The rapid progress that plasma wakefield accelerators are experiencing is now posing the question as to whether they could be included in the design of the next generation of highenergy electronpositron colliders. However, the typical structure of the accelerating wakefields presents challenging complications for positron acceleration. Despite seminal proofofprinciple experiments and theoretical proposals, experimental research in plasmabased acceleration of positrons is currently limited by the scarcity of positron beams suitable to seed a plasma accelerator. Here, we report on the first experimental demonstration of a laserdriven source of ultrarelativistic positrons with sufficient spectral and spatial quality to be injected in a plasma accelerator. Our results indicate, in agreement with numerical simulations, selection and transport of positron beamlets containing
For the first time, timedependent internal charge amplification through impact ionization has been observed in a planar germanium (Ge) detector operated at cryogenic temperature. In a time period of 30 and 45 min after applying a bias voltage, the charge energy corresponding to a baseline of the 59.54 keV
 Award ID(s):
 1743790
 NSFPAR ID:
 10405639
 Publisher / Repository:
 Springer Science + Business Media
 Date Published:
 Journal Name:
 The European Physical Journal C
 Volume:
 83
 Issue:
 4
 ISSN:
 14346052
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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