Development of the X-band RF power source for JLC
In this paper, we summarize our activities on X-band RF power source development for the Japan Linear Collider (JLC) project. First, we have designed and tested a solenoid-focused klystron at 11.424 GHz with a pulse length of 1.5 /spl mu/s and with an efficiency of 47%. A periodic permanent magnet (PPM) klystron, the first in that kind at KEK, is also under development. In parallel to this activity, another PPM klystron has been developed and remodeled in collaboration with BINP. Second, a new RF window with 100-MW power-handling capability has been designed and tested. It utilizes the TW mixed mode (TE11 and TM11 modes) to reduce the surface field at the brazing edge of the ceramic. The cold model test shows a low electric field at the brazing point as predicted by HFSS calculations. The high power model is now in manufacturing and the testing will start soon. Third, the Blumlein modulator was upgraded to produce a pulse with 2 /spl mu/s flat top and 200 ns rise time at 550 kV output voltage. Fourth, the multi-mode 2/spl times/2 DLDS (Delay Line Distribution System) pulse compression system has been designed, and its basic unit was manufactured and tested for proof of the principle. The measurement results show that the system works well with a high power distribution efficiency. The so-called mode stability experiment is also under preparation in the ATF linac tunnel in collaboration with SLAC. This experiment is aimed for examination of the stability of linearly polarized TE12 mode in a 55 m long waveguide, a key issue in the present configuration of multi-mode DLDS. Details of these developments and measurement results are presented.

title: A multi-moded rf delay line distribution system for the next linear collider
abstract: The Delay Line Distribution System (DLDS) is an alternative to conventional pulse compression, which enhances the peak power of rf sources while matching the long pulse of those sources to the shorter filling time of accelerator structures. We present an implementation of this scheme that combines pairs of parallel delay lines of the system into single lines. The power of several sources is combined into a single waveguide delay line using a multi-mode launcher. The output mode of the launcher is determined by the phase coding of the input signals. The combined power is extracted from the delay line using mode-selective extractors, each of which extracts a single mode. Hence, the phase coding of the sources controls the output port of the combined power. The power is then fed to the local accelerator structures. We present a detailed design of such a system, including several implementation methods for the launchers, extractors, and ancillary high power rf components. The system is designed so that it can handle the 600 MW peak power required by the NLC design while maintaining high efficiency.

title: Beam Position Monitoring Using the Hom-Signals from a Damped and Detuned Accelerating Structure
abstract: The Next and Global Linear Collider (NLC/GLC) designs require precision alignment of the beam in the accelerator structures to reduce short range wakefields. The moderately damped and detuned structures themselves provide suitable higher order mode (HOM) signals to measure this alignment. The modes in the lowest dipole band, whose frequencies range from 14-16 GHz, provide the strongest signals. To determine the position resolution they provide, an NLC/GLC prototype structure that was installed in the ASSET facility of the SLAC Linac was instrumented to downmix and digitize these signals. The beam position within the structure was determined by simultaneously measuring the signals at three frequencies (14.3, 15, 15.7 GHz) corresponding to modes localized at the beginning, the middle and the end of the 60 cm long structure. A resolution of 1 micron was achieved even with 28 dB signal attenuation, which is better than the 5 micron resolution required for the NLC/GLC.

title: Alignment of the CMS Silicon Tracker during Commissioning with Cosmic Rays
abstract: This is the Pre-print version of the Article. The official published version of the Paper can be accessed from the link below - Copyright @ 2010 IOP

title: T2K neutrino flux prediction
abstract: The Tokai-to-Kamioka (T2K) experiment studies neutrino oscillations using an off-axis muon neutrino beam with a peak energy of about 0.6 GeV that originates at the Japan Proton Accelerator Research Complex accelerator facility. Interactions of the neutrinos are observed at near detectors placed at 280 m from the production target and at the far detector—Super-Kamiokande—located 295 km away. The flux prediction is an essential part of the successful prediction of neutrino interaction rates at the T2K detectors and is an important input to T2K neutrino oscillation and cross section measurements. A FLUKA and GEANT3-based simulation models the physical processes involved in the neutrino production, from the interaction of primary beam protons in the T2K target, to the decay of hadrons and muons that produce neutrinos. The simulation uses proton beam monitor measurements as inputs. The modeling of hadronic interactions is reweighted using thin target hadron production data, including recent charged pion and kaon measurements from the NA61/SHINE experiment. For the first T2K analyses the uncertainties on the flux prediction are evaluated to be below 15% near the flux peak. The uncertainty on the ratio of the flux predictions at the far and near detectors is less than 2% near the flux peak.

title: CMS Data Processing Workflows during an Extended Cosmic Ray Run
abstract: The CMS Collaboration conducted a month-long data taking exercise, the Cosmic Run At Four Tesla, during October-November 2008, with the goal of commissioning the experiment for extended operation. With all installed detector systems participating, CMS recorded 270 million cosmic ray events with the solenoid at a magnetic field strength of 3.8 T. This paper describes the data flow from the detector through the various online and offline computing systems, as well as the workflows used for recording the data, for aligning and calibrating the detector, and for analysis of the data.

title: Design of 2x2 DLDS RF Components for JLC
abstract: We have studied a multi-mode Delay Line Distribution System (DLDS)[1][2] as the RF power distribution system from klystrons to RF structures for linear colliders. In particular, a 2×2 DLDS has been proposed and studied at KEK for Japan Linear Collider(JLC). It has been proved that the 2×2 DLDS is simple, bus has good transmission efficiency. We have designed RF components of a basic unit of a DLDS using the High Frequency Structure Simulator (HFSS) code[3]. They include the TE01 extractor, the TE11 to TE01 converter, and the TE11 to TE12 converter for TE12 mode. HFSS calculation of the system, which consists of TE01 extractor and TE11 to TE01 converter, shows that the transmission efficiency of each mode is better than 95%. A low power test model for the mode stability experiment in 55m long wave guide in DLDS is also being developed. Further study is underway.

title: 50 MW X-BAND RF SYSTEM FOR A PHOTOINJECTOR TEST STATION AT LLNL
abstract: In support of X-band photoinjector development efforts at LLNL, a 50 MW test station is being constructed to investigate structure and photocathode optimization for future upgrades. A SLAC XL-4 klystron capable of generating 50 MW, 1.5 microsecond pulses will be the high power RF source for the system. Timing of the laser pulse on the photocathode with the applied RF field places very stringent requirements on phase jitter and drift. To achieve these requirements, the klystron will be powered by a state of the art, solid-state, high voltage modulator. The 50 MW will be divided between the photoinjector and a traveling wave accelerator section. A high power phase shifter is located between the photoinjector and accelerator section to adjust the phasing of the electron bunches with respect to the accelerating field. A variable attenuator is included on the input of the photoinjector. The distribution system including the various x-band components is being designed and constructed. In this paper, we will present the design, layout, and status of the RF system.

title: Search for Microscopic Black Hole Signatures at the Large Hadron Collider
abstract: A search for microscopic black hole production and decay in pp collisions at a center-of-mass energy of 7 TeV has been conducted by the CMS Collaboration at the LHC, using a data sample corresponding to an integrated luminosity of 35 inverse picobarns. Events with large total transverse energy are analyzed for the presence of multiple high-energy jets, leptons, and photons, typical of a signal expected from a microscopic black hole. Good agreement with the expected standard model backgrounds, dominated by QCD multijet production, is observed for various final-state multiplicities. Limits on the minimum black hole mass are set, in the range 3.5 -- 4.5 TeV, for a variety of parameters in a model with large extra dimensions, along with model-independent limits on new physics in these final states. These are the first direct limits on black hole production at a particle accelerator.

title: Strange particle production in pp collisions at $ \sqrt {s} = 0.9 $ and 7 TeV
abstract: The spectra of strange hadrons are measured in proton-proton collisions, recorded by the CMS experiment at the CERN LHC, at centre-of-mass energies of 0.9 and 7 TeV. The $ {\text{K}}_{\text{S}}^0 $, Λ, and Ξ− particles and their antiparticles are reconstructed from their decay topologies and the production rates are measured as functions of rapidity and transverse momentum, pT. The results are compared to other experiments and to predictions of the Pythia Monte Carlo program. The pT distributions are found to differ substantially from the Pythia results and the production rates exceed the predictions by up to a factor of three.

title: Monte Carlo simulation of the response of Si(Li) detectors to monoenergetic X-rays
abstract: We present a Monte Carlo simulation of X-ray interaction with a Si(Li) detector which includes for the first time both a detailed description of the atomic excitation and de-excitation and also a physically realistic model of the frontal region of incomplete charge collection. Simulated lineshapes are in good agreement with those measured by us using monoenergetic X-rays of energy 1–10 keV and by varying the two parameters of the model we can generate lineshapes very similar to those reported in the literature for other Si(Li) detectors.