multi-turn extraction tracking simulation for JPARC-MR

1. multi-turn extraction tracking simulation for JPARC-MR A. Ando, T. Koseki, S. Mihara, N. Saito, A. Sakumi*, K.Satoh, M. Tomizawa and M. Tawada KEK*) Univ of Tokyo 2008.06.12 BNL g-2 meeting

2. Introduction JPARC-MR • Circumference 1567.5m with 3-116m long straight sections. • 3.3x1014 protons per pulse (15uA) full beam power: 750kW at 50GeV • Extraction energy: 30 GeV (Phase-I) • Emittance 10 pi mm-mrad (design) @30 GeV

3. Introduction JPARC-MR • May 22, 2008 3Gev proton beams were successfully injected to JPARC-MR. • Beam were captured by RF and dumped after 1000 turns. • Acceleration to 30 GeV and beam extraction will start in the end of this year.

4. Purpose of this simulation • Split a beam into 5 or 4 beams in transverse phase space in JPARC-MR. • We want to study the following issues by using simulation. • Can nonlinear elements create stable islands in JPARC-MR? (Do higher order components degrade the islands?) • Is there enough beam separation space for extraction? • Can the fraction of each beam be equal? • How much is the beam loss at septum magnet? • Estimate machine error tolerances.

5. Simulation model • MR lattice: FODO • Sextupole magnets which are used for chromaticity corrections are included. • Higher order multi-pole components at 30GeV are different from that at 3 GeV due to the magnet saturation. Correction data, which are measured for 96 bend and 216 quadrupole magnets at 30GeV are also included in lattice file. • One octupole and one sextupole are added to straight section for simulation. • Using SAD and MAD program for parameter survey and particle tracking. • 6D full symplectic tracking can be done but 4D tracking was performed for simplicity.

6. JPARC-MR Lattice + Sextupole & Octupole

7. Evolution of tune in simulation • The fourth order resonance is assumed to be used. • Change Horizontal tune 0.255 → 0.245 every 50 turns. • We tried several working point for vertical tune. • Vertical tune and the strength of sextupole and octupole are kept constant. • Horz. chromaticity is small ( ξx < 1)

8. Evolution of Horz. phase space plot nx=0.255 nx=0.250 nx=0.245

9. Evolution of distribution • Beam emittances for horz. and vert. are assumed as 10 pi mm-mrad. • Parabolic beam distribution is assumed for the initial condition. • Horz. beam distribution in phase space is plotted every 500 turns. • Typically, it takes one hour for 1000 particles and 20000 turns. • The rotation of islands can be adjust to right-angle by changing ocutpole and sextupole position.

10. Estimation of particles loss at the septum • 5mm septum thickness is assumed here. • The fraction of core particle have about 50%. • Islands fraction: about 10% • 50/1000=0.5% will be lost at septum magnet

11. 5 pi mm-mrad 10 pi mm-mrad (design) 15 pi mm-mrad Initial beam emittance dependence 1 pi mm-mrad ・Fraction of trapped particles and particle loss at septum magnet depends on initial beam emittance.

12. K2=2.6 K3=-35 K2=2.0 K3=-90 Parameter survey • We are trying to find good parameter to increase the islands particles. • Sakumi-san found several candidates at nx=0.25. • But no islands are obtained for these parameters in tracking simulation.

13. Parameter survey nx=0.255 K2=2.0 K3=-90 nx=0.250 nx=0.245

14. Amplitude dependence of tune • We try to follow CERN experiment to increase islands particles. • CERN group show it is important to erase amplitude dependence of horizontal tune by octupole strength. • K3 is trimmed during crossing 0.25. • This effect was small.Something wrong?

15. Summary • Multi-turn extraction for JPARC-MR is studied. • Tracking simulation shows • Stable islands can be obtained. • Enough beam separation space between core and islands is obtained • core fraction have 47%. island fraction: 13%. • Beam loss: <1% • Issues • Increase the fraction of islands particles. • Machine error tolerances. • …