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RFQ Tuning Method last results

RFQ Tuning Method last results. IPHI-SPL collaboration meeting - CERN 28 & 29 /04/2003. CEA/DSM/DAPNIA/SACM. V [kV]. 4. Closest dipole modes frequencies. 3. Dipole components presence within the accelerating mode. f + D - f Q = f Q - f - D.

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RFQ Tuning Method last results

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  1. RFQ Tuning Methodlast results IPHI-SPL collaboration meeting - CERN 28 & 29 /04/2003 CEA/DSM/DAPNIA/SACM

  2. V [kV] 4. Closest dipole modes frequencies 3. Dipole components presence within the accelerating mode f +D - fQ = fQ - f -D |uS(z)/uQ(z)|< 10-2 |uT(z)/uQ(z)|< 10-2 z [m] What do we electromagnetically tune ? 1. Resonance Frequency fQ : 352.21 MHz 2. Accelerating voltage profile : Vp(z) |(uQ(z)-Vp(z))/Vp(z)|< 10-2

  3. Mode S et T (ST) Mode Q distribution S Quadripole Mode S = [ -1/2, 0, 1/2, 0] Q = [ -1/2, 1/2, -1/2, 1/2] T = [ 0, -1/2, 0, 1/2]  S dipoleModes  focalisation  Kpq = 352,2 MHz …

  4. Central region End regions 1. Slug tuners 2. « dipole » rods 3. Plate thickness What do we mechanically tune ?

  5. Diagnosis Treatment 1. Model 2. Test bench 5. Mathematical formalism What is the ideal RFQ ? e.l.m. parameters of the real RFQ e.l.m. parameters  mechanical devices 1. Slug tuners Frequencies  2. Dipole rods Field distribution 3. End plates 3. Spectral analysis The tuning tools that we have developed 4. Cold-model  Defaults real RFQ / ideal RFQ  Fast tuning  High accuracy

  6. Coupled, inhomogeneous, 4-wire line equivalent circuit End regions Central region End regions Boundary conditions M = hermetian operator (tM=M) Eigen values (R+) = resonance frequencies fQi, fSj, fTk Our model & the associated spectral analysis d2U/dz2 – A U = - (/c)2 U Eigen functions (orthogonal basis) = { vQi(z), vSj(z), vTk(z) } voltage base functions Refer to : A. France, F. Simoens, “Theoretical Analysis of a Real-life RFQ Using a 4-Wire Line Model and the Spectral Theory of Differential Operators.”, EPAC2002 Conference (Paris), June 2002

  7. Measurements Model 3d simulations 2 L2 C1 3 L1 L3 C3 L4 C4 4 Comparison measurements / model / 3d simulations Refer to :F. Simoens, A. France, O. Delferrière, “An Equivalent 4-Wire Line Theoretical Model of Real RFQ based on the Spectral Differential Theory”, CEA-SACLAY, LINAC Conference (Gyungju, Korea), August 2002

  8. uS(z) [u.a.] fQ 0 350,62 MHz 1 352,18 MHz 2 352,22 MHz -9,2.10-2<uD/uQ<10,6.10-2 uQ(z) [u.a.] -6,4.10-2<(uQ-Vp)/Vp<3,4.10-2 -0,4.10-2<uD/uQ<0,4.10-2 uT(z) [u.a.] -0,2.10-2<(uQ-Vp)/Vp<0,2.10-2 Slug tuners : fast simultaneous convergence RFQ 2x1m Ref: F. Simoens, A. France, J. Gaiffier, “A New RFQ Model applied to the Longitudinal Tuning of a Segmented, Inhomogeneous RFQ with Highly Irregularly Spaced Tuners”, EPAC2002 Conference (Paris), June 2002

  9. A new tuning criteria : ‘quadratic shift frequency’ Voltage profiles of the first dipole mode before dipole rods tuning after dipole rods tuning steep slopes straightened slopes Dipole rods length adjustment  Matching of the equivalent end loads When df(n)real RFQ df(n)ideal RFQ  Good correspondence between the measured andthe ‘ideal’ dipole mode frequencies Refer to : F. Simoens, A. France, “Tuning procedure of the 5 MeV IPHI RFQ”, CEA-SACLAY, LINAC Conference (Gyungju, Korea), August 2002

  10. End region mismatch characterization :  parameter  = L x  f [m.MHz] L = RFQ half-length f = (mismatched resonance freq.) - (nominal cut-off freq.) Nominal mid-position thickness Example of the IPHI RFQ cold-model end region adjustment range[-0,24 m.MHz , +0,33 m.MHz] End plate thickness adjustment    0 m.MHz Refer to : F. Simoens, A. France, “Tuning procedure of the 5 MeV IPHI RFQ”, CEA-SACLAY, LINAC Conference (Gyungju, Korea), August 2002

  11. End #1 End #2 Slugs are moved at some distance of the end being tuned i.e. for end#1, in planes #6, 7 and 8 of segment #1 = set of different voltage excitations Spectral analysis  Parameter extraction from measurements End plate thickness adjustment  The nominal plate thickness is well-adjusted, Refer to : F. Simoens, A. France, “Tuning procedure of the 5 MeV IPHI RFQ”, CEA-SACLAY, LINAC Conference (Gyungju, Korea), August 2002

  12. Conclusion • Last results • The agreement between measurements, 3d simulations and our model validates our mathematical formalism. • The tuning procedures of the different mechanical devices have been developed and experimentally validated. • In a 2-m long RFQ, we have achieved relative voltage error lower than 10-2 within 3 steps of slug tuners displacements. • For the dipole rods adjustments, a new practical tuning criteria has been introduced, that ensures the convergence of tuning. • The end region mismatch can be characterized from a set different voltage excitations and directly related to the end plate thickness. • Studies in progress • Chronology of the different tuning procedures in the context of the RFQ machining and assembling steps. • RF power coupling (iris / loop).

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