Simulation studies of main linac steering in the next linear collider

In order to achieve the design luminosity of the Next Linear Collider, the main linac must accelerate trains of bunches from 10 GeV to 500 GeV while preserving vertical normalized emittances on the order of 0.05 mm.mrad. We describe a set of simulation studies, performed using the program LIAR, comparing several algorithms for steering the main linac; the algorithms are compared on the basis of emittance preservation, convergence speed, and sensitivity to BNS phase profile. The effects of an ATL mechanism during the steering procedure are also studied

Beam-based Feedback Simulations for the NLC Linac

Extensive beam-based feedback systems are planned as an integral part of the Next Linear Collider (NLC) control system. Wakefield effects are a significant influence on the feedback design, imposing both architectural and algorithmic constraints. Studies are in progress to assure the optimal selection of devices and to refine and confirm the algorithms for the system design. We show the results of initial simulations, along with evaluations of system response for various conditions of ground motion and other operational disturbances.Comment: 3 pages. Linac2000 conferenc

Interrater Reliability in Toxicity Identification: Limitations of Current Standards.

PurposeThe National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) v5.0 is the standard for oncology toxicity encoding and grading, despite limited validation. We assessed interrater reliability (IRR) in multireviewer toxicity identification.Methods and materialsTwo reviewers independently reviewed 100 randomly selected notes for weekly on-treatment visits during radiation therapy from the electronic health record. Discrepancies were adjudicated by a third reviewer for consensus. Term harmonization was performed to account for overlapping symptoms in CTCAE. IRR was assessed based on unweighted and weighted Cohen's kappa coefficients.ResultsBetween reviewers, the unweighted kappa was 0.68 (95% confidence interval, 0.65-0.71) and the weighted kappa was 0.59 (0.22-1.00). IRR was consistent between symptoms noted as present or absent with a kappa of 0.6 (0.66-0.71) and 0.6 (0.65-0.69), respectively.ConclusionsSignificant discordance suggests toxicity identification, particularly retrospectively, is a complex and error-prone task. Strategies to minimize IRR, including training and simplification of the CTCAE criteria, should be considered in trial design and future terminologies

Nulling Emittance Measurement Technique for CLIC Test Facility

In order to test the principle of Two-Beam-Acceleration (TBA), the CLIC Test Facility utilizes a high-intensity drive beam of 640 to 1000 nC to generate 30 GHz accelerating fields. To ensure that the beam is transported efficiently, a robust measurement of beam emittance and Twiss parameters is required. This is accomplished by measuring the beam size on a profile monitor, while scanning five or more upstream quadrupoles in such a fashion that the Twiss parameters at the profile monitor remain constant while the phase advance through the beam line changes. In this way the beam size can be sampled at different phases while a near-constant size is of such measurement devices, especially those associated with limited dynamic range. In addition, the beam size is explicitly constant for a matched beam, which provides a ``nulling'' measurement of the match. Details of the technique, simulations, and results of the measurements are discussed

Application of Kick Minimization to the RTML 'Front End'

The ''front end'' of the ILC RTML constitutes the sections of the RTML which are upstream of the first RF cavity of the first stage bunch compressor: specifically, the SKEW, COLL, TURN, SPIN, and EMIT sections. Although in principle it should be easy to transport the beam through these sections with low emittance growth, since the energy spread of the beam is relatively low, in practice it is difficult because of the large number of betatron wavelengths and strong focusing, especially in the TURN section. We report here on the use of the Kick Minimization Method for limiting the emittance growth in the ''front end'' of the RTML. Kick Minimization (KM) is a steering method which balances two optima: minimization of the RMS measured orbit on the BPMs (often called 1:1 steering), and minimization of the RMS corrector strength [1]. The simulation program used for these studies is Lucretia [2]

Emittance Correction in the 2006 ILC Bunch Compressor

A recent study [1] has indicated substantial potential emittance growth in the ILC bunch compressor due to quad misalignments, BPM misalignments, and pitches in the RF cavities. Table 1 summarizes several results from [1]. In this simulation, quad misalignments and cavity pitches are Gaussian distributed and are considered with respect to the nominal survey line; BPM misalignments are also Gaussian-distributed but are considered with respect to the quadrupole axis. It is assumed that the BPM offsets with respect to the quads are found in a previous quad-shunting BBA step which is not simulated. In this study we seek to repeat the studies documented above, and additionally to perform a study in which additional dispersion bumps are used to further reduce the projected emittance