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hepunx.rl.ac.ukuknf2007-01-10signedrotator.ppt

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									Lower-Frequency RF Phase
Rotation Techniques for Both
        Muon Signs
                Stephen Brooks, RAL
                     s.j.brooks@rl.ac.uk
   Matthew McCullough, University College, Oxford
              matthew.mccullough@univ.ox.ac.uk
Low-Frequency Phase Rotation
• The UKNF phase rotator evolved from the
  CERN design
  – DE reduction occurs in a single RF bucket:




• Rees design uses 31.4MHz RF to achieve
  180±23MeV intended for a cooling ring
              Stephen Brooks, Matthew McCullough
               UKNF meeting, RAL, January 2007
     Problem with Two Signs
• Negative muons are rotated backwards




            Stephen Brooks, Matthew McCullough
             UKNF meeting, RAL, January 2007
Stephen Brooks, Matthew McCullough
 UKNF meeting, RAL, January 2007
Solution (idea) for Two Signs


I. Mixed-sign
                          II. Separate signs           III. Drift further to
drifted bunch from
                          with on-peak RF              get separation in time
decay channel




 IV. Put bunches on opposite sides of two adjacent wave troughs, to get the
 reverse sign separation and remaining phase rotation simultaneously
                      Stephen Brooks, Matthew McCullough
                       UKNF meeting, RAL, January 2007
   Does Dual-Sign Idea Work?
• Initial concept worked moderately well
• Some optimisation gave a solution for
  31.4MHz




              Stephen Brooks, Matthew McCullough
               UKNF meeting, RAL, January 2007
Stephen Brooks, Matthew McCullough
 UKNF meeting, RAL, January 2007
      Multi-Harmonic System
• Idea: allowing variation of RF frequencies
  in the optimisation could produce higher
  yields by better shaped rotation
• Allowed harmonics h=n/6 from 1/6 to 4
  times the 31.4MHz fundamental
  – Re-synchronisation every 6 periods (191ns)
• My optimisation produced one solution
• Summer student produced several others!
              Stephen Brooks, Matthew McCullough
               UKNF meeting, RAL, January 2007
Stephen Brooks, Matthew McCullough
 UKNF meeting, RAL, January 2007
Stephen Brooks, Matthew McCullough
 UKNF meeting, RAL, January 2007
Comparison of Yields
        70



        60

                                              (27.9,58.7)%
        50                                    Arithmetic mean = 43.3%

        40
                                                                 Original
% mu-




                                                                 Mine
                                                                 Matthew's
        30



        20



        10



         0
             0   10       20    30           40   50   60   70
                                     % mu+



                      Stephen Brooks, Matthew McCullough
                       UKNF meeting, RAL, January 2007
                    Other Parameters
Design              % Yield        # Cells            MV sum f / MHz
Original (single-
sign)               23.5           30                 67.5      31.4
31.4MHz dual-
sign                27.7           131                257.5     31.4
Multiharmonic
dual-sign           37.8           96                 184.4     20-126
Matthew: “New
Phase Rotation”     43.3           140                253.0     20-36
“Fifty Three”
                    42.1           115                201.3     20-43
“Twofreq”
                    34.8           98                 220.5     20.9, x2
“Optimise”
                    37.2           140                238.4     22-39
                           Stephen Brooks, Matthew McCullough
                            UKNF meeting, RAL, January 2007
               Conclusion
• The dual-sign problem with lower
  frequency (few-bucket) phase rotation
  schemes has been addressed
• Bunch train is 50-100ns instead of ~300ns
  as with 200MHz/Neuffer rotation
• Yields compare favourably
  – 43.3% into ±23MeV hard limit (48% into 28)
  – c.f. 57% into 28MeV 1-sigma ( 39% into 28)

              Stephen Brooks, Matthew McCullough
               UKNF meeting, RAL, January 2007

								
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