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Rotating gantries are commonly used in ion-therapy facilities to assist and support optimizing the dose distribution delivered to the patient. They are installed at the end of the beamlines and rotated mechanically in the treatment room. In synchrotron-based facilities, the gantries must be able to transport slowly extracted beams with essentially different emittance patterns in the two transverse planes. Such beams will be referred to as the asymmetric beams. A special device called rotator has been proposed as a possible solution. The worldwide first beamline with the rotator has been recently commissioned. The original rotator concept uses an “external” rotator that is a part (a module) of the beamline the gantry is connected to. In this paper, a novel gantry ion-optical concept integrating the rotator optics into the gantry optics is introduced. The first-order gantry transfer matrix satisfies the so-called sigma-matching ion-optical constraints, and—at the same time—it possesses the format of a rotator transfer matrix. The rotator-matching and the sigma-matching principles are combined in the gantry transfer matrix, which means that the sigma-matching gantry acts simultaneously as a rotator without the need for an extra rotator device. In addition, scattering in the gantry nozzle is used to balance the asymmetric beam emittances in the two transverse planes without an additional scattering foil. In this way, the presented ion-optical concept combines all three known matching techniques—the sigma matching, the rotator matching, and the scattering-foil matching—within the gantry beam transport system. Such a beam transport system provides the best matching result and full angular independence of the beam parameters at the gantry isocenter. It also makes it possible to optimize the beam parameters not only at the gantry isocenter but also at the beam monitors located in the gantry nozzle without increasing the number of gantry quadrupoles. There are two possible versions of such gantry optics: the point-to-point and the parallel-to-point optics. They both are presented in this paper. Theoretical calculations are supported by beam transport simulations performed with the winagile code. Feasibility of the newly proposed ion-optical concept is demonstrated on the MedAustron proton gantry. However, it can be applied to any rotating gantry at any ion-therapy facility. The presented design is the first rotatorlike gantry ion-optical concept worldwide.

This paper provides an overview of the worldwide first commissioning of a gantry beamline with a rotator at the MedAustron synchrotron-based proton/ion cancer therapy facility in Wiener Neustadt, Austria. The gantry beamline consists of the high energy beam transfer (HEBT) line and the gantry beam transport system. It transports the beam from the synchrotron to the gantry-room isocenter. The HEBT transports the beam from the synchrotron to the gantry entrance, which is the coupling point between the HEBT and the gantry. The rotator is one of the HEBT modules, thus it is an integral part of the gantry beamline. The MedAustron rotator is the worldwide first rotator system used to match slowly extracted asymmetric beams from the synchrotron to the rotating gantry. In this paper, main attention is paid to ion-optical and beam-alignment aspects of the beamline commissioning. A novel orbit-correction and beam-alignment technique has been developed specifically for the beamline with the rotator. While the theoretical concept of the rotator has existed for almost two decades, the MedAustron rotator is the first hardware implementation of this concept all over the world. The presented overview of the beamline commissioning includes a description of the principal technical solutions and main results of the first beam-transport measurements. Since the measured beam size and beam position agree well with theoretical predictions, one can conclude that the proof-of-concept of the rotator-matching has been successfully accomplished.

We report modeling results for electron cloud buildup and instability in the International Linear Collider positron damping ring. Updated optics, wiggler magnets, and vacuum chamber designs have recently been developed for the 5 GeV, 3.2-km racetrack layout. An analysis of the synchrotron radiation profile around the ring has been performed, including the effects of diffuse and specular photon scattering on the interior surfaces of the vacuum chamber. The results provide input to the cloud buildup simulations for the various magnetic field regions of the ring. The modeled cloud densities thus obtained are used in the instability threshold calculations. We conclude that the mitigation techniques employed in this model will suffice to allow operation of the damping ring at the design operational specifications.

We have applied our simulation code POSINST to evaluate the contribution to the growth rate of the electron cloud instability in proton storage rings. In particular, we present here recent simulation results for the main features of the electron cloud in the storage ring of the Spallation Neutron Source at Oak Ridge, and updated results for the Proton Storage Ring at Los Alamos. A key ingredient in our model is a detailed description of the secondary electron emission process, including a refined model for the emitted energy spectrum, and for the three main components of the secondary yield, namely, the true secondary, rediffused and backscattered components.

We provide a detailed description of a model and its computational algorithm for the secondary electron emission process. The model is based on a broad phenomenological fit to data for the secondary-emission yield and the emitted-energy spectrum. We provide two sets of values for the parameters by fitting our model to two particular data sets, one for copper and the other one for stainless steel.