problems on WATCH, HISTOGRAM, and bunched_beam

[jcytsai]

Dear Michael,

I am a beginner in elegant, so far I found something strange and not sure if it's bug or not. Let me list them as follows: (I am using 25.0.2)

1. when using an accelerator element "WATCH" to record particles' parameters, I found "dt" and "t" are actually with the same values. I thought "dt" is a relative coordinate to bunch centroid's; however "t" is global coordinate. I was wondering if "dt" should be modified or is there anything I misunderstand? I have tried to create a new parameter (say, dtt) defined as the difference of "dt" and "t", and find "dtt" always shows zero.

2. For another element "HISTOGRAM", two of the column "tFrequency" and "dtFrequency" look showing weird results. For instance, when I use total of 1e5 particles for simulation, I get 5e11 dtFrequency in the vertical axis. However, the remaining columns look working normally.

3. For an elegant command "bunched_beam", when I tried to modify the beam distribution and its cutoff conditions by using "distribution_type" and "distribution_cutoff", I first simply copy the default values from manual,

distribution_cutoff[3] = {2,2,2},
distribution_type[3] = {"gaussian","gaussian","gaussian"},

then I found it fails to work.
However, when I look for an elegant example file, it reads

distribution_type[0] = 3*"gaussian",
distribution_cutoff[0] = 3*3,

this time it works! (why?)

4. When picking up one elegant example file to familiarize this simulation, I found the example "unchComp" lacks something (enumeration_file?) so that "phaseSweep" and "energySweep" cannot work. If possible, where can I get the missing files?

Since I am not really sure how the above questions should be categorized, I just put them here. I appreciate your time on my situation.
Thanks for your time and help.

Cheng-Ying

[michael_borland]

Cheng-Ying,

1. when using an accelerator element "WATCH" to record particles' parameters, I found "dt" and "t" are actually with the same values. I thought "dt" is a relative coordinate to bunch centroid's; however "t" is global coordinate. I was wondering if "dt" should be modified or is there anything I misunderstand? I have tried to create a new parameter (say, dtt) defined as the difference of "dt" and "t", and find "dtt" always shows zero.

dt is the time taken for the last pass through the system. For transport lines or linacs, it is the same as t. For storage rings, it will be different.

2. For another element "HISTOGRAM", two of the column "tFrequency" and "dtFrequency" look showing weird results. For instance, when I use total of 1e5 particles for simulation, I get 5e11 dtFrequency in the vertical axis. However, the remaining columns look working normally.

tFrequency and dtFrequency are in units of particles/sec. So if the bunch is short, you can get very high values. If you think there is a problem, please post a complete set of input files.

3. For an elegant command "bunched_beam", when I tried to modify the beam distribution and its cutoff conditions by using "distribution_type" and "distribution_cutoff", I first simply copy the default values from manual,

distribution_cutoff[3] = {2,2,2},
distribution_type[3] = {"gaussian","gaussian","gaussian"},

then I found it fails to work.
However, when I look for an elegant example file, it reads

distribution_type[0] = 3*"gaussian",
distribution_cutoff[0] = 3*3,

this time it works! (why?)

Because the manual shows the syntax in a form designed to show the data types and defaults. This is explained in
http://www.aps.anl.gov/Accelerator_Syst ... ode17.html
Also, it might help to study some of the examples

4. When picking up one elegant example file to familiarize this simulation, I found the example "unchComp" lacks something (enumeration_file?) so that "phaseSweep" and "energySweep" cannot work. If possible, where can I get the missing files?

The scripts dtSweep and phaseSweep create the enumeration files. If you are running the .ele files directly with elegant, you need to study the scripts first.

--Michael