Q: I understand Landau damping, but I don't know anything about computers, what do I do?

Saving Potential Data (mode amplitude vs. time) for Post-Processing

The Landau Damping run requires time-history data, in this case, the time-history of the potential turns out to be the cleanest data to analyze, so the following document will (hopefully) give a step-by-step instruction to produce hard copies of the potential time history.

To start the user-friendly shell, type:


Choose (1) to start the 1-D electrostatic simulation. Use the following input parameters:

NPX = 40000
NPXB = 0
T0= 0.0
TEND= 300.0
DT= 0.10000
NTP= 1
NDP= 0

To get a copy of the input file,

After you have modified the parameters, you can begin running the program by typing:


after you finished entering the input parameters, then the shell will compile the program with the new parameters.

The shell will then ask you what graphic package you want to use for the simulation, since you are only in the potential history and are not interested in the instaneous events (or snapshots) in the plasma, you can run the simulation without graphics, so choose (8).

OK, now the computer asks:

Enter ok if it is ok to reuse all default diagnostic files? ,



At this point, you will get a few error messages from the code (which are harmless, by the way), and the message:

program executing

(and after a few minutes)

program done

Do you wish to run any post-processors?

p: Potential diagnostic
c: Debye cloud diagnostic
m: Main simulation program
n: Main simulation with forced recompilation

Enter the label before the colon or quit to terminate

Now, choose the potential post-processor by typing:


The computer would then prompt:

Enter name for potential file, ok for default, or quit

Because we didn't change the name of the potential file when we made the run, we should just type ok Now, in order to make hard-copies of the mode amplitude vs. time data ("mode history"), you will need to choose 5, this will make a file called gmeta that can be viewed or printed after the run is finished.

Now the computer asks:

* * * hit return or enter key to continue * * *

So hit (ENTER) , now, the parameters for the post-processor will appear on the screen. You need to change nothing to look at the damping, so just type run. Now you are done!! Type quit as many times as you need until the prompt:

alpha (51) %

appears, then log-out. In your PICL account, you need to fetch the gmeta file from OAC so you can print it with the laser printer. To transfer file, use ftp (file transfer protocol). To launch ftp, type:

ftp cluster.oac

(type user name and password to log in)

ftp> binary
ftp> get gmeta
ftp> quit

Now, you should have the gmeta file in your PICL account, to view it, type:

ctrans -d X11 gmeta

To print it out, type:

ctrans -d ps.mono gmeta

Fig: ln |correlation| vs. time for mode 11

Plasma Theory Homepage
Copyright © 1995 UCLA.

All rights reserved.
Frank S. Tsung 5/15/95