def test_eloss_with_4he(self):
en = 1.
m = 4
z = 2
res = self.he.energy_loss(en, m, z)
bth = pytpc.gases.bethe(rel.beta(en, m*p_mc2), z, self.he.electron_density_per_m3, self.he.mean_exc_pot)
self.assertAlmostEqual(res, bth, delta=10)
def test_eloss_with_4he(self):
en = 1.
m = 4
z = 2
res = self.he.energy_loss(en, m, z)
bth = pytpc.gases.bethe(rel.beta(en, m * p_mc2), z,
self.he.electron_density_per_m3,
self.he.mean_exc_pot)
self.assertAlmostEqual(res, bth, delta=10)
def energy_loss(self, en, proj_mass, proj_charge):
"""Finds the energy loss of a projectile in the gas.
This default version uses the Bethe formula (defined by the function `bethe`) to calculate the energy loss.
This function may be overridden with an empirical fit to give better results.
Parameters
----------
en : float
The kinetic energy of the projectile, in MeV
proj_mass : int
The mass number of the projectile
proj_charge : int
The charge number of the projectile
Returns
-------
dedx : float
The stopping power in MeV/m
"""
beta = rel.beta(en, proj_mass * p_mc2)
return bethe(beta, proj_charge, self.electron_density_per_m3, self.mean_exc_pot)
def energy_loss(self, en, proj_mass, proj_charge):
"""Finds the energy loss of a projectile in the gas.
This default version uses the Bethe formula (defined by the function `bethe`) to calculate the energy loss.
This function may be overridden with an empirical fit to give better results.
Parameters
----------
en : float
The kinetic energy of the projectile, in MeV
proj_mass : int
The mass number of the projectile
proj_charge : int
The charge number of the projectile
Returns
-------
dedx : float
The stopping power in MeV/m
"""
beta = rel.beta(en, proj_mass * p_mc2)
return bethe(beta, proj_charge, self.electron_density_per_m3, self.mean_exc_pot)
def test_value(self):
for e in range(1, 40):
for m in range(1, 40):
exp = (sqrt(e) * sqrt(e + 2 * m)) / (e + m)
self.assertAlmostEqual(rel.beta(en=e, mass=m), exp, places=5)
def test_zero_energy(self):
self.assertEqual(rel.beta(0.0, 4), 0)
def test_zero_mass(self):
self.assertEqual(rel.beta(4, 0), 1)
def test_value(self):
for e in range(1, 40):
for m in range(1, 40):
exp = (sqrt(e) * sqrt(e + 2*m)) / (e + m)
self.assertAlmostEqual(rel.beta(en=e, mass=m), exp, places=5)
def test_zero_energy(self):
self.assertEqual(rel.beta(0.0, 4), 0)
def test_zero_mass(self):
self.assertEqual(rel.beta(4, 0), 1)
def beta(self):
"""The particle's beta, or v/c"""
en = self.energy
m = self.mass
return rel.beta(en, m)
