Paper  Title  Page 

MOPPC052  Calculation of Synchrotron Radiation from High Intensity Electron Beam at eRHIC  247 


The ElectronRelativistic Heavy Ion Collider (eRHIC) at Brookhaven National Lab adds an electron beam line to the existing RHIC and improves the luminosity by at least 2 orders of magnitude. It requires a high energy and high intensity electron beam. Thus the synchrotron radiation (SR) coming from the bending magnets and large quadrupoles could be penetrating the vacuum chamber and providing hazard to electronic devices and undesired background for detectors. In this paper, we calculate the SR spectral intensity and power density distributions on the chamber wall, suggest the wall thickness required to stop the SR, calculate heat load on the chamber, and estimate spectral characteristics of the residual and scattered background radiation outside the chamber.  
MOPPP088  Control of Nonlinear Dynamics by Active and Passive Methods for the NSLSII Insertion Devices  759 


Funding: US DOE, Contract No. DEAC0298CH10886. Nonlinear dynamics effects from insertion devices (IDs) are known to affect the electron beam quality of third generation synchrotron light sources. In particular, beam lifetime, dynamical aperture and injection efficiency. Methods to model the IDs' nonlinear effects are known, e.g. by secondorder (in the inverse electron energy) kick maps. Methods to compensate these effects are known as well, e.g. by firstorder thin or thick magnetic kicks introduced by "magic fingers," "Lshims," or "current strips." However, due to physical or technological constraints, these corrections are typically only partial. Therefore, a precise model is required for a correct minimization of the residual nonlinear dynamics effects for the combined magnetic fields of the ID and compensating magnets. We outline a systematic approach for such predictions, based on 3D magnetic field and local trajectory calculation in the ID by the Radia code, and particle tracking by Tracy3. The optimal geometry for the compensating magnets is determined from these simulations using a combination of linear algebra and genetic optimization. 

MOPPP089  Development of a PrFeB Cryogenic Undulator at NSLSII  762 


Recent cryogenic undulators use PraseodymiumIronBoron (PrFeB) magnets cooled down to 80K. The main drawn drawback of the PrFeB magnet grades developed so far are their relative low coercive field at ambient temperature, below 2 T which prevents PrFeB based cryogenic undulator from baking. Some precautions are required during the undulator assembling and shimming to ensure ultra high vacuum compatibility. However Hitachi Metal Industry (HMI) recently developed two different grades of PrFeB magnet with large coercive field but at the expense of the remanent field. The magnetization curves have been measured from 40 K up to 400 K to determine the field increase and to investigate the magnet withstanding to baking. An IVU prototype has also been baked. Magnetic measurements before and after baking are also presented.  
MOPPP090  Spectral Performance of Segmented AdaptiveGap InVacuum Undulators for Storage Rings  765 


Funding: US DOE, Contract No. DEAC0298CH10886. We propose an approach to the optimization of segmented invacuum undulators, in which different segments along an undulator may have different gaps and periods. This enables close matching between the gaps and the vertical "envelope" of electron beam motion in a storage ring straight section (carefully satisfying the associated vertical "stay clear" constraint) and, at the same time, precise tuning of all the segments to the same fundamental photon energy. Thanks to this, the vertical gaps in segments located closer to straight section center can be smaller than at extremities, and so the entire undulator structure can offer better magnetic performance, compared to the case of a standard undulator with constant gap (and period) over its length. We will present magnetic field, radiation flux, brightness and intensity calculation results for such segmented adaptivegap invacuum undulators and demonstrate their gain in spectral performance over standard invacuum undulators, both for roomtemperature and cryocooled realizations. 

WEPPR098  Two Dimensional Impedance Analysis of Segmented IVU  3168 


Funding: Work supported by DOE contract No: DEAC0298CH10886 Segmented AdaptiveGap InVacuum Undulator (IVU) with variable magnetic gap along zaxis is considered as an alternative to the Constant Gap IVU (7mm gap) for the NSLSII storage ring. The length of the Constant Gap IVU for a given minimum gap is limited by the beam stay clear aperture. With the new conceptual design of IVU the magnetic gap can be varied along zaxis and its minimum gap can be reduced down to 5.25mm in the center of the structure for the same stay clear aperture. Beam impedance becomes an important issue since the new design consists of several magnet gaps. Wakepotentials and impedances have been analyzed for a new type of IVU and the results compared with data for the reference geometry which is the Constant Gap IVU. 
