The effect becomes very important for an intense short bunch when a tight collimation of the background beam halo is required. The halo is most likely formed from gun dark current or dark current in some of the accelerating sections. The wake field effect from the collimators not only brings an additional energy jitter and change in the trajectory of the beam, but it also rotates the beam on the phase plane, which consequently leads to a degradation of the performance of the Free Electron Laser at the Linac Coherent Light Source. In this paper, we describe a model of the wake field radiation in the SLAC linac collimators. We use the results of a numerical simulation to illustrate the model. Based on the model, we derive simple formulas for the bunch energy loss and the average kick.
A collimator optimization method for quantitative imaging: Application to Y-90 bremsstrahlung SPECT
A collimator optimization method for quantitative imaging: Application to Y bremsstrahlung SPECT
Abstract In single photon emission computed tomography, the choice of the collimator has a major impact on the sensitivity and resolution of the system. Traditional parallel-hole and fan-beam collimators used in clinical practice, for example, have a relatively poor sensitivity and subcentimeter spatial resolution, while in small-animal imaging, pinhole collimators are used to obtain submillimeter resolution and multiple pinholes are often combined to increase sensitivity. This paper reviews methods for production, sensitivity maximization, and task-based optimization of collimation for both clinical and preclinical imaging applications. New opportunities for improved collimation are now arising primarily because of i new collimator-production techniques and ii detectors with improved intrinsic spatial resolution that have recently become available. These new technologies are expected to impact the design of collimators in the future. The authors also discuss concepts like septal penetration, high-resolution applications, multiplexing, sampling completeness, and adaptive systems, and the authors conclude with an example of an optimization study for a parallel-hole, fan-beam, cone-beam, and multiple-pinhole collimator for different applications.
Collimator List Designs Nuclear Fields has manufactured virtually every type of collimator, from unique research prototypes to standard production models. We were at the forefront in the development of Fanbeam, Conebeam and Kev collimators. Fanbeam Collimator Design Rules There are some design rules that one should take into consideration.
Post-therapy quantitative 90Y bremsstrahlung single photon emission computed tomography SPECT has shown great potential to provide reliable activity estimates, which are essential for dose verification. Typically 90Y imaging is performed with high- or medium-energy collimators. However, the energy spectrum of 90Y bremsstrahlung photons is substantially different than typical for these collimators. In addition, dosimetry requires quantitative images, and collimators are not typically optimized for such tasks. Optimizing a collimator for 90Y imaging is both novel and potentially important.