerators and ERLs}
 beam grating sep.
-stability
+beam stability
+shot to shot stability
+ESS