Overview of fast particle experiments in the first MAST Upgrade experimental campaigns

MAST-U is equipped with on-axis and off-axis neutral beam injectors (NBI), and these external sources of super-Alfvénic deuterium fast-ions provide opportunities for studying a wide range of phenomena relevant to the physics of alpha-particles in burning plasmas. The MeV range D-D fusion product ions are also produced but are not confined. Simulations with the ASCOT code show that up to 20% of fast ions produced by NBI can be lost due to charge exchange (CX) with edge neutrals. Dedicated experiments employing low field side (LFS) gas fuelling show a significant drop in the measured neutron fluxes resulting from beam-plasma reactions, providing additional evidence of CX-induced fast-ion losses, similar to the ASCOT findings. Clear evidence of fast-ion redistribution and loss due to sawteeth (ST), fishbones (FB), long-lived modes (LLM), Toroidal Alfvén Eigenmodes (TAE), Edge Localised Modes (ELM) and neoclassical tearing modes (NTM) has been found in measurements with a Neutron Camera (NCU), a scintillator-based Fast-Ion Loss Detector (FILD), a Solid-State Neutral Particle Analyser (SSNPA) and a Fast-Ion Deuterium-α (FIDA) spectrometer. Unprecedented FILD measurements in the range of 1–2 MHz indicate that fast-ion losses can be also induced by the beam ion cyclotron resonance interaction with compressional or global Alfvén eigenmodes (CAEs or GAEs). These results show the wide variety of scenarios and the unique conditions in which fast ions can be studied in MAST-U, under conditions that are relevant for future devices like STEP or ITER

Diagnostic weight functions in constants-of-motion phase-space

The fast-ion phase-space distribution function in axisymmetric tokamak plasmas is completely described by the three constants of motion: energy, magnetic moment and toroidal canonical angular momentum. In this work, the observable regions of constants-of-motion phase-space, given a diagnostic setup, are identified and explained using projected velocities of the fast ions along the diagnostic lines-of-sight as a proxy for several fast-ion diagnostics, such as fast-ion Dα spectroscopy, collective Thomson scattering, neutron emission spectroscopy and gamma-ray spectroscopy. The observable region in constants-of-motion space is given by a position condition and a velocity condition, and the diagnostic sensitivity is given by a gyro-orbit and a drift-orbit weighting. As a practical example, 3D orbit weight functions quantifying the diagnostic sensitivity to each point in phase-space are computed and investigated for the future COMPASS-Upgrade and MAST-Upgrade tokamaks

Apstatin, a selective inhibitor of aminopeptidase P, reduces myocardial infarct size by a kinin-dependent pathway

1. Inhibitors of the angiotensin converting enzyme (ACE) have been shown to exert their cardioprotective actions through a kinin-dependent mechanism. ACE is not the only kinin degrading enzyme in the rat heart. 2. Since aminopeptidase P (APP) has been shown to participate in myocardial kinin metabolism to the same extent as ACE, the aims of the present study were to investigate whether (a) inhibition of APP leads to a reduction of myocardial infarct size in a rat model of acute ischaemia and reperfusion, (b) reduction of infarct size is mediated by bradykinin, and (c) a combination of APP and ACE inhibition leads to a more pronounced effect than APP inhibition alone. 3. Pentobarbital-anaesthetized rats were subjected to 30 min left coronary artery occlusion followed by 3 h reperfusion. The APP inhibitor apstatin, the ACE-inhibitor ramiprilat, or their combination were administered 5 min before ischaemia. Rats receiving HOE140, a specific B(2) receptor antagonist, were pretreated 5 min prior to enzyme inhibitors. Myocardial infarct size (IS) was determined by tetrazolium staining and expressed as percentage of the area at risk (AAR). 4. IS/AAR% was significantly reduced in rats that received apstatin (18±2%), ramiprilat (18±3%), or apstatin plus ramiprilat (20±4%) as compared with those receiving saline (40±2%), HOE (43±3%) or apstatin plus HOE140 (49±4%). 5. Apstatin reduces IS in an in vivo model of acute myocardial ischaemia and reperfusion to the same extent than ramiprilat. Cardioprotection achieved by this selective inhibitor of APP is mediated by bradykinin. Combined inhibition of APP and ACE did not result in a more pronounced reduction of IS than APP-inhibition alone

Orbit tomography in constants-of-motion phase-space

Tomographic reconstructions of a 3D fast-ion constants-of-motion phase-space distribution function are computed by inverting synthetic signals based on projected velocities of the fast ions along the diagnostic lines of sight. A spectrum of projected velocities is a key element of the spectrum formation in fast-ion D-alpha spectroscopy, collective Thomson scattering, and gamma-ray and neutron emission spectroscopy, and it can hence serve as a proxy for any of these. The fast-ion distribution functions are parameterised by three constants of motion, the kinetic energy, the magnetic moment and the toroidal canonical angular momentum. The reconstructions are computed using both zeroth-order and first-order Tikhonov regularisation expressed in terms of Bayesian inference to allow uncertainty quantification. In addition to this, a discontinuity appears to be present in the solution across the trapped-passing boundary surface in the three-dimensional phase space due to a singularity in the Jacobian of the transformation from position and velocity space to phase space. A method to allow for this apparent discontinuity while simultaneously penalising large gradients in the solution is demonstrated. Finally, we use our new methods to optimise the diagnostic performance of a set of six fans of sightlines by finding where the detectors contribute most complementary diagnostic information for the future COMPASS-Upgrade tokamak.</p