Conceptual design report for the LUXE experiment

This Conceptual Design Report describes LUXE (Laser Und XFEL Experiment), an experimental campaign that aims to combine the high-quality and high-energy electron beam of the European XFEL with a powerful laser to explore the uncharted terrain of quantum electrodynamics characterised by both high energy and high intensity. We will reach this hitherto inaccessible regime of quantum physics by analysing high-energy electron-photon and photon-photon interactions in the extreme environment provided by an intense laser focus. The physics background and its relevance are presented in the science case which in turn leads to, and justifies, the ensuing plan for all aspects of the experiment: Our choice of experimental parameters allows (i) field strengths to be probed where the coupling to charges becomes non-perturbative and (ii) a precision to be achieved that permits a detailed comparison of the measured data with calculations. In addition, the high photon flux predicted will enable a sensitive search for new physics beyond the Standard Model. The initial phase of the experiment will employ an existing 40 TW laser, whereas the second phase will utilise an upgraded laser power of 350 TW. All expectations regarding the performance of the experimental set-up as well as the expected physics results are based on detailed numerical simulations throughout

Letter of Intent for the LUXE Experiment

This Letter of Intent describes LUXE (Laser Und XFEL Experiment), an experiment that aims to use the high-quality and high-energy electron beam of the European XFEL and a powerful laser. The scientific objective of the experiment is to study quantum electrodynamics processes in the regime of strong fields. High-energy electrons, accelerated by the European XFEL linear accelerator, and high-energy photons, produced via Bremsstrahlung of those beam electrons, colliding with a laser beam shall experience an electric field up to three times larger than the Schwinger critical field (the field at which the vacuum itself is expected to become unstable and spark with spontaneous creation of electron-positron pairs) and access a new regime of quantum physics. The processes to be investigated, which include nonlinear Compton scattering and nonlinear Breit-Wheeler pair production, are relevant to a variety of phenomena in Nature, e.g. in the areas of astrophysics and collider physics and complement recent results in atomic physics. The setup requires in particular the extraction of a minute fraction of the electron bunches from the European XFEL accelerator, the installation of a powerful laser with sophisticated diagnostics, and an array of precision detectors optimised to measure electrons, positrons and photons. Physics sensitivity projections based on simulations are also provided

Conceptual design report for the LUXE experiment

AbstractThis Conceptual Design Report describes LUXE (Laser Und XFEL Experiment), an experimental campaign that aims to combine the high-quality and high-energy electron beam of the European XFEL with a powerful laser to explore the uncharted terrain of quantum electrodynamics characterised by both high energy and high intensity. We will reach this hitherto inaccessible regime of quantum physics by analysing high-energy electron-photon and photon-photon interactions in the extreme environment provided by an intense laser focus. The physics background and its relevance are presented in the science case which in turn leads to, and justifies, the ensuing plan for all aspects of the experiment: Our choice of experimental parameters allows (i) field strengths to be probed where the coupling to charges becomes non-perturbative and (ii) a precision to be achieved that permits a detailed comparison of the measured data with calculations. In addition, the high photon flux predicted will enable a sensitive search for new physics beyond the Standard Model. The initial phase of the experiment will employ an existing 40 TW laser, whereas the second phase will utilise an upgraded laser power of 350 TW. All expectations regarding the performance of the experimental set-up as well as the expected physics results are based on detailed numerical simulations throughout.</jats:p

Efficacy Testing of Shielding Materials for XFEL Using the Radiation Fields Produced at FLASH.

The European X-Ray Free Electron Laser (XFEL), a grand international scientific endeavour to produce extremely brilliant (~ 1033 photons/s/mm2/mrad2), ultra short pulsed (~ 100 fs) coherent X-rays of wavelengths down to 0.1 nm is now under construction at DESY (Deutsches Elektronen-Synchrotron) laboratory. The XFEL facility, which measures a total length of 3.3 km will be driven by a 1.7 km long, 20 GeV electron linac made of high-purity superconducting niobium cavities developed at DESY under TESLA (Tera Electron-Volt Superconducting Linear Accelerator) technology collaboration. The electron linac section of the XFEL will be housed in a 5 m diameter underground concrete tunnel. Furthermore, all electronic equipments vital to machine safety, operation and control system of the linac, as well as the klystrons and power supplies will also be installed in the tunnel. Intense field of parasitic (ionising) radiations will be generated during linac operation thereby causing radiation induced detrimental effects in the electronic devices. Hence, in order to guarantee a safe and flawless linac operation, it is imperative to implement suitable radiation shielding around the racks containing those electronic equipments.Radiation shielding design for the electronics operating in close vicinity of a high-energy electron linac, installed in a narrow 5 m diameter tunnel is complex and has to cope with the following major challenges: (a) Due to space limitation in the tunnel, a compact shielding is mandatory, i.e. provision of a maximum radiation attenuation at the location of interest with a minimum shield thickness and (b) extremely complex radiation exposure geometry and large variation of linac operation conditions make the shielding calculations based on Monte-Carlo simulation unsuitable to produce reliable results. We have therefore, adopted the analytical calculation method using the results of radiation measurement experiments at Free Electron Laser in Hamburg (FLASH), already operational at DESY. The optimum photon shielding parameters for selected materials were calculated.This report highlights experimental methods to estimate the photon (bremsstrahlung gamma rays) and neutron field distributions along FLASH tunnel. Photon attenuation (shielding) parameters in industrial lead, carbon steel, heavy concrete and multi-layer shield (lead + heavy concrete) are presented. Application of this evaluated data for the construction of optimised shielding of electronics racks to be installed in XFEL tunnel is recommended

Low-temperature high-resolution VUV spectroscopy of Ce3+ doped LiYF4, LiLuF4 and LuF3 crystals

RadiochFor LiYF4:Ce3+, LiLuF4:Ce3+ and LuF3:Ce3+ crystals UV/visible emission and time-resolved VUV/UV excitation spectra were recorded at liquid helium temperature with spectral resolution of 0.1 nm for excitation spectra and better than 0.3 nm for emission spectra. Well resolved fine structures due to zero-phonon lines were clearly observed in both excitation and emission spectra for LiYF4:Ce3+ and LiLuF4:Ce3+. For LuF3:Ce3+ crystal no fine structure was detected in the spectra even at the highest spectral resolution. Under the host excitation, the fine structure for high-energy emission band of Ce3+ (5d-F-2(5/2)) in LiLuF4:Ce3+ becomes well pronounced because of weaker reabsorption effect, as compared to Ce3+ 4f-5d absorption, due to small penetration depth for exciting radiation. As a result the crystal-field splitting for F-2(7/2) and F-2(5/2) levels of Ce3+ in LiLuF4 crystal was measured. First observation of zero-phonon lines at similar to81,550 and similar to82,900 cm(-1) as well as vibronic side bands due to interconfigurational 4f(14)-4f(13)5d transitions in Lu3+ is reported for excitation spectrum of LiLuF4:Ce3+

6d5f and 5f2f^ {2} configurations of U4+U^ {4+} doped into LiYF4F_{4} and YF3F_{3} crystals

RadiochThe properties of U4+ 6d5f→5f2 luminescence in LiYF4 and 5f2→5f2 luminescence in YF3 are very similar to properties of 5d4f→4f2 and 4f2→4f2 luminescence in the iso-electronic Pr3+ ion embedded into the same crystals. In LiYF4 the lowest level of the 6d5f electronic configuration of U4+ is located below the highest 1S0 level of the 5f2 electronic configuration whereas in YF3 the relative energy position of these levels is opposite. Accordingly, the interconfigurational broad-band luminescence from the lowest 6d5f level is observed from the U4+:LiYF4 crystal, but the intraconfigurational narrow-line luminescence from the 1S0 level of the U4+ ion is observed in the U4+:YF3 crystal when it is excited into the 6d5f levels of U4+. The U4+ doped crystals can be considered as more attractive phosphor systems based on cascade luminescence compared with those of Pr3+ doped because the main 1S0 emission in U4+ occurs in the visible range (around 500 nm). However, no definite evidence of the second step in cascade luminescence originating from the lower 5f levels populated by the radiative decay of the 1S0 level of U4+ was identified in the emission spectrum of the U4+:YF3 crystal