Slotted Iris Structure Studies

Accelerating structures with strong transverse-mode damping are required in both the 30 GHz CLIC main linac and the 3 GHz CTF3 drive-beam accelerator. Damping via slotted irises has been investigated for both structures. The transverse wake, the effect of the slots on the fundamental-mode parameters such as Q, sensitivity to tolerances, and surface-field enhancements have been computed. Terminating loads have been designed and machining studies to obtain rounded slot edges have been made. A 32-cell prototype 3 GHz structure is being fabricated for the drive beam accelerator of CTF3

Burning Both Ends: Examining Overload, Trait Motivation, and Burnout Through the Person-Environment Interaction

Burnout has received substantial attention in academic literature and popular media due to its extensive breadth and detrimental impact on individual and organizational outcomes. To effectively address and combat the phenomenon, it is important to understand the boundary conditions in which burnout occurs and the individual and environmental interactions that predict burnout. In the current study, the relationships among burnout, overload, and trait motivation were investigated. Data were collected via Amazon Mechanical Turk from a sample of working professionals. Overload was negatively related to approach motivation and positively related to avoidance motivation and burnout. Approach motivation was negatively related to burnout, while avoidance motivation was positively related. A series of moderation models were tested to understand the interaction between trait motivation and overload in the relationship to burnout. The moderation results were not confirmed, but the main effects were significant. Understanding relevant boundary conditions and individual differences associated with motivation and burnout will equip organizational leaders and decision-makers to effectively combat the phenomenon and preserve employee well-being

Spectral filtering with diffractive reflection gratings for fast superconducting detectors in the THz frequency range

In this work we describe the design process of a grating spectrometer with fast superconducting THz detectors based on Niobiumnitride. The main application is the use as a diagnostic tool for accelerator-based sources of THz radiation like synchrotrons, where interactions of the electron bunches in storage ring lead to fluctuations in spectrum and intensity of the emitted radiation. Guidelines for the design of the two main parts, grating and detector design, are given. Here, a blazed reflection grating for a frequency range of 1 THz to 5 THz has been developed and successfully fabricated in a high-precision milling process out of brass. Also three different planar antenna designs (double-slot, annular slot and log-per spiral) in combination with quasioptical bandpass filters for the THz range have been simulated and evaluated for best spectral resolution and power coupling. Finally, we have verified grating performance for pulsed THz radiation of 1 THz in an experiment conducted at the synchrotron light source of the KIT. Excellent agreement of the grating performance to the simulations has been found

The Rydberg-Atom-Cavity Axion Search

We report on the present progress in development of the dark matter axion search experiment with Rydberg-atom-cavity detectors in Kyoto, CARRACK I and CARRACK II. The axion search has been performed with CARRACK I in the 8 % mass range around $10 \mu {\rm eV}$, and CARRACK II is now ready for the search in the wide range $2 \mu {\rm eV} - 50 \mu {\rm eV}$. We have also developed quantum theoretical calculations on the axion-photon-atom system in the resonant cavity in order to estimate precisely the detection sensitivity for the axion signal. Some essential features on the axion-photon-atom interaction are clarified, which provide the optimum experimental setup for the axion search.Comment: 8 pages, 2 figures, Invited talk presented at the Dark2000, Heidelberg, Germany,10-15 July, 200

SLAC/CERN high gradient tests on an X-band accelerating section

High frequency linear collider schemes envisage the use of rather high accelerating gradients: 50 to 100 MV/m for X-band and 80 MV/m for CLIC. Because these gradients are well above those commonly used in accelerators, high gradient studies of high frequency structures have been initiated and test facilities have been constructed at KEK [1], SLAC [2] and CERN [3]. The studies seek to demonstrate that the above mentioned gradients are both achievable and practical. There is no well-defined criterion for the maximum acceptable level of dark current but it must be low enough not to generate unacceptable transverse wakefields, disturb beam position monitor readings or cause RF power losses. Because there are of the order of 10,000 accelerating sections in a high frequency linear collider, the conditioning process should not be too long or difficult. The test facilities have been instrumented to allow investigation of field emission and RF breakdown mechanisms. With an understanding of these effects, the high gradient performance of accelerating sections may be improved through modifications in geometry, fabrication methods and surface finish. These high gradient test facilities also allow the ultimate performance of high frequency/short pulse length accelerating structures to be probed. This report describes the high gradient test at SLAC of an X-band accelerating section built at CERN using technology developed for CLIC

The Compact Linear e+^+e−^- Collider (CLIC): Accelerator and Detector

The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear e$^+$e$^-$ collider under development by international collaborations hosted by CERN. This document provides an overview of the design, technology, and implementation aspects of the CLIC accelerator and the detector. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, for a site length ranging between 11 km and 50 km. CLIC uses a two-beam acceleration scheme, in which normal-conducting high-gradient 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments, and system tests have resulted in significant progress in recent years. Moreover, this has led to an increased energy efficiency and reduced power consumption of around 170 MW for the 380 GeV stage, together with a reduced cost estimate of approximately 6 billion CHF. The detector concept, which matches the physics performance requirements and the CLIC experimental conditions, has been refined using improved software tools for simulation and reconstruction. Significant progress has been made on detector technology developments for the tracking and calorimetry systems. The construction of the first CLIC energy stage could start as early as 2026 and first beams would be available by 2035, marking the beginning of a physics programme spanning 25-30 years and providing excellent sensitivity to Beyond Standard Model physics, through direct searches and via a broad set of precision measurements of Standard Model processes, particularly in the Higgs and top-quark sectors.Comment: Input to the European Particle Physics Strategy Update on behalf of the CLIC and CLICdp Collaboration

High-Power Testing of X-Band CLIC Power Generating Structures

A fundamental element of the CLIC concept is two-beam acceleration, where rf power is extracted from a high-current and low-energy beam in order to accelerate the low-current main beam to high energy. The power extraction occurs in special Xband Power Extraction and Transfer Structures (PETS). The structures are large aperture, high-group velocity and overmoded periodic structures. Following the substantial changes of the CLIC baseline parameters in 2006, the PETS design has been thoroughly updated along with the fabrication methods and corresponding rf components. Two PETS prototypes have been fabricated and high power tested. Test results and future plans are presented