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Preliminary DTL studies at RAL

Preliminary DTL studies at RAL. Ciprian Plostinar CCLRC, ASTeC, Intense Beams Group General HIPPI yearly meeting, Cosener’s House, Abingdon, UK. H - source. RFQ. MEBT. DTL. SCL. The goal. - To upgrade the ISIS spallation neutron source

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Preliminary DTL studies at RAL

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  1. Preliminary DTL studies at RAL Ciprian Plostinar CCLRC, ASTeC, Intense Beams Group General HIPPI yearly meeting, Cosener’s House, Abingdon, UK

  2. H-source RFQ MEBT DTL SCL The goal • - To upgrade the ISIS spallation neutron source • One of the upgrade phases consists in developing of a new injector comprising a 180 MeV linac and 2 booster synchrotrons (1.2 GeV) • The 180 MeV linac will replace the current 70 MeV injector The basic layout for the 180 MeV linac is:

  3. DTL requirements: • Ion species: H- • Input energy: 3 MeV • Output energy: 90 MeV • Operating frequency: 324 MHz • Current: 50 mA • Use Toshiba Klystrons (2.5 MW) ? • No of tanks: 4 (1 Klystron /Tank) • E field 2.5 MV/m • Maximum E field level: 1.3 Kilpatrick

  4. Rc f g/2 D/2 Ro L/2 F or Fd Drift tube g/2 Ri Rb Beam axis d/2 Rb Geometric parameters Rb – bore radius g –gap length L – cell length D – full cavity diameter d – drift tube diameter α – face angle Rc – corner radius Ri – inner nose radius Ro – outer nose radius F – flat segment

  5. Restrictions: • Use a constant tank diameter, bore radius and drift tube diameter along the structure. • Make room for quadrupoles inside the drift tubes. • Have a good shunt impedance • Avoid voltage breakdown Which are the parameters that influence this more?

  6. f Angle influence - Bigger face angles lead to higher shunt impedance, but, Leave less space for the quadrupoles, and increase the Kilpatrick.

  7. f • The optimum face angle should: • Allow enough space for the quadrupoles; • Give a good shunt impedance; • Avoid voltage breakdown. The face angle will change along the structure so these 3 conditions are fulfilled.

  8. How much space we should leave for the quadrupoles? 25 % more space for the quadrupoles than J-PARC DTL (3 – 50 MeV)

  9. What focussing lattice should we use? Comparing phase advance per unit length for different lattices we get: With a FFDD lattice we can get the same phase advance per unit length as for FODO cell, but with a 1.4 smaller quadrupole gradient So using a FFDD lattice will allow us more space for the quadrupoles, so more design freedom. But longer focussing periods lead to a growth in the beam size; Is it acceptable?

  10. f Optimum tank diameter - Larger tank diameters leave less room for the quadrupoles; - Smaller tank diameters leave more room for the quadrupoles but decrease the efficiency (see next slides) and increase the Kilpatrick ;

  11. Efficiency Kilpatrick

  12. Upper limit given by the quadrupole length and efficiency. Lower limit given by Kilpatrick and efficiency Best tank diameter curve

  13. SUPERFISH simulations (Gen_DTL) Input parameters: Rb (bore radius) = 1 cm D – full cavity diameter = 56 cm d – drift tube diameter = 14.8 cm Rc – corner radius = 0.5 cm Ri – inner nose radius = 0.15 cm Ro – outer nose radius = 0.3 cm F – flat segment = 0.2 cm Phase ramp

  14. Preliminary Results DTL Main parameters

  15. Parameters of each DTL tanks

  16. Lengths Face angle Longitudinal phase advance Shunt Impedance

  17. Conclusions and future work. • A preliminary design study has been done • Frequency: 324 MHz; • 4 DTL tanks to accelerate from 3 – 90 MeV; • Optimised tank parameters; • 47.7 m long; • One 2.5 MW Klystron/ Tank; • But, • No beam dynamics simulations has been done yet (next step); • Readjust the structure. • Choose a more complex design after 50 MeV (CCDTL)?

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