In this work we investigate superconducting properties of niobium samples via application of the muon spin rotation/relaxation (muSR) technique. We employ for the first time the muSR technique to study samples that are cutout from large and small grain 1.5 GHz radio frequency (RF) single cell niobium cavities. The RF test of these cavities was accompanied by full temperature mapping to characterize the RF losses in each of the samples. Results of the muSR measurements show that standard cavity surface treatments like mild baking and buffered chemical polishing (BCP) performed on the studied samples affect their surface pinning strength. We find an interesting correlation between high field RF losses and field dependence of the sample magnetic volume fraction measured via muSR. The muSR line width observed in ZF-muSR measurements matches the behavior of Nb samples doped with minute amounts of Ta or N impurities. An upper bound for the upper critical field Hc2 of these cutouts is found.

The e-Linac project at TRIUMF, now funded, is specified to accelerate 10 mA of electrons to 50 MeV using 1.3 GHz multi-cell superconducting cavities. The linac consists of three cryomodules; an injector cryomodule with one cavity and two accelerating modules with two cavities each. The injector module is being designed and constructed in collaboration with VECC in Kolkata. The design utilizes a unique box cryomodule with a top-loading cold mass. A 4 K phase separator, 4 K / 2 K heat exchanger and JouleThomson valve are installed within each module to produce 2 K liquid. The design and status of the development are presented.

The ILC crab cavities require very tight phase control in order to achieve the desired luminosity increase at the interaction point. In order to test the performance of the phase control system designed to lock the cavities, two single-cell superconducting cavities were built and tested in a liquid helium cryostat. The preparation of the cavities, and design of the cryostat support structure are detailed in this paper, as is the performance of the phase control system. EXPERIMENTAL SET-UP The experimental set-up was described in a previous report [1]. Briefly, it consists of a magnetically shielded vertical helium vessel containing both cavities. A Labview interface allows us to monitor and log temperature, helium level and gas flows. A pump allows us to cool the system to 2K when required.

Due to the combination of fixed magnetic field operation with strong focusing, non-scaling FFAGs have a significant potential for future particle accelerator applications. However, this technology has a number of unique features, which must be fully studied before this potential can be realised. To do this, a proof-of-principle non-scaling FFAG, called EMMA – Electron Model for Many Applications – has been constructed at the STFC Daresbury Laboratory in the UK. It has been designed by an international collaboration of accelerator scientists and engineers. It will demonstrate the principle of non-scaling FFAGs and be used to study the features of this type of accelerator in detail.

The status of the PAMELA (Particle Accelerator for MEdical Applications) project to design an accelerator for proton and light ion therapy using non-scaling Fixed Field Alternating Gradient (ns-FFAG) accelerators is reviewed and discussed.

ALICE (Accelerators and Lasers in Combined Experiments) is a 35 MeV energy recovery linac based light source. ALICE is being developed as an experimental test-bed for a broad suite of science and technology activities that make use of electron acceleration and ultra-short pulse laser techniques. ALICE utilises two super-conducting radio frequency (SRF) cryomodules, each with two identical 9-cell, 1.3 GHz cavities that are powered by 5 inductive output tubes (IOTs) from 3 different commercial suppliers. The experience gained in both commissioning these systems and ultimately operating for energy recovery is presented. Developments for a new ERL cryomodule upgrade for ALICE are also described.

A superconducting RF vertical test facility (VTF) has been constructed at Daresbury Laboratory to enable the commissioning of an ILC Crab Cavity LLRF Control System. Two single cell 3.9 GHz dipole mode cavities were tested simulataneously to enable the evaluation of the control system. Careful tuning of the cavities for frequency and external Q factors enabled a low noise reference oscillator to be utilised. Several tests have been performed throughout the past 12 months, each test enabling a much improved system performance. The system is described, and the latest performance of the system is presented. EXPERIMENTAL SET-UP

The PAMELA project(Particle Accelerator For MEdical Applications) currently consists of the design of a particle therapy facility. The project, which is in the design phase, contains Non-Scaling FFAG, particle accelerator capable of rapid beam acceleration, giving a pulse repetition rate of 1kHz, far beyond that of a conventional synchrotron. To realise the repetition rate, a key component of the accelerator is the rf accelerating system. The combination of a high energy gain per turn and a high repetition rate is a significant challenge. In this paper, options for the rf system of the proton ring and the status of development are presented.

This report describes a LLRF system developed at Lancaster University and an experiment undertaken at the STFC Daresbury Laboratory by Cockcroft Institute Staff to validate an approach to phasing the crab cavities for the International Linear Collider. The work has involved the manufacture and processing of a pair superconducting cavities, the development of a vertical cryostat facility, the development of a digital control system for each cavity and the development of an interferometer. In a test conducted during August 2008 it was demonstrated that an RF interferometer with digital phase detection and digital cavity controllers can lock a pair of superconducting cavities having realistic levels of microphonics such that r.m.s. phase errors are less than 120 millidegrees at 3.9 GHz. 1. Engineering Department, Lancaster University, Cockcroft Institute, Lancaster, LA1 4YR 2. ASTeC, STFC Daresbury Laboratory, Daresbury, Warrington, Cheshire, WA4 4AD, UK EUROTeV-Report-2008-073 December 2008 2 of 67 3.

The PAMELA (Particle Accelerator for MEdicaL Applications) project is to design an accelerator for proton and light ion therapy using non-scaling Fixed Field Alternating Gradient (FFAG) accelerators, as part of the CONFORM project, which is also constructing the EMMA electron model of a non-scaling FFAG at Daresbury. This paper presents an overview of the PAMELA design, and a discussion of the design goals and the principles used to arrive at a preliminary specification of the accelerator.

The main accelerating cavities of the ILC provide acceleration of both positron and electron beams to 250 GeV per beam and 500 GeV per beam in a proposed upgrade. The wake-fields excited by each ultra-relativistic beam in the accelerating cavities can cause appreciable dilution of the beam emittance. Each cavity is supplied with both fundamental and higher order mode couplers. The geometrical configuration of these rf couplers results in an asymmetrical field and this gives rise to both an rf kick being applied to the beam and a transverse wake- field. Detailed electromagnetic (e.m.) fields are simulated in the vicinity of the couplers in order to assess the impact on the beam dynamics for the ALICE/ERLP (1) couplers.

The BBU threshold in ERLs is a limitation on the maximum beam current due to the interaction of the electron bunches and the Higher Order Modes (HOMs) contained within the RF cavities. Several factors are involved in determining the threshold current; from the cavity the Q, R/Q and degeneracy of the modes all play an important part. From the beam transport the values of the lattice functions α, β and μ have an effect. We will discuss the limits on these variables to provide a BBU current threshold greater than 100 mA for a multiple cavity machine and what will be required to provide higher currents. Also three different cavity profiles were investigated with the aim of reducing the BBU threshold. The TESLA 9-cell cavity was used as a baseline for comparison against possible 7-cell cavity designs, using the TESLA cell shape for their inner cells. The ends of the 7-cell cavities join to different sized beampipes, with radii of 39 mm and 54 mm, to allow most of the HOMs to propagate to a broadband HOM absorber. Two different beampipe to cavity to transitions were investigated. The optimised 7-cell cavity will be shown to provide an increase in the BBU threshold.

A superconducting RF vertical test facility (VTF) has been constructed at Daresbury Laboratory for the testing of superconducting RF cavities at 2K. When fully operational, the facility will be capable of testing a 9-cell 1.3 GHz Tesla type cavity. The facility is initially to be configured to perform phase synchronisation experiments between a pair of single cell 3.9GHz ILC crab cavities. These experiments require the cavities to operate at the same frequency; therefore a tuning mechanism has been integrated into the system. The system is described, and data from the initial operation of the facility is presented.

Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.

The Cockcroft Institute is a newly created international centre for Accelerator Science and Technology in the UK. It is a joint venture between the Universities of Lancaster, Liverpool and Manchester, and the Science and Technology Facilities Council. The Cockcroft Institute has a large expertise base in Wakefields and Impedances which is linked through the Cockcroft Institute Wakefields Interest Group. Members of this group have experience in wakefields in linear colliders, ring colliders, light sources as well as generic fundamental research and focus on a wide range of specialist areas. In this article we summarize the work performed in this important field of research at the Cockcroft Institute.

The ILC reference design report (RDR) recommends a 14 mrad crossing angle for the positron and electron beams at the IP. A matched pair of crab cavity systems are required in the beam delivery system to align both bunches at the IP. The use of a multi-cell, 3.9 GHz dipole mode superconducting cavity is proposed, derived from the Fermilab CKM cavity being developed as a beam slice diagnostic [1]. Dipole-mode cavities phased for crab rotation are shifted by 90deg with respect to similar cavities phased for deflection. Uncorrelated phase errors of 0.086deg (equivalent to 61 fs) for the two cavity systems, gives an average of 180 nm for the relative deflection of the bunch centers. For a horizontal bunch size sigma x = 655 nm, a deflection of 180nm reduces the ILC luminosity by 2%. The crab cavity systems are to be placed ~30 m apart and synchronization to within 61 fs is required; this is on the limit of what is presently achievable. This paper describes LLRF circuits under development at the Cockcroft Institute for proof of principle experiments planned on the ERLP at Daresbury and on the ILCTA test beamline at FNAL. Simulation results for stabilisation performance are also given.