Novel hybrid multipolar RF cavities for transverse beam manipulations

This thesis describes the development and application of a method for tailoring the profile of electromagnetic fields in RF cavities for use in particle accelerators. This so-called azimuthal modulation method (AMM) is underpinned by an analytic expression of the basis of the electromagnetic modes in closed RF cavities whose cross-sections vary with the azimuth. This basis is derived and the notation {M}ηp is introduced to describe the azimuthal, radial and longitudinal form of the modes. The scope of the AMM for designing realisable cavities is explored. The underlying reasons for the limitations on the range of magnitudes and orientations of multipoles that can be supported by azimuthally modulated cavities are derived and discussed. This understanding provides the foundation for the latter half of the thesis where numerous applications of the AMM are presented. First, the AMM is used to construct a prototype cavity that supports a 3 GHz mode which could be used for the simultaneous acceleration and focusing of a particle beam. Experimental testing supported the multipolar content of the mode being as designed. Second, the AMM is applied to create RF cavities which support modes free from unwanted multipoles generated by power couplers and tuning pins. An example design of an RF structure which incorporates a single-slot power coupler and supports an accelerating mode free from dipole, quadrupole, sextupole and octupole components is analysed. Third, the AMM is used to design RF cavities that support modes tailored for the off-axis traversal of particle beams. An example optimisation of an accelerating field that remains as flat as possible along the horizontal is presented. Finally, the AMM also finds application in the creation of musical drums. This concept inspired an outreach workshop that was designed and delivered to showcase this research to 11-14 year-old school students

Creating Exact Multipolar Fields with Azimuthally Modulated RF Cavities

RF cavities used in modern particle accelerators operate in TMm10-like modes composed of a single, dominant multipole of order m; m = 0 modes are used for the longitudinal acceleration of a particle beam and m ̸= 0 modes for controlling transverse beam dynamics. The practical design of the latter, however, can be complex and require extensive analysis through the iteration of both approximate mathematical models and computationally expensive simulations to optimise the performance of the structure. In this paper we present a new, systematic method for designing azimuthally modulated RF cavities that support modes composed of any number and magnitude of user-specified transverse multipoles, either with or without a longitudinally accelerating component. Two case studies are presented of RF cavity designs that support modes composed of a longitudinally accelerating field in addition to a single transverse multipole, and designs that support modes composed of two transverse multipoles. We discuss generalising the discoveries and conclusions from the two case studies to designing cavities that support modes composed of any number of multipoles. The theoretical work is verified with analysis of 3D simulations and experimental measurements are presented of a cavity operating in a 3 GHz mode that simultaneously longitudinally accelerates and transversely focuses a beam

Minimising Transverse Multipoles in Accelerating RF Cavities via Azimuthally Modulated Designs

In this paper, we build upon previous work of designing RF structures that support modes with tailored multipolar fields by applying the concept to negate the transverse multipoles in accelerating RF cavities caused by the incorporation of waveguide slots and tuning deformations. We outline a systematic method for designing structures that minimise these transverse multipoles and present analysis of simulations of two different minimisation designs

Creating Exact Multipolar Fields in Accelerating RF Cavities via an Azimuthally Modulated Design

In this paper, we present a novel method for designing RF structures with specifically tailored multipolar field contributions. This has a range of applications, including the suppression of unwanted multipolar fields or the introduction of wanted terms, such as for quadrupole focusing. In this article, we outline the general design methodology and compare the expected results to 3D CST simulations

Abstract D066: A prospective study on chemotherapy-induced anemia using serial hemoglobin measurement in cancer patients undergoing treatment at National Hospital Abuja, Nigeria

Anaemia is a common complication of myelo-suppressive chemotherapy. Severe anaemia is usually treated with red blood cell transfusion, however, mild-to-moderate anaemia are most often managed conservatively. There is no universally established benchmark for haemoglobin of patients selected for cancer chemotherapy to guide a global best practice and enhance patients treatment outcome and their quality of life. Objective: The objective of this study is to examine the change in Hb levels of cancer patients undergoing chemotherapy measuring Hb after treatment. Materials & Methods: A total of 100 voluntary patients with solid malignancies were recruited within a period of eight (8) months. Baseline demographic characteristics and type of tumours were documented. Pre-treatment Hb level was measured on the first day of consultation and repeated every 2 weeks during and after the therapy until after three consecutive Hb readings (6 weeks). Results & Analysis: All data were analysed using IBM statistical package for Social Science (SPSS) version 20. 88 of the 100 cancer patients were female. Breast 68% (68) was the commonest site of tumour. Prevalence of anaemia in the study was 72% and majority of the patients had their Hb within the range of 9.60 g/dl to 10.62 g/dl at the end of their treatment. At P-value >0.05 and standard deviation there was no statistical significance on distribution of mean haemoglobin values, were independent of sex and type of treatment. Conclusion and Recommendation: Our results show that chemotherapy has no significant effect on Hb level between 11 g/dl to 12 g/dl. Prevalence of anaemia in the cohort of patients was 72%. We recommend a benchmark minimum of Hb of 11 g/dl for all patients being selected for chemotherapy in Nigeria

A Design for a 3 TeV Rapid Cycling Synchrotron for Muon Acceleration in the SPS Tunnel

Current proposals for new high-energy physics machines either focus on building ever-larger circular hadron colliders, such as the proposed FCC- hh, or on electron-positron linac designs, such as CLIC and ILC. However, muon colliders present an alternative approach to probing new physics at the energy frontier while also offering a number of advantages over hadron or electron-positron colliders. A detailed design for the acceleration stage of a future 3 TeV centre of mass energy muon collider is proposed. The acceleration of muons to 1.5 TeV would be achieved in two hybrid Rapid Cycling Synchrotrons (RCSs), which would both be situated in the existing SPS tunnel at CERN. RCS1 would accelerate counter rotating muons and antimuons from 100 GeV to 900 GeV before they would be injected into RCS2 where they would then be accelerated up to 1.5 TeV. The lattice design was optimised to fit into the SPS tunnel and two dispersion suppressor schemes are presented. Longitudinal simulations were performed in order to study beam loss and collective effects over the acceleration cycle. A radiofrequency cavity was designed, where the optimal frequency and cavity geometry were investigated, before being modelled in 3D. Designs for the normal conducting dipoles and quadrupoles are presented, which meet the requirements detailed in the lattice design while also minimising power consumption. Radiation deposition in the accelerator was also investigated, along with a study on the environmental exposure from neutrino radiation

Comparative Analysis of Radiotherapy Linear Accelerator Downtime and Failure Modes in the UK, Nigeria and Botswana

The lack of radiotherapy linear accelerators (LINACs) in Low- and Middle- Income Countries (LMICs) has been recognised as a major barrier to providing quality cancer care in these regions, along with a shortfall in the number of highly qualified personnel. It is expected that additional challenges will be faced in operating precise, high tech radiotherapy equipment in these environments, and anecdotal evidence suggests that LINACs have greater downtime and higher failure rates of components than their counterparts in High-Income Countries. To guide future developments such as the design of a LINAC tailored for use in LMIC environments, it is important to take a data-driven approach to any re-engineering of the technology. However, no detailed statistical data on LINAC downtime and failure modes has been previously collected or presented in the literature. This work presents the first known comparative analysis of failure modes and downtime of current generation LINACs in radiotherapy centres, with the aim of determining any correlations between LINAC environment and performance. Logbooks kept by radiotherapy personnel on the operation of their LINAC were obtained and analysed from centres in Oxford (UK), Abuja, Benin, Enugu, Lagos, Sokoto (Nigeria) and Gaborone (Botswana). By deconstructing the LINAC into 12 different subsystems, it is found that the vacuum subsystem only fails in the LMIC centres and the failure rate in an LMIC environment is more than twice as large in 6 of the 12 subsystems compared to the High Income Country (HIC). Additionally, it is shown that despite accounting for only 3.4% of total number of faults, the LINAC faults which take more than an hour to repair account for 74.6% of the total downtime. The results of this study inform future attempts to mitigate the problems affecting LINACs in LMIC environments