Preliminary injector, accelerator, and beamline design for rf-linac-driven XUV free-electron lasers

The proposed Los Alamos National Laboratory XUV free-electron laser (FEL) facility requires exceptional beam quality at high peak currents. Although the beam quality needed for a demonstration machine lasing at 50 nm is not far from what can be expected with extensions of present linacs to higher energy, conventional injector technology will not meet the requirements needed for lasing at 12 or 4 nm. We have conceived a preliminary injector and accelerator design that will meet these requirements. Using the Los Alamos photoelectric injector, it appears that normalized 90% emittances of 24 ..pi.. dot mm dot mrad can be attained in a relatively straightforward manner, and emittances down to 4 ..pi.. doe mm dot mrad are possible. Beamline simulations have been performed with the particle-pushing code PARMELA, using particle-dump inputs from the particle-in-cell code ISIS. The latter models the photoelectric gun up to the range between 0.75 and 1 MeV. Designs including electron guns with Pierce geometries have also been studied. Using an injector with a large planar-cathode Pierce gun seems to satisfy the 50-nm lasing requirements. In addition, other beamline questions have been studied. Beamline bends have been designed that are achromatic and nearly isochronous. The threshold for cumulative beam breakup and the emittance growth caused by transverse resistive-wall beam instability have been calculated. Finally, we discuss the advantages and disadvantages of building a straight-line machine versus a recycling machine, including recycling instability current levels. 11 refs., 16 figs

Final Report 200 MW L-Band Annular Beam Klystron for Accelerators

This program developed a 200 MW, 1.3 GHz, Annular Beam Klystron (ABK) for accelerator systems. An ABK provides lower impedance than a conventional klystron, making it possible to produce higher RF powers with lower voltages. With a higher power per unit, fewer klystrons would be required for a large accelerator. Lower voltage also simplifies and reduces the cost of the power supply system. Both features will significantly lower the cost of an RF system. This device operates at 475 kV. The klystron uses a magnetron injection gun producing 1100 A in one microsecond pulses. Power is extracted into fundamental rectangular waveguide through two output windows. The predicted gain is approximately 45 dB with estimated efficiency of 45%. The klystron was assembled, but no facility was available for testing. Consequently, no high power performance measurements are available. Because the assembled klystron is approximately 15 feet long, it was disassembled for storage. It can be reassembled should a use materialize

High-Power, High-Frequency, Annular-Beam Free-Electron Maser

The authors have developed a 15--17 GHz free electron maser (FEM) capable of producing high power pulses with a phase stability appropriate for linear collider applications. The electron beam source is a 1 {micro}s, 800 kV, 5 kA, 6-cm-dia annular electron beam machine called BANSHEE. The beam interacts with the TM{sub 02} mode Raman FEM amplifier in a corrugated cylindrical waveguide where the beam runs close to the interaction device walls to reduce the power density in the fields. They studied the phase stability by analyzing the dispersion relation for an axial FEL, in which the rf field was transversely wiggled and the electron trajectories were purely longitudinal. Detailed particle-in-cell simulations demonstrated the transverse wiggling of the rf mode and the axial FEL interaction and explicit calculations of the growing root of the dispersion relation are included to verify the phase stability

Space-Borne Electron Accelerator Design

Renewed interest in active experiments with relativistic particle beams in space has led to the development of solid-state radio-frequency (RF) linear accelerators (linac) that can deliver MeV electron beams but operate with low-voltage DC power supplies. The solid-state RF amplifiers used to drive the accelerator are known as high-electron mobility transistors (HEMTs), and at C-band (5–6 GHz) are capable of generating up to 500 watts of RF power at 10% duty factor in a small package, i.e., the size of a postage stamp. In operation, the HEMTs are powered with 50 V DC as their bias voltage; they thus can tap into the spacecraft batteries or electrical bus as the primary power source. In this paper we describe the initial testing of a compact space-borne RF accelerator consisting of individual C-band cavities, each independently powered by a gallium nitride (GaN) HEMT. We show preliminary test results that demonstrate the beam acceleration in a single C-band cavity powered by a single HEMT operating at 10% duty factor. An example of active beam experiments in space that could benefit from the HEMT-powered accelerators is the proposed Magnetosphere-Ionosphere Connection (CONNEX) experiment (Dors et al., 2017)

Inflammatory cytokines and aromatase inhibitor-associated musculoskeletal syndrome: a case–control study

The aromatase inhibitor (AI)-associated musculoskeletal syndrome (AIMSS) occurs in approximately 50% of AI-treated patients. Inflammatory mediators are associated with oestrogen signalling and may change with oestrogen depletion. We hypothesised that AIMSS may be associated with changes in circulating inflammatory markers

Gene expression and in situ protein profiling of candidate SARS-CoV-2 receptors in human airway epithelial cells and lung tissue

In December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)emerged, causing the coronavirus disease 2019 (COVID-19) pandemic. SARS-CoV, the agent responsible for the 2003 SARS outbreak, utilises angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) host molecules for viral entry. ACE2 and TMPRSS2 have recently been implicated in SARS-CoV-2 viral infection. Additional host molecules including ADAM17, cathepsin L, CD147 and GRP78 may also function as receptors for SARS-CoV-2.To determine the expression and in situ localisation of candidate SARS-CoV-2 receptors in the respiratory mucosa, we analysed gene expression datasets from airway epithelial cells of 515 healthy subjects, gene promoter activity analysis using the FANTOM5 dataset containing 120 distinct sample types, single cell RNA sequencing (scRNAseq) of 10 healthy subjects, proteomic datasets, immunoblots on multiple airway epithelial cell types, and immunohistochemistry on 98 human lung samples.We demonstrate absent to lowACE2promoter activity in a variety of lung epithelial cell samples andlowACE2gene expression in both microarray and scRNAseq datasets of epithelial cell populations.Consistent with gene expression, rare ACE2 protein expression was observed in the airway epithelium and alveoli of human lung, confirmed with proteomics. We present confirmatory evidence for the presence ofTMPRSS2, CD147 and GRP78 protein in vitro in airway epithelial cells and confirm broad in situ protein expression of CD147 and GRP78 in the respiratory mucosa. Collectively, our data suggest the presence of a mechanism dynamically regulating ACE2 expression inhuman lung, perhaps in periods of SARS-CoV-2 infection, and also suggest that alternative receptors forSARS-CoV-2 exist to facilitate initial host cell infection

Using a hybrid-fluid model to simulate the ion-hose instability in long-pulse electron linacs

A numerical model of the ion-hose instability for long-pulse electron linacs is presented, where the ion motion is represented by fluid parameters. In order to gain extra numerical stability, the fluid behavior of the ions is evolved via particle-in-cell (PIC) techniques. This methodology provides a much faster simulation than a full PIC calculation, allowing for end-to-end simulations of the ion-hose instability in actual linear accelerator configurations. After the description of the simulation model and some simple test cases, the instability is analyzed for a variety of nominal accelerator transport conditions. Simulations of the instability are provided for sections of the DARHT long-pulse accelerator that show different growth regimes of the instability. We find that large-amplitude growth is possible in accelerator and transport regions lacking uniform external focusing, for electron pulse lengths of 2   μsec and longer

Rippled beam free electron Laser Amplifier

A free electron laser amplifier provides a scalloping annular electron beam that interacts with the axial electric field of a T{sub 0n} mode. A waveguide defines an axial centerline and . A solenoid arranged about the waveguide produces an axial constant magnetic field within the waveguide. An electron beam source outputs a annular electron beam that interacts with the axial magnetic field to have an equilibrium radius and a ripple radius component having a variable radius with a ripple period along the axial centerline. An rf source outputs an axial electric field that propagates within the waveguide coaxial with the electron beam and has a radial mode that interacts at the electron beam at the equilibrium radius component of the electron beam