Threshold and bursting dynamics of the CSR instability in electron rings · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
Threshold and bursting dynamics of the CSR instability in electron rings
Plain
In storage rings run with very short bunches, above a certain current the bunch breaks into ripples and emits bursts of far-infrared light; the threshold and the bursting pattern are only partly predicted.
Precise · changed · core
Revision 1: For a Gaussian bunch in an electron ring with the shielded steady-state CSR impedance, Vlasov-Fokker-Planck calculations give a threshold in the dimensionless current $S_{\mathrm{csr}}$ of approximately S_csr,th = 0.5 + 0.12 $\Pi$, with Pi the shielding parameter, plus a narrow low-threshold region near $\Pi \sim 0.7$ (2010). Determine whether the threshold and the period and amplitude of sawtooth bursting above it are predicted within 20 percent once the full ring impedance, potential-well distortion and finite chamber geometry are included, in low-momentum-compaction operation of several rings.
Revision 2: For a Gaussian bunch in an electron ring with the shielded steady-state CSR impedance, Vlasov-Fokker-Planck calculations give a threshold in the dimensionless current $S_{\mathrm{csr}}$ of approximately $S_{\mathrm{csr}},\mathrm{th} = 0.5 + 0.12$ $\Pi$, with $\Pi$ the shielding parameter, plus a narrow low-threshold region near $\Pi \sim 0.7$ (2010). Determine whether the threshold and the period and amplitude of sawtooth bursting above it are predicted within 20 percent once the full ring impedance, potential-well distortion and finite chamber geometry are included, in low-momentum-compaction operation of several rings.
Settled by
Bunch-by-bunch measurements of threshold current and burst spectra versus Pi in two or more rings, compared with Vlasov-Fokker-Planck solutions that use independently measured impedances.
Kind
well-posed
Answer type
value
References
(empty)
Literature status
partially-resolved
Status note
Measured thresholds in low-momentum-compaction modes of several rings in the 2010s were broadly consistent with the scaling law; bursting dynamics above threshold are reproduced only qualitatively (moderate confidence, not rechecked for 2024-2026).
Posed since
(empty)

Decisions