IPAC2012 - List of Authors (Letchford, A.P.)

Paper	Title	Page
MOPPD037	Investigation of Space Charge Compensation at FETS	445
	J.K. Pozimski, S.M.H. Alsari, P. Savage Imperial College of Science and Technology, Department of Physics, London, United Kingdom D.C. Faircloth, A.P. Letchford STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	In order to contribute to the development of high power proton accelerators in the MW range, to prepare the way for an ISIS upgrade and to contribute to the UK design effort on neutrino factories, a front end test stand (FETS) is being constructed at the Rutherford Appleton Laboratory (RAL) in the UK. The aim of the FETS is to demonstrate the production of a 60 mA, 2 ms, 50 pps chopped beam at 3 MeV with sufficient beam quality. The ion source and LEBT are operational with the RFQ under manufacture. In the LEBT a high degree of space charge compensation (~90%) and a rise time of space charge compensation around ~ 50 μs could be concluded indirectly from measurements . As a more detailed knowledge is of interest also for other projects like ESS the FETS LEBT was updated to perform a detailed experimental analysis of space charge compensation. In this paper the results of the experimental work will be presented together with discussion of the findings in respect to beam transport.

MOPPR055	A Two-dimensional Wire Scanner for a Low Energy Ion Beam	909
	C. Gabor STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom G.E. Boorman Royal Holloway, University of London, Surrey, United Kingdom A.P. Letchford STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL) is intended to demonstrate the early stages of acceleration for future high power proton applications. So far, the H⁻ ion source and the low energy beam transport (LEBT) are operational. The commissioning of the LEBT is carried out with a multipurpose diagnostics vessel. On the other hand, the present status of the LEBT does not provide any permanent installed beam diagnostics beyond current measurement. Possible diagnostics need to be compact and rigid in a way that it can survive an area with potentially high beam losses and not suffering to much of beam noise. Furthermore, minimal invasive diagnostics is preferred. It is intended to present first results of a wire scanner where the geometry has been changed in a way that the two dimensional xy-space is accessible.

MOPPR056	Experimental and Theoretical Studies of a Low Energy H⁻ beam	912
	C. Gabor STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom G.E. Boorman Royal Holloway, University of London, Surrey, United Kingdom A.P. Letchford STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL) is intended to demonstrate the early stages of acceleration (0-3 MeV) and beam chopping required for high power proton accelerators. At the moment, the RFQ is under construction and there is a need to understand the matching of the Low Energy Beam Transport (LEBT) into the RFQ as conclusive as possible. The parameter of interest may include solenoid settings, steering effects but also the influence of the post acceleration of the ion source and potential effects of space charge compensation. Two emittance scanner are installed and can be combined with scintillator acting as a beam profile monitor and auxiliaries like current measurement.

THPPP051	Status of the RAL Front End Test Stand	3856
	A.P. Letchford, M.A. Clarke-Gayther, D.C. Faircloth, S.R. Lawrie STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom S.M.H. Alsari, M. Aslaninejad, A. Kurup, P. Savage Imperial College of Science and Technology, Department of Physics, London, United Kingdom J.J. Back University of Warwick, Coventry, United Kingdom G.E. Boorman, A. Bosco Royal Holloway, University of London, Surrey, United Kingdom C. Gabor, D.C. Plostinar STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom A. Garbayo AVS, Eibar, Gipuzkoa, Spain S. Jolly UCL, London, United Kingdom J.K. Pozimski STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
	The Front End Test Stand (FETS) under construction at RAL is a demonstrator for front end systems of a future high power proton linac. Possible applications include a linac upgrade for the ISIS spallation neutron source, new future neutron sources, accelerator driven sub-critical systems, a neutrino factory etc. Designed to deliver a 60mA H-minus beam at 3MeV with a 10% duty factor, FETS consists of a high brightness ion source, magnetic low energy beam transport (LEBT), 4-vane 324MHz radio frequency quadrupole, medium energy beam transport (MEBT) containing a high speed beam chopper plus comprehensive diagnostics. This paper describes the current status of the project and future plans.

THPPP052	Modelling the ISIS 70 MeV Linac	3859
	D.C. Plostinar, C.R. Prior, G.H. Rees STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom A.P. Letchford STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom A.W. Mitchell University of Warwick, Coventry, United Kingdom
	The ISIS linac consists of four DTL tanks that accelerate a 50 pps, 20 mA H⁻ beam up to 70 MeV before injecting it into an 800 MeV synchrotron. Over the last decades, the linac has proved to be a stable and reliable injector for ISIS, which is a significant achievement considering that two of the tanks are nearly 60 years old. At the time the machine was designed, the limited computing power available and the absence of modern modeling codes, made the creation of a complex simulation model almost impossible. However, over the last few years, computer tools have became an integral part of any accelerator design, so in this paper we present a beam dynamics model of the ISIS linac. A comparison between the simulation results and machine operation data will be discussed, as well as possible linac tuning scenarios and recommended upgrades based on the new model.

THPPP053	The Manufacture and Assembly of the FETS RFQ	3862
	P. Savage, J.K. Pozimski Imperial College of Science and Technology, Department of Physics, London, United Kingdom A. Garbayo AVS, Eibar, Gipuzkoa, Spain A.P. Letchford STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom D.S. Wilsher STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
	The Rutherford Appleton Laboratory (RAL) Front End Test Stand (FETS) uses a 324 MHz 4-vane RFQ to accelerate H⁻ ions from 65keV to 3MeV. The RFQ is a copper structure that has been designed as 4 nominally one metre long assemblies. Each assembly consists of 2 major vanes and 2 minor vanes that are bolted together and sealed using an O ring. The mechanical design for the FETS RFQ is complete and the manufacture is underway. In order to achieve the designed physics performance the vanes must be machined and assembled to high degree of accuracy. This requirement has demanded a tight synergy between the design, manufacture and metrology services. Together they have developed detailed procedures for the manufacturing, inspection, alignment and assembly phases. The key points of these procedures will be detailed in this paper.

THEPPB001	Design and Fabrication of The ESS-Bilbao RFQ Prototype Models	3228
	I. Bustinduy, F.J. Bermejo, J. Feuchtwanger, N. Garmendia, A. Ghiglino, O. González, P.J. González, I. Madariaga, J.L. Muñoz, I. Rueda, F. Sordo Balbin, A. Vélez, D. de Cos ESS Bilbao, Bilbao, Spain V. Etxebarria, J. Portilla University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain A. Garbayo AVS, Eibar, Gipuzkoa, Spain S. Jolly UCL, London, United Kingdom S.R. Lawrie, A.P. Letchford STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom J.K. Pozimski, P. Savage Imperial College of Science and Technology, Department of Physics, London, United Kingdom
	As part of the development of the ESS-Bilbao Accelerator in Spain, two different sets of radio frequency quadrupole (RFQ) models have been developed. On one hand, a set of four oxygen free high conductivity copper weld test models has been designed and manufactured, in order to test different welding methods as well as other mechanical aspects involved in the fabrication of the RFQ. On the other hand, a 352.2 MHz four vane RFQ cold model, with a length of 1 meter, has been designed and built in Aluminum. It serves as a good test bench to investigate the validity of different finite element analysis (FEA) software packages. This is a critical part, since the design of the final RFQ will be based on such simulations. The cold model also includes 16 slug tuners and 8 couplers/pick-up ports, which will allow to use the bead-pull perturbation method, by measuring the electric ﬁeld profile, Q-value and resonant modes. In order to investigate fabrication tolerances, the cold model also comprises a longitudinal test modulation in the vanes, which is similar to the one designed for the final RFQ.

Paper

Title

Page

Investigation of Space Charge Compensation at FETS

445

J.K. Pozimski, S.M.H. Alsari, P. Savage
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
D.C. Faircloth, A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

In order to contribute to the development of high power proton accelerators in the MW range, to prepare the way for an ISIS upgrade and to contribute to the UK design effort on neutrino factories, a front end test stand (FETS) is being constructed at the Rutherford Appleton Laboratory (RAL) in the UK. The aim of the FETS is to demonstrate the production of a 60 mA, 2 ms, 50 pps chopped beam at 3 MeV with sufficient beam quality. The ion source and LEBT are operational with the RFQ under manufacture. In the LEBT a high degree of space charge compensation (~90%) and a rise time of space charge compensation around ~ 50 μs could be concluded indirectly from measurements . As a more detailed knowledge is of interest also for other projects like ESS the FETS LEBT was updated to perform a detailed experimental analysis of space charge compensation. In this paper the results of the experimental work will be presented together with discussion of the findings in respect to beam transport.

MOPPR055

A Two-dimensional Wire Scanner for a Low Energy Ion Beam

909

C. Gabor
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
G.E. Boorman
Royal Holloway, University of London, Surrey, United Kingdom
A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL) is intended to demonstrate the early stages of acceleration for future high power proton applications. So far, the H⁻ ion source and the low energy beam transport (LEBT) are operational. The commissioning of the LEBT is carried out with a multipurpose diagnostics vessel. On the other hand, the present status of the LEBT does not provide any permanent installed beam diagnostics beyond current measurement. Possible diagnostics need to be compact and rigid in a way that it can survive an area with potentially high beam losses and not suffering to much of beam noise. Furthermore, minimal invasive diagnostics is preferred. It is intended to present first results of a wire scanner where the geometry has been changed in a way that the two dimensional xy-space is accessible.

MOPPR056

Experimental and Theoretical Studies of a Low Energy H⁻ beam

912

C. Gabor
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
G.E. Boorman
Royal Holloway, University of London, Surrey, United Kingdom
A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL) is intended to demonstrate the early stages of acceleration (0-3 MeV) and beam chopping required for high power proton accelerators. At the moment, the RFQ is under construction and there is a need to understand the matching of the Low Energy Beam Transport (LEBT) into the RFQ as conclusive as possible. The parameter of interest may include solenoid settings, steering effects but also the influence of the post acceleration of the ion source and potential effects of space charge compensation. Two emittance scanner are installed and can be combined with scintillator acting as a beam profile monitor and auxiliaries like current measurement.

THPPP051

Status of the RAL Front End Test Stand

3856

A.P. Letchford, M.A. Clarke-Gayther, D.C. Faircloth, S.R. Lawrie
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
S.M.H. Alsari, M. Aslaninejad, A. Kurup, P. Savage
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
J.J. Back
University of Warwick, Coventry, United Kingdom
G.E. Boorman, A. Bosco
Royal Holloway, University of London, Surrey, United Kingdom
C. Gabor, D.C. Plostinar
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
A. Garbayo
AVS, Eibar, Gipuzkoa, Spain
S. Jolly
UCL, London, United Kingdom
J.K. Pozimski
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom

The Front End Test Stand (FETS) under construction at RAL is a demonstrator for front end systems of a future high power proton linac. Possible applications include a linac upgrade for the ISIS spallation neutron source, new future neutron sources, accelerator driven sub-critical systems, a neutrino factory etc. Designed to deliver a 60mA H-minus beam at 3MeV with a 10% duty factor, FETS consists of a high brightness ion source, magnetic low energy beam transport (LEBT), 4-vane 324MHz radio frequency quadrupole, medium energy beam transport (MEBT) containing a high speed beam chopper plus comprehensive diagnostics. This paper describes the current status of the project and future plans.

THPPP052

Modelling the ISIS 70 MeV Linac

3859

D.C. Plostinar, C.R. Prior, G.H. Rees
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
A.W. Mitchell
University of Warwick, Coventry, United Kingdom

The ISIS linac consists of four DTL tanks that accelerate a 50 pps, 20 mA H⁻ beam up to 70 MeV before injecting it into an 800 MeV synchrotron. Over the last decades, the linac has proved to be a stable and reliable injector for ISIS, which is a significant achievement considering that two of the tanks are nearly 60 years old. At the time the machine was designed, the limited computing power available and the absence of modern modeling codes, made the creation of a complex simulation model almost impossible. However, over the last few years, computer tools have became an integral part of any accelerator design, so in this paper we present a beam dynamics model of the ISIS linac. A comparison between the simulation results and machine operation data will be discussed, as well as possible linac tuning scenarios and recommended upgrades based on the new model.

THPPP053

The Manufacture and Assembly of the FETS RFQ

3862

P. Savage, J.K. Pozimski
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
A. Garbayo
AVS, Eibar, Gipuzkoa, Spain
A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
D.S. Wilsher
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom

The Rutherford Appleton Laboratory (RAL) Front End Test Stand (FETS) uses a 324 MHz 4-vane RFQ to accelerate H⁻ ions from 65keV to 3MeV. The RFQ is a copper structure that has been designed as 4 nominally one metre long assemblies. Each assembly consists of 2 major vanes and 2 minor vanes that are bolted together and sealed using an O ring. The mechanical design for the FETS RFQ is complete and the manufacture is underway. In order to achieve the designed physics performance the vanes must be machined and assembled to high degree of accuracy. This requirement has demanded a tight synergy between the design, manufacture and metrology services. Together they have developed detailed procedures for the manufacturing, inspection, alignment and assembly phases. The key points of these procedures will be detailed in this paper.

THEPPB001

Design and Fabrication of The ESS-Bilbao RFQ Prototype Models

3228

I. Bustinduy, F.J. Bermejo, J. Feuchtwanger, N. Garmendia, A. Ghiglino, O. González, P.J. González, I. Madariaga, J.L. Muñoz, I. Rueda, F. Sordo Balbin, A. Vélez, D. de Cos
ESS Bilbao, Bilbao, Spain
V. Etxebarria, J. Portilla
University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
A. Garbayo
AVS, Eibar, Gipuzkoa, Spain
S. Jolly
UCL, London, United Kingdom
S.R. Lawrie, A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
J.K. Pozimski, P. Savage
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

As part of the development of the ESS-Bilbao Accelerator in Spain, two different sets of radio frequency quadrupole (RFQ) models have been developed. On one hand, a set of four oxygen free high conductivity copper weld test models has been designed and manufactured, in order to test different welding methods as well as other mechanical aspects involved in the fabrication of the RFQ. On the other hand, a 352.2 MHz four vane RFQ cold model, with a length of 1 meter, has been designed and built in Aluminum. It serves as a good test bench to investigate the validity of different finite element analysis (FEA) software packages. This is a critical part, since the design of the final RFQ will be based on such simulations. The cold model also includes 16 slug tuners and 8 couplers/pick-up ports, which will allow to use the bead-pull perturbation method, by measuring the electric ﬁeld profile, Q-value and resonant modes. In order to investigate fabrication tolerances, the cold model also comprises a longitudinal test modulation in the vanes, which is similar to the one designed for the final RFQ.