12 research outputs found
Three-cell traveling wave superconducting test structure
Use of a superconducting traveling wave accelerating (STWA) structure with a
small phase advance per cell rather than a standing wave structure may provide
a significant increase of the accelerating gradient in the ILC linac. For the
same surface electric and magnetic fields the STWA achieves an accelerating
gradient 1.2 larger than TESLA-like standing wave cavities. The STWA allows
also longer acceleration cavities, reducing the number of gaps between them.
However, the STWA structure requires a SC feedback waveguide to return the few
hundreds of MW of circulating RF power from the structure output to the
structure input. A test single-cell cavity with feedback was designed,
manufactured and successfully tested demonstrating the possibility of a proper
processing to achieve a high accelerating gradient. These results open way to
take the next step of the TW SC cavity development: to build and test a
traveling-wave three-cell cavity with a feedback waveguide. The latest results
of the single-cell cavity tests are discussed as well as the design of the test
3-cell TW cavity.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 28 Mar - 1 Apr
2011: New York, US
Millikelvin measurements of permittivity and loss tangent of lithium niobate
Lithium Niobate is an electro-optic material with many applications in
microwave signal processing, communication, quantum sensing, and quantum
computing. In this letter, we present findings on evaluating the complex
electromagnetic permittivity of lithium niobate at millikelvin temperatures.
Measurements are carried out using a resonant-type method with a
superconducting radio-frequency (SRF) cavity operating at 7 GHz and designed to
characterize anisotropic dielectrics. The relative permittivity tensor and loss
tangent are measured at 50 mK with unprecedented accuracy.Comment: 5 pages, 4 figure
Crustal Emission and the Quiescent Spectrum of the Neutron Star in KS 1731-260
(Abridged). The type-I X-ray bursting low mass X-ray binary KS 1731-260 was
recently detected for the first time in quiescence by Wijnands et al.,
following an approximately 13 yr outburst which ended in Feb 2001. Unlike all
other known transient neutron stars, the duration of this recent outburst is as
long as the thermal diffusion time of the crust. The large amount of heat
deposited by reactions in the crust will have heated the crust to temperatures
much higher than the equilibrium core temperature. As a result, the thermal
luminosity currently observed from the neutron star is dominated not by the
core, but by the crust. Moreover, the level and the time evolution of quiescent
luminosity is determined mostly by the amount of heat deposited in the crust
during the most recent outburst. Using estimates of the outburst mass accretion
rate, our calculations of the quiescent flux immediately following the end of
the outburst agree with the observed quiescent flux to within a factor of a
few. We present simulations of the evolution of the quiescent lightcurve for
different scenarios of the crust microphysics, and demonstrate that monitoring
observations (with currently flying instruments) spanning from 1--30 yr can
measure the crust cooling timescale and the total amount of heat stored in the
crust. These quantities have not been directly measured for any neutron star.Comment: Submitted to ApJ; 7 text pages, 3 figures, uses emulateapj.sty and
apjfonts.st
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Analysis and Design of MEBT Beam Absorber for Project-X
A beam absorber is needed for a new high power accelerator to be built in Fermilab. It is called Project-X and should replace the existing linac and the 8 GeV Booster synchrotron. The beam absorber is part of the bunch-by-bunch chopper assigned to create an arbitrary bunch sequence required by experimental program. It will be located in the middle of the medium energy beam transport (MEBT) and has to remove the unnecessary bunches from the initially uniform bunch structure supplied by 2.1 MeV CW RFQ. At nominal RFQ beam current of 5 mA, the maximum power delivered to the beam absorber is about 10 kW. Beam optics requirements result in that the length allocated to the beam absorber is short ({approx}400 mm) and the beam size is small ({sigma}{approx}2mm). That yields high power density of the beam arriving to the absorber. The paper presents the thermal and mechanical analysis of one of proposed designs
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CW Room Temperature Re-Buncher for the Project X Front End
At Fermilab there is a plan to construct the Project X Injector Experiment (PXIE) facility - a prototype of the front end of the Project X, a multi-MW proton source based on superconducting linac. The construction and successful operations of this facility will validate the concept for the Project X front end, thereby minimizing the primary technical risk element within the Project. The room temperature front end of the linac contains an ion source, an RFQ accelerator and a Medium Energy Beam Transport (MEBT) section comprising a high bandwidth bunch selective chopper. The MEBT length is about 10 m, so three re-bunching CW cavities are used to support the beam longitudinal dynamics. The paper reports a RF design of the re-bunchers along with preliminary beam dynamic and thermal analysis of the cavities
The International Linear Collider: Report to Snowmass 2021
The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community