Philip Burrows

Abstract:

Beams of uniform transverse beam profile are desirable for a variety of applications such as irradiation experiments. The generation of beams with such profiles has previously been investigated as a method of reducing emittance growth. These methods, however, often use complicated optics setups or short, femtosecond laser pulse lengths. In this paper, we demonstrate that if ultra low emittance is not the target of the photoinjector, it is possible to produce transversely uniform beam profiles using a simple Gaussian laser, with a bunch length of a few picoseconds, utilising space-charge effects only.

Abstract:

FLASH radiation therapy calls for the delivery of fast bursted spills of particles with dose delivery times of the order of milliseconds. The requirements overlap with fundamental physics experimental requests that are being studied at CERN, albeit at very different energy scales. In this contribution, a scheme for extracting millisecond bursts from synchrotrons is explored by controlling a third-integer resonant and chromatic extraction with RF phase displacement acceleration. The scheme would be implementable in existing medical and experimental synchrotron facilities. Using a model of the CERN Proton Synchrotron, both single-burst and multi-burst extractions are simulated. Results show that 80 - 90 % of the total beam intensity is extracted in a single burst of 40 − 60 ms. This would correspond to a ∼10 ms burst in a typical medical synchrotron, namely the one outlined in the Proton Ion Medical Machine Study. A set of 3 consecutive bursts of 30 ms was simulated in the Proton Synchrotron with optimised machine parameters.

Abstract:

The Advanced Wakefield Experiment (AWAKE) at CERN investigates the plasma-wakefield acceleration of electrons driven by a relativistic proton bunch. After successfully demonstrating the acceleration process in Run 1, the experiment has now started Run 2. AWAKE Run 2 consists of several experimental periods that aim to demonstrate the feasibility of the AWAKE concept beyond the acceleration experiment, showing its feasibility as accelerator for particle physics applications. As part of these developments, a dramatic effort in improving the AWAKE instrumentation is sustained. This contribution reports on the current developments of the instrumentation pool upgrade, including the digital camera system for transverse beam profile measurement, the beam halo measurement and the spectrometer upgrade studies. Studies on the development of high-frequency beam position monitors are also described.

Abstract:

Resonant slow extraction from synchrotrons aims at providing constant intensity spills over timescales much longer than the revolution period of the machine. However, the extracted intensity is undesirably modulated by noise on the machine’s power converters with a frequency range of between 50 Hz and a few kHz. The impact of power converter noise can be suppressed by exploiting a Radio Frequency (RF) technique known as empty bucket channelling, which increases the speed at which particles cross the tune resonance boundary. In this contribution the implementation of empty bucket channelling in the CERN Proton Synchrotron (PS) is described via simulation and measurement. The technique was tested with both a resonant RF cavity and an inductive Finemet cavity, which can produce non-sinusoidal waveforms, to significantly reduce the low frequency noise observed on the extracted spill.

Abstract:

The International Linear Collider (ILC) is a proposed electron-positron collider targeting collision energies from 250 GeV to 1 TeV. With design luminosities of order 10³⁴ cm²s^⁻1 a beam-based, intra-train feedback system would be required near the Interaction Point (IP) to provide nanometre-level stabilisation of the beam overlap in the collisions. Here we present results from beam-tracking simulations of the 500 GeV ILC, including the impact of beam-trajectory imperfections on the luminosity, and the capability of the IP feedback system to compensate for them. Effects investigated include the position jitter introduced by the damping ring extraction kicker, short-range and long-range wakefields, and ground motion. The feedback system was shown to be able to correct for beam-beam offsets of up to 200 nm and stabilise the collision overlap to the nanometre level, within a few bunch crossings.