IPAC2017 - List of Authors (Williams, P.H.)

Paper	Title	Page
WEPIK100	The Applicability of NEG Coated Undulator Vessels for the CLARA FEL Test Facility	3181
	O.B. Malyshev, K.B. Marinov, K.J. Middleman, N. Thompson, R. Valizadeh, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom O.B. Malyshev, K.J. Middleman, N. Thompson, R. Valizadeh, P.H. Williams Cockcroft Institute, Warrington, Cheshire, United Kingdom
	CLARA is a FEL test facility at Daresbury Laboratory (DL), UK. The undulator vacuum chamber is 20 m long with inner diameter 6 mm and its vacuum performance can benefit from a NEG coating. The thickness of the coating layer must be carefully optimised. A layer ~ 1 um would help the vacuum but a thinner layer would be partially transparent for the EM field reducing the resistive wall wakefields due to the NEG. A very thin layer, however, may not yield the necessary vacuum performance. Two types of NEG coatings produced at DL - dense and columnar - were considered. Their bulk conductivities were measured in a separate study. The resistive wall wakefield impedance was calculated following the standard approach for multilayer vessels. A 250 fs rms electron bunch was generated in ASTRA and its wakefield was obtained from the vessel impedance. The FEL performance was then studied through GENESIS simulations and the result compared to the case with no wakefields. It was found that NEG layers thicker than 100 nm give an unacceptable reduction of the FEL power and the vacuum performance of such thin coatings is unknown. Possible solutions to this problem are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK100
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THPAB053	Laser Heater Deisgn for the CLARA FEL Test Facility	3833
	A.D. Brynes, S.P. Jamison, B.D. Muratori, N. Thompson, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S.P. Jamison, B.D. Muratori, N. Thompson, P.H. Williams Cockcroft Institute, Warrington, Cheshire, United Kingdom
	We present considerations of microbunching studies in the CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility under construction at Daresbury Laboratory. CLARA, a high-brightness electron linac, presents an opportunity to study the microbunching instability. A number of theoretical models have been proposed concerning the causes of this instability, and it has also been observed at various FEL facilities. We have applied these models to the CLARA FEL, and propose a suitable laser heater design which will provide flexibility in terms of the range of modes of operation for CLARA. We also propose a method for inducing and controlling the microbunching instability via pulse stacking of the photoinjector laser.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB053
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WEPAB090	Developments in the CLARA FEL Test Facility Accelerator Design and Simulations	2787
	P.H. Williams, D.J. Dunning, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	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. The requirement to co-propagate the beam with laser seeds of very different wavelengths has led to a redesign of the section preceding the undulators, with a dogleg being replaced by a chicane. Additional refinements of the facility design include the inter-undulator sections. With this finalised design we show start to FEL simulations for all beam modes envisaged.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB090
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THPAB059	CSR and Space Charge Studies for the CLARA Phase 1 Beamline	3851
	B.S. Kyle, R.B. Appleby UMAN, Manchester, United Kingdom J.K. Jones, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom M.J. de Loos, S.B. van der Geer Pulsar Physics, Eindhoven, The Netherlands
	The installation of Phase 1 of CLARA, the UK's new FEL test facility, is currently underway at Daresbury Laboratory. When completed, it will be able to deliver 45 MeV electron beams to the pre-existing VELA beamline, which runs parallel. Phase 1 consists of a 10 Hz photocathode gun, a 2 m long S-band travelling wave linac, a spectrometer line, and associated optics and diagnostics. A detailed study into the beam dynamics of the lattice is presented, with a focus towards the effects of space charge and coherent synchrotron radiation on the electron bunch. Simulations disagreed with predictions from a one-dimensional model of coherent radiation, and this disagreement is believed to be due to a violation of the Derbenev criterion.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB059
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Paper

Title

Page

The Applicability of NEG Coated Undulator Vessels for the CLARA FEL Test Facility

3181

O.B. Malyshev, K.B. Marinov, K.J. Middleman, N. Thompson, R. Valizadeh, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
O.B. Malyshev, K.J. Middleman, N. Thompson, R. Valizadeh, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom

CLARA is a FEL test facility at Daresbury Laboratory (DL), UK. The undulator vacuum chamber is 20 m long with inner diameter 6 mm and its vacuum performance can benefit from a NEG coating. The thickness of the coating layer must be carefully optimised. A layer ~ 1 um would help the vacuum but a thinner layer would be partially transparent for the EM field reducing the resistive wall wakefields due to the NEG. A very thin layer, however, may not yield the necessary vacuum performance. Two types of NEG coatings produced at DL - dense and columnar - were considered. Their bulk conductivities were measured in a separate study. The resistive wall wakefield impedance was calculated following the standard approach for multilayer vessels. A 250 fs rms electron bunch was generated in ASTRA and its wakefield was obtained from the vessel impedance. The FEL performance was then studied through GENESIS simulations and the result compared to the case with no wakefields. It was found that NEG layers thicker than 100 nm give an unacceptable reduction of the FEL power and the vacuum performance of such thin coatings is unknown. Possible solutions to this problem are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK100

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAB053

Laser Heater Deisgn for the CLARA FEL Test Facility

3833

A.D. Brynes, S.P. Jamison, B.D. Muratori, N. Thompson, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S.P. Jamison, B.D. Muratori, N. Thompson, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom

We present considerations of microbunching studies in the CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility under construction at Daresbury Laboratory. CLARA, a high-brightness electron linac, presents an opportunity to study the microbunching instability. A number of theoretical models have been proposed concerning the causes of this instability, and it has also been observed at various FEL facilities. We have applied these models to the CLARA FEL, and propose a suitable laser heater design which will provide flexibility in terms of the range of modes of operation for CLARA. We also propose a method for inducing and controlling the microbunching instability via pulse stacking of the photoinjector laser.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB053

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB090

Developments in the CLARA FEL Test Facility Accelerator Design and Simulations

2787

P.H. Williams, D.J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

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. The requirement to co-propagate the beam with laser seeds of very different wavelengths has led to a redesign of the section preceding the undulators, with a dogleg being replaced by a chicane. Additional refinements of the facility design include the inter-undulator sections. With this finalised design we show start to FEL simulations for all beam modes envisaged.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB090

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAB059

CSR and Space Charge Studies for the CLARA Phase 1 Beamline

3851

B.S. Kyle, R.B. Appleby
UMAN, Manchester, United Kingdom
J.K. Jones, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
M.J. de Loos, S.B. van der Geer
Pulsar Physics, Eindhoven, The Netherlands

The installation of Phase 1 of CLARA, the UK's new FEL test facility, is currently underway at Daresbury Laboratory. When completed, it will be able to deliver 45 MeV electron beams to the pre-existing VELA beamline, which runs parallel. Phase 1 consists of a 10 Hz photocathode gun, a 2 m long S-band travelling wave linac, a spectrometer line, and associated optics and diagnostics. A detailed study into the beam dynamics of the lattice is presented, with a focus towards the effects of space charge and coherent synchrotron radiation on the electron bunch. Simulations disagreed with predictions from a one-dimensional model of coherent radiation, and this disagreement is believed to be due to a violation of the Derbenev criterion.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB059

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)