Usage: vmcw <command file>
The numerical experiment is done according with the command file. Each
line of the file containes a command for controlling the solver,
modifying 3He parameters etc. Comments are started with # symbol,
empty lines are ignored. Command file name without extention is used as a prefix
for some default output files.
-
start-- (Re)start the solver using a uniform mesh with number of points specified bynptscommand. If solver was running, use its data as initial conditions. -
stop-- Stop the solver, save its data as initial conditions. -
exit-- Stop the solver and exit. -
save state <file>-- Save solver state to a file. Only the solver state is saved, not experimental conditions (magnetic fields, 3He parameters, etc.). If solver is not running, then do nothing and print a warning message. -
load_state <file>-- Load solver state from a file. It does not matter was a solver running previously or not. -
wait <time, s>-- Do calculations for some time period. -
average <duration> <units=s> <npts=20>-- Average functions over some time and restart solver using the average value as initial conditions. Duration can be specified using different units:s(secnds),ms(milliseconds),us(microseconds),per_rf(period of RF pumping, 1/f0),per_hpd(period of low-frequency HPD oscillations, depends on f0, fB, HR0, uses RF field in the cell center if it is non-uniform). -
reset_time-- Reset time to 0. This command is useful when the time is much larger then time step and the calculation fails withT + DT = Terror. -
acc <value>-- Change solver accuracy. If solver is not running, the value will be used after it starts. Accuracy can be changed for the running solver. Default value for accuracy is 2^-20. -
acc2 <value>-- Same, but use log2 value (10 for accuracy 2^-10). -
mindt <value>-- Change min. time step (seconds). It can be changes at any time, but real change happenes when the new solver is started. It's recommended not to change default value (1e-10). -
npts <number>-- Change number of points. It is used when a new solver is started. It is also used for setting non-uniform initial conditions. -
tstep <value>-- Set time step. Can be changed during calculation. -
cell_len <value, cm>-- Change cell length. Do not change while the solver is running. -
adaptive_mesh [<N>] [<density>]-- Set a non-uniform mesh using solution from a running solver, restart the solver using the new mesh.<N>- number of points in the mesh (default - use old value).<density>- Non-uniform mesh step:cell_len/(N-1) / (1+<density>*RMS(U')). 0 means that mesh is uniform, 1 means that mesh is twice mere dense if RMS of function derivatives is 1.
bcond_type_l <value>,bcond_type_r <value>,bcond_type <value>-- set boundary condition type on left/right/both sides. BC types:- default - open BC
- 2 - closed cell, no spin flow through walls
- 3 - NPD wall, constant functions on the boundary
Following commands change default boundary condition and have an effect only when the solver is starded next time.
-
set_icond_uniform [<nz value>=1]-- set uniform i.c. with nz=-1 or nz=+1. -
set_icond_npd_simple [<nz value>=1]-- same -
set_icond_hpd_simple [<ny value>=1]-- set simple HPD initial condition: th = acos(-0.25), m=(ny*sin(th),0,cos(th)), n = (0, ny, 0). -
set_icond_hpd [<ny value>=1]-- set HPD initial condition with ny=-1 or ny=+1. This function uses 3He parameters, cell size and field profile to calculate HPD state. Use it after all parameters are set. State with ny=+1 is stable, ny=-1 is unstable. -
set_icond_npd [<ny value>=1]-- set NPD initial condition with ny=-1 or ny=+1. This function uses 3He parameters, cell size and field profile to calculate HPD state. Use it after all parameters are set. State with ny=+1 is stable, ny=-1 is unstable. This initial condition could be bad near resonance because spin diffusion is not taken into account and sharp resonance peak appeares. -
set_icond_nsol <width>-- set i.c witn a simple n-soliton. Width >0 does not work yet -
set_icond_tsol <width>-- set i.c witn a simple t-soliton -
deform <type> [<par>]-- Update initial condition from current function values, make some modification, and apply it to the solver. Types:deform none- no modifications;deform half_turn- rotate alpha_n, alpha_m by pi.deform rotation <N>- add constant gradient to alpha_n, alpha_m to have N full turns on the cell length.deform 2pi_soliton <w>- add a 2-pi soliton in alpha_n, alpha_m in the middle of the cell, with width<w>.deform th_soliton <w>- add a theta soliton in the middle of the cell, with width<w>.deform th_soliton1 <w>- th-soliton type 1 with sharp theta changedeform th_soliton2 <w>- th-soliton type 2 with sharp theta changedeform th_soliton1a <w>- th-soliton type 1 with artificial theta change (works only with BC=3)deform th_soliton2a <w>- th-soliton type 2 with artificial theta change (works only with BC=3)
After the deformation the solver uses same parameters as before, pnm_writer is not restarted.
-
write_profile [<file>] [<N>]-- Write function profiles to the file. Meaning of columns depends onNPDEsetting. ForNPDE=7it isx, mx,my,mz, nx,ny,nz, th, mx',my'...If filename is not set or set to '-' then a default filename<prefix>.prof<n>.datis used. IfNis not set or0, then use solver's mesh. IfN>2, build a uniform mesh withNpoints. If solver is not running then only prints a warning. -
write_mesh [<file>]-- Write coordinate breakpoints x(i). Default filename is<prefix>.mesh<n>.dat. -
magn_start [<file>]-- Start recording components of total magnetization (what you see in usual NMR experiment) to a file. If recording is already started then close old file and start new one. Default filename is<prefix>.magn<n>.dat. -
magn_stop-- Stop writing magnetization file. -
pnm_start [<file>]-- Start writing a pnm-file with vectors n and M orientation. If solver is not started do nothing and print a warning message. Default filename is<prefix>.pic.pnm. A few pnm writers can be opened. Pnm writers are stopped either then the solver is stopped or thenpnm_stopcommand is executed. -
pnm_legend [<file>]-- Start drawing a legend in the pnm file. If the pnm writer for this file is not running only prints a warning. -
pnm_hline [<file>]-- Draw a horizontal line in the pnm file. If the pnm writer for this file is not running only prints a warning. -
pnm_stop [<file>]-- Stop the pnm writer. If the pnm writer for this file is not running only prints a warning.
-
set_freq <value, Hz>-- Set NMR frequency. -
set_field <value, G>-- Set uniform field, in Gauss from larmor. -
step_field <value, G>-- Uniform field step [G]. -
set_field_grad <value, G/cm>-- Set field gradient. -
set_field_quad <value, G/cm^2>-- Set field quadratic term. -
sweep_field <destination, G> <rate, G/s>-- Sweep uniform field: destination [G from Larmor], rate [G/s] -
set_field_hz <value, Hz>-- Set uniform field in frequency shift units [Hz from NMR freq]. -
step_field_hz <value, Hz>-- Uniform field step [Hz]. -
sweep_field_hz <destination, Hz> <rate, Hz/s>-- Sweep uniform field: destination [Hz from NMR frequency], rate [Hz/s]. -
set_field_cm <value, cm>-- Set uniform field in Larmor position units [cm]. Gradient term is used to convert field to cm. Quadratic term is not used. Lower Larmor positon means higher field. If the gradient term is zero do nothing and print a warning message. -
step_field_cm <value, cm>-- Uniform field step [cm]. -
sweep_field_cm <destination, cm> <rate, cm/s>-- Sweep uniform field. -
set_rf_field <value, G>-- Set RF field. -
step_rf_field <value, G>-- Step RF field. -
sweep_rf_field <destination, G> <rate, G/s>-- Sweep RF field.
-
set_t1 <value, s>-- Set relaxation time t_1 [s], or 0 for no relaxation -
sweep_t1 <value, s> <rate, s/s>-- Sweep relaxation time t_1 [s] -
set_tf <value, s>-- Set Leggett-Takagi relaxation time tau_f [s], or 0 for no relaxation -
sweep_tf <value, s> <rate, s/s>-- Sweep Leggett-Takagi relaxation time tau_f [s] -
set_diff <value, cm^2/s>-- Set spin diffusion [cm^2/s] -
sweep_diff <value, cm^2/s> <rate, (cm^2/s)/s>-- Sweep spin diffusion [cm^2/s] -
set_cpar <value, cm/s>-- Set spin-wave velocity c_parallel [cm/s] -
sweep_cpar <value, cm/s> <rate, (cm/s)/s>-- Sweep spin-wave velocity c_parallel [cm/s] -
set_leggett_freq <value, Hz>-- Set Leggett frequency [Hz] -
sweep_leggett_freq <value, Hz> <rate, Hz/s>-- Sweep Leggett frequency [Hz] -
set_ttc_press <T/Tc> <pressure, bar>-- Set He3 parameters for a given temperature and pressure (Leggett frequency, spin-wave velocity, spin diffusion, Leggett-takagi relaxation). Program should be built withhe3libsupport. -
pin <k> <w>-- set pinning profile: minimum of Leggett frequency in the center with width xiD*w. May be useful for stabilizing theta-solitons. 0 (defailt) - no pinning, 1 - full pinning.wB = wB*(1- k*exp(-(x/xiD/w)^2)).