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

The career paths of researchers in long-term employment on short-term contracts: case study from a UK university

The career stage between PhD and lectureship, conventionally called “postdoctoral”, has traditionally been seen as transitional. However, with an estimated one third of university researchers in the United Kingdom having been employed on temporary contracts for more than 10 years, the transitional nature of this career stage is questionable. Despite so many research staff being in long-term employment on short-term contracts, the lack of visibility of this population, which does not have a legitimate place within the current academic career structure, means that we do not know how deliberate or accidental their career choices are. Based on semi-structured interviews with long-term researchers (LTRS) at one university in the United Kingdom, this is the first study to investigate the personal and professional circumstances behind the career path of long-term researchers on temporary contracts. Three categories of LTRS were identified: 1) the candidate, who wants to follow the traditional academic career pathway and to secure a lectureship 2) the accidental long-term researcher, who did not or could not plan their career path 3) the career researcher, who sustains a research-only career despite the precarity of such positions. Most participants had belonged successively to two categories. Some obstacles to career progression transcended the categories: inequal access to opportunities for developing one’s teaching portfolio, poor or lack of managerial support, the perceived prestige or lack thereof of one’s field, and bullying and discrimination. We argue that short-termism and lack of visibility play down considerably the contribution of long-term researchers to the financial and academic success of research institutions. We also argue that traditional–but still in place–structures in academia are ill adapted to the contemporary demographics and practices of the research community; we recommend that future studies involve HE sector stakeholders to review and to reform the academic career structure

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

Exploring the Impact of Suicidal Behaviour on Staff Working in Acute Psychiatric Inpatient Services

This thesis was interested in exploring the experience of working with service users’ suicidal behaviour for staff working in acute psychiatric inpatient services. The first section of this portfolio comprises a literature review of the existing research exploring the impact of service user suicide on mental health professionals working in acute psychiatric inpatient settings. Nine papers were identified utilising a systematic search strategy. Their quality was appraised using a combination of the QualSyst Tool and the Critical Appraisal Skills Programme Checklist. Their results were further synthesised through narrative analysis. Findings suggested that service user suicide had an emotionally significant impact on staff which tended to be hidden in the workplace. The experience of ‘non-qualified’ staff, however, was missing in the literature. The second portion of this portfolio outlines the results of an empirical paper, qualitatively exploring the experience of suicidal behaviour (attempted and completed suicide) on ‘non-qualified’ staff based in acute psychiatric inpatient settings. Semi-structured interviews were utilised to interview 10 staff’s experiences and data was analysed using Reflexive Thematic Analysis. Four themes were highlighted; ‘Direct personal impact’, ‘Unrealistic expectations’, ‘Attempting to contain impact’ and ‘Acclimatisation’, containing 10 sub-themes. The results provided insight into the specific experience of working with suicidal behaviour as a non-qualified member of staff, and recommendations are suggested to improve perceived support in its aftermath. The final section of this portfolio is an executive summary of the empirical paper. This has been developed to be disseminated to those who have expressed an interest in the research and for those with organisational responsibility of acute psychiatric inpatient settings