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The TOTEM experiment has been designed to measure the total proton-proton cross section and to study the elastic and diffractive scattering at the LHC energy. The measurement requires detecting protons at distances as small as 1 mm from the beam center: TOTEM uses Roman Pots, movable beam pipe insertions, hosting silicon detectors. In the first period of LHC operation no relevant problems were detected with Roman Pots retracted or inserted during special runs. However, when operating the LHC with high intensity beams, impedance induced heating has been observed during the Roman Pots insertion. In order to be compatible with the higher LHC beam current foreseen after the LS1, a new version of the Roman Pot has been proposed and optimized with respect to the beam coupling impedance. In this work we present the bench impedance measurements carried out on the new Roman Pot prototype. Single and double wire measurements, as well as probe measurements, were performed in order to detect possible harmful resonant modes. The laboratory setup has been as well simulated with the help of CST Particle Studio in order to benchmark the measurement results. Measurements and simulations are in close agreement confirming the equipment compatibility with the LHC requirements for safe operation.

This article describes a study performed on one of the CERN-SPS vertical rotational wire scanners in order to investigate the breakage of the wire, which occurred on several occasions during operation in 2012. The thermionic emission current of the wire was measured to evaluate temperature changes, and was observed to rise significantly as the wire approached the ultimate LHC beam in the SPS, indicating the possibility of strong coupling between the beam’s electromagnetic field and the wire. Different laboratory measurements, complemented by CST Microwave Studio simulations, have therefore been performed to try and understand the RF modes responsible for this heating. These results are presented here, along with the subsequent modifications adopted on all of the operational SPS wire scanners.

In the accelerator domain there is a need of integrating industrial devices and creating control and monitoring applications in an easy and yet structured way. The LabVIEW-RADE framework provides the method and tools to implement these requirements and also provides the essential integration of these applications into the CERN controls infrastructure. We present three examples of applications of different nature to show that the framework provides solutions at all three tiers of the control system, data access, process and supervision. The first example is a remotely controlled alignment system for the LHC collimators. The collimator alignment will need to be checked periodically. Due to limited access for personnel, the instruments are mounted on a small train. The system is composed of a PXI crate housing the instrument interfaces and a PLC for the motor control. We report on the design, development and commissioning of the system. The second application is the renovation of the PS beam spectrum analyzer where both hardware and software were renewed. The control application was ported from Windows to LabVIEW-Real Time. We describe the technique used for a full integration into the PS consoles.The third example is a control and monitoring application for the “CLIC two beam test stand”. The application accesses CERN front-end equipment through the CERN middleware, CMW, and provides many different ways to view the data. We conclude with an evaluation of the framework based on the three examples and indicate new areas of improvement and extension.

Some of the upgrade scenarios of the high-luminosity LHC require large intensity per bunch from the injector chain. Single bunch beams with intensities of up to 3.5 to 4e11 p/b and nominal emittances were successfully produced in the PS Complex and delivered to the SPS in 2010. This contribution presents results of studies with this new intense beam in the SPS to probe single bunch intensity limitations with nominal gamma transition. In particular, the vertical Transverse Mode Coupling Instability (TMCI) threshold with low chromaticity was observed at 1.6e11 p/b for single nominal LHC bunches in the SPS. With increased vertical chromaticity, larger intensities could be injected, stored along the flat bottom and accelerated up to 450 GeV/c. However, significant losses and/or transverse emittance blow up were then observed. Longitudinal and transverse optimization efforts in the PSB, PS and SPS were put in place to minimize this beam degradation and succeeded to obtain single 2.5e11 p/b LHC type bunches with satisfying parameters at extraction of the SPS.