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| MOPRI046 | The Evolution of the Transverse Energy Distribution of Electrons from a GaAs Photocathode as a Function of its Degradation State | 707 |
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The brightness of a photoelectron injector is fundamentally limited by the mean longitudinal and transverse energy distributions of the photoelectrons emitted from its photocathode, and the electron beam brightness is increased significantly if the mean values of these quantities are reduced. ASTeC have commissioned a Transverse Energy Spread Spectrometer (TESS – an experimental facility designed to measure these transverse and longitudinal energy distributions) which can be used for III-V semiconductor, alkali antimonide/telluride and metal photocathode research*. GaAs photocathodes were activated in our photocathode preparation facility (PPF)**, then transferred to TESS under XHV conditions and progressively degraded through controlled exposure to oxygen. We present commissioning data and initial measurements showing the evolution of the transverse energy distribution of electrons from GaAs photocathodes as a function of their degradation state.
* Proc. FEL ’13, TUPPS033, 290-293 ** Proc. IPAC ’11, THPC129, 3185-3187 |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI046 | |
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| MOPRI047 | The Preparation of Atomically Clean Metal Surfaces for use as Photocathodes in Normally Conducting RF Guns | 711 |
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Funding: Research supported by FP7 EuCard2 http://cern.ch/eucard2 This work reports a study of various alternative metal samples as candidate materials for use as photocathodes in normally conducting RF guns. Clean surfaces were prepared using Argon ion bombardment and quantum efficiency measured using a 265 nm UV LED light source with a picoammeter for drain current monitoring. Surface composition was studied using X-ray photoelectron spectroscopy and a Kelvin probe apparatus provided work function measurements. Data was taken both before and after annealing to 200°C, a temperature that is routinely achieved during RF gun vacuum baking. Ion bombardment typically leaves a very rough surface that can have a detrimental effect on beam emittance, so further work will focus on the use of Oxygen plasma cleaning of the best candidate alternative metals. An oxygen plasma treated Copper photocathode has been shown to produce an acceptable level of quantum efficiency in the VELA accelerator at Daresbury Laboratory. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI047 | |
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| MOPRI051 | Measurements of the Longitudinal Energy Distribution of Low Energy Electrons | 720 |
| SUSPSNE030 | use link to see paper's listing under its alternate paper code | |
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Funding: Work supported by STFC Cockcroft Core Grant No.ST/G008248/1 The Transverse Energy Spread Spectrometer (TESS) is an ASTeC experiment designed to measure the energy of electrons from different cathode materials. It is a dedicated test stand for future light sources. A full particle tracking code has been developed in the QUASAR Group, which simulates particle trajectories through TESS. Using this code it is possible to simulate different operational conditions of the experiment and cathode materials. The simulation results can then be benchmarked against experimental data to test the validity of the emission and beam transport model. Within this paper, results from simulation studies are presented and compared against experimental data as a collaboration within the Cockcroft Institute between ASTeC and the QUASAR Group for the case of measuring the longitudinal velocity distribution of electrons emitted from a gallium arsenide cathode using a grid structure as an energy filter. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI051 | |
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| TUPME081 | Plasma Wakefield Acceleration at CLARA PARS | 1544 |
| SUSPSNE025 | use link to see paper's listing under its alternate paper code | |
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| PARS is a proposed Plasma Accelerator Research Station using the planned CLARA (Compact Linear Accelerator for Research and Applications) electron linear accelerator at Daresbury Laboratory in the UK. In this paper, two- dimensional particle-in-cell simulations based on realistic CLARA beam parameters are presented. The results show that an accelerating gradient of 2.0 GV/m can be achieved over an accelerating length of at least 13 cm. Preliminary simulation results for a two bunch scheme show an energy gain of 70% over a length of 13 cm, giving an average accelerating gradient of 1.2 GeV/m. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME081 | |
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| WEPME083 | VELA: A New Accelerator Technology Development Platform for Industry | 2471 |
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| The Versatile Electron Linear Accelerator (VELA) facility will provide enabling infrastructures targeted at the development and testing of novel and compact accelerator technologies, specifically through partnership with industry and aimed at addressing applications in medicine, health, security, energy and industrial processing. The facility has now been commissioned at Daresbury Laboratory and the facility is now being actively utilised by industrial groups who are able to take advantage of the variable electron beam parameters available on VELA to either demonstrate new techniques and/or processes or otherwise develop new technologies for future commercial realisation. Examples of which to be presented include; demonstration of a new cargo scanning process, characterisation of novel, high performance beam position monitors, as well as other technology development applications. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME083 | |
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| THPRO029 | A Front End for the CLARA FEL Test Facility at Daresbury Laboratory | 2927 |
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| The next step towards the full CLARA facility is installation of the CLARA front end to comprise a 2m S-band linac section after the photoinjector gun. This will be suitable for both the velocity bunching and standard booster modes of CLARA. An S-bend will also be installed to deflect the beam into the current VELA line, enabling delivery of higher energy beams to two existing user areas. The current photoinjector beam diagnostics section can then be used to test a High Repetition Rate electron gun currently under development. We describe the proposed CLARA front end design. We define two beam dynamics working points for CLARA, one working point for sending beam from the CLARA Front End to VELA, and one working point to feed an interim user station prior to CLARA full construction in the straight-on position. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO029 | |
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| THPRO030 | Developments in CLARA Accelerator Design and Simulations | 2930 |
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| We present recent developments in the accelerator design of CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility at Daresbury Laboratory. Updates on the electron beam simulations and code comparisons including wakefields are described. Simulations of the effects of geometric wakefields in the small-aperture FEL undulator are shown, as well as further simulations on potential FEL experiments using chirped beams. We also present the results of simulations on post-FEL diagnostics. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO030 | |
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| THPRO051 | Cavity Design for a S-Band Photoinjector RF Gun with 400 Hz Repetition Rate | 2983 |
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| As part of the design of CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility at Daresbury Laboratory, a high repetition rate S-band photoinjector RF gun is being developed. This gun will be able to operate at up to 400 Hz repetition rate in single bunch mode. We present the initial cavity design including its optimisation for the beam dynamics of CLARA. We also present the initial cooling design for the cavity which will enable the high repetition rates to be achieved. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO051 | |
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| THPRO052 | Beam Physics Commissioning of VELA at Daresbury Laboratory | 2986 |
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| A user facility VELA (Versatile Electron Linear Accelerator) based on an RF photoinjector has been commissioned at Daresbury Laboratory in April 2013, providing beam to first users in September 2013. Machine study runs in 2013-2014 have concentrated on characterisation of main beam parameters like bunch charge, its momentum, beam emittance and dependence of these parameters on the launching RF phase. Major efforts have been also concentrated on investigation of the dark current from the gun and its dependence on the RF amplitude. Significant time has been dedicated to investigation of relative stability of LLRF and drive laser having significant impact on the overall machine stability. We present here the results of these studies. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO052 | |
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