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A new generation of high-gradient normal conducting 1.3 GHz RF gun with 1% duty factor was developed to provide a high-quality electron source for superconducting linac driven free-electron lasers like FLASH and European XFEL. Compared to the Gun4 series, Gun5 aims for a ~50% longer RF pulse length (RF pulse duration of up to 1 ms at 10 Hz repetition rate) combined with high gradients (up to ~60 MV/m at the cathode). In addition to the improved cell geometry and cooling concept, the new cavity is equipped with an RF probe to measure and control the amplitude and phase of the RF field inside the gun. The first characterization of Gun5.1 included measurements of RF amplitude and phase stability (pulse-to-pulse and along 1 ms RF pulse). The dark current was measured at various peak power levels. The results of this characterization will be reported.

The Photo Injector Test Facility at DESY in Zeuthen (PITZ) develops a prototype of an accelerator-based high-power tunable THz source for pump-probe experiments at the European XFEL. The PITZ injector is also the site for the development and preparation of the high-brightness electron source for the main linac of the European XFEL and has the same pulse train structure as the X-ray photon source of the XFEL. For the proof-of-principle experiments on high-power THz generation an LCLS- I undulator (on loan from SLAC) is installed in the tunnel annex downstream of the existing accelerator. The extension of the beam line consists of a bunch compressor and a collimation system in the main PITZ tunnel, as well as a matching section, the undulator and the THz diagnostic setup in the tunnel annex. A Self-Amplified Spontaneous Emission (SASE) FEL is used to generate the THz pulses. High radiation power can be achieved by utilizing high charge (up to several nC) electron bunches from the PITZ photo injector. A beam energy of ~17 MeV is used to generate THz radiation with a centre wavelength of 100 μm. The transport of this space charge dominated electron beam and its thorough matching into the planar LCLS-I undulator with a strong vertical focusing is one of the project challenges. The installation of the first THz beamline setup was finished in summer 2022 and com-missioning with electron beam started. A specially developed procedure for a high charge beam matching into the undulator was successfully tested resulting in a first THz pulse generation. The start-up THz diagnostics is based on pyrodetectors. First measurements of the THz generation from 1,2 and 3 nC bunches have been taken, the statistics properties analysis corresponds to the expected SASE performance. The gain curve for the 3 nC case reflects the onset of saturation regime.

Research and development of an accelerator-based THz source prototype for pump-probe experiments at the European XFEL are ongoing at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). A proof-of-principle experiment to generate THz SASE FEL radiation using an LCLS-I undulator driven by an electron bunch from the PITZ accelerator has been prepared. After four years of designs and construction, the first commissioning with an electron beam was started in July 2022. This paper presents and discusses the experience and results of the first commissioning.

Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK 31st Linear Accelerator Conference, LINAC22, Liverpool, United Kingdom, 28 Aug 2022 - 2 Sep 2022; JACoW Publishing, Geneva, Switzerland 699-702 (2022). doi:10.18429/JACoW-LINAC2022-THPOJO03, A new generation of normal conducting 1.3GHz RF gun was developed to provide a high-quality electron source for superconducting linac driven free-electron lasers like FLASH and European XFEL. Compared to the Gun4 series, Gun5 aims for a 50% increase of the duration of the RF pulse (up to 1 ms at 10 Hz repetition rate) combined with high gradients (up to ~60 MV/m at the cathode). In addition to the improved impedance, the new cavity is equipped with an RF probe to measure and control the amplitude and phase of the RF field inside the gun. The first prototype of the new RF gun was manufactured at DESY and installed at the Photo Injector Test facility at DESY in Zeuthen (PITZ) in October 2021. In mid-October 2021 the RF conditioning began, aiming for achieving the aforementioned RF parameters. The conditioning procedure involves a slow gradual increase in repetition rate, RF pulse duration and peak power while carefully monitoring vacuum conditions and signals from interlock sensors. The results of RF conditioning will be reported., Published by JACoW Publishing, Geneva, Switzerland

Proceedings of the 11th International Beam Instrumentation Conference, IBIC2022, Kraków, Poland 11th International Beam Instrumentation Conference, IBIC2022, Krakow, Poland, 12 Sep 2022 - 15 Sep 2022; [Geneva, Switzerland] : JACoW Publishing 273-276 (2022). doi:10.18429/JACoW-IBIC2022-TUP20, The Photo Injector Test Facility at DESY in Zeuthen (PITZ) characterizes and optimizes electron sources for use at FLASH and European XFEL. AT PITZ, the transverse phase space is measured using a single slit scan and scintillator screen method. With the trend in photoinjectors towards lower current and emittance, these measurements become increasingly influenced by systematic errors including camera resolution and scintillator response due to smaller spot sizes. This study investigates the effects and corrections of the systematic errors for phase space measurements at PITZ., Published by JACoW Publishing, [Geneva, Switzerland]

Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand 13th International Particle Accelerator Conference, IPAC'22, Bangkok, Thailand, 12 Jun 2022 - 17 Jun 2022; JACoW Publishing, Geneva, Switzerland 310-312 (2022). doi:10.18429/JACOW-IPAC2022-MOPOPT029, The longitudinal phase space characteristics of space-charge dominated electron beams are keys to achieving bunch compression for the accelerator-based THz source at the Photo Injector Test facility at DESY in Zeuthen (PITZ). Such a THz source is proposed as a prototype for an accelerator-based THz source for pump-probe experiments at the European XFEL. A start-to-end simulation has suggested the settings of the phase of booster linear accelerator manipulating longitudinal beam characteristics to optimize the performance of the THz FEL. Although beam diagnostics after compression at PITZ are limited, the longitudinal beam characteristics as a function of the booster phase have been measured and compared with the corresponding simulations. The benchmark involves measurements of longitudinal phase space distribution for bunch charges up to 2 nC. The measurement technique assigned uses 50-um slits to achieve higher momentum and time resolution (1.8 keV/c and 0.5 ps, respectively)., Published by JACoW Publishing, Geneva, Switzerland

[Ebook] IBIC 2022, International Beam Instrumentation Conference : 11-15 September 2022, Krakow, Poland : IBIC2022 - proceedings / Organizers: GSI [Helmholtzzentrum für Schwerionenforschung]; SOLARIS, National Synchrotron Radiation Centre, Jagiellonian University in Krakow , [Geneva, Switzerland] : JACoW Publishing, [2022], 11th International Beam Instrumentation Conference, IBIC 2022, Cracow, Poland, 11 Sep 2022 - 15 Sep 2022; Geneva, Switzerland : JACoW Publishing 105-108 (2022). doi:10.18429/JACoW-IBIC2022-MOP28, Methodical studies to improve the longitudinal phase space (LPS) tomography of space-charge dominated electron beams were carried out at the Photo Injector Test facility at DESY in Zeuthen (PITZ). An analytical model was developed to quantify mean momentum, RMS energy spread, bunch length and phase advance. Phase advance analysis determined the booster phase scan range and step size to be used for obtaining momentum projections. A slit was introduced before the booster to truncate the beam in transverse plane to strongly reduce the space charge effects. The signal resolution of this truncated beam was improved by careful beta function control at the reference screen of the momentum measurements. The reconstruction algorithm was changed from Algebraic Reconstruction Technique (ART) to Image Space Reconstruction Algorithm (ISRA) owing to its assurance of non-negative solutions. In addition, the initial physically justified assumption of LPS, based on low-energy section measurements, was established to clear out noise-like artefacts. This paper will highlight the improvements made in the LPS tomography and compare the simulated and experimental results., Published by JACoW Publishing, Geneva, Switzerland

[Ebook] IBIC 2022, International Beam Instrumentation Conference : 11-15 September 2022, Krakow, Poland : IBIC2022 - proceedings / Organizers: GSI [Helmholtzzentrum für Schwerionenforschung]; SOLARIS, National Synchrotron Radiation Centre, Jagiellonian University in Krakow , [Geneva, Switzerland] : JACoW Publishing, [2022], International Beam Instrumentation Conference, IBIC 2022, Krakow, Poland, 11 Sep 2022 - 15 Sep 2022; Geneva, Switzerland : JACoW Publishing 277-280 (2022). doi:10.18429/JACoW-IBIC2022-TUP21, A standard technique to measure beam profiles in linear accelerators are screen monitors using scintillating screens. This technique is used e.g. at the European XFEL in order to overcome coherence effects in case of OTR usage [*]. During the XFEL commissioning it was found out that screens based on LYSO:Ce as scintillating material revealed a nonproportional light output [**]. Reason for it is the high particle beam density. As consequence it was decided to exchange LYSO:Ce by GAGG:Ce scintillators because the excitation carriers can rapidly transfer their energy to excited states of gadolinium, and a rapid migration of this energy among the Gd sub-lattice is expected. Driven by the observations at XFEL a series of measurements was started to investigate the properties of various scintillator materials (LYSO:Ce, YAP:Ce, YAG:Ce, LuAG:Ce and GAGG:Ce). The last measurement campaign was carried out at PITZ which allows to operate at higher beam charge and lower electron energy compared to the XFEL. The present work summarizes the results of these measurements., Published by JACoW Publishing, Geneva, Switzerland

12th International Particle Accelerator Conference, IPAC'21, Campinas, Brazil, 24 May 2021 - 28 May 2021; doi:10.18429/JACOW-IPAC2021-WEPAB115, The need for carrier-envelope-phase (CEP) stable THz pump pulses is recognized at many pump-probe experiments at the European XFEL. At the Photo Injector Test Facility at DESY in Zeuthen (PITZ), a proof-of-principle experiment of an accelerator-based THz FEL source is in preparation. Since the CEP stability of FEL pulses is not guaranteed in the SASE regime, a seeding scheme is needed. A common scheme for seeding is to drive the microbunching process with external laser pulses, which are power-limited in the THz range. Alternatively, a pre-bunched beam, generated for example by applying a temporally modulated photocathode laser pulse, can be used to drive the FEL. The beam dynamics with such a seeding method are studied with ASTRA tracking code simulations with space-charge forces as well as experimentally. The results of these studies are shown and discussed.

P3Workshop@SLAC, DESY, 10 Nov 2021

Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil 12th International Particle Accelerator Conference, IPAC'21, Campinas, Brazil, 24 May 2021 - 28 May 2021; 4 pp. (2021). doi:10.18429/JACoW-IPAC2021-WEPAB274, A magnetic bunch compressor has been recently designed for an accelerator-based THz source which is under development at the Photo Injector Test facility at DESY in Zeuthen (PITZ). The THz source is assumed to be a prototype for an accelerator-based THz source for pump-probe experiments at the European XFEL. As an electron bunch is compressed to achieve higher bunch currents for the THz source, we investigate the beam dynamics in the bunch compressor by numerical simulations. A start-to-end simulation optimizer has been developed by combining the use of ASTRA, IMPACT-T, and OCELOT to support the design of the THz source prototype. Coherent synchrotron radiation effects degrade the compression performance for our study cases with bunch charges up to 4 nC and beam energy of 17 MeV at a bending angle of 19 degrees. Simulation and preliminary beam characteristic results will be presented in this paper.

Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil 12th International Particle Accelerator Conference, IPAC'21, Campinas, Brazil, 24 May 2021 - 28 May 2021; 3244-3247 (2021). doi:10.18429/JACOW-IPAC2021-WEPAB257, The Photo Injector Test facility at DESY in Zeuthen (PITZ) is developing a THz SASE FEL as a prototype high repetition rate accelerator-based source for the THz-pumped, X-ray-probed experiments at the European XFEL. For the generation of THz pulses of mJ-level energy from SASE, an electron beam with a high charge (up to 4 nC) and high peak current (~200 A) will be injected into an LCLS-I undulator, which is currently being installed at the end of the photo-injector. The narrow vacuum chamber (11x5 mm) between the magnetic poles and the strong vertical focusing from the undulator, as well as the lack of beam diagnostics, have made it a challenge to match the space-charge dominated beam into the undulator without beam loss during the following transport. In this paper, boundary conditions of a matched electron beam will be discussed and the simulation and experimental study on our matching strategy will be presented.

Linac based X-ray free electron laser demand a high beam quality from the electron source, therefore RF photoinjectors are used to generate the electron bunches for state of the art beam brightness. One important figure of merit for these injectors is the transverse emittance of the generated electron beam, which can be minimized by shaping the photocathode laser pulses. Best performance can be achieved with ellipsoidal laser pulses, but 3D shaping is technically challenging. Typically, a quasi-uniform transverse laser profile is truncated from the Gaussian profile generated by the laser with an aperture to reduce the transverse nonlinear space charge forces. This is investigated in detail by optimizing the laser transverse profile at the Photoinjector Test facility at DESY in Zeuthen (PITZ), where photoinjector R is conducted for the E-XFEL and FLASH free electron lasers at DESY in Hamburg. In this contribution we present experimental results at high acceleration gradients (up to 60 MV/m) for both 250 pC and 500 pC. For a bunch charge of 500 pC an emittance reduction of about 30% compared to the commonly used transverse flat-top laser distribution was achieved., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

AIP Advances 10(3), 035017 - (2020). doi:10.1063/1.5129532, Free-electron laser based x-ray facilities require high-brightness photoinjectors to provide low emittance electron beams at a fixed bunch charge. The emittance optimization in the injector determines the lowest achievable emittance. Based on experimental emittance optimization at the photoinjector test facility at DESY in Zeuthen, a space-charge affected emission regime is identified, in which the optimum transverse beam emittance is achieved and thus, the injector is routinely operated in this regime. An advanced modeling approach is proposed to consider a dynamic emission process in the simulation of injector beam dynamics, meanwhile allowing detailed studies of the impact of strong space-charge fields during emission on the slice formation of the emitted electron bunch at the cathode. As an application, the proposed approach is used to analyze the budget of the optimized transverse beam emittance. An interplay, taking place in the identified emission regime, between intrinsic cathode emittance and space-charge induced emittance is demonstrated. The resolved behavior by simulation is consistent with the corresponding measurement under practical operation conditions of interest. The obtained results are reported., Published by American Inst. of Physics, New York, NY

39th International Free-Electron Laser Conference, FEL19, Hamburg, Germany, 26 Aug 2019 - 30 Aug 2019; JACoW Publishing, Geneva, Switzerland 45-47 (2019). doi:10.18429/JACOW-FEL2019-TUP003, For pump-probe experiments at the European XFEL, a THz source is required to produce intense THz pulses at the same repetition rate as the X-ray pulses from XFEL. Therefore, an accelerator-based THz source with identical electron source as European XFEL was suggested and proof-of-principle experiments utilizing an LCLS I undulator will be performed at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). The main idea is to use a 4nC beam for maximum SASE radiation but to allow different radiation regimes a magnetic bunch compressor can be used. This helps e.g. to reduce the saturation length inside the undulator and also to study super-radiant THz radiation. In this paper a design of a chicane type magnetic bunch compressor using HERA corrector magnets is presented., Published by JACoW Publishing, Geneva, Switzerland

39th International Free-Electron Laser Conference, FEL19, Hamburg, Germany, 26 Aug 2019 - 30 Aug 2019; JACoW Publishing, Geneva, Switzerland 444-447 (2019). doi:10.18429/JACOW-FEL2019-WEP052, In this paper we report our consideration and simulation on the space charge dominated emission in the L-band photocathode RF gun at the Photo Injector Test facility at DESY in Zeuthen (PITZ). It has been found that the emission curve, which relates the extracted and accelerated bunch charge after the gun to the laser energy, doesn’t agree very well with Astra simulations when the emission is nearly or fully saturated. Previous studies with a core-halo model for a better fit of the experimentally measured laser transverse profile as well as with an improved transient emission model have resulted in a better agreement between experimental data and simulation. A 3D FFT space charge solver including mirror charge and binned energy/momentum has been built, which also allows more emission mechanisms to be included in the future. In this paper, the energy spread during emission was preliminarily analyzed. Experimentally measured emission curves were compared with simulation, showing the effect of the inhomogeneity of the laser on the emission and beam parameters., Published by JACoW Publishing, Geneva, Switzerland

39th International Free-Electron Laser Conference, FEL19, Hamburg, Germany, 26 Aug 2019 - 30 Aug 2019; JACoW Publishing, Geneva, Switzerland 473-476 (2019). doi:10.18429/JACOW-FEL2019-WEP062, Cesium telluride is a widely used cathode in photo injectors, and its performance is one of the keys for not only emittance but also reliable operation. Over the years lots of experiences with Cs2Te photocathodes produced with the same recipe and thickness were gained at the DESY photo injectors, but cathode performance dependence on the cathode layer thickness were not investigated. In this paper, we test fresh Cs2Te cathodes with different thickness at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). The QE and thermal emittance of these cathodes inside the high gradient RF gun will be compared. Besides, the injector emittance under the operation conditions of the XFEL will also be measured with these cathodes., Published by JACoW Publishing, Geneva, Switzerland

39th International Free-Electron Laser Conference, FEL19, Hamburg, Germany, 26 Aug 2019 - 30 Aug 2019; JACoW Publishing, Geneva, Switzerland 41-44 (2019). doi:10.18429/JACOW-FEL2019-TUP002, A proof-of-princle experiment for a THz SASE FEL is undergoing preparation at the Photo Injector Test facility at DESY in Zeuthen (PITZ), as a prototype THz source for pump-probe experiments at the European XFEL, which could potentially provide up to mJ/pulse THz radiation while maintaining the identical pulse train structure as the XFEL pulses. In the proof-of-principle experiment, LCLS-I undulators will be installed to generate SASE radiation in the THz range of 3-5 THz from electron bunches of 16-22 MeV/c. One key design is to obtain the peak current of nearly 200 A from the heavily charged bunches of a few nC. In this paper, we report our simulation results on the optimization of the space charge dominated beam in the photo injector and the following transport line with two cathode laser setups. Experimental results based on a short Gaussian laser will also be discussed., Published by JACoW Publishing, Geneva, Switzerland

The Photo Injector Test Facility at DESY in Zeuthen (PITZ) was built to test and to optimize sources of high brightness electron beams for Free-Electron Lasers (FELs). In order to achieve high accelerating gradients and long RF pulse lengths in the RF gun cavities an extensive and safe RF conditioning is required. A State Machine based Automatic Conditioning application (SMAC) was developed to automate the RF conditioning processes, allowing for greater efficiency and performance optimization. SMAC is written in Java and uses State Chart XML (SCXML) as the finite-state machine execution environment based on Harel statecharts. It employs the Distributed Object-Oriented Control System (DOOCS) and Three-fold Integrated Networking Environment (TINE) for the communication with the control system of PITZ. The graphical user interface (GUI) is created by using the Java Swing toolkit. Communication between GUI and SXML processing layer is performed via Document Object Model (DOM) events. The SMAC application has been successfully applied to RF conditioning of several gun cavities at PITZ., Proceedings of the 12th Int. Workshop on Emerging Technologies and Scientific Facilities Controls, PCaPAC2018, Hsinchu, Taiwan

8th International Beam Instrumentation Conference, IBIC2019, Malmö, Sweden, 8 Sep 2019 - 12 Sep 2019; 4 pp. (2019)., At the Photo Injector Test Facility at DESY in Zeuthen (PITZ) high-brightness electron sources are optimized for use at the X-ray free-electron lasers FLASH and European XFEL. Transverse projected emittance measurements are carried out by a single-slit scan technique in order to suppress space charge effects at an energy of ~20 MeV. Previous slice emittance measurements, which employed the emittance measurement in conjunction with a transverse deflecting structure, suffer from limited time resolution and low signal-to-noise ratio (SNR) due to a long drift space from the mask to the observation screen. Recent experimental studies at PITZ show improvement of the temporal resolution and SNR by utilizing quadrupole magnets between the mask and the screen. The measurement setup is described and first results are shown.

39th International Free-Electron Laser Conference, FEL19, Hamburg, Germany, 26 Aug 2019 - 30 Aug 2019; JACoW Publishing, Geneva, Switzerland 599-602 (2019). doi:10.18429/JACOW-FEL2019-THP007, We model and characterize a transverse kick which results from the coaxial RF coupler in the L-band RF gun at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). The RF pulse is typically 600 µs long and used to produce a train of up to 2700 electron bunches. The kick is transient and found to be dependent on the detuning of the resonance frequency of the gun cavity. The frequency detuning within the RF macro-pulse results in a variation in the kick strength along the pulse. This leads to a downstream orbit and size change of individual bunches within the train. Using 3D RF field distributions calculated at detuned frequencies of the cavity, particle tracking simulations are performed to simulate the transient kick onto the bunch train. Given a drift distance, the orbit and size change along a train of fixed length is estimated. Systematic measurements of the kick have meanwhile been carried out. The temperature of the cooling water for the gun is tuned allowing detailed characterization of the frequency detuning within the RF pulse, and thereby measurements of the kick under conditions of practical interest. Experimental findings and simulation results will be presented., Published by JACoW Publishing, Geneva, Switzerland

10th International Particle Accelerator Conference, IPAC’19, Melbourne, Australia, 19 May 2019 - 24 May 2019; Geneva, Switzerland : JACoW Publishing 1964-1967 (2019). doi:10.18429/JACOW-IPAC2019-TUPTS014, In state of the art photoinjector electron sources, cathode performance determines the lower limit of achievable beam emittance. Measuring the thermal emittance at the photocathodes in electron guns is of vital importance for improving the injectors. Traditional methods, like solenoid scan, pepper-pot, need multi-shots and are time-consuming, therefore suffer from machine stability. Here we propose a new method, named cathode transverse momentum imaging. By tuning the gun solenoid focusing, the electrons’ transverse momentum at the cathode is imaged to a downstream screen, which enables a single shot measurement. Several experiments have been done at the Photo Injector Test Facility at DESY in Zeuthen (PITZ) with a Cs2Te cathode. Measurements of cathode transverse momentum, the corresponding spectra, cathode transverse momentum map and its correlation with surface electric field are presented., Published by JACoW Publishing, Geneva, Switzerland

39th International Free-Electron Laser Conference, FEL19, Hamburg, Germany, 26 Aug 2019 - 30 Aug 2019; JACoW Publishing, Geneva, Switzerland 440-443 (2019). doi:10.18429/JACOW-FEL2019-WEP051, A continuous wave (CW) mode operation of the European X-ray Free-Electron Laser (XFEL) is under considerations for a future upgrade. Therefore, a superconducting radio frequency (SRF) CW gun is under experimental development at DESY in Hamburg. Beam dynamics simulations for this setup have been done assuming 100 pC bunch charge and a maximum electric field at the photocathode of 40 MV/m. Experimental studies for these parameters using a normal conducting RF photogun have been performed at the Photo Injector Test facility at DESY in Zeuthen (PITZ). The beam transverse emittance was minimized by optimizing the main photo injector parameters in order to demonstrate the feasibility of generating electron beams with a beam quality required for successful CW operation of the European XFEL for conditions similar to the SRF gun setup., Published by JACoW Publishing, Geneva, Switzerland

The SINBAD facility (Short and INnovative Bunches and Accelerators at DESY) is foreseen to host multiple experiments relating to the production of ultra-short electron bunches and novel high gradient acceleration techniques. The SINBAD-ARES linac will be a conventional S-band linear RF accelerator allowing the production of low charge (0.5 pC - tens pC) ultra-short electron bunches (FWHM length =< 1 fs - few fs) with 100 MeV energy. The installation of the linac will proceed in stages. In this paper we report on the status of the characterization of the ARES RF gun and the installations of the related infrastructure., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

60th ICFA Advanced Beam Dynamics Workshop on Future Light Sources, FLS2018, Shanghai, Deutsches Elektronen Synchrotron, China, 4 Mar 2018 - 9 Mar 2018, We present an overview of the dedicated accelerator R&D facility “SINBAD”, currently under construction at DESY. It will host multiple independent experiments related to the generation and acceleration of ultra-short electron bunches and to the development of various advanced acceleration schemes. SINBAD will initially host two experiments: AXSIS and ARES. The AXSIS collaboration aims to generate fs to sub-fs electron bunches at 15-20 MeV using THz-driven dielectric structures, with the objective to generate ultrafast X-ray pulses by inverse Compton scattering. The first stage of the ARES experiment is to set up a 100 MeV S-band electron linac to produce ultra-short electron bunches with excellent beam arrival time stability. The RF-gun is currently being installed and will be commissioned in spring 2018, followed by the installation and commissioning of the accelerating structures. Thereafter in 2019, the electron bunches will be ideally suited for various experiments on advanced accelerator and diagnostics concepts (e.g. DLA experiments in the context of the ACHIP collaboration). In the long term, external injection into a laser driven plasma acceleration stage is also targeted.

8th International Particle Accelerator Conference, IPAC 2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; Geneva : JACoW, 3253-3255(2017). doi:10.18429/JACoW-IPAC2017-WEPVA004, The "Attosecond X-ray Science: Imaging and Spectroscopy" (AXSIS) experiment at DESY will use a dielectric loaded waveguideto accelerate electron bunches up to 15 MeV. Such a linac will be powered by a narrowband multicycle THz-pulse with a central frequency of 300 GHz. In this paper we focus on the reflection of the excited field at a pinhole, on the optimization of the bunch injection time and on the bunch dynamics in the acceleration process. The linac excitation by the THz-pulse and the bunch acceleration in the excited field are investigated using CST and ECHO simulations., Published by JACoW, Geneva

8th International Particle Accelerator Conference, IPAC 2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; Geneva : JACoW, 3 pp. (2017). doi:10.18429/JACoW-IPAC2017-MOPIK005, We present ultra-small electron injectors based on cascaded cavities excited by short multi-cycle THz signals. The designed structure is a 3.5 cell normal conducting cavity operating at 300 GHz. This cavity is able to generate pC electron bunches and accelerate them up to 250 keV using less than 1 mJ THz energy. Unlike conventional RF guns, the designed cavity operates in a transient state which, in combination with the high frequency of the driving field, makes it possible to apply accelerating gradients as high as 500 MV/m. Such high accelerating gradients are promising for the generation of high brightness electron beams with transverse emittances in the nm-rad range. The designed cavity can be used as the injector for a compact accelerator of low charge bunches., Published by JACoW, Geneva

8th International Particle Accelerator Conference, IPAC 2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; Geneva, Switzerland : JACoW, 869-872(2017). doi:10.18429/JACoW-IPAC2017-MOPVA012, We present an overview of the dedicated R&D facility SINBAD which is currently under construction at DESY. The facility will host multiple independent experiments on the acceleration of ultra-short electron bunches and advanced acceleration schemes. In its initial phase, SINBAD will host two experiments: AXSIS and ARES. The AXSIS collaboration aims to accelerate fs-electron bunches to 15 MeV in a THz driven dielectric structure and subsequently create X-rays by inverse Compton scattering. The first stage of the ARES experiment is to set up a 100 MeV S-band electron linac to produce ultra-short electron bunches with excellent beam arrival time stability. Once this is achieved, the electrons will be ideally suited to be injected into experiments for testing advanced accelerator concepts e.g. DLA experiments in the context of the ACHIP collaboration. In the long term, external injection into a laser driven plasma acceleration stage is targeted as well., Published by JACoW, Geneva, Switzerland

8th International Particle Accelerator Conference, IPAC 2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; Geneva, Switzerland : JACoW, 1406-1408(2017). doi:10.18429/JACoW-IPAC2017-TUPAB038, We present results on an improved THz-driven electron gun using transversely-incident single-cycle THz pulses using a horn-coupler. Intrinsic synchronization between the electrons and the driving field was achieved by using a single laser system to create electrons by UV photoemission and to create THz radiation by difference frequency generation in a tilted-pulse front geometry. Details of the optical setups for the UV and THz pulses will be described as well as preliminary results showing evidence of electron acceleration., Published by JACoW, Geneva, Switzerland

8th International Particle Accelerator Conference, IPAC 2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; Geneva : JACoW, 3 pp. (2017). doi:10.18429/JACoW-IPAC2017-MOPIK006, The AXSIS (Attosecond X-ray Science: Imaging and Spectroscopy) project aims for development of a compact, fully coherent, THz-driven, attosecond X-ray source. A compact THz driven gun was developed, produced and tested as a source of the ultra-short electron bunches required for the project. To characterize the low energy, low-charge beam produced by such a gun tailored diagnostic devices were developed and commissioned at a test-stand chamber in CFEL (DESY). Results of the first experiments on the production and characterization of the electron beam are presented., Published by JACoW, Geneva

28th Linear Accelerator Conference, LINAC2016, East Lansing, USA, 25 Sep 2016 - 30 Sep 2016; JACoW, Geneva, Switzerland 3 pp. (2017). doi:10.18429/JACoW-LINAC2016-MOPLR013, Since more than a decade, the photo injector test facility at DESY, Zeuthen site (PITZ), has developed and optimized high brightness electron sources for modern Free Electros Lasers like FLASH and the European XFEL. Despite a very high performance of the photo injector was experimentally demonstrated, several discrepancies between measurements and beam dynamics simulations have been revealed. Although the optimized measured values of the projected transverse emittance are close to those obtained from the beam dynamics simulations, the corresponding experimental machine parameters show certain systematic deviations from the simulated optimized setup. As a source for these deviations, electron beam imperfections were experimentally investigated. This includes studies on bunch charge production, electron beam imaging using the RF gun with its solenoid, and investigations on the transverse asymmetry of the electron beam generated in a rotationally symmetric gun cavity. Experimental studies were supplied with corresponding beam dynamics simulations. The paper reports on results of these studies., Published by JACoW, Geneva, Switzerland

7th International Particle Accelerator Conference, Busan, Korea, 8 May 2016 - 13 May 2016 ; (2016)., The Photo Injector Test facility at DESY, Zeuthen site (PITZ), was built with the aim to develop and characterize electron sources for future usage at FLASH and at the European XFEL. Recently, the main focus at PITZ has been the study of gun reliability and photoinjector performance at high average power. The goal is to get stable and reliable operation with 6.4 MW peak power in the gun at 650 μs RF pulse length and 10 Hzrepetition rate. To achieve this, a new RF feed system with two RF windows was installed at PITZ in 2014. During this test, the old gun 4.2 with a modified back-plane design for better cathode contact has been used. In this contribution the results of the RF conditioning of gun 4.2 with a detailed interlock analysis will be reported as well as results from recent electron beam characterization.

The SINBAD facility (Short and INnovative Bunches and Accelerators at Desy) is foreseen to host various experiments in the field of production of ultra-short electron bunches and novel high gradient acceleration technique. The SINBAD linac, also called ARES (Accelerator Research experiment at SINBAD), will be a conventional S-band linear RF accelerator allowing the production of low charge (0.5 pC - few pC) ultra-short electron bunches (FWHM, length, Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

For the operation of free electron lasers (FELs) like the European X-FEL and FLASH located at DESY, Hamburg Site, high quality electron beams are required already from the source. The Photo Injector Test facility at DESY, Zeuthen Site (PITZ) was established to develop, characterize and optimize electron sources for such FELs. Last year the work at PITZ focused on the optimization of a photo injector operated with the startup parameters of the European X-FEL. This implies photocathode laser pulses with a Gaussian temporal profile of about 11-12 ps FWHM to drive the photo gun operated at a gradient of 53 MV/m. Significant effort was spent on the electron beam characterization and optimization for various bunch charges. Emittance measurements were performed as a function of major accelerator parameters such as main solenoid current, laser spot size on the cathode and the gun launching phase. The requirement on the beam emittance for bunch charge of 500 pC for the European XFEL commissioning phase has been demonstrated. Results of these studies accompanied with the corresponding simulations are presented in this paper., Proceedings of the 37th International Free Electron Laser Conference, FEL2015, Daejeon, Republic of Korea

High brightness electron sources for free electron lasers like FLASH and the European XFEL are developed, optimized and characterized at the Photo Injector Test facility at DESY in Zeuthen (PITZ). Last year the facility was significantly upgraded with a new prototype photocathode laser capable of producing homogeneous ellipsoidal pulses. Previous simulations have shown that the corresponding pulses produce high brightness electron bunches with minimized emittance. Furthermore, a new normal conducting RF gun cavity was installed with a modified two-window waveguide RF feed layout for stability and reliability tests, as required for the European XFEL. Other relevant additions to the facility include beamline modifications for improved electron beam transport through the PITZ accelerator, refinement of both the cooling and RF systems for improved parameter stability, and preparations for the installation of a plasma cell. This paper describes the facility upgrades and reports on the operational experience with the new components., Proceedings of the 37th International Free Electron Laser Conference, FEL2015, Daejeon, Republic of Korea

The Photo Injector Test facility PITZ at DESY, Zeuthen site, characterizes and optimizes high brightness electron sources for linac-based Free Electron Laser (FELs) with a specific focus on the requirements of FLASH and the European XFEL. X-ray FELs require high brightness electron beam in terms of high peak current, small transverse emittance and energy spread. Such high quality beams are mandatory for efficient SASE generation in a single pass through long undulators with narrow gaps. Photocathode laser pulse shaping is a powerful tool to optimize the photo injector performance. Recently, a new photocathode laser system capable of producing 3D quasi-ellipsoidal pulses has been installed at PITZ. It is foreseen to operate this new system in parallel to the nominal one that generates cylindrical pulses with various temporal profiles. A set of numerical simulations was performed to study and compare the beam dynamics of electron beams produced with 3D ellipsoidal laser profile with the typical cylindrically shaped (flat-top) profile. Different bunch charges from 20 pC up to several nC are considered, in order to find an optimum PITZ machine setup which will yield the lowest transverse emittance. we present and discuss the results of this comparison in the submission., Proceedings of the 37th International Free Electron Laser Conference, FEL2015, Daejeon, Republic of Korea

University of Hamburg, Diss., 2013; DESY-THESIS (2013). doi:10.3204/DESY-THESIS-2013-043, Light is one of the main tools for the investigation of natural phenomena. Light produced with the help of synchrotron machines serves to investigate many phenomena in natural sciences for many years. However the synchrotron light has a limited degree of spatial coherence, restriction on the minimum achievable pulse duration at the level of about 30 ps and not sufficient brilliance to perform a lot of experiments. With the invention of free electron lasers (FELs) new opportunities are opened as the light produced by the free electron lasers is spatially coherent, the pulse duration of the produced light can be in the order of 10 fs and below and the brilliance is much higher compared to synchrotron light. To produce high quality laser light with a short wavelength free electron lasers like the European XFEL and FLASH require electron beams with a high charge and low transverse emittance. The photo injector test facility at DESY, Zeuthen site, was built with the aim to develop and characterize electron sources for future usage at FLASH and the European XFEL. The emittance of the produced electron beam plays a key role as it influences the final brilliance and the minimum achievable wavelength of the produced laser light. This work is devoted to investigations of the emittance of electron beams with different charges. The emittance of the electron beam depends on many machine parameters such as UV laser pulse shape and its size, solenoid focusing current and accelerating cavities settings. Methodical studies of the emittance dependencies on these parameters were done in simulations using a particle tracking code as well as experimentally., Published by DESY, Hamburg