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Physica medica 104, 174 - 187 (2022). doi:10.1016/j.ejmp.2022.10.026, At the Photo Injector Test facility at DESY in Zeuthen (PITZ), an R&D platform for electron FLASH and very high energy electron radiation therapy and radiation biology is being prepared FLASH$\mathrm{{\ell}ab@}$PITZ). The beam parameters available at PITZ are worldwide unique. They are based on experiences from 20 + years of developing high brightness beam sources and an ultra-intensive THz light source demonstrator for ps scale electron bunches with up to 5 nC bunch charge at MHz repetition rate in bunch trains of up to 1 ms length, currently 22 MeV (upgrade to 250 MeV planned). Individual bunches can provide peak dose rates up to 10$^{14}$ Gy/s, and 10 Gy can be delivered within picoseconds. Upon demand, each bunch of the bunch train can be guided to a different transverse location, so that either a “painting” with micro beams (comparable to pencil beam scanning in proton therapy) or a cumulative increase of absorbed dose, using a wide beam distribution, can be realized at the tumor. Full tumor treatment can hence be completed within 1 ms, mitigating organ movement issues. With extremely flexible beam manipulation capabilities, FLASHlab@PITZ will cover the current parameter range of successfully demonstrated FLASH effects and extend the parameter range towards yet unexploited short treatment times and high dose rates. A summary of the plans for FLASH$\mathrm{{\ell}ab@}$PITZ and the status of its realization will be presented., Published by Elsevier, Amsterdam

Photocathode Physics for Photoinjectors Workshop, California, DESY, USA, 10 Nov 2021 - 12 Nov 2021

FRPT 2021, Wien, DESY, Austria, 1 Dec 2021 - 3 Dec 2021

Photocathode Physics for Photoinjectors Workshop, California, DESY, USA, 10 Nov 2021 - 12 Nov 2021

Dissertation, Universität Hamburg, 2020; 155 pp. (2020). = Dissertation, Universität Hamburg, 2020, Light is one of the most versatile tools in an experimenter’s toolbox and has been used toinvestigate the natural world since the invention of the lens and as new techniques, sources,and materials have been developed. One of the biggest turning points was the development ofa brilliant, coherent, light source: the laser. This simple device revealed predicted but hithertounprovable science before the availability of such an intense light source. Since then thisversatile tool has enabled and opened up numerous avenues of research and development ofcommunication networks, computer processors, medical manufacturing and treatments, drugresearch, basic commerce, and much more.However, despite its flexibility a conventional laser system is limited by its materialconstraints. The crystals, glasses, and optical elements used in modern, ultrafast, high powerlasers can only endure a finite amount of energy flux before damage sets in. Furthermore, thespectral range is limited by the most fundamental of material properties: absorption.Extending the operational range further and further into the ultraviolet (UV) wavelengths andbeyond is difficult with the increasing number of exotic technical requirements.Modern Free Electron Lasers (FEL) circumvent these constraints on the generation andpropagation of extreme light pulses by simply not having any material. Instead coherent,ultrashort light pulses are generated by exploiting relativistic electron bunches generated in anaccelerator. By utilizing periodically alternating magnetic fields and spontaneous lightgeneration Self Amplifcation by Stimulated Emision (SASE) can be induced and a brilliant,coherent laser pulse in the deep UV, soft X-ray, and beyond can be produced. In effect a lasersystem without an optical cavity- without materials. This approach permits unparalleledtunability and flexibility of the laser pulse properties as the repetition rate, duty cycle,duration, wavelength, intensity and coherence can all be dynamically modified.For modern, linear, electron accelerators and light sources such as the Free Electron Laser inHamburg (FLASH) and the European XFEL the entire foundation of this process is thephotoinjector and the conventional laser system used to drive photoelectron production withinit. Fundamentally, the properties of the electron bunches determine the quality of lasing. Thesize, charge, duration, distribution and subsequently the emittance (the volume the bunchestake in phasespace) all play a role and are determined by the photoinjector and primarily bythe laser pulse properties.The Photo Injector Test Facility at DESY, Zeuthen (PITZ) was founded to pioneer newtechnologies and concepts to improve and characterize photoinjectors and subsequently helppush the limits and capabilities of FELs. As such it is uniquely situated to test and developnew photocathode drive lasers.In this work the feasibility and application of a new method to produce volumetricallyshaped photocathode laser pulses, and subsequently shaped electron bunches, at PITZ isdetailed and demonstrated. First, the basic theory, and numerical simulations of laser pulsesshaped by directly accessing their spectral domain and modifying it with Spatial LightModulators, and the potential advantages of the shaped electron bunches are shown.Furthermore, shaped electron bunches arising from shaped photocathode laser pulses aredemonstrated and utilized to improve photoelectron bunch properties. Finally, lessons,designs, and preliminary results of an improved laser system are shown.

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.

10th International Particle Accelerator Conference, IPAC’19, Melbourne, Australia, 19 May 2019 - 24 May 2019; Geneva, Switzerland : JACoW Publishing 2286-2290 (2019). doi:10.18429/JACOW-IPAC2019-WEZPLS2, Beam driven wakefield acceleration (PWFA) schemes in plasmas are among the most promising candidates for novel, compact accelerators. Several aspects of PWFA are under investigation at the Photoinjector Test facility at DESY in Zeuthen (PITZ). One of the main characteristics of these accelerators is the ratio between field strength usable for acceleration and decelerating field strength in the driver bunch, the so called transformer ratio. To reach high transformer ratios usually shaped bunches, e.g. with ramped current profiles are employed as drivers. The so-called self-modulation instability, which causes transverse modulation of a bunch longer than the plasma wavelength, is proposed as a means of supplying short driver bunches for proton-driven PWFA. This talk will give an overview on experimental results in these two aspects of PWFA at PITZ with a focus on the production of electron bunches enabling high transformer ratio acceleration by shaping the photocathode laser pulses of a photoinjector and the demonstration of high transformer ratio PWFA. Simulations and further developments on the shaping techniques, allowing highly flexible electron bunches for future plasma wakefield accelerators are also presented., Published by JACoW Publishing, Geneva, Switzerland

DPG Frühjahrstagung 2018, Würzburg, Germany, 19 Mar 2018 - 23 Mar 2018, The photo injector test facility at DESY, Zeuthen site (PITZ), was built to test, develop and experimentally optimize high brightness photoelectron sources for superconducting linac driven SASE FELs, such as the Free electron LASer in Hamburg (FLASH) and the European X-ray Free Electron Laser (European XFEL). Extremely low beam emittance beyond the original European XFEL requirements has been demonstrated at PITZ in 2011. Further improvements of the transverse projected beam emittance are in good progress by generating 3D ellipsoidal electron beams on the basis of photocathode laser pulse shaping. In this talk, an overview of the PITZ facility is given. New progress on emittance optimization will be presented.

4. Annual MT Meeting, Berlin, Germany, 12 Jun 2018 - 14 Jun 2018

DPG - Frühjahrstagung 2018, Würzburg, Germany, 19 Mar 2018 - 23 Mar 2018, The photo injector test facility at DESY, Zeuthen site (PITZ), was built to test, develop and experimentally optimize high brightness photoelectron sources for coherent light sources. The produced high quality electron beam and a large variety of advanced beam diagnostics at PITZ also provide excellent oppotunities for a wide field of research activities. This includes experiments of particle beam driven plasma wakefield acceleration, experiments towards a prototype IR/THz source for pump-probe experiments at the European XFEL, experimental demonstration of ballistic bunching with dielectric-lined waveguides, electron diffraction experiments and many others. In this talk, an overview of recent research activities at PITZ is given. Corresponding results will be presented.

PITZ Collaboration Meeting, DESY, Zeuthen

PITZ collaboration meeting, Zeuthen, DESY Zeuthen, Germany, 31 May 2016 - 1 Jun 2016 ; (2016).

PITZ Collaboration Meeting, Zeuthen, DESY Zeuthen, 29 Nov 2016 - 30 Nov 2016 ; (2016).

Physical review letters 120(14), 144802 (2018). doi:10.1103/PhysRevLett.120.144802, Self-modulation of an electron beam in a plasma has been observed. The propagation of a long (several plasma wavelengths) electron bunch in an overdense plasma resulted in the production of multiple bunches via the self-modulation instability. Using a combination of a radio-frequency deflector and a dipole spectrometer, the time and energy structure of the self-modulated beam was measured. The longitudinal phase space measurement showed the modulation of a long electron bunch into three bunches with an approximately 200 keV=c amplitude momentum modulation. Demonstrating this effect is a breakthrough for proton-driven plasma accelerator schemes aiming to utilize the same physical effect., Published by APS, College Park, Md.

DPG - Frühjahrstagung 2018, Würzburg, Germany, 19 Mar 2018 - 23 Mar 2018, Transverse emittance is one of the most important properties for high-brightness electron beams used for X-Ray free-electron lasers. The photo injector test facility at DESY in Zeuthen (PITZ) focuses on the development of high-brightness electron sources. The two main methods to measure the emittance are the quadrupole scan and the slit scan. Combining either of these methods with a transverse deflecting cavity allows the measurement of the slice emittance. At PITZ, space-charge effects at the low beam momentum of 24 MeV/c complicate in particular the quadrupole scan. This has to be considered in the emittance measurements. First slit-scan based slice emittance results will be shown next to studies on the beam transport for quadrupole scans.