IPAC2018 - List of Authors (Hannah, A.N.)

Paper	Title	Page
THPAL092	Test Particle Monte Carlo Simulation of NEG Coated Narrow Tubular Samples	3862
	O. Seify, A.N. Hannah, O.B. Malyshev, Sirvinskaite, R. Sirvinskaite, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom Sirvinskaite, R. Sirvinskaite Loughborough University, Loughborough, Leicestershire, United Kingdom
	The pumping properties of the NEG coated vacuum chambers play an important role in the efficiency of vac-uum system of accelerators. The sticking probability of the NEG films is one the most important parameters to characterise the pumping properties of the NEG coated vacuum chambers. In order to investigate the NEG film sticking probability, Test Particle Monte-Carlo (TPMC) models were used. The models were based on the design of the installed experimental setup in ASTeC Vacuum Science group laboratory at Daresbury Laboratory (DL). The results of the simulations have been used for inter-preting the results of the measurements in the experi-mental setup.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL092
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAL095	Metal Photocathodes Preparation for Compact Linear Accelerator at Daresbury Laboratory	3865
	A.N. Hannah, J.A. Conlon, L.B. Jones, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom V. R. Dhanak The University of Liverpool, Liverpool, United Kingdom L.B. Jones, B.L. Militsyn Cockcroft Institute, Warrington, Cheshire, United Kingdom S. Lederer DESY Zeuthen, Zeuthen, Germany S. Lederer DESY, Hamburg, Germany
	The photoinjector of the CLARA FEL test facility Front End at Daresbury Laboratory is based on a S-band 10 Hz photocathode RF-gun operating with a copper photocath-ode which is driven by the third harmonic of a Ti:Sapphire laser (266 nm). The main aim of this study was to establish a procedure to prepare the Cu surface prior to installation so a Quantum Efficiency (QE) of 10^-5 or higher can be achieved at laser power density below the ablation threshold of copper. The best results have been obtained by ex-situ chemical cleaning. This removed the surface oxide layer whilst at the same time producing a surface buffer layer. This inhibited the regrowth of native oxide for up to a week when exposed to normal ambient atmospheric conditions. With either chemical cleaning or Ar plasma cleaning after heating the sample in-situ to 150 °C for 90 minutes or 250 °C for 40 hours, almost all of the surface oxide was removed. For these surfaces a QE of 4.10-5 or better was measured. Oxygen plasma cleaning at 100% and 20% power produced CuO layer with surface carbon contaminant to 3 atomic %, however in-situ thermal cycling resulted in at best a QE of 3·10-6.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL095
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAL098	Pumping Properties of Single Metal Zirconium Non-Evaporable Getter Coating	3869
	Sirvinskaite, R. Sirvinskaite, M.D. Cropper, M.D. Cropper Loughborough University, Leicestershre, United Kingdom A.N. Hannah, O.B. Malyshev, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom O.B. Malyshev, R. Valizadeh Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Non-evaporable getter (NEG) coating has been used for years in many particle accelerator facilities due to its evenly distributed pumping speed, low thermal outgassing, and low photon and electron stimulated desorption yields. We have previously demonstrated that quaternary Ti-Zr-Hf-V coating deposited from an alloy wire has the lowest desorption yields, the highest sticking probability and sorption capacity. In this work, we explore the single element targets which are widely available and can be produced in a form of a wire that is easy to apply for a uniform coating of various shapes of vacuum chamber. Single metal Zr coatings have been tested to find a more efficient and cheaper way of producing the NEG-coated vacuum chambers. Two samples coated with Zr of dense and columnar structure were analysed and results of the pumping properties are reported. The results show that pure Zr coating could be an economic solution, despite not being as effective as can be achieved with quaternary NEG film. It shows that columnar Zr coating can be activated and reaches full pumping capacity at 160°C. This is close to the activation temperature of Ti-Zr-Hf-V and lower than that for the widely used ternary Ti-Zr-V alloy.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL098
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Test Particle Monte Carlo Simulation of NEG Coated Narrow Tubular Samples

3862

O. Seify, A.N. Hannah, O.B. Malyshev, Sirvinskaite, R. Sirvinskaite, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
Sirvinskaite, R. Sirvinskaite
Loughborough University, Loughborough, Leicestershire, United Kingdom

The pumping properties of the NEG coated vacuum chambers play an important role in the efficiency of vac-uum system of accelerators. The sticking probability of the NEG films is one the most important parameters to characterise the pumping properties of the NEG coated vacuum chambers. In order to investigate the NEG film sticking probability, Test Particle Monte-Carlo (TPMC) models were used. The models were based on the design of the installed experimental setup in ASTeC Vacuum Science group laboratory at Daresbury Laboratory (DL). The results of the simulations have been used for inter-preting the results of the measurements in the experi-mental setup.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL092

Export •

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

THPAL095

Metal Photocathodes Preparation for Compact Linear Accelerator at Daresbury Laboratory

3865

A.N. Hannah, J.A. Conlon, L.B. Jones, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
V. R. Dhanak
The University of Liverpool, Liverpool, United Kingdom
L.B. Jones, B.L. Militsyn
Cockcroft Institute, Warrington, Cheshire, United Kingdom
S. Lederer
DESY Zeuthen, Zeuthen, Germany
S. Lederer
DESY, Hamburg, Germany

The photoinjector of the CLARA FEL test facility Front End at Daresbury Laboratory is based on a S-band 10 Hz photocathode RF-gun operating with a copper photocath-ode which is driven by the third harmonic of a Ti:Sapphire laser (266 nm). The main aim of this study was to establish a procedure to prepare the Cu surface prior to installation so a Quantum Efficiency (QE) of 10^-5 or higher can be achieved at laser power density below the ablation threshold of copper. The best results have been obtained by ex-situ chemical cleaning. This removed the surface oxide layer whilst at the same time producing a surface buffer layer. This inhibited the regrowth of native oxide for up to a week when exposed to normal ambient atmospheric conditions. With either chemical cleaning or Ar plasma cleaning after heating the sample in-situ to 150 °C for 90 minutes or 250 °C for 40 hours, almost all of the surface oxide was removed. For these surfaces a QE of 4.10-5 or better was measured. Oxygen plasma cleaning at 100% and 20% power produced CuO layer with surface carbon contaminant to 3 atomic %, however in-situ thermal cycling resulted in at best a QE of 3·10-6.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL095

Export •

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

THPAL098

Pumping Properties of Single Metal Zirconium Non-Evaporable Getter Coating

3869

Sirvinskaite, R. Sirvinskaite, M.D. Cropper, M.D. Cropper
Loughborough University, Leicestershre, United Kingdom
A.N. Hannah, O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
O.B. Malyshev, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Non-evaporable getter (NEG) coating has been used for years in many particle accelerator facilities due to its evenly distributed pumping speed, low thermal outgassing, and low photon and electron stimulated desorption yields. We have previously demonstrated that quaternary Ti-Zr-Hf-V coating deposited from an alloy wire has the lowest desorption yields, the highest sticking probability and sorption capacity. In this work, we explore the single element targets which are widely available and can be produced in a form of a wire that is easy to apply for a uniform coating of various shapes of vacuum chamber. Single metal Zr coatings have been tested to find a more efficient and cheaper way of producing the NEG-coated vacuum chambers. Two samples coated with Zr of dense and columnar structure were analysed and results of the pumping properties are reported. The results show that pure Zr coating could be an economic solution, despite not being as effective as can be achieved with quaternary NEG film. It shows that columnar Zr coating can be activated and reaches full pumping capacity at 160°C. This is close to the activation temperature of Ti-Zr-Hf-V and lower than that for the widely used ternary Ti-Zr-V alloy.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL098

Export •

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