NONDISTRUCTIVE TESTING INSTRUMENT OF DISHED Nb SHEETS FOR SRF CAVITIES BASED ON SQUID TECHNOLOGY

Abstract The performance of superconducting RF cavities used in accelerators can be enhanced by detecting micro particles and inclusions which are the most serious source of performance degradation. These defects prevent the cavities from reaching the highest possible accelerating fields. We have developed a SQUID scanning system based on eddy current technique that allows the scanning of curved Nb samples. This SQUID scanning system successfully located Tantalum defects about 100 zm diameter in a flat Nb sample and was able to also locate the defects in a cylindrical surface sample. Most importantly, however, the system successfully located the defects on the backside of the flat sample and curved sample, both 3-mm thick. This system can be used for the inspection and detection of such defects during SRF cavity manufacturing

In situ high-temperature XRD and FTIR investigation of hohmannite, a water-rich Fe-sulfate, and its decomposition products

The thermal dehydration of hohmannite, Fe 2 [O(SO 4 ) 2 ]·8H 2 O, a secondary iron-bearing hydrous sulfate, was investigated by in situ high-temperature X-ray powder diffraction and in situ high-temperature Fourier transform infrared spectroscopy. Combination of the data from both techniques allowed determining the stability fields and reaction paths for this mineral and its high temperature products. Five main dehydration/transformation steps for hohmannite have been identified in the heating range of 25-800 °C. Temperature behavior of the different phases was analyzed, and the heating-induced structural changes are discussed

Using leg muscles as shock absorbers : theoretical predictions and experimental results of human drop landing

The use of muscles as power dissipators is investigated in this study, both from the modellistic and the experimental points of view. Theoretical predictions of the drop landing manoeuvre for a range of initial conditions have been obtained by accounting for the mechanical characteristics of knee extensor muscles, the limb geometry and assuming maximum neural activation. Resulting dynamics have been represented in the phase plane (vertical displacement versus speed) to better classify the damping performance. Predictions of safe landing in sedentary subjects were associated to dropping from a maximum (feet) height of 1.6-2.0 m (about 11 m on the moon). Athletes can extend up to 2.6-3.0 m, while for obese males (m = 100 kg, standard stature) the limit should reduce to 0.9-1.3 m. These results have been calculated by including in the model the estimated stiffness of the 'global elastic elements' acting below the squat position. Experimental landings from a height of 0.4, 0.7, 1.1 m (sedentary males (SM) and male (AM) and female (AF) athletes from the alpine ski national team) showed dynamics similar to the model predictions. While the peak power (for a drop height of about 0.7 m) was similar in SM and AF (AM shows a +40% increase, about 33 W/kg), AF stopped the downward movement after a time interval (0.219 \ub1 0.030 s) from touch-down 20% significantly shorter than SM. Landing strategy and the effect of anatomical constraints are discussed in the paper