Conference Paper

Progress in tune, coupling, and chromaticity measurement and feedback during RHIC run 7

BNL, Upton
DOI: 10.1109/PAC.2007.4440748 Conference: Particle Accelerator Conference, 2007. PAC. IEEE
Source: IEEE Xplore


Tune feedback was first implemented in RHIC in 2002, as a specialist activity. The transition of the tune feedback system to full operational status was impeded by dynamic range problems, as well as by overall loop instabilities driven by large coupling. The dynamic range problem was solved by the CERN development of the Direct Diode Detection Analog Front End [1]. Continuous measurement of all projections of the betatron eigenmodes made possible the world's first implementation of coupling feedback during beam acceleration [2,3], resolving the problem of overall loop instabilites. Simultaneous tune and coupling feedbacks were utilized as specialist activities for ramp development during the 2006 RHIC run. At the beginning of the 2007 RHIC run there remained two obstacles to making these feedbacks fully operational in RHIC - chromaticity measurement and control, and the presence of strong harmonics of the power line frequency in the betatron spectrum [4]. We report on progress in tune, coupling, and chromaticity measurement and feedback, and discuss the relevance of our results to LHC commissioning.

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    • "From the 2004 run through the 2008 run, a good amount of progress was made, but an expert was still required to operate the BBQ system. Various problems were encountered [4] such as mains interference, 'anomalous' beam transfer functions, and 'tune scalloping' which often interfered with acquiring a successful tune lock on the beam. Prototype boards and chassis were fabricated to try to help solve some of these problems. "
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    ABSTRACT: Throughout RHIC Run-9 (polarized protons) and Run-10 (gold), numerous modifications to the Baseband Tune (BBQ) system were made. Hardware and software improvements resulted in improved resolution and control, allowing the system to overcome challenges from competing 60Hz mains harmonics, other spectral content, and other beam issues. Test points from the Analog Front End (AFE) were added and connected to diagnostics that allow us to view signals, such as frequency spectra on a Sr785 dynamic signal analyser (DSA), in real time. Also, additional data can now be logged using a National Instruments DAQ (NI-DAQ). Development time using tune feedback to obtain full-energy beams at RHIC has been significantly reduced from many ramps over a few weeks, to just a few ramps over several hours. For many years BBQ was an expert-only system, but the many improvements allowed BBQ to finally be handed over to the Operations Staff for routine control.
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    ABSTRACT: The unprecedented intensity and energy of the LHC proton beams will require an excellent control of the transverse beam dynamics in order to limit particle loss in the superconducting systems. Due to restricted tolerances of the machine protection system and a tight beam emittance blow-up budget only small beam excitation is allowed, making precise measurements of the transverse beam parameters very challenging. This overview outlines the systems measuring the tune, chromaticity and betatron coupling of the LHC beams, referred to in the paper as the transverse diagnostic systems. As manual correction of the parameters may reach its limit with respect to required precision and expected time scales, the LHC is the first proton collider that can be safely and reliably operated only with automatic feedback systems for controlling transverse beam dynamics. An outline of these feedback systems is also presented.
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    ABSTRACT: This year (2008) deuterons and gold ions were collided in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) for the first time since 2003. The setup and performance of the collider for the 2008 run is reviewed with a focus on improvements that have led to an order of magnitude increase in luminosity over that achieved in the 2003 run.