Rhodri Jones

TOWARDS A ROBUST PHASE LOCKED LOOP TUNE FEEDBACK SYSTEM

Attempts to introduce a reliable tune feedback loop at RHIC (BNL) [1] have been thwarted by two main problems, namely transition crossing and betatron coupling. The problem of transition crossing is a dynamic range problem, resulting from the increase in the revolution content of the observed signal as the bunch length becomes short and from the fast orbit changes that occur during transition. The dynamic range issue is being addressed by the development of a baseband tune measurement system [2] as part of the US LHC Accelerator Research Program (US-LARP). This paper will focus on the second problem, showing how a phase locked loop (PLL) tune measurement system can be used to continuously measure global betatron coupling, and in so doing allow for robust tune measurement and feedback in the presence of coupling.

First results from the Jetset RICH detector

The Jetset internal target experiment at LEAR is devoted to the study of hadronic resonances in the channel pp → φφ within the invariant mass range 2.0–2.4 GeV/c2. Without a magnet for momentum analysis, the kinematic reconstruction of the final state has relied upon track directions and dEdx. In 1992 a compact RICH detector based upon a quartz radiator and a unique cellular MWPC operated with TMAE was installed in the forward region of the experiment. Data with the RICH in operation were taken during the two Jetset running periods that year, with performance in agreement with Monte Carlo simulations. Initial results from the analysis of this data are presented.

LHC Beam Instrumentation Status and Challenges

This presentation will aim to give an overview of the beam instrumentation foreseen for the LHC. A brief summary of the main systems will be followed by a discussion of areas where there have been recent advances, such as in the measurement of tune, chromaticity and coupling, or where there are still outstanding issues. The instrumentation to be delivered as part of the US LHC Accelerator Research Program (US‐LARP) will also be highlighted.

LHC Orbit Stabilisation Tests at the SPS

The LHC, presently being built at CERN, is the first proton collider that requires a continuous orbit control for safe and reliable machine operation. A realistic test of the orbit feedback system was performed in 2004 using already-present LHC instrumentation and infrastructure on a 270GeV coasting beam in the Super-Proton-Synchrotron. It has been demonstrated that the chosen feedback architecture can stabilise the beam better than 10 micrometres and is essentially limited by the noise of the beam position monitor and the bandwidth of the corrector magnets. The achieved orbit stability is comparable to those found at modern light sources and gives enough operational margin with respect to the requirements of the LHC Cleaning System (70 µ m). Estimates for the longterm drifts and achievable stability will be presented based on the experimental results.