Production of long-strip multi-gap resistive plate chamber module for the STAR-MTD system
A new Long-strip Multi-gap Resistive Plate Chamber (LMRPC) prototype with 5 gas gaps has been developed for the Muon Telescope Detector (MTD) of the STAR experiment at RHIC in order to reduce the working High Voltage (HV) of previous design. Technical specifications related to the final infrastructure present in the experiment have motivated this effort. Its performance has been measured with cosmic rays. The efficiency of this prototype can reach 98% and the time resolution is around 95 ps. It shows a good uniformity among strips. The noise level is less than 0.2 Hz/cm2. The signal transmission and crosstalk of the modules was measured with a vector network analyzer, showing a good match with simulations within the amplifier bandwidth. A new cosmic-ray test system with long scintillators has been developed to accelerate the Quality Control (QC) process during the mass production of STAR-MTD. A selection of perpendicular cosmic-ray events for more accurate evaluation of the time resolution is achieved. The time resolution with this method is better, albeit with larger error, than the result obtained without any selection. A new spacer is used, resulting in a much reduced streamer ratio at comparable fields. Thirty-two modules have been built with the new spacer by the middle of April of 2012. They have been tested and they all have passed the QC.

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: 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: A MRPC prototype for SOLID-TOF in JLab
abstract: A prototype of Multi-gap Resistive Plate Chamber (MRPC) for the future SoLID time of flight system at JLab has been developed. The counter, trapezoidal in shape, is assembled with the newly developed low-resistive Chinese glass. It has 10 × 0.25 mm gas gaps and 11 readout strips of different lengths. The strip width is 2.5 cm with a strip-to-strip interval of 3 mm. Preliminary tests performed with cosmic-rays showed an efficiency higher than 95% and a time resolution around 50 ps. Results under diffuse/uniform irradiation performed at JLab with scattered high energy electrons showed a time resolution of 70–80 ps and over-95% efficiency up to an incoming flux of 15 kHz/cm2. These performances meet the requirements of the new time of flight system SoLID-TOF.

title: STATUS OF THE X-BAND RF POWER SOURCE DEVELOPMENT FOR JLC
abstract: In this paper, we summarize the status of X-band RF power source development for the Japan Linear Collider (JLC) project. The periodic permanent magnet (PPM) klystrons are under development in the two-year/two-stage project with Toshiba. The goal is to produce 50MW output power at 1.5 µs pulse length at the first klystron and then to advance to 75MW at the second one. The high power testing of the first klystron is scheduled to start in July 2000. The multi-mode RF windows have been high power tested at KEK and SLAC. The window with smaller diameter (53mm) achieved a circulation power of 80MW with 1.5µs duration at 30Hz repetition. It was not destroyed during the testing. As for the modulator, the SIthyristor solid state switches were tested successfully. KEK is developing the multi-mode 2x2 DLDS (Delay Line Distribution System) power distribution system, in which the stability of linearly polarized TE12 mode in a long (up to 160m) waveguide is the key for low loss power transport. The experiment was carried out successfully in the ATF linac tunnel in collaboration with SLAC using a specially installed 55m long waveguide. 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: SOURCE OF MICROBUNCHING AT BNL NSLS SOURCE DEVELOPMENT LABORATORY
abstract: We report experimental studies of the origins of electron beam microbunching instability at BNL Source Development Laboratory (SDL). We eliminated laser-induced microbunching by utilizing an ultra-short photocathode laser. The measurements of the resulting electron beam led us to conclude that, at SDL, microbunching arising from shot noise is not amplified to any significant level. Our results demonstrated that the only source of microbunching instability at SDL is the longitudinal modulation of the photocathode laser pulse. Our work shows that assuring a longitudinally smoothed photocathode laser pulse allows mitigating microbunching instability at a typical FEL injector with a moderate microbunching gain. In this paper we investigated the source of microbunching instability at the SDL. To distinguish microbunching induced by shot noise from that arising from the longitudinal modulation of the photocathode laser, we studied the beam created by a very short laser pulse, thus eliminating the possibility of laser-induced microbunching. While the measured energy spectra of compressed beam did reveal severe longitudinal fragmentation, an analysis of the beam dynamics proved this to be due to self-fields acting on a beam with an initially smooth longitudinal profile, and not due to microbunching instability. Such fragmentation only was possible with the very short bunch chosen for these studies, and is absent in routine SDL operations. Our experiment shows that in the absence of the initial laser-induced beam modulation, microbunching instability at the SDL is not observed, and must be well below the levels that would limit the FEL performance. This result agrees with assumption of previous SDL studies that (when present under different machine conditions) microbunching instability at the SDL was laser-induced. Microbunching instability gain at the SDL is moderate. This is mainly because the SDL utilizes a single stage bunch compressor as well as due to the small compression ratio. Since the design of the SDL injector is typical of the majority of FEL injectors, our experiment proves that one possible way to control microbunching instability in such machines (that by design have a moderate microbunching gain) is to maintain a sufficiently smooth longitudinal profile of the photo-cathode laser. We note that the general principles for designing a machine with a moderate microbunching instability gain are presented in . In conclusion, our experiment demonstrates that microbunching instability can be eliminated from a typical FEL injector with single stage bunch compressor (and operating without a laser heater) as long as the photocathode laser is longitudinally smooth. For machines with multi-stage bunch compressors, our results offer an important benchmark to establish a minimal laser heater power for instability-free operation.

title: First look at the beam test results of the FPIX2 readout chip for the BTeV silicon pixel detector
abstract: High energy and nuclear physics experiments need tracking devices with increasing spatial precision and readout speed in the face of ever-higher track densities and increased radiation environments. The new generation of hybrid pixel detectors (arrays of silicon diodes bump bonded to arrays of front-end electronic cells) is the technology able to meet these challenges. We report the first results of the BTeV silicon pixel detector beam test carried out at Fermilab in summer 2004. Tests were performed using a 120 GeV/c proton beam incident on a 6 plane pixel detector telescope. The last prototype developed for the BTeV experiment (FPIX2) is tested in the middle of the telescope. There is no external trigger, and events were built using the time-stamp information provided by the readout chips

title: Electromagnetic calorimeter with thin gap wire chambers
abstract: In this paper we report about the experimental results obtained in a beam test of a gas sampling EM calorimeter. The module consists of 20 thin gap (30 mm) multiwire chambers as active elements, interleaved with brass absorber plates of 12 mm thickness or 0.84 radiation length. The KEK electron beam was tuned to energies of 0.5, 1.0, 2.0, 3.0, 4.0 GeV. The construction and performances of the chamber, the assembling of the module, the experimental setup and data acquisition system are briefly described. The energy resolution of the module is found to be 25%√E (E in GeV). In the range of measured energies, good linearity of the energy response is obtained. The longitudinal development of EM shower, the relation between energy resolution and thickness of the absorber as well as the high voltage of the chamber are studied. The effect of incident position of the beam on the performance of the module is also given.

title: MICROWAVE MEASUREMENTS OF ENERGY LOST TO LONGITUDINAL MODES BY SINGLE ELECTRON BUNCHES TRAVERSING PERIODIC STRUCTURES
abstract: In the design of future linear colliders, it will be important to minimize the loss of beam energy due to the excitation of higher-order modes in the accelerator structure by single bunches of electrons or positrons. This loss is not only detrimental in itself but also gives rise to energy spectrum widening and transverse emittance growth. This paper describes microwave measurements made on disk-loaded and alternating-spoke structures to determine the loss to the longitudinal modes. In these measurements the Gaussian bunch is simulated by a current pulse of the same shape transmitted through the structure on an axial center conductor. Results to date are presented for the total longitudinal loss parameter per period K in volts per picocoulomb.

title: Vertex and Track Reconstruction and Luminosity Monitoring at LHCb