Julian McKenzie

The influence of high intensity terahertz radiation on mammalian cell adhesion, proliferation and differentiation.

Understanding the influence of exposure of biological systems to THz radiation is becoming increasingly important. There is some evidence to suggest that THz radiation can influence important activities within mammalian cells. This study evaluated the influence of the high peak power, low average power THz radiation produced by the ALICE (Daresbury Laboratory, UK) synchrotron source on human epithelial and embryonic stem cells. The cells were maintained under standard tissue culture conditions, during which the THz radiation was delivered directly into the incubator for various exposure times. The influence of the THz radiation on cell morphology, attachment, proliferation and differentiation was evaluated. The study demonstrated that there was no difference in any of these parameters between irradiated and control cell cultures. It is suggested that under these conditions the cells are capable of compensating for any effects caused by exposure to THz radiation with the peak powers levels employed in these studies.

Development of high brightness, high repetition rate photoelectron injectors at STFC Daresbury Laboratory

Accelerator drivers for Energy Recovery Linac (ERL) and Free-Electron Laser (FEL) based light sources demand electron injectors which deliver high brightness bunches on the several hundreds of picocoulomb scale, at repetition rates between 1 MHz and 1 GHz (or higher), corresponding to an average current between 0.1 and 100 mA. Simultaneous satisfaction of these injector requirements is considerably beyond the current state-of-the-art. Daresbury Laboratory is concentrating efforts on the development of high average current III-V and XnY3?nSb photocathode-based DC and SRF photocathode guns for ERL applications. The ultimate goal of this research is their integration with the ALICE ERL.

Photocathode Preparation System for the ALICE Photoinjector

ALICE—Accelerators and Lasers in Combined Experiments—is a relatively new accelerator built at Daresbury Laboratory that will demonstrate the process of energy recovery by the end of 2008. The project is a research facility to develop the technology required to build a New Light Source (NLS) in the UK. This paper details the current ALICE photoinjector design and highlights the limitations before focusing on a photoinjector upgrade. The key component of the upgrade is a three‐stage extreme high vacuum load‐lock system that will be incorporated into the ALICE photoinjector in 2010. The load‐lock system has de facto become a standard component of a type III–V semiconductor photocathode injector and comprises: 1) loading chamber to allow new photocathodes to be introduced, 2) cleaning chamber for atomic hydrogen cleaning of the photocathodes and, 3) a preparation and activation chamber where the photocathodes will be activated to the NEA state ready for use on the ALICE accelerator. Once commissioned the loa...

The ALICE Energy Recovery Linac – Project overview and injector performance

The ALICE accelerator (Accelerators and Lasers In Combined Experiments) at Daresbury Laboratory is a 35 MeV ERL. The electron beam drives an infra-red free-electron laser (FEL) and THz light sources, but can also be used to generate X-rays through Compton back-scattering (CBS). ALICE also acts as the injector for the EMMA NS-FFAG machine. This paper will outline the project status and milestones achieved thus far, focussing on the status and performance of the photoinjector gun and the injection line.

Beam Characterisation and Machine Developments at VELA

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3D Modeling of the ALICE Photoinjector Upgrade

The injector for the ALICE machine (Accelerators and Lasers In Combined Experiments) at Daresbury Laboratory is based around a 350 kV DC photocathode electron gun. An upgrade is proposed to introduce a load‐lock GaAs photocathode preparation facility to allow rapid transfer of photocathodes to the gun without breaking the vacuum system. In the current design this requires side‐loading of the photocathodes into the cathode ball. An alternative is to relocate the ceramic insulator vertically which will allow back‐loading and also backillumination of the photocathodes. 3D electrostatic simulations of the gun chamber are presented for both options along with 3D beam dynamic simulations for an off‐axis photocathode, introduced to increase photocathode lifetime by reducing damage by ion backbombardment. Beam dynamic simulations are also presented for the entire injector beamline as well as for a proposed extension to the injector beamline to include a diagnostic section.