The OPAL Discussion Forum

["frederic.le.pimpec" <frederic.le.pimpec AT psi.ch>]

Hi Chuan,

The simulation is queuing since 11 am this morning.
In the .data file
QBUNCH          0.1     # Bunch charge [pC]

before hand it was 200.
After QB will certainly deal with the number of QBUNCH .

So now I am expecting to see variation in the FE over 900 steps, 900 deg 
of RF S band phase.

bests
Frederic        

wangchuan02513 wrote:
> Hi, Frederic,
> Yes you can try Npart = 50 but no less, which as far as I know it's OK. But 
> the unit of QB is C not pC, so QB=1e-13 will not scare people:-)
> Enjoy!
> Best regards
> Chuan
>
>
>
>
>
> At 2011-09-02 16:41:17,"frederic.le.pimpec" <frederic.le.pimpec AT psi.ch> wrote:
> > Dear Chuan,
> >
> > OK I understand about the emission time. I indeed looked at this 1e-14 s 
> > and i was wondering what it was since i specified 1e-12, which becomes 
> > correct after a while.
> >
> > So Can I set Npart to 50 ?
> > This is small enough, and i don't care about the normal bunch. I am 
> > solely interested in how the dark current appears and get multiplied.
> > I can also set the bunch to 0.1pC in the data or tmpl file. I never 
> > remember.
> > Qinitial = Qi= 4e-14 [C] = QB(0.1)/Npart(54)
> > It should be OK with the simulation ? no cluster crashing ?
> >
> > bests
> > Frederic
> >
> > wangchuan02513 wrote:
> > > Dear, Frederic, Sorry for the late reply. Basically,  Qinitial = Qi=
> > > 0.002e-12 [C] = QB/Npart, where, QB [C] and Npart are defined in your .in
> > > file. Currently, Npart can not be set to zero, there are two reasons
> > > (at least these two are good enough:-??
> > >
> > >
> > > One is OPAL need to know the charge, particle type, etc before run FE
> > > model, so I adopted the old way to initialize the initial electron
> > > particle bunch for tracking ( Although I've provided another way to
> > > initialize particle bunch for cyclotron cavity multipacting
> > > simulation which do not involve initial electron bunch). Please don't
> > > set Npart to zero in FE simulation, this may crash the cluster.
> > >
> > >
> > > Second is we can use the initial bunch as a time/position reference
> > > during visualization for the dark current particles. In your case, I
> > > think you can simply subtract the number of initial bunch
> > > (Npart=5000), if the initial bunch will not hit the surface of the
> > > cavity, then you can get the number of dark current particles in each
> > > time step. Best regards Chuan
> > >
> > >
> > >
> > >
> > >
> > > At 2011-08-31 17:41:33,"frederic.le.pimpec"
> > > <frederic.le.pimpec AT psi.ch> wrote:
> > > > Dear Chuan,
> > > >
> > > > The png file which was sent yesterday shows : top plot, the total
> > > > number of particles at each time step and bottom plot the
> > > > difference between 2 systematic input from the PartStatistics.dat 
> > > > after extracting in the oxxx file for example step 666 OPAL {0}> *
> > > > NP= 31665 Qtot= 4.19804 [nC]  Qi= 4e-14 [C] This matches the number
> > > > in PartStatistics.datat the same step.
> > > >
> > > > The png file sent Partcl_Stat02.png, shows the number of emitted 
> > > > particle at every step extracted from the 0xxx file. This is very 
> > > > similar to what i sent yesterday from the PartStatistics.dat
> > > >
> > > > So the Qinitial (Qi= 4e-14 [C]) is set by default in the .in file ?
> > > >  this is in the data file or in the tmpl file ? I did not find it
> > > > in the .in file
> > > >
> > > > OK for the Npart. In fact since i have no initial bunch then i
> > > > should not care Npart should be set to zero ? I only care about
> > > > electrons emitted above threshold !
> > > >
> > > > About FN and the unsymmetrical surface mesh. I perfectly agree with
> > > > you "this unsymmetry should be small as the mesh is usually fine."
> > > >
> > > > Bests Frederic
> > > >
> > > > wangchuan02513 wrote:
> > > > > Hi, Frederic, First, could you find the PartStatistics.dat file
> > > > > in: your_simulation_directory/data/ ? Please have a quick look at
> > > > > the last column of the PartStatistics.dat which contains the
> > > > > number of physical particles in each time step, to see if the
> > > > > number of physical particles is the same with the simulation
> > > > > particle number data extracted from the .0xxx files.
> > > > >
> > > > > Then please also send me the input file, i.e., the .in file you
> > > > > use as well as the PartStatistics.dat file and .0xxx files
> > > > > generated by the OPAL output. So I can better understand the
> > > > > result you got.
> > > > >
> > > > > And, the Npart you defined in the .in file is the particle number
> > > > > of primary bunch, which only matters to the initial charge of
> > > > > each simulation particles in FE based simulation. As the time
> > > > > step goes by, there will be more more paritcles emitted by the FE
> > > > > model.
> > > > >
> > > > > The Qreal I mentioned in the previous email can be different for 
> > > > > every field emitted particles, because each field emitted
> > > > > particle, namely particle i, which have charge Qreal_i, may
> > > > > represent many more particles which have the same charge Qinitial
> > > > > as the charge of particles in initial bunch (like the initial
> > > > > bunch you have defined in beam1in your .in file).
> > > > >
> > > > > As the Fowler-Nordheim formular only compute the current density,
> > > > > so we have to multiply the triangle area as well as the time step
> > > > > size to get the emitted charge per time step. So the unsymmetry
> > > > > of the surface mesh (the triangle area) could cause the
> > > > > unsymmetry of the emitted particle number. But this unsymmetry
> > > > > should be small as the mesh is usually fine.
> > > > >
> > > > > Best regards Chuan
> > > > >
> > > > >
> > > > >
> > > > > At 2011-08-30 22:19:09,"frederic.le.pimpec" 
> > > > > <frederic.le.pimpec AT psi.ch> wrote:
> > > > > > Hi Chuan,
> > > > > >
> > > > > > so if you see attach what gives (extracted) the .0xxx files it
> > > > > > is emitting always at the beginning the same number of
> > > > > > particles. My RF phase change every ps in S band so 1 deg
> > > > > > phase. The particle emission should look like what is going on
> > > > > > between 600 and 700. which is already after a full period.
> > > > > >
> > > > > > when below threshold I should indeed have 0 emission particles.
> > > > > >  This is correct.
> > > > > >
> > > > > > Hence my question about the injection phase of the RF. It seems
> > > > > >  that for the 1st (360 steps) period I do not emit properly.
> > > > > >
> > > > > > Also in my ctf3...data file I have defined NPART      	5000 	# 
> > > > > > Number of simulation particles
> > > > > >
> > > > > > at the end I endup with more than 50 000 !
> > > > > >
> > > > > > in the .in file beam1: BEAM, PARTICLE=ELECTRON, pc=P0,
> > > > > > NPART=5000, BFREQ=BFREQ, BCURRENT=BCURRENT, CHARGE=-1;
> > > > > >
> > > > > > and what is Qreal = Qinitial*Nn/M
> > > > > >
> > > > > > at t=0 Qinitial=0, at t=t0 is my Q initial the  Q at =t0-1step
> > > > > > ? bounded to 1 otherwise Q =0
> > > > > >
> > > > > > I understand that M is the maximum number allowed per triangle.
> > > > > > How do you check that an iris in a structure when the field is
> > > > > > above threshold emitt the particles ? And all triangles mapping
> > > > > > the edge of the iris should emit homogeneously. They all should
> > > > > > emit the same way because I have a field cylindrical symmetric
> > > > > > around the Z axis of the machine !
> > > > > >
> > > > > >
> > > > > > So I am a bit lost ! like my particles.
> > > > > >
> > > > > > bests and thanks Frederic
> > > > > >
> > > > > >
> > > > > >
> > > > > > wangchuan02513 wrote:
> > > > > > > Hi, Frederic, So the particle number you use in the .oxxx
> > > > > > > file is the number of simulation particles, which may have
> > > > > > > different charge for each particle and is not the number of
> > > > > > > physical particles which you might be interested in. Please
> > > > > > > try PartStatistics.dat in YOUR_SIMULATION_DIRECTORY/data/ or 
> > > > > > > YOUR_SIMULATION_DIRECTORY/vtk/ (if you use older version of
> > > > > > > OPAL) and the last column gives the correct number of
> > > > > > > physical pariticles. Best regards Chuan
> > > > > > >
> > > > > > >
> > > > > > > At 2011-08-30 19:43:42,"Andreas Adelmann" 
> > > > > > > <andreas.adelmann AT psi.ch> wrote:
> > > > > > >
> > > > > > >
> > > > > > > On 30.08.2011, at 12:50, wangchuan02513 wrote:
> > > > > > >
> > > > > > >
> > > > > > > Hi, Frederic First I'm happy someone other than Andreas and 
> > > > > > > myself are interested in FE model in OPAL:-)
> > > > > > >
> > > > > > > First I have a question about the  .oxxx file, because as far
> > > > > > > as I know, I didn't write any .oxxx file during the FE based 
> > > > > > > simulation. Do you add this new feature in OPAL? If so,
> > > > > > > please give me more information about the .oxxx file.
> > > > > > >
> > > > > > >
> > > > > > > The .oxxx file is the std-out which appears in the output
> > > > > > > file written by SGE.
> > > > > > >
> > > > > > >
> > > > > > > Andreas
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > W.r.t you question, I would first introduce what the FE model
> > > > > > > in OPAL exactly do, which may help you to find out what the
> > > > > > > problem is. In the FE model in OPAL, 1. we traverse all the
> > > > > > > surface triangles in each time step, read and compute the
> > > > > > > Efields normal to the triangles, compare the Efields with a
> > > > > > > threshold defined by user in input file. 2. If
> > > > > > > Ffield<threshold, skip following algorithms and see the next
> > > > > > > triangle. 3. If Ffield>=threshold, compute the emission
> > > > > > > current density J according to Fowler-Nordheim formular. Then
> > > > > > > compute the nominal emitted particle number Nn. As the field
> > > > > > > emission process is a quantum process which may generate so
> > > > > > > many particles that beyond the memory limit of a cluster, so
> > > > > > > we scale the real emission particle number Nr with a larger
> > > > > > > charge Qreal = Qinitial*Nn/M, if Nn>M, where M is the allowed
> > > > > > > maximum number of emitted particles per triangle per time
> > > > > > > step. And in this case Nr=M. So probably, first you can try
> > > > > > > to set the threshold=0, which will make OPAL go through the
> > > > > > > full algorithms of FE model, then you should use tot 
> > > > > > > charge/Qinitial instead of the number of simulation particle 
> > > > > > > number in each time step. Hopefully these can help you, if
> > > > > > > not, please let me know. Best regards Chuan
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > At 2011-08-29 23:59:36,"frederic.le.pimpec" 
> > > > > > > <frederic.le.pimpec AT psi.ch> wrote:
> > > > > > > > Dear Chuan,
> > > > > > > >
> > > > > > > > I am wondering about the particle emission depending of the
> > > > > > > > RF phase of the accelerating structure, case of an RF gun,
> > > > > > > > 2 and a 1/2 cell, S band, meaning 1ps=1deg of rf phase.
> > > > > > > > Pure Field emission (FE)
> > > > > > > >
> > > > > > > > I have set in the ini file, 1000 steps. 1 ps = 1 step for
> > > > > > > > every ps.
> > > > > > > >
> > > > > > > >
> > > > > > > > The .oxxx file give the number of particle emitted per
> > > > > > > > step. let say for at least the first 25 steps, the emission
> > > > > > > > is constant and correspond to 27 particles. From the Field 
> > > > > > > > emission model and the RF phase , the number should either 
> > > > > > > > increase or decrease over 25 deg of RF phase.
> > > > > > > >
> > > > > > > > Sometimes during the emission the number of particle
> > > > > > > > emitted is identical to 22 and then jump at 400, then it
> > > > > > > > decreases.
> > > > > > > >
> > > > > > > > So I am not really understanding the behaviour of the
> > > > > > > > emission !
> > --
> > ---------------------------
> > Dr Frederic Le Pimpec
> > Paul Scherrer Institut
> > WBBA 315
> > 5232 Villigen
> > Switzerland
> > http://fel.web.psi.ch/
> > Tel : +41 56 310 5130
> > FAX : +41 56 310 4488

--
---------------------------
Dr Frederic Le Pimpec
Paul Scherrer Institut
WBBA 315
5232 Villigen
Switzerland
http://fel.web.psi.ch/
Tel : +41 56 310 5130
FAX : +41 56 310 4488