Author: Letchford, A.P.
Paper Title Page
WEPAL072 A Novel Longitudinal Laserwire to Non-Invasively Measure 6-Dimensional Bunch Parameters at High Current Hydrogen Ion Accelerators 2349
 
  • S.M. Gibson, A. Bosco
    Royal Holloway, University of London, Surrey, United Kingdom
  • S.E. Alden, A. Bosco, S.M. Gibson
    JAI, Egham, Surrey, United Kingdom
  • A.P. Letchford
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • J.K. Pozimski
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  • J.K. Pozimski
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
  
  Funding: We acknowledge funding by the STFC Grant ST/P003028/1 and the John Adams Institute at Royal Holloway, University of London.
Optical methods for non-invasive beam diagnostics of high current H− ion accelerators have been developed in recent years*, **. Such laserwires typically measure a 1D beam profile and/or 2D transverse emittance from the products of photo-detached ions as a laser beam is scanned across the H− beam. For laser pulse durations (~80ns) longer than the RF period (~3ns), the detector integrates many complete bunches, enabling only transverse beam monitoring. This paper presents a new technique to capture a series of time resolved transverse emittance measurements along the bunch train. A fast (~10ps) pulsed laser photo-detaches ions within each bunch and is synchronized to sample consecutive bunches at certain longitudinal positions along each bunch. A fast detector records the spatial distribution and time-of-flight of the neutralized H0, thus both the transverse and longitudinal emittance are reconstructed. We present simulations of a time varying pulsed laser field interacting within an H− bunch, and estimate the yield, spatial and time distributions of H0 arriving at the detector. We summarise the design of a recently funded longitudinal laserwire being installed in FETS at RAL, UK.
* NIM-A, 830, p526-531, T. Hofmann et al
** T. Hofmann et al, 'Commissioning of the Operational Laser Emittance Monitors for LINAC4 at CERN' IPAC18. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL072  
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THPML059 Re-Commissioning the Front End Test Stand Negative Hydrogen Ion Source, Beam Transport and Interlocks 4769
 
  • S.R. Lawrie, R.E. Abel, M. Dudman, D.C. Faircloth, A.P. Letchford, J.H. Macgregor, M. Perkins, T. M. Sarmento, R.C. Searle, M. Whitehead, T. Wood
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  The front end test stand (FETS) is a demonstrator for a future high intensity, high duty factor negative hydrogen (H') ion injector. With the radio-frequency quadrupole (RFQ) nearing installation, the ion source has been re-commissioned in preparation for long-term operation. The 3 MeV beam exceeds the radio-activation energy of common engineering materials, so radiation shielding has been erected. A new interlocking scheme has been signed-off which integrates the existing ion source high voltage area with the new shielding access points, to ensure that the machine can operate safely during beam production. The existing vacuum arrangement has been extended to in-clude the RFQ and medium energy beam transport (MEBT) line. A new programmable logic controller (PLC) has been built to operate the entire vacuum chain. The ion source high voltage equipment has been upgraded to minimise both spark rate and intensity. A collimating aperture and Faraday cup have been installed after the low energy beam transport (LEBT) section to ensure the beam is well aligned for injection into the RFQ. Re-commissioning the ion source has given a rugged shakedown of all these new systems before beam is required for the RFQ.
*scott.lawrie@stfc.ac.uk 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML059  
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