The Insulation Vacuum Barrier for the Large Hadron Collider (LHC) Magnet Cryostats

The sectorisation of the insulation vacuum of the LHC magnet cryostats, housing the superconducting magnets, which operate in a 1.9 K superfluid helium bath, is achieved by means of vacuum barriers. Each vacuum barrier is a leak-tight austenitic stainless steel thin-wall structure, mainly composed of large diameter (between 0.6 m and 0.9 m) bellows and concentric corrugated cylinders. It is mounted in the Short Straight Section (SSS) [1], between the magnet helium enclosure and the vacuum vessel. This paper presents the design of the vacuum barrier, concentrating mostly on its expected thermal performance, to fulfil the tight LHC heat in-leak budgets. Pressure and leak test results, confirming the mechanical design of two prototypes manufactured in industry, and the preparation of one of these vacuum barriers for cryogenic testing in an SSS prototype, are also mentioned

CONTRIBUTION A L'OPTIMISATION DES PHOTOCATHODES TRIALCALINES SEMI-TRANSPARENTES

Dans la plupart des dispositifs utilisant des photoémetteurs, le rendement quantique de la photocathode détermine les performances ultimes du système. Nous examinons ici les photocathodes multialcalines du type (SbNa2K, Cs). Des sensibilités photoélectriques de 220 µA/lm ont été obtenues avec des photocathodes de 300 Å d'épaisseur. Dans ce cas le rendement quantique vrai atteint 50 % pour une radiation incidente λ comprise entre 400 et 500 Å. Pour des couches plus épaisses (1 200 Å) on a pu obtenir des photocathodes semi-transparentes beaucoup plus sensibles allant jusqu'à 705 µA/lmIn most of the photoelectric tubes the radiant sensitivity of the photoemissive layer determines the ultimate performances of the system. In this paper we consider the multialcaline (SbNa2K, Cs) photocathodes. Considering a photoemissive layer 300 Å thick, it is possible to obtain 220 µA/lm. In this case the actual photoelectric yield reaches 50 % for a wavelength λ of incident light between 400 and 550 nm. With a thicker photocathode (1 200 Å) we have obtained a much better sensitivity which is 705 µA/lm in semi transparent mode

Progress on the ITER H&D EC Upper Launcher Steering-Mirror Control System

The ITER Heating and Current Drive Upper Launcher (H&CD EC UL) uses a pneumomechanical steering-mirror assembly (SMA) to steer the RF beams for their deposition in the appropriate location in the plasma to control magnetohydrodynamic activity (neoclassical tearing modes (NTMs) and sawtooth oscillations). For NTM stabilization, the mirror rotation needs to be controlled to an accuracy that is better than 0.1 degrees. A 10 degrees . s(-1) mirror steering speed is also required. To assess the performance of the two SMA prototypes that have been manufactured, a test stand that reproduces the expected pneumatic configuration of the UL has been built. So far, only the first SMA prototype has been tested, and tests on the second prototype are foreseen in the 2009-2010 period. The steering angle of the mirror will be deduced from the pressure applied to the mechanism since there is no in situ angle measurement at present. An "off-the-shelf" commercial servo valve with a proportional-integral-derivative controller has been used to control the pressure with good results for the switching cycle. These tests show that a more advanced controller will be required to attain the desired accuracy and speed for the modulation cycles

Can cellular transplantation improve function in doxorubicin-induced heart failure?

International audienceBackground: Transplantation of fetal cardiomyocytes has been shown to improve function of regionally infarcted myocardium, but its effects on global heart failure are still unknown.Methods and results: Heart failure was induced in female mice by intraperitoneal injection of doxorubicin (2 mg/kg twice per week over 2 cycles of 2 weeks separated by a 2-week drug-free period). One week after the end of treatment, left ventricular function was assessed by transthoracic echocardiography (baseline). Animals were then randomized into 3 groups: The treated group (n = 12) received an intramyocardial injection of fetal cardiomyocytes (1 x 10(6) in 10 microL) harvested from transgenic mice expressing the gene of beta-galactosidase, the control group (n = 15) received an equivalent volume of culture medium alone, and 10 sham mice had no surgery. Two weeks and 1 month after transplantation, function was again assessed echocardiographically. At baseline, fractional shortening was not significantly different between the 3 groups. It then significantly increased in cell-treated mice at 2 weeks and 1 month after transplantation (P < 0.002 and P < 0.03 versus baseline, respectively), whereas it did not change in untreated animals. Transplanted cells could not be identified by beta-galactosidase activity or presence of Y chromosome (with 1 exception).Conclusions: Cellular transplantation can improve function of globally failing hearts by a mechanism that might not necessarily involve the sustained presence of transplanted cells but rather the effects of cardioprotective factors released by them