A final focus system for injection into a laser plasma accelerator at the ARES linac
Sumera Yamin, Ralph Assmann, Florian Burkart, Angel Ferren Pousa, Wolfgang Hillert, Francois Lemery, Barbara Marchetti, Eva Panofski
AA final focus system for injection into a laser plasma accelerator at the ARES linac
S. Yamin ∗ DESY, Notkestrasse 85, 22607 Hamburg, Germany. Also at University of Hamburg, 20148, Hamburg, Germany
R. Assmann, F. Burkart, A. Ferran Pousa, F. Lemery, B. Marchetti, and E. Panofski
DESY, Notkestrasse 85, 22607 Hamburg, Germany
W. Hillert
University of Hamburg, 20148, Hamburg, Germany (Dated: February 18, 2021)ARES (Accelerator Research Experiment at SINBAD) is a linear accelerator at the SINBAD(Short INnovative Bunches and Accelerators at DESY) facility at DESY. ARES was designed tocombine reproducible beams from conventional RF-based accelerator technology with novel butstill experimental acceleration techniques. It aims to produce high brightness ultra-short electronbunches in the range of sub fs to few fs, at a beam energy of 100-150 MeV, suitable for injection intonovel acceleration experiments like Dielectric Laser Acceleration (DLA) and Laser driven PlasmaAcceleration (LPA). This paper reports the conceptual design and simulations of a final focus systemfor injecting into a LPA experiment at ARES, including permanent magnetic quadrupoles (PMQ),sufficient longitudinal space for collinear laser and electron transport, space for required diagnosticsand a LPA setup. Space-charge effects play a significant role and are included. Simulation resultson the focusing of the ARES electron bunches into and their transport through the laser-drivenplasma are presented. The effects of several errors have been simulated and are reported.
I. INTRODUCTION
SINBAD acronym for Short INnovative Bunches andAccelerators at DESY, is an accelerator R&D facility atDESY on its Hamburg site [1]. It includes research in thefield of ultrashort electron bunches and will host multi-ple independent experiments [2] on laser driven advancedhigh gradient acceleration techniques such as DielectricLaser Acceleration (DLA) [3], Laser Plasma Accelera-tion (LPA) [4] and THz-driven acceleration in the AX-SIS project [5]. The ARES (Accelerator Research Ex-periment at SINBAD) linear accelerator (linac) at SIN-BAD is based on conventional S-band technology witha photo-injector gun [6][7]. It is designed to provideultrashort high brightness electron beams for injectioninto novel accelerators. The FWHM length of electronbunches is expected to reach a few fs and potentially subfs values. The electron gun relies on a conventional ra-dio frequency (RF) accelerator technology for producingthe electron bunches. This has several advantages. TheARES linac on one hand will allow advancing R&D onthe “conventional” production of high brightness ultra-short electron bunches. On the other hand, the well-characterized bunches can be used to explore compactnovel accelerators, characterized by accelerating fieldswith short wavelengths and therefore require the injec-tion of short “acceleration buckets”. The ARES buncheshave been designed to constitute excellent probes to mea-sure the energy gain and the quality of the acceleration.At ARES, the electron bunches can be compressed ei-ther via velocity bunching or by using a magnetic bunch ∗ [email protected] compressor or by using a hybrid scheme to achieve the de-sired bunch lengths in the range of sub fs to few fs [8][9].The characterization of such ultra-short bunches is a re-search field in itself and ARES will also serve as a testbench for novel diagnostic devices in the low to mediumcharge range of up to 30 pC and with sub-fs to few fsbunch length [10][11]. All these features contribute inmaking ARES a promising candidate where LPA exper-iments with external injection could be performed. Thispotential was explored as a part of a PhD project.LPAs can provide an accelerating gradient in the rangeof ≈
100 GV/m, which is several orders of magnitudehigher than what can be achieved with conventional RFtechnology. This reduces the size of the accelerationchannel from meters to millimeters, to achieve GeV en-ergy range, and hence offers the possibility of compactand cost-effective accelerators. In a LPA, strong laserpulses propagating in a plasma generate charge separa-tion through the excitation of wakefields, inducing strongelectric fields. Since the LPA concept was first introduced[12], it has been a subject of extensive studies with sig-nificant progress in recent years [13][14]. Many impor-tant milestones have been demonstrated such as achiev-ing GeV energies in only cm scale [15]. Today’s focusfor these devices is to reach beam stability, similar toestablished RF accelerators, by deploying feedback con-trol systems. Recently another milestone has been suc-cessfully demonstrated at DESY with 24 hours of stableoperation of laser plasma acceleration [16]. The externalinjection LPA experiment studied for ARES, investigateda possible step towards usable LPA from a combinationof reproducible conventional RF-based accelerator tech-nology with the high gradient fields from plasma wake-fields [17]. The RF-based technology allows for a precise a r X i v : . [ phy s i c s . acc - ph ] F e b manipulation of the phase space of the electron bunchesbefore entering the plasma hence, providing independentcontrol and quality adjustments as well as optimization ofthe plasma experiment. The beam quality in novel accel-erators depends on the detailed parameters and quality ofthe injected beam e.g. bunch shape, bunch length, emit-tance, arrival time stability and beam energy. ARES pro-vides the option of widely tunable working points (WP)and bunch shapes for external injection LPA acceleratorR&D. External injection of electron beam into an LPA,however, has its own technical challenges [7]. The syn-chronization of laser and electron beam can be the mostcrucial aspect of this experiment.The present status of ARES is shortly summarized. Its5 MeV RF gun and linac has been commissioned [18] andfirst electrons have been produced at the end of 2019 [19].The installation of the subsequent experimental chamberand diagnostic beam line is finished [19]. The prepara-tions for a DLA experiment are ongoing and simulationstudies have been performed for a potential LPA exper-iment [20]. In this paper, we present design studies fora final focus system that could fulfill the requirements ofexternal injection of ARES bunches into a LPA setup.In the following sections, the layout of the ARES linacand the experimental area for the simulated LPA ex-periment are described, followed by the requirements forbeam matching into the plasma cell. The results for de-sign and optimization of the final focus system and forelectron beam tracking through the lattice are presented.Tolerance studies for the final focus system are presentedand discussed. II. LAYOUT OF ARES LINAC
A schematic overview of the ARES linac with a po-tential LPA acceleration experiment is shown in Fig. 1.The main beam parameters are summarized in Table 1.The ARES linac consists of a 5 MeV RF gun followedby two travelling wave structures (TWS) with space re-served for a third travelling wave structure for a possiblefuture energy upgrade [7]. This space will be temporar-ily used as first experimental area (EA). This is followedby a matching section into a magnetic bunch compressor(BC). At the exit of the BC the electron bunches have aduration of a few fs or below [21]. The BC is followed bya drift space that provides space for the laser incoupling.Further downstream, we have a high energy diagnosticbeamline followed by the matching optics for the secondexperimental area. This area could host LPA experi-ment and could combine the electron beam from ARESwith high power laser pulses from the high repetitionhigh power laser KALDERA currently under construc-tion at DESY [22]. The matching scheme is designed forthe low charge WP of the ARES linac that will provide0.8 pC electron bunches with smallest arrival time jitterof about ≈
10 fs rms. It uses a pure magnetic compres-sion scheme and is designed for ultimately sub fs bunch
TABLE I. Parameters for the RF systems and the electronbeam at the ARES linac
Parameter Values
RF Frequency 2.998 GHzRepetition rate 50 HzBeam Energy 100 MeV (155 MeV on crest)Upgraded beam energy 150 MeV (230 MeV on crest)Bunch Charge 0.5-30 pCBunch Length sub to few fsArrival Time Jitter stability 10fs to few tens of fs length. The WP has been discussed in detail in [23]. Theelectron bunches from this setup provide a time resolu-tion in sub fs range and can serve as probe particles forplasma wakefields or fields in dielectric structures.In this paper, we present the results for the highercharge 10 pC WP of the ARES linac. It features a longerbunch length of 10 fs FWHM or 4.3 fs rms. The peakcurrent in this case is 1 kA, approaching the requirementsof several use cases [24]. It is noted that this WP issimilar to a WP studied at the BELLA facility in LBNLfor which a broad energy spread electron bunch of ≈ III. TECHNICAL CONSTRAINTS FOR THEMATCHING BEAM LINE
In the external injection LPA experiment, the laserbeam and the electron beam are collinearly injected intothe plasma channel. The collinear electron and laserbeam lines, along with required beam diagnostic ele-ments, introduce strict constraints on both the transverseand longitudinal dimensions for the design of the final fo-cusing system. The system must be compact and mustprovide gradients high enough to tightly focus the beaminto the plasma cell. Those constraints led to choosing aPMQ triplet as final focusing system.The key parameters for the laser system are presentedin table II. The schematic of the laser beam at its waistand the parameter definitions are shown in Fig. 2. Forthis study a Gaussian laser beam is assumed. Since thedivergence of the laser beam depends on the beam waistw o , the design of the laser beamline and hence in turn thespace constraints for our final focus system are stronglydependent on the laser parameters. TABLE II. Key parameters for the Laser setup
Parameters Units Values
Wavelength λ o µ m 0.8Vector potential a o w o µ m 42.4Pulse Energy (E) J 3Peak Power (P) TW ∼ FWHM ) fs 30
FIG. 1. Schematic of ARES
The technical design considerations for the PMQtriplet have been discussed in detail in [26]. The requiredmirror is housed in a beam pipe having diameter of 10 cm.The beam pipe size is chosen to accommodate the mirrordimensions required for focusing the 100 TW peak powerlaser beam. A hole in the mirror allows the electron beamtransmission and, collinearly to the laser beam, the elec-tron beam enters the plasma cell. At the focal point,the laser beam has a design waist of 42.4 µ m. For theexternal injection experiment, the laser beam also has topass through the PMQ triplet to reach the plasma cell.Hence the free aperture, defined by the distance of themagnetic pole tips of the PMQ should be bigger than thelaser spot size at the position of quadrupoles. Consider-ing the laser beam evolution from Fig. 2, the apertureof PMQ is chosen to be 10 mm. The laser parametersand the laser beam line design dictate the limits for thephysical dimensions of the PMQ inner and outer radii,the length of the total triplet and also set constraints tothe positions of the focusing magnet. The distance be-tween the exit of the BC and the entrance of the plasmacell is ≈ o , the design of the laser beamline andhence in turn space constraints for our final focus systemhave a strong dependence on the laser parameters. IV. MATCHING CRITERION
For preserving the beam emittance, it is required tomatch the externally injected electron beam to the fo-cusing fields of the plasma accelerator. The matching
FIG. 2. Evolution of the laser beam along the direction ofbeam propagation. The origin here is set at the focal point ofthe laser beam which is the entrance position of the plasmacell. A Gaussian laser beam is assumed. conditions depend on the focusing strength of the plasmachannel, essentially given by the plasma density [27]. Forthe LPA experiment studied, the matched Twiss param-eter is β x,y ≈ cm − . This requirement was relaxed byproper shaping of the longitudinal plasma density profile(upramps) as discussed in [28] and [29]. The longitudinalplasma density profile given by Eq. 1 was implemented tomatch the electron beam into the plasma focusing fieldand thus to control the emittance growth of the beam inthe plasma section: n p,r = n p,o (cid:16) zL r (cid:17) (1)where n p,r is the plasma density, n p,o is the density ofthe plateau, z is the distance to the plateau and L r is thelength parameter which determines how fast the densitydecreases with z. Such a ramp has been found to havegood performance as illustrated in [28]. The optimiza-tion of the plasma ramps was done via FBPIC simula-tion scans in which different values for L r were simulatedand optimized. For the present case, L r = 2 mm wasused. The calculation of the necessary Twiss parametersat the plasma entrance were obtained by back-trackinga matched beam at the plateau entrance, through theramp. The back-tracking in this case implies that thebeam was propagated through a downramp identical tothe upramp. The approach was to calculate the betafunction needed at the beginning of the plateau using thefocusing fields there. Then a Gaussian bunch was gen-erated with this beta and alpha = 0 and then tracked,including the laser driver, through a plasma down rampwhich has the same shape as the up ramp. This is equiv-alent to back propagating the bunch through the plasma.A similar approach has been used in [30]. The requiredmatched twiss parameters for a laser spot size of 40 µ mare then β x,y = 11.8 cm and α x,y = 4.4. Through-out the article, the entrance of plasma cell refers to thestart of plasma ramps for which this matching criterionis defined. V. DESIGN STUDY FOR THE MATCHINGBEAMLINE
The beam dynamics simulations for the matchingbeamline after the BC have been performed using Elegant(without space charge) [31] and then ASTRA [32] to opti-mize and include the effects of 3D space charge (SC). Theoptimization parameters for the PMQ triplet are lengths,strengths and distances between the quadrupoles. Basedon the laser beamline layout, as shown in Fig. 2, the con-straints for the final focus system were the quadrupoleaperture, the outer diameter corresponding to size of thequadrupoles and the focal length. The focal length musttake into account space for diagnostic screens allowinglaser and electron beam profiling between the last mag-net of the triplet and the plasma cell. We set the originof our simulations at the exit of the last magnet of theBC and the beamline is simulated from this point untilthe entrance of the plasma cell corresponding to the startof plasma upramp as defined by the matching criterionin Section IV.The key parameters for the working points at the BCexit and at the entrance of the plasma cell are summa- rized in Table III. The full beam distribution is includedin the calculation of statistical parameters. The threequadrupoles of the triplet have lengths of 0.055 m, 0.033m and 0.040 m with strengths of 50 m -2 , -180 m -2 and130 m -2 respectively. The distance between the last mag-net and the plasma cell is 0.25 m which is sufficient toplace screens for laser and electron beam profiling. Fig. 3shows the evolution of the electron beam parameters overthe drift space and through the PMQ triplet from theBC to the plasma cell. The transverse and longitudinalphase spaces of the electron beam at the BC exit and atthe entrance of plasma cell are shown in Fig. 4. FromFig. 3 and 4 it is evident that at the start of plasmaramp, the electron beam is well matched with preservedtransverse emittance and bunch length shorter than theaccelerating wavelength in the plasma. The transversephase space distributions show that the beam is sym-metric in both planes as required by LPA. The PMQtriplet also ensures to maintain the current profile fromthe longitudinal phase space with ≈ TABLE III. Bunch Parameters at the BC exit (I) and ofmatched beam at the entrance of plasma cell (II)
Parameters I II
Energy (MeV) 150 150Bunch Charge (pC) 10 10Bunch length FWHM/rms (fs) 11.8/4.38 11.9/4.30 ε x ( π .mm.mrad) 0.59 0.57 ε y ( π .mm.mrad) 0.29 0.31 β x (cm) 15.3e2 11.8 β y (cm) 47.22e2 11.9 α x -1.7 4.5 α y -1.7 4.4 σ x σ y VI. ERROR ANALYSIS OF THE PMQ TRIPLETAND THE INCOMING BEAM
The experimental conditions may vary from the idealdesign parameters discussed in the previous sections dueto temporal and spatial jitter in the beam. Moreover,there are additional sources of errors in the quadrupoles,arising during the manufacturing and installation of the
FIG. 3. Evolution of the electron beam parameters along the beam line from the exit of the BC until the entrance of theplasma cell. The origin here is set at the exit of the last magnet of the BC. The parameters shown are the Twiss parametersin (a) β x,y and in (b) α x,y , in (c) the normalized transverse emittance ε x,y , in (d) the rms transverse beam sizes σ x,y , in (e)the energy spread σ E and in (f) the bunch length σ z FIG. 4. Evolution of the transverse and longitudinal phase spaces at (a) the BC exit and matched beam at (b) the entrance ofthe plasma cell. Color scales indicate normalized electron density. final focus system. For example, offsets between the mag-netic field center of the quadrupoles and the ideal beam-line can lead to emittance growth and betatron oscilla-tions in the plasma. A basic tolerance study for the finalfocus system was performed to estimate the effects ofseveral error sources.We consider two sources of errors in our system. Oneset of errors can arise from spatial and temporal jitterin the electron beam. The other set of errors is intro-duced from positioning errors in the quadrupole triplet.In simulation parameters in the beam distribution afterthe bunch compressor were varied and analyzed. In addi-tion, perturbations from transverse offsets x off and y off inthe quadrupole triplets, from rotation errors x rot in thex-z plane, from rotation errors y rot in the y-z plane, fromrotation errors z rot in the x-y plane, from longitudinal off-set errors z off and from errors in the focusing strength Kwere included. The quadrupole parameters under studywere varied according to Eq. 2 A = A ref ± A off ( ± tol ) (2)where A represents an input parameter, A ref is thedesign parameter of the quadrupole and A off ( ± tol) isthe variation of the design parameter within the giventolerances range. All quadrupoles were assigned the sameerror as one would realistically expect if errors arise froma common power supply or a common support girder. Forexample, mounting errors between single elements on acommon girder are usually much better corrected thanoffsets or drifts of the whole girder in the tunnel.For the tolerance studies for jitter in the input beam,the beam properties were perturbed according to Eq. 3.Included were transverse offsets in electron bunch posi-tion in both transverse planes (x and y), errors in bunchsize in both transverse planes, the beam momentum anddivergence, bunch charge, bunch length as well as longi-tudinal offset in z, all defined at the exit of the bunchcompressor: ∆ b i = b i,ref ± b off ( ± tol ) (3)where b i,ref is the reference beam parameter at the exitof BC given in Table III and b off is the error in the beamparameter at the same location.The observables in simulation include transverse nor-malized emittance, transverse beam sizes, beam diver-gence in both planes, Twiss parameters, bunch lengthand energy spread at the entrance of the plasma cell.In order to assess the robustness of the PMQ tripletsolution, 10,000 cases were simulated for two cases.Mismatch case 1: Errors are randomly assigned. Thisincludes ± µ m errors in bunch position at the BC exitand 10% errors in beam size, bunch length and bunchcharge. For the quadrupole triplet transverse and lon-gitudinal offsets were varied within ± µ m, rotationaloffsets within ± µ rad and the strength were varied by ±
10% of the design value. The minimum tolerancerange of 10 ± m was chosen according to the precisionrange of hexapods which can be used for the positioningof the quadrupole triplet [33].Mismatch case 2: A same set of simulations were car-ried out in which the tolerance range for transverse androtational offset of quadrupole was 100 µ m and 100 µ radrespectively.The position for observing the final beam parametersin both cases was fixed at the matched case position ofTable III, which is the entrance of plasma cell as ex-plained in section IV. Fig. 5 summarizes the simulatedbeam parameters at the plasma entrance, as obtained inthe two error cases. From Fig. 5, it can be concluded thatthe mismatch case 1 is an acceptable scenario, since thebeam with this set of variations still enters the plasma cellwell matched in the transverse plane with only a smallincrease in emittance. It is worthwhile to note again thatthis also includes the variation in input beam parameters.It can be safely inferred that the PMQ triplet design isrobust and can be used for matching the electron beamto the plasma channel under less than ideal experimentalconditions as well. VII. SIMULATED ACCELERATION THROUGHA PLASMA CELL
The simulated beam matched to the plasma entrance(reference case from Section V) was further trackedthrough a laser-driven plasma cell (LPA) using theFBPIC code [34]. A plasma cell model, with density of10 cm − is used to accelerate the beam. Fig. 7 showsthe simulated beam evolution through the plasma cell.The density profile and the evolution of the Twiss param-eter β x , the normalized emittance ε x , the beam energyand the energy spread σ E are shown. Fig. 6(a) showsthe simulated transverse and longitudinal phase spacesafter the beam has been accelerated through the LPA.It is seen that we obtain an emittance of around 0.5 µ mwith a final beam energy of 1 GeV. A three-sigma cutwas applied in the determination of the various observ-ables, leading to 1% of the total number of particles beingcut (particles far out in the tail would otherwise bias thecalculated observables).Achieving emittance preservation and a small energyspread is essential for a usable beam quality from a LPA.The slice energy spread for the beam after the plasma cellis very good and amounts to 0.3% in our case which isstill on the high side compared to facilities like FLASH[35]. However, for applications such as FEL, large en-ergy spread can be tolerated by reducing the slice en-ergy spread by means of bunch decompression as demon-strated in [36]. Recently, a scheme has been proposed todiminish the energy spread by using a chicane betweentwo plasma stages [24].A perturbed beam, according to mismatch case 1 ofFig. 5, was also simulated through the plasma cell. In FIG. 5. Variation in observed beam parameters at the plasma entrance for the two error scenarios defined in the text (mismatchcase 1 and 2) and each 10,000 random cases simulated
FIG. 6. Simulated evolution of beam parameters through aLPA plasma cell in the ARES linac for the matched beam andthe mismatched beam considered in this study n p [ c m ] x [ m ] matched casemismatched case n , x [ m ] E n e r g y [ M e V ] E [ % ] FIG. 7. Simulated evolution of beam parameters through aLPA plasma cell in the ARES linac for the matched beam andthe mismatched beam considered in this study this mismatch case, the offsets were introduced in thebeam parameters at the exit of BC as well as in thequadrupole triplet. Fig. 7 shows the beam evolution ofthe mismatched beam in comparison to the matched case.In both cases, the slice emittance is still below 0.5 µ m asshown in Fig. 6. From Fig. 7 and 6, it is seen that theproposed tolerances in the mismatch case 1 are sufficientto match the electron beam coming from the chicane tothe plasma cell and to transport it with somewhat dete-riorated but still good quality through a LPA. VIII. CONCLUSION
The design for a final focus system, an experimentalbeamline and a LPA with external injection has beendeveloped for the ARES linac in the SINBAD facil-ity at DESY. Detailed numerical simulations show thatthe electron beam can be transported and focused toa plasma cell. The studies include the effects of spacecharge. The electron beam has adequate transverse sym-metry and is well matched into a plasma channel withplasma ramps. The longitudinal phase space is preservedwith a 1 kA peak current, as approaching the require-ments for several use cases. We have performed a sensi-tivity analysis of the PMQ triplet for understanding thetolerances and to mitigate the effect of imperfections ofthe final focus system. The performed error analysis,which is specific to the system under study but could begeneralised for any quadrupole triplet, gives a useful es-timate about the performance of the final focus systemand suggests critical parameters in the implementationof the experiment. A plasma simulation shows that ex-ternal injection of short electron bunches into a LPA atARES can achieve high beam quality and can constitutea stepping stone towards a staged multi GeV high per-formance plasma accelerator.
ACKNOWLEDGMENTS
The authors acknowledge valuable discussions with K.Floettmann, D. Marx, F. Mayet and F. Jafarinia. Specialthanks to W. Leemans for his support and discussion.The authors would also like to acknowledge the FBPICdevelopers and contributors. [1] R. Aßmann, C. Behrens, R. Brinkmann, U. Dorda,K. Fl¨ottmann, B. Foster, J. Grebenyuk, M. Gross,I. Hartl, M. H¨uning, F. K¨artner, B. Marchetti,Y. Nie, J. Osterhoff, A. R¨uhl, H. Schlarb, B. Schmidt,F. Stephan, A. M¨uller, M. Schuh, F. Gr¨uner, B. Hid-ding, A. R. Maier, and B. Zeitler, SINBAD - AProposal for a Dedicated Accelerator Research Fa-cility at DESY, in
Proc. 5th International Parti-cle Accelerator Conference (IPAC’14), Dresden, Ger-many, June 15-20, 2014 , International Particle Accel-erator Conference No. 5 (JACoW, Geneva, Switzerland, 2014) pp. 1466–1469, https://doi.org/10.18429/JACoW-IPAC2014-TUPME047.[2] U. Dorda, B. Marchetti, J. Zhu, F. Mayet, W. Kuropka,T. Vinatier, G. Vaschenko, K. Galaydych, P. A. Walker,D. Marx, R. Brinkmann, R. Assmann, N. H. Matlis,A. Fallahi, and F. X. Kaertner, Status and objectivesof the dedicated accelerator r & d facility sinbad at desy,Nuclear Inst. and Methods in Physics Research, A ,239 (2018).[3] F. Mayet, R. Assmann, J. B¨odewadt, R. Brinkmann,U. Dorda, W. Kuropka, C. Lechner, B. Marchetti, and
J. Zhu, Simulations and Plans for Possible DLA Experi-ments at SINBAD, Nuclear Inst. and Methods in PhysicsResearch, A , 1 (2018).[4] B. Marchetti, R. Assmann, U. Dorda, and J. Zhu, Con-ceptual and Technical Design Aspects of Accelerators forExternal Injection in LWFA, Applied Sciences ,1 (2018).[5] F. K¨artner, F. Ahr, A.-L. Calendron, H. C¸ ankaya,S. Carbajo, G. Chang, G. Cirmi, K. D¨orner, U. Dorda,A. Fallahi, A. Hartin, M. Hemmer, R. Hobbs, Y. Hua,W. Huang, R. Letrun, N. Matlis, V. Mazalova, O. M¨ucke,E. Nanni, W. Putnam, K. Ravi, F. Reichert, I. Sarrou,X. Wu, A. Yahaghi, H. Ye, L. Zapata, D. Zhang, C. Zhou,R. Miller, K. Berggren, H. Graafsma, A. Meents, R. Ass-mann, H. Chapman, and P. Fromme, Axsis: Explor-ing the frontiers in attosecond x-ray science, imagingand spectroscopy, Nuclear Instruments and Methods inPhysics Research Section A: Accelerators, Spectrometers,Detectors and Associated Equipment , 24 (2016),2nd European Advanced Accelerator Concepts Workshop- EAAC 2015.[6] E. Panofski et al. , Status Report of the SINBAD-ARES RF Photoinjector and LINAC Commission-ing, in
Proc. 10th International Particle AcceleratorConference (IPAC’19), Melbourne, Australia, 19-24May 2019 , International Particle Accelerator Confer-ence No. 10 (JACoW Publishing, Geneva, Switzerland,2019) pp. 906–909, https://doi.org/10.18429/JACoW-IPAC2019-MOPTS026.[7] B. Marchetti, R. Assmann, R. Brinkmann, F. Burkart,U. Dorda, K. Floettmann, I. Hartl, W. Hillert, M. Huen-ing, F. Jafarinia, S. Jaster-Merz, M. Kellermeier,W. Kuropka, F. Lemery, D. Marx, F. Mayet, E. Panof-ski, S. Pfeiffer, H. Schlarb, T. Vinatier, P. A. Walker,L. Winkelmann, and S. Yamin, SINBAD-ARES - aphoto-injector for external injection experiments in novelaccelerators at DESY, Journal of Physics: Conference Se-ries , 012036 (2020).[8] B. Marchetti, R. Assmann, U. Dorda, J. Grebenyuk, andJ. Zhu, Compression of an Electron-Bunch by Means ofVelocity Bunching at ARES, in
Proc. of InternationalParticle Accelerator Conference (IPAC’15), Richmond,USA, 3-8 May, 2015 (JACoW, Geneva, Switzerland,2015) pp. 1472–1475.[9] J. Zhu, R. W. Assmann, M. Dohlus, U. Dorda, andB. Marchetti, Sub-fs electron bunch generation with sub-10-fs bunch arrival-time jitter via bunch slicing in amagnetic chicane, Phys. Rev. Accel. Beams , 054401(2016).[10] S. Jaster-Merz, R. W. Assmann, F. Burkart, U. Dorda,J. Dreyling-Eschweiler, L. Huth, U. Kr¨amer, andM. Stanitzki, Development of a beam profile monitorbased on silicon strip sensors for low-charge electronbeams, Journal of Physics: Conference Series ,012047 (2020).[11] D. Marx, R. W. Assmann, P. Craievich, K. Floettmann,A. Grudiev, and B. Marchetti, Simulation Studies forCharacterizing Ultrashort Bunches Using Novel Polariz-able X-band Transverse Deflection Structures, ScientificReports , 1 (2019).[12] T. Tajima and J. M. Dawson, Laser electron accelerator,Phys. Rev. Lett. , 267 (1979).[13] W. P. Leemans, B. Nagler, A. J. Gonsalves, C. Toth,K. Nakaruma, C. G. R. Geddes, E. Esarey, C. B. Schroeder, and S. M. Hooker, GeV electron beams froma centimetre-scale accelerator, Nature Physics , 3909(2006).[14] M. Litos, E. Adli, J. M. Allen, W. An, C. I. Clarke,S. Corde, C. E. Clayton, J. Frederico, S. J. Gessner, S. Z.Green, M. J. Hogan, C. Joshi, W. Lu, K. A. Marsh, W. B.Mori, M. Schmeltz, N. Vafaei-Najafabadi, and V. Yaki-menko, 9 gev energy gain in a beam-driven plasma wake-field accelerator, Plasma Physics and Controlled Fusion , 034017 (2016).[15] A. J. Gonsalves, K. Nakaruma, J. Daniels, C. Benedetti,C. Pieronek, T. C. H. Raadt, S. Steinke, J. H. Bin, S. S.Bulanov, J. V. Tilborg, C. G. R. Geddes, C. B. Schroeder,C. Toth, E. Esarey, K. Swanson, L. Fan-Chiang, G. Bag-dasarov, N. Bobrova, V. Gasilov, G. Korn, P. Sasorov,and W. P. Leemans, Petawatt Laser Guiding and Elec-tron Beam Acceleration to 8 GeV in a Laser-HeatedCapillary Discharge Waveguide, Physical Review Letters , 1 (2019).[16] A. R. Maier, N. M. Delbos, T. Eichner, L. H¨ubner,S. Jalas, L. Jeppe, S. W. Jolly, M. Kirchen, V. Ler-oux, P. Messner, M. Schnepp, M. Trunk, P. A. Walker,C. Werle, and P. Winkler, Decoding sources of energyvariability in a laser-plasma accelerator, Phys. Rev. X , 031039 (2020).[17] J. Grebenyuk, R. W. Assmann, U. Dorda, andB. Marchetti, Laser-Driven Acceleration with ExternalInjection at SINBAD, in Proc. of International ParticleAccelerator Conference (IPAC’14), Dresden, Germany,15-20 June, 2014 (JACoW, Geneva, Switzerland, 2014)pp. 1515–1518.[18] B. Marchetti, R. W. Assmann, S. Baark, F. Burkart,U. Dorda, K. Floettmann, I. Hartl, J. Hauser, J. Her-rmann, M. Huening, L. Knebel, O. Krebs, G. Kube,W. Kuropka, S. Lederer, F. Lemery, F. Ludwig, D. Marx,F. Mayet, M. Pelzer, I. Peperkorn, F. Poblotzki,S. Pumpe, J. Rothenburg, H. Schlarb, M. Titberidze,G. Vashchenko, T. Vinatier, P. A. Walker, L. Winkel-mann, K. Wittenburg, S. Yamin, and J. Zhu, Statusof the ARES RF Gun at SINBAD: From its Char-acterization and Installation towards Commissioning,in
Proc. 9th International Particle Accelerator Confer-ence (IPAC’18), Vancouver, BC, Canada, April 29-May 4, 2018 , International Particle Accelerator Confer-ence No. 9 (JACoW Publishing, Geneva, Switzerland,2018) pp. 1474–1476, https://doi.org/10.18429/JACoW-IPAC2018-TUPMF086.[19] F. Burkart, R.W.Assmann, U. Dorda, J. Hauser,B. Marchetti, W. Kuropka, S. lederer, F. lemery,F. Mayet, E. Panofski, and P. Wiesener, The Ex-perimental Area at the ARES LINAC, in
Proc.10th International Particle Accelerator Conference(IPAC’19), Melbourne, Australia, 19-24 May 2019 ,International Particle Accelerator Conference No. 10(JACoW Publishing, Geneva, Switzerland, 2019) pp.867–870, https://doi.org/10.18429/JACoW-IPAC2019-MOPTS014.[20] E. Svystun, R. Aßmann, U. Dorda, B. Marchetti,and A. M. de la Ossa, Numerical Studies on ElectronBeam Quality Optimization in a Laser-Driven PlasmaAccelerator with External Injection at SINBAD forATHENAe, in
Proc. 10th International Particle Accel-erator Conference (IPAC’19), Melbourne, Australia, 19-24 May 2019 , International Particle Accelerator Confer- ence No. 10 (JACoW Publishing, Geneva, Switzerland,2019) pp. 3628–3631, https://doi.org/10.18429/JACoW-IPAC2019-THPGW023.[21] F. Lemery, R. W. Assmann, U. Dorda, K. Flotte-mann, J. Hauser, M. Huning, G. Kube, M. Lantschner,S. lederer, B. Marchetti, N. Mildner, M. Pelzer,M. Rosan, J. Tiesses, and K. Wittenburg, Overviewof the ARES Bunch Compressor at SINBAD, in Proc. 10th International Particle Accelerator Confer-ence (IPAC’19), Melbourne, Australia, 19-24 May2019 , International Particle Accelerator ConferenceNo. 10 (JACoW Publishing, Geneva, Switzerland,2019) pp. 902–905, https://doi.org/10.18429/JACoW-IPAC2019-MOPTS025.[22] W. Leemans, High average power laser plasma accelera-tor project at desy (2019), european Advanced Acceler-ator Conference.[23] S. Yamin, R. W. Assmann, U. Dorda, F. Lemery,B. Marchetti, E. Panofski, and P. A. Walker, Design con-siderations for permanent magnetic quadrupole tripletfor matching into laser driven wake field acceleration ex-periment at SINBAD, Journal of Physics: ConferenceSeries , 012010 (2020).[24] A. Ferran Pousa, A. Martinez de la Ossa, R. Brinkmann,and R. W. Assmann, Compact multistage plasma-basedaccelerator design for correlated energy spread compen-sation, Phys. Rev. Lett. , 054801 (2019).[25] J. van Tilborg, S. K. Barber, F. Isono, C. B.Schroeder, E. Esarey, and W. P. Leemans, Free-electron lasers driven by laser plasma accelerators,AIP Conference Proceedings , 020002 (2017),https://aip.scitation.org/doi/pdf/10.1063/1.4975838.[26] S. Yamin, R.W.Assmann, U. Dorda, F. Lemery,B. Marchetti, E. Panofski, and P. Walker, Design Con-siderations for Permenant Magnetic Quadrupole Tripletfor Matching Into Laser Driven Wake Field Accel-eration Experiment at SINBAD, in
Proc. 10th In-ternational Particle Accelerator Conference (IPAC’19), Melbourne, Australia, 19-24 May 2019 , Interna-tional Particle Accelerator Conference No. 10 (JA-CoW Publishing, Geneva, Switzerland, 2019) pp.143–146, https://doi.org/10.18429/JACoW-IPAC2019-MOPGW027.[27] X. Li, A. Chanc´e, and P. A. P. Nghiem, Preserving emit-tance by matching out and matching in plasma wakefieldacceleration stage, Phys. Rev. Accel. Beams , 021304(2019).[28] X. L. Xu, J. F. Hua, Y. P. Wu, C. J. Zhang, F. Li,Y. Wan, C.-H. Pai, W. Lu, W. An, P. Yu, M. J. Hogan,C. Joshi, and W. B. Mori, Physics of phase space match-ing for staging plasma and traditional accelerator compo-nents using longitudinally tailored plasma profiles, Phys.Rev. Lett. , 124801 (2016).[29] K. Floettmann, Adiabatic matching section for plasmaaccelerated beams, Phys. Rev. ST Accel. Beams ,054402 (2014).[30] I. Dornmair, K. Floettmann, and A. R. Maier, Emittanceconservation by tailored focusing profiles in a plasma ac-celerator, Phys. Rev. ST Accel. Beams , 041302 (2015).[31] M. Borland, elegant: A Flexible SDDS-Compliant Codefor Accelerator Simulation, APS LS-287, September2000, .[32] K. Floettmann, ASTRA - A Space Charge Tracking Al-gorithm, , .[33] Smaact hexapods, .[34] R. Lehe, M. Kirchen, I. A. Andriyash, B. B. Godfrey, andJ. L. Vay, A spectral, quasi-cylindrical and dispersion-free particle-in-cell algorithm, Computer Physics Com-munications , 10.1016/j.cpc.2016.02.007 (2016).[35] Flash accelerator at DESY, https://flash.desy.de/accelerator/ .[36] A. R. Maier, A. Meseck, S. Reiche, C. B. Schroeder,T. Seggebrock, and F. Gruner, Demonstration schemefor a laser plasma driven free electron laser, Phys. Rev.X2