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CCDTL design and prototype measurements M. Pasini, Abingdon September 28 th , 2005

CCDTL design and prototype measurements M. Pasini, Abingdon September 28 th , 2005. CONTENTS:. CCDTL structure, general concept. Beam Parameters Layout design philosophy Optimized layout Frequency error study CCDTL prototype – Mechanical remarks Low level measurements Conclusions.

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CCDTL design and prototype measurements M. Pasini, Abingdon September 28 th , 2005

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  1. CCDTL design and prototype measurementsM. Pasini, Abingdon September 28th, 2005 1

  2. CONTENTS: • CCDTL structure, general concept. • Beam Parameters • Layout design philosophy • Optimized layout • Frequency error study • CCDTL prototype – Mechanical remarks • Low level measurements • Conclusions 2

  3. Cavity structure 3

  4. Why CCDTL? • In the energy range 40-90 MeV the velocity of the particle is high enough to allow long drifts between focusing elements so that… • …we can put the quadrupoles lenses outside the drift tubes with some advantage for the shunt impedance but with great advantage for the installation and the alignment of the quadrupoles… • the final structure becomes easier to build and hence cheaper than a DTL. • The resonating mode is the p/2 which is intrinsically stable. 4

  5. ZT2 Curve DTL tank2 DTL tank3 CCDTL DTL tank1 5

  6. Beam Parameters 6

  7. Single Accelerating CCDTL tank 1 Power coupler / klystron Module A bit of Definitions… 7

  8. Layout design philosophy • Every tank has 3 accelerating gaps (2 drift tubes). • The klystron feeds a module that is made out of 3 tanks. • The level of the accelerating field from module to module is decreasing in order to have a even power load per klystron. • Synchronous phase is -20 deg. • Distance between tanks is constant (250 mm). This allow insertion of a quadrupole. 8

  9. CCDTL optimized Layout 9

  10. Voltage and Phase error study Results of a simulation of voltage and phase error for the synchronous particle with DV/V = 0.5% rms and Df = 0.5 deg rms Ref. M. Pasini, CARE/HIPPI Document-2005-006 10

  11. Coupling coefficients 9‰ Coupling factor k 6‰ Cavity number (#) 11

  12. PSPICE Simulation 12

  13. 13

  14. RMSfielderrors Df = ±50 kHz in all the 5 resonating cells 14

  15. CCDTL Prototype • A prototype consisting in 2 half accelerating cells and a full coupling cell has been built and assembled. • The delivery of the prototype was late by 6 months, mainly due to fabrication problems (steel quality) and copper plating preparation. (Finally successful at the 2 attempt). 15

  16. Coupling cell 2nd Half-tank (accelerating) 1st Half-tank (accelerating) 16

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  27. Low Level Measurements After single cell tuning K=0.88% coupling coefficient The measured Q-value is only 61 % with respect to Superfish. The cavity however was not properly closed and the tuners used were made of aluminum. 27

  28. Low Level Measurements 28

  29. Wave guide coupling factor measurement Distance between coupling iris and short circuit. 29

  30. Summary / Conclusions • A new reference layout has been calculated, the section length is now 25m (20% shorter then the previous layout) • Validation of the 20 degrees synchronous phase layout has been achieved. • Future layout will include a special subsection where the fields in the last 2 modules will be raised up in order to allow a smooth transition in term of longitudinal phase advance. This will imply the addition of one more klystron. 30

  31. Summary / Conclusions • Calculation on the frequency error leads to tolerable error in the fields. • The prototype is completely assembled. A low level measurement campaign has been performed and results are reported. • Final assembly and tuning is foreseen in October and high power test in November. 31

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