1. January 5, 2004S. A. Pande - CAT-KEK School on SNS 1 100 MeV Injector Linac for Indian Spallation Neutron Source S. A. PANDE

2. The Spallation Neutron Source Ion SourceRFQ Linac 1 GeV Proton Synchrotron Spallation target 50 keV4.5 MeV100 MeV

3. January 5, 2004S. A. Pande - CAT-KEK School on SNS 3 Synchrotron Parameters Injection energy100 MeV Extraction energy1.0 GeV Circumference212.4 m Radio Frequency1.21 – 2.47 MHz Repetition rate25 Hz Beam power100 kW No of protons/pulse2.5x10 13

4. January 5, 2004S. A. Pande - CAT-KEK School on SNS 4 Requirements From Injector Linac Output energy100MeV ParticlesH – Pulse current20ma Pulse length500  s Repetition rate25Hz

5. January 5, 2004S. A. Pande - CAT-KEK School on SNS 5 Layout of the Linac Ion Source LEBT & Chopper RFQMEBTDTL HEBT + Long. & Trans. Phase Space Painting 1 GeV Proton Synchrotron 50 keV4.5 MeV100 MeV

6. January 5, 2004S. A. Pande - CAT-KEK School on SNS 6 Low Energy Beam Transport (LEBT) Required for the following. Phase space matching of the beam from ion source to RFQ Putting diagnostics after the ion source Vacuum pumping provision Additionally, LEBT will house the chopping system in our case

7. January 5, 2004S. A. Pande - CAT-KEK School on SNS 7 The Chopper System Why it is required to chop the beam? The 500  sec beam pulse will be sufficient to wrap ~302 times around the synchrotron With harmonic no.(h)= 2, there will be 2 RF buckets. Bucket height EE Synch. RF Period

8. January 5, 2004S. A. Pande - CAT-KEK School on SNS 8 The Chopper (Contd.) The RF bucket height decreases at the ends (shown by yellow circles in the last slide) and particles falling in these regions will be lost These lost particles form a considerable amount of the injected beam (at 100 MeV!) Why not stop this beam being injected into the synchrotron or in the linac itself.

9. January 5, 2004S. A. Pande - CAT-KEK School on SNS 9 Chopper (Contd.) This is done using the chopper system The chopper will be an electrostatic deflector assembly sweeping the beam across a circular aperture ~34% of the beam will be stopped and 66% will be transmitted through the linac

10. January 5, 2004S. A. Pande - CAT-KEK School on SNS 10 The Chopper (Contd.) Synch. RF Period Injected Chopped  120  of RF Period  

11. January 5, 2004S. A. Pande - CAT-KEK School on SNS 11 Radio Frequency Quadrupole (RFQ) Choice of Parameters – main considerations

12. January 5, 2004S. A. Pande - CAT-KEK School on SNS 12 Choice of Parameters - RFQ Main considerations will be- To control the emittance growth Less power loss in the structure to enable efficient removal of heat Higher transmission efficiency to reduce the risk of structure activation Choice of Structure Higher efficiency, simplicity in heat removal  Four Vane Cavity Structure

13. January 5, 2004S. A. Pande - CAT-KEK School on SNS 13 Input/output Energy Input energy can be anywhere from 30 to 100 keV Higher output energy is preferred from injection point of view in the following accelerator The RFQ output energy range from 3 MeV to 7 MeV for similar projects around the world  The output energy chosen is 4.5 MeV

14. January 5, 2004S. A. Pande - CAT-KEK School on SNS 14 The Design Frequency Major factor – Availability RF Power Source Higher power conversion efficiency f 1/2  Choice of higher frequency Dimensional tolerancesf -1/2 Power dissipation capability of the accelerator structure f -1  Choice of lower frequency Considering CW operating mode, machining and alignment tolerances, we chose f = 350 MHz

15. January 5, 2004S. A. Pande - CAT-KEK School on SNS 15 Inter-vane Voltage Higher inter-vane voltage preferred for Better transverse focusing and better beam characteristics Better transmission efficiency Higher acceleration efficiency & in turn shorter accelerator length Lower inter-voltage is preferred for Lower power loss in the structure Less probability of sparking

16. January 5, 2004S. A. Pande - CAT-KEK School on SNS 16 Inter-vane Voltage (Contd.) Power dissipation in the structure  V 2 Acceleration or energy gain  V Being a CW accelerator, the last point is of crucial importance. The inter-vane voltage between 65-90 kV should be a good choice. We generated RFQ designs with Inter-voltages of 65, 70, 75, 80 and 85 kV The design with 65 kV is selected

17. January 5, 2004S. A. Pande - CAT-KEK School on SNS 17 Radio Frequency Quadrupole (RFQ) Frequency350MHz Energy4.5MeV Beam current25mA Inter vane voltage65kV ParticleH + /H – Total length 6.52m Transmission efficiency96.3% Total power loss(structure)428kW Beam power111.25kW Max. surface E field (Emax)26MV/m Kilpatrick 1.4

18. January 5, 2004S. A. Pande - CAT-KEK School on SNS 18 RFQ – Design Parameters Modulation Parameter (m)1 – 1.915 Average radius (r 0 )3.30mm Synchronous phase (  s )-90 - -30  Transmission efficiency (  )96.3% Input emitt.  t,rms (n)0.20  m.rad Output emitt.  t,rms (n)0.20  m.rad Output emitt.  z,rms (n)0.10 deg.MeV Quality factor (Q 0 ) 9000

19. January 5, 2004S. A. Pande - CAT-KEK School on SNS 19 RFQ – Design Parameters Modulation Parameter (m)1 – 1.915 Average radius (r 0 )3.30mm Synchronous phase (  s )-90 - -30  Transmission efficiency (  )96.3% Input emitt.  t,rms (n)0.20  m.rad Output emitt.  t,rms (n)0.20  m.rad Output emitt.  z,rms (n)0.10 deg.MeV Quality factor (Q 0 )9000

20. January 5, 2004S. A. Pande - CAT-KEK School on SNS 20 RFQ Cavity Characteristics Four vane structure Transverse cross section optimized with SUPERFISH Power loss = 656 W/cm Power density 6 W/cm 2 3D Study with MAFIA is in progress to decide about joining the multiple sections.

21. January 5, 2004S. A. Pande - CAT-KEK School on SNS 21 100 MeV DTL as injector for SNS DTL is designed for 50 mA with a view to inject more current into synchrotron with increased injection energy. A 50 mA RFQ is redesigned with 85 kV intervane voltage, Length = 5.5 m. Beam dynamics design is performed with PARMILA. Beam available from RFQ is traced through DTL MEBT design and matching through DTL is studied with TRACE3D

22. January 5, 2004S. A. Pande - CAT-KEK School on SNS 22 Matched beam through DTL

23. January 5, 2004S. A. Pande - CAT-KEK School on SNS 23 Beam transmission through DTL

24. 100 MeV DTL - Parameters Energy100MeV Beam current50 mA Average E 0 1.8 – 2.2MV/mm Synchronous phase-60 – -30  Length74meters Number of Tanks7 Tank diameter52 – 50 – 48 cm Total power6.76MW Focussing latticeFODO Input  Tr (n,rms)0.2  mm mrad Output  Tr (n, rms)0.28  mm mrad  Long (n, rms)0.197deg.MeV Energy spread (100%)  450keV Phase spread (100%)  16.6  rms radius at O/P1.27mm

25. January 5, 2004S. A. Pande - CAT-KEK School on SNS 25 Beam at the Output