18885837
Beam test of a superconducting cavity for the CESR luminosity upgrade
The prototype superconducting cavity system for CESR-Phase III was tested in CESR in August 1994. The performance of the system was very gratifying. The cavity operated gradients of 4.5-6 MV/m and accelerated beam currents up to 220 mA. This current is a factor of 3 above the world record 67 mA for SRF[1]. The high circulating beam current did not increase the heat load or present any danger to the cavity. No instability attributable to the SRF cavity was encountered. A maximum of 155 kW of rf power was transferred to a 120 mA beam. The window was subjected to 125 kW reflected power and processed easily. In the travelling wave mode, vacuum bursts and are trips prevented us from going above 165 kW. The maximum HOM power extracted was 2 kW. Beam stability studies were conducted for a variety of bunch configurations. In other tests a 120 mA beam was bumped horizontally and vertically by /spl plusmn/10 mm. While supporting a 100 mA beam, the cavity was axially deformed with the tuner by 0.4 mm to sweep the HOM frequencies across dangerous revolution harmonics. In all such tests, no resonant excitation of HOMs or beam instabilities were observed, which confirms that the potentially dangerous modes were damped strongly enough to be rendered harmless.
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.
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.
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.
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.
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.
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.
120582474
Study of inclusive neutral current interactions of neutrinos and antineutrinos
Abstract We report on results from a study of hadron-energy distributions for ν and ν inclusive neutral current interactions. There is no significant variation of the neutral to charged current total cross-section ratios R ν and R ν with neutrino energy. The space-time structure of neutral currents is dominated by V − A , with a significant admixture of V + A . The Weinberg-Salam model is in agreement with all data if sin 2 θ w =0.24±0.02.
122027905
Production of charmed mesons inZ decays
AbstractThe production of charmed mesons
$$\mathop {D^0 }\limits^{( - )} $$
,D±, andD*± is studied in a sample of 478,000 hadronicZ decays. The production rates are measured to be
$$\begin{gathered} \frac{{\Gamma ({\rm Z} \to D^{* \pm } X)}}{{\Gamma _{had} }} = 0.187 \pm 0.015(\exp .) \pm 0.013(BR), \hfill \\ \frac{{\Gamma ({\rm Z} \to D^ \pm X)}}{{\Gamma _{had} }} = 0.251 \pm 0.026(\exp .) \pm 0.025(BR), \hfill \\ \frac{{\Gamma ({\rm Z} \to \mathop {D^0 }\limits^{( - )} X)}}{{\Gamma _{had} }} = 0.518 \pm 0.052(\exp .) \pm 0.035(BR), \hfill \\ \end{gathered} $$
 where the errors from this analysis are separated from those coming from theD branching ratios (BR). TheD*± momentum distribution is extracted separately for
$$Z \to c\bar c$$
 and
$$Z \to b\bar b$$
 events with the help of event shape variables. It is consistent with the prediction of the JETSET Monte Carlo program after adjustment of the charm fragmentation function. Constraining the shape of the
$$Z \to b\bar b$$
 contribution, the average fraction of the beam energy taken by aD* meson produced in the fragmentation of a charm quark is extracted by a parametric fit to be c=0.495±0.011±0.007. Evidence forD**0 (D1(2420)0 and/orD2*(2460)0) production is found in the
$$D^{* \pm } \pi ^ \mp $$
 channel, accounting for a fraction (18±5±2)% of allD*± production. The relative production of vector and pseudoscalar mesons is dicussed, together with the possible effects ofD** production. Thec-quark forward-backwardZ-pole asymmetry is detrmined from that of high momentumD*± to beAFB0,c=(7.7±4.4)%.
119085485
Heavy quark tagging with leptons in the ALEPH detector
This paper deals with sustainable development policies in the French South-Eastern Alps region (Digne-les-Bains). It aims to delineate the influence of communication and mediation practices which are used to implement such principles in a largely reluctant area. This approach combines the point of views of two sciences, media and communication on the one hand, geography , on the other hand
123082927
Electroweak parameters from a high statistics neutrino nucleon scattering experiment
AbstractThe final results from the WA 1/2 neutrino experiment in the 1984 CERN 160 GeV narrow band beam are presented. The ratiosRν and
$$R_{\bar v} $$
 of neutral to charged current interaction rates of neutrinos and antineutrinos in iron are measured to beRν=0.3072±0.0033 and
$$R_{\bar v} $$
=0.382±0.016. A value of the electroweak parameter sin2 θw = 1 −mW2/mZ2 is extracted fromRν. The result is sin2 θw =0.228+0.013(mc−1.5)±0.0003 (theor.) wheremc is the mass of the charmed quark in GeV formt=60 GeV,MH=100 GeV, ρ=1. CombiningRν and
$$R_{\bar v} $$
 one obtains a value for ρ=0.991+0.023(mc−1.5)±0.020(exp.). Alternatively,Rν and
$$R_{\bar v} $$
 yield a precise value of the ratio of intermediate vector boson massesmW/mZ=0.880−0.007(mc−1.5)±0.002(exp.)±0.002(theor.). Comparison of these results with those from direct measurements of the vector boson masses are presented. In a model-independent analysis the left- and right-handed neutral current coupling constants,gL2 andgR2, are determined.