Stretched-Wire Techniques and Measurements for the Alignment of a 15GHz RF-BPM for CLIC

For the Compact LInear Collider (CLIC) project at CERN, maintaining low emittance beams, as they are transported along the two independent 10-20 km long main linacs, is crucial. The beam trajectory therefore has to be very well aligned to the magnetic centre of the quadrupole magnets. A series of microwave cavity beam position monitors (BPM) is foreseen to detect the position of the beam along the main linacs to precisely monitor the beam trajectory in the circular beam pipe of only 8 mm diameter. The PACMAN project aims to demonstrate the pre-alignment of the magnetic field of a main CLIC quadrupole with the electro-magnetic centre of a 15 GHz RF-BPM to the required sub-micron accuracy. This paper focuses on stretched-wire measurements of a CLIC Test Facility (CTF) cavity BPM, to locate its electrical centre. Details of two measurement methods are discussed: RF signal excitation of the wire and analysis of RF signal transfer through the slot-coupled waveguides of the cavity, using the stretched wire as a passive target. This contribution will present the theory behind these measurements, their electromagnetic analysis and first, preliminary experimental results

CLIC BPM-Quadrupole pre-alignment in the frame of the PACMAN Marie Curie Action

The Compact Linear Collider (CLIC) requires a low emittance beam transport and preservation, thus a precise control of the beam orbit along up to 50 km of the accelerator components in the sub- μm regime is required. Within the PACMAN (Particle Accelerator Components Metrology and Alignment to the Nanometer Scale) Ph.D. training action a study with the objective to pre-align the electrical center of a 15 GHz cavity BPM to the magnetic center of the main beam quadrupole is initiated. Goals, first ideas, some technical details, as well as the challenges of this stretched wire based method will be presented, including calculations, simulations, and first preliminary measurements [1]

ELECTROMAGNETIC FIELD PRE-ALIGNMENT OF THE COMPACT LINEAR COLLIDER (CLIC) ACCELERATING STRUCTURE WITH HELP OF WAKEFIELD MONITOR SIGNALS

Abstract The CLIC project, currently under study at CERN is an electron-positron collider at 3 TeV centre-of-mass energy and luminosity of 2*10 34 cm -2 s -1 . Achieving such luminosity requires a beam dimension of 1 nm in the vertical plane and high beam stability. The TD24 is a traveling wave structure operating at 12 GHz designed to reach 100 MV/m at constant gradient. It consists of two coupling cells and 24 disks. The RF is coupled from cell to cell though an iris of 5.5 mm. To minimize the occurrence of wake-fields and minimize the emittance growth Δε y below 5%, the pre-alignment precision of the electrical centre of the accelerating structure (AS) on its support has to be better than 7 µm. Following, the AS is actively aligned with beam using the wakefield monitor (WFM) signals, with a resolution of 3.5 µm. A test bench for laboratory measurements has been designed and exploits the asymmetry created by RF scattering parameters by an off-centre conductive wire, stretched to locate the electromagnetic centre of the AS. Simulations and preliminary measurement results are presented

A systematic review on the cost evaluation of two different laparoscopic surgical techniques among 996 appendectomies from a single center

Acute appendicitis is one of the main indications for urgent surgery representing a high-volume procedure worldwide. The current spending review in Italy (and not only in this country) affects the health service and warrants care regarding the use of different surgical devices. The aim of our study is to perform a cost evaluation, comparing the use of endoloops and staplers in complicated acute appendicitis (phlegmonous and gangrenous), taking into consideration the cost of the device in relation to the management of any associated postoperative complications. We retrospectively evaluated 996 laparoscopic appendectomies of adult patients performed in the Emergency General Surgery—St. Orsola University Hospital in Bologna (Italy). Surgical procedures together with the related choice of using endoloops or staplers were performed by attending surgeons or resident surgeons supervised by a tutor. A systematic review was performed to compare our outcomes with those reported in the literature. In our experience, the routine use of endoloop leads to a real estimated saving of 375€ for each performed laparoscopic appendectomy, even considering post-operative complications. Comparing endoloop and stapler groups, the total number of complications is significantly lower in the endoloop group. Our systematic review confirmed these findings even if the superiority of one technique has not been proved yet. Our analysis shows that the routine use of endoloop is safe in most patients affected by acute appendicitis, even when complicated, and it is a cost-effective device even when taking into consideration extra costs for potential post-operative complications

Debris-Filled Duodenal Diverticulum and Lemmel's Syndrome

We report a case of a 73-year-old woman affected by Lemmel's syndrome, a rare type of obstructive jaundice caused by a periampullary duodenal diverticulum. The patient was admitted to the Emergency Department for pneumonia associated with mild epigastric pain and vomiting. While hospitalized for antibiotic treatment, the appearance of jaundice led us to discover a periampullary duodenal diverticulum by endoscopy and CT scan. The jaundice was successfully managed endoscopically with removal of food debris from the diverticulum

New solution for the high accuracy alignment of accelerator components

Several state-of-the-art metrology measurement methods have been investigated and combined for a fiducialization of accelerator components in the micrometric regime. The PACMAN project at CERN applied stretched-wire measurement methods to Compact Linear Collider quadrupole and cavity beam position monitor prototypes, to locate their magnetic, respectively, electromagnetic, axis using a dedicated test stand and to determine the position of the wire with respect to external alignment targets (fiducials) testing different methods, such as coordinate measuring machine measurements and microtriangulation. Further studies have been performed using a nanopositioning system, verifying the absolute accuracy and repeatability of the fiducialization method within a few micrometers

A novel alpha-D-galactosynthase from Thermotoga maritima converts beta-D-galactopyranosyl azide to alpha-galacto-oligosaccharides

The large-scale production of oligosaccharides is a daunting task, hampering the study of the role of glycans in vivo and the testing of the efficacy of novel glycan-based drugs. Glycosynthases, mutated glycosidases that synthesize oligosaccharides in high yields, are becoming important chemo-enzymatic tools for the production of oligosaccharides. However, while beta-glycosynthase can be produced with a rather well-established technology, examples of alpha-glycosynthases are thus far limited only to enzymes from glycoside hydrolase 29 (GH29), GH31 and GH95 families. alpha-l-Fucosynthases from GH29 use convenient glycosyl azide derivatives as a strategic alternative to glycosyl fluoride donors. However, the general applicability of this method to other alpha-glycosynthases is not trivial and remains to be confirmed. Here, beta-d-galactopyranosyl azide was converted to alpha-galacto-oligosaccharides with good yields and high regioselectivity, catalyzed by a novel alpha-galactosynthase based on the GH36 alpha-galactosidase from the hyperthermophilic bacterium Thermotoga maritima. These results open a new avenue to the practical synthesis of biologically interesting alpha-galacto-oligosaccharides and demonstrate more widespread use of beta-glycosyl-azide as donors, confirming their utility to expand the repertoire of glycosynthase