Ulrik I. Uggerhøj

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[1] We have studied sulfuric acid aerosol nucleation in an atmospheric pressure reaction chamber using a 580 MeV electron beam to ionize the volume of the reaction chamber. We find a clear contribution from ion‐induced nucleation and consider this to be the first unambiguous observation of the ion‐effect on aerosol nucleation using a particle beam under(More)
BACKGROUND AND PURPOSE Antiprotons travel through tissue in a manner similar to that for protons until they reach the end of their range where they annihilate and deposit additional energy. This makes them potentially interesting for radiotherapy. The aim of this study was to conduct the first ever measurements of the biological effectiveness of(More)
The total cross sections for single ionization of helium and single and double ionization of argon by antiproton impact have been measured in the kinetic energy range from 3 to 25 keV using a new technique for the creation of intense slow antiproton beams. The new data provide benchmark results for the development of advanced descriptions of atomic(More)
At very high energies the Earth magnetic field, although in many other connections considered rather weak, acts as a strong field on photons and leptons. This paper discusses the intimate connection between this effect and the corresponding 'strong field effects' observed at accessible accelerator energies in aligned single crystals. As such, these effects(More)
Experimental results for the radiative energy loss of 149, 207, and 287 GeV electrons in a thin Ir target are presented. From the data we conclude that at high energies the radiation length increases in accordance with the Landau-Pomeranchuk-Migdal (LPM) theory and thus electrons become more penetrating the higher the energy. The increase of the radiation(More)
Experimental results for the restricted energy loss of pairs created from 1-178 GeV photons in a thin Au target and subsequently passing a CCD detector are presented. It is shown that pairs--when detected close to the creation vertex--suffer a reduced energy loss due to the internal screening of the charges constituting the pair. Furthermore, the ability to(More)
We report the first observation of a shoulder in the radiation spectrum from GeV electrons in a structured target consisting of two thin and closely spaced foils. The position of the shoulder depends on the target spacing and is directly connected to the finite formation length of a low-energy photon emitted by an ultrarelativistic electron. With the(More)
The slowing-down process of pointlike charged particles in matter has been investigated by measuring the stopping power for antiprotons in materials of qualitatively very different nature. Whereas the velocity-proportional stopping power observed for metal-like targets such as aluminum over a wide energy range of 1-50 keV is in agreement with expectations,(More)
The processes of coherent bremsstrahlung (CB) and coherent pair production (CPP) based on aligned crystal targets have been studied in the energy range 20 –170 GeV. The experimental arrangement allowed for measurements of single photon properties of these phenomena including their polarization dependences. This is significant as the theoretical description(More)