A minimally invasive transverse beam profile monitor based on supersonic gas curtain technology and beam-induced fluorescence has been developed and demonstrated. The concept presented can be used to measure both the profile of the proton beam in the Large Hadron Collider (LHC) and the concentricity of the electron and the proton beams in the LHC hollow electron lens. In this Letter, the performance of such a monitor for a low energy electron beam is discussed, which paves the way for its wider implementation.

Noninterceptive beam profile monitors are of great importance for many particle accelerators worldwide. Extra challenges are posed by high energy, high intensity machines and low energy low intensity accelerators. For these applications, existing diagnostics are no longer suitable due to the high power of the beam or the very low intensity. In addition, many other accelerators, from medical to industrial will benefit from a noninvasive, real time beam profile monitor. In this paper we present a new beam profile monitor with a novel design for the nozzle and skimmer configuration to generate a supersonic gas jet meeting ultrahigh vacuum conditions and we describe the first results for such a beam profile monitor at the Cockcroft Institute. This monitor is able to measure two-dimensional profiles of the particle beam while causing negligible disturbance to the beam or to the accelerator vacuum. The ultimate goal for this diagnostic is to provide a versatile and universal beam profile monitor suitable for measuring any beams.

SPIE Digital Library Proceedings

Coherent synchrotron radiation (CSR) is crucial for the development of powerful ultrashort light sources. We present a mechanism for generating CSR in the form of generalised superradiance, based on surface plasmon polaritons (SPPs), which are resonantly excited on a solid, near-critical-density inner surface of a microtube. A high-intensity, circularly polarized laser pulse, propagating along the microtube axis, efficiently couples the cylindrical SPP modes. This process creates azimuthally structured, rotating electromagnetic fields. These rotating fields subsequently confine, modulate, and directly accelerate surface electrons to emit CSR in the Vavilov-Cherenkov angle. We further demonstrate that by improving the azimuthal symmetry of these electrons, the helical modulation enables CSR emission across all azimuthal directions in the form of isolated harmonics, significantly enhancing radiation intensity even when full coherence is imperfect. Our full 3D particle-in-cell simulations indicate this scheme can generate x-rays with coherence enhanced by up to 2 orders of magnitude compared to incoherent emission. The challenges to experimentally realize this scheme are discussed, including the need for high-contrast lasers to prevent preplasma formation and the demanding tolerances for microtube fabrication and alignment, while these challenges are not beyond the scope of existing or near-future experimental capabilities.