Sheath thickness functions #401

jasperbeckers · 2018-04-24T14:57:45Z

Adds matrix and Child law sheath thickness functions to parameters.py. These are important in characterizing a plasma and defining criteria for the use of probes and other diagnostics (one of the items of #339).

StanczakDominik · 2018-04-24T17:52:12Z

We sorta agreed a while ago to increase the line character limit for our code to 100. We should really make that more visible somehow.

jasperbeckers · 2018-04-24T18:00:11Z

That's great! But are we going to refactor all current code for the new limit?

StanczakDominik · 2018-04-24T18:03:46Z

Oh no, that would be a massive waste of time! I just mention that because the other changes you made to this module looked like you were shortening lines to fit 80, and I just wanted to keep you from wasting time on that :)

StanczakDominik · 2018-04-24T18:43:32Z

I would kinda like to keep the current feature set before v0.1. Would you be fine with not merging this PR before that's done?

jasperbeckers · 2018-04-24T18:48:01Z

Yes, seems like a good plan.

lemmatum

Improve the tests a bit and then this should be good to merge.

lemmatum · 2018-04-30T17:18:35Z

plasmapy/physics/parameters.py

+
+ lambda_D = Debye_length(T_e, n_s)
+
+ s = (np.sqrt(2) / 3) * lambda_D * (2 * e * V_0 / T_e) ** 0.75


Will the units here work out? Does astropy.units know that V/eV is unitless?

We might want to put these things in terms of kelvins or at least allow for interoperability (as per prior discussions).

lemmatum · 2018-04-30T17:21:01Z

plasmapy/physics/tests/test_parameters.py

+
+ V_0 = 80 * u.V
+
+ assert matrix_sheath_thickness(V_0, n_e).unit.is_equivalent(u.m)


separate methods for each assert.

lemmatum · 2018-04-30T17:21:19Z

plasmapy/physics/tests/test_parameters.py

+
+ assert matrix_sheath_thickness(V_0, n_e).unit.is_equivalent(u.m)
+
+ assert np.isclose(matrix_sheath_thickness(V_0, n_e).value, 1.329823977068723e-05)


error string message for when asserts fail.

# Conflicts: # plasmapy/physics/parameters.py

pep8speaks · 2018-05-01T12:10:39Z

Hello @jasperbeckers! Thanks for updating your pull request.

In the file plasmapy/physics/parameters.py, following are the PEP8 issues :

Line 1173:5: E128 continuation line under-indented for visual indent

Comment last updated on August 11, 2018 at 09:42 Hours UTC

…asmaPy into langmuir-update

samurai688 · 2018-05-19T21:19:11Z

plasmapy/physics/parameters.py

+ Sheath potential in units convertible to V.
+
+ n_s : ~astropy.units.Quantity
+ Sheath ion density in units convertible to m**-3.


Might be good to include some more description here of exactly which density is meant, since in the Child-law sheath the ion density is changing throughout the sheath. I'm 95% sure here you mean the density at the "sheath edge", or the point at which the ions have been accelerated to the Bohm speed through the presheath, and quasineutrality begins to break down. I think for a collisionless presheath this density is 1/sqrt(e) n_i ~= 0.606 n_i of the "bulk" plasma density n_i outside the presheath.

Yes, and make sure to make this clear throughout the Langmuir probe code.

lemmatum

I'm happy with merging this - just some minor suggested fixes.

lemmatum · 2018-05-20T02:29:49Z

plasmapy/diagnostics/langmuir.py

@@ -273,7 +273,8 @@ def swept_probe_analysis(probe_characteristic, probe_area, gas,
 Estimate of the ion saturation current in units of Am^-2.

 "hot_fraction" : float
- Estimate of the total hot (energetic) electron fraction.
+ Estimate of the total hot (energetic) electron fraction. Only supplied
+ if bimaxwellian is True.


This is minor, but I would call it a "bi-Maxwellian"

re: @lemmatum: "bi-Maxwellian" is a better name, but it won't work as an argument.

lemmatum · 2018-05-20T02:31:59Z

plasmapy/physics/parameters.py

@@ -974,7 +990,8 @@ def plasma_frequency(n, particle='e-', z_mean=None):
 # using user provided average ionization
 Z = z_mean
 Z = np.abs(Z)
- # TODO REPLACE WITH Z = np.abs(_grab_charge(particle, z_mean)), some bugs atm
+ # TODO REPLACE WITH Z = np.abs(_grab_charge(particle, z_mean)), some


Are you going to do this? If not, raise it as a separate issue.

lemmatum · 2018-05-20T02:33:52Z

plasmapy/physics/parameters.py

+ Sheath potential in units convertible to V.
+
+ n_s : ~astropy.units.Quantity
+ Sheath ion density in units convertible to m**-3.


Yes, and make sure to make this clear throughout the Langmuir probe code.

lemmatum · 2018-05-20T02:34:22Z

plasmapy/physics/parameters.py

+ If one or more of the supplied parameters are not of the correct type.
+
+ ~astropy.units.UnitConversionError
+ If one or more parameter cannot be succesfully converted to the


parameters, plural

lemmatum · 2018-05-20T02:34:37Z

plasmapy/physics/parameters.py

+ respective unit.
+
+ ValueError
+ If one or more parameter does not have an appropriate value.


same as above - fix throughout

lemmatum · 2018-05-20T02:36:24Z

plasmapy/physics/parameters.py

+ -----
+ The Child law sheath model is self-consistent in terms of ion density
+ throughout the sheath and assumes a large sheath potential compared to the
+ electron temperature. The sheath thickness is given by


Out of curiosity, is there a good or commonly used criterion for this? For example, a potential 100x larger than electron temperature?

lemmatum · 2018-05-20T02:37:09Z

plasmapy/physics/tests/test_parameters.py

+ V_0 = 80 * u.V
+
+ def test_correct_unit(self):
+ assert matrix_sheath_thickness(self.V_0, n_e).unit.is_equivalent(u.m), \


replace continuation slash

lemmatum · 2018-05-20T02:37:59Z

plasmapy/physics/tests/test_parameters.py

+ V_0 = 80 * u.V
+
+ def test_correct_unit(self):
+ assert Child_law_sheath_thickness(T_e, self.V_0, n_e).unit.is_equivalent(u.m), \


replace continuation slash

StanczakDominik

The code looks good, but I think there's a few doc fixes that would make this look much better!

StanczakDominik · 2018-05-28T05:03:57Z

plasmapy/diagnostics/langmuir.py

@@ -273,7 +273,8 @@ def swept_probe_analysis(probe_characteristic, probe_area, gas,
 Estimate of the ion saturation current in units of Am^-2.

 "hot_fraction" : float
- Estimate of the total hot (energetic) electron fraction.
+ Estimate of the total hot (energetic) electron fraction. Only supplied
+ if bimaxwellian is True.


re: @lemmatum: "bi-Maxwellian" is a better name, but it won't work as an argument.

StanczakDominik · 2018-05-28T05:09:54Z

plasmapy/physics/parameters.py

+ 'n_s': {'units': u.m ** -3, 'can_be_negative': False}
+ })
+def matrix_sheath_thickness(V_0, n_s):
+ r"""Calculate the matrix sheath thickness for a high potential sheath.


I think this could potentially be more descriptive than repeating the function's name, but I don't really have any better suggestions!

StanczakDominik · 2018-05-28T05:10:24Z

plasmapy/physics/parameters.py

+ >>> matrix_sheath_thickness(80 * u.V, 1e18 * u.m**-3)
+ <Quantity 9.40327552e-05 m>
+
+ """


We could probably use a reference here.

StanczakDominik · 2018-05-28T05:11:15Z

plasmapy/physics/parameters.py

+ >>> Child_law_sheath_thickness(1e6 * u.K, 80 * u.V, 1e18 * u.m**-3)
+ <Quantity 5.17439662e-05 m>
+
+ """


Likewise, a reference would be nice to have here.

StanczakDominik · 2018-05-28T05:12:56Z

plasmapy/physics/tests/test_parameters.py

+ errStr = (f"The test result value of matrix_sheath_thickness is not correct "
+ f"and returns {test_result} instead of {expected}.")
+
+ assert test, errStr


I really think we need to start using http:https://docs.astropy.org/en/stable/api/astropy.tests.helper.assert_quantity_allclose.html?highlight=assert this function rather than run our custom checks! I'll just keep grumbling in reviews about it, I guess.

lemmatum · 2018-08-09T19:54:21Z

bump can we resolve conflicts, get those minor fixes done, and merge this?

lemmatum · 2018-11-07T15:51:15Z

bump the 2nd

github-actions · 2021-04-02T03:05:57Z

This pull request will be closed in 14 days due to a year of inactivity unless the stale label or comment is removed.

StanczakDominik · 2021-04-13T19:02:38Z

I will try to pick this up and finally get it merged!

... sometime for 0.7 :)

Adds sheath thickness functions

73e7050

jasperbeckers added 2 commits April 24, 2018 20:09

Adds tests for sheath thickness functions

d70ac3d

Test fix

5112ba4

StanczakDominik added this to the v0.2 milestone Apr 24, 2018

StanczakDominik self-requested a review April 24, 2018 18:43

jasperbeckers added the status: ready to merge label Apr 24, 2018

StanczakDominik force-pushed the master branch 4 times, most recently from 02e758d to 749a6bd Compare April 29, 2018 16:04

lemmatum self-requested a review April 30, 2018 17:13

lemmatum suggested changes Apr 30, 2018

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jasperbeckers added status: nearing completion and removed status: ready to merge labels Apr 30, 2018

jasperbeckers added 3 commits May 1, 2018 11:27

Switch accepted unit to Kelvin, refactor and document tests

90997e7

Merge https://github.com/PlasmaPy/PlasmaPy into langmuir-update

feffe84

# Conflicts: # plasmapy/physics/parameters.py

Fixes tests

01277b4

jasperbeckers added 7 commits May 1, 2018 13:28

Fix for the test fix

7730623

Turns out np.isclose cannot handle Quantities

f2480a3

Remove whitespace

3e48116

Break up a number of long lines

172aaed

Break up a number of long lines

43de901

Merge branch 'langmuir-update' of https://github.com/jasperbeckers/Pl…

8632d97

…asmaPy into langmuir-update

Recommit

4528bcd

samurai688 previously approved these changes May 19, 2018

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lemmatum previously approved these changes May 20, 2018

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Merge branch 'master' into HEAD

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Sheath thickness functions #401

Sheath thickness functions #401

jasperbeckers commented Apr 24, 2018

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		lambda_D = Debye_length(T_e, n_s)

		s = (np.sqrt(2) / 3) * lambda_D * (2 * e * V_0 / T_e) ** 0.75


		V_0 = 80 * u.V

		assert matrix_sheath_thickness(V_0, n_e).unit.is_equivalent(u.m)


		assert matrix_sheath_thickness(V_0, n_e).unit.is_equivalent(u.m)

		assert np.isclose(matrix_sheath_thickness(V_0, n_e).value, 1.329823977068723e-05)

Sheath thickness functions #401

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Sheath thickness functions #401

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