120575134
EUROFEL: Europe Tackles Key Issues of Free Electron Lasers
During the last few years Europe has made enormous progress towards free electron laser (FEL)-based research infrastructures. The FLASH facility [1] at DESY in Hamburg, Germany, has been in user operation since the summer of 2005; FERMI@Elettra [2] in Trieste, Italy, is under construction; the European XFEL [3] in Hamburg will start construction in summer 2008; and several other FEL projects are being prepared in France, Germany, Italy, Poland, Sweden, Switzerland and the UK. In addition, a number of dedicated test facilities have become available, including the photo-injector test facility (PITZ) [4] and the cryomodule test bench (CMTB) [5] at DESY, the HoBiCaT facility for testing superconducting cavities [6] at BESSY, Berlin, Germany, the SPARC facility [7] at INFN-LNF in Frascati, Italy, and the ERL Prototype (ERLP) [8] at Daresbury Laboratory, UK. They have been strongly supported by the national stakeholders in order to prepare the design of new FEL sources.
55994461
FIRST CHARACTERIZATION OF A FULLY SUPERCONDUCTING RF PHOTOINJECTOR CAVITY
As a first step towards a high brightness, high average current electron source for the BERLinPro ERL a fully superconducting photo-injector was developed by HZB in collaboration with JLab, DESY and the A. Soltan Institute. This cavity-injector ensemble is made up of a 1.6-cell superconducting cavity with a superconducting lead cathode deposited on the half-cell backwall. A superconducting solenoid is used for emittance compensation. This system, including a diagnostics beamline, has been installed in the HoBiCaT facility to serve as a testbed for beam dynamics studies and to test the combination SRF cavity and superconducting solenoid. This paper summarizes the characterization of the cavity in this configuration including Q measurements, dark current tests and field-stability analyses.
31537972
First Considerations Concerning an Optimized Cavity Design for the Main Linac of BERLinPro
The Berlin Energy Recovery Linac Project (BERLinPro) is designed to develop and demonstrate CW linac technology and expertise required to drive next-generation Energy Recovery Linacs. Strongly HOM-damped multicell 1.3 GHz cavities are required for the main linac. The optimization of the cavities presented here is primarily based on the CEBAF 1.5 GHz 5-cell high-current cavity design, including HOM waveguide couplers. The cavity was scaled to 1.3 GHz and extended to 7 cells. Modifications to the end group design have also been studied. An effort was also made to reduce the ratio Epk/Eacc while still permitting HOMs to propagate.
59036810
First Demonstration of Electron Beam Generation and Characterization with an All Superconducting Radio-frequency (SRF) Photoinjector
In preparation for a high brightness, high average current electron source for the energy recovery linac BERLinPro an all superconducting radio-frequency (SRF) photoinjector is now in operation at Helmholtz-Zentrum Berlin. The aim of this experiment is beam demonstration with a high brightness electron source able to generate short, few ps long pulse length electron bunches from a superconducting (SC) cathode film made of Pb coated on the backplane of a Nb SRF cavity. This paper describes the setup of the experiment, first results from beam measurements and capabilities of the source derived from beam dynamics considerations. In April 2011 the photoinjector generated and accelerated for the first time electron beam. This result marks the highlight of the project running for two years starting with project approval in May 2009.
37292985
FABRICATION , TREATMENT AND TESTING OF A 1 . 6 CELL PHOTO- INJECTOR CAVITY FOR HZB
As an amendment to a CRADA (Cooperative Research and Development Agreement) between Forschungszentrum Dresden (FZD) and JLab we have fabricated and tested after appropriate surface treatment a 1.6 cell, 1300 MHz RRR niobium photo-injector cavity to be used in a demonstration test at HZB. Following a baseline test at JLab, the cavity received a lead spot coating of ~8 mm diameter deposited with a cathode arc at the Soltan Institute on the endplate made from large grain niobium. It had been demonstrated in earlier tests with a DESY built 1.6 cell cavity – the original design – that a lead spot of this size can be a good electron source, when irradiated with a laser light of 213 nm. In the initial test with the lead spot we could measure a peak surface electric field of ~29 MV/m; after a second surface treatment, carried out to improve the cavity performance, but which was not done with sufficient precaution, the lead spot was destroyed and the cavity had to be coated a second time. This contribution reports about the experiences and results obtained with this cavity.
198946223
CHARACTERISATION OF MICROPHONICS IN HOBICAT
The HoBiCaT test-facility at BESSY, which is designed for cryogenic testing of superconducting TESLA units has been equipped with a 9-cell TESLA-type cavity. Mechanical vibrations in the cryostat result in microphonic detuning of the cavity resonance. These microphonics have been characterized, and their sources analyzed, including the impact of operating conditions such as LHe pressure, cavity field and heater power. Furthermore, the mechanical transfer functions needed for the eventual compensation of the microphonics have been recorded. INTRODUCTION For CW operation of a superconducting, TESLA-type cavity microphonics represent the largest disturbance of the resonant frequency. In particular at a small bandwidth Δf = ω/QL, according to the equation P ∝ 1 + (δf) 2 (Δf)2 (1) the microphonics δf lead to a significant increase of the generator power P, which is required to maintain a constant cavity field. Therefore it is highly desirable to minimize the microphonics. Measurements characterizing the microphonics and their impact on the cavity operation are presented below. The perspectives on possible countermeasures are described elsewhere [1]. MICROPHONICS MEASUREMENTS Microphonics have been recorded in two different ways. In a first method, the RF-feedback signal, see Figure 1, is recorded over time. This is preferably done in open loop configuration, because obtaining a calibration factor is more straightforward here, than in closed loop configuration. A second method utilizes the sensor-actuator design of the piezo tuner to record the induced piezoelectric voltage over time. In this design, two high-voltage piezos are attached to the tuner, thus piezoelectric forces can be exercised on the cavity and measured simultaneously. The latter is only an indirect method, as the mechanical influence from cavity and tank on the frequency response does not necessarily lead to a linear relationship between cavityand piezo position. The results presented here were solely obtained from the RF-feedback signal. ∗Work funded by the European Commission in the Sixth Framework Program, contract No. 011935 EUROFEL. Input coupler piezo
122736691
Inclusive production of neutral pions in hadronic Z decays
A measurement of the inclusive production of pi0 mesons in hadronic Z decays is presented and compared to Monte Carlo model predictions. The analysis is based on approximately 2 million hadronic events recorded with the ALEPH detector at LEP at a centre-of-mass energy of sqrt(s) = 91.2 GeV. Neutral pions are reconstructed using photons from conversion pairs and photons measured in the electromagnetic calorimeter. The inclusive pi0 momentum spectrum is measured in the range from 0.025 < x(p) = p/p(beam) < 1 to be 4.80 +/- 0.07(stat) +/- 0.31(sys). The differential inclusive pi0 cross section has also been measured as a function of transverse momentum with respect to the event plane (p_T^in and p_T^out_T).
209835401
Search for events with large missing transverse momentum, jets, and at least two tau leptons in 7 TeV proton–proton collision data with the ATLAS detector
A search for events with large missing transverse momentum, jets, and at least two tau leptons has been performed using 2 fb(-1) of proton-proton collision data at root s = 7 TeV recorded with the ...
116813021
Results of a beam dump experiment at the CERN SPS neutrino facility
We report results from a beam dump experiment that has been performed at the CERN SPS neutrino facility using the CDHS neutrino counter detector. Limits on dimuon and trimuon production by new penetrating neutral particles are given. A new source of prompt electron and muon neutrinos has been observed giving (1.2±0.4)× 10−7 νe or νμ per incident proton with neutrino angle smaller than 1.85 mrad and Eν > 20 GeV. If these prompt neutrinos are attributed to charmed meson pair production, the inclusive DD production cross section could be of the order of 30 ωb. If axions are existing their production rate relative to π0 mesons is found to be less than 0.5 × 10−8.
23468075
Status Report of the DPHEP Study Group: Towards a Global Effort for Sustainable Data Preservation in High Energy Physics
Data from high-energy physics (HEP) experiments are collected with significant financial and human effort and are mostly unique. An inter-experimental study group on HEP data preservation and long-term analysis was convened as a panel of the International Committee for Future Accelerators (ICFA). The group was formed by large collider-based experiments and investigated the technical and organisational aspects of HEP data preservation. An intermediate report was released in November 2009 addressing the general issues of data preservation in HEP. This paper includes and extends the intermediate report. It provides an analysis of the research case for data preservation and a detailed description of the various projects at experiment, laboratory and international levels. In addition, the paper provides a concrete proposal for an international organisation in charge of the data management and policies in high-energy physics.
126420285
Table 55 ; Measurement of the pseudorapidity and transverse momentum dependence of the elliptic flow of charged particles in lead-lead collisions at $\sqrt{s_{NN}}=2.76$ TeV with the ATLAS detector