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User Guide

See also Help tab of the tool (?-tab)

About this Tool

Version 1.0
Authors: Julia Branke and Erwin Verwichte
email: Julia.Branke(at), Erwin.Verwichte(at)

Centre for Fusion, Space and Astrophysics
Department of Physics, University of Warwick
Coventry CV4 7AL, West-Midlands, United Kingdom

Sponsored by EPSRC Science and Innovation Grant, EU FP7 CA FUSENET

Scope and Aims of the Tool

The aim of this interactive tool is to provide students and scientists alike a quick and easy way of calculating some basic physical quantities in plasma physics for pre-defined or custom plasma conditions. For instance, the tool can answer a question such as:

What is the Alfven speed given a magnetic field strength and total number density?

or a much more specific question,

For a deuterium-tritium plasma, given a magnetic field strength, number density of electrons and abundance of tritium, what is the Alfven speed?

We assume a uniform plasma. Where these quantities are normally vectors, we only provide a magnitude value.


This tool is a java applet. Therefore, in order to run you need to have java installed on your computer and enabled for your web browser.

How to use this Tool

At the heart of the tool is of course the physical calculations and you can read through in detail how every quantity is defined and calculated using the

Help tab of the tool

The tool consists of two panels, a top input panel and a bottom output panel. Also have a look at the Slides for a visual run-through.

The input panel

The input panel is divided into 5 parts: main, fields, bulk plasma, particle species and typical scales.

The user has three basic options of how to enter plasma parameters: two-species bulk, two-species and three species.

If the user choses two-species bulk, then the total number density, temperature, flow speed and current density are taken as the basis to do the calculations. Note that the part on particle species is grey and nothing can be entered there. Those quantities are derived from the bulk quantities. The temperature for both electrons and ions is assumed to be the same and equal to the bulk temperature.

If the user choses two-species, then the electron and ion number density, temperature and speed are taken as the basis for the calculations. Note that now the part on bulk quantities are grey and nothing can be entered there. The part on the three species is also still unavailable.

Finally, if the use choses three-species, then the electron and ion (including a second ion species) number density, temperature and speed are taken as the basis for the calculations.

The user can switch between these options and the tool automatically recalculates. However, it is important to be aware that when switching from a species choices to the bulk choice, that assumptions need to be made. For instance, the bulk temperature will be taken to be equal to the temperature of the main ion species.

Every entry field has in front of it a small information link, which will bring up the exact definition of the quantity. Also, behind the field is a drop-down menu where the user can toggle the units between SI and cgs.

The drop-down menu contains user-friendly tools and actions.

The user can choose from a list of pre-defined plasmas such as tokamak, solar corona, etc... to have a starting point to use the tool. If a certain configuration of values is particualrly useful to the user, it can be saved as a user-defined plasma so that it can be reused another time.

The user can quickly switch between entering numbers in SI or in cgs units. The toggle in the menu will switch all quantities automatically. There is a separate switch for temperature between units of Kelvin and electron Volt. The user may also switch the units if each quantity individually using the little drop-down menu behind each field.

A powerful option in the menu is the ability to export to and import from PDF. All the quantity values and their definition are brought together in reader-friendly two-page PDF document which can be shared with others. Others may then import the same PDF into the tool from their computer and make further calculations using those settings. An example of the PDF output is given here:


The Output Panel

The output panel, displayed in yellow, contains a series of tabs for the various output. Clicking on the tabs will allow you to navigate between them. Again each output quantity is displayed in a three-part structure. First a help button that links to the definition of the quantity. Second, the calculated value. Third, the units as the little drop-down menu (to switch between SI and cgs).

An important tab is the help indicated by the question mark. When clicking on this, a second set of tabs is displayed that follow the original set. Each tab contains the definitions of all the quantities displayed in the corresponding output tab.