• N. Simos, M. Fallier
  BNL, Upton, Long Island, New York

Vibration stability in third generation light sources such as the 3 GeV NSLS II under construction at BNL and which are aiming at high brightness and extremely small photon beam sizes is paramount. Movement of the magnetic elements of the accelerator lattice, and in particular when uncorrelated, will induce jitter in the beam and degrade the machine performance. The accelerator lattice response is coupled with the ring structure which in turn interacts with the site and the ground vibration field that characterizes it. Therefore, understanding this dynamic coupling between the accelerator ring structure and the site and the “filtering” effect of the interaction on both the amplitude and the spectral characteristics of the ground vibration is central towards establishing the response of the lattice. In this study, the site-ring dynamic interaction is evaluated based on the NSLS II design and site conditions using a state-of-the-art 3-D wave propagation and scattering analysis model. The study is augmented with an extensive array of measurements at the selected site as well as field studies at similar operating light source facilities.

• N. Simos, M. Fallier, T.F. Joos
  BNL, Upton, Long Island, New York

Cultural noise generated within or in the proximity of a light source facility aiming to achieve stability levels of just tens of nanometers in the electron beam and extremely small photon beams in special experimental lines could be a limiting factor towards achieving the performance goals. While operating systems within the facility are more readily identifiable as sources of vibration and cause of instabilities and they tend to be of deterministic nature so appropriate action can be taken to minimize their impact, moving-type loads such as traffic in the general vicinity or within the bounds of the accelerator facility are more of a stochastic nature and require a different approach in assessing its impact on the synchrotron facility. In this study the effect of such loads which poses both stochastic elements and a complex spectrum on the stability performance goals of the NSLS II synchrotron and its vibration-sensitive experimental lines is addressed prior to the construction of the facility. This is achieved through the synergy of a comprehensive numerical model and an array of recorded field data.

• N. Simos
  BNL, Upton, Long Island, New York

The extremely small photon beam dimensions of NSLS II impose challenging requirements on the e-beam orbital stability in the 6-D phase space. The electron beam orbit at the photon source locations must remain within a few hundred nanometer window for a wide frequency band. The beam orbit movement is coupled to the movement of the magnetic elements in the lattice which are itself coupled to the ring-building structure. While the vibration exciting the ring structure consists of deterministic and stochastic noise, it is the high frequency random, uncorrelated part that has the largest impact on the residual beam orbit movement as it is most difficult to control by fast orbit feedback. In this study, an analytical model is employed to quantify lattice displacement and beam orbit jitter for the expected conditions of NSLS II. The dynamic interaction of the ring supporting the lattice with the stationary ground vibration is addressed using a 3-D model of wave-structure interaction. Cross transfer functions linking ground vibration with the ring and magnetic lattice for various stochastic parameters are deduced leading to a multi-degree of freedom cross-spectral density of the lattice.

• N. Simos, G. Atoian, H. Ludewig, J.G. O'Conor, S.N. White
  BNL, Upton, Long Island, New York
• N.V. Mokhov
  Fermilab, Batavia

Funding: Work performed under the auspices of the US Department of Energy

SiO2 quartz fibers of the LHC ATLAS 0-degree calorimeter (ZDC) anticipated to experience integrated doses of a few Grad at their closest position were exposed to 200 MeV protons and neutrons at the BNL Linac. Specifically, 1mm- and 2mm- diameter quartz (GE 124) rods were exposed to direct 200 MeV protons during the first phase of exposure leading to peak integrated dose of ~28 Grad. Exposure to a primarily neutron flux of 1mm-diameter SiO2 fibers was also achieved with a special neutron source arrangement. In a post-irradiation analysis the quartz fiber transmittance was evaluated as a function of the absorbed dose. Dramatic degradation of the transmittance property was observed with increased radiation damage. In addition, detailed evaluation of the fibers under the microscope revealed interesting micro-structural damage features and irradiation-induced defects. This paper presents the results of the irradiation damage study.

• N. Simos, A. Aronson, A.E. Bolotnikov, G.S. Camarda, C. Copeland, R. James, H. Ludewig
  BNL, Upton, Long Island, New York

The effects of high fluences of energetic charged particles on CdZnTe detectors have been studied and are reported in this paper. Specifically, 200 MeV protons of the Brookhaven National Laboratory LINAC were used to bombard a set of CdZnTe detector crystals to fluences as high as 2.6x10¹⁶ protons/cm². Following exposure a set of past-irradiation analyses were conducted to quantify the effects. These include (a) gamma-ray spectra analysis using a high-purity germanium detector in an effort to assess both the peak position shifting as a function of fluence and the spectral content, (a) resistivity and leakage current measurements, and (c) manifestation of radiation damage in the crystal microstructure. In addition, and based on the irradiation parameters used, a numerical prediction model was formulated aiming to benchmark the observed isotopes.