From 7d7581ed53ed6a27faa83c10b7dae4eb9f35ce95 Mon Sep 17 00:00:00 2001
From: gubaidulinvadim <gubaidulinvadim@gmail.com>
Date: Wed, 19 Feb 2025 10:28:33 +0100
Subject: [PATCH] Added an option to choose number of points to be considered
in the lattice for space-charge tune shift calculation. Renamed the function
to be 'Gaussian' transverse space-charge.
---
mbtrack2/instability/instabilities.py | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/mbtrack2/instability/instabilities.py b/mbtrack2/instability/instabilities.py
index 275faa6..c67bc22 100644
--- a/mbtrack2/instability/instabilities.py
+++ b/mbtrack2/instability/instabilities.py
@@ -456,7 +456,7 @@ def rwmbi_threshold(ring, beff, rho_material, plane='x'):
return Ith
-def transverse_space_charge_tune_shift(ring, bunch_current, **kwargs):
+def transverse_gaussian_space_charge_tune_shift(ring, bunch_current, **kwargs):
"""
Return the (maximum) transverse space charge tune shift for a Gaussian
bunch in the linear approximation, see Eq.(1) of [1].
@@ -480,6 +480,9 @@ def transverse_space_charge_tune_shift(ring, bunch_current, **kwargs):
If True, use beta fonctions along the lattice.
If False, local values of beta fonctions are used.
Default is ring.optics.use_local_values.
+ n_points : int, optional
+ Number of points in the lattice to be considered if use_lattice ==
+ True. Default is 1000.
sigma_delta : float, optional
Relative energy spread.
Default is ring.sigma_delta.
@@ -505,15 +508,15 @@ def transverse_space_charge_tune_shift(ring, bunch_current, **kwargs):
use_lattice = kwargs.get('use_lattice', not ring.optics.use_local_values)
sigma_delta = kwargs.get('sigma_delta', ring.sigma_delta)
gamma = kwargs.get('gamma', ring.gamma)
-
- q = np.abs(ring.particle.charge)
+ n_points = kwargs.get('n_points', 1000)
+ q = ring.particle.charge
m = ring.particle.mass
r_0 = 1 / (4*pi*epsilon_0) * q**2 / (m * c**2)
- N = bunch_current / ring.f0 / q
+ N = np.abs(bunch_current / ring.f0 / q)
sigma_z = sigma_s * c
if use_lattice:
- s = np.linspace(0, ring.L, 1000)
+ s = np.linspace(0, ring.L, n_points)
beta = ring.optics.beta(s)
sig_x = (emit_x * beta[0] +
ring.optics.dispersion(s)[0]**2 * sigma_delta**2)**0.5
--
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