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@PHDTHESIS{Stehr:630593,
      author       = {Stehr, Felix Paul Georg},
      othercontributors = {List, Jenny and Moortgat-Pick, Gudrid},
      title        = {{T}owards {S}pin-{P}olarized {E}lectron {B}eams from a
                      {L}aser-{P}lasma {A}ccelerator},
      school       = {University of Hamburg},
      type         = {Dissertation},
      address      = {Hamburg},
      publisher    = {Staats- und Universitätsbibliothek Hamburg Carl von
                      Ossietzky},
      reportid     = {PUBDB-2025-01873},
      pages        = {227},
      year         = {2025},
      note         = {Dissertation, University of Hamburg, 2025},
      abstract     = {The LEAP (Laser Electron Acceleration with Polarization)
                      project at DESY is a proof-of-principle experiment aiming to
                      demonstrate the generation -- thus also the transport -- of
                      spin-polarized electron beams from a laser-plasma
                      accelerator (LPA). This is expected to be achieved using a
                      pre-polarized plasma source, generated via the
                      photodissociation of HCl molecules with an ultraviolet (UV)
                      dissociation laser. Compton transmission polarimetry is
                      envisioned for polarization measurements, inferring electron
                      polarization from the transmission asymmetry of
                      bremsstrahlung photons through magnetized iron. This thesis
                      explores three key aspects of LEAP, focusing on development
                      an experimental realization. First, a feasibility study was
                      conducted to generate the UV dissociation laser via cascaded
                      second-harmonic generation in two beta-barium borate
                      crystals directly from the LPA driver laser. A measured
                      conversion efficiency of $\eta_{\omega \rightarrow
                      4\omega}\approx0.8\,\\%$ into the UV demonstrates the
                      feasibility of this approach. Second, a homogeneous
                      Cherenkov lead-glass calorimeter was built as an integral
                      part of the LEAP Compton transmission polarimeter.
                      Furthermore, it was tested and calibrated with single
                      electrons at the DESYII Test Beam Facility. The derived
                      calorimeter energy resolution of $\frac{\sigma_{E}}{\langle
                      E \rangle} < 2\,\\%$ at TeV-scale total energies meets the
                      requirement for its application within the LEAP polarimeter.
                      GEANT4 simulations indicate a nonlinear calorimeter response
                      to low-energy particles ($<10\,$MeV). The uncertainty of
                      this response introduces a relative uncertainty of
                      $\sim1.5\,\\%$ on the simulated analyzing power of the
                      polarimeter.Finally, the full polarimeter setup, consisting
                      of a solenoid magnet and the Cherenkov calorimeter, was
                      commissioned at the FLARE facility using an unpolarized LPA
                      electron beam. Initial system tests, beam charge and energy
                      characterization, and operational polarization measurements
                      were conducted. Simulations determined the analyzing power
                      of the system to be $A=11.74\pm0.18\,\\%$ ($\frac{\Delta
                      A}{A} = 1.6\,\\%$) with the dominant uncertainty arising
                      from the calorimeter response. The actual measurement was
                      found to be primarily influenced by beam stability and
                      control. In particular, observed asymmetries -- unrelated to
                      beam polarization -- can be explained by potential energy
                      drifts. Extrapolation to realistic polarization measurements
                      indicates that shot-to-shot charge and energy stability must
                      be provided at the $\leq 1\,\\%$ level to enable reliable
                      polarization measurements.},
      cin          = {FTX / MPA},
      cid          = {I:(DE-H253)FTX-20210408 / I:(DE-H253)MPA-20200816},
      pnm          = {PHGS, VH-GS-500 - PIER Helmholtz Graduate School
                      $(2015_IFV-VH-GS-500)$ / 622 - Detector Technologies and
                      Systems (POF4-622)},
      pid          = {$G:(DE-HGF)2015_IFV-VH-GS-500$ / G:(DE-HGF)POF4-622},
      experiment   = {EXP:(DE-H253)PLASMA-20250101 /
                      EXP:(DE-H253)TestBeamline24-20150101},
      typ          = {PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:gbv:18-ediss-128363},
      doi          = {10.3204/PUBDB-2025-01873},
      url          = {https://bib-pubdb1.desy.de/record/630593},
}