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Letchford, A.P.

Paper Title Page
TUPB22 Design Report of a Non-Destructive Emittance Instrument for RAL's Front End Test Stand FETS 213
 
  • C. Gabor
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon
  • A.P. Letchford
    STFC/RAL, Chilton, Didcot, Oxon
  • J.K. Pozimski
    Imperial College of Science and Technology, Department of Physics, London
 
 

The RAL front end FETS is currently under construction to demonstrate an H-ion beam with up to 18 kW at 3 MeV. Due to the beam power photo detachment techniques are the preferable choice for emittance instruments. Typically, measurements will be performed in just one transverse plane by using a magnet to separate ion beam from produced neutrals. Another general technique to work out a 2D emittance bases on several beam profiles applying an image reconstruction method called maximum entropy (MaxEnt). Combining both methods in one device has the significant advantage of reducing technical and physical problems which may occur by doubling magnet or laser beam path. Drawback of MaxEnt is the necessity of sufficient phase space advance to achieve reasonable results which can be either optimised by moving the particle detector or with additional focusing. The paper presents a conceptual design study discussing all possible constraints given by beam parameters and chopper/ MEBT. Simulations will help to estimate performance and errors.

 
WEOA03 Data Acquisition and Error Analysis for Pepperpot Emittance Measurements 421
 
  • S. Jolly
    Imperial College of Science and Technology, Department of Physics, London
  • D.C. Faircloth, S.R. Lawrie, A.P. Letchford
    STFC/RAL/ISIS, Chilton, Didcot, Oxon
  • C. Gabor
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon
  • O.K. Kester
    NSCL, East Lansing, Michigan
  • J. Pfister
    IAP, Frankfurt am Main
  • J.K. Pozimski
    STFC/RAL, Chilton, Didcot, Oxon
 
 

The pepperpot provides a unique and fast method of measuring emittance, providing four dimensional correlated beam measurements for both transverse planes. In order to make such a correlated measurement, the pepperpot must sample the beam at specific intervals. Such discontinuous data, and the unique characteristics of the pepperpot assembly, requires special attention be paid to both the data acquisition and the error analysis techniques. A first-principles derivation of the error contribution to the rms emittance is presented, leading to a general formula for emittance error calculation. Two distinct pepperpot systems, currently in use at GSI in Germany and RAL in the UK, are described. The data acquisition process for each system is detailed, covering the reconstruction of the beam profile and the transverse emittances. Error analysis for both systems is presented, using a number of methods to estimate the emittance and associated errors.

 

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