BEAM DYNAMICS SIMULATIONS ON THE ESS BILBAO RFQ

Transcription

1 BEAM DYNAMICS SIMULATIONS ON THE ESS BILBAO RFQ D. de Cos, I. Bustinduy, J. Feuchtwanger, J.L. Muñoz, A. Vélez, O. González, ESS Bilbao, Spain A. Letchford, ISIS (RAL), UK S. Jolly, P. Savage, Imperial College London, UK F.J. Bermejo, V. Etxebarria, J. Portilla, UPV/EHU, Bilbao, Spain

2 OUTLINE ESS Bilbao Overview Characteristics of the RFQ RFQ Vane Modulation Design: RFQSIM Multiparticle Tracking Simulations Slide 2 of 18 RFQSIM GPT Conclusions and Future Work

3 ESS BILBAO OVERVIEW In development LINAC in Bilbao (Spain). Will accelerate H+ and H beams up to 50 MeV in the first stage, and plans to reach ~500 MeV in a later second stage. Pulsed beam ~ 1.5 ms long, up to 75 ma of peak current. Source (75 kev) LEBT RFQ (3 MeV) MEBT DTL (50 MeV) Slide 3 of 18

4 RFQ CHARACTERISTICS 4 vane RFQ, accelerates from 75 kev to 3 MeV. RF frequency of MHz. Cavity design: couplers and tuners positions Slide 4 of 18 Project tasks (I)

5 RFQ CHARACTERISTICS Project tasks (II) Low Level RF control system, cold model to be built in Aluminum. Slide 5 of 18

6 RFQ CHARACTERISTICS Project tasks (III) Thermo mechanical simulations to design cooling system. Vacuum system. Mechanical design: four models will be fabricated in oxygen free copper, in order to test different part joining methods. Vane modulation design: RFQSIM. Slide 6 of 18

7 RFQ VANE MODULATION RFQSIM Vane modulation designed with RFQSIM (written by Alan Letchford, ISIS). Generates cell parameters based on the K T method. Performs particle tracking simulations using 8 term multipole expansion. Many variables need to be scanned in order to find the best designs. Designs evaluated in terms of length, Bravery Factor, particle tracking results (emittance growth, transmission). ɸ sh ɸ gb ɸf Slide 7 of 18 a (mm) m Wgb (MeV) BF Length (m) Cells Δ Ɛ (%) Transm. (%)

8 RFQ VANE MODULATION Modulation parameters Total length = 3.89 m, 306 cells. Average displacement (R0) of 3.09 mm, final synchronous phase (ɸs) of 30o. Bravery Factor ~ Slide 8 of 18

9 BEAM DYNAMICS RFQSIM multiparticle tracking INPUT Protons, 5000 macroparticles. K = 75 kev, I = 75 ma. Ɛ = 0.20 π mm mrad. Input beam C S parameters calculated with Trace2D. Distribution: 4D waterbag transv., 2D waterbag longitudinally. OUTPUT K = 3.01 MeV, I = 72.2 ma. Ɛ < 0.21 π mm mrad. ΔK/K = 0.37%, with 92% of the particles less than 20 kev apart from the mean energy. Slide 9 of 18

10 BEAM DYNAMICS GPT: overview General Particle Tracer (Pulsar Physics, NL). RFQSIM space charge algorithm implemented into GPT. Same input distribution as the one used in RFQSIM simulations. GPT has no specific code for RFQs: Field map calculated externally using 8 term multipole expansion, then used as an input in GPT. Boundaries not defined First results: very good transmissions, but poor emittances. Slide 10 of 18

11 BEAM DYNAMICS Slide 11 of 18 GPT: particle killing

12 BEAM DYNAMICS Slide 12 of 18 GPT: video (start)

13 BEAM DYNAMICS Slide 13 of 18 GPT: video (50 ns)

14 BEAM DYNAMICS Slide 14 of 18 GPT: video (150 ns)

15 BEAM DYNAMICS Slide 15 of 18 GPT: video (300 ns)

16 BEAM DYNAMICS Slide 16 of 18 GPT: video (430 ns)

17 BEAM DYNAMICS Slide 17 of 18 Comparison: RFQSIM vs. GPT

18 CONCLUSIONS AND FUTURE WORK We have presented a vane modulation design for the ESS Bilbao RFQ. Multiparticle tracking simulations performed using two different computer codes show promising results. Future work: Slide 18 of 18 Perform simulations with TRACK (Brahim Mustapha). Create 3D model, obtain a field map from Finite Element Analysis. Estimate acceptance. Vane geometry error analysis.