We report on the observation of incoherent Cherenkov radiation emitted by a 5.3 GeV positron beam circulating in the Cornell electron-positron storage ring as the beam passes in the close vicinity of the surface of a fused silica radiator (i.e., at a distance larger than 0.8 mm). The shape of the radiator was designed in order to send the Cherenkov photons towards the detector, consisting of a compact optical system equipped with an intensified camera. The optical system allows both the measurements of 2D images and angular distribution including polarization study. The corresponding light intensity has been measured as a function of the distance between the beam and the surface of the radiator and has shown a good agreement with theoretical predictions. For highly relativistic particles, a large amount of incoherent radiation is produced in a wide spectral range. A light yield of 0.8×10^{-3} photon per particle per turn has been measured at a wavelength of 600±10 nm in a 2 cm long radiator and for an impact parameter of 1 mm. This will find applications in accelerators as noninvasive beam diagnostics for both leptons and hadrons.
The two eigentunes Q I and Q II , two eigenmode amplitude ratios R I and R II , and two eignmode phase differences ∆φ I and ∆φ II , are defined as the coupling observables for the linear weak difference betatron coupling. Simulations were carried out to investigate their behaviors in global decoupling scans. It was found that the amplitude ratios R I,II are more sensitive than the tune split when the decoupling scan is approaching the global uncoupled point, and that the phase differences ∆φ I,II tell the right global decoupling direction, the right strength combination of the skew quadrupoles or families. The analytical solution to these six coupling observables is calculated through both the strict matrix approach and the perturbation Hamiltonian approach. The constant phase differences in the right decoupling direction hint a possible global decoupling phase loop. Dedicated beam experiments were carried out at the Relativistic Heavy Ion Collider (RHIC). The preliminary results from the beam experiments are presented. These six parameters can be used for the global decoupling in feedback mode, especially on the non-stop energy ramp.
The OKs (Object Kernel Support) is a library to support a simple, active persistent in-memory object manager. It is suitable for applications which need to create persistent structured information with fast access but do not require full database functionality. It can be used as the frame of configuration databases and real-time object managers for Data Acquisition and Detector Control Systems in such fields as setup, diagnostics and general configuration description.OKS is based on an object model that supports objects, classes, associations, methods, inheritance, polymorphism, object identifiers, composite objects, integrity constraints, schema evolution, data migration and active notification. OKS stores the class definitions and their instances in portable ASCII files. It provides query facilities, including indices support. The OKS has a C++ API (Application Program Interface) and includes Motif based GUI applications to design class schema and to manipulate objects.OKS has been developed on top of the Rogue Wave Tools.h++ C++ class library [l].
Attempts to introduce a reliable tune feedback loop at RHIC 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 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 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. AbstractAttempts to introduce a reliable tune feedback loop at RHIC [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.
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