Status in 2021 and request for beamtime in 2022 for CERN NA63

In the NA63 experiment of April 2018 reliable data was taken for 40 and 80 GeV electrons and positrons aligned to the h100i axis of a diamond crystal of thickness 1.5 mm, as well as for 40 and 80 GeV electrons on a 1.0 mm thick diamond aligned to the h100i axis. The 2017 + 2018 results have been published in Phys. Rev. D. and a shorter paper is in the making for a special issue on "Strong Field Quantum Electrodynamics with high power lasers and particle beams" in New Journal of Physics. For the 2017 data, a paper has been published in Phys. Rev. Research in 2019, and our experimental findings have inspired another paper published in Phys. Rev. Lett. For the year 2022 we request 2 weeks of beamtime in the SPS H4 to do a measurement of trident production, e− ! e−e+e−, in strong crystalline fields. We requested 2 weeks of beam time in 2021, but high demand prevented NA63 from getting beam time allocated and we therefore submit our request again. The trident process is closely related to the production of muon pairs, e− ! e−μ+μ−, and single crystals may prove to be an attractive source to obtain muons of high intensity and small emittance, as required for a muon collider. The trident results obtained in 2009, and published in 2010, are strongly at odds with theory (factor 3-4 discrepancy). Since then we have acquired and have been using MIMOSA-26 position-sensitive detectors with a resolution about a factor 40 higher than the drift chambers used in 2009, and now with true multi-hit capability, a significant advantage when looking for trident events. Thus we have substantial improvements in our equipment that enable a much more precise measurement.