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Lawrie SR, Faircloth DC, Smith JD, Sarmento TM, Whitehead MO, Wood T, Perkins M, Macgregor J, Abel R. Recent H - diagnostics, plasma simulations, and 2X scaled Penning ion source developments at the Rutherford Appleton Laboratory. Rev Sci Instrum 2018; 89:052101. [PMID: 29864892 DOI: 10.1063/1.5011714] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A vessel for extraction and source plasma analyses is being used for Penning H- ion source development at the Rutherford Appleton Laboratory. A new set of optical elements including an einzel lens has been installed, which transports over 80 mA of H- beam successfully. Simultaneously, a 2X scaled Penning source has been developed to reduce cathode power density. The 2X source is now delivering a 65 mA H- ion beam at 10% duty factor, meeting its design criteria. The long-term viability of the einzel lens and 2X source is now being evaluated, so new diagnostic devices have been installed. A pair of electrostatic deflector plates is used to correct beam misalignment and perform fast chopping, with a voltage rise time of 24 ns. A suite of four quartz crystal microbalances has shown that the cesium flux in the vacuum vessel is only increased by a factor of two, despite the absence of a dedicated cold trap. Finally, an infrared camera has demonstrated good agreement with thermal simulations but has indicated unexpected heating due to beam loss on the downstream electrode. These types of diagnostics are suitable for monitoring all operational ion sources. In addition to experimental campaigns and new diagnostic tools, the high-performance VSim and COMSOL software packages are being used for plasma simulations of two novel ion thrusters for space propulsion applications. In parallel, a VSim framework has been established to include arbitrary temperature and cesium fields to allow the modeling of surface physics in H- ion sources.
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Affiliation(s)
- S R Lawrie
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Oxfordshire, United Kingdom
| | - D C Faircloth
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Oxfordshire, United Kingdom
| | - J D Smith
- Tech-X UK Ltd., The Innovation Centre, Sci-Tech Daresbury, Cheshire, United Kingdom
| | - T M Sarmento
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Oxfordshire, United Kingdom
| | - M O Whitehead
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Oxfordshire, United Kingdom
| | - T Wood
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Oxfordshire, United Kingdom
| | - M Perkins
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Oxfordshire, United Kingdom
| | - J Macgregor
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Oxfordshire, United Kingdom
| | - R Abel
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Oxfordshire, United Kingdom
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Lawrie SR, Faircloth DC, Letchford AP, Whitehead MO, Wood T. Detailed beam and plasma measurements on the vessel for extraction and source plasma analyses (VESPA) Penning H⁻ ion source. Rev Sci Instrum 2016; 87:02B122. [PMID: 26932004 DOI: 10.1063/1.4934580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A vessel for extraction and source plasma analyses (VESPA) is operational at the Rutherford Appleton Laboratory (RAL). This project supports and guides the overall ion source R&D effort for the ISIS spallation neutron and muon facility at RAL. The VESPA produces 100 mA of pulsed H(-) beam, but perveance scans indicate that the source is production-limited at extraction voltages above 12 kV unless the arc current is increased. A high resolution optical monochromator is used to measure plasma properties using argon as a diagnostic gas. The atomic hydrogen temperature increases linearly with arc current, up to 2.8 eV for 50 A; whereas the electron temperature has a slight linear decrease toward 2.2 eV. The gas density is 10(21) m(-3), whilst the electron density is two orders of magnitude lower. Densities follow square root relationships with arc current, with gas density decreasing whilst electron (and hence ion) density increases. Stopping and range of ions in matter calculations prove that operating a high current arc with an argon admixture is extremely difficult because cathode-coated cesium is heavily sputtered by argon.
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Affiliation(s)
- S R Lawrie
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Harwell, Oxford, United Kingdom
| | - D C Faircloth
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Harwell, Oxford, United Kingdom
| | - A P Letchford
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Harwell, Oxford, United Kingdom
| | - M O Whitehead
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Harwell, Oxford, United Kingdom
| | - T Wood
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Harwell, Oxford, United Kingdom
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Wood T, Faircloth DC, Lawrie SR, Letchford AP, Whitehead MO, Pike T, Perkins M. The ISIS pre-injector reconfiguration. Rev Sci Instrum 2016; 87:02B121. [PMID: 26932003 DOI: 10.1063/1.4934658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
With the introduction of a new "low energy beams" group at ISIS, the decision was taken to expand the ion source area. This paper will explain what actions were taken, how this has improved the present working environment and how the space will be used to accommodate a medium energy beam transport (MEBT) section after the existing radio-frequency quadrupole. The MEBT will incorporate three 202.5 MHz re-bunching cavities and will achieve a transmission of 96% with minimal emittance growth.
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Affiliation(s)
- T Wood
- ISIS Pulsed Spallation Neutron and Muon Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Oxfordshire, United Kingdom
| | - D C Faircloth
- ISIS Pulsed Spallation Neutron and Muon Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Oxfordshire, United Kingdom
| | - S R Lawrie
- ISIS Pulsed Spallation Neutron and Muon Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Oxfordshire, United Kingdom
| | - A P Letchford
- ISIS Pulsed Spallation Neutron and Muon Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Oxfordshire, United Kingdom
| | - M O Whitehead
- ISIS Pulsed Spallation Neutron and Muon Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Oxfordshire, United Kingdom
| | - T Pike
- ISIS Pulsed Spallation Neutron and Muon Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Oxfordshire, United Kingdom
| | - M Perkins
- ISIS Pulsed Spallation Neutron and Muon Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Oxfordshire, United Kingdom
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Lawrie SR, Faircloth DC, Letchford AP, Perkins M, Whitehead MO, Wood T, Gabor C, Back J. Development of the front end test stand and vessel for extraction and source plasma analyses negative hydrogen ion sources at the Rutherford Appleton Laboratory. Rev Sci Instrum 2014; 85:02B127. [PMID: 24593567 DOI: 10.1063/1.4826109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The ISIS pulsed spallation neutron and muon facility at the Rutherford Appleton Laboratory (RAL) in the UK uses a Penning surface plasma negative hydrogen ion source. Upgrade options for the ISIS accelerator system demand a higher current, lower emittance beam with longer pulse lengths from the injector. The Front End Test Stand is being constructed at RAL to meet the upgrade requirements using a modified ISIS ion source. A new 10% duty cycle 25 kV pulsed extraction power supply has been commissioned and the first meter of 3 MeV radio frequency quadrupole has been delivered. Simultaneously, a Vessel for Extraction and Source Plasma Analyses is under construction in a new laboratory at RAL. The detailed measurements of the plasma and extracted beam characteristics will allow a radical overhaul of the transport optics, potentially yielding a simpler source configuration with greater output and lifetime.
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Affiliation(s)
- S R Lawrie
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Harwell Oxford, Harwell, United Kingdom
| | - D C Faircloth
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Harwell Oxford, Harwell, United Kingdom
| | - A P Letchford
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Harwell Oxford, Harwell, United Kingdom
| | - M Perkins
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Harwell Oxford, Harwell, United Kingdom
| | - M O Whitehead
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Harwell Oxford, Harwell, United Kingdom
| | - T Wood
- STFC ISIS Pulsed Spallation Neutron and Muon Facility, Rutherford Appleton Laboratory, Harwell Oxford, Harwell, United Kingdom
| | - C Gabor
- ASTeC Intense Beams Group, Rutherford Appleton Laboratory, Harwell Oxford, Harwell, United Kingdom
| | - J Back
- High Energy Physics Department, University of Warwick, Coventry, United Kingdom
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Gabor C, Back JJ, Faircloth DC, Lawrie SR, Letchford AP. Matching an H(-) beam into a radio frequency quadrupole at Rutherford Appleton Laboratory. Rev Sci Instrum 2014; 85:02A745. [PMID: 24593479 DOI: 10.1063/1.4862213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A major component of work being carried out to upgrade the ISIS spallation neutron source at Rutherford Appleton Laboratory (RAL) is the Front End Test Stand (FETS). FETS is aimed at improving the luminosity of the linac, and consists of a Penning ion source, Low Energy Beam Transport (LEBT), Radio Frequency Quadrupole (RFQ), and Medium Energy Beam Transport (MEBT). It may serve as a first part of the accelerator chain providing a 60 mA, 3 MeV H(-) beam up to a 10% duty cycle. The current output of the source and the transmission of the LEBT are reasonable, but there are issues with the alignment to provide a centred beam matched into the acceptance of the RFQ. Improvements have been made to the post acceleration to address this problem. Measurements with a collimated beam have been performed to understand the behaviour of the solenoids and steerer magnets. Comparing these results with simulations proved that, besides possible mechanical imperfections of the ion source and post acceleration assembly, agreement can only be achieved if the magnetic fields are distorted.
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Affiliation(s)
- C Gabor
- STFC, Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, United Kingdom
| | - J J Back
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - D C Faircloth
- STFC, Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, United Kingdom
| | - S R Lawrie
- STFC, Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, United Kingdom
| | - A P Letchford
- STFC, Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, United Kingdom
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Lawrie SR, Faircloth DC, Philippe K. Initial study of the optical spectrum of the ISIS H- ion source plasma. Rev Sci Instrum 2012; 83:02A704. [PMID: 22380213 DOI: 10.1063/1.3662959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The front end test stand is being constructed at the Rutherford Appleton Laboratory, with the aim of producing a 60 mA, 2 ms, 50 Hz, perfectly chopped H(-) ion beam. To meet the beam requirements, a more detailed understanding of the ion source plasma is required. To this end, an initial study is made of the optical spectrum of the plasma using a digital spectrometer. The atomic and molecular emission lines of hydrogen and caesium are clearly distinguished and a quantitative comparison is made when the ion source is run in different conditions. The electron temperature is 0.6 eV and measured line widths vary by up to 75%.
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Affiliation(s)
- S R Lawrie
- ISIS Pulsed Neutron and Muon Source, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, United Kingdom.
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Gabor C, Back JJ, Faircloth DC, Izaola Z, Lawrie SR, Letchford AP. H- beam transport experiments in a solenoid low energy beam transport. Rev Sci Instrum 2012; 83:02B719. [PMID: 22380324 DOI: 10.1063/1.3678656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The Front End Test Stand (FETS) is located at Rutherford Appleton Laboratory and aims for a high current, fast chopped 3 MeV H(-) ion beam suitable for future high power proton accelerators like ISIS upgrade. The main components of the front end are the Penning ion source, a low energy beam transport line, an radio-frequency quadrupole (RFQ) and a medium energy beam transport (MEBT) providing also a chopper section and rebuncher. FETS is in the stage of commissioning its low energy beam transport (LEBT) line consisting of three solenoids. The LEBT has to transport an H(-) high current beam (up to 60 mA) at 65 keV. This is the injection energy of the beam into the RFQ. The main diagnostics are slit-slit emittance scanners for each transversal plane. For optimizing the matching to the RFQ, experiments have been performed with a variety of solenoid settings to better understand the actual beam transport. Occasionally, source parameters such as extractor slit width and beam energy were varied as well. The paper also discusses simulations based on these measurements.
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Affiliation(s)
- C Gabor
- ASTeC Intense Beams Group, Rutherford Appleton Laboratory, Chilton, Didcot-Oxfordshire OX11 0QX, United Kingdom.
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Gabor C, Faircloth DC, Lee DA, Lawrie SR, Letchford AP, Pozimski JK. Diagnostic experiments at a 3 MeV test stand at Rutherford Appleton Laboratory (United Kingdom). Rev Sci Instrum 2010; 81:02B718. [PMID: 20192458 DOI: 10.1063/1.3290858] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A front end is currently under construction consisting of a H(-) Penning ion source (65 keV, 60 mA), low energy beam transport (LEBT), and radio frequency quadrupole (3 MeV output energy) with a medium energy beam transport suitable for high power proton applications. Diagnostics can be divided either in destructive techniques such as beam profile monitor, pepperpot, slit-slit emittance scanner (preferably used during commissioning) or nondestructive, permanently installed devices such as photodetachment-based techniques. Another way to determine beam distributions is a scintillator with charge-coupled device camera. First experiments have been performed to control the beam injection into the LEBT. The influence of beam parameters such as particle energy and space-charge compensation on the two-dimensional distribution and profiles will be presented.
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Affiliation(s)
- C Gabor
- ASTeC Intense Beams Group, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, United Kingdom.
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Faircloth DC, Lawrie S, Letchford AP, Gabor C, Wise P, Whitehead M, Wood T, Westall M, Findlay D, Perkins M, Savage PJ, Lee DA, Pozimski JK. The front end test stand high performance H- ion source at Rutherford Appleton Laboratory. Rev Sci Instrum 2010; 81:02A721. [PMID: 20192390 DOI: 10.1063/1.3271169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The aim of the front end test stand (FETS) project is to demonstrate that chopped low energy beams of high quality can be produced. FETS consists of a 60 mA Penning Surface Plasma Ion Source, a three solenoid low energy beam transport, a 3 MeV radio frequency quadrupole, a chopper, and a comprehensive suite of diagnostics. This paper details the design and initial performance of the ion source and the laser profile measurement system. Beam current, profile, and emittance measurements are shown for different operating conditions.
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Affiliation(s)
- D C Faircloth
- STFC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX14 0QX, United Kingdom.
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Lawrie SR, Faircloth DC, Letchford AP, Gabor C, Pozimski JK. Plasma meniscus and extraction electrode studies of the ISIS H- ion source. Rev Sci Instrum 2010; 81:02A707. [PMID: 20192377 DOI: 10.1063/1.3277139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In order to reduce the emittance and increase the transported beam current from the ISIS Penning-type H(-) ion source, improvements to the extraction system are required. This ion source is currently being commissioned on the front end test stand at the Rutherford Appleton Laboratory, which demands higher extraction energies, higher beam currents, and smaller emittances. To facilitate this, the present geometry requires optimization. This paper details the experimental and simulation studies performed of the plasma meniscus and the possible electrode geometry modifications needed to extract the highest quality beam.
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Affiliation(s)
- S R Lawrie
- ISIS Pulsed Spallation Neutron Source, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, United Kingdom.
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Faircloth DC, Letchford AP, Gabor C, Whitehead MO, Wood T, Jolly S, Pozimski J, Savage P, Woods M. Understanding extraction and beam transport in the ISIS H(-) Penning surface plasma ion source. Rev Sci Instrum 2008; 79:02B717. [PMID: 18315208 DOI: 10.1063/1.2821506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The ISIS H(-) Penning surface plasma source has been developed to produce beam currents up to 70 mA and pulse lengths up to 1.5 ms at 50 Hz. This paper details the investigation into beam extraction and beam transport in an attempt to understand the beam emittance and to try to improve the emittance. A scintillator profile measurement technique has been developed to assess the performance of different plasma electrode apertures, extraction electrode geometries, and postextraction acceleration configurations. This work shows that the present extraction, beam transport, and postacceleration system are suboptimal and further work is required to improve it.
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