Lagzda, A. Aitkenhead, A. Corsini, R. Farabolini, W. Jones, R.M. Kirkby, K. MacKay, R. Van Herk, M. Very-High Energy Electron (VHEE) Studies at CERN's CLEAR User Facility JACoW Publishing Geneva, Switzerland 978-3-95450-184-7 10.18429/JACoW-IPAC2018-MOPML023 English 445-448 MOPML023 Contribution to a conference proceedings 2018 2018-06 https://doi.org/10.18429/JACoW-IPAC2018-MOPML023 http://jacow.org/ipac2018/papers/mopml023.pdf Here we investigate how inserts of various densities (0.001-2.2 g/cm³) affect the dose distribution properties of VHEE beams at ~150 MeV. A range variation comparison was also made with clinical proton beams using TOPAS/GEANT4 Monte Carlo simulations. In addition, we assess the viability of scattering foils for optimizing the size of VHEE beams for radiotherapy purposes. The experiments were conducted at CERN's CLEAR user facility.