EXPERIENCES ON IMPROVED CAVITY PREPARATION CYCLES WITH A VISION ON INDUSTRIALIZATION OF THE XFEL CAVITY PREPARATION

Abstract Within the last decade the production and preparation of superconducting resonators became more and more stable at DESY. Two cycles for the final surface preparation, the final surface removal by electro polishing (EP) and the final surface removal by a short buffered chemical polishing (BCP flash) are the baseline of cavity surface preparation at DESY. Basing on the positive development overtime and in view of industrialization of the processes for the XFEL project, a proposal for a reduced number of work steps was presented on the SRF 2007 workshop in Beijin

UPDATE ON THE JRA1 PROJECT RESULTS OF ELECTRO-POLISHING OF MULTI-CELL SUPER CONDUCTING RESONATORS

Abstract Under the contract RII3-CT-2003-506395 of the European Union improvement on the electro-polishing (EP) of multi cell resonators are made. Several methods to improve resonator performances are studied. Improvement of electrode shape, simulated by numerical computer codes and test set ups are presented. With respect to reproducible cavity performances and industrialization of the EP process, a study for quality control by acid management is started. An automated EP system is developed at INFN Legnaro / Italy and within the collaboration of Legnaro and DESY this automated steering will be integrated into the DESY EP facility. We will report on the status of the WP 5.2.2.and the progress of the transfer of the automated E

Inefficient Nef-Mediated Downmodulation of CD3 and MHC-I Correlates with Loss of CD4+ T Cells in Natural SIV Infection

Recent data suggest that Nef-mediated downmodulation of TCR-CD3 may protect SIVsmm-infected sooty mangabeys (SMs) against the loss of CD4+ T cells. However, the mechanisms underlying this protective effect remain unclear. To further assess the role of Nef in nonpathogenic SIV infection, we cloned nef alleles from 11 SIVsmm-infected SMs with high (>500) and 15 animals with low (<500) CD4+ T-cells/µl in bulk into proviral HIV-1 IRES/eGFP constructs and analyzed their effects on the phenotype, activation, and apoptosis of primary T cells. We found that not only efficient Nef-mediated downmodulation of TCR-CD3 but also of MHC-I correlated with preserved CD4+ T cell counts, as well as with high numbers of Ki67+CD4+ and CD8+CD28+ T cells and reduced CD95 expression by CD4+ T cells. Moreover, effective MHC-I downregulation correlated with low proportions of effector and high percentages of naïve and memory CD8+ T cells. We found that T cells infected with viruses expressing Nef alleles from the CD4low SM group expressed significantly higher levels of the CD69, interleukin (IL)-2 and programmed death (PD)-1 receptors than those expressing Nefs from the CD4high group. SIVsmm Nef alleles that were less active in downmodulating TCR-CD3 were also less potent in suppressing the activation of virally infected T cells and subsequent cell death. However, only nef alleles from a single animal with very low CD4+ T cell counts rendered T cells hyper-responsive to activation, similar to those of HIV-1. Our data suggest that Nef may protect the natural hosts of SIV against the loss of CD4+ T cells by at least two mechanisms: (i) downmodulation of TCR-CD3 to prevent activation-induced cell death and to suppress the induction of PD-1 that may impair T cell function and survival, and (ii) downmodulation of MHC-I to reduce CTL lysis of virally infected CD4+ T cells and/or bystander CD8+ T cell activation

Experience on In-Situ Module Repair and Set up of Non XFEL Cavity Strings at DESY

All components installed to the European XFEL cavity string modules underwent an intensive inspection and quality control before acceptance for installation to cavities or modules. Even though some RF feed throughs for HOM coupler- and Pick Up antennas showed leaks at the ceramic insulation after module test at 2 K. Due to time restriction and continuity of production the exchange of these parts needed to be done without reentering the cleanroom. Successful repair of these modules took place by setting up a local cleanroom onto the cavity string.In collaboration with Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a cavity string for the ELBE Project was assembled at DESY and transported to HZDR for installation to the vacuum vessel.A spare module with 3.9 GHz resonators for the Euro-pean XFEL was set up at DESY and will be tested and qualified for the European XFEL. Due to delay in delivery of the power couplers, four power couplers were installed after string assembly

Tibial plateau angles with and without cranial cruciate ligament rupture - Comparison between different dog populations and a wolf population

The tibial plateau angles (TPA) of dogs with andwithout cranial cruciate ligament (CrCL) injuries wereevaluated and further compared to the TPAs of dogsfrom a previous population and of wolves. Similar TPAmeasurements were found in all groups, suggestingthat any possible changes in breeding practises,breed preferences, nutrition or other factors have notsignificantly influenced the TPA over time. Moreover,a difference was not found in the TPA between anygroup and the group affected with CrCL injury,suggesting that the TPA is not a clinically relevantpredisposing factor in the development of canine CrCLrupture

Final Acceptance Test of SRF Photo injector Cold String for the BERLinPro Energy Recovery Linac

Helmholtz Zentrum Berlin HZB is currently designing and building an high average current all superconducting CW driven ERL as a prototype to demonstrate low normalized beam emittance of 1 mm mrad at 100 mA and short pulses of about 2 ps. In order to achieve these demanding goals HZB started a staged program for developing this class of required high current, high brightness SRF electron sources. In this contribution we will present the current status of the module assembly and testing of the prototype SRF photoinjector cavity cold string. The steps taken to install the cathode insert system with the cavity in the clean room and the following horizontal test of the cold string as final acceptance test prior installation into its cryostat are shown. First beam in a dedicated diagnostics test stand called Gunlab are planned for this winte

High gradients at SRF photoinjector cavities with low RRR copper cathode plug screwed to the cavity back wall

In recent years we increased the typical maximum peak field on axis gradients obtained in L-band superconducting RF (SRF) photoinjector cavities at vertical tests to around 55 MV/m. This was achieved with niobium cathode plugs directly screwed to the cavity back wall omitting an RF choke filter and a load lock system for cathodes. Copper demonstrated being a suitable cathode material in normal conducting injector cavities used at X-Ray Free Electron Lasers (XFELs) operating with pulsed RF. In this article we present the first experimental confirmation that peak field on axis gradients around 55 MV/m and beyond can be achieved in L-band SRF photoinjector cavities with copper cathode plugs screwed to the cavity back wall. We view this as a major milestone for the development of a high gradient photoinjector operating continuous wave (CW)