242 research outputs found
Effects of rf breakdown on the beam in the Compact Linear Collider prototype accelerator structure
Understanding the effects of RF breakdown in high-gradient accelerator
structures on the accelerated beam is an extremely relevant aspect in the
development of the Compact Linear Collider (CLIC) and is one of the main issues
addressed at the Two-beam Test Stand at the CLIC Test Facility 3 at CERN.
During a RF breakdown large electro-magnetic fields are generated and produce
parasitic magnetic fields which interact with the accelerated beam affecting
its orbit and energy. We discuss here measurements of such effects observed on
an electron beam accelerated in a CLIC prototype structure. Measurements of the
trajectory of bunch-trains on a nanosecond time-scale showed fast changes in
correspondence of breakdown which we compare with measurements of the relative
beam spots on a scintillating screen. We identify different breakdown scenarios
for which we offer an explanation based also on measurements of the power at
the input and output ports of the accelerator structure. Finally we present the
distribution of the magnitude of the observed changes in the beam orbit and we
discuss its correlation with RF power and breakdown location in the accelerator
structure.Comment: 10 pages, 8 figures. We replace the previous version of the article
with this one, in which we extend our discussion on the experimental set-up
and on the interpretation of our measurements, on the basis of the inputs
received during the review process for publication on Phys. Rev. Special
Topics - Accelerators and Beams. The essence of our conclusions remain
unchange
RF-BREAKDOWN KICKS AT THE CTF3 TWO-BEAM TEST STAND
Abstract The measurement of the effects of RF-breakdown on the beam in CLIC prototype accelerator structures is one of the key aspects of the CLIC two-beam acceleration scheme being addressed at the Two-beam Test Stand (TBTS) at CTF3. RF-breakdown can randomly cause energy loss and transverse kicks to the beam. Transverse kicks have been measured by means of a screen intercepting the beam after the accelerator structure. In correspondence of a RFbreakdown we detect a double beam spot which we interpret as a sudden change of the beam trajectory within a single beam pulse. To time-resolve such effect, the TBTS has been equipped with five inductive Beam Position Monitors (BPMs) and a spectrometer line to measure both relative changes of the beam trajectory and energy losses. Here we discuss the methodology used and we present the latest results of such measurements
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
A Very Intense Neutrino Super Beam Experiment for Leptonic CP Violation Discovery based on the European Spallation Source Linac: A Snowmass 2013 White Paper
Very intense neutrino beams and large neutrino detectors will be needed in
order to enable the discovery of CP violation in the leptonic sector. We
propose to use the proton linac of the European Spallation Source currently
under construction in Lund, Sweden to deliver, in parallel with the spallation
neutron production, a very intense, cost effective and high performance
neutrino beam. The baseline program for the European Spallation Source linac is
that it will be fully operational at 5 MW average power by 2022, producing 2
GeV 2.86 ms long proton pulses at a rate of 14 Hz. Our proposal is to upgrade
the linac to 10 MW average power and 28 Hz, producing 14 pulses/s for neutron
production and 14 pulses/s for neutrino production. Furthermore, because of the
high current required in the pulsed neutrino horn, the length of the pulses
used for neutrino production needs to be compressed to a few s with the
aid of an accumulator ring. A long baseline experiment using this Super Beam
and a megaton underground Water Cherenkov detector located in existing mines
300-600 km from Lund will make it possible to discover leptonic CP violation at
5 significance level in up to 50% of the leptonic Dirac CP-violating
phase range. This experiment could also determine the neutrino mass hierarchy
at a significance level of more than 3 if this issue will not already
have been settled by other experiments by then. The mass hierarchy performance
could be increased by combining the neutrino beam results with those obtained
from atmospheric neutrinos detected by the same large volume detector. This
detector will also be used to measure the proton lifetime, detect cosmological
neutrinos and neutrinos from supernova explosions. Results on the sensitivity
to leptonic CP violation and the neutrino mass hierarchy are presented.Comment: 28 page
Study of the p p -> p p pi+ pi- Reaction in the Low-Energy Tail of the Roper Resonance
Exclusive measurements of the p p -> p p pi+ pi- reaction have been carried
out at Tp = 775 MeV at CELSIUS using the PROMICE/WASA setup. Together with data
obtained at lower energy they point to a dominance of the Roper excitation in
this process. From the observed interference of its decay routes N* -> N sigma
and N* -> Delta pi -> N sigma their energy-dependent relative branching ratio
is determined
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