SRF cavity geometry optimization for the ILC with minimized surface e.m. fields and superior bandwidth

The main linacs of the ILC consist of nine-cell cavities based on the TESLA design. In order to facilitate reaching higher gradients we have re-designed the cavity shape. This leads to a reduction, comparable to several current designs, in both the ratio of the surface electric field to the accelerating field (Es/Ea) and the magnetic field to the accelerating field (Bs/Ea). The bandwidth of the accelerating mode is also optimized. This new shape, which we refer to as the New Low Surface Field (NLSF) design, bears comparison with the Ichiro, Re-entrant and LSF designs.Comment: Presented at the 23rd Particle Accelerator Conference (PAC09) Vancouver, Canad

Third Harmonic Cavity Modal Analysis

Third harmonic cavities have been designed and fabricated by FNAL to be used at the FLASH/XFEL facility at DESY to minimise the energy spread along the bunches. Modes in these cavities are analysed and the sensitivity to frequency errors are assessed. A circuit model is employed to model the monopole bands. The monopole circuit model is enhanced to include successive cell coupling, in addition to the usual nearest neighbour coupling. A mode matching code is used to facilitate rapid simulations, incorporating fabrication errors. Curves surfaces are approximated by a series of abrupt transitions and the validity of this approach is examinedComment: Proceedings of 14th International Conference on RF Superconductivity (SRF 2009), 2009, Berlin, German

Study of Beam Diagnostics with Trapped Modes in Third Harmonic Superconducting Cavities at FLASH

Off-axis beams passing through an accelerating cavity excite dipole modes among other higher order modes (HOMs). These modes have linear dependence on the transverse beam offset from the cavity axis. Therefore they can be used to monitor the beam position within the cavity. The fifth dipole passband of the third harmonic superconducting cavities at FLASH has modes trapped within each cavity and do not propagate through the adjacent beam pipes, while most other cavity modes do. This could enable the beam position measurement in individual cavities. This paper investigates the possibility to use the fifth dipole band for beam alignment in the third harmonic cavity module. Simulations and measurements both with and without beam-excitations are presented. Various analysis methods are used and compared. A good correlation of HOM signals to the beam position is observed.Comment: 2nd International Particle Accelerator Conference (IPAC '11), San Sebastian, Spain, Sep 4-9, 201

Rapid cavity prototyping using mode matching and globalised scattering matrix

Cavity design using traditional mesh based numerical means (such as the finite element or finite difference methods) require large mesh calculations in order to obtain accurate values and cavity optimisation is often not achieved. Here we present a mode matching scheme which utilises a globalised scattering matrix approach that allows cavities with curved surfaces (i.e. cavities with elliptical irises and or equators) to be accurately simulated allowing rapid cavity prototyping and optimisation to be achieved. Results on structures in the CLIC mainComment: Proceedings of X-Band Structures and Beam Dynamics Workshop (XB08), 44th ICFA beam dynamics workshop, cockcroft institute, uk, 1-4 dec. 200

Public Safety Personnel and the Use of Peer-to-Peer Mental and Emotional Support Through Social Media

The emotional and mental health of public safety personnel has been a topic that is continuing to receive attention. Being exposed to multiple traumatic events takes a mental and emotional toll on those who place their lives in harm’s way to help others. The study was based on social cognitive theory which focused on self-efficacy through social influences and environment. The purpose of this study was to understand the experience of public safety personnel’s training regarding their perceptions to mitigate emotional stress; the experience of public safety personnel with seeking mental health services; experience of public safety personnel with the stigma of receiving mental health services; the experience of public safety personnel’s use of online social networks for emotional support; and the experience of peer-to-peer online support for mental health and receiving mental health services. The research design was basic qualitative with an open-ended questionnaire through a link placed into public safety Facebook groups. Nvivo software was used to code and identify themes for interpretation. The results showed inadequate initial and ongoing mental health training along with negative experiences when seeking mental health services. Mental health stigma has changed, but some participants still felt there was a stigma with seeking mental health services. Peer-to-Peer online support had positive results toward mental health when participants felt stigma amongst coworkers. Findings may be used for positive social change by providing adequate initial mental health training needs. Online peer-to-peer support may be the first step if a person is not ready to seek professional help and public safety personnel need specialized mental health due to the type of traumas they are exposed to each shift

Functional immunoglobulin transgenes guide ordered B-cell differentiation in Rag-1-deficient mice

We have examined the regulatory role of the individual components of the immunoglobulin antigen receptor in B-cell development by transgenic complementation of Rag-1 deficient (Rag-1⁻) mice. Complementation with a membrane µ heavy chain (µHC) gene allows progression of developmentally arrested Rag-1⁻ pro-B-cells to the small pre-B cell stage, whereas the introduction of independently integrated µHC and κ light chain (κLC) transgenes promotes the appearance of peripheral lymphocytes which, however, remain unresponsive to external stimuli. Complete reconstitution of the B-cell lineage and the emergence of functionally nature Rag-1⁻ peripheral B cells is achieved by the introduction of cointegrated heavy and light chain transgenes encoding an anti-H-2^k antibody. This experimental system demonstrates the competence of the µHC and κLC to direct and regulate the sequential stages of B-cell differentiation, defines the time at which negative selection of self-reactive B cells occurs, and shows that elimination of these cells occurs equally well in the absence of Rag-1 as in its presence. These data also support the hypothesis that Rag-1 directly participates in the V(D)J recombination process

Lineage specification and plasticity in CD19− early B cell precursors

We describe here three CD19− B cell precursor populations in mouse bone marrow identified using 12-color flow cytometry. Cell transfer experiments indicate lineage potentials consistent with multilineage progenitor (MLP), common lymphoid progenitor (CLP), and B lineage–restricted pre-pro–B (Fr. A), respectively. However, single cell in vitro assays reveal lineage plasticity: lymphoid/myeloid lineage potential for CLP and B/T lineage potential for Fr. A. Despite myeloid potential, recombination activating gene 2 reporter activation is first detected at low levels in most MLP cells, with 95% of CLPs showing 10-fold increased levels. Furthermore, single cell analysis shows that half of CLP and 90% of Fr. A cells contain heavy chain DJ rearrangements. These data, together with expression profiles of lineage-specific genes, demonstrate progressive acquisition of B lineage potential and support an asynchronous view of early B cell development, in which B lineage specification initiates in the MLP/CLP stage, whereas myeloid potential is not lost until the pre-pro–B (Fr. A) stage, and B/T lymphoid plasticity persists until the CD19+ pro–B stage. Thus, MLP, CLP, and Fr. A represent progressively B lineage–specified stages in development, before the CD19+ B lineage–committed pro–B stage

Status of COLDDIAG: A Cold Vacuum Chamber for Diagnostics

One of the still open issues for the development of superconducting insertion devices is the understanding of the beam heat load. With the aim of measuring the beam heat load to a cold bore and the hope to gain a deeper understanding in the beam heat load mechanisms, a cold vacuum chamber for diagnostics is under construction. The following diagnostics will be implemented: i) retarding field analyzers to measure the electron energy and flux, ii) temperature sensors to measure the total heat load, iii) pressure gauges, iv) and mass spectrometers to measure the gas content. The inner vacuum chamber will be removable in order to test different geometries and materials. This will allow the installation of the cryostat in different synchrotron light sources. COLDDIAG will be built to fit in a short straight section at ANKA. A first installation at the synchrotron light source Diamond is foreseen in June 2011. Here we describe the technical design report of this device and the planned measurements with beam.Comment: Presented at First International Particle Accelerator Conference, IPAC'10, Kyoto, Japan, from 23 to 28 May 201