Beam quality and beam loss predictions with space charge for SIS100

Abstract

The SIS100 synchrotron as a part of the new FAIR accelerator facility at GSI should be operated at the "space charge limit" for light and heavy-ion beams. Losses due to space charge induced resonance crossing should not exceed a few percent during a full cycle. Detailed magnet field measurements are now available for 72 out of the total 108 main SIS100 dipole magnets. Particle tracking studies including nonlinear field errors up to 7 th order in the main magnets together with different space charge models are performed. Because of the long time scales reduced space charge models are employed for tune scans. First comparisons with simulations using a self-consistent space charge solver are discussed as well as potential measures to further improve the options in tune space for the reference intensities and beyond. K: Accelerator modelling and simulations (multi-particle dynamics; single-particle dynamics); Beam dynamics; Beam Optics 1Corresponding author.

Simulation Study of the Space Charge Limit in Heavy-ion Synchrotrons

“…Contrary to the static field maps in FFSC, the adaptive model picks up and amplifies the macro-particle noise through the field updates. While it is possible to suppress the macroparticle noise impact in the AFSC by choosing larger numbers of macro-particles, relative convergence has only been observed with high numerical resolutions of up to 50 times more macro-particles than FFSC [28]. Despite the suppressed noise effect, the AFSC results still exhibit a systematic overshoot in the predicted rms emittance growth compared to PIC and FFSC around the upper edge of the stop-band.…”

“…The stochastic field error model considered in the simulations is based on cold bench measurements and has been described in detail in Ref. [28]. A summarising overview is found in Appendix B.…”

“…The development of the error model has been described in detail in Ref. [28] and is based on cold bench measurements of the real magnets. Figures 20a and 20b exhibit the corresponding multipole components of the field error models for the dipole and quadrupole magnets, respectively.…”

Impact of Field Errors of Quadrupole Units on Beam Losses at SIS100 Injection

“…The nonlinear part has been described in detail in Ref. [2,Section 2]. Beam simulations demonstrate that the multipole errors beyond dodecapolar order b 6 (with figures around or below 0.5 units) have no effect on the losses with space charge during accumulation of heavy ions.…”

“…b 3 = 0.7 (not 0.6), b 5 = 1.0 (not 0.9), a 3 = 1.2 (not 0.5) and a 6 = 1.0 (not 0.8). 2 The measurement protocols of the 10 cold quadrupole units bear the CIDs 02000090630, 02000090647, 02000090654, 02000090661, 02000090678, 02000091330, 02000091354, 02000091361, 02000091378, 02000091385 in the respectively tagged reports prepared by JINR Institute, Dubna. • a halved normal octupolar component (≈ factor 0.6),…”